Tuesday, July 31, 2007
Christopher at the Catalogue of Organisms explains how Daddy-Long-Legs (DLL) are not a useful name since people have historically applied different organisms to the name. So is a DLL a Harvestman, a Spider, or a Crane Fly? Head over to the Catalogue and decide for yourself!
Sunday, July 29, 2007
Everyone knows that all crabs moult. Its no secret. When you wear you skeleton on the outside, it makes it difficult to grow. So every now and then crabs and other arthropods, nematodes, tardigrades and some other "minor" phyla shed their exoskeleton or cuticle resorbing the Calcium held in it. They secrete a new one thats a little bigger, reusing the calcium from the old exoskeleton, letting them grow a little more from the inside out.
The exoskeleton of crabs is mad of a long-chain polymer called chitin (to the right, from here). It is a very sturdy material and an excellent defense against many would-be predators. But it might not be only for growth that crabs moult. There have been studies demonstrating the crabs have excess heavy metals in their exoskeleton and it has been hypothesized that moulting may be a mechanism to rid the crab of toxic metals. Metals could be bound and woven into the chitin matrix, then removed with the crab's moult.
An intriguing new study by Bergey & Weis, currently In Press at Marine Environmental Research, studied the distribution of Copper, Lead and Zinc during postmoult and intermoult times. These metals are common the Atlantic estuaries where Uca pugnax is found. Obviously all creatures need some amount of trace metals to various functions, such as enzyme cofactors, so why are some heavy metals harmful to crabs? In addition to sluggishness, lack of responsiveness, premature egg dropping, larval swimming behavior altered (Mercury), larval development and metabolic rate altered (Cadmium)
"Metals can cause disruption of molting, limb regeneration, alteration of blood glucose levels, color changes, and impairment of reproduction in crustaceans."-Bergey & Weis 2007Yikes, lets get rid of this stuff! Now, what could a crab do with excess metals to get it outside of its body? One way is to excrete it out with the rest of the waste products, such as ammonia, across epithelia or gill (see Weihrauch et al. 2004). But then this would be processed through several organ systems and tissues which could potentially be harmed by the metals. The other way is to hide it away somewhere until you can get rid of a large portion all at once. Sort of like bulk trash pickup day when the undergrads leave for the summer.
Bergey & Weis studied two populations of fiddler crabs from New Jersey. One population was inside a large, protected salt marsh (the clean population). The other population was collected outside of a sewage outfall (the polluted population):
"The site is surrounded by industrial sites, a sewage treatment plant, and a major highway. Oil spills... and possible leachate from landfills have also been a source of organic contaminants"-Bergey & Weis 2007I found the result to be very interesting. Namely, that the fiddler crabs from the polluted site eliminated 12% Copper, 76% Lead, and 22% Zinc. Notice the interesting skew? Thats a lot lead shed off with the moult! Conversely, fiddler crabs from the clean site eliminated a significantly lower amount compared to ones from the polluted site (3% Cu, 56% Pb, 8% Zn). So not only are fiddler crabs in lead-polluted sites mobilizing excess Lead to the exoskeleton, they are preferentially doing so potentially as a depurification mechanism. Quite brilliant actually, you already have the genetic machinery to moult. It seems to me an easy evolutionary story to visualize. Crabs that were able to make physiological adaptations to concentrate damaging heavy metals in their cuticles or exoskeletons had more viable offspring than those who sequestered the metals and let it damage their tissues and reproductive system. Of course zinc and copper are enzymatically important metals and are in much higher demand, which is why you don't see much elimination of these two elements. Lead has no known vital function in fiddler crabs
One thing I kept thinking about when reading this was whether thee crabs ate their moult. When a crustacean moults, it is unarmored and vulnerable. In fact, many crabs don't even bother feeding or coming out from a good hiding spot for a month while they wait for their new exoskeleton to harden (helped out by the recycled Calcium by the way). The benefit is lost if crabs eat their moult. This is common in insects as the moult may provide a first meal post-moult before retreating to safety. Some hermit crabs and the coconut crab are known to eat their moults. It would be interesting to see a comparative study of several different types of crab from polluted vs. clean sites that are known to either eat or not eat their moults. Also, perhaps doing a similar study on crabs that are known to ingest moults and have a treatment allowing them eat and treatment removing moults (not allowing them to eat) to see if metals are being reingested from the moult.
See also News@Nature.com story.
Friday, July 27, 2007
Solitary corals are a one-polyp stony coral and can often hide attached to reef-forming corals, where it mimics the reef-building coral. I have seen this many times on reefs of Lophelia pertusa, a deep-sea reef-forming coral. This song is about a solitary coral that is about to be overgrown, but can't do anything about it (any guesses why?) and can't seem to find any prey. Tragic. Some may recognize that this is sung to the tune of "Solitary Man" by Neil Diamond. Link to song is in the Spineless Songs sidebar. The singing was after drinking lots of homemade aquavit and I was too lazy to redo it. Should be entertaining enough for everyone!
The reef was mine 'til the time they overgrew me
Slow and long
Many polyps strong
Then food came along, made me strong, that's what I thought
then my prey,
Don't know that I will but until I can find me
Some prey that'll stay and won't play games behind me
I'll be in this world
A solitary coral
A solitary coral
I've had it to here - being where one is a small number
No strength in many
Can’t move any
I know it's been done havin' one polyp survive
Right or wrong
Weak or strong
Don't know that I will but until I can find me
Some prey that'll stay and won't play games behind me
I'll be in this world
A solitary coral
A solitary coral
Interested in doing a Masters of PhD? Not disillusioned enough yet? Always wanted to live in Louisiana?
Well have I got the job for you! Dr. Ray Bauer of the University of Louisiana at Lafayette is looking for graduate students interested in working on:
various aspects of the biology of decapod crustaceans (shrimps, crayfishes, crabs etc)Go to his website (linked in his name above) and check out his groups research! His current research interests are in hermaphroditic mating system in marine shrimp. If only I were 4 years younger... and had some strange desire to live in the South.
p.s.-Dr. Bauer, if you are reviewing my shrimp paper, please enthusiastically accept! And encourage the editors to waive page charges...
Somehow I came across this transcript of "Molluscs - Live TV Documentary", episode 32 of Monty Python's Flying Circus. Its hilarious (if you are into monty python humor). Of course a simple web search revealed it also existed on the almighty YouTube!
This is my favorite excerpt:
Zorba: The randiest of the gastropods is the limpet. This hot-blooded little beast with its tent-like shell is always on the job. Its extra-marital activities are something startling. Frankly I don't know how the female limpet finds the time to adhere to the rock-face. How am I doing?
Mrs Jalin: Disgusting.
Mr Jalin: But more interesting.
Mrs Jalin: Oh yes, tch, tch, tch.
Zorba: Another loose-living gastropod is the periwinkle. This shameless little libertine with its characteristic ventral locomotion ... is not the marrying kind: Anywhere anytime is its motto. Up with the shell and they're at it.
Mrs Jalin: How about the lamellibranchs?
Zorba: I'm coming to them ... the great scallop (holds one up) ... this tatty, scrofulous old rapist, is second in depravity only to the common clam. (holds up a clam) This latter is a fight whore, a harlot, a trollop, a cynical bed-hopping firm-breasted Rabelaisian bit of sea food that makes Fanny Hill look like a dead Pope... and finally among the lamellibranch bivalves, that most depraved of the whole sub-species - the whelk. The whelk is nothing but a homosexual of the worst kind. This gay boy of the gastropods, this queer crustacean, this mincing mollusc, this screaming, prancing, limp-wristed queen of the deep makes me sick.
***Editor's Note*** To alleviate any confusion in the last two sentences, whelk's are not lamellibranch bivalves. They are gastropods.
Wednesday, July 25, 2007
I started this series because I really wanted to know more about Chaetognaths. I've never run into them in any samples I've collected nor have any real experience with them at all. This may be the reason for my fascination of them. After reading the 2 articles from Current Biology that I discussed in Part 1 and Part 2, I have certainly developed an appreciation of their evolution and Chaetognaths as organisms in the general sense. That is where this post comes in. In that same issue of Current Biology, there is - believe it or not - a third article on Chaetognaths by Ball & Miller. This paper discusses more of the biology of chaetognaths and why they just plain cool creatures.
They are a relic of the Cambrian and fossils show that not much has changed in their body plan (above).
"The chaetognaths are an ancient lineage of invertebrates that shares some characteristics with just about every other major invertebrate phylum and has consequently puzzled taxonomists ever since its original description in 1769. Darwin described chaetognaths as ‘‘remarkable for the obscurity of their affinities’’ and they have puzzled a succession of eminent zoologists ever since. Though unfamiliar to most biologists, chaetognaths are typically the most abundant planktonic predators, sometimes accounting for more than 10% of zooplankton biomass and being outnumbered only by their major prey, the copepods."-Ball & Miller 2006Chaetognaths feed on copepods by sensing their vibrations and are able hunters in darkness (click here for a movie of a chaetognath hunting!). Some even have a neurotoxic venom. They are also simultaneous hermaphrodites. One species, Paraspadella gotoi, exhibits interesting mating behavior with ritualistic dance before exchanging sperm packet(below).
I found it interesting to that the authors note the nervous system bears a resemblance to nematodes, kinorhynchs and priapulids. In the phylogenetic papers of Matus et al. 2006 (see Part 1) and Marlétaz et al. 2006 (see Part 2), the authors take out priapulids from the analyses because they didn't like that Chaetognaths grouped with them within the Ecdysozoa. The Ecdysozoa clade is supposed to encompass the moulting animals. So Chaetognath's nervous system resembles members of the Ecdysozoa AND Chaetognaths have a cuticle. To my knowledge, animal cuticles get shed periodically? I'm not entirely certain if this is true or not, but something to think about. Another thing to about are a priori assumptions, such as we would like Chaetognaths to be closely allied to the Deuterostomes yet have some affinity with Protostomes too. You can't have your cake and eat it to. I think if you are going to use a consensus tree from dozens of genes, you should use the taxa possible/applicable to the analysis. In this case, all animal phyla because the question related to a phylum's position in the phylogeny of the animals.
I have no doubt from the molecular work shown to date that chaetognaths align with protostomes. But the protostomes are a HUGE group encompassing some of the most diverse animal taxa such as the arthropods, molluscs and annelids. Where they fit in that tree means alot evolutionarily. There are alot of biologists that outright reject the Ecdysozoa hypothesis for a variety of reasons. Libbie Hyman, who wrote book(s) on invertebrate diversity quite literally, recognized the affinities of the Chaetognaths to the protostomes:
‘‘It seems probable that the chaetognaths should be regarded as having diverged at an early stage from the primitive ancestor of the Bilateria.’’-Quoted in Ball & Miller 2006But Chaetognaths aren't the only unresolved taxon. There are many minor taxa which have few people working on them. Some taxa don't even have anyone in the U.S. as a specialist working on that group. Many of these taxa are in desperate need of study and revision and can potentially fill in alot of holes in animal phylogeny.
More Chaeognath Stuff:
Erik Thuesen's Chaetognath Webpage
PZ Myers Chaetognath Friday Blogging (2004)
Tuesday, July 24, 2007
Yeah thats right they get it on with any male gamete that passes there way. They just give a [rhymes with duck]. Boom chaka-laka-boom. These loose lizzies are all about increasing genetic diversity if you know what I mean. OH, I know you know what I mean!
In the latest Molecular Ecology, Johnson & Yund, explore the promiscuity of tunicates (In order to preserve my somewhat kid-friendly stature, I won't even go into all the possibilities with sea squirts...but feel to in comments!). I like this study, not only for its obvious connotations, but because multiple paternity in a sessile critter is an interesting and fundamental research question. Most studies of promiscuity have focused on mobile fauna. But the uncanny Urochordata, Botryllus schlosseri, has another interesting facet, it alternates between being male and female, with no storage of sperm. Yeah, thats right. Being male is just a phase that Tunicates go through. But this does pose an interesting question.
Johnson & Yund used molecular tools, such as DNA microsatellites and sperm haplotyping to investigate the role of multiple paternity using three measures
1) minimum number of fathers, based on paternal allele frequency from embryos
2) number of sperm haplotypes
3) effective paternity, based on the number of unique sperm haplotypes
They found 15 sperm haplotypes and no effect of local or population level density on any of their measures. I find this interesting because common sense would appear to dictate that colonies would show skewing of sperm haplotypes towards males that are closest to the embryos of the females being sampled as opposed to sperm that has had to travel farther, hence becoming more diluted or fertilizing females closer by, etc. But this doesn't appear to be the case with Botryllus schlosseri from Maine's Damariscotta River estuary.
So the punchline is that a whopping 90% of broods (using the most conservative measure) have multiple fathers. In fact, the smallest effective paternity from any one population was 2.4, meaning that there at least more than 2 fathers for each brood. Conversely, the highest effective paternity was 14.2! Woowee! Thats a virtual Orgychordata if you ask me! Keep in mind they only genotyped 15-20 embryos out of a potential pool of over 4,000 embryos in a broo.d. So I would definitely say that B. schlosseri is the slut of the invertebrates. But that is not without its potential advantages as outlined in the conclusion by the authors:
"Polyandry to increase genetic diversity is predicted to be favoured only (i) as a mechanism of inbreeding avoidance (ii) under situations of completely unpredictable environmental fluctuation (iii) when there is intense sibling competition, or (iv) when there is some cooperative or compensatory interaction among half-sibs."-Johnson & Yund 2007
Saturday, July 21, 2007
Porifera Double Whammy! Huge Silicate Spicules (or are you just happy to see me?) and the Evolution of Calcification!
Craig at Deep Sea News posted on new research about a deep sea sponge, Monorhaphis chuni (Hexactinellida), with the world's largest known biosilica structure! This is a silcate spicule that can grow up to 3 meters long. Thats at least a meter longer than you!
I don't really know how to construe to enormity of that structure. I could make it so you have to scroll down this post 3 meters, but that would just be annoying. The study Craig is referring to on DSN is by Müller et al., published in the most recent issue of Cell and Tissue Research. The authors carefully studied the formation of these giganto-spicules and helped along the way with silicatein-related proteins. Silica is not a common element in the ocean, though rare at the surface it increases in concentration as you go deeper by about 10-fold. The ability scavenge this rare element and incorporate into a biostructure in itself is a feat, and an expensive one at that! Now multiply that over time to about 3 meters...
This study is an excellent exercise in integrative biology. It merges biochemistry, histology, genetics, morphology and systematics. They determined there were different chemical layers to the spicules, including collagen and the silicateins (potentially a first for the Hexactinellida). The conclusion:
"Based on the data gathered here, we suggest that, in the Hexactinellida, the growth of the spicules is mediated by silicatein or by a silicatein-related protein, with the orientation of biosilica deposition being controlled by lectin and collagen."-Müller et al.Keeping with the theme of sponge skeletons, but moving away from silica-based to carbonate-based, a study by Jackson et al. in June 29 issue of Science used an approach called Paleogenomics to determine the role of precursor alpha-Carbonic Anhydrases (a-CA's) in calcareous skeleton formation. Paleogenomics uses modern techniques, such as gene and protein expression and phylogenetics, on extant organisms in combination with knowledge of their evolutionary history. a-CA's have evolved through several gene duplication events in the Metazoa for a variety of physiological purposes:
"The chemical reaction [CO2 + H2O ⇆ HCO3− + H+] functions in processing metabolic wastes, regulating pH, fixing carbon, and transporting ions across organic membranes. The metalloenzyme carbonic anhydrase is pivotal to these processes by catalyzing this reaction approximately 1 million fold."-Jackson et al.
A very important enzyme with a diverse set of functions cascading down throughout the Metazoa. The aim of this paper, in my opinion was to see what a-CA's looked like in the last common ancestor to the Metazoa (LCAM). Sponge genomes are great to look at for these types of questions because of their basal position on the animal tree of life. They determined the a-CA enzyme is used in biocalcification of the Demosponges. The sponges (and presumably biocalcification) radiated in the Cambrian Explosion, 520-540- million years ago. The LCAM most likely used the a-CA enzyme for a similar purpose. And in fact we see this feature, biocalcification, presevered in several protostome and deuterostome taxa. As with any well written Science paper, there is a succinct final paragraph concluding their results:
"From our data we infer that a core molecular toolkit capable of catalyzing the production of HCO3− (and ultimately CaCO3) was present in the first metazoans and included an a-CA. Subsequently, various metazoan lineages inherited this toolkit and have added to and elaborated upon its key elements to guide, enhance, and inhibit the deposition of CaCO3 in the spectacular variety of ways we see today."-Jackson et al.
Two well-written sponge papers with important evolutionary conclusions. What more could you ask for?
See also a perspective written by Taylor et al. on how sponges are providing insights into animal evolution.
Friday, July 20, 2007
In a fitting tribute, I've made minor revision to an old standard sang by the likes of Woody Guthrie, Bill Monroe and Doc Watson (modified as "Where is my Sailor Boy?"), Tim O'Brien and my personal favorite Dave Alvin, as dedication to Craig and Peter over at Deep Sea News.
Words are copied below and the song is in my Spineless Songs sidebar. I never claimed to sing well by the way! But then again thats why its called folk.
For another take on what the deep sea is saying click here.
What Does the Deep Sea Say? (DSN version)
Oh Captain tell me true
Do my sailors sail with you
No they do not sail with me
They sleep at the bottom of the sea
What does the deep sea say
What does the deep sea say
It moans and it groans, it splashes and it foams
and it rolls on it's weary way
Oh please tell me deep blue sea
Is Craig sleeping peacefully
The winds from the north are blowing icy cold,
Please keep him warm for me
If only Peter's dreamin soul
Some token of love could find
If only the waves would show me where he sleeps,
Then I’d leave this world behind
A beautiful rose one day
I placed on the crest of a wave
I said take it please and let the petals fall
Above their watery grave
The driftwood I watched in vain
My rose never came back again
So wave take a message to Deep Sea News,
Sayin I'll be here above
Thursday, July 19, 2007
Amphipods are truely amazing creatures. I've posted on them before and you can expect a plethora of posts in the future. Especially since I am trying to ID some right now from my quantitative community collections from the Lau Basin hydrothermal vents. So they are fresh in my mind.
I was very surprised today when I discovered that the ScienceDaily headline, Ice Age Survivors Found in Iceland, was not about neanderthals but amphipods! This news release highlights the research of Kristjánsson and Svavarsson in the endemic amphipods of Iceland's groundwater, recently published in American Naturalist. This study is fascinating for the reason that the island of Iceland has a known geologic beginning, around 30 million years ago, and known glacial period starting around 2.6 million years ago and ending 10,000-12,000 years ago. Most scientists believe that the glacial periods wiped out most of the terrestrial and freshwater fauna, except that may have found refugia near the edges of the glaciers. The author's discovery of 2 new species of groundwater amphipods
"strongly suggests that during the glaciations there was a subglacial refugium in Iceland where the amphipods could apparently survive in groundwater flowing through the porous lava bedrock that was constantly built up by active volcanoes throughout the glacial and interglacial periods."-Kristjánsson and Svavarsson 2007They cite three key pieces of evidence:
1) biogeographical patterns of the groundwater amphipods across the northern hemisphere
2) the new amphipods are the only freshwater ones in iceland with the new species pictured above being the representative of a new family, the Crymostygiidae, signaling the antiquity of amphipod in question
3) limited dispersal capability of subterranean amphipods, hence little colonization potential. They easily rule out dispersal via migrating birds since the closest place with closely related species is in southern England and Ireland.
Though they can't say exactly when and where a subglacial refugia formed, they offer this interesting point, where biology may aid in understanding geology:
"The presence of the Icelandic subterranean freshwater species belonging to an old group with a current distribution mainly in North America and the Eurasian continent indicates that the subterranean freshwaters of Iceland were in contact with continental groundwater at some time."-Kristjánsson and Svavarsson 2007This is yet another reason why amphipods are cool. Their subterranean relatives' patchy distribution, ability to survive harsh conditions, low dispersal capability, and the ability to adapt on a short time scale makes them model organisms to understand the evolutionary ecology of isolation by geological and ecological factors. I hope the next step that these authors take is to examine the population genetics and phylogeography of their new icelandic amphipods and compare them to counter parts in eastern US and western Europe. Perhaps this will bring to light the origin of their beasties.
I've been linked by the University of Michigan's Museum of Zoology for my highlight of the Museum's research on Tahitian Tree Snails. It is in the News and Events section. This is a big honor for me as I am a big fan of natural history museums. Maybe they will give me a job when I finish my degree! (wink wink nudge nudge) I always appreciate being linked to. Send me an email or leave a comment if you link to one of my articles. That way we can reciprocate the link love.
Go Wolverines! (nevermind that I'm nittany lion fan, only until I graduate though)
As a side note, I started using Statcounter to track my blog. The amount of hits I've been receiving has been astounding! Thank you to all who read and take interest in my little contribution to the internet. It is motivating to see people take such an interest in the other 95% of life!
A special thanks and shout out to Craig and Peter at Deep Sea News for helping me along the way. Some will know I had a short-lived column at DSN called From the Desk of Zelnio. This is basically an extension of that and applied to all the invertebrate phyla of which I hold so dear.
Wednesday, July 18, 2007
In Part 1 of What the Hell is a Chaetognath?! we learned from a study by Matus et al. using a consensus tree built from many genes, that Chaetognaths are the sister-taxon to the protostomes. This was surprising because Chaetognaths have long been classified as deuterostomes. The molecular evidence is strong even if I bitched about a few technicalities in their tree-building process (i.e. exluding taxa to get a different tree). A complimentary study in the same issue directly after the Matus et al. article, Marlétaz et al. consider the phylogeny of the Cheatognaths... again.
Before I delve into the science, a bit of an aside. Both studies analyzed genes of Chaetognaths and BLASTed the database of model organisms with those genes (mostly expressed sequence tags or ESTs). Each study had a different set of authors (no overlap) and came to the same conclusion, namely that Chaetognaths are protostomes. That is fine, I think the science is there. But 2 2-page articles saying the same thing with essentially the same method, published in the same issue of the same journal!? Come on people, lets work together. This is a little ridiculous. My guess it is political. One group found out what the other was doing. So as not to step on anyone's toes, they make an agreement to publish together, but separately. It happens. Just a little pointless is all.
Back to science! The Marlétaz et al. paper actually did find something new and interesting though. They sequences over 11,000 ESTs of a juvenile Chaetognath (Spadella cephaloptera, below).
In their prodding around they found the gene for Guanidinoacetate N-methyltransferase. This gene is interesting because it is only found in Deuterostomes and Cnidarians, lost in the Protostomes. It catalyzes the final step towards creatine synthesis, which is an important compound in energy metabolism of brain and muscle. Interesting that this is derived from a Cnidarian ancestor! Maybe that is why our brains look like jelly? Anyways, this provides striking evidence for their placement as a sister taxon to the Protostomes. Hence the common ancestor is not between a Protostome and Deuterostome, but between a Chaetognath and a deuterostome. May I remind you that Chaetognaths share the same embryological characteristics as Deuterostomes, plus now a Deuterostome-specific gene carried down from the Cnidarians and lost to the Protostomes. The phylogeny below (reprinted here without permission) from the Marlétaz et al. paper says it all.
Problems? Well, like I mentioned in Part 1, they exclude the Platyhelminthes from analysis. What is about flatworms that confuses Chaetognath phylogeny?? For one, they were the previous occupants of the sister-clade-to-Protostomes position, otherwise known as the position between Cnidarians and protostomes. Figure S2 from the online supplementary material shows the effects of this analysis. Fig. S2A includes Chaetognaths, while Fig S2B excludes them (reprinted without permission).
As you can see, Platyhelminthes was excluded based on the weak bootstrap support either way. This begs the question about why are Chaetognaths and Platyhelminthes so closely related (potentially), while only Chaetognaths retain deuterostomy characteristics? Thats another topic for another day though. I'll leave you with the concluding sentences:
"It confirms, on a genomic basis, that deuterostomy in an embryological sense is not a decisive character for the classification of animals. Some animals, like the chaetognaths, can be protostomes and yet show features of a deuterostome-like embryology. Nevertheless, the position of chaetognaths as a sistergroup of protostomes prompts us to propose that their development could be reminiscent of the bilaterian ancestor and testify that chaetognaths are a landmark phylum for addressing hypotheses about the origins of bilaterians."
Monday, July 16, 2007
Pascal over at Research at a Snail's Pace posted a spontaneous "8 things" blog meme. This post started as a comment that I just decided to post here, mostly for bragging rights. He states
"I have counted more than 10,000 individual snails and sieved through more than 200 kilograms of mud for my dissertation."
Impressive young Jedi. Let me just recall my last two field seasons of JUST THE GASTROPODS ONLY (don't even get me started on the freaking polychaetes!).
Lepetodrilus schrolli-37,666 (321.67g)
Olgasolarus tollmanni-7,114 (229.88g)
Symmetromphalus sp. nov.-713 (14.08g)
Bathyacmaea sp. nov.-424 (1.36g)
Pseudorimula marianae-72 (0.3g)
Desbruyeresia cancellata-70 (1.12g)
Shinkailepas sp. nov.-43 (0.98g)
Eosipho desbruyeresi-11 (273.57g)
Provanna buccinoides-6 (0.75g)
Bruciella globulus-6 (0.01g)
Phymorhynchus sp.-4 (0.16g)
Lurifax sp.-4 (<0.01g)
Pachydermia sculpta-3 (<0.01g)
Venstia tricarinata-3 (<0.01g)
Planordibella depressa-2 (<0.01g)
Leptogyra inflata-1 (0.01g)
Laeviphitus sp.-1 (<0.01g)
TOTAL # - 46,143 (843.89g)
These snails and limpets, by the way, are from the Lau Basin hydrothermal vent are are associated with communities of chemoautotrophic mussel (Bathymodiolus brevior) and snails (Alviniconcha hessleri and Ifremeria nautilei, counted >1000 each for sure). As an evolutionary biology/statistician friend of mine says, my dissertation is in bean-counting.
The purpose of all this counting and weighing though is to test hypotheses about how communities associated with chemoautotrophic foundation fauna are structured. At this particular locality there are three dense bed-forming foundation species. Each foundation species forms the structure or substrate for a community of associated organisms. I'm in the process of analyzing my data from 2 expeditions right now and will keep you posted on the progress and results!
Initial results look pretty interesting though, some clear cut patterns. For instance, one foundation species, A. hessleri, inhabits the hottest (up to 37 C perhaps) and most toxic (highest concentrations of sulfide) parts of the vents. Its community of associated fauna is very much different than the communities associated with I. nautilei and B. brevior. Both of the latter inhabit low temperature areas with lower concentrations of sulfide (the energy source for the endosymbiotic bacteria inside the chemoautotrophs). In fact their communities are very similar and overlap in Bray-Curtis nonmetric multidimensional scaling plots.
Sunday, July 15, 2007
In my ongoing mission to glorify everything invert, I've added new functionality to my blog. On the right side-bar you'll notice a my Spineless Songs sidebar. I will be writing songs about invertebrates and the sea, when the liquid inspiration lets me. Let me know if there are any problems.
I am happy to provide the mp3 or GarageBand file (for Mac users) to anyone who wants it. Are you a musical invert-o-phile too? Enjoying one of my tunes but think you could add a little pizazz to it with your instrument of choice? Got some great lyrics to serenade your beautiful beasties to but just need some music? Let's collaborate! Send me your digital file, lyrics that need music or ask for my digital file and let's jam (in the virtual sense of it).
My first song is called Big Dead Squid inspired by this Deep Sea News post of ...well... a big dead squid!
*By popular request here are the lyrics:
Big Dead Squid by Kevin zelnio
I sailed for 3 long years
Till the day I saw my fears
Realized on a stormy eve
On a stormy eve
I climbed the ladders down
Set my harpoon to the ground
Grabbed the oars to take my leave
the oars to take my leave
Was but 20 minutes out
No fin or water spout
Horizons clear there nothing but a breeze
There nothing but a breeze
But as the moment flashed
All I saw was but a splash
A whale as large ten oak trees
as large ten oak trees
My harpoon did I grab
I gave her one good jab
The blood the wailing that it did
the wailing that it did
For three more hours I held
The mother ship she sailed
To meet me before the sea forbid
before the sea forbid
The captain oh he grinned
But myself oh I sinned
We cut the blubber the skin we got rid
the skin we got rid
Rotten was the smell
My belly it felt like hell
As we gasped in awe at the big dead squid
in awe at the big dead squid
For common folk it be
A spectacle to see
For a sailor theres no worse a curse than a big dead squid
For a sailor theres no worse a curse than a big dead squid
Jeremy at the Voltage Gate explains why spiders aren't insects from a palaeobiological point of view. This is part three in a series of excellent posts on why spiders are not insects. Part one deals with morphology and physiology, while part two details the ancestry of spiders.
Part 4, the last in the series is posted. Jeremy explains the concept of homology and how the molecular phylogeny of spiders is congruent morphology and in fact the horseshoe crab is the closest relative, not in fact insects!
Thanks for the enlightening posts Jeremy!
Thursday, July 12, 2007
The vent shrimp, Rimicaris exoculata (literally the Rift-shrimp deprived of eyes), swarms hydrothermal chimneys, with temperatures reaching over 350C, en masse in the darkness of the deep sea. It has a certain peculiarity in that its eyes are completely absent yet there is a high concentration of the visual pigment, rhodopsin, in a dorsal "eyespot" beneath a transparent cuticle of the carapace. Other vent shrimp, such as individuals in all other alvinocarid genera, do retain the eye, though it tends to be reduced and fused together. The anatomy of this eye has been studied in detail and several authors have hypothesized that it can detect "black-body" radiation, or thermal radiation given off by the vents at around 350C.
Pelli & Chamberlain (1989) actually calculated out whether or not R. exoculata could see this black-body radiation given the concentration of rhodopsin it has and the radiation properties of 350C hydrothermal vents. Using alot of physics and math, their conclusion is:
"... 50pmol of rhodopsin present in the shrimp eye will yield approximately 1,600 thermal isomerizations per second. To detect the 350C vent, the shrimp would have to discriminate a signal-plus-noise isomerization rate of 1,800+1,600=3,400 per second from a noise-alone rate of 1,600 per second. A brief integration time of only 20ms would yield a decision variable with a signal-to-noise ratio of 6.4.[...] This would allow the shrimp to detect correctly the lethal hot water 99.9% of the time, and mistake ambient for hot water only 2% of the time."They determined that the shrimp's peak wavelength was around 500nm, pointing out that the luminance of the vent is just below the threshold for a dark-adapted human. Nuckley et al. 1996 concluded from their examination of retina:
"The structural changes observed in the retina of Rimicaris sp. might be expected in an animal that is adapting to a dim-light environment... and are consistent with the changes we have observed in other hydrothermal vent shrimp. In general, an animal's eye continues to enlarge as the environment becomes dimmer and dimmer until the "quit point" is reached where exploitation of light in the environment becomes impossible [...]. In animals that adapt to the darkness beyond the quit point, the eye shrinks or disappears altogether. The eyes of the [alvinocaridid] shrimp that live on the sides of black smoker chimneys at sites along the Mid-Atlantic Ridge have all enlarged... however the eye of the predator Alvinocaris markensis, which lives at the base of these chimneys, seems to be in the process of evolving past the quit point [...]."An interesting point also is that Rimicaris farms and harvests sulfide-loving bacteria under its carapace. The bacteria are where the temperatures are hot because that is where the sulfide is. Therefore the shrimp would have to make periodic excursions into hot water to get more bacteria to graze. This eyespot appears to be able to sense the thermal radiation given off by vents and use it to as a navigational cue utilizing the light-sensing organ in addition to using it to sense where it may get scorched! I have sense some alvinocaridids with what looks like burnt off tails. These alvinocaridids do not have the dorsal eyespot that Rimicaris does. Chamberlain 2000 reviewed vision in vent shrimp. He compared the image-forming eye of shallow water shrimp to the photodetection eye of vent shrimp, as well as comparing juvenile to adult vent shrimp. A very interesting insight was that
"the retinal structure of juvenile vent shrimp resembles much more closely that of the imaging eyes of surface-dwelling species... than it does the retinal structure of adult vent shrimp ...these data suggest that vent shrimp have evolved from ancestors that lived in a visual environment bright enough for them to use pattern vision, since the juveniles still show this kind of retinal structure,"
Tuesday, July 10, 2007
So I thought they were deuterostomes, but apparently thats only half the story. Lynn Margulis classified the arrow worms as deuterostomes in her 5-kingdom classfication (after Whittaker). Their deuterostome characteristics include radial, indeterminate cleavage, a posterior position of the blastopore (deuterostomy), enterocoelous coelom formation and a tripartite adult body plan with a post-anal tail. At least this is what I was taught "growing up". Three papers in Current Biology last year showed that while they have developmental patterns like deuterostomes, their genes tell another story!
The first paper by Matus et al. sampled several phyla and used several genes. A consensus tree built from 72 EST genes grouped them within the Lophotrochozoa. They also constructed a tree using tropomyosin genes showing Chaetognaths as the sister taxon to all the Lophotrochozoa. One thing that bugged about the EST tree is that when they included the Priapulida, Chaetognaths grouped with them in the Ecdysozoa. When the data were reanalyzed without the Priapulids, Chaetognaths grouped with the last common ancestor of the molluscs and annelids. The authors argued that
"The association with the Ecdysozoa, therefore, depends on a single taxon and is not likely to reflect a general affinity for the group."But shouldn't you use total evidence? Can you really justify leaving out data because it doesn't fit your expectations? In their supplementary material, they show three trees with three different conclusions.
The first tree:
"Bayesian tree based on the analysis of RY-coded concatenated SSU and LSU rRNA genes shows a relationship between the chaetognaths Paraspadella and Sagitta with priapulids."Conclusion: Chaetognaths are sister-taxon to Priapulids, well situated within the Ecdysozoa.
The second tree:
"Bayseian analysis of Ribosomal SSU and LSU data, excluding priapulids from RY re-coded data... The maximum likelihood bootstrap tree had very low support values."Conclusion: Chaetognaths are sister-taxon to Platyhelminthes, well situated within the Lophotrochozoa.
The third tree:
"Bayesian analysis of Ribosomal SSU and LSU data excluding long branch platyhelminths and priapulids from RY re-coded data."Conclusion: Chaetognaths are sister-taxon to all the Lophotrochozoa, occupying a basal position to the clade. This is the tree they liked and went with for their main article.
Don't get me wrong, I (think) I believe them. Their maximum likelihood studies show best support for Tree #3 and fits nicely into a story, keeps everything monophyletic and stable. For instance they state:
"To eliminate long branch attraction artefacts, we analyzed subsets of taxa to determine the effects of taxon sampling (Supplemental data). Regardless of the taxa removed (nematodes, platyhelminths or tardigrades) the chaetognaths remained as sister to annelids and molluscs with varying degrees of support in Bayesian analyses and as sister to the Ecdysozoa (arthropods, nematodes and tardigrades) with weak bootstrap support in likelihood analyses."I (think) I believe their analysis and conclusions, but I'm just concerned about the structure of the tree. There are profound evolutionary differences between protostomes and deuterostomes or between Lophotrochozoans and Ecdysozoans. One day I will go into detail about the different clades. Either way, the molecular data say Chaetognaths are definitely Protostomes. It disturbs me though that most of the developmental and morphological similarities to deuterostomes, as the authors stated, may be the result of convergent evoluton. In my opinion, convergent evolution tends to destabilize tree topology by decreasing parsimony. Sometimes I feel that when you invoke convergent evolution too much you might as well through up your hands and proclaim the magnificence of the grand designer...
Sunday, July 8, 2007
I've been double-tagged as it were, or tag-teamed perhaps, by RPM at Evolgen and Lim at Fresh Brainz. I am therefore obligated to post 8 random facts about myself. Being as there is no pre-existing list of facts about me to used a randomized method of selection, these will be haphazardly chosen from the recesses of my memory. The not-so-fresh part of my brainz. Here are the rules:
1. We have to post these rules before we give you the facts.
2. Players start with eight random facts/habits about themselves.
3. People who are tagged need to write their own blog about their eight things and post these rules.
4. At the end of your blog, you need to choose eight people to get tagged and list their names.
5. Don't forget to leave them a comment telling them they're tagged, and to read your blog.
And here are your haphazardly chosen facts about me .
1) I never ever thought of working in science at any point in my life prior to 2002. I actually never really considered college for that matter, My cumulative high school GPA was... lets just say less than 2. I had intended to work in music either on the rockstar end or the audio engineering end. I actually have a vocational degree in audio engineering and worked in a recording studio in the Bay Area (you can tell which end i was better suited for?). I hated the industry and decided to go community college.
2) Though born on the Illinois side of the QC, I spent 14 out of my 19 years in the QC on the Iowa side. I am proud to say I'm from Iowa, though I will die before I ever live there again. I have a shirt that says "Iowa: Our trees bend north because Minnesota sucks".
2) I went to 5 different colleges before getting my Bachelors of Science in Evolution and Ecology from University of California at Davis. Scott Community College in Iowa, Conservatory of Recording Arts and Sciences in Arizona, Vista Community College and Monterey Peninsula College in California and UC-Davis being the last.
3) In contrast for my love of the Invertebrates, I detest earwigs and will not hesitate to kill one. I kindly release everything else (except ants) outside my back door and co-exist with spiders in the hopes they eat the other bugs.
4) I worked the culinary industry for 5 years and still love to cook. I cook everyday for my beautiful swedish wife. She has cooked occasionally in the 8 years we've been together, but only rarely. In fact, she can hardly even eat out anymore because she says she prefers my cooking.
5) I was suspended from school in 9th grade for throwing a smoke bomb into a garbage can in the band room. I was also suspended in 8th grade for drinking an airplane bottle of scotch I stole from my parents liquor cabinet in the boys bathroom. Stupid 6th grader ratted us out...
6) I'm not alcoholic, just a drunk, but a happy one! I very much enjoy the evening (or lunch) drink or three. In fact, I am making aquavit as I write this.
7) Even though I am a marine biologist, I have never SCUBA dived. Just an intro-dive at the Great Barrier Reef. I want to but couldn't afford the gear and other expenses. I will get certified one day though. But I have been down to the bottom of the deep sea in 2 different submersibles, the Alvin and the Johnson Sea Link.
8) I'm covered in tattoos, though none are invertebrates I hope to change that in the future. I've been thinking about getting tattoos of all the species I describe.
Thanks for attention, it went on a little longer than I intended. As somewhat of an exhibitionist, I do like to talk about myself. The buck stops here as I don't think I know anyone who hasn't been tagged yet and I abhor chain letter/emails and wouldn't wish it upon anyone else. Consider me an evolutionary dead end if you will.
Saturday, July 7, 2007
Nothing makes me more happier than collecting specimens. I feel as if I am transported back to the Victorian era and am on a grand expedition to uncover the mysteries of the deep and testing for the first time the Azoic Theory of the ocean.
Except that my expedition only lasts for 4 weeks, not 4 years, and my purpose is not prove life exists in great depths at great extremes but to study the life we expect to find at these places. One such place is the East-Lau Spreading Center between Fiji and The Kingdom of Tonga. Here I am studying, as part of my graduate work, the ecology of communities structured by three habitat-forming molluscs, the mussel Bathymodiolus brevior and the snails Alviniconcha hessleri and Ifremeria nautilei. These 3 species are large chemoautotrophic species and serve as the foundation for an intricate network of associated fauna living within the aggregations of each mollusc. I am also describing, with other colleagues, species of anemone, zoanthid and shrimp from there (6, 1, 1 species, respectively).
The picture above shows my haul from the 2006 (sept.) field season. My last field, it is time for me to write it up, turn it in and move on. I don't know how many specimens I've collected in total. But from all the quantitative collections I've made in 2005 and 2006 I have found ~55 species associated with the 3 habitat-forming communities and have counted over 50,000 individuals of this associated fauna so far weighing in at over 1,948 grams. There are still a few taxonomic details I am working out with a Polynoid Polychaete genus, so I'll let you know the final word after that is sorted out along with the counts of the habitat-forming fauna.
As a final caveat, yes all the organisms I have identified are INVERTS! Surprised? I didn't think so... We did collect some zoarcid fish that I will analyze the gut contents of, but none were caught in my quantitative collections.
Friday, July 6, 2007
Its been a long time in the making and I know everyone is as excited as I am that the first cnidarian genome is finished! This is monumental for cnidarian biologists (such as I sometimes fancy myself to be). The lucky species is Nematostella vectensis (its pimp name is the starlet sea anemone),a small edwardsiid anemone quickly becoming a model organism in developmental biology and now comparative genomics.
Curiously, the genome more closely resembles that of the human and other vertebrate genomes rather than invertebrate genomes such as other model organisms Drosophila (Arthropoda) and C. elegans (Nematoda). Nicholas Putnam, lead author of the study elaborates that this surprising result may be due to greater retention of ancestral genes in the anemones and vertebrates, whereas these tend to be lost at higher rates in Drosophila and C. elegans.
"In many ways, the ancestral genome was not so different from ours; it was intron-rich and contained nearly complete toolkits for animal biochemistry and development,which can now be recognized as pan-eumetazoan, as well as the core gene set required to execute sophisticated neural and muscular function. The ancestor had blocks of linked genes that remain together in the modern human and anemone genomes—the oldest known conserved synteny outside of prokaryotic operons. Whereas fruit flies and soil nematodes have proven to be exquisite model systems for dissecting the genetic underpinnings of metazoan development and physiology, their genomes are relatively poor models for the ancestral eumetazoan genome, having lost introns, genes, and gene linkages."-Putnam et al. 2007. Science 317: 86-94
The sea anemone genome is estimated to contain about 18,000 genes compared to a reasonable estimate for the human genome at around 20,000 genes. These 18k genes are spread over 30 chromosomes. Furthermore, over 80% of the anemone's introns are in the same place as human's!
"Only 20 percent of the ancestral eumetazoan genes seem to be unique to animals. Fifteen percent of these seem to be completely novel - we can't identify any related gene in non-animals. The other five percent were formed through substantial modifications to very ancient genes."-Study co-author Daniel Rokhsar, quoted from UC-Berkeley press release on ScienceDaily.
“Nematostella’s genome may provide more insights into the functional evolution of human genes than many far more closely related animals.”-Co-author John Finnerty, quoted in Pennisi 2007. Science 317: 27, confirming the superiority of the sea anemone to all other phyla in being able to answer "What is the meaning life?" I know there is an anemone out there with 42 chromosomes...
This is fantastic start that will undoubtedly open many interesting doors in comparative genomics. I will be anxiously awaiting more results, especially in understanding the origin of novel genes to the animal kingdom relative to other eukaryotic kingdoms (Plantae and Fungi). The next genome? After reading the latest on Zooillogix today, it is definitely got to be Buddenbrockia plumatellae. It looks like a worm, but is completely symmetrical in cross-section. In the words of Peter Holland:
"It has no mouth, no gut, no brain and no nerve cord. It doesn’t have a left or right side or a top or bottom – we can’t even tell which end is the front!" (quoted from Physorg)
This study was also published in the latest issue of Science (way to bump up the invert presence!) and answers the paradox, what the $@#! is this thing?! Analysis of 50 genes (thats 31,092 amino acid alignments) confirms that 97% of the time Buddebrockia plumatellae clusters with medusozoan cnidarians. I would say that is pretty good evidence. The authors conclude that
"This active muscular worm increases the known diversity in cnidarian body plans and demonstrates that a muscular, wormlike form can evolve in the absence of overt bilateral symmetry."Is that funding bells I hear ringing? This is an amazing evolutionary question on how body form is controlled at the genetic level. Let me clear things up a bit. Buddebrockia is a myxozoan. A strange group of typically amoeboid parasites, with Buddenbrockia being a parasite of bryozoans (see picture below of new cnidarian exiting a bryozoan zooid). Myxozoans have strange nematocyst-looking cells called polar capsules. Some consider them reduced cnidarians, though with the discovery of the worm-like Buddenbrockia plumatellae and some Hox genes support a bilateria origin. Confused or just weirded out? Hopefully this study lays to rest of some of this conundrum. Although, it opens up infinitely more conundrums. Such as, if these are really cnidarians, albeit highly derived parasitic forms, how can there be this amazing diversity of body form from medusoid, polypoid, amoeboid, worm-like, and planular larvae all within a single phylum. I remind you that the Cnidaria are a well-supported clade!
Thursday, July 5, 2007
Deep Sea News reports on the recent finding of the OCTO-SQUID! This is potentially a new species of Mastigoteuthid squid that was sucked up by the deep-water pipelines of the Natural Energy Laboratory of Hawai'ian Authority (NELHA), a state-run agency. These pipelines suck in water from 3000 ft. and occasionally suck in the odd critter, such as the rattail and satellite medusae that accompanied the "octo-squid".
Of course NELHA would like to name the species if it is new. I say why not, it was their pipelines that discovered this rarity. From the sounds of Honolulu's Star Bulletin, NELHA may work in conjunction with the University of Hawai'i to assist in a more rigorous sampling effort, potentially offering up a treasure trove of deep-sea species that can be collected intact and alive. Pretty much my biggest wet dream. Yes, I will be applying for a job there when I finish my PhD. "Will describe species for meager salary and health benefits"
Wednesday, July 4, 2007
This video from Dr. Jared Leadbetter at Cal Tech, courtesy of the Journal of Visualized Experiments, described in fantastic detail the layers of symbiosis in termite hindguts. Well worth the view, watch as Jared dissects a termite hindgut then views the live bacterial and protozoal community. The quality of imagery is fantastic and Jared's enthusiastic narration is informative and captivating. Head over to the Journal of Visualized Experiments for many more visual wonders! This is how science is supposed to work in my opinion. The free transfer of knowledge from one individual to another. NO password barricades, journal subscription hinderance, just open access to the tremendous wealth of information accumulated by civilization.
Check out the traveling Circus of the Spineless this month over at Burning Silo. Find out all the spineless highlights of the blogosphere for June. So go and be "struck by the incredible beauty of so many of the images found in the posts". Learn about moths, butterflies and other insects as well as worms, slugs, spiders and snails!
Tuesday, July 3, 2007
In a new short, but sweet, paper by Lee et al. published in the most recent Current Biology, there is a "glimmer of hope" for montane tahitian tree snails (Mollusca, Gastropoda, Partulidae, Partula). They examined mitochondrial haplotype diversity of tree snail specimens locked away in museum drawers from 1970 and compared that to individuals from the wild and in
Partula spp. from Society Islands.
Photo Credit: Marc Agren
captivity from 2004-2005. What they found was that all the major clades from 1970 are present, though severaly winnowed, in modern day captive or wild populations. If that weren't enough to get the conservation junkies all jumping up and down in their pants. They were able to observe that 4 out of the 5 main Partula clades persisted on mountaintop refuges. This gives conservation efforts of Tahiti's tree snails a hot spot focal point to conserve the genetic diversity of the Partula lineage.
"Only a few years ago, it looked like the sole survivors from this radiation would be the captive populations that have been painstakingly established and maintained for decades in European and American zoos. Our new study indicates that it may be possible to maintain genetically representative remnant wild populations on Tahiti, the largest Society Island, although this will require proactive conservation measures."-Co-author Diarmaid Ó Foighil of The University of Michigan, Ann Arbor (quoted from EurekAlert!)
This also represents the extreme importance of museum collections to conservation. Without the proper vouchering and preservation techniques employed by quality museum staff, the 1970 snails wouldn't have been available to help answer this conundrum. The plight of the tree snail was not a light one. 61 species of Partulid tree snails were described from the Society Islands. Today, only 5 remain. The culprit? The carnivorous rosy wolf snail (Euglandina rosea, right), an invasive brought in to control another invasive snail from Africa (which was coincidentally brought over as a potential food source...).
"Natural history museum collections represent time-islands of biological diversity whose real value only becomes apparent in the long run. Jack Burch went to Tahiti in 1970 as a museum curator engaged in basic collection-oriented research. At the time, his Tahitian tree snail collections did not have any special conservation value. They are now priceless.”-Diarmaid Ó Foighil (quoted from EurekAlert!)
Go out and support your local natural history museum today! You never know what that $10 admission will do to help conserve species and understand our complex global ecosystem. Better yet, become a member, volunteer and participate in museum activities. Be a part of something great.
Monday, July 2, 2007
Those cnidocysts add a little tang to the tongue, kind of like a hot sauce! Jennifer at Shifting Baselines brings us the burger d'Jour, or the reality of the United States' current consumption of seafood. If things go as projected, all that will be left are Jellies! Is that so bad? The japanese eat them, but jellies aren't very nutritious. Leatherback sea turtles, a jelly specialist, need to consume a plethora of jellies to maintain expensive physiological processes like growth, metabolism and endothermy.
Another ENORMOUS problem is the use of the word jellyfish. Not only is this wrong on so many levels, it connotates a paraphyletic meaning if you will. Fish are the last common ancestors of the Amniotes (including humans), all of which contain backbones. Clearly this isn't the case. Morphological evidence suggests that jellies, though sometimes with a rigid hydrostatic system, rock-hard carbonate skeleton, sand grain and mucus tubes, or just plain ole incorporating sediment right into the body wall, do not contain contain a backbone, nor a notocord, nor pharyngeal gill slits, or dorsal-hollow nerve cord. Molecular and morphological evidence (see trees posted at Evolgen) also places the Jellies as a more or less basal group in the animal phylogeny and well separated from fish.
Next: Sea Stars aren't fish either! It is the stated mission of The Other 95% to strike from common usage the terms "Jellyfish" and "Starfish".
Sunday, July 1, 2007
The Amphipod homepage is your one stop-shop for any and all information relating to those wily Amphipoda! As you can see by this highly detailed graph from Australia's Museum Victoria, the Amphipoda have a wide vertical distribution from just under the snow line of pointy coastal mountains to pretty much everywhere there is water.
This website provides many links to labs and other online sources for everything Amphipoda. You can even read the temporally variable Amphipoda Newsletter and view many fantastic photographs of amphipods all brought to you courtesy of the Tromso Amphipod Team at the University of Tromso in Norway.
Well, at least the part of our brain that controls hormones anyways.
Researchers from the European Molecular Biology Laboratory [EMBL] now reveal that the hypothalamus and its hormones are not purely vertebrate inventions, but have their evolutionary roots in marine, worm-like ancestors.
In a press release on ScienceDaily, researchers in Germany found striking similarities in hormone-secreting nerve cells between the marine polychaete, Platynereis dumerilii (pictured above) and the Zebrafish, a model organism for developmental biology. These calls also have the dual purpose of containing sensory properties, such as photo- and chemo-sensory functions.
The similarities between the fingerprints of vasotocin and RF-amide-secreting cells in zebrafish and Platynereis are so big that they are difficult to explain by coincidence. Instead they indicate a common evolutionary origin of the cells.
"...vertebrate-type hormones were found in annelid worms and molluscs, indicating that these centres might be much older than expected." - Study coauthor, Detlev ArendtThe study's authors propose that cell types with dual sensory-neurosecretory properties were the starting point for the evolution of neurosecretory brain centers in Bilateria.
"Now we know that the brain is itself a sensory organ and has been so since very ancient times."-Kristin Tessmar-Raible, lead author of the study, published this week in the journal Cell.
In your face vert-o-centrics! I knew all along that worms were at the core of our brains. We all dream of them every night, just most of us deny our inner desire to evert our pharynx!