Thalassinidean shrimp are among the most common burrowing organisms of marine intertidal and shallow subtidal environments, and may be common in deep-sea habitats as well. These organisms rely on self-constructed burrows for a wide variety of needs including shelter, reproduction, and feeding. Except for a larval phase which may be pelagic, most thalassinidean shrimp spend their entire life within the burrow. (Griffis and Suchanek 1991)
One well known thalassinidean on the Pacific coast of North America is the ghost shrimp Neotrypaea californiensis (formerly known as Callianassa californiensis), which burrows in muddy sand with enough clay and organic matter to make it reasonably cohesive and to provide material for lining its tunnels. This shrimp has a waxy pale pink and orange appearance. The largest individuals may reach 10 cm (excluding appendages). Burrows usually have a number of branches and turnaround chambers, with at least two openings to the surface, providing for some circulation of seawater through the tunnel system. Burrow openings are typically in the middle of little piles of sand or sand mixed with small pebbles. (Kozloff 1993)
This shrimp is abundant in mud flats of bays and estuaries on the west coast of North America. Individuals average from 5 to 8 cm in length and vary from a whitish yellow to orange-red. A striking feature is the possession of an exceedingly large cheliped, or claw, which may be on either the right or left side. This inequality in size of the chelipeds is largely a sexually dimorphic trait, for in the females the difference between left and right is much smaller. (MacGinitie 1934)
These shrimp, which are awkward and relatively helpless outside their burrows, are found most abundantly in tidal regions from zero to one foot in depth, and are restricted to bottoms of mixed sand and mud of a consistency that allows the construction of fairly permanent burrows. Neither very loose sand nor very soft mud will work. Individuals are occupied almost constantly in extending or adding new tunnels to their burrows, which often connect with those of other individuals (such connections, however, are continually being blocked off and tunneled around). The burrows are extensive and are being added to continually because the animals sift sandy mud to extract detritus, which constitute this shrimp's diet. The continual turning over of the soil and the aeration of the subsoil by the burrows of this shrimp are important to the entire community of mud-dwellers, and a variety of other species are commonly found on the bodies and in the burrows of these shrimp. (MacGinitie 1934) These associated animals include pea crabs; the scaleworm Hesperonoe complanata; a small clam, Cryptomya californica, whose siphons open into the burrow instead of to the surface; and the goby Clevelandia ios (although not restricted to Neotrypaea burrows, this small fish is regularly found in their vicinity). (Kozloff 1993) The presence of burrowing Neotrypaea californiensis may increase or decrease populations of other marine soft-sediment species (Posey 1986).
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