Enteromorpha Life History
UPDATE: Enteromorpha: synonymous with the genus Ulva
See Linnaeus was right all along: Ulva and Enteromorpha are not distinct genera. in Eur. J. Phycol (August 2003) 38: 277-293.
Like many algae, Enteromorpha alternates between asexual
and sexual life stages. Both life stages are very similar morphologically.
However, the sporophyte has two sets of chromosomes, denoted as 2N,
while the gametophytes have only one set of chromosomes (1N).
As shown in the following diagram, through mitosis, gametes (sexually
reproductive cells) are produced by gametophytes, and then they join
together and grow into a sporophyte. The sporophyte then undergoes
meiosis, producing zoospores (asexual reproductive cells), and each
zoospore grows into a gametophyte. The gametophyte then produces more
gametes, and the cycle continues.
Enteromorpha is dioecious, meaning it has separate
sexes. In addition, Enteromorpha can be isogamous or anisogamous,
in other words, the male and female gametes can be the same size or
they can be different sizes. However, even thought the gametes are
sometimes different sizes, it is difficult to tell the male and female
gametophytes apart because they have similar morphologies, and neither
sex has specialized reproductive bodies. Both gametes and zoospores
are released from the tips of the fronds, and when fertile the tips
become colored orange-yellow in males and yellow-green in females.
Some lonely gametes looking for love.
The gametes are starting to find each other and clump
Any of the cells in a frond are capable of producing gametes. Gametes
have two flagellae, which enables them to swim. Spores, on the other
hand, have four flagellae. Gametes are unable to survive for long periods
after being released if they do not find another gamete or a place to
grow. Zoospores, however, are able to live for as long as eleven months
without growing if they are subjected to an adverse environment.