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Thursday, Nov. 13, 2003


Sea slug

* Japanese name: Amakesaamefurashi
* Scientific name: Aplysia juliana
* Description: Sea slugs are marine mollusks, without gills or a shell -- just like most other mollusks. Often a dark olive-green color, at first glance a sea slug resembles nothing more than a stray piece of seaweed, but with a sucker on the end of its foot. Using the toe sucker to anchor itself, the sea slug can stretch out its head and neck. Sea slugs can also swim by flapping the flanges of their flattened bodies, like wings. They range in color from pale brown to black and often have whitish patches on the body; tropical species can be brightly colored. Sea slugs -- also called sea hares -- grow from 20-45 mm long.
* Where to find them: FAround the coast, in algal tidal pools. Sea slugs may be found by sorting through algae. Sometimes they can be found out of the water, sometimes partly buried in mud.
* Food: Sea slugs are herbivores and feed on green sea lettuce and algae. The color of the animal's body varies according to the type of algae it eats. They have vertical mouths.
* Special features: Many sea slugs produce a purple ink if they are disturbed. They have a gland (the opaline gland) that produces ink, like octopuses and squid. The species in the photo is one of the few that does not: It produces a milky white secretion.
Sea slugs are hermaphrodites, meaning they possess both male and female sets of genitalia. But they do not self-fertilize (they don't use their own sperm to fertilize their eggs). They mate ventrally ("face to face," rather than one mounting the other) and produce long strings of bright yellow eggs. Mating can occur any time of the year, except midwinter, and takes place in bouts, with individuals alternating the male role and donating sperm. The eggs are thought to contain chemicals derived from their plant food which are distasteful to potential predators. The eggs change color (to pink) as the larvae inside develops.

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