Distribution:- Aplysia is found in most parts of the world from the Arctis to the Antarctic. It is found in the West Indies,Florida, Coast, Asia(India).
Habit and Habitat: – Aplysia is a marine gastropod found crawling in sea weeds. It is able to change its color according to the color of seaweeds on which it lives .
General character :-
1) Aplysia is commonly known as sea horse.
2) The body is soft and lumpy with a thin flexible plate-like shell almost completely covered by a mantle. The shell is internal.
3) Head hears two pairs of tentacles, the anterior being larger and ear-like, while the posterior pair is olfactory rhinophores, each bearing on the eye at its base.
4) Mantle cavity opens on the right side with the ctenidium pointing backwards.
5) Visceral mass is raised into a prominent hump.
6) Anus lies at the posterior end .
7) Aplysia feeds mainly on the sea weeds.
Economic Importance :-
Seahorses possess one of the largest neurons in the animal kingdom, so they are extensively used in the field of neurobiology to study the function of specific nerves, especially memory and learning behaviors .
Distribution:- Doris is cosmopolitan in distribution. It is specially found in the water of New England.
Habit and Habitat – Doris is a sluggish, marine animal moving between weeds and feeding on the encrusting organisms.
1) Doris is commonly known as the sea lemon.
2) The body is bilaterally symmetrical, short, flat and oval with a convex dorsal surface.
3) Skin is tough and contains calcareous spicules of various types arranged symmetrically.
4) The color is purplish brown.
5) Head bears a pair of short retractile tentacles or rhinophores.
6) Mouth is situated on the ventral surface.
7) Foot is ventral with a broad sole for creeping.
8) Nervous system euthyneurons type.
Because the neurons of sea lemons are larger and easier to access than human neurons, researchers find sea lemons are useful in their study of nerve cells.Species are also used in aquariums.