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Sea
hares are seasonally common on Chek Jawa. Like other gastropods, sea
hares have a shell, but this is thin and just under the skin.
Why are they called sea hares?
Sea hares probably got their name because they move rather quickly,
for a slug! With some imagination, the tentacles on their head do
resemble the ears of a hare. Also, they are herbivores, eating seaweed.
Sea hare parts: Sea hares breathe
through gills. These are enclosed in their mantle (body wall) which
has openings to pump water in and out. They have two pairs of tentacles.
The front pair is made up of rolled tubes containing chemical sensors.
Some have a smaller pair further back. Some have simple eyes at the
base of the second pair of tentacles. Some sea hares can swim by flapping
the sides of their bodies.
You are what you eat: Sea hares
eat seaweed and algae, rasping this off with their radula. They often
match their food, in colour and sometimes, texture as well!
Hare dye: Some sea hares produce
a purple dye when disturbed. The dye is believed to contain distasteful
chemicals. It clouds up the water and confuses and repels predators.
Others produce colourless but equally repulsive chemicals.
Hare today, gone tomorrow! Sea
hares do not live long as large, mature adults. They die soon after
they reproduce. They are hermaphrodites and sometimes form mating
chains, each one acting as female to the one in front of it and as
a male to the one behind. They lay eggs in strings or ribbons. There
is often a seasonal abundance of sea hares on Chek Jawa, with not
a hare in sight in between.
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Close-up of the head
Geographic sea hare
Syphonota geographica |
See
also ...
Nudibranchs are also gastropods that are not protected
by thick shells.
Molluscs in
general
Gastropods in general
Links
Sea Hares-Watch
out for Mating Chains by Fred Wells, Western Australian Museum on the
Beachcomber on the Western Fisheries Magazine: about the Black sea hare
(Aplysia gigantea).
Sea Slug Forum by
Dr Bill Rudman: all about sea hares, nudibranchs and other sea slugs; including
details on Bursatella
leachii and Syphonota
geographica.
Sea hares
by Fred Wells, Western Australian Museum on the Beachcomber Archives on
the Western Australia website: easy introduction to sea hares and mating
chains, with some photos.
Other references
- Barnes, Robert
D. & Ruppert, Edward E., 1996. Invertebrate Zoology. Harcourt
College Publishers, 6th Edition. pp. 1056, G-1-16, I-1-30.
- Morten, Brian
& John Morten, 1983. The Sea Shore Ecology of Hong Kong. Hong
Kong University Press. 350 pp.
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