you learn only 3 things about them ...
are molluscs like snails. But most do not have an external
slugs such as nudibranchs are among the prettiest of marine
Slugs have very specialised diets and should not be kept
in home aquariums.
are slugs? Sea slugs belong to Phylum
Mollusca and Class Gastropoda. They
look like naked snails, i.e., without shells. Sea slugs are of course
those found in the sea. There are also slugs that live on land.
Sea slugs may be generally differentiated into two main groups. Members
of one group breathe with lungs. These include pulmonate sea slugs
such as the Onch slugs of the Family Onchidiidae.
Members of another group breathe with gills. These include the Opisthobranchs
or just plain sea slugs.
|Where seen? You will be almost
certain to see a sea slug on a visit to any of our shores. Onch slugs
can be found among the rocks near the high water mark, while other
slugs are found further down where it is almost always covered in
water. Some are burrowing and many are found on or near their food.
Some sea slugs are stunningly beautiful, among them, nudibranchs.
slugs range from large sea hares of 10cm to tiny nudibranchs 1cm or
less. Sea slugs generally lack large external shells. Some many have
external shells but cannot fully retract their bodies into these shells
like other 'regular' snails do. Other sea slugs may have internal
shells. Most sea slugs don't have any shells at all.
confused with flatworms.
Here's more on how to tell slugs
from flatworms, and how to tell apart
the different kinds of slugs.
they lack shells, slugs are not helpless. Some taste bad, others release
toxic or irritating substances. Yet others incorporate stingers of
sea anemones, hydroids and other cnidarians that they feed on and use these to protect themselves.
What do they eat? As
a group, sea slugs eat a wide variety of plants and animals. But each
species usually specialises in one kind of food.
Slug babies: Most slugs are simultaneous hermaphrodites, that is, each animal has both male
and female reproductive organs at the same time. The details of the way each reproduces is covered
in the fact sheets on them.
|Human (ab)uses: Slugs do poorly in
home aquariums because most have specialised diets (e.g., only specific
species of sponges). Most eventually die a slow death from starvation.
Some slugs may release highly toxic substances when stressed and may
thus kill everything in the tank.
Status and threats: None of our sea
slugs are listed among the endangered animals of Singapore. However,
like other creatures of the intertidal zone, they are affected by
human activities such as reclamation and pollution. Trampling by careless
visitors and over-collection can also have an impact on local populations.
Sea Slug Forum by Dr Bill Rudman: everything you could possibly
want to know about nudibranchs with fabulous photos and close-ups
of nudibranch body parts, larvae and more. And lots of links.
Slug Site has fact sheets with gorgeous photos of various
slugs in the Branch of the Week collection.
Guide to Singapore Nudibranchs by Uma Sachidhanandam: though
without any description of the nudibranchs, there are lots of
photos and locations where the species are found and a list of
- Tan Siong
Kiat and Henrietta P. M. Woo, 2010. Preliminary
Checklist of The Molluscs of Singapore (pdf), Raffles
Museum of Biodiversity Research, National University of Singapore.
- Wee Y.C.
and Peter K. L. Ng. 1994. A First Look at Biodiversity in Singapore.
National Council on the Environment. 163pp.
Helmut, 2001. Nudibranchs
and Sea Snails: Indo-Pacific Field Guide
IKAN-Unterwasserachiv, Frankfurt. 321 pp.
- Wells, Fred
E. and Clayton W. Bryce. 2000. Slugs
of Western Australia: A guide to the species from the Indian to
West Pacific Oceans.
Western Australian Museum. 184 pp.
Neville. 2001. 1001
Nudibranchs: Catalogue of Indo-Pacific Sea Slugs. Neville
Coleman's Underwater Geographic Pty Ltd, Australia.144pp.
Neville, 1989. Nudibranchs
of the South Pacific Vol 1. 64 pp.
- Edward E.
Ruppert, Richard S. Fox, Robert D. Barnes. 2004.Invertebrate
Brooks/Cole of Thomson Learning Inc., 7th Edition. pp. 963
Jan A., 2005. Biology
of the Invertebrates.
5th edition. McGraw-Hill Book Co., Singapore. 578 pp.