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| Phylum Mollusca > Class Gastropoda > sea slugs > Subclass Opisthobranchia > Order Nudibranchia |
| Nudibranchs
Order Nudibranchia updated Oct 08
Where seen? Nudibranchs may be encountered on many of our shores. They are especially more likely to be seen near reefs. Also on coral rubble and rocky shores with sponges and other encrusting animals. Some are well camouflaged. The colourful ones may also be hard to spot as they blend in with their equally colourful prey. Many are quite small. What are nudibranchs? Nudibranchs belong to Phylum Mollusca.They are snails of the Class Gastropoda that lack shells as adults. Features: Nudibranchs have lost their shells as adults; 'Nudibranch' (pronounced 'noo-dee-brank' to rhyme with 'bank') means 'naked gills'. To protect themselves, some produce distasteful substances, toxins and even acids. They advertise this with bright warning colours. Others are camouflaged to match their surroundings. Those that eat colourful creatures such as sponges or corals, may themselves be colourful to match their prey. Being small and flat, they can easily hide in narrow places. Some nudibranchs breathe with a flower-like feathery external gill on their backs. Others lack this feathery gill and their gills are hidden between the body mantle and the foot. Many nudibranchs have two pairs of tentacles. One pair is near the mouth called oral tentacles, usually used to sense things by touch. The second pair is on top of the head and called rhinophores. Rhinophores are believed to 'smell' or detect chemicals in the hunt for prey and mates. Sometimes confused with flatworms, as well as other sea slugs that appear similar but belong to different orders. Here's more on how to tell nudibranchs from flatworms, and nudibranchs from other sea slugs. Stored stolen stingers: Aeolid nudibranchs have long, slender bodies with clusters or rows of elongated portions called cerata. These contain extensions of the digestive system and may also help the nudibranch breathe. Some nudibranchs, like Cerberilla nudibranch (Cerberilla sp.) protect themselves with the stingers of the sea anemones or corals that they eat. These stingers are passed, undischarged, to the cerata. The cerata of these nudibranchs have special sacs at their tips that contain the stinging cells of their prey. These stingers are undischarged and now protect the nudibranch.Here, the stingers remain 'live', ready to fire off and protect the nudibranch. What do they eat? Most nudibranchs are carnivores, each species usually specialises in a particular victim. Being small and slow, they feed on immobile creatures like barnacles, sponges, ascidians, hard corals, soft corals, sea anemones, zoanthids, peacock anemones, sea pens and eggs of other creatures including other nudibranch eggs. Fierce slugs: Like other molluscs, many nudibranch have a rough tongue (called a radula). Each species has specially adapted 'teeth' on the radula to deal with its prey. Those that eat sponges have many scythe-like teeth to scrape at the sponges. Some nudibranchs lack a radula and simply secrete digestive juices on their prey and suck up the soften soupy result. Others that feed on corals have well-developed jaws to hold onto the coral polyp while they gouge out the flesh with hooked teeth. Those that feed on bryozoans or ascidians have a pair of large teeth to cut open their prey. Nudibranch babies: Nudibranchs are simultaneous hermaphrodites, that is, each animal has both male and female reproductive organs at the same time. They practice internal fertilisation. So each nudibranch has a complex system of tubes to avoid self fertilisation, to introduce sperm while at the same time receiving sperm from a partner, and for laying eggs. They mate in pairs, lining up side-by-side, facing opposite directions in order to exchange sperm. Then they go their separate ways and each lays its egg mass, usually on the prey that they eat or on a hard surface nearby. In most, the eggs hatch into free-swimming larvae which have shells. Often, the larvae only undergoes metamorphosis and settles down when it is near its particular prey! The juveniles lose their shells and eventually turn into adult nudibranchs. Human uses: Nudibranchs don't do well in captivity and are thus not extensively collected for the aquarium trade. Moreover, some nudibranchs such as the phyllids produce toxins that may kill its tank mates. However, they are part of the attraction for divers and other visitors to natural habitats. Status and threats: None of our nudibranchs 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. |
 The Blue dragon nudibranch can be numerous at times. Beting Bronok , Jul 03  The Black-margined glossodoris is among the most commonly encountered nudibranch on our reefs. St. John's Island, May 05  The Bohol nudibranch is seasonally numerous. Sentosa, Jan 06  The Lined chromodoris nudibranch is another commonly seen nudibranch. Pulau Semakau, Jun 05  The Polka-dot nudibranch is very commonly seen. Pulau Semakau, Jul 08  Purple foot nudibranch laying egg ribbon. Chek Jawa, Jun 05 |
Pronounced 'noo-dee-brank', which means 'naked gills'.
| Order
Nudibranchia recorded for Singapore from Wee Y.C. and Peter K. L. Ng. 1994. A First Look at Biodiversity in Singapore. *from Bill Rudman's Sea Slug Forum species list **A Guide to Singapore Nudibranchs by Uma Sachidhanandam +added from our observation and documentation
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Links
- The
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. Go to the
General Topics section and browse the many interesting articles. Dr
Rudman helped identify our Chek Jawa nudibranchs and they are featured
on his site.
- The
Slug Site has fact sheets with gorgeous photos of various slugs
in the Branch of the Week
collection.
- A 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 Singapore nudibranchs.
- What
can nudibranchs tell us about climate change? on the wild shores
of singapore blog.
- Chou, L. M., 1998. A Guide to the Coral Reef Life of Singapore. Singapore Science Centre. 128 pages.
- Wee Y.C. and Peter K. L. Ng. 1994. A First Look at Biodiversity in Singapore. National Council on the Environment. 163pp.
- Debelius, 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
- Coleman, Neville. 2001. 1001 Nudibranchs: Catalogue of Indo-Pacific Sea Slugs. Neville Coleman’s Underwater Geographic Pty Ltd, Australia.144pp.
- Coleman, Neville, 1989. Nudibranchs of the South Pacific Vol 1. 64 pp.
- Edward E. Ruppert,
Richard S. Fox, Robert D. Barnes. 2004.Invertebrate
Zoology
- Pechenik, Jan
A., 2005. Biology
of the Invertebrates
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