 |
|
| sea slugs text index | photo index |
| Phylum Mollusca > Class Gastropoda > sea slugs |
| Onch
slugs Family Onchidiidae updated Feb 09
Where seen? Onch slugs are common on all our shores, on algae-covered rocks or other hard surfaces, or on mud in mangroves or mangrove tree roots. But they are often well hidden especially on a hot day, or well camouflaged even when moving about in the open. What are onch slugs? Onch slugs belong to Phylum Mollusca and are snails of the Class Gastropoda that lack shells. Onch slugs are NOT nudibranchs! Pulmonate sea slugs such as the Onch slugs of the Family Onchidiidae breathe air through simple lungs or modified gills. Other sea slugs breathe underwater with gills. Here's more on how to tell apart onch slugs from other sea slugs. Features: 1-6cm. Unlike most other snails, they don't have a shell as adults. Instead, they have tough skin to reduce water loss. But like most other snails, they have a broad foot and a pair of eyes on long stalks. Most snails have eyes at the base of tentacles. When disturbed, the eye stalks retract under the tough broad body. Onch slugs often blend perfectly with the rocks in both colour and texture! Bits of sand and sediments that get stuck on their skin adds to the camouflage. So please watch your step when you are walking on a rocky shore. These slugs belong to the same group as land snails. They have modified gills, a section of the mantle cavity modified as a lung to breath air. The opening to this cavity is at their rear ends. At high tide, they burrow into mud or sand, trapping an air bubble to breathe from. What do they eat? Onch slugs graze on algae and lichen on rocks at low tide, they are more commonly seen on cool mornings or evenings. Onch slug babies: Onch slugs are hermaphrodites, each slug having both male and female reproductive organs. Status and threats: One of our mangrove onch slugs (Peronina alta) is listed among the threatened animals of Singapore. Like other creatures of the intertidal zone, they are affected by human activities such as reclamation and pollution. Trampling by careless visitors can also have an impact on local populations. |
 Raffles Lighthouse, Jul 06  Leaving behind a grazed patch, and a trail of 'processed algae' Raffles Lighthouse, Jul 06  One pair of tentacles and mouth on the underside. Raffles Lighthouse, Jul 06 |
Onchs are very well camouflaged. Don't step on them!
 Underside. |
 |
 |
Onch slugs on Singapore shores
| Family
Onchidiidae recorded for Singapore from Wee Y.C. and Peter K. L. Ng. 1994. A First Look at Biodiversity in Singapore. *from Ng, Peter K. L. & N. Sivasothi, 1999. A Guide to the Mangroves of Singapore II (Animal Diversity) in red, listed among the threatened animals of Singapore from Davison, G.W. H. and P. K. L. Ng and Ho Hua Chew, 2008. The Singapore Red Data Book: Threatened plants and animals of Singapore.
|
Links
|
IKAN-Unterwasserachiv, Frankfurt. 321 pp.|
|