Holothuria leucospilota

My initial impression of sea cucumbers was that they are really boring and rather disgusting creatures. They look like huge bloated worms and most of the time doing nothing but just….hanging around. But then I got my hands on some echinoderm books and I started to develop a liking for them, more so after encountering several sea cucumber species during the course of my work.

Sea cucumbers have evolved to lie on one side with the mouth and anus on opposite ends of the body. Their skeletons have been reduced to microscopic ossicles which are important in identifying species. Sea cucumbers feed by means of filtering suspended food particles or organic laden sediments using their feeding tentacles. They thus play an important role in helping to turn over reef sediments.

Holothuria leucospilota is one species I’ve encountered numerous times. They are usually exposed at low tide and are conspicuous in rock crevices. They kind of look like the excrement of a giant marine creature.

H. leucospilota is one of the species that ejects sticky white threads called Cuvierian tubules from the anus as a defence strategy. The repugnant tubules are believed to repel or entangle would be predators.

Sea cucumbers may be soft bodied and appear docile but they are not to be underestimated!

Pictures taken at: Terumbu Bukom, July 2006; St John’s Island, December 2006 and Lazarus Island, December 2006.


References:

Colin, P. L. & C. Arneson, 1995. Tropical Pacific Invertebrates. A Field Guide to the Marine Invertebrates Occurring on Tropical Pacific Coral Reefs, Seagrass Beds and Mangroves, Coral Reef Press, U.S.A.

Lane, D. J. W. & D. Vandenspiegel, 2003. A Guide to Sea Stars and other Echinoderms of Singapore, Singapore Science Centre, Singapore.

Colugo (Malayan Flying Lemur)

I got to know Norman Lim when I volunteered for his Pangolin survey. He is a nice guy, scholarly and has tremendous passion for animals especially those poorly studied nocturnal creatures. He also has a sharp eye and is always spotting well camouflaged animals others would miss. His Honours Colugo project and recently published book open a window into the Colugo's secretive life.






There are only two species of Flying Lemur in the world. The Colugo (Cynocephalus variegatus) and the Philippine Flying Lemur (Cynocephalus volans). They are of course not related to Lemurs at all but belong to the order Dermoptera. The taxonomy of Flying Lemur has been of much debate. Recently, genetic studies suggest they maybe closely related to humans!

And of course Colugos are one of the few mammals that glide. I was lucky to witness the feat a couple of times and it was quite a sight as the animal spread its patagium and glided effortlessly onto a tree trunk metres away. During the day they’ll usually rest in a tree hole or roost by perching against a tree trunk. It takes a keen observer to spot them.

These individuals were seen at Bukit Timah Nature Reserve and near the Tree Top Walk.

There is an estimated population of about 1500 in our forests. They do not do well in captivity but ironically there is a small population of free ranging Colugos in the Zoo. It seems they can survive well in landscaped and fragmented habitats. Nonetheless, it is crucial for the relevant authorities to conserve its shrinking habitats and protect this native enigmatic animal.

Pictures taken at: A northern offshore island, November 2006; Bukit Timah Nature Reserve, September 2006 and Tree Top Walk, November 2006.

References:

Agoramoorthy, G., C. M. Sha & M. J. Hsu, 2006. ‘Population, diet and conservation of Malayan flying Lemurs in altered and fragmented habitats in Singapore’, Biodiversity and Conservation, vol. 15 (7), pp. 2177-2185.

Francis, C. M., 2001. A Photographic Guide to Mammals of South-east Asia, New Holland Publishers Ltd, United Kingdom.

Lim, N., 2007. Colugo. The Flying Lemur of South-east Asia, Draco Publishing & Distribution Pte Ltd and National University of Singapore, Singapore.

Mud Lobster

We were just about to leave the survey site when Weiling and Shufen squealed in delight. They have sighted a Mud Lobster out of its mound!! We followed the bright red lobster as it scrambled over the mud mounds and debris.

We were urging it on and wondering where it was heading when it stopped and started digging into the mud. As it dug with its huge claws, we were expecting it to go right in. But surprisingly, it did a reverse maneuver and went in abdomen first thus completing a perfect camouflage!

It was indeed very fortunate for us to witness this common but rarely seen mangrove keystone species. The tall mud mounds they create are the result of processing huge amount of mud to obtain the organic material the lobsters feed on. The mounds will eventually become a key habitat for several mangrove animals like tree-climbing crabs, other invertebrates and even certain species of mangrove snakes.

I did a search on ScienceDirect and a surprising paper from 1942 turned up. It was written by researchers in Singapore recommending the use of lime and water to kill mud lobsters!! Their aim was to control the proliferation of mud lobster mounds thus eradicating breeding sites of malaria mosquitoes. Boy, am I glad our researchers have moved on from this mindset.

There are two species of Mud Lobster in Singapore. What we saw is most probably a Thalassina anomala. But the taxonomy of Thalassina genus is difficult and needs to be revised.

Pictures and video taken at: Mangrove in western Singapore, January 2007.

References:

Holthuis, L. B., Marine Lobsters of the World.
http://ip30.eti.uva.nl/BIS/lobsters.php?selected=beschrijving&menuentry=soorten&id=12

Ng, P. K. L. & N. Sivasothi, 1999. A Guide to the Mangroves of Singapore II, Singapore Science Centre, Singapore.

Scharff, J. W. & M. W. F. Tweedie, 1942. ‘Malaria and the Mud Lobster’, Transactions of the Royal Society of Tropical Medicine and Hygiene, vol. 36 (1), pp. 41-44.