Algae-eating snails and British writers

November 26, 2014

Divers had a break of sunshine over this monsoon weekend! Coupled with surprisingly good visibility despite the heavy rains we’ve been having, it was a perfect day for a dive! There were sightings of seahorses, pipefish, bamboo shark + a few of their egg cases tied around the reef, carpet eel-blennies, schooling Yellow soapfish (which was SO lovely), Yellowtail fusiliers, Yellowstripe scad and heaps of nudibranchs! There were also many dive boats out at the islands, keeping the reef busy all morning and afternoon. It’s great to see local city reefs getting lots of visitors! Hopefully, with more attention on our reefs, a better appreciation for Singapore’s natural marine heritage can be nurtured! Above: Anemone shrimp. Photography by Hantu Blog Reef Guide, Jeemee Goh.

The Saddleback anemonefish is typically found on sand flats and silty coastal reefs, or in harbours and lagoons. This is due to its relationship with the Haddon’s sea anemone, a sand-dwelling cnidarian upon which it is highly dependent on for protection. Because of its home in the sand, Female saddleback anemonefish have developed a novel way of creating suitable structures to deposit their eggs on. Adults drag suitable materials close to the base of the sea anemone, such as rocks, aluminum cans, sheets of plastic, coconut shells, and even old shoe soles. [1] The False clown anemonefish that can be found on coral reefs in Singapore, deposit their eggs on the reef structure at the base of its host anemone.

The dog conch, known endearingly by locals (who are about to dip it into sambal) as gongong, is a species of edible sea snail that bears no resemblance to a dog. Humans aren’t the only animals that look upon this snail with gastronomic fervour. Other spineless creatures like volutes and cone snails would be quick to make a meal out of this algae-eating conch. Crab-eating macaques are also keen to exploit this shelled nugget during the low tides, making life for this humble Strombus very challenging indeed. The dog conch has been subject to over harvesting throughout its range. Initiatives in the Thai province of Phuket attempt to increase depleted populations by reintroducing cultured animals into local seagrass beds. [2] Fishermen are also encouraged not to collect younger, smaller individuals that have not yet reproduced. We are lucky to have seen a few big ones crawling around our seabeds.

Thuridilla gracilis is a species of sea slug that lives in or near coral reefs and eats algae. They are often found in shallow water during the day and can grow up to 25mm!

The beginning of a new colony! This Dendrophylliid polyp is a kind of hard coral that does not contribute to the building of reefs. Unlike most coral on our reefs, they are not photosynthetic, and do not host zooxanthellae, the symbiotic algae that provides energy to the coral via photosynthesis. Instead, they are heterotrophic, and extend long tentacles at night to catch passing zooplankton. [3]

Chromodoris preciosa is beautiful and somewhat variable species found in the Indo-West Pacific, of which Singapore reefs are a part of. It favours both soft and hard substrates, grassbeds, algae, and silty seabeds. Perhaps the wide range of habitats in which it occurs has has something to do with the variety of colours in which it can be found. [4]

Divers saw some little cuttlefish and big cuttlefish this weekend, as well as a bunch of cuttlefish eggs deposited within the branches of an Acropora coral colony!

An awkward encounter during our dive was of this deflated giraffe balloon. Made of plastic, this balloon wasn’t about to disintegrate anytime soon. Had we not removed it, it would probably end up tangled in the coral as it weathered down into strips of plastic, potentially ending up in some poor sea turtle’s gut. It is not known how a balloon like that ended up out here on our reefs, but all over the world, the benign balloon is wrecking havoc in the environment. Check out BalloonsBlow.org to find out why we should try to avoid using balloons.

We were also very excited to share Singapore reefs with non-diver and Singapore-based British author Neil Humphreys who was eager to possibly be the only person on Hantu island. He had his moment for about an hour when campers, that were on the island when we arrived, packed up their tents and left. He was also unfazed by the murky water and was quick to plunge into our sandy lagoons to spot “blue fish”, “black fish with yellow stripes” and “yellow fish with two black stripes”, of which silhouettes he had sketched into his notepad. Even as our boat took a bit longer than usual to berth at the jetty due to a strong current, he bantered, “It’s all right, I can swim.” We look forward to hearing his thoughts about our humble islands in his writings!