Blog Log June 25, 2006
While the weather wasn't too pleasent this Sunday, with rains holding up till 10am, we continued our venture out to Hantu with a full boat of Xplore guides and guests. Because of the cooler surface temperature, getting into the water was alot more comfortable and warm, and some of the creatures we came across during our first dive included juvenile sweetlips and rubble pipefish, as well as shy crinoids.
On our second dive, there were other delicately coloured crinoids, also known as feather stars. Crinoids are among the most ancient and primitive of ocean invertebrates. They are Echinoderms, the same as seastars, brittle stars, sea urchins, and sea cucumbers.
This is the same animal but with its tentacles slightly unfurled this time. To feed, they extend their arms to catch bits of plankton or waste matter passing in the current. The number of arms a Crinoid has varies widely between species; some may have as many as 200, each up to almost 14 inches in length. Crinoids are distinguished from other echinoderms by the fact that their mouth is pointed upward, unlike their starfish cousins. There are nearly 550 species of comatulid crinoids worldwide.
This is not a new picture to the Blog. Photographed a few times before, I continue to find it entertaining seeing such a handful of tubeworms living so closely together. Until I found out that these feather duster worms live in groups, making them social! These worms make their tubes with calcium-based minerals, similar to our bones. The worms use their antennae (or radioles) to catch food and to breathe. Ocean currents push water through the radioles, which work like a net to trap tiny plants and animals called plankton that float in the water. The radioles also work like gills, exchanging carbon dioxide for oxygen in the water, allowing the worm to breathe.
We also found a new pair of shrimps in a Ritteri anemone (also known as Magnificent Anemone). While there's one that might look quite prominent to you, notice another hiding closer to the anemone's tentacles. She's gravid because you can clearly see her brood of green-coloured eggs, right through her transparent body, amazing!
And who could ever have enough of them? With a good number of anemones at Hantu, several anemone fish can be found at Hantu. We know at least 3 species that can be found here. The anemone, with its stinging tentacles, protects the fish from predators. Like all cnidarians it has nematocysts, that explode when touched, injecting poison in any aggressor or prey. The reaction is triggered by contact, and it is inhibited by substances in the mucus coat: two tentacles belonging to the same anemone can get in touch without attacking reciprocally.