15 December 2008

Strange snails, huge stars and other surprises

A very soft and silty shore with creatures seldom encountered. A small team braved the uncertain weather to check it out once more and saw yet more animals that we've not seen before!This amazing shore has patches of thick seagrasses. Especially near the mid-water mark.
With growths stretching out in some parts to below the low water mark.Seagrass species seen there include a clump of Tape seagrass (Enhalus acoroides).And lots of Spoon seagrass (Halophila ovalis) (left photo) and Needle seagrass (Halodule sp.) (right photo). Among the thick growths of seagrasses are dense crowds of creeper snails (Family Cerithiidae) and little Dubious nerites (Clithon oualaneinsis). I obsessed about those little snails in my post about my earlier trip there so I didn't look closely at them this time.
The seagrasses provide shelter for baby fishes such as these tiny Cresent perch (Terapon jarbua). Nearby, there were several fishermen. Conserving these habitats supports such recreational activities. Other creatures seen among the seagrasses were several bright red Thorny sea cucumbers (Colochirus quadrangularis), and an earnestly ploughing Tiger moon snail (Natica tigrina). This moon snail eats other snails and clams so it's in the middle of an eat-all-you-can buffet!Dotting the seagrass thickets were small and large carpet anemones, probably Haddon's carpet anemones (Stichodactyla haddoni) although the tiny ones could be Stichodactyla tapetum.In fact, carpet anemones were quite plentiful even elsewhere on the shores. And one had a pair of Five-spot anemone shrimps (Periclimenes brevicarpalis). At first, I only saw the big female with the large white spots and totally missed her more transparent mate. You can see him on the lower right corner of the photo with only a few white spots.Soft shores are great for sea anemones and large ones seen include the Plain sea anemone and one which had tucked its tentacles into its body column and look just like a ball.Today I saw a lot more peacock anemones (Order Ceriantharia) out on the soft silty shore. They are burrowing animals that create their own tube to hide in and are thus sometimes also called tube anemones.The black feathery Phoronid worm (Phylum Phoronida) is often seen with peacock anemones.Despite their common name, these animals are NOT sea anemones. They are distinguished from true sea anemone by their outer ring of longer tentacles, with an inner ring of shorter tentacles, and their tube. This pretty peacock anemone is unlike anything I've seen so far.

Surprisingly, on this soft silty shore we saw several small skinny sea fans.We didn't find any of Segal's spindle cowries (Cymbovula segaliana) that are sometimes seen on these sea fans. But there were things that looked like little red flatworms on this sea fan.

Embedded in the silt was this large Fan shell clam (Pinna sp.), showing only a thin wavy orange line where its shell opening is. These large clams provide rare hard surfaces on such soft shores so all kinds of other animals settle on them, such as this Thorny sea cucumber, as well as seaweeds. Some species of our Fan shell clams are listed as 'Vulnerable' on the Red List of threatened animals of Singapore.

There are quite a lot of snails on this shore and when they die, their shells are taken over by hermit crabs.These tiny hermit crabs crowd in large gatherings all over the shore.

This shore is full of snail surprises!Such as this large Lined moon snail (Natica lineata) which is seldom encountered elsewhere.
We saw this special snail again. I saw this on an earlier trip and it is possibly Bufonaria sp. (Family Bursidae).

A really special find was this large unknown snail.It refused to retract the mantle which covered most its shell. So we couldn't see the entire shell. It has a long siphon that it sticks out through a long narrow portion of its shell.It has a broad foot and we couldn't see an operculum. Chay Hoon and Kok Sheng got a photo of its eyes I think.
We saw a second one! This one was showing its entire foot. And further along, we saw a third one. We have no idea what kind of snail this might be.

Could these snails be Fig snails (Family Ficidae)?This is a drawing from The Gladys Archerd Shell Collection at Washington State University Tri-Cities Natural History Museum of a fig snail. Our fig snails didn't spread out the foot as in the diagram. According to the website, fig snails have a characteristic large triangular foot, and the two folds of the mantle almost entirely cover the thin shell. They lack an operculum.

We were so excited about this strange snail we almost entirely forgot about the special sand dollars that were thus far only seen on this shore.We saw lots and lots of these thick pentagonal Laganum sand dollars (Laganum depressum) that were seen during my last trip. Some were pink, others were darker. Also among these sand dollars were circular ones! Could they be the commonly seen Cake sand dollars (Arachnoides placenta) or something else entirely?

With Kok Sheng around, of course we wished for stars. Sea stars. The bigger the better.And our wishes came true! We saw this gianormous Eight-armed sea star (Luidia maculata)! We saw several more during the trip, for a total of four of these monsters.A little splash of sea water reveals the pretty patterns on this sea star. And we notice it's in an odd position. Kind of hunched so that the centre part of the body was raised. We're not sure what is going on because when we looked underneath, it wasn't holding onto or eating anything.A little further along, Chay Hoon found a second sea star also tucking one of its arms under itself.A closer look by Mei Lin at this second sea star reveals it might have nine arms! There was a little one regenerating. The underside is in the left photo, and upper side on the right photo. The nine-armed star also had orange stripes on its pointed tube feet. Here is a closer look (right photo) compared with the plain pointed tube feet of the first star (left photo).The upper side of the second star also had orange bits (right photo) compared to the plain grey and white of the first star (left photo). Hmmm. Kok Sheng has done a thorough post about this star and will no doubt keep us updated on what exactly is going on here.
Kok Sheng also found this tiny little star. It's too small for us to figure out what kind it might be.This soft shore had the usual sea cucumbers we've seen elsewhere, such as the bright red Thorny sea cucumbers (Colochirus quadrangularis) (left photo) and the Warty sea cucumber (Cercodemas anceps) (right photo).And strange unknown cukes such as these little white ones. There were two of them, one was above the surface, and another half buried.And this large greyish sea cucumber. I don't know what it might be.It was a really nice surprise to see several of these tiny red sea cucumbers. I saw a few individuals scattered among seaweeds. Kok Sheng said he saw a big gathering of these tiny red sea cucumbers in a soft part of the shore that I did not dare venture into. I've seen these before in both Tuas and Chek Jawa. There, they were seen in huge numbers, carpeting the rubble and other animals. The ones at Chek Jawa were sadly wiped out following the massive flooding of 2007 and we've not seen them again since.

Unfortunately, Chay Hoon didn't get her wish for slugs. But we were quite happy with a most exciting day out on a special shore. Despite visiting shores every low tide for nearly 7 years, we STILL see new stuff we've never seen before. And always, more questions than answers about our fascinating marine life.

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