Thursday, August 04, 2011

Changi Beach on 31 July 2011

Last Sunday, I was back at Changi Beach to check out the intertidal life. Not sure if it's because of the hot weather over the previous few days, there were much fewer organisms compared to what we saw on our previous trips. The diversity was still quite good though.

There were several octopuses out and about today! This one appeared to have caught something and was holding it in its tentacles.

Have seen this many times at Changi, but still not sure exactly what it is.

The were a few clumps of Green Mussels (Perna viridis), sticking on to harder substrates.

Interestingly, we saw several pairs of moon snails, including the Tiger Moon Snails (Natica tigrina) above. Are they mating?

There were also a few pairs of Calf Moon Snails (Natica vitellus), and one lonely one shown above.

Here's a look at its underside.

Several crabs were spotted, but the most abundant one should be the Flower Crab (Portunus pelagicus).

Among the sea pens, a few commensal Porcelain Crabs (Porcellanella picta) were found.

The little Black Sea Urchins (Temnopleurus sp.) were not as abundant compared to my previous trip here last month, though I suspect they were probably in deeper water.

We only saw one Salmacis Sea Urchin (Salmacis sp.), and it was really well camouflaged!

There were also a few Sand Stars (Astropecten sp.).

We can usually see two different colorations among the Sand Stars. Not sure if they were of different species.

There were a few Biscuit Stars (Goniodiscaster scaber), but definitely not as abundant as our previous trips.

I only saw one Cake Sea Star (Anthenea aspera).

One of the main highlights for the other friends who came with me must be this Sea Apple (Pseudocolochirus axiologus). This poor animal was washed up onto higher shore when we saw it. We quickly put it into a pool of water, and were glad to see it moving a while later.

The Pink Thorny Sea Cucumbers (Colochirus quadrangularis) were still very abundant.

And once in a while, the Pink Warty Sea Cucumbers (Cercodemas anceps) are spotted.

This is one sea cucumber which we still have not managed to identify...

There appeared to be a lot more tube anemones than usual though.

And as usual, several of these sea anemones with red spots on its body column were found.

I was rather pleasantly surprised to see this dark red sea anemone, Bunodosoma goanensis, which was kindly identified by Dr Daphne during her recent trip here. Previously I have seen only seen it at Punggol.

While there were fewer things seen during this trip, Changi still had many nice surprises!

1 comment:

Pat said...

Have seen this many times at Changi, but still not sure exactly what it is.

I've been rather curious about this shellfish too. The one in your photo looks similar to most of the specimens labelled "Bean-shaped venus clams" at WildSingapore.

The distinctive zigzag/cris-cross lines & the wide "beans-shaped" shells suggest either Paphia undulata (Undulating Venus, Surf Clam, Short-Necked Clam, Carpet Shell, Hoi Lai), or Paphia textile (Textile Venus). I have also seen Sheng Siong Supermarket sometimes sell live specimens as "Undulating Venus Lala" -- structurally, they resemble the one in your photo.

Paphia undulata is differentiated from the smoother-shelled Paphia textile by its "undulating oblique grooves on medial part of the shell", "less elevated outline", "less inflated valves", as well as larger size at maturity.

So the specimen in your photo looks more like Paphia undulata. Do you have an photo showing the side/ elevation view ? Over at the WildSingapore webpage, the relatively-smooth & pale shell labelled as "Changi, May 05" appears to be the only Paphia textile shown there. What do you reckon ? Have you noticed more P. undulata or P. textile on local shores ?

Below are some photos &/or descriptions for comparison:-

[1] Marine Biodiversity Database of India: Paphia undulata, Paphia textile
[2] SeaLifeBase: Paphia undulata, Paphia textile
[3] Natural History Museum Rotterdam: Veneridae -- look for both species
[4] Molluscan Trip Photos -- look for Paphia undulata under Pattani Market
[5] Malacologist's Corner: Paphia undulata, Paphia textile
[6] Mediterreanean Science Commision: Paphia textile