Barnacles, limpets or gribbles?

The Leafless walked in from a walk by the beach to tell us about a log which had washed in. She said it was full of shells. I thought it might be barnacles. I finished my tea and walked out to look at the log.

It was a freshly broken branch of a tree, and it had been colonized by bivalves. Clearly these were not barnacles or limpets. Were they gribbles? I didn’t think they were. They could be piddocks; those are bivalves. But the piddock shells I got to see in a few days did not look like these. I wonder what these mysterious creatures are. Look at the movement of the shells on the extreme left in the 7th second of the video below: they look like real bivalves.

I wonder if anyone can help me figure out what they are.

Fish in a tide pool

On arrival at Neil Island we met a young auto driver called Suman. He turned out to be very articulate, and had a very pleasant way of explaining to us when we disagreed on anything: including fares. There were many pleasant auto drivers on the island, but of those we met he was the most articulate. Once we were at a loose end in Bharatpur beach, when we met him.sitapurrocks He asked where we wanted to go, and we said that we would go to whichever place he wanted to show us. He took us to Sitapur beach.

That was the first time we saw this beach, with its spectacular crescent of yellow sand, and the wonderful submerged layers of rocks. You can see the clarity of the water in the photo above. I think the rocks must have been heaved up in the 2004 earthquake. I loved the very eroded flat slabs of rock, some with holes bored by piddocks.

Rocks around Sitapur beach, Neil Island, Andaman

The tide was out, and we walked out over the bare rocks to peer into little tide pools. Some of them had tiny fish which would dart away as soon as they saw something looming above the water. Eventually I captured the featured photo by crouching low on a rock until the fish came to rest. Until I saw the photo, I hadn’t noticed the bubbles at the tips of the fronds of seaweed.

The beach was empty except for us and a French couple swimming in a deep pool among the rocks. We walked up to a distant rock fall and came back. Suman was waiting expectantly, and his face lit up when we answered his unasked question by saying this was a beautiful spot.

Bitten by a radioactive mollusc?

It’s not very often than I hear The Family yelp. When she did, I tore myself away from the ghost crab I was trying to photograph to check on her. She was holding a long conical shell and looking very white. As I rushed up to her I remembered a friend of ours who was working on poisonous cone snails. Was she holding one?

Fortunately, she was not. The creature in the photo you see above had been startled when The Family picked it up from the beach, looked out and used its pincers to explore its surroundings. That’s when I heard the sound from its surroundings. Once we realized that it was not poisonous, I took a few photos before putting it back. It was the second day of Christmas.

Ghost crab, Neil Island, Andaman

Meanwhile the ghost crab (photo above) would have disappeared. I saw it first as something scurrying over the white sand at the edge of my vision. I looked around and couldn’t see it. But then it moved again as I was looking at it. It didn’t like my camera, and kept scuttling away. Eventually, as it rested on a little stone, I managed to get a photo. Even in the photo it is hard to see it clearly. I’ve enhanced the contrast to make it visible. I’m sure I can see ten legs, but how many eyes does it have, and where?

When you look at the photo above, you notice the holes in the stone. What makes them? Jessica had some answers: in a much colder sea there are creatures called rock borers (duh), piddocks, and sponges.

Piece of a sea sponge, Neil Island, Andaman

I would not have believed this about sea sponges. But on the third day of Christmas my niece got for me a sea sponge on a rock. We admired it together. The branching filaments of the sponge allow it to sample the water that flows through it, and filter out food. I noticed that the rock on which it grew was full of holes. As for piddocks, I only saw these bivalves the next day.

Gribble holes in wood, Neil Island, Andaman

On the fourth day of Christmas, The Family and I admired this large piece of driftwood we had to cross. The beautiful surface has been created by living creatures. In the waters around the Andaman islands, the wood borers are mainly molluscs called shipworms (family Teredinidae) and crustaceans called gribbles. It turns out that there is an immense scientific literature on these, because of the harm they do to wooden structures. However, many of the papers are on the biology and physiology of these creatures. One of the few things I learnt was that shipworms and gribbles eat wood, but piddocks just make holes where they can sit safely. In the photo above you can see a few shells lodges snugly in holes in the wood; these are probably piddocks. Eventually I came across a post which takes you deeper into the world of wood eaters in the sea.

I think these were more interesting than partridges, turtle doves, French hens and calling birds. And no, The Family still hasn’t developed a mollusc sense.