Continuing from the previous post …
It must have been a hermit crabs’ convention, as there were dozens and dozens. Perhaps they were there en masse to trade shells (they swap into larger shells as they grow) or mate, or just because there was a lot to eat. We saw close encounters, but perhaps that was because of the sheer numbers.
The rock pools always have a lot of dead shells, usually in poor condition as they’re smashed about a bit by the water against the rocks. Here’s a mudcreeper, the Hercules club (Pyrazus ebeninus). Mudcreepers graze on organic bits and pieces and algae in mud or sand.
This zebra volute was in pristine condition – unusual considering that volutes usually live in deep water and so this one would have had to travel a long way. According to Wilson’s A Handbook of Australian Seashells (which strangely doesn’t have this species in it, so I had to identify it using Jansen’s Seashells of South-East Australia), ‘Volutes are sand-dwelling predators, feeding on a variety of invertebrates including other molluscs. They have a long siphon and a large foot which is often colourfully patterned. … Australia is especially rich in species of this family, most of them endemic [found nowhere else]’.
Here’s the underside. Apparently they eat rocks, too.
There were very many live shells, many of which will provide shelter for hermit crabs in years to come. The neopolitan triton (Cymatium parthenopeum) has a coarse ‘hairy’ surface, called a periostracum, and the animal itself is the yellow-and-black-spots part. The stripe is part of the shell. Tritons are carnivorous, too, and eat other molluscs, sea squirts and sea urchins.
Cart-rut shells (Dicathais orbita) – more carnivores – were having a convention, too.
Here’s a live Spengler’s triton (Cabestana spengleri), one of which the hermit crab above was using as a home.
With all these carnivores, I bet the herbivores were shivering in their boots. I’ll talk about them next time.