How many creatures can live on a sea pen? On a sandy shore, a sea pen is probably like a luxurious apartment to many small animals that need shelter.
This particular sea pen that washed up on the shore was full of tiny Painted porcelain crabs (Porcellenella picta). I have never seen so many porcelain crabs in one sea pen! Usually, only a pair are found in a single sea pen.
bottlebrush brittlestar, and several tiny colourful brittle stars (Ophiactis savignyi).
Striped hermit crabs (Clibanarius infraspinatus). The hermit crab constantly produces an aerated stream of water and its messy feeding habits mean lots of left overs to snack on.
Slipper snails (Family Calyptraeidae). These hat-shaped snails are usually only found in shells occupied by hermit crabs. The smaller snail is male and is fastened on top of a larger female. On the upper side of the shell, there was a Jingle shell clam (Family Anomiidae) and small Drill snails (Family Muricidae) had laid their egg capsules!
Moon crabs (Family Matutidae) on the shore. This looked like a mating pair, a larger one wrestling with a much smaller one.
Flower crabs (Portunus pelagicus). I also saw some other kinds of Swimming crabs (Family Portunidae), one Reticulated moon crab (Matuta planipes) and one Ghost crab (Ocypode cerathophthalmus) buried in the sand.
sea pencils. I also saw one cerianthid.
swimming anemones (Boloceroides mcmurrichi) which were more plentiful.
Cake sand dollars (Arachnoides placenta). I saw two Sand stars (Astropecten sp.).
Ball sea cucumber (Phyllophorus sp.). Kok Sheng found a Smooth sea cucumber, and I saw a washed up Pink warty sea cucumber (Cercodemas anceps).
Penaeid shrimp (Family Penaeidae).
transparent shrimps with yellow 'elbows' (Palaemon sp.) in shallow pools on the higher shore. As well as many small Tidal hermit crabs (Diogenes sp.).
Blue fan worm (Family Sabellidae) that I usually only see on our northern shores.
goby (Family Gobiidae)!
Tongue sole (Family Cynoglossidae) slithering over the sand in the water. There were also several Whitings (Family Sillagenidae).
Button snails (Umbonium vestiarum), I couldn't find any live ones. I wonder why this sandy shore isn't as spectacular as the one at the Lost Coast that we visited recently? It's not even as nice as the sandy shore at the East Coast. Well, at least we checked up on it. We never know when it might suddenly become more alive!
See also Kok Sheng's blog post. He saw a lot more than I did!