Marine Invertebrates of the Week: Hermit Crabs…and a Barnacle!

SEURAT'S HERMIT CRAB (Calcinus seurati)

Hermit crabs are related to crabs but the rear half of their bodies are soft bodies that they must conceal inside an empty gastropod (marine snails and slugs) shell.  When they grow too big for their shell, they must find a bigger one.  They are especially active at night but can be found by day in tidepools.  They are actually very fast little critters!

SEURAT'S HERMIT CRAB (Calcinus seurati)

I went to Pyramid Rock this past weekend and found a strange looking thing in the sand.  I just had to post this!  I emailed an expert and he said it’s most likely the exoskeleton of a Purple Rock Barnacle (Nesochthamalus intertextus). Barnacles are invertebrates that filter-feed and they do not move.  They are permanently attached to a hard surface.  This is most likely an exoskeleton of it’s larval stage, since it’s so tiny and since the adult stage looks drastically different.  See the adult stage here.  Doesn’t look like something out of a science fiction movie?

PURPLE ROCK BARNACLE (Nesochthamalus intertextus)