82 — Dwarf swimming crab, Liocarcinus corrugatus

Liocarcinus corrugatus Pilot Bay,
 Mt. Maunganui, July 2018.

Liocarcinus corrugatus Pilot Bay,
 Mt. Maunganui, 14/11/16.

Liocarcinus corrugatus Pilot Bay,
Mt. Maunganui, 14/11/16. This is what you see,
as they break through the sand.

Liocarcinus corrugatus Pilot Bay,
 Mt. Maunganui, 14/11/16.

Liocarcinus corrugatus Pilot Bay,
 Mt. Maunganui, 14/11/16.

Dwarf swimming crabs (Liocarcinus corrugatus (Pennant, 1777)) have a nearly global temperate distribution (essentially, all over the place in warm waters), which suggests that they have a really long planktonic larval dispersion stage.

Dwarf swimming crabs are a smallish crab (to ~40mm across the carapace). Usually they are sub-tidal, down to ~130m, but occasionally they can be found in sand at extreme low tides, where they emerge out of the sand just after low tide. When disturbed they play dead and lie motionless—they seem quite passive and not aggressive like other paddle crabs (e.g., Ovalipes catharus (White, 1843)). After about 30 seconds (I didn't time it), they suddenly come alive and then very quickly bury themselves.

I do wonder if this playing dead makes them easy prey for seagulls though.

These photos were taken at Pilot Bay, Mt. Maunganui, 14/11/16 and there nearly a dozen of them (spread along ~25m of Pilot Bay), all coming up out of the sand, just after low tide.








































More info:

NIWA crabs guide: Wilkens, S. & Ahyong, S. 2015. Coastal crabs: A guide to the crabs of New Zealand, Version 1.