Pinnotheroidea De Haan 1833

Female Pinnixa tubicola, found intertidally at March Point, Padilla Bay, by Sarah Bewley and Melissa Moxey along with terebellind tubeworms. Carapace width 7 mm. (Photo by: Dave Cowles, June 2012)

The dactyls are strongly curved. Setae on legs 3 and 4, especially on the dorsal edge of the merus, are long and featherlike. According to Hart (1982), the legs of gravid females have few setae while males and non-gravid females have many more setae (which may be used for swimming), plus hard carapaces. Hard individuals (mature males and non-gravid females) have more opaque carapaces, flatter legs, more long setae on the legs, and red articulations on the carapace. This individual seems intermediate between these conditions. This closeup dorsal view of the carapace shows the egg clusters in the gill chamber. The dorsal longitudinal grooves extending back from the orbits as well as the transverse groove can also be seen.

This closeup of the chelipeds shows the tooth on the inner margin of the dactyl

This ventral view shows the larger cluster of eggs carried on the abdomen, as is normal for Brachyuran crabs (and other members of Suborder Pleocyemata). I have not heard reports of other brachyuran crabs which have some of their eggs up in the gill chambers, as this individual does. Also, several references state that in gravid females the abdomen is wider than the carapace, but that is not true of this individual. Johnson and Snook (1955) state that the propodus has two rows of setae on the ventral side. The outer row extends to the base of the fixed finger while the inner row extends to the tip. Those rows can be seen here.

The legs are flattened, translucent with darker spots or reticulations, and are fringed with long, abundant plumose setae. It can also be seen that the dactyls and the propodus of the walking legs are of approximately equal length (though the dactyls are mostly extended downward in this photo and may appear shorter), and that the dactyls are nearly straight. Notice that the last leg is much shorter than the others.

This dorsal view shows the chelae. The tips of the chelae can cross.

This view of the underside shows how much lighter the abdomen is, and also reveals that this individual is a female.

Pinnixa eburna, carapace width 7 mm wide by 3.5 mm long. Found in a burrow of Abarenicola pacifica on the mudflats of Padilla Bay. (Photo by: Dave Cowles, June 2009)

The dactyl tips of the walking legs are curved.

This closeup of the face and claw of the male shows the red cornea of the eye and the thick propodus and curved dactyl of the cheliped.

There is no rostrum and no teeth between the eyes, and the outer margins of the eye sockets are rounded.

Here is another individual, with a bit more setae than the one above. This one is likely a female (not the same one as below), from Tresus capax. Photo by Dave Cowles, July 2008

Pinnixa faba, likely a male, from the mantle cavity of Tresus capax. Scale in background = mm (Photo by: Dave Cowles, July 2005)