A new genus and species of pinnotherid crab (Decapoda: Brachyura: Pinnotheridae: Pinnothereliinae) with a unique male abdominal appendage, and its symbiotic relationship with a sipunculan worm (Sipuncula) from Miami, Florida, U.S.A.

Abstract

Abstract A new genus and species of pinnotherid crab, Laminapinnixa miamiensis, is described based on specimens mostly collected from sipunculan burrows in intertidal sand flats on Virginia Key, Miami, Florida. Males of this crab are characterized particularly by the presence of a conspicuous, broad, flattened, ventral abdominal appendage, herein referred to as the “abdominal plate” (AP). This structure has not previously been reported from brachyurans and occurs in males of all sizes (measured by carapace width, CW). Among 89 males and 87 females recovered, 50 crabs (24 males, 26 females) were associated with burrows of Sipunculus nudus Linnaeus, 1766. Hosts of most other specimens were not determined, but it is suggested that many were also likely associated with sipunculans. Eighteen sipunculan burrows had solitary crabs, whereas 15 had more than one; 14 of the 15 had heterosexual pairs. Carapace width (CW) and carapace length (CL) for males were 2.5 to 6.6 mm ( = 4.5 ± 1.0 mm) and 1.3 to 3.4 mm ( = 2....