Bioacoustics of Grapsidae

DIAGNOSIS Carapace typically quadrilateral to quadrate; surface moderately flat, usually with marked striae, especially on branchial regions ( Banerjee 1960 : figs 1a-e, 5; Naderloo 2017 : fig. 30.1), exceptionally faint in Planes ( Chace 1951 : table 1); anterolateral margins entire or with one, may be two, teeth behind exorbital angle; front wide, much broader than orbits, entire, strongly deflexed, widely overhanging epistome between short eyestalks; suborbital margin running vertically from orbital angle to meet end of suborbital crest directly, no overlap (N. K. Ng et al. 2007 : fig. 5B); basal article of antenna immobile, bent; orbit small, open laterally; mxp3 leaving rhomboidal gape; both mxp3 merus and ischium with single longitudinal sulcus and lacking oblique setose crest (N. K. Ng et al. 2007 : fig. 7D; Davie et al. 2015a : fig. 71- 2.27N ); flagellum of exopodite usually present, may be strongly reduced or absent ( Geograpsus ); absence of stridulatory suborbital crest; pterygostomial region sparingly setose, with setae simple, plumose, never arranged in reticulated pattern; male chelipeds homochelous (except in Metopograpsus , merus usually with developed spines on anterodistal margin, fingers apically spoon-shaped; walking legs robust, distinctly flattened, usually armed with spines and bristles; mobile setae on dactylus of P2-P5; sterno-pleonal cavity without rim at level of telson, may be a faint rim; male gonopore next to articular membrane adjacent to P5 coxa (sternal emergence being proved by dissection), and opening in middle of sternite 8 thus far from suture 7/8 (except in Planes ); penis elongate, narrow (e. g. Grapsus ) or wide, short (e.g. Metopograpsus ), partially calcified; G1 short, sinuous or slightly curved, even twisted, usually with dense setae on apical part; pleon with six free somites plus telson; pleonal-locking mechanism of press-button type always present (but absent in Geograpsus ), functional throughout life, usually very marked, close to suture 5/6 or slightly remote ( Goniopsis ), with round or acute buttons, exceptionally developed and half-moon-shaped ( Metopograpsus ); small but distinct socket usually next to intestine ( Hartnoll 1965 ; Guinot & Bouchard 1998 : fig. 22; Köhnk et al. 2017 : figs 16, 17); vulva with operculum (McLay & Sal Moyan 2016). Tufts of hydrophilic setae generally lacking, but may be present between P3/P 4 in some species of Grapsus , in Goniopsis , Metopograpsus , Pachygrapsus ( Oliveira 2014 : table 2) and chiefly in Geograpsus , the single terrestrial grapsid species ( Greenaway 1988 : fig. 7.2.B-D; Paulay & Starmer 2011 ).