Bioacoustics of Gecarcinus

Remarks. Guinot et al . (2018) reexamined all gecarcinid morphological characters, and divided the family Gecarcinidae into two subclades. The first clade included: Cardisoma Latreille, 1828 , Discoplax A. Milne-Edwards, 1867 , and Tuerkayana Guinot et al. , 2018 ; the second subclade, with a higher degree of terrestriality, included: Gecarcinus Leach, 1814 , Gecarcoidea H. Milne-Edwards, 1837 , and Johngarthia Türkay, 1970 . Among the important characters shared by Gecarcinus and Johngarthia is the stridulatory apparatus, which is used to produce sounds when these crabs are disturbed in their retreats ( Abele et al . 1973 ). The sound is produced when oblique rows of rugosities on the subhepatic region are rubbed against the tuberculated internal margin of the merus of the cheliped in G. quadratus , or against a longitudinal tuberculated ridge on the internal surface of the palm of the major cheliped in G. lateralis ( Klaassen 1973 ; Abele et al . 1973 ). The ability to absorb water from the substrate is well developed in Gecarcoidea natalis ( Pocock, 1889 ) and Gecarcinus lateralis , in which setal tufts extend along the first three pleonal somites and on the coxa of P5 to establish a connection with the pericardial sacs ( Bliss 1963 , 1968 ; Greenaway 1988 ). In Gecarcinus ruricola and Gecarcoidea lalandii H. Milne Edwards, 1837 , the posterior margin of sternite 7 is lined with dense hydrophilic setae in contact with tufts of setae on the coxa of P5 and pleonal somites 1-3 ( Guinot et al . 2018 ).