Presumptive stridulatory organs in Paranthura cf. japonica Richardson, 1909 (Isopoda: Cymothoida: Paranthuridae)

Abstract

Abstract Morphological diversity of sound-producing structures has not been well investigated among members of superorder Peracarida. Presumptive stridulatory sound-producing organs have been reported in some amphipods and tanaidaceans, and sound production by these organs has been documented in two isopod species in Oniscidea and Sphaeromatidea. We describe three presumptive stridulatory organs in the paranthurid isopod Paranthura cf. japonica Richardson, 1909, the first case known in Cymothoida. One type, consisting of a scale-bearing knob on the posterolateral corner of a pereonite and the scale-bearing anterolateral corner of the succeeding pereonite, was found between two pairs of pereonites (1, 2 and 2, 3). A second type involves a serrated structure in the sub-posterolateral region of pereonites 1 and 2, with the sharp anterolateral margins of pereonites 2 and 3 appearing to provide corresponding plectra. The third type involves an extension bearing a pair of serrated structures on the posteroventral margin of pereonites 1 and 2; the anterior-ventrolateral edges of pereonites 2 and 3 appear to provide corresponding plectra. All three organs occurred in both sexes of P. cf. japonica. Our discovery of novel, presumptive stridulatory organs in an intertidal isopod indicates that much remains to be learned about the biology of even common peracarid species.