Bioacoustics of Ambicholestes trilobatus

Diagnosis. Rostrum present in depressed position between antennae 1. Antenna 1 peduncle article 1 and antenna 2 peduncle article 3 (rest of antenna missing) partly covered withmicrosetules. Anteriormargin of cephalon and rostrum covered by microscales. Pleon and urosomites dorsally with dense cover oflong, very fine setules. Article 2 of pereopod 2 with anterior margin trilobate; presumed stridulation organ present. Further description. Rostrum narrow, pointed. Antenna 1 peduncle article 1 with 2 recurved robust setae ventrally, with ventral to medial cover of microsetules. Antenna 2 peduncle article 3 with mid-medial robust seta, with dorsal to medial cover of microsetules; ventroapical projection of article 2 as long as wide, triangular, with 4 long lateral and 2 short medial setae.

Ambicholestes (Ambicholestes) trilobatus n.sp. Figs 6-8 Material examined. HOLOTYPE : fully developed female, 3.5 mm , with empty marsupium, Long Island , Chesterfield Reef , Coral Sea , seaward face, 20 m , "Lady Basten", N.L. Bruce , 4 May 1979 , QM Wl1668. Unique. Diagnosis. Rostrum present in depressed position between antennae 1. Antenna 1 peduncle article 1 and antenna 2 peduncle article 3 (rest of antenna missing) partly covered withmicrosetules. Anteriormargin of cephalon and rostrum covered by microscales. Pleon and urosomites dorsally with dense cover oflong, very fine setules. Article 2 of pereopod 2 with anterior margin trilobate; presumed stridulation organ present. Further description. Rostrum narrow, pointed. Antenna 1 peduncle article 1 with 2 recurved robust setae ventrally, with ventral to medial cover of microsetules. Antenna 2 peduncle article 3 with mid-medial robust seta, with dorsal to medial cover of microsetules; ventroapical projection of article 2 as long as wide, triangular, with 4 long lateral and 2 short medial setae. Coxal plates 5 and 6 posterior lobe rounded with upturned part rounded. Distalmost part of plates 3 and 4, anterior lobe of plate 5, posterior lobe of plate 6, and anterior lobe of plate 7 with microscales. Pleonal sideplates 1 and 2 evenly rounded. Mouthparts normal. Mandibular palp laterally to ventrally with lose cover of acute cuticular scales. Pereopod 1 article 6 without posterodistal tooth, with 4 posterior robust setae. Pereopod 2 article 6 with 4 posterior robust setae; article 2 anterior margin proximal to lobate part with a few small marginal teeth. Uropod 1 outer ramus about 5 times longer than broad, with 7 lateral robust setae; inner ramus ca. 40% length of outer ramus, with lateral and apical robust setae. Urosomites 1 and 2 free. Urosomite 3 and telson fused dorsally, but with distinct subcuticular line of articulation. Colour and biology. Not known. Etymology. The specific epithet alludes to the shape of the anterior margin of pereopod 2 article 2.