Bioacoustics of Metopa propoda

Description. Head . Head length subequal to pereonite 1 and 2 combined. Interantennal lobe strongly projecting, broadly rounded. Eyes rounded. Antenna 1 and 2 sexual dimorphisms. In female antenna 1, subequal to or slightly longer than antenna 2, peduncular articles 1 and 2 of equal length, flagellum 12–13 articles, accessory flagellum absent; antenna 2 peduncular article 5 the longest, flagellum 3 / 4 length of peduncular article 5, with 7–8 articles. In males, antenna 1 is shorter than antenna 2, primary flagellum article 1 longest, article 2 half-length of article 1 (based on male paratype ); antenna 2 with flagellum shorter than half-length of peduncular article 5. Mouthparts . Right mandible incisor with four large teeth; lacinia mobilis serrate edge broader than that of the incisor, with 9 teeth; palp 3 - articulate, basal article quadrangular, second one the longest, very short and small third article carrying one long distal seta. Left mandible incisor with 11 teeth unequal in size, lacinia mobilis absent. Maxilla 1 palp with one article, with row of 4 robust setae in distal 1 / 4 length of medial margin and 3 setae subapically. Maxilla 2 plates in ordinary tandem position. Maxilliped inner plate fused with apical notch and small marginal setae; outer plate visible as acute tooth-shaped prolongation; dactylus subequal in length to article 3. Coxa 2 tongue-shaped, with marginal setae; coxa 3 larger than coxa 2, rectangular; coxa 4 not excavated, about 1.3 times wider than long. Gnathopods and pereopods . Gnathopod 1 sexual dimorphism, propodus suboval and narrow, palm not defined; carpus in female wider and shorter than that of in male, longer than propodus, proximally narrower than distally; merus projecting under carpus, all articles beset with groups of short setae. Gnathopod 2 sexual dimorphism, female propodus slightly widening distally, hind margin subequal in length to palm, which is defined by a shallow notch and not very strong tooth and has many small serrations next to dactylus insertion; dactylus somewhat shorter than length of palm; carpus in lateral view wider than long, triangular, in medial view oval-shaped; merus not lobate, in lateral view rectangular, in medial view triangular. Gnathopod 2 male propodus hind margin shorter than palm, which is defined by a very large rectangular excavation and strong thumb-shaped palmar corner and has 4 small serrations; carpus in lateral view triangular, dorsal margin with row of stridulating knobs, in medial view rectangular, with anterodistal acute projection; merus not lobate. Pereopod 3 longer than pereopod 4, all articles elongate and weak, distal three articles with setae on posterior margin. Pereopod 4 with posterior margin of merus, carpus, and propodus with a few transverse rows of small setae; merus somewhat curved. Pereopod 5 basis rectilinear; merus to propodus anterior margin with several transverse rows of small setae; merus wider than carpus, with shortly lengthened posterodistally. Pereopod 6 and 7 bases widened with rounded posterodistal lobe; merus with lengthened posterodistally hardly reaching to distal margin of carpus; merus to propodus of both armed as in pereopod 5. Uropods and telson . Uropod 1 peduncle much longer than subequal rami, with short robust setae on peduncle and outer ramus; inner ramus unarmed with setae. Uropod 2 peduncle longer than rami, with short robust setae; outer ramus slightly longer than inner one, armed with robust setae; inner ramus unarmed. Uropod 3 peduncle subequal to ramus; article 1 of ramus slightly longer than spine-shaped robust article 2. Telson tongue-shaped, distally rounded, with three marginal robust setae on each side dorsally.