Crusaceans family Melitidae (Amphipoda - Gammaridea) from Vietnam sea

Abstract

By the results of taxonomical study on the amphipod crustaceans family Melitidae collected from different localities in the nearshore waters of the Vietnam sea, 20 species belonging to 9 genera has been recorded, among them 17 species are new to the Vietnam sea, of which 6 are new to science. Up to now, Melitidae is one of two families the most rich in species composition of the fauna of Amphipoda Gammaridea of the Vietnam sea.

Ceradocus nghisonensis sp. nov.

Antenna 1 with peduncular article 1 shorter than article 2. Flagellum 15- jointed, accessory flagellum 4- jointed. Antenna 2 longer than antenna 1 peduncle, article 4 slightly longer than article 5. Flagellum with 11 articles. Mandibular palp 3- jointed, article 3 as long as 1/3 article 2. Gnathopod 1 left and right symmetrical. Palm short, reaching about 1/2 posterior margin of article 6, densely setose. Gnathopod 2 left and right asymmetrical. Propodus ellipsoid in shape, palm obbique, reaching 1/3 posterior margin, with 2 quadrate humps, separated by narrow incision. Gnathopod 2 smaller. Pleonit 1-3 with small serrations. Epimera 3 posteriodistal corner with small tooth, posterior margin with 5 teeth, ventral margin with 3 teeth, Uropod 3 large, leaf in shape, subequal ramus, lateral margin serrated. Telson with 2 lobes obbiquely pointed.

Ceradocus multidentatus sp. nov.

Antenna 1 with pedunculer article 1 shorter than article 2 (2/3 as long as), flagellum 15 jointed, accessory flagellum 3- jointed. Antenna 2 overeaching antenna 1 peduncle, article 4 longer than 5, flagellum 7- jointed. Mandibuler palp with proximal part slightly produced, article 3 very short, 1/4 as long as article 2. Gnathopod 1 left and right symmetrical. Right gnathopod 2 with propodus long, subrectangular in shape, dorsal margin straigth, smooth, palm oblique, occuping about 1/2 posterior margin, with a large, shallow excavation in middle part, distally limited by a pointed, low hump, armed with setae and spines. Left Gnathopod 2 smaller in size, palm obliqe, with a quadrate hump in distal part of the middle excavation. Epimera 3 with acute posterior corner, serrated posterodorsal and posteroventral margin. Uropod 3 ramus lanceolate in shape, equal in size. Telson triangular in form.

Ceradocus setosus sp. nov.

Antenna 1 peduncular article 1 and 2 equal in length, flagellum 25- jointed, accessory flagellum 5- jointed. Antenna 2 article 4 and 5 equal in length, flagellum 15- jointed. Mandibular palp with article 1 short and toothed, article 3 short 1/4 as long as article 2. Gnathopod 1 left and right symmetrical: article 6 distally tapered, palm overeaching the middle point of posterior margin. Gnathopod 2 asymmetrical left and right. Gnathopod 2 left large, article 6 ovale in shape, distally tapered, palm oblique, with a small middle excavation, delimited by 2 nodules triangular and quadrish in form in distal part, and a triangular hump in proximal part.. The surface and lateral margin of article 5-6 densely setose. Dorsal margin of pleonit segments serrated. Epimera 3 posterior margin serrated, posterior corner acute. Uropod 3 lacking.

Melita haiphongensis sp. nov.

Antenna 1 overeaching half length of body, pedoncular article 1 shorter than article 2, flagellum 15-20 jointed. Accessory flagellum 3-jointed. Antenna 2, article 4 subequal to article 5, flagellum 7-jointed. Mandibular palp 3-jointed, article 2 curved, article 3 longer than article 2, with distal setae. Gnathopod 1 coxa rectangular, article 5 semilunar, setose, article 6 shorter than article 5, distally produced with distal protuberance. Palm short, transverse, densely setose. Gnathopod 2 greater, article 5 cup in shape, article 6 large subquadrate, with oblique posteroventral margin. Palm oblique, occuping half length of posterior margin, not serrated, but armed setae and spines. Uropod 3 with inner ramus scale shaped outer ramus stick in form, 2.5 times in length of peduncle, spiniform, setose along outer margin on the surface.

Quadrimaera vietnamica sp. nov.

Head with developed eyes lobes. Antenna 1 peduncular article 1 slightly shorter than article 2, flagellum 28-jointed, accessory flagellum 10-jointed. Antenna 2 peduncular article 4 longer than article 5, flagellum 10- jointed. Mandibular palp with article 3 a half length of article 2. Gnathopod with article 5 nearly semilunar in shape, setose in margin, palm short. Gnathopod 2 with article 5, article 6 high cup in shaped, palm clearly oblique forming an acute angle with ventral margin with an shaped medial shallow excavation, by both sides 2 low humps and delimited by 1 strong, acute triangular tooth. Uropod 3 with acute posterior corner, no serrated in posterior margin.

Quadrimaera anhi sp. nov.

Head with anterior margin nearly straigth. Antenna 1 with peduncular article 1 shorter than article 2. Flagellum 15- pointed, accessory flagellum 6-jointed. Antenna 2 with article 4 longer than article 5, flagellum 6-jointed, mandibular palp with article 3 shorter than article 2. Gnathopod 1 with article 6 nearly semilunar in shape, slightly longer than article 5, posterior margin densely setose. Gnathopod 2 with article 6 subrectangular, parallel margins. Palm transverse, delimited distally by a low strong triangular tooth, with an medial deep shaped excavation and 2 high nearly quadrate humps by both sides. Dactylus thick, all covered palm. Epimera 3 with blunt posterior corner, posterior margin weakly serrated.