New Amphipoda crustaceans species recently found in Vietnam nearshore waters

Abstract

Taxonomical study recently realized with materials collected from nearshore waters of Vietnam has contributed 7 new species to science, belonging to families: Amphithoidae, Corophiidae, Liljeborgidae, Lysianassidae and Synopiidae.

Cymadusa exavata sp. n. (Figs. 1-16)

Male: Body large in size. Anterofrontal margin with low ocular lobe. Eyes subquadrate, reddish. Antennae 1 and 2 subequal in length, reaching midpoint of body length. Antennae 1 with 1^st and 2^nd peduncular article similar in length. Flagellum 26-articulated, accessory flagellum 1 articulate. Antennae 2 with 4^th as long as in length with 5^th peduncular article, flagellum 24-articulated. Mandibule palp 3-jointed, 2^nd and 3^rd joints equal in length, with distal long seta. Gnathopod 1 (male) with 5^th article cup form, 6^th article large, subquadrate, palm transverse widely excavated, delimited by a strong tooth. Gnathopod 2 with slender, curve 2^nd article. 5^th and 6^th article subequal in length, the later one subretangular, palm oblique, short. Claw like 7^th article overeaching beyond palm. Uropod 1 with ramus unequal, lateral margin setose. Uropod 2 with equal ramus. Uropod 3 with rami longer than 1/2 peduncle. Telson quadrate distally setose.

Female: Unknown.

Kanaka quadrata sp. n. (Figs. 17-32)

Male: Anterolateral cephalic lobe developed, reaching nearly distal margin of 3th peduncular article of Ant 2. Eyes large, occupied the whole cephalic lobe. Antennae 1, 2^nd and 3^rd peduncular articles subequal in length. Flagellum 8-articulated. Antennae 2 with 4^th peduncular article very long, inflated, distal angle with a hooked tooth. 5^th article stick shaped, 1/2 as long as 4^th article. Gnathopod 1 with coxa anteriorly and posteriorly prolonging, 4^th, 5^th and 6^th articles subequal in length. Gnathopod 2 with 2^nd article slender, 5^th subtriangular, 6^th article widely quadrate, palm transverse, delimited by a strong tooth. Uropod 3 uniramus. Telson lobe medially excavated. Urosomit coalescent.

Female: Sexual dimorphism in antennae 2, gnathopod 1 and 2 structures.

Listriella tuberculata sp. n. (Figs. 33-50)

Male: body small in size, whitish. Eyes round, large. Antennae 1 with 1^st peduncular article large, 3^rd article very small, flagellum 12-articulated, accessory flagellum 3-articulated. Antennae 2 with 4^th and 5^th peduncular articles equal in length. 14-articulated. Mandibule palp 3-jointed the 2^nd the longest. Gnathopod 1 (male) with 5^th article flat, cup form in shape, 6^th ovate, palm overeaching midpoint of posterior margrin, setose and spinose, delimited 2 small tubercular spines. In proximal part near to basis occuring 3 large tubercules. Gnathopod 2 with similar structure, but 6^th article with palm without tubercules at proximal part, only setose. Urosomit with a spine in dorsal margin. Uropod 1 with ramis subequal, longer than peduncle, outer ramus slender, biarticulate inter ramus lanceolate. Telson bilobed slender, distally spinose epimera 1-3 with poster distal angles untoothed. Pleonit segment dorsal margin smooth.

Hippomedon pluriarticulatus sp. n. (Figs. 51-60)

Male: body large in size. Dorsal margin without carina. Eyes large, reniform. Antennae 1 with 1^st peduncular article longer than 2^nd and 3^rd article combined. Flagellum 16-jointed 1^st joint very large. Accessory flagellum 6-articulated. Antennae 2 reaching to midpoint of body length, 4^th peduncular article large subquadrate, shorter than 5^th article, flagellum 46 articulate. Mandibule palp with 2^nd joint the longest. Gnathopod 1 short, 5^th and 6^th articles subequal in length, 6^th article subrectangular, palm tranverse distally located. Dactylus claw like, overeaching beyond palm, posterior margin armed with a spine. Gnathopod 2 long, 2^nd article slender very long, 5^th article 2 times as long as 6^th, palm transverse distally located. Surface of 5^th and 6^th article densely setose. Claw like dactylus short, beak form. Uropod 1 and 2 rows of spines. Uropod 3 with rami longer than peduncle outer ramus biarticulate. Telson bilobed slender angle toothed. Epinera 3 with osterodistal.

Hippomedon bioculatus sp. n. (Figs. 61-71)

Male: body large in size, dorsal margin without carina. Head small, no rostrum. Eyes present with two distinct omnatidia. Antennae 1 with robust 1^st article, 2^nd and 3^rd articles minute. Flagellum 7-articulated Antennae 2 short, reaching to 1/3 body length 4^th and 5^th articles equal in length, flagellum 26-jointed. Mandibule palp 3-jointed, 2^nd and 3^rd joints similar in length. Gnathopod 1 (male) with 5^th article longer than 6^th, this article elongate ovate in shape, palm oblique, reaching to 1/2 posterior margin delimited by a spine, palm margin scarcely setose. Claw like dastylus covered palm length. Gnathopod 2 with 5^th longer than 6^th article, this later subrectangular, densely setose on surface. Palm transvese, distally located in 6^th article. Dactylus very short, beak form. Uropod 1 and Uropod 2 with rami equal peduncle, outer ramus biarticulate. Telson bilobed paralelly elongated. Epimera 3 with posterodistal angle produced to a minute tooth. Epimera 1, 2 with a spine in dorsal margin.

Tiron quadrioculatus sp. n. (Figs. 72-86)

Male: Dorsoanterior margin of head curving evenly to rostrum, without forming extended spine. lateral cephalic lobe round. Rostrum jointing obliquely anteroventrally. Eyes not presented, accessory eyes composed by 4 omnatidia. Antennae 1 with 2^nd and 3^rd articles equal in length. Flagellum 10-articulated, accessory flagellum 4-articulated. Antennae 2 with 4^th peduncular article 2 times as long as 5^th, flagellum
9-articulated. Mandibule palp with elongate 2^nd joint. Gnathopod 1 and 2 (male) similar in structure, with 5^th article slender, 2 times as long as 6^th article. 6^th article cylindrical, lateral inferior margin, as in 5^th article, with rows of long setae. Claw like dactylus elongate. Pereopods 3-7 with short, cylindrical, 4-6 articles laterally armed with rows of spines and rudimentary distal dactylus. Uropods 1 and 2 with rami shorter than peduncle. Uropod 3 with rami longer than peduncle, outer ramus biarticulate, inner ramus with dense setose lateral margin. Telson with 2 slender lobes, slightly distally separated. Pleomit dorsal margin serrated. Urosomit 1, 2 with strong teeth in posterodorsal margin.

Pseudotiron sublongicaudatus sp. n. (Figs. 87-100)

Male: Body small in size. Dorsoanterior margin of head forming an extended forehead protuberance. Pleonit 1-5 with serrated posterodorsal margin. Antennae 1 peduncular article equal in length with 3^rdarticle, 2^nd article short, flgagellum 15-articulated, accessory flagellum 3-articulated. Antennae 2 with 5^th peduncular article shorter than 4 article, flagellum 17-articulated, lateral margin peduncular articles setose. Mandibule palp with 2^nd joint 2 times as long as 1^st joint. Gnathopod 1 with 5^th and 6^th articles elongate, slender 6^th article not diffenciated, 5^th article 2,5 times as long as 6^th article. Claw like dactylus elongate and toothed in ventral margin. Uropod 1 and 2 with rami longer than perduncule, inner ramus longer than outer, both biarticulate. Uropod 3 with unequal 2 ramus, lateral margin densely setose. Telson bilobed, slender, slightly separated distally. Urosomit 1-3 with poster dorsal marginal spines.