Metopa torbeni, Krapp-Schickel, 2009

Krapp-Schickel, T., 2009, New and poorly described stenothoids (Crustacea, Amphipoda) from the Pacific Ocean., Memoirs of Museum Victoria 66 (1), pp. 95-116 : 110

publication ID	https://doi.org/ 10.24199/j.mmv.2009.66.12
DOI	https://doi.org/10.5281/zenodo.12211975
persistent identifier	https://treatment.plazi.org/id/03818F6E-9038-FF89-FF44-9280FAFCFCBE
treatment provided by	Felipe
scientific name	Metopa torbeni
status	sp. nov.

Treatment

Metopa torbeni View in CoL n.sp.

Fig. 12 View Figure 12

Holotype: 1 spec.?sex 3mm. Danish Exp. to Siam by Carl Mortensen , Gulf of Thailand, 1.6 km S of Ko (h) Chuen, shells; dredge; 1. February 1900; 30 Fv. = 54m; slide ZMUC CRU-20193 .

Type locality: Gulf of Thailand.

Etymology: Dedicated to the 90th birthday of Torben Wolff, indefatigable crustaceologist at the Copenhagen Museum.

Description. Based on?sex, 3mm.

Head. Eyes rounded. Antenna 1 robust, longer than head and peraeonites 1–4, longer than antenna 2; peduncular article 1 length about two times the width; flagellum with 14 articles; accessory flagellum absent. A2 much shorter than A1, peduncle robust, flagellum longer than peduncle article 5, with 8 articles.

Mouthparts. Mandible palp not clearly seen, with one long distal seta. Maxilla 1 palp 1–articulate. Maxilla 2 outer plate sitting next to inner one. Maxilliped inner plates not fused, surpassing length of ischium, rectangular; outer plate lacking, dactylus a bit shorter than propodus.

Peraeon. Coxa 2 oval without tooth; Cx3 tongue-shaped; Cx4 not excavated, anterior and posterior margin rounded, much wider than long. Gnathopods 1–2 extremely dissimilar in shape and size. Gnathopod 1 dactylus short and thickened; propodus elongate, palm not defined, about 4 x as long as wide; carpus much longer than propodus, also with parallel margins, proximally wider than distally; merus incipiently chelate, with free obtuse distal end; all articles beset with groups of setae. Gnathopod 2 length of propodus longer than Cx2, subpiriform; hind margin much shorter than length of palm which has one wide shallow excavation near palmar corner and 4 humps next to dactylus insertion; palmar corner not well defined. Dactylus same length like palm; carpus shorter than wide, cup-shaped, merus not lobate. Peraeopod 4 merus anterodistal margin somewhat lengthened. Peraeopod 7 basis widened with rounded posterodistal lobe; merus lengthened and widened, reaching about 3/4 carpus length.

Pleon. Urosomites articulation not clearly visible. Uropod 1 peduncle nearly twice as long as subequal rami, with 5 short robust setae; U 2 peduncle also beset with small robust setae, longer than longer ramus, rami unequal; U 3 peduncle longer than ramus, article 1 of ramus longer than article 2.

Telson . Not reaching end of peduncle U3, with 2 robust setae.

Female (sexually dimorphic characters). Unknown.

Habitat. Marine; among shells, 54m.

Distribution: Gulf of Thailand, Pacific Ocean.

Remarks. Despite the fact that the mandible palp of this small specimen was not clearly visible, this new species must belong to the group around the type of Metopa , having a very specialized Gn1 with a short dactylus, narrow propodus, elongate carpus distally narrowing and a short rectangular merus with a free distal margin. However, Gn2 propodus is different from all other members, as M. clypeata ( Krøyer, 1842) ; M. cristata Gurjanova, 1955 ; M. kobjakovae Gurjanova, 1955 ; M. koreana Gurjanova 1952 ; M. leptocarpa Sars, 1883 ; M. norvegica (Liljeborg, 1851) , M. robusta Sars, 1895 ; M. spitzbergensis Brüggen, 1907 ; M. submajuscula Gurjanova, 1948 : all have a clearly pronounced tooth on the palmar corner, and most of these species are rectipalmate. Even if the present specimen is a young one, it is quite improbable that allometric growth will change the propodus to such a degree.