Stenothoe divae, Bellan-Santini, 2005

Bellan-Santini, Denise, 2005, Stenothoidae (Crustacea: Amphipoda) of hydrothermal vents and surroundings on the Mid-Atlantic Ridge, Azores Triple Junction zone, Journal of Natural History 39 (39), pp. 3435-3452 : 3440-3443

Stenothoe divae n. sp.

( Figures 3 , 4 )

Type locality

Mid-Atlantic Ridge, south-west of Azores, Segment 38 ° N, 38 ° 19.049N, 30 ° 40.139W, 788 m.

Material examined

DIVA 1 cruise, DV 11-5, 19 May 1994, Segment 38 ° N, 38 ° 19.049N, 30 ° 40.139W, 788 m: 25 specimens with two adult males, one male is the holotype, MNHN-Am5870 .

Diagnosis

Antenna 1 lacking nasiform process on article 1, no accessory flagellum. Mandible without palp. Gnathopod 1 with merus produced to the middle of the carpus. Gnathopod 2 with the propodus enlarged, palm oblique, excavate in the proximal part and largely indented in the distal part. Pereiopods 6–7 with expanded lobate basis. Telson entire.

Description

Male. Length 6 mm.

Head slightly shorter than two first pereon segments. Eyes present of moderate size. Antenna 1 lacking nasiform process on article 1. Antenna 1 exceeding length of body, articles 1 and 2 subequal, accessory flagellum absent, flagellum with 23 articles. Antenna 2 shorter than antenna 1 but longer than half of body, flagellum with 14 articles. Palp of mandible absent (represented by a single seta), cutting edge strongly toothed, without molar. Palp of maxilla 1 biarticulate. Inner plates of maxillipeds well separated, palp four-articulate.

Coxa 1 small, covered by coxa 2, anteriorly rounded. Coxa 3 subrectangular, coxa 4 very large, triangular, not posteriorly excavate. Gnathopods 1–2 subchelate, strongly different from each other in size and shape. Gnathopod 1 small, merus distally produced into a setose lobe reaching the middle of the carpus, carpus as long as propodus, non–lobate, propodus with palm oblique, undefined. Gnathopod 2 greatly enlarged, merus and carpus short, lobed, propodus with palm oblique, excavate in the proximal part and strongly indented in the distal part, limited proximally by a spine. In a second specimen, the propodus is less excavate. Dactylus equal to palm, inner margin sparsely setose. Pereiopods 3–4 slender. Pereiopod 5 with rectilinear basis. Pereiopods 6–7 with expanded and lobate basis, merus with an acute postero-distal lobe bearing terminal spines.

Epimeral plates 1 and 2 rounded, 3 rounded with the distal margin oblique. Pleonite 3 lacking dorsal process. Uropod 1 peduncle with four spines, longer than rami; uropod 2 shorter than 1, outer ramus three-quarters of the inner with, respectively, three spines. Uropod 3 with three lateral and four distal spines on the peduncle, ramus biarticulate, the proximal article with two distal spines. Telson entire, longer than broad, each lateral margin with one spine and one seta, one pair of subterminal setae.

Female. Female with the propodus of gnathopod 2 without excavation, but strongly indented.

Etymology

Name of the species is derived from the name of the DIVA cruise.

Relationship

This species is referable to the genus Stenothoe , due to no mandibular palp, and maxilla 1 with two-articulate palp. Seven species occur in the deep Atlantic: S. aequicornis Stephensen 1931 , S. bosphorana Sowinski, 1898 , S. coutieri Chevreux, 1908 , S. dollfusi Chevreux, 1887 , S. macrophthalma Stephensen, 1931 , S. marina Bate, 1856 , and S. richardi Chevreux, 1895 . Three species have been found in the North Sea or Norway Sea at more than 180 m deep: S. megacheir ( Boeck, 1871) , S. microps Sars, 1895 , and S. tenella Sars, 1895 . None of these species has a propodus of gnathopod 2 enlarged with a palm obliquely excavated in the proximal part and strongly indented in the distal part, a gnathopod 1 with merus distally produced into a setose lobe reaching to the middle of the carpus, and a telson with only one pair of spines. Stenothoe divae is considered a new species.

Distribution and habitat

Mid-Atlantic Ridge, south-west of Azores, Segment 38 ° N, 788 m depth. The specimens were collected on indurated sediment, among spongia, hydrozoans, gorgonians, and colonial tunicates.

Figures

Figure 3. Stenothoe divae, DIVA 1, DV11-5. (1, 2, 5, 6) Holotype male and (4) paratype female: (1) habitus; (2) gnathopod 1; (5) pereiopod 3; (6) epimeral plate 3. (3) Holotype male: gnathopod 2. (4) Paratype female: gnathopod 2. Scale bars: 100 mm.

Figure 4. Stenothoe divae, DIVA 1, DV11-5, holotype male. (1) Mandible; (2) maxilla 1; (3) maxilla 2; (4) maxilliped; (5) pereiopod 4; (6) pereiopod 5; (7) pereiopod 7; (8) pereiopod 6; (9) uropod 1; (10) uropod 2; (11) uropod 3; (12) telson. Scale bars: 100 mm.