Stenothoe senegalensis, Krapp-Schickel, 2015

Krapp-Schickel, Traudl, 2015, Minute but constant morphological differences within members of Stenothoidae: the Stenothoe gallensis group with four new members, keys to Stenothoe worldwide, a new species of Parametopa and Sudanea n. gen. (Crustacea: Amphipoda), Journal of Natural History 49 (37), pp. 2309-2377 : 2343-2348

Stenothoe senegalensis n. sp.

( Figures 18–20 ; Table 1)

S. gallensis Reid 1951: 228 ff. part., fig. 27

? S. uncinifera Mateus & Mateus, 1966: 177–178 , fig. 3–6

Holotype

Male 3 mm from Tarrafal, Île de Santiago near Dakar, Sénégal (71) 30 m depth, 02/ 03/1954, J. Cadenat coll., slide MVRCr 7705 .

Additional material

Male 3 mm from same locality as above: one slide MVRCr 7706 ; female ov. 2 mm, one Île de Gorée, Sénégal (50) from calcareous algae, 25/04/1953, J. Cadenat coll., slide MVRCr 7707 .

About 100 males, females, juveniles from Île de Gorée, Sénégal (50) from calcareous algae, 25/04/1953, J. Cadenat coll.; in alcohol, MVRCr .

Etymology

After the type locality.

Description

In parentheses, some characters of S. gallensis and citation of Reid (1951, p. 228 ff.) about his ‘ S. gallensis ’:

Length 3 mm.

Head. Eyes rounded, small (rather large in S. gallensis ; Reid: small). Antenna 1 subequal to head and peraeonites 1–4 (vs longer in S. gallensis ), flagellum with 12 arts (S.g. 22, Reid: 12). A 2 flagellum = peduncle (vs.> peduncle), flagellum with 14 arts (S.g. 18, Reid 14).

Peraeon. Peraeonite 4 wider than the ones before (vs not elongate, similar in length to peraeonite 3). Gn 1 length of propodus> length of merus + ischium together; length of propodus = 1.5× length of carpus (S.g. 3×). Gnathopod 2 male palm with two posterodistal humps, the proximal forming a right angle (vs without right angle). Gnathopod 2 female palm regularly rounded, smooth (see Reid 1951, fig. 27 g). Peraeopods: coxa 4 with notch on anterodistal corner; merus well produced distally (vs.only little produced distally), but not surpassing the middle of carpus; propodus clearly shorter than carpus + merus together (vs nearly as long as carpus + merus together).

Pleon. Uropods: U 1 not reaching end of U 3 (vs reaching end of U 3), with long peduncular spur. U 3 peduncle subequal to ramus (S.g. longer, Reid: the ramus is only a little, if at all, longer than the peduncle), with two robust spines along the upper margin and a pair on the distal margin (vs 5–6 spines); ramus art 1 with two distal spines (vs 1), ramus art 2 proximally much thicker than distally, with many coarse gutters, tip acutely uncinate (S.g.: upwardly bent in the middle and finely denticulate on the upper surface; Reid: serrated dorsally, proximal swelling ventrally).

Remarks

Reid (1951, p. 228) reports ovigerous females with 2 mm length and others with 5 mm length; thus, he clearly did not have only one species in his samples called ‘ S. gallensis ’. After the illustration of his S. cattai (p. 231, fig. 28), he probably had S. valida females (see below) in his collection of West African amphipods (sampling locality 11°54 ʹ N, 17°14 ʹ W, off Bathurst, Gambia), but the material of his ‘ S. gallensis ’ matches the here-described animals from Senegal. The most striking differences from S. gallensis or from S. valida are the body length, the shape of Gn 2 female, basis and merus of P 7, the shape of U 2, U 3. Differences from S. clavetta : the serration on the coxae and the shape of U 3. In the present material, there is some crenulation but never the incisions of S. clavetta .

The material could belong to Stenothoe uncinifera Mateus and Mateus (1966 , p. 177–178, fig. 3–6), but only one incomplete female was found and the description is poor and shows an artifact,? damaged or malformed U 3 (sampling locality Ponta da Mina, île Principe). The shape of basis and merus P 7 is similar to that of S. valida , but otherwise the species belongs to the S. gallensis group.

Distribution

Senegal, Atlantic Ocean.

Herewith ends the description of various members of the Stenothoe gallensis group.

As the above-described material is quite close to the morphology of S. valida Dana (which has straight and unsculptured U 3 articles also in males, and thus does not belong to the S. gallensis group), a description of this species is herewith included:

Figures

Figure 18. Stenothoe senegalensis n. sp., Senegal, male, 3 mm: Gn 2 = second gnathopod; Us = urosome; U 1, 2, 3 = uropod 1, 2, 3; T = telson.

Figure 19. Stenothoe senegalensis n. sp., Senegal male: Mx 1 = maxilla 1; Md = mandible; Gn 1, 2 = gnathopod 1, 2; P 3–7 = peraeopod 3–7.

Figure 20. Stenothoe senegalensis n. sp., Senegal female: Gn1, 2 = first and second gnathopod; U2, 3 = second and third uropod.