Parametopa gorea, 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 : 2365-2368

Parametopa gorea n. sp.

Figures 26 , 27

Holotype

Adult specimen 3 mm from Gorée (island near Senegal) 17–3-53, ‘contenu stomacal de Spondyliosoma cantharum ’, slide MVRCr 7671 .

Additional material

Fem. ov. 3 mm, fem. 2.5 mm, same locality, stored in alcohol at MVRCr.

Etymology

Collected on the coasts of Gorée, Italian Gorea, a small island off the coast of Senegal.

Diagnosis

Gn 1 propodus subchelate, merus reaching end of carpus; Gn 2 propodus anterior and posterior margin parallel, palm oblique, with several incisions and humps; basis with many robust spines on anterior margin; U 1–3 and T strongly spinose.

Description

Length. 2.5–3 mm.

Head. Antennae subequal in length, length of A 1 ped. art 1 = art 2, art 3 about one third; flagellum with 14 arts. A 2 peduncle art 4 somewhat longer than art 5, flagellum with eight arts. Mouthparts: Mx 1 palp with one art; Mx 2 lobes in riding position; Md palp lacking; Mxp narrow, OP vanishing.

Peraeon: Gn 1 subchelate, merus reaching end of carpus, distally not acute but rounded ending; propodus ovoid, palm oblique, about half length of propodus. Cx 2 anterior margin regularly convex, posterior margin concave; Gn 2 basis on anterior margin beset with many strong spines; carpus triangular, length subequal to width; propodus with nearly parallel margins, palm oblique, with many more or less deep incisions and humps; dactylus about half length of propodus. Cx 3 narrow, with parallel margins, distally slightly serrate, Cx 4 much wider than deep, ovoid. Peraeopods: P 3> P 4; P 3 basis with many setae anteriorly; P 5 basis rectilinear, dactylus ≥ half length of propodus; anterior margin of merus, carpus and propodus with many spines; P 6, 7 basis widened, merus on both margins with spines, posterior one widened and lengthened, but not reaching half length of carpus.

Pleon: Ep 3 posteriorly bluntly produced; U 1–3 peduncle richly spinose; U 1 ped> subequal rami; U 2 rami unequal; P 3 ped> ramus, length of ramus art 1 = art 2; T with 5 pairs of spines marginally.

Distribution

Senegal, Atlantic O.

Key to Parametopa species

1. Gn 2 propodus rectangular, palmar corner 90° (rectipalmate) or even less ..... 2

- Gn 2 propodus with oblique palm, palmar corner much more than 90° ......... 3

2. Gn 1 simple, Gn 2 palm concave; A 1 flagellum with 4 arts, U 3 ramus art 1 naked ................................... P. crassicornis Just, 1980 (3.2 mm) NW Greenland

- Gn 1 simple to subchelate; Gn 2 palm straight; A 1 flagellum> 10 arts, U ramus art 1 with marginal spines .................................................................................... .................. P. kervillei Chevreux, 1901 (5 mm) French coast of English Channel

3. Gn 2 propodus palm with U-shaped excavation near palmar corner, palm defined by prominent elevation; P 5–7 with very few marginal spines; U 3 ramus and T naked ................................................. P. alaskensis ( Holmes 1904) (? mm) Alaska

- Gn 2 propodus palm with several small incisions, palm defined by blunt corner; P 5–7 richly spinose on both margins; U 3 ramus and T densely beset with spines .................................................. P. gorea n. sp. (2.5–3 mm) West Africa, Senegal

Within the present material from the Red Sea, I found a stenothoid with Gn 1 similarly long as but wider than Gn 2:

Figures

Figure 26. Parametopa gorea n. sp. male, Senegal: A 1, 2 = antennae; Mx 1, 2 = first and second maxillae; Md = mandible; Mxp = maxilliped; Gn 1 first gnathopod small, Gn 1ʹ enlarged.

Figure 27. Parametopa gorea n. sp. male, Senegal: Gn 2 = gnathopod 2 complete and only propodus; P 3–7 peraeopods 3–7; Ep 3 = epimeral plate 3; Us = urosome; U 1, 2, 3 = uropod 1, 2, 3; T = telson.