Stenula peltata, Smith, 1872

Krapp-Schickel, Traudl & Vader, Wim, 2015, Stenothoids living with or on other animals (Crustacea, Amphipoda), Zoosystematics and Evolution 91 (2), pp. 215-246 : 218

Taxon classification Animalia Amphipoda Stenothoidae

? Stenula peltata (Smith, 1872) Figures 11, 12, 13

? Stenula peltata Smith 1872 in: Smith and Harger 1872: 29, pl. 3, fig. 5-8; Della Valle 1893: 570; Stebbing 1906: 194-195.

Stenula peltata ? synonymous to Gurjanova 1948: 310 Stenula ratmanovi

Type locality.

St. George’s Banks, 55 m depth. Near Cultivator Shoal.

Material examined.

one specimen USNM 35636, 41.5557 N, 68.1641 W, NA, 30 fathoms, sandy bottom, 29/8/1872.

As the original paper is not easily accessible and as there is some confusion about the authors, I repeat herewith the type-description by Smith:

Description.

Female. Eyes round and nearly white in alcohol. Antennulae (=A1) considerably shorter than epimera of the 4th segment (Cx 4); first article of the peduncle stout, subequal to head, the second shorter, the third very short and similar to the arts of the flagellum; flagellum scarcely longer than the peduncle, with 8 arts. Antennae (=A 2) slightly longer than antennulae; peduncle art 4, 5 about equal in length; flagellum subequal to flagellum of antennulae. Cx 2 (fig. 5) nearly ovate, twice as high as broad; Cx 3 somewhat rectangular, not wider than the second but considerably deeper; Cx 4 (fig. 6) very large, slightly deeper than Cx 3 and 1/3-1/4 longer than deep, being about as long as the first five segments of the thorax, the inferior margin regularly curved and the posterior convex in outline. Gn 1 (fig. 7) small and slender; merus triangular and distally broader than the carpus, which is not quite twice as long as broad and has the lateral margins parallel; propodus narrower but slightly longer than the carpus and narrowed distally; dactylus about half as long as the propodus. Gn 2 (Fig. 5) stouter; merus short triangular, carpus much broader than long and only slightly produced beneath the propodus; propodus about as long as the breadth of Cx 2, nearly twice as long as broad; palmar margin (Fig. 8) convex in outline, slightly oblique, with an acute lobe and a spine at the posterior angle, within which the top of the dactylus closes. P 4, 5 slender and nearly naked, P 5 basis slender, four times as long as broad, not wider than the merus. P 6, 7 slightly shorter than P 5, basis posteriorly dilated and squamiform in both pairs, but broader in P 7. U 3 ramus slightly longer than the peduncle.

Length of largest specimen, from front of head to tip of telson, about 6 mm.

The mandibles are without palp or molar tubercles, and in all other characters the species agrees with the genus Stenothoe as restricted by Boeck, but it seems to be very distinct from either of the European species.

Discussion.

The hint after the original description, that this species should belong to Stenothoe as it has no mandible palp, was not convincing: no Stenothoe is described from the region off Massachusetts or Connecticut, nor from the entire Atlantic, with gnathopods similar to the ones illustrated.

The incomplete illustrations of Stenothoe ratmanovi (Gurjanova, 1948) are very similar to what little we know about? Stenothoe peltata , and the two species may well be synonymous, in spite of the large geographic distance between the type localities. In that case the older name Stenula peltata (Smith, 1874) would become the valid name of the taxon.

We hoped to get more information by studying the single type specimen (see Fig. 11, 12) and illustrate here all what we could see; but there were no mouthparts except the maxilliped, and we still don’t know anything about the shape of the mandibular palp.

A sample in the collections of the Smithsonian Inst. (Washington) raised new hope to shed light in this situation: there could exist a Stenula sp. from the coelenteron of Haliactis arctica . Will this be Stenula peltata ?