Stenothoe valida Dana 1852
Creators: name: Krapp-Schickel, Traudl
Publisher: name: Zenodo
Year: 2015
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Amphipoda
Stenothoidae
Stenothoe
Stenothoe valida
Stenothoe validus

description: Stenothoe valida Dana, 1852
(Figures 21–23)
S. validus Dana 1852: 311; Dana 1853: 924–925, pl. 63 fig. 1a–o.
Type locality
Rio de Janeiro.
Material examined
Nearly 200 spec. Hamilton Parish, Harrington Sound, behind Bermuda Aquarium, from hydroids 2/VI/1987; YPM IZ 20392.
Male 4.5 mm from Gorée (Senegal), calcareous algae, 25/04/1953, slide MVRCr 7675.
Female 4 mm from Gorée (Senegal), calcareous algae, 25/04/1953, slide MVRCr 7676.
? male 2 mm, fem. 3 mm Bonaire, Kralendijk near Pasanggrahan, 03–05/09/1930 NBCL (PWH).
? male 3 mm Venezuela 1202 (between Aruba and Blanquila), mud without rock debris, mud, summer 1936, NBCL (PWH).? fem. ov. 4 mm Barbados, Caribbean Sea without any details. NBCL (PWH).? fem. ov. 3.5 mm, E- China Sea 25° 28 ʹ N, 120° 29 ʹ E, NBCL (PWH).? male 3 mm, harbour of Havelok, Andaman Islands, Bay of Bengal; coralligène, 1–8 m depth; coll. Ulrich Schiecke 22. XII.1978, slide MVRCr 7682.? Two fem. ov. 3 mm, same locality, slide MVRCr 7708, 7709.
Remarks
Two characters are quite helpful for the determination: the widened and extremely lengthened merus of P 6, P 7 reaching the end of carpus, and male Cx 3 with margins not parallel, but rather triangular or even trapezium-shaped, not very different from Cx 4, while females have a rectangular Cx 3 like all other Stenothoe members. The first character is repeated everywhere in the literature, but the second one is barely described, though illustrated in Chevreux (1935, pl. 16), Barnard (1953, pl. 15; 1970, fig. 165) and Krapp-Schickel (1976, fig. 21).
The information about the length varies from ‘3–4 lines’ given in the description by Dana, 1853 (meaning about 30–40% of an inch probably, thus up to 7.5–8 mm), 5–6 mm in Chevreux and Fage, 1925, up to 8 mm in Lincoln 1979, 5– 6 mm in Krapp- Schickel 1993.
Also Reid (1951, p. 231, fig. 28) found S. valida in his samples, besides material of S. senegalensis n. sp.
Three differences to the original description of S. valida Dana are (1) very large round dark-pigmented eyes; (2) the body length (here 3–4.5 mm; in S. valida the original description reports ‘3–4 lines’, which means up to 7.5–8 mm); and (3) the shape of Gn 2 female. For this last character, Dana (1853, p. 924) writes: ‘palm nearly straight’, and the margins of propodus and dactylus are densely beset with setae like in male; here Gn 2 propodus hind margin is regularly rounded, the propodus is medially the widest and shows a triangular hump. But all this variation could depend on allometry.
Not only in the samples of Reid, but also in the material studied here from Senegal, the two stenothoids S. senegalensis n. sp. and S. valida were living together. For distinguishing them it is helpful to look at the following characters: ovigerous females of S. senegalensis less than 3 mm, in S. valida more than 3 mm; U 3 male in S. senegalensis uncinate, in S. valida always straight; U 2 in S. senegalensis with subequal rami, in S. valida rami clearly unequal; Gn 2 female in S. senegalensis with rounded and smooth palmar margin, in S. valida with triangular hump or more elevations near dactylus insertion; eyes in S. senegalensis of normal size, in S. valida large and dark pigmented; P 7 in S. senegalensis basis always longer than wide, in S. valida strongly widened, merus in S. senegalensis never reaching carpus, in S. valida much widened, lengthened and usually reaching carpus.
Three specimens found at the Andaman Islands fit quite well the description of the morphology of S. valida; however, they are only about 3 mm and P 6, 7 basis is still wider; Gn 2 propodus of ovigerous females has a slightly different shape, not being widest in the middle, but towards the proximal end. But the three specimens are too few for judging if these character states are stable or variable.
I have the strong suspicion that not only has Stenothoe gallensis erroneously been called cosmopolitan, but Stenothoe valida too may well be a group of morphologically extremely similar species living in different regions of the world. I give here all the citations I know about this species, ordered by geographical region. Maybe they can be helpful in this ‘detective’ task.
(1) Mediterranean and Atlantic Ocean:
Dana (1852, p. 311; 1853, p. 924, pl. 63); Bate (1862, p. 60–61, pl. 9, fig. 6); Stossich (1880, p. 246); Carus (1885, p. 407); Della Valle (1893, p. 566–568, pl. 58, figs. 74–78); Graeffe (1902, p. 22); Stebbing (1906, p. 194); Chevreux (1908, p. 4–8, figs. 4–6 (S. assimilis); 1913, p. 2–3; 1935, p. 81–84, p. 16, figs. 7, 12, 30, t. 16); Walker (1910a, p. 621–622, fig. 1; 1910c, p. 31–32); Chevreux and Fage (1925, p. 138, fig. 137); Giordani- Soika (1949, p. 187–188); Spooner (1950, p. 249–250); Barnard (1953, p. 83–84, fig. 15; 1970, p. 250–251, fig. 165); Krapp-Schickel (1976, p. 24–27, fig. 19–21; 1993, p. 706–708, fig. 485); Ledoyer (1977, p. 409); Diviacco (1979, p. 96, t. 1); Lincoln (1979, p. 198, fig. 90); Diviacco (1983, p. 89–91, fig. 3, t. 1).
(2) South Africa:
K.H. Barnard (1925, p. 345–346); Griffiths (1974a, p. 200, 202; 1974b, p. 252; 1975, p. 168).
(3) Australia– New Zealand:
Chilton (1924, p. 270); Hale (1927, p. 314, fig. 3); Barnard (1972b, p. 158; 1974, p. 129).
(4) Pacific Ocean:
J.L. Barnard (1953, p. 83–87, pl. 15; 1959, p. 21; 1961, p. 178; 1964, p. 105; 1971, p. 122).
(5) Indian Ocean:
Schellenberg (1928, p. 641); Ledoyer (1967, p. 125, fig. 4b; 1979, p. 133; 1986, p. 975–977, fig. 385); Sivakrakasam (1969, p. 373–376, figs. 2A, B).
Distribution
Until now seen as cosmopolitan, which is questionable.
Here follow some other members of Stenothoe for clearing up discovered taxonomic problems or streamlining the species’ distinctions.
description: Published as part of 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), pp. 2309-2377 in Journal of Natural History 49 (37) on pages 2348-2353, DOI: 10.1080/00222933.2015.1021873, http://zenodo.org/record/4000077