Orchestia mediterranea Costa, 1853

Myers, Alan A. & Lowry, James K., 2020, A revision of the genus Orchestia Leach, 1814 with the reinstatement of O. inaequalipes (K. H. Barnard, 1951), the designation of a neotype for Orchestia gammarellus (Pallas 1776) and the description of three new species (Crustacea: Amphipoda: Talitridae Talitrinae), Zootaxa 4808 (2), pp. 201-250 : 231-234

Orchestia mediterranea Costa, 1853

( Figs 23–25 )

Orchestia mediterranea A. Costa, 1853: 171 .― Spence Bate & Westwood, 1861: 27.― Heller, 1866: 4, pl. 1, fig. 7.― Scott, 1899: 264, pl. 13, figs 9–11.―? Spandl, 1923: 59 (only record from the Red Sea).― Chevreux & Fage, 1925: 273, fig. 283.― Williamson, 1951: 63, fig. 1a.― Bulycheva, 1957: 154, fig. 55.―G. Karaman, 1970: 18, pl. 5, pl. 6, fig. 43.―Lin- coln, 1979: 218, figs 96c, 100a–l.― Bellan-Santini, 1993: 746, fig. 512.― Conceição et al., 1998: 226, fig. 1, 227, table 1, 228, table 3, 229, table 4, 5, 230, fig. 2 (genetics).― Pavesi & Ketmaier, 2013: 892, tables 1, 2.

Orchestia trigonocheius Spence Bate, 1862: 26 , pl. 4, fig. 6.

Orchestia chilensis Della Valle, 1893 (partim: 498, pl. 2, fig. 8; pl. 15, figs 31–38).

Type locality. Napoli , Italy .

Description of adult male (18 mm).

Head. Eyes of moderate size. Antenna 1 short, not reaching end of peduncular article 4 of antenna 2; accessory flagellum absent; primary flagellum with 6–7 articles. Antenna 2 peduncular article 5 1.4 × length of peduncular article 4; flagellum longer than combined length of peduncular articles 4 and 5, with about 18 articles, final article cone shaped, with terminal cluster of imbricated setae. Labrum without epistome. Mandible left lacinia mobilis with 4 cusps. Maxilliped palp article 2 with distomedial lobe.

Pereon. Gnathopod 1 subchelate, coxa smaller than that of coxa 2; posterior margin of carpus and propodus each with lobe covered in palmate setae; propodus length to carpus length 1:1.4; propodus subtriangular; dactylus shorter than palm. Gnathopod 2 subchelate. basis 2.0 as long as broad; merus posterior margin with 3 robust setae; propodus pyriform, palm very oblique. Pereopods 3–7 cuspidactylate. Pereopods 3–4 dactylus relatively short and stout. Peropod 4 dactylus thickened proximally with a notch midway along posterior margin. Pereopod 5 basis subovoid. Pereopod 6 subequal in length with pereopod 7. Pereopod 7 basis posterior margin weakly serrate; merus strongly triangular, 2.2 × as wide distally as proximally; carpus irregular, anterior margin strongly and evenly convex, posterior margin straight, notched; carpus and merus subequal in length; propodus about 1.4 × length of carpus.

Pleon. Epimeron 3 posterior margin weakly crenulate. Uropod 1 peduncle much longer than rami, without distolateral robust seta; rami subequal. Uropod 2 peduncle a little shorter than rami, rami, rami subequal; exopod with 2 marginal robust setae; endopod with 2 marginal robust setae. Uropod 3 peduncle only a little longer than broad; ramus 2.2 × as long as broad about half length of peduncle, outer margin with two small robust setae. Telson with 7– 8 marginal and apical robust setae.

Female (sexually dimorphic characters). Gnathopod 2 mitten-shaped, basis 1.9× as long as broad, convex proximally, weakly concave distally; carpus 1.7 × length of propodus. Pereopod 7 slender, merus and carpus unexpanded.

Habitat. Amongst decaying weed including Posidonia oceanica debris high on the shore.

Remarks. Orchestia mediterranea resembles O. magnifica and O. aestuarensis in the extremely acute palm and absence of a proximal lobe on the male gnathopod 2 propodus and by the irregular posterior margin of the pereopod 7 carpus. It differs from O. magnifica in the uropod 3 ramus margin being naked or bearing a single small seta, whereas in O. magnifica the ramus has five strong marginal robust setae. It differs from O. aestuarensis in the relatively short, stout dactyls of pereopods 3–7 (elongate and slender in O. aestuarensis ).

In the notched margins of the male pereopod 7 carpus, O. mediterreanea resembles O. montagui , however, in O. mediterreanea , the posterior margin of the carpus abruptly narrows abruptly distally, whereas in O. montagui the carpus evenly narrows distally. Orchestia mediterranea differs from O. gammarellus in the evenly convex dactylus of the male gnathopod 2 (strongly falcate in O. montagui ) as well as in the strongly oblique palm of the male ganthopod 2 (weakly oblique in O. montagui ).

Distribution. British Isles: Great Cumbrae Island in the Firth of Clyde (55°44’N, 4°54’W) ( Spicer & Taylor, 1986).

Mediterranean: France: étang de Canet (Charniaux-Legrand 195l); Sète; étang de Berre; La Ciotat ( Chevreux 1911); Isle des Embiez ( Bellan-Santini 1993); Saint-Tropez; Villefranche-sur-Mer. Corsica ( Chevreux 1911). Sardinia: Cagliari (? Ruffo 1938).

Italy-Tyrrhenian Sea: Napoli ( Della Valle 1893); Gargano ( Ruffo 1948). Sicily: Egadi; Pachino ( Bellan-Santini

1993). Italy-Adriatic Sea: Civitanova Marche (Cechini 1928); Lago di Verano, Gargano, Lago Verano River ( Ruffo

1948); Venezia (? Brian 1939 Giordani-Soika 1950); Timavo (? Stammer 1932); Duino (? Stammer 1932); Trieste

( Nebeski 1880). Y ugoslavia: Krk; Split (G. Karaman 1971); Vis; Hvar; Korcula; Lastovo ( Heller 1866). Greece: Rodhos ( Bellan-Santini 1993). Black Sea ( Sezgin et al. 2001, Sezgin & Kataðan 2007). Morocco: Bou Regreg (El Kaïm et al. 1985)

Algeria: Annaba; Rherchell (Chevreux 191l).

Tunisia: Iles Kerkenah ( Elkaïm 1985 et al.), Bizerte Lagoon (? Jelassi et al. 2012); northern Tunisian wetlands, 40 sites (? Khemaissia et al. 2017).

Egypt: Port Said (? Ruffo 1938).

Figures

FIGURE 23. Orchestia mediterranea Costa, 1857, Napoli (redrawn from Bellan-Santini 1993 and Adriatic, Karaman 1970).

FIGURE 24. Orchestia mediterranea Costa, 1857, Napoli (redrawn from Bellan-Santini 1993 and Adriatic, Karaman 1970).

FIGURE 25. Orchestia mediterranea Costa, 1857, Napoli (redrawn from Bellan-Santini 1993 and Adriatic, Karaman 1970).