Diamysis mesohalobia mesohalobia Ariani & Wittmann, 2000

Fig. 14

Diamysis bahirensis: W. M. Tattersall 1927; Ariani 1966 (partim), 1979 (partim), 1981a (partim); Ariani et al. 1981, 1982, 1983, 1993 (partim); De Matthaeis et al. 1982 (partim); Wittmann et al. 1990, 1993 (partim); Schlacher et al. 1992.

Diamysis bahirensis ssp.: Ariani 1981b (partim).

Diamysis sp.: Wittmann & Stagl, 1996 (partim); Ariani et al. 1999.

Diamysis sp. A: Wittmann 1999.

Diamysis mesohalobia Ariani & Wittmann, 2000: 2002, 2004; Ariani et al. 2000; Petrescu & Wittmann 2009; San Vicente 2010; Daneliya & Petryashev 2011; ITIS 2014.

Diamysis mesohalobia mesohalobia Ariani & Wittmann, 2000: 2005; Kocataş et al. 2003; Ariani 2004; Özbek et al. 2004; Remerie et al. 2004; Özbek & Ustaoğlu 2006; Anderson 2008; Wittmann & Ariani 2010; Mees 2014.

Material examined. 84 samples from mesohaline to mixoeuhaline coastal waters of the Adriatic, Aegean and Levantine Seas (Ariani & Wittmann 2000). Previously unpublished sample: 93 F ad. 5.5–7.1 mm, 223 M ad. 4.3– 6.3 mm, 22 subad., 56 imm., 112 juv., karstic spring with small salinity fluctuations, Fiume Piccolo, near Torre Canne, Adriatic coast of southern Italy, 40.8275N 017.4818E, 2–3 m depth, striped with hand net from brown algae, S = 15 , pH 7, 18.5°C, 29 Nov. 2011, leg. A. P. Ariani. One specimen of this sample reminds of a gynandromorph of the 'fore and aft' type (Hollingsworth 1960): with pleopods as typical for adult males, but antennula without appendix masculina and also without plumose setae typical of males or females.

Short updated description. The following data cover primarily the type population in the mesohaline spring Fiume Morello (Apulia, Adriatic Sea). Data from remaining populations, as far as different, are given in square brackets.

Diamysis mesohalobia with short rostrum forming a wide convex angle with rounded tip (Figs 14 A, C). Fenestra paracornealis poorly developed, rarely visible. Carapace without fringes (Fig. 14 C) in both sexes. Palpus of maxilla with subcircular terminal segment, armed with 6–24 [5–24] denticles along distal margin. Basal segment of thoracic exopods with outer corner spiniform (Fig. 14 D), less frequently ending in an acute or rounded edge, especially in posterior exopods. Pereiopods relatively short, endopod 8, when stretched anteriorly, extending to basis of endopod 1 or at most up to maxillae [mandibles]. Pereiopods stout (Fig. 14 E) to moderately slender, with R6 = 4.4–6.1 [4.4–6.8]. Carpopropodus of thoracic endopods 3–8 with 3 (2), 3 (2), 3–2, 2–3, 2–3, and 3 (2) [3–2] segments, respectively. Thoracic endopod 3 with carpopropodus being longer than 5 times its maximum width; thoracic endopods 3–8 with long and slender claw. Penis with smooth setae only, arranged in a semicircle close to ejaculatory opening (Fig. 14 F). Male pleopod 4 biramous with 2-segmented exopod bearing a modified, strong seta at tip and a smaller, smooth seta subterminally on basal segment (Fig. 14 H). Scutellum paracaudale subtriangular, biconvex; tip pointed or less frequently rounded (Fig. 14 J–M). Telson subquadrangular (Fig. 14 N) [to subtriangular], 0.8–0.9 [0.7–1.0] times length of last abdominal somite; maximum width of telson is 1.6–2.0 [1.6– 3.0] times that at apex; lateral margins concave or rarely straight, armed with 7–12 [7–14] spines. Apical cleft of telson with convex (Fig. 14 N) or rarely straight margins, bottom of cleft rounded, cleft is 12–16% [9–16%] telson length, cleft lined by 15–39 [8–39] laminae.

Body length: Adult females 4.6–9.6 mm, males 4.1–7.7 mm.

Distribution (Fig. 16). Eastern Mediterranean only: in Adriatic, Aegean, and Levantine Seas. Mostly in mesohaline karstic springs with small salinity fluctuations, also in mesohaline to mixoeuhaline lagoons and estuaries. Predominantly in the salinity range 10–38, locally down to S = 2. Samples of this subspecies were taken by Özbek et al. (2004) in the Köyceğiz lagoon at the Aegean coast of Turkey. Data by Akin et al. (2005) and own measurements at the northern shore (S = 2.3 in 0.5–2 m, 10 June 2006) suggest that the positive station was most likely from the oligohaline range within this large, oligo- to metahaline lagoon with complex salinity patterns.