Diamysis mesohalobia Ariani & Wittmann, 2000

Figs 14, 15

Diagnosis (sensu lato: covering the three currently known subspecies). Appendix masculina 80–120% the length of terminal segment of antennular peduncle (Fig. 14 B). Eyes normal; eyestalks with fenestra paracornealis weakly developed (Fig. 15 K) or absent (Fig. 15 A), in any case mostly not or poorly visible. Distal segment of maxillary palpus with 4–27 distinct denticles. Presence of fringes on male carapace varies between subspecies; no such fringes in females. Basal segment of thoracic exopods with outer corner spiniform or less frequently ending in an acute edge, occasionally rounded in the first and/or in some of the median and/or posterior exopods. All pereiopods with normal carpopropodus and slender, styliform claw (Figs 14 E, 15B, M). Carpopropodus of thoracic endopods 3–8 with 3 (2; 4), 3–2 (4), 3–2, 2–3, 2–3 and 3–2 segments, respectively. Carpopropodus of endopod 3, if 3- segmented, with basal segment not longer than remaining segments combined (Fig. 15 M). Thoracic endopod 3 and often also endopod 8 with at least one among the four paradactylar setae distally pectinate in (most) females, smooth or pectinate in males. Male pleopod 4 biramous with 2-segmented sympod and with small, 2-segmented endopod (Figs 14 H, 15N); its exopod 2–(3)-segmented, with large modified seta at tip. This exopod with basal segment bearing a smaller smooth seta (Figs 14 H, 15D), in certain populations occasionally with an additional barbed seta (Fig. 15 N). Endopod of uropod with one strong spine below statocyst, statolith composed of vaterite. Telson subquadrangular (Fig. 15 S) to subtriangular (Fig. 15 J); maximum width is 1.4–3.0 times that at apex; its apical cleft with 8–39 laminae; cleft is 5–26% telson length.

Taxonomy. Interbreeding experiments by Ariani & Wittmann (2000) indicated mutual crossability between morphologically different Mediterranean populations of D. mesohalobia . The three main morphotypes distinguished were, therefore, described at subspecific level as D. mesohalobia mesohalobia Ariani & Wittmann, 2000, D. mesohalobia gracilipes Ariani & Wittmann, 2000, and D. mesohalobia heterandra Ariani & Wittmann, 2000; each of these subspecies are treated in separate subchapters below.

Occurrence (Fig. 16). Marine, brackish and fresh (near)-coastal waters of the E-Mediterranean and Marmora Seas.