Diamysis mesohalobia Ariani & Wittmann, 2000

Wittmann, Karl J., Ariani, Antonio P. & Daneliya, Mikhail, 2016, The Mysidae (Crustacea: Peracarida: Mysida) in fresh and oligohaline waters of the Mediterranean. Taxonomy, biogeography, and bioinvasion, Zootaxa 4142 (1), pp. 1-70 : 29

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.

Figures

FIGURE 14. Diamysis mesohalobia mesohalobia Ariani & Wittmann, 2000, paratypes from the brackish spring Fiume Morello at the Adriatic coast of SE-Italy. A, dorsal aspect of male with body length 6.5 mm; B, antennula of male 6.3 mm, dorsal; C, carapace expanded on slide, male 6.0 mm, dorsal; D, exopod of first thoracopod, male 6.3 mm, caudal aspect; E, tarsus (i. e. carpopropodus plus dactylus) of fourth thoracic endopod, male 6.4 mm, rostral; F, right face of left penis, male 6.3 mm; G, third pleopod of same male, rostral; H, fourth pleopod of same male, rostral; J – M, posterior margin of sixth pleonite, lateral, in female 6.6 mm (J), female 6.8 mm (K), and two males, each with 6.3 mm (L, M); N, telson of male 6.3 mm, dorsal. A, C, pores on carapaces not to scale. A, B, D, E, G – N, modified from Ariani & Wittmann (2000); C, F, original.

FIGURE 15. Diamysis mesohalobia gracilipes Ariani & Wittmann, 2000 (A – J), and Diamysis mesohalobia heterandra Ariani & Wittmann, 2000 (K – S). Materials from Mar Piccolo in the Gulf of Tarent (paratypes: A – E, G – J, Ionian Sea), the Bay of Strunjan (F, Gulf of Trieste, NE-Adriatic Sea), Lake Deran (L, N, P – S, E-Adriatic), Limni Antinioti (K, M, Island of Corfu, Ionian Sea), and Lakes of Bacin (O, E-Adriatic). A, anterior body region of male with body length 7.2 mm, dorsal view on cephalothorax; B, tarsus (i. e. carpopropodus plus dactylus) of third thoracopod, male 6.5 mm, rostral; C, left face of right penis, male 7.2 mm; D, E, exopod of fourth pleopod, rostral, in males with 4.4 mm (D) or 6.5 mm (E) body length; F – H, posterior margins of sixth pleonite in female with 7.4 mm (F), in male with 7.2 mm (G), and in female with 4.8 mm (H) body length, lateral; J, telson of male 7.2 mm, dorsal; K, anterior body region of male 5.2 mm (paratype); L, carapace expanded on slide, dorsal, male 7.9 mm; M, tarsus of third thoracic endopod, rostral, male 5.2 mm (paratype); N, fourth pleopod of male 7.9 mm, rostral; O, P, exopod of fourth pleopod, rostral, in males with 5.5 mm (O) or 8.4 mm (P) body length; Q, R, posterior margins of sixth pleonite in female with 9.8 mm (Q) or in male with 6.0 mm (R) body length, lateral; S, telson of male 7.9 mm, dorsal. A, K, L, pores on carapaces not to scale. A, D, E, G – K, M, modified from Ariani & Wittmann (2000); L, N – S, modified from Wittmann & Ariani (2012 b); B, C, F, original.

FIGURE 16. Distribution of Limnomysis benedeni Czerniavsky, 1882, Neomysis integer (Leach, 1814), and the three subspecies of Diamysis mesohalobia Ariani & Wittmann, 2000, in tributaries and coastal waters of the Mediterranean and adjacent seas. Data original and from 79 literature sources.