Diamysis Czerniavsky, 1882

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 : 27-28

Genus Diamysis Czerniavsky, 1882

Figs 13–15 , 17

Short diagnosis (modified from Wittmann & Ariani (2012a)). Diamysini with eyes normal. Antennal scale setose all around, with small apical segment (<= 20% scale length) surrounded by five plumose setae in both sexes ( Figs 13 A, D, E, 14A, 15A, K, 17A, K). Carapace with a pair of post-suborbital spines ( Figs 13 A, B, D, F, 14A, C, 15K, L, 17A). Carapace of females always without fringes, whereas potential presence of fringes ( Figs 13 B, 15L) is species-specific in males. Thoracic endopods 3–8 normal, with 2–4-segmented carpopropodus, dactylus small, with distinct claw ( Figs 14 E, 15B, M, 17D, L). All female pleopods and male pleopods 1, 2, 5 reduced to setose rods. Male pleopod 3 reduced to well-developed, 2-segmented sympod terminally fused with its small, setose, unsegmented endopod, exopod missing ( Figs 13 C, 14G). Male pleopod 4 biramous with 2-segmented sympod, with small, 1–2-segmented endopod, and with moderately long, rod-like, 2–3-segmented exopod bearing a modified, strong seta at tip ( Figs 13 G, 14H, 15D, E, N, 17E, N); the apical seta is much longer than any other seta on male pleopod 4. Endopod of uropod setose all around, with one (exceptionally two) spines below statocyst. Telson with superficial to deep apical incision; with spines on each lateral margin, these margins ending in a pair of larger, posteriorly directed apical spines; cleft lined by many laminae ( Figs 13 H, 14N, 15J, S, 17J, Q).

Type species. Mysis bahirensis G. O. Sars, 1877 , by subjective monotypy upon definition of the genus Diamysis by Czerniavsky (1882a, 1887: 84).

Taxonomy. Interbreeding experiments by Ariani & Wittmann (2000) indicate failure of mutual interbreeding between the topotypical population of Diamysis bahirensis ( G. O. Sars, 1877) from the El Bahira lagoon at the coast of Tunisia and a number of other Mediterranean populations of its genus. This and morphological differences point to a specific status of D. mesohalobia Ariani & Wittmann, 2000 , and D. lagunaris Ariani & Wittmann, 2000 .

Distribution. Tropical to temperate waters of the E-Atlantic, Mediterranean, Pontocaspian, and W-Indian Ocean. Greatest species diversity in the Mediterranean ( Figs 6 , 12 , 16 ). In coastal to continental waters, mostly in brackish waters, also marine, comparatively high diversity in fresh-water. Among the 14 species plus two nonnominotypical subspecies so far known, Diamysis pengoi (Czerniavsky, 1882) , D. lacustris Băcescu, 1940 , and D.

fluviatilis Wittmann & Ariani, 2012 , are mainly found in fresh-water; whereas D. mesohalobia heterandra Ariani & Wittmann, 2000 , is an essentially brackish-water taxon ( Fig. 16 ), also found in fresh-water ( Fig. 12 ).

Bionomy. In D. lagunaris and in two subspecies of D. mesohalobia , the survival of brood pouch larvae was higher under mesohaline than euhaline conditions in the laboratory (Ariani & Wittmann 2000). Based on this, along with biomineralogical and morphological similarities of the statoliths with fossil ones from Miocene deposits of the brackish Paratethys, Ariani & Wittmann (2000) suggested a brackish-water origin of Diamysis , even of (mixo)euhalobious forms that may have returned to the sea from low-salinity environments.

Remarks. Exhaustive data on D. lagunaris , D. lacustris , D. mesohalobia heterandra , and D. fluviatilis , are available in Wittmann & Ariani (2012a, 2012b). Data necessary for determination are given in Figs 13–15 , 17 . Additional remarks are in the ‘Discussion’.

Figures

FIGURE 6. Distribution of Diamysis hebraica Almeida Prado-Por, 1981, D. lagunaris Ariani & Wittmann, 2000, and Paramysis kosswigi Băcescu, 1948, in tributaries and coastal waters of the Mediterranean Sea. Data are original and from Băcescu (1948, 1954), Almeida Prado-Por (1981), Ariani & Wittmann (2000), Kocataş et al. (2003), and Wittmann & Ariani (2011, 2012 a).

FIGURE 12. Distribution of five species of Mysinae (Mysidae) in tributaries and coastal waters of the Adriatic Sea. In part modified from Wittmann & Ariani (2012 b).

FIGURE 13. Diamysis fluviatilis Wittmann & Ariani, 2012 (A – C), and D. lacustris Băcescu, 1940 (D – H). Materials from the Sile River (A – C) and Lake Scutari (D – H). A, cephalic region of female with body length 8.9 mm, dorsal; B, carapace expanded on slide, male 9.5 mm, dorsal; C, third pleopod of male 6.6 mm, rostral aspect; D, male with body length 5.2 mm, lateral view; E, cephalic region of female 8.0 mm, dorsal; F, carapace expanded on slide, dorsal, same male as in (D); G, fourth pleopod of same male, rostral; H, telson of same male, dorsal. B, F, pores on carapaces not to scale. From Wittmann & Ariani (2012 b).

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.

FIGURE 17. Diamysis lagunaris Ariani & Wittmann, 2000 (A – J), and D. hebraica Almeida Prado-Por, 1981 (K – Q). Materials from Lago di Caprolace (paratypes: A, C – E, G, J, Lazio coast of Tyrrhenian Sea), Étang de La Palme (B, Golfe du Lion, Mediterranean coast of France), coast of La Spezia (F, N-Tyrrhenian Sea), Lago di Ganzirri (H, Strait of Messina, Tyrrhenian Sea), and the coastal stream Nahal Tanninim (K – Q, Levantine Sea, coast of Israel). A, anterior body region of male with body length 5.6 mm, dorsal view on cephalothorax; B, eyes and anterior margin of carapace in female 5.3 mm, dorsal; C, exopod of first thoracopod in male 4.0 mm, caudal; D, tarsus (i. e. carpopropodus plus dactylus) of third thoracic endopod in female 6.1 mm, rostral; E, fourth pleopod of male 4.8 mm, rostral; F – H, posterior margin of sixth pleonite in females with 7.2 mm (F), 5.2 mm (G), or 5.1 mm (H) body length, lateral; J, telson of male 4.8 mm, dorsal; K, anterior body region of male 5.0 mm, dorsal view on cephalothorax; L, tarsus of third thoracic endopod, male 5.0 mm, rostral; M, exopod of sixth thoracopod in male 4.0 mm (paratype), rostral; N, exopod of fourth pleopod of male 5.0 mm, rostral; O, posterior margin of sixth pleonite, male 4.0 mm (paratype), lateral; P, the same for female 4.0 mm (holotype); Q, telson of male 5.0 mm, dorsal. A, K, pores on carapaces not to scale; A – J, from Ariani & Wittmann (2000); K – Q, original.