Diamysis Czerniavsky 1882
Creators: name: Wittmann, Karl J.
name: Ariani, Antonio P.
name: Daneliya, Mikhail
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Mysida
Mysidae
Diamysis

description: 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’.
description: Published as part of 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, pp. 1-70 in Zootaxa 4142 (1) on pages 27-28, DOI: 10.11646/zootaxa.4142.1.1, http://zenodo.org/record/261102