Ariani, A.P.; Wittmann, K.J. (2000). Interbreeding versus morphological and ecological differentiation in Mediterranean Diamysis (Crustacea, Mysidacea), with description of four new taxa. Hydrobiologia. 441: 185-236.

150233

Ariani, A.P.; Wittmann, K.J.

2000

441: 185-236

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NeMys doc_id: 3619

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Hybridization experiments in the laboratory, performed until the F1 free-living juvenile stage, showed failure of embryonic development in crossbreedings between certain populations of mysids from meso- to metahaline waters of the Mediterranean that were previously lumped together under the name Diamysis bahirensis (G. O. Sars). Western Mediterranean populations did not successfully crossbreed with those from the eastern basin and vice versa. This is consistent with the W-E morphological differentiation in this genus and with different salinity affinities of the western as compared to the eastern forms. From the study of type material, the diagnosis of D. bahirensis is redefined to populations in the SW-Mediterranean showing large spiniform projections of the sixth pleonite, flanking the telson, and numerous small fringes on the posterior margin of the male carapace. Crossbreeding was unsuccessful with populations of D. mesohalobia n. sp. in the E-Mediterranean, which show smooth posterior margin of the carapace in both sexes and distally pectinate paradactylary setae on certain pereiopods, at least in females. Within this species, three morphotypes with different salinity affinities in nature are distinguished; as they showed successful laboratory interbreeding under mesohaline conditions, the taxa, therefore, are defined at subspecific level (D. mesohalobia mesohalobia, D. mesohalobia gracilipes n. ssp., D. mesohalobia heterandra n. ssp.). Populations of these three subspecies failed to crossbreed with a W-Mediterranean (NE-Tyrrhenian) population of D. lagunaris n. sp., which is characterized by a smooth carapace in both sexes, cuticular ’windows‘ on the eyestalks, and rounded projections of the sixth pleonite. In D. lagunaris, D. mesohalobia mesohalobia and D. mesohalobia gracilipes, survival of brood pouch larvae in the laboratory was higher under mesohaline compared with euhaline conditions. This along with biomineralogical and morphological similarities of the statoliths with fossil repr esentatives from Miocene deposits of the brackish Paratethys, suggest a brackish water origin, even in euhalobiontic forms that may have immigrated into the sea from low salinity environments. A key to the 10 species and two subspecies in this genus is given.

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