The transition from an Epigean to a Hypogean mode of life: Morphological and Bionomical characteristics of Diamysis Camassai sp. nov.(Mysidacea, Mysidae) from Brackish-Water Dolinas in Apulia, SE-Italy

A new representative of the mainly Mediterranean and Pontocaspian genus Diamysis Czerniavsky is described from a system of brackish-water dolinas near the Ionian coast of southern Italy (eastern Mediterranean). Most life stages mainly dwell in microalgal beds on hard substrata or among macrophytes inside well-illuminated dolinas, whereas incubating females and neonates are relatively more abundant in dimly-lit or dark dolinas. D. camassai sp. nov. is distinguished from its congeners by a relatively small cornea and short eyestalks with larger scales at their basis, as well as by a complex of characters affecting the carpopropodus of the thoracic endopods and the exopod of the male fourth pleopod. Relatively small eyes, dense setation on the legs, and large eggs point to a certain degree of adaptation to a subterranean mode of life, albeit that the animals are strongly pigmented and essentially micro-herbivorous. The stygophilic characteristics of this Diamysis may represent an important intermediate stage in the evolution towards stygobionts, which occur in the closely related genera Troglomysis Stammer (Mediterranean) and Antromysis Creaser (Caribbean).