Extremophile at a Glance: Ostracod Crustacean From a Chemoautotrophic Sulphidic Cave Ecosystem

Abstract

Sulphidic cave ecosystems are remarkable evolutionary hotspots that have witnessed adaptive radiation of their fauna represented by extremophile species having particular traits. Ostracods, a very old group of crustaceans, exhibit specific morphological and ecophysiological features that enable them to thrive in groundwater sulphidic environments. Herein, we report a peculiar new ostracod species Pseudocandona movilaensis sp. nov. thriving in the chemoautotrophic sulphidic groundwater ecosystem of Movile Cave (Romania). The new species displays a set of homoplastic features specific for unrelated stygobitic species, for e.g., triangular carapace in lateral view with reduced postero–dorsal part and simplification of limb chaetotaxy (i.e., loss of some claws and reduction of secondary male sex characteristics), driven by a convergent or parallel evolution during or after colonization of the groundwater realm. P. movilaensis sp. nov. thrives exclusively in sulphidic meso-thermal waters (21°C) with high concentrations of sulphides, methane, and ammonium. Based on the geometric morphometrics-based study of the carapace shape and molecular phylogenetic analyses based on the COI marker (mtDNA), we discuss the phylogenetic relationship and evolutionary implication for the new species to thrive in groundwater sulphidic groundwater environments.