CONICET | Buscador de Institutos y Recursos Humanos

Ostracoda are small, bivalved crustaceans that abound in all types of water bodies, marine and non-marine; some species even occur in phytotelmic environments. Phytotelmata are plant structures that hold water, such as tree holes, flowers, husks or leaf brackets. These water bodies are completely rain dependent and often contain communities of highly specialised aquatic invertebrates (Kitching 2000). There are several species of Bromeliacea (a group of terrestrial and epiphytic perennial plants) that are widespread from Argentina to Florida, and with one representative in Africa.As a consequence of their architecture, bromeliads provide high quality living space in the form of humus and moisture for diverse biota (Benzing 2000). The material was collected on September 26th, in 2009 from Aechmea distichantha (Bromeliacea) in the northeast of Argentina. Fluid contents of plants were extracted with a pipette attached to a lift pump. Ostracods were sorted under a binocular microscope and preserved in 70% ethanol. Specimens were dissected with valves stored dry in micropaleontological slides and with soft parts in glycerine in sealed slides. Drawings of soft parts were made with a camera lucida with a compound microscope (Olympus, BX51 at RBINS, Brussels). Valves were illustrated and measured using scanning electron microscopy (Philips XL30 SEM at RBINS, Brussels).The new species characterized by the medium to large sized of the carapace (> 0.7 mm) with a mark dimorphism. Females larger than males, with posterior part expanded into a brood pouch. In lateral view carapace elongated with left valve overlapping right valve in both anterior and posterior margins. Surface of carapace smooth with a few hairs. A2 dimorphic, the terminal segment of male with a stong serrated claw. Mandibular coxal with 8 strong cuspated teeth. Second and third maxillular endites with two setae and two spatulated claws each; palp not segmented, tapering, with 2 apical setae. Hemipenis with distal lobe triangular, with a pointed tip and with a finger-like projection at the base of the internal margin, dorsal seta present near the basis of the distal lobe; Lower Ramus present and shaped in a claspering process, copulatory process thick. There are eight species within the genus Elpidium: Elpidium bromeliarum O.F. Muller, 1880. Elpidium inaequivalvis Danielopol, 1981. Elpidium laesslei (Tressler, 1956). Elpidium maricaoensis (Tressler, 1941). Elpidium pintoi Danielopol, 1981. Elpidium purperae Danielopol, 1981. Elpidium merendonense Pinto, 2013. Elpidium martensi Danielopol, 2014, all of them cited for the Neotropical Region. Two of these, namely E. maricaoensis and E. laesslei, are known only from incomplete original descriptions and without records of males, whose reproductive structures bear the most important diagnostic features for identification. Elpidium sp. nov. resembles E. martensi, E. bromeliarum and E. pintoi Danielopol because of the similar cordiform shape and the size of the carapace, althought the three species have a very different morphology of the hemipenis. In E. martensi the right valve overlaps the left valve and the hemipenis is lancet-shaped and with a bright basis (that is also peculiar in E. pintoi) Most of the other Elpidium species have distal lobes provided with a ventral digitiform projection. Elpidium sp. nov. differs from E. purperae in the shape of carapace. The right valve overlaps the left one in lateral view. These two species also have differences in the shape of the hemipenis. In E. purperae the hemipenis has an elongated distal lobe and without digitiform protrusion. Elpidium sp. nov. differs from E. laesslei in the carapace ornamentation wich is pitted and has cosnpicuous fossae. Elpidium sp. nov. is different from E. inequivalvis and E. meredonense in the shape of the carapace. In the two species valves are really asymmetric. In E. meredonense there is a unique outgrowth at the posterior end of the left valve where it overlaps the right valve. This is the first record of the genus Elpidium in Argentina (Martens and Behen 1994).