Estela Celia Lopretto

Anaspidacea, Bathynellacea (Crustacea, Syncarida), generalised tracks, and the biogeographical relationships of South America

The spatial evolution of South American Syncarida (Anaspidacea and Bathynellacea) and related taxa is evaluated applying a panbiogeographic approach, where Ocean basins are used to identify major patterns of intercontinental distribution. The Pacific basin, corresponding to a southern temperate track, is identified as the major evolutionary centre for Stygocaris(Stygocarididae), Bathynella (Bathynellidae), Atopobathynellu, and Chilibathynella (Parabathynellidae), whereas distribution of Nannobathynella (Bathynellidae) and Cteniobathynella (Parabathynellidae) is centred on the Atlantic Ocean, belonging to a northern tropical track. It is concluded that the biotic origin of the South American Syncarida is complex, implying the existence of at least two ancestral biotas.

Pelagostrobilidium wilberti n. sp. (Oligotrichea, Choreotrichida): Morphology and Morphogenesis

ABSTRACT. Morphology, infraciliature, morphogenetic features, and some ecological data for Pelagostrobilidium wilberti n. sp. are described. This new species was collected from a temporary pond in Magdalena, Buenos Aires province, Argentina, which was sampled monthly from August 2003 to July 2005. The species was found in autumn and winter. Observations were made in vivo and after staining with protargol. Pelagostrobilidium wilberti n. sp. measures 63–84 × 42–49 μm in vivo and is conical in shape, with a posterior spine‐like cytoplasmic process. It possesses 6 somatic kineties, with kinety 2 sinistrally curved and shorter than the others. The oral apparatus is composed of 25–32 external and two internal membranelles. The macronucleus is horseshoe‐shaped and located beneath the oral apparatus; two or three spherical micronuclei lie dorsally. There is a posterior contractile vacuole. Morphogenesis is hypo‐apokinetal and begins dorsally between the curved kinety 2 and kinety 3. After the discovery of this new species, the diagnosis of the genus Pelagostrobilidium was amended.

The genus Chlamydotheca Saussure (Crustacea: Ostracoda) in northeastern Argentina

The genus Chlamydotheca Saussure, 1858 is a typical representative of the Neotropical ostracod fauna that occupies lotic and lentic environments including temporary and permanent ponds. Up to the present, four species have been recorded in Argentina: C. iheringi (Sars), C. incisa (Claus) and C. leuckarti (Claus), and C. symmetrica (Vavra). Temporary and permanent ponds of this region were sampled for ostracods, using a fine mesh net. Three species belonging to the genus Chlamydotheca were collected of which C. arcuata (Sars) is recorded for first time for the Chacoan region. Limb morphology was studied under light microscope and line drawings were made using camera lucida. Valves were photographed under scanning electron microscope and redescriptions of C. arcuata and C. iheringi are provided and distributional aspects of the species sampled are discussed.

Description of Deviata rositae n. sp., a new ciliate species (Ciliophora, Stichotrichia) from Argentina

ABSTRACT. Soil samples were taken from a temporary pond located in Buenos Aires province, Argentina, during the dry phase in the summer of 2005. The ciliates were studied alive and after staining with protargol. Deviata rositae n. sp. measures 112–154 μm in length and 21–28 μm in width in vivo and has a vermiform body. The contractile vacuole is located in the mid‐body on the left. The macronucleus is moniliform and there are 1–3 micronuclei. The oral apparatus is composed of 14–18 adoral membranelles and straight paroral and endoral membranes that never intersect each other. The somatic ciliature is arranged in four frontal cirri, one buccal cirrus, six long and slightly spiraled rows of cirri with the first right row extending up to the equatorial or sub‐equatorial region, and two dorsal rows of dikinetids. This new species of Deviata primarily differs from its congeners by the number of macronuclear nodules and the number and disposition of the dorsal rows of dikinetids.