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The Malacology Collection of the Museo de La Plata contains more 13,000 lots from various regions of Argentina and other South American countries. The Collection also includes 511 type lots. Among the oldest type specimens are a large series of marine gastropod from Patagonia which were studied by Fernando Lahille in 1895. He was one of the first's naturalists of the Museo de La Plata, and there between 1893 and 1899, he made several studies in zoology. During that time, he described three species and forty varieties of Volutidae. Herein, we compare Lahille's type specimens, label data, number, and specimen information to the original descriptions and illustrations of these taxa. Each taxon has been photographed in multiple views. This historic type material is entirely composed of shells. This work is the first of a series of photographic catalogues of type material from the Malacology Collection of the Invertebrate Division of Museo de La Plata. [ABSTRACT FROM AUTHOR]

This study describes euspermatogenesis and paraspermatogenesis in Adelomelon ancilla (Volutidae) and compares them with the same processes in other caenogastropods. Spermatogenesis in A. ancilla followed the general developmental pattern of caenogastropods. The pattern of nuclear condensation involves granular, fibrillar, lamellar and homogenous electron-dense phases. Acrosome development begins with the posteriorly located proacrosomal vesicle arising from the Golgi complex in euspermatids. The proacrosomal vesicle develops into a preattachment acrosome which, together with the Golgi body, later moves towards the apex of the nucleus. In the early stage of paraspermatogenesis, the pattern of chromatin distribution in dense patches, together with the cytoplasmatic characteristics of paraspermatogonia, allows the recognition of the apyrene line from the euspermatogonia. Later features, including the peripheral condensation of nuclear chromatin followed by nuclear invagination, the posterior breakdown into nuclear vesicles (‘caryomerites’), centriole multiplication and the synthesis of secretory products, are the most conspicuous changes in the process of paraspermatogenesis. [ABSTRACT FROM PUBLISHER]

The imposex incidence and TBT pollution were investigated along 4,700km of Argentinean coast, including city harbors and proximal zones without marine traffic. We analyzed 1805 individuals from 12 gastropod species, including families Volutidae, Muricidae, Nassariidea, Calyptraidae, Marginellidae, and Buccinidae, and found the imposex phenomenon for the first time in six species. In high marine traffic zones, TBT pollution was registered and the percentage of imposex was high, while these occurrences were null in areas without boat traffic. The species that best reflect the degree of imposex were those inhabiting sandy/muddy or mixed bottoms. TBT determination and imposex incidence indicate that pollution was focused only in ports with high marine traffic or in areas where ship hulls are painted. This is the first report of an imposex-sediment approach to evaluate organotin contamination along the coast of a South American country. [Copyright &y& Elsevier]

Volutes are widely distributed in the Cenozoic record of Patagonia and Tierra del Fuego, where they are represented by the South American endemic genera Adelomelon DalI, 1906, Pachycymbiola Ihering, 1907, Odontocymbiola Clench and Turner, 1964, and Miomelon DalI, 1907. These taxa have been restricted to the southwestern Atlantic and southeastern Pacific Oceans from Tertiary times to the Recent, and since their earliest record in the ?Middle Eocene-Late Oligocene.-earliest Miocene they have evolved adaptations to variations in water depth and temperature. These ecological adaptations were less marked for Adelomelon and Pachycymbiola, which have achieved a similar geographical pattern since the Tertiary, but they were strongly modified in Miomelon. In the Atlantic, Miomelon migrated southwards from the shallow and warm-temperate waters that it typically inhabited during the Tertiary, to deeper, colder waters of the Recent Magellanic Province and Subantarctic region, where it is restricted at present. A detailed discussion of the validity of Tertiary genus Proscaphella Ihering, 1907 herein concludes it to be a synonym of Miomelon DalI, 1907. Seven species are redescribed and illustrated: Adelomelon pilsbryi (Ihering), A. cannada (Ihering), A. (Pachycymbiola) ameghinoi Ihering, ?Pachycymbiola feruglioi (Doello Jurado), Miomelon gracilior (Ihering), M. dorbignyana (Philippi), and M. petersoni (Ortmann); and four new ones are described: Miomelon castilloensis, Pachycymbiola chenquensis, P. camachoi, and P. arriolensis. [ABSTRACT FROM AUTHOR]

Two new species of gastropods belonging to the volutid genus Adelomelon Dall, 1906 are described from Tertiary strata of Patagonia, Argentina. Adelomelon posei n. sp. was found in the lower part of the Gran Bajo del Gualicho Formation (Río Negro Province), which is currently dated as Late Eocene through Middle Miocene in age. Adelomelon valdesiense n. sp. comes from the Puerto Madryn Formation (Chubut Province) of early Late Miocene age. Both species are characterized by angulated biconical teleoconch whorls and strongly developed rows of axial nodes, similar in shape to those of some Recent species of Adelomelon, but positioned differently. Discovery of two new species of the genus Adelomelon in the Tertiary of Patagonia significantly extends the known stratigraphic range of this genus from Late Eocene(?)-Miocene to Recent. [ABSTRACT FROM AUTHOR]