Abstract:

Molluscan taphonomic patterns below the sediment-water interface in three freshwater shallow lakes from the Southeastern Pampa Plain, Argentina (Nahuel Ruca´, Las Mostazas, and Los Carpinchos), were analyzed in order to explore the taphonomic alteration suffered by mollusks with depth and determine if this taphonomic alteration varied locally within lakes or between them. Short cores (approximately 30 cm) from littoral environment as well as open water were sampled in each lake. Nine mollusk species were identified: Heleobia parchappii, H. australis, Biomphalaria peregrina, Uncancylus concentricus, Musculium argentinum, Drepanotrema kermatoides, Succinea meridionalis, Antillorbis nordestensis, and Pomacea canaliculata. The highest percentage of moisture, organic matter and carbonates as well as less alkaline pH were recorded at the top of the cores and in littoral environments, indicating less favorable conditions for preservation. Results suggest that the taphonomically active zone occupies the first 10 cm below the sediment-water interface.

Author affiliation: Cristini, Paula Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina

Author affiliation: de Francesco, Claudio German. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina

Abstract:

The dates of publication of ten papers of A. Doering published from 1874–1879 in two Argentinan journals are reviewed. Seven of these papers appear to have been published later than their printed dates suggest. The status of one taxon described in these papers, Clessinia Doering, 1875, is clarified.

Author affiliation: Breure, Abraham S.H.. Naturalis Biodiversity Center; Países Bajos

Author affiliation: Miquel, Sergio Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina

Abstract:

Zidona dufresnei is a carnivorous snail that plays an important role in the trophic web as a top predator. It is a threatened species due to high levels of fisheries exploitation. In this study, we describe the morphology of the digestive gland of Z. dufresnei from Mar del Plata, Argentina, and discuss the function and the cycle of activity of the different cell types. Histological analysis reveals two types of tubules: type 1 tubules composed of digestive and basophilic cells and type 2 tubules lined by basophilic cells only. Pyramidal basophilic cells contain lipofuscin and a large amount of rough endoplasmic reticulum, which suggests that these cells are responsible for the secretion of digestive enzymes that initiate the extracellular digestion of the food. Columnar digestive cells exhibit large membrane-bound vesicles that contain proteoglycans, neutral glycosaminoglycans and small amounts of lipid and lipofuscin. The presence in digestive cells of many endocytic vesicles and residual lysosomal bodies, as evidenced by the presence of lipofuscin pigments in the apical region, indicate that digestion is completed intracellularly within these cells. The digestive cells are subject to cyclical changes involving four phases: initial, digestion, fragmentation, and disintegration stages.

Author affiliation: Ojeda, Mariel Adriana. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; Argentina

Author affiliation: Arrighetti, Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; Argentina

Author affiliation: Giménez, Juliana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; Argentina

Abstract:

A hemocyte primary culture system for Pomacea canaliculata in a medium mimicking hemolymphatic plasma composition was developed. Hemocytes adhered and spread onto culture dish in the first few hours after seeding but later began forming aggregates. Time lapse video microscopy showed the dynamics of the early aggregation, with cells both entering and leaving the aggregates. During this period phagocytosis occurs and was quantified.Later (>4 h), hemocytes formed large spheroidal aggregates that increased in size and also merged with adjacent spheroids (24-96 h). Large single spheroids and spheroid aggregates detach from the bottom surface and float freely in the medium. Correlative confocal, transmission electron and phase contrast microscopy showed a peculiar organization of the spheroids, with a compact core, an intermediate zone with large extracellular lacunae and an outer zone of flattened cells; also, numerous round cells emitting cytoplasmic extensions were seen attaching to the spheroids? smooth surface. Dual DAPI/propidium iodide staining revealed the coexistence of viable and non-viable cells within aggregates, in varying proportions. DNA concentration increased during the first 24 h of culture and stabilized afterward. BrdU incorporation also indicated proliferation.Spontaneous spheroid formation in culture bears interesting parallels with spheroidal hemocyte aggregates found in vivo in P.canaliculata, and also with spheroids formed by tumoral or non-tumoral mammalian cells in vitro.

Author affiliation: Cueto, Juan Agustin. Consejo Nacional de Investigaciones Cientí­ficas y Técnicas. Centro Cientifico Tecnológico Mendoza. Instituto Histologia y Embriología de Mendoza " Dr. M. Burgos"; Argentina

Author affiliation: Vega, Israel Aníbal. Consejo Nacional de Investigaciones Cientí­ficas y Técnicas. Centro Cientifico Tecnológico Mendoza. Instituto Histologia y Embriología de Mendoza " Dr. M. Burgos"; Argentina

Author affiliation: Castro Vazquez, Alfredo Juan. Consejo Nacional de Investigaciones Cientí­ficas y Técnicas. Centro Cientifico Tecnológico Mendoza. Instituto Histologia y Embriología de Mendoza " Dr. M. Burgos"; Argentina

Abstract:

Two new species are described from Brazil. Notocochlis laurae n. sp. from the Canopus Bank, a seamount located 160 Km off Fortaleza, Ceará, is characterized by its large size, the umbilical and parietal calluses separated by a notch; a straight sulcus, and a moderately developed funicle. Color brownish white, with axial and oblique bands extending from the suture to the lower third of the whorl; the subsutural region with a thin white spiral band. N. isabelleana, a shallow water species, is comparable and can be differentiated from N. laurae by its small size, rounded shape, coloration pattern and operculum with only one marginal rib. Notocochlis guesti a deep water species that occurs in Bermuda Is. and the Caribbean can be differentiated by its rounded profile, pale coloration pattern and some radular characters. Natica juani n. sp., distributed from southern Brazil to Uruguay, has a small, smooth shell, with an obsolete funicle. The shell color pattern has axial brownish zig-zag, interconnected, flammules over a white background. The internal margin of the operculum is serrate and the external margin has two thick cords. It is similar to N. perlineata and N. menkeana both Caribbean species with different coloration pattern and a thicker funicle in the latter.

Author affiliation: Santos Costa, Paulo Mauricio. Universidade Federal do Rio de Janeiro; Brasil

Author affiliation: Pastorino, Roberto Santiago Guido. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina

Abstract:

Se dan a conocer 11 nuevos registros de gastrópodos marinos procedentes de numerosas localidades en el centro-oeste de Argentina. Entre ellos se encuentran las siguientes especies nuevas: Proconulus kotrus, Calliotropis (Riselloidea) ligosta, Lyosoma truquicoensis, Exelissa crassicostata, Cirsocerithium agriorivensis, Cataldia? binodosa, Vanikoropsis? leviplicata y Tornatellaea neuquina. Estos registros proceden de dos unidades de edad cretácica temprana de la Cuenca Neuquina: las formaciones Mulichinco (Valanginiano) y Agrio (Valanginiano superior–Hauteriviano superior/Barremiano basal). En esta fauna se encuentran representadas las familias Proconulidae, Calliotropidae, Neritidae, Cryptaulacidae, ?Pseudomelaniidae, Vanikoridae, Epitoniidae y Acteonidae, con un registro no asignado aún a nivel familia.

Eleven new records of marine gastropods from several localities in west-central Argentina are hereby presented, including the following new species: Proconulus kotrus, Calliotropis (Riselloidea) ligosta, Lyosoma truquicoensis, Exelissa crassicostata, Cirsocerithium agriorivensis, Cataldia? binodosa, Vanikoropsis? leviplicata and Tornatellaea neuquina. These records were recovered from two Early Cretaceous units of the Neuquén Basin, the Mulichinco (Valanginian) and the Agrio (upper Valanginian-upper Hauterivian/lowermost Barremian) formations. The families Proconulidae, Calliotropidae, Neritidae, Cryptaulacidae,?Pseudomelaniidae, Vanikoridae, Epitoniidae and Acteonidae are represented whilst one record is yet to be assigned at the family level.

Author affiliation: Cataldo, Cecilia Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos ; Argentina

Abstract:

Larval trematodes infecting Biomphalaria tenagophila and B. occidentalis were surveyed in a suburban and semipermanent pond of Corrientes province, Northeastern Argentina. A total of 1,409 snails were examined between spring 2011 to winter 2013, and 8 different larval trematodes were studied morphologically. Three of these species–Echinocercaria sp. IV, Ribeiroia sp. and Echinocercaria sp. XIV–have been previously found in Corrientes province. Six other trematodes belonging to Strigeidae (Furcocercaria sp. III), Clinostomidae (Cercaria Clinostomidae sp.), Spirorchiidae (Cercaria Spirorchiidae sp.) and Echinostomatidae (Echinocercaria sp. 1, Echinocercaria sp. 2, Echinocercaria sp. 3) are new species parasitizing Biomphalaria snails. Cercaria Spirorchiidae sp. is the third larval trematode related to Spirorchiidae recorded in South America and the first one for Argentina. Cercaria Clinostomidae sp. is the first one related to Clinostomidae in northeastern Argentina. The prevalence of larval trematodes infecting B. tenagophila and B. occidentalis in the environment studied was low (˂5%) with the echinostome group better represented in terms of prevalence and species richness. Drought periods could affect the dynamics of parasitic transmission due to the absence of trematodes in the autumn and winter of the first seasonal cycle. However, in humid periods parasite transmission can occur throughout the year due to the presence of larvae in all seasons of the second seasonal cycle, although the less-warm seasons showed higher prevalence than the summer period probably related to the subtropical climate of Corrientes province.

Author affiliation: Fernández, María Virginia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; Argentina

Author affiliation: Hamann, Mónika Inés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; Argentina

Author affiliation: Ostrowski, Margarita Clotilde. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Abstract:

Gastropod faunas from the Early Jurassic (Late Pliensbachian–Early Toarcian) marine deposits of Chubut Province, Argentina, are described from Lomas Occidentales, Cerro La Trampa and Puesto Currumil localities, representing eight species, three of them new. These are Scurriopsis? sp., Chartronella gradata sp. nov., Calliotropis? sp., Pleurotomaria sp., Leptomaria sp., Hamusina? wahnishae sp. nov., Colpomphalus musacchioi sp. nov. and Jurassiphorus? cf. triadicus Haas. The gastropod assemblage reported here testifies paleobiogeographical connections with other coeval gastropod associations from the western Tethys. However, Chartronella, Hamusina and Jurassiphorus may represent survivors of Triassic associations, considering the ancient seaway from Peru as the most plausible hypothesis for biotic exchange of these faunas during the Late Triassic–Early Jurassic boundary. An abundant and diverse invertebrate fauna such as corals, echinoderms, cephalopods, brachiopods, bivalves and other gastropods found in association with the gastropods described here characterises a shallow marine environment for the gastropod-bearing rocks.

Author affiliation: Ferrari, Silvia Mariel. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Abstract:

To achieve a better understanding of predation pattern recorded in the fossil record it is essential to study predator-prey interactions in the modern seas. It includes the data collected from the field observations as well as from the experiments in captivity. Such an approach allows recognition of the bioeroders, its description and also provides quantification of these interactions. This work offers a case study of the traces of predation resulting from the predator-prey interactions between three mussels: Mytilus chilensis, Brachidontes purpuratus, and Aulacomya atra; and their five natural enemies: the gas- tropods Trophon geversianus, Xymenopsis muriciformis, and Acanthina monodon, and the asteroids Cosmasterias lurida and Anasterias antarctica living along the intertidal and/or subtidal rocky shores in Tierra del Fuego. The predatory dam- age to mussel shells varies according to the predator and prey species and techniques for attacking prey are highly special- ized. A. monodon drills a hole in B. purpuratus but uses the outer lip of its shell as a wedge to open the valves of M. chilensis and A. atra. T. geversianus always makes holes, but while it drills the valve walls of M. chilensis, it prefers to drill the valve edges of A. atra and B. purpuratus, with different characteristic patterns. Usually the shells of mussels killed by C. lurida do not suffer from any mechanical damage, but some other shells were crushed or fractured along the margins. Comparatively, time required to successfully attack a prey was shorter in C. lurida (24 hours), followed by A. monodon (36 hours), and longer in T. geversianus (9 to 10 days). Traces of predation are not randomly distributed across size classes of mussel prey, reflecting selectivity for a particular size class. Also, drill holes are usually placed at specific sectors of the shell, indicating site selectivity. These observations offer some paleontological implications for investigating the pattern of predation in fossil record. They show that different patterns of shell damage can be due to different predator species (e.g., wall vs. edge drillings), although the same predator species can leave different marks when consuming different prey (e.g., T. geversianus). Most disconcerting for paleontologists are cases of predation which do not leave any marks on the prey shell detectable in the fossil record (e.g., predation by asteroids), or leave ambiguous marks (A. monodon when preying with the spine). In conclusion, besides the opportunity to identify some traces of predation by drilling gastropods in fossil mussels, this work gives criteria to address predation in some particular paleontological cases that would otherwise be dismissed by researchers.

Author affiliation: Gordillo, Sandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina

Author affiliation: Archuby, Fernando. Universidad Nacional de Río Negro. Sede Alto Valle. Instituto de Investigaciones en Paleobiología y Geología; Argentina

Abstract:

Quaternary mollusc assemblages preserved in the Salado basin are described and analyzed in order to reconstruct past environments and evaluate spatial and temporal variations. Five localities were analyzed, in which 48,998 individuals of eight continental gastropod species were recovered: Heleobia parchappii, Antillorbis nordestensis, Biomphalaria peregrina, Drepanotrema heloicum, Uncancylus concentricus, Pomacea canaliculata, Succinea meridionalis and Miradiscops brasiliensis. As well, other species typical of marine-estuarine environments have been found, among which Heleobia australis is highlighted. Based on changes in the composition and abundance of the assemblages, different environments could be recognized. Quaternary mollusc assemblages have low taxonomic heterogeneity and spatial and temporal variations. Assemblages recovered from Late Pleistocene-Early Holocene sediments are characterized by low species richness and abundance, with a single species in numerous examples. In the Middle Holocene, the shells became more constant and more diverse. Late Holocene assemblages have high species richness, freshwater, terrestrial and amphibious habits, and show some differences among different localities. Several episodes of flooding have been identified through the record of fossiliferous horizons with high density of shells, mainly Heleobia parchappii. These events that affected the area of influence of the Salado River occurred at least during the Late Holocene.

Author affiliation: Pisano, Maria Florencia. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Fucks, Enrique Eduardo. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; Argentina