ABSTRACT This communication describes the first records of byssal hairs on the postlarvae shells of Mytilus edulis platensis d’Orbigny, 1842. The postlarvae used in this study were sampled on artificial collectors used for mussel culture in San Jorge Gulf, Sudoccidental Atlantic Ocean. A general description of the hairs is made as well as an exploratory analysis of their spatial distribution on the shell surface. The presence of these byssal hairs is suggested as a criterion to differentiate M. edulis platensis from other mytilids.

ABSTRACT Although the presence of apertural folds and lamellae is the most recognizable character of the Odontostomidae, some species lack them, mostly in Anctus Martens, 1860, Bahiensis Jousseaume, 1877 and Moricandia Pilsbry & Vanatta, 1898. Eudioptus avellanedae Doering, 1881 - a slender odontostomid species that lacks even the slightest trace of folds or lamellae in its shell aperture - was however transferred to Odontostomus by Pilsbry in 1902 on the basis of its building forward of the aperture-margins. It is currently placed in its own monotypic subgenus, Cyclodontina (Ventania) Parodiz, 1940, on the basis of about the same argument. In this paper we redescribe its shell morphology and, for the first time, describe the internal anatomy of the pallial complex and the reproductive and digestive systems. The presence of a spongy gland in the pallial complex; of a short penis sheath with no retractor muscle; of a bursa copulatrix duct longer than spermoviduct, and of an epiphallic gland strongly support the inclusion of this unusual species in Odontostomidae. The species is diagnosable by the sculpture of the protoconch, which is not smooth as previously described, but has waved axial ribs crossed by spiral lines in young specimens; the distinctive external and internal shape of the bursa copulatrix duct; the internal penis wall divided in three regions of different sculpture; the smooth inner wall of the vagina; the long and cylindrical epiphallus with a distal widening indicating the presence of an epiphallic gland, and the penis retractor muscle inserted in the distal end of a short flagellum. These characters support the validity of Ventania Parodiz, 1940, different from Cyclodontina Beck, 1837.

Quinquelaophonte aestuarii sp. nov. (Copepoda, Harpacticoida) from Bahía Blanca estuary is the first record of Quinquelaophonte Wells, Hicks & Coull, 1982 in Argentina and its southernmost location in the world. The setal formula (P2: exopod 1.2.3-endopod 1.2.0; P3: exopod 1.2.3-endopod 2.2.1; P4: exopod 1.2.3-endopod 1.2.0) of the last segment of P2-P4, in both the exopod and the endopod, distinguishes this species from all known species in Quinquelaophonte, except for Quinquelaophonte varians Bjornberg, 2010. The new species differs from the latter in the setal formula of the antennule, the mouth parts and maxillipeds, the absence of an inner seta on the second exopod segment of P2, the length of the second exopod segment of P4 and in the shape of baseoendopod setae of P5.

The widespread Mexican apple snail Pomacea flagellata (Say 1827) and the strictly endemic "tegogolo" P. patula catemacensis (Baker 1922) (restricted to Lake Catemaco), are the only known American Ampullariidae that have haploid complements n=13. Pomacea patula catemacensis has suffered a critical reduction in abundance due to immoderate fishing for human consumption. Chromosome slides were obtained from colchicine-injected Pomacea snails collected from nine locations along the coastal zone of the Gulf of Mexico, including Lake Catemaco, for use in principal component analysis (PCA). Total proteins in foot homogenates were analyzed through isoelectric focusing (IEF) and native-PAGE electrophoresis on polyacrylamide gels. The chromosome number 2n=26 was confirmed for snails from all locations, with a uniform 9 m + 4 sm formula. However, P. patula catemacensis showed significantly larger chromosomes (absolute size) than any population of P. flagellata. Pomacea patula catemacensis also differed from all populations of P. flagellata in a PCA with standardized data, i.e., independently of the absolute size difference between species. Proteins with an acid isoelectric point were dominant in the foot of both species. The electrophoresis analysis showed that P. flagellata has 17 protein bands, with an upper bound at IEF=7.6, while P. patula catemacensis has only 15 bands, with an upper bound at IEF=7 and a more evenly spaced band pattern. Molecular weights ranged from 40 to approximately 130 kDa in both species. Proteins with high values (>94 kDa) were the most abundant. Pomacea patula catemacensis showed a band of 93 kDa, which was absent from all specimens of P. flagellata. Samples of P. flagellata did not cluster according to any geographical pattern in the statistical analyses, nor did they show any taxonomically useful differences in their electrophoretic patterns that merit sub-specific discrimination.

Mitotic chromosomes of the freshwater snail Pomacea patula catemacensis (Baker 1922) were analyzed on gill tissue of specimens from the type locality (Lake Catemaco, Mexico). The diploid number of chromosomes is 2n = 26, including nine metacentric and four submetacentric pairs; therefore, the fundamental number is FN = 52. No sex chromosomes could be identified. The same chromosome number and morphology were already reported for P. flagellata, i.e., the other species of the genus living in Mexico. The basic haploid number for family Ampullariidae was reported to be n = 14 in the literature; so, its reduction to n = 13 is probably an apomorphy of the Mexican Pomacea snails. Lanistes bolteni, from Egypt, also shows n = 13, but its karyotype is much more asymmetrical, and seems to have evolved independently from P. flagellata and P. patula catemacensis. The nominotypical subspecies, P. patula patula (Reeve 1856), is a poorly known taxon, whose original locality is unknown. A taxonomical account is presented here, and a Mexican origin postulated as the most parsimonious hypothesis.

Previous authors demonstrated that Triatoma virus (TrV) is able to infect several species of triatomines when injected with viral inoculum obtained from its original host, T. infestans. Both vertical (transovarian) and horizontal (faecal-oral) mechanisms of viral transmission were also described. In this paper we report the experimental TrV infection of a wild species from southern Argentina, T. patagonica. The inoculum consisted of clarified gut contents of infected T. infestans rubbed on the chicken skin whereupon T. patagonica individuals were fed. The results demonstrate that this is another potential host for the virus, and that the oral route is also effective for experimental interspecific infections.