Systematics and geographical distribution of Galba species, a group of cryptic and worldwide freshwater snails.

Cryptic species can present a significant challenge to the application of systematic and biogeographic principles, especially if they are invasive or transmit parasites or pathogens. Detecting cryptic species requires a pluralistic approach in which molecular markers facilitate the detection of coherent taxonomic units that can then be analyzed using various traits (e.g., internal morphology) and crosses. In asexual or self-fertilizing species, the latter criteria are of limited use. We studied a group of cryptic freshwater snails (genus Galba) from the family Lymnaeidae that have invaded almost all continents, reproducing mainly by self-fertilization and transmitting liver flukes to humans and livestock. We aim to clarify the systematics, distribution, and phylogeny of these species with an integrative approach that includes morphology, molecular markers, wide-scale sampling across America, and data retrieved from GenBank (to include Old World samples). Our phylogenetic analysis suggests that the genus Galba originated ca. 22 Myr ago and today comprises six species or species complexes. Four of them show an elongated-shell cryptic phenotype and exhibit wide variation in their genetic diversity, geographic distribution, and invasiveness. The remaining two species have more geographically restricted distributions and exhibit a globose-shell cryptic phenotype, most likely phylogenetically derived from the elongated one. We emphasize that no Galba species should be identified without molecular markers. We also discuss several hypotheses that can explain the origin of cryptic species in Galba, such as convergence and morphological stasis.

A new multiplex PCR assay to distinguish among three cryptic Galba species, intermediate hosts of Fasciola hepatica.

A molecular tool described here allows in one step for specific discrimination among three cryptic freshwater snail species (genus Galba) involved in fasciolosis transmission, a worldwide infectious disease of humans and livestock. The multiplex PCR approach taken targets for each species a distinctive, known microsatellite locus which is amplified using specific primers designed to generate an amplicon of a distinctive size that can be readily separated from the amplicons of the other two species on an agarose gel. In this way, the three Galba species (G. cubensis, G. schirazensis, and G. truncatula) can be differentiated from one another, including even if DNA from all three were present in the same reaction. The accuracy of this new molecular tool was tested and validated by comparing multiplex PCR results with species identification based on sequences at mitochondrial and nuclear markers. This new method is accurate, inexpensive, simple, rapid, and can be adapted to handle large sample sizes. It will be helpful for monitoring invasion of Galba species and for developing strategies to limit the snail species involved in the emergence or re-emergence of fasciolosis.

Características biológicas de una cepa de tripanosoma cruzi en un modelo murino y análisis de supervivencia / Characteristic biological of a strain of trypanosoma cruzi in a murine model and analysis of survival

Conocer las características biológicas de una cepa de Trypanosoma cruzi, procedente de Tiabaya, Arequipa, Perú,y determinar la supervivencia de los ratones inoculados con relación a la dosis infectante y al sexo. Se utilizaron 14 ratones BALB/C-53 (machos y hembras) de 30 días. Los grupos I y II fueron inoculados por vía intraperitoneal con 1,8 x 105 y 1,8 x 104 trypomastigotes metacíclicos de T. cruzi, respectivamente; el grupo III con 1,5 x 107 trypomastigotes sanguíneos. El grupo control (IV) recibió solo solución salina fisiológica al 0,9 por ciento. Los parásitos fueron evaluados en sangre periférica de los ratones. El análisis de supervivencia fue realizado por el método de Kaplan-Meier, test deLogaritmo de rangos y Wilcoxon al 95 por ciento de nivel de confianza. Se encontraron formas delgadas y gruesas de T. cruzi. La letalidad fue 100 por ciento al día 40 postinfección (pi). La parasitemia fue detectada desde el 6to hasta el 40mo día pi y el pico máximo global (6747 parásitos) fue observado al 29no día pi. Existen diferencias significativas en la supervivenciade los ratones inoculados de acuerdo a la dosis por la prueba de Logaritmo de rangos (p = 0,0202). La cepa de T. cruzi,procedente de Tiabaya, Arequipa es de mediana virulencia. La supervivencia de los ratones infectados está relacionadaa la dosis de inoculación.

To know the biological characteristics of a strain of Trypanosome cruzi, coming from the district of Tiabaya, Arequipa,Peru, and to determine the survival of inoculated mice relating the infecting dose ante and sex. Were used 14 BALB/C-53 mice (males and females) of 30 days of age as biological model. The groups I and II were inoculated via intraperitoneum with 1,8 x 105 and 1,8 x 104 meta-cyclic trypomastigotes of T. cruzi, respectively; group III with 1,5 x 107 sanguine trypomastigotes. Control group (IV) received only physiologic saline solution at 0.9 por ciento. The parasites were searched in peripheral blood of the mouse. The analysis of survival was carried out by Kaplan-Meier method, Logrank test andWilcoxon to 95 por ciento of confidence level. Were find thin and thick forms of T. cruzi. The fatality rate was 100 por ciento groups at day 40 -post-infection- (pi). The parasitemy was detected from the 6th until the 40th day pi and the global maximum pick (6747parasites) was observed on the 29th day pi. Significant differences exist in the survival of inoculated mice according to the dose by the Logrank test (p = 0,0202). The strain of T. cruzi, coming from Tiabaya, Arequipa is of medium virulence. The survival of the infected mice is related to the dose of inoculation.