Search

We studied the population genetic structure of the freshwater snail Galba schirazensis (Kuster, 1862), a potential vector of infectious diseases such as fascioliasis. Galba schirazensis has now a worldwide distribution but a poorly known origin because this species has been distinguished only recently from the morphologically similar and cosmopolitan Galba truncatula (O.F. Muller, 1774). We developed specific microsatellite markers and sequenced a mitochondrial gene (cytochrome oxidase subunit I (CO1)) to study individuals of G. schirazensis from the Old World and the New World. We found very low genetic diversity within populations, no heterozygotes, and marked population structure--a pattern observed in other highly selfing lymnaeid species with recently enlarged distributions as a result of biological invasions. The total lack of observed heterozygosity in the few populations of G. schirazensis that displayed some allelic diversity suggests high selfing rates. We also found that the center of diversity, and by extension the origin area of this species, should be found in the New World, whereas Old World populations should rather result from a recent introduction of a genetically uniform population. The microsatellite markers developed here will help to clarify the history of expansion of G. schirazensis and might help to understand its role as a potential vector of infectious diseases. Key words: lymnaeids, Lymnaea, Galba schirazensis, Galba truncatula, vector, microsatellites, selfing. Nous avons etudie la structure genetique des populations du gasteropode d'eau douce Galba schirazensis (Kuster, 1862), un vecteur potentiel de maladies infectieuses telles que la fasciolose. Galba schirazensis presente aujourd'hui une repartition planetaire, mais une origine meconnue puisque cette espece n'a que recemment ete distinguee de Galba truncatula (O.F. Muller, 1774), une espece cosmopolite semblable sur le plan morphologique. Nous avons mis au point des marqueurs microsatellites specifiques et sequence un gene mitochondrial (la sous-unite I de la cytochrome oxidase (CO1)) pour etudier des individus de G. schirazensis de l'Ancien Monde et du Nouveau Monde. Nous n'avons note qu'une tres faible diversite genetique au sein des populations, aucun heterozygote et une structure marquee des populations, des caracteristiques observees chez d'autres especes de lymnees tres autofecondes dont les aires de repartition ont beaucoup cru recemment dans la foulee d'invasions biologiques. L'absence totale d'heterozygotie observee dans les quelques populations de G. schirazensis qui presentaient un certain degre de diversite allelique indiquerait des taux d'autofecondation eleves. Nous avons egalement observe que le centre de diversite et, par extension, la region d'origine de cette espece devraient se trouver dans le Nouveau Monde, alors que les populations de l'Ancien Monde seraient plutot le resultat de l'introduction recente d'une population uniforme sur le plan genetique. Les marqueurs microsatellites ainsi mis au point aideront a preciser l'histoire de l'expansion de G. schirazensis et pourraient aider a comprendre son role comme vecteur potentiel de maladies infectieuses. [Traduit par la Redaction] Mots-cles : lymneides, Lymnaea, Galba schirazensis, Galba truncatula, vecteur, microsatellites, autofecondation., Introduction During the last century, human activities and climatic change have considerably accelerated the spread of species across their natural barriers and modified their areas of distribution (Kolar and Lodge [...]

Sisal whiskers (SW) were prepared by acid hydrolysis for subsequent evaluation as reinforcing material for biodegradable matrices of thermoplastic starch (TPS) and TPS/polycaprolactone (TPS/PCL) blends. The acid hydrolyzed SW had dimensions of 5 ± 2 nm in diameter and 210 [+ or -] 60 nm in length and 78% crystallinity. The nanocomposite blends consisted of whisker contents of 5 and 10 wt% and were coextruded with either TPS or TPS/PCL which formed the matrix material. The influence of SW on the morphology, crystallinity, thermal properties, mechanical behavior, structural, and biodegradation of TPS and TPS/PCL matrices were investigated. The lower SW content of 5 wt% dispersed and interacted well with both matrices. The introduction of PCL in the TPS matrix leads to an increased crystallinity and there was evidence that the carbonyl groups of PCL interacted with the OH groups on the surface of the whiskers. Addition of PCL decreased the whisker/whisker interaction over TPS alone, favoring the dispersion of the whiskers in the matrix and, consequently, the reinforcement effect was more pronounced in TPS/PCL blends than in the pure TPS matrix. The addition of the whiskers as reinforcement increased the biodegradability of TPS and TPS/PCL matrices. POLYM. ENG. SCI., 53:800-808, 2013. © 2012 Society of Plastics Engineers, INTRODUCTION Biodegradable, synthetic or natural polymers have been used as eco-friendly alternatives to petrochemicals (1). There is considerable interest in replacing synthetic and non biodegradable polymers with biodegradable polymers that [...]

Experimental infections of Galba sp. (origin, Colombia) with allopatric isolates of Fasciola hepatica from France or Fascioloides magna from the Czech Republic were carried out during five successive snail generations to determine if this lymnaeid might sustain complete larval development of either parasite. In snails exposed to F. hepatica, 7 of 400 snails harboured several rediae and only two snails contained a small number of free cercariae on day 50 post-exposure. In contrast, the intensity of F. magna infection in Galba sp. progressively increased from the F1 to F5 generations. Spontaneous cercarial shedding of F. magna occurred in 7 of 100 Galba sp. belonging to the F5 generation and the number of shed cercariae did not differ significantly from that noted in control Galba truncatula of French origin. Galba sp. from Colombia can be added to the list of potential intermediate hosts for F. magna. [ABSTRACT FROM AUTHOR]

A wild population of the lymnaeid snail Pseudosuccinea columella infected by larval stages of Fasciola hepatica was discovered in the Pinar del Río Province, Cuba. One of 100 snails was infected in a rice culture field. This is the first time this species has been found acting as intermediate host of F. hepatica under natural conditions, not only for Cuba but also for the Caribbean area. [ABSTRACT FROM AUTHOR]