La saison sèche en Guadeloupe et ses conséquences sur la démographie des mollusques dans les biotopes A Biomphalaria glabrata (say, 1818), vecteur de la bilharziose intestinale

Resistance of some freshwater snails to drought has been studied in four seasonal ponds, one (temporary) stream and one « mangrove » area on the island of Guadeloupe, West Indies. In such locations a small percentage of the snail population is able to survive the dry season under the shelter of organic debris and rocks. Biomphalaria glabrata, the local intermediate host of human Rilharziasis, is less resistant to dessication than sympatric Eupera viridans, Biomphalaria schrammi, Drepanotrema lucidum and Ampullaria glauca. Physa marmorata, Drepanotrema kermatoides and Pleisiophysa granulata are even more sensitive to drought than Biomphalaria glabrata

Distribución actualizada de limneidos vectores de Fasciola hepatica e índice cercárico en la región Arequipa, Perú

Fasciolosis is a zoonotic disease caused by Fasciola hepatica, which is widely distributed in Peru and considered highly endemic in the Arequipa region. Despite this, records of lymnaeid snails in the area remain limited. This study aimed to identify lymnaeid vectors of F. hepatica and to determine their distribution across natural regions, along with their corresponding cercarial index (CI). Lymnaeid snails were manually collected from irrigation canals, wetlands, and other humid environments, identified by their small size and dextral coiling shell. A subset of 10–25 snails was immersed in water at 70°C for 30–40 seconds to facilitate soft tissue extraction. The soft bodies were then removed from the shells and preserved in 70% ethanol. Taxonomic identification was conducted at the Centre de Recherches insulaires et observatoire de L’environnement (CRIOBE), Université de Perpignan, France, based on morphological characteristics of the shell and soft body parts. Sampling locations were categorized according to natural regions: coast (≤2000 m.a.s.l.) and highlands (>2000 m.a.s.l.). Live lymnaeids were examined by compression under a compound microscope (40X and 100X magnification). The criterion for positivity was the presence of rediae and cercariae of F. hepatica. New distribution areas of lymnaeid snails were identified. On the coast, the species detected included Galba cubensis (primary vector) in the provinces of Caravelí, Camaná, Islay, and Arequipa; Pseudosuccinea columella (potential vector) in Caravelí; and G. schirazensis in Santa Rita de Siguas. In the highlands, G. truncatula was identified as the primary vector in the provinces of Caylloma, La Unión, Castilla, Condesuyos, and Arequipa. Cercarial indices were generally low, averaging 0.63% for the Arequipa region. In localities with positive vectors, the distribution was as follows: on the coast, G. cubensis in Vítor showed a CI of 2.13%; in the highlands, G. truncatula exhibited CI values of 1.20% in Huanca, 1.61% in Achoma, 2.63% in Maca, and 2.78% in Taurisma.La fasciolosis es una zoonosis causada por Fasciola hepatica, de amplia distribución en el Perú y particularmente endémica en Arequipa. En esta región, los reportes de limneidos son escasos. Se realizó el estudio en la región Arequipa, con el objetivo de identificar los limneidos vectores de F. hepatica, su distribución de acuerdo con la región natural y el índice cercárico (IC). Se colectaron limneidos, de forma manual en acequias, bofedales o lugares húmedos, reconocidos por su tamaño pequeño y su conchilla dextrógira. Una parte (10-25 caracoles) fue introducida en agua a 70 °C por 30-40 segundos. Posteriormente, se extrajo el cuerpo blando de la conchilla y esta fue fijada en etanol 70%. La identificación taxonómica basada en caracteres morfológicos de las partes blandas y conchilla fue realizada en el Centre de Recherches insulaires et observatoire de L´environnement (CRIOBE), Université de Perpignan, Francia. Las localidades se clasificaron según región natural: costa (hasta 2.000 m s. n. m.) y sierra (sobre 2.000 m s. n. m.). Los limneidos vivos fueron examinados por aplastamiento en microscopio compuesto. El criterio de positividad fue la observación de redias y cercarias compatibles con F. hepatica. Se detectaron nuevas áreas de distribución de limneidos. Las especies identificadas en la costa fueron Galba cubensis vector primario en las provincias de Caravelí, Camaná, Islay y Arequipa; Pseudosuccinea columella vector potencial en Caravelí y G. schirazensis en Santa Rita de Siguas. En la sierra se identificó a G. truncatula como vector primario en las provincias de Caylloma, La Unión, Castilla, Condesuyos y Arequipa. Los índices cercáricos en general fueron bajos con 0,63% para la región Arequipa y por localidades con vectores positivos distribuidos en la costa (G. cubensis) 2,13% en Vítor; y en la sierra (G. truncatula) en Huanca 1,20%, Achoma 1,61%, Maca 2,63% y Taurisma 2,78%

Primeiro registro do gastrópode africano invasor Melanoides tuberculatus (Gastropoda: Prosobranchia: Thiaridae) na Bacia do Rio Paranã, GO, Brasil

The Thiarid snail Melanoides tuberculatus (Müller, 1774), native to Asia and East Africa was recorded for the first time in the Paranã River basin, Goiás State. There is no evidence concerning introduction vectors but aquarium releases is the most probable vector. Specimens were collected at three different water bodies after twenty-seven rivers were investigated. The possible spread of this species to other habitats and potential effects on native thermal water communities are discussed.O gastrópode Thiaridae Melanoides tuberculatus (Müller, 1774), nativo da Ásia e do Leste Africano, é registrado pela primeira vez na Bacia Hidrográfica do Rio Paranã (Estado de Goiás). Não se conhecem os vetores de introdução da espécie, mas o setor de aquariofilia foi apontado por alguns moradores locais como a mais provável causa. Os espécimes foram coletados em três corpos d´água depois de serem investigados vinte e sete rios e lagoas. A possibilidade de dispersão dessa espécie para outros habitats e os efeitos potenciais dessa introdução sobre a comunidade nativa são discutidos no artigo

Stable Isotope Evidence for Dietary Overlap between Alien and Native Gastropods in Coastal Lakes of Northern KwaZulu-Natal, South Africa

Tarebia granifera (Lamarck, 1822) is originally from South-East Asia, but has been introduced and become invasive in many tropical and subtropical parts of the world. In South Africa, T. granifera is rapidly invading an increasing number of coastal lakes and estuaries, often reaching very high population densities and dominating shallow water benthic invertebrate assemblages. An assessment of the feeding dynamics of T. granifera has raised questions about potential ecological impacts, specifically in terms of its dietary overlap with native gastropods.A stable isotope mixing model was used together with gut content analysis to estimate the diet of T. granifera and native gastropod populations in three different coastal lakes. Population density, available biomass of food and salinity were measured along transects placed over T. granifera patches. An index of isotopic (stable isotopes) dietary overlap (IDO, %) aided in interpreting interactions between gastropods. The diet of T. granifera was variable, including contributions from microphytobenthos, filamentous algae (Cladophora sp.), detritus and sedimentary organic matter. IDO was significant (>60%) between T. granifera and each of the following gastropods: Haminoea natalensis (Krauss, 1848), Bulinus natalensis (Küster, 1841) and Melanoides tuberculata (Müller, 1774). However, food did not appear to be limiting. Salinity influenced gastropod spatial overlap. Tarebia granifera may only displace native gastropods, such as Assiminea cf. ovata (Krauss, 1848), under salinity conditions below 20. Ecosystem-level impacts are also discussed.The generalist diet of T. granifera may certainly contribute to its successful establishment. However, although competition for resources may take place under certain salinity conditions and if food is limiting, there appear to be other mechanisms at work, through which T. granifera displaces native gastropods. Complementary stable isotope and gut content analysis can provide helpful ecological insights, contributing to monitoring efforts and guiding further invasive species research

Lymnaea schirazensis, an Overlooked Snail Distorting Fascioliasis Data: Genotype, Phenotype, Ecology, Worldwide Spread, Susceptibility, Applicability

BACKGROUND: Lymnaeid snails transmit medical and veterinary important trematodiases, mainly fascioliasis. Vector specificity of fasciolid parasites defines disease distribution and characteristics. Different lymnaeid species appear linked to different transmission and epidemiological patterns. Pronounced susceptibility differences to absolute resistance have been described among lymnaeid populations. When assessing disease characteristics in different endemic areas, unexpected results were obtained in studies on lymnaeid susceptibility to Fasciola. We undertook studies to understand this disease transmission heterogeneity. METHODOLOGY/PRINCIPAL FINDINGS: A ten-year study in Iran, Egypt, Spain, the Dominican Republic, Mexico, Venezuela, Ecuador and Peru, demonstrated that such heterogeneity is not due to susceptibility differences, but to a hitherto overlooked cryptic species, Lymnaea schirazensis, confused with the main vector Galba truncatula and/or other Galba/Fossaria vectors. Nuclear rDNA and mtDNA sequences and phylogenetic reconstruction highlighted an old evolutionary divergence from other Galba/Fossaria species, and a low intraspecific variability suggesting a recent spread from one geographical source. Morphometry, anatomy and egg cluster analyses allowed for phenotypic differentiation. Selfing, egg laying, and habitat characteristics indicated a migration capacity by passive transport. Studies showed that it is not a vector species (n = 8572 field collected, 20 populations): snail finding and penetration by F. hepatica miracidium occur but never lead to cercarial production (n = 338 experimentally infected). CONCLUSIONS/SIGNIFICANCE: This species has been distorting fasciolid specificity/susceptibility and fascioliasis geographical distribution data. Hence, a large body of literature on G. truncatula should be revised. Its existence has henceforth to be considered in research. Genetic data on livestock, archeology and history along the 10,000-year post-domestication period explain its wide spread from the Neolithic Fertile Crescent. It is an efficient biomarker for the follow-up of livestock movements, a crucial aspect in fascioliasis emergence. It offers an outstanding laboratory model for genetic studies on susceptibility/resistance in F. hepatica/lymnaeid interaction, a field of applied research with disease control perspectives

Avaliação de populações de planorbídeos, em habitats naturais, pelo método de perfuração da concha

Propõe-se um novo método de marcação de planorbídeos para determinação de densidade e de outros parâmetros pertinentes ao estudo de dinâmica de população, como capacidade de migração, taxas de crescimento e potencial biótico nos habitats naturais. Consiste em marcação através de dois furos de cerca de 2 mm de diâmetro de cada lado da concha em sua extremidade anterior, usando-se um estilete metálico. Após a marcação os caramujos são imediatamente reintroduzidos no habitat, em local correspondente ao da captura processada poucos minutos antes. Nos experimentos realizados, as taxas de caramujos marcados, recapturados uma semana após a marcação, variaram de 14 a 18% e permitiram calcular a população total de B. glabrata, de 5 mm de diâmetro ou mais. O método permite estimar também a população de jovens com menos de 5 mm e fazer marcações múltiplas. É muito simples, de fácil manejo, não exige equipamentos nem pessoal especializados e provoca menos impacto no ambiente do que outros métodos