Insights into the relationships of Palearctic and Nearctic lymnaeids (Mollusca : Gastropoda) by rDNA ITS-2 sequencing and phylogeny of stagnicoline intermediate host species of Fasciola hepatica

Fascioliasis by Fasciola hepatica is the vector-borne disease presenting the widest latitudinal, longitudinal and altitudinal distribution known. F. hepatica shows a great adaptation power to new environmental conditions which is the consequence of its own capacities together with the adaptation and colonization abilities of its specific vector hosts, freshwater snails of the family Lymnaeidae. Several lymnaeid species only considered as secondary contributors to the liver fluke transmission have, however, played a very important role in the geographic expansion of this disease. Many of them belong to the so-called "stagnicoline" type group. Stagnicolines have, therefore, a very important applied interest in the Holarctic region, to which they are geographically restricted. The present knowledge on the genetics of stagnicolines and on their parasite-host interrelationships is, however, far from being sufficient. The present paper analyses the relationships between Palaearctic and Nearctic stagnicoline species on the base of the new light furnished by the results obtained in nuclear rDNA ITS-2 sequencing and corresponding phylogenetic studies of the lymnaeid taxa Lymnaea (Stagnicola) occulta, L. (S.) palustris palustris (topotype specimens) and L. (S.) p. turricula from Europe. Natural infections with F. hepatica have been reported in all of them. Surprisingly, ITS-2 length and GC content of L. occulta were similar and perfectly fitted within the respective ranges known in North American stagnicolines. Nucleotide differences and genetic distances were higher between L. occulta and the other European stagnicolines than between L. occulta and the North American ones. The ITS-2 sequence of L. p. turricula from Poland differed from the other genotypes known from turricula in Europe. The phylogenetic trees using the maximum-parsimony, distance and maximum-likelihood methods confirmed (i) the inclusion of L. occulta in the branch of North American stagnicolines, (ii) the link between the North American stagnicolines-L. occulta group with Galba truncatula, and (iii) the location of the L. p. turricula genotype from Poland closer to L. p. palustris than to other European L. p. turricula genotypes. The Palaearctic species occulta is included in the genus Catascopia, together with the Nearctic species catascopium, emarginata and elodes. The results suggest a potential of transmission capacity for C. occulta higher than that of other European stagnicolines or Omphiscola glabra. The relatively low genetic distances between C. occulta and G. truncatula and the clustering of both species in the same clade suggest that C. occulta may be potentially considered as the second lymnaeid intermediate host species of F. hepatica in importance in eastern and northern Europe, and probably also western and central Asia, after G. truncatula. L. p. turricula may be considered as a potential secondary vector of F. hepatica, at a level similar to that of L. p. palustris.(VLID)221360

A recent finding of Didogobius schlieweni(Gobiidae) with some notes on its ecology and distribution

Background. This paper reports a new record of Didogobius schlieweni in the Ligurian Sea (Italy). Ecological data of all previous findings and the distribution of this species in the Mediterranean Sea are presented

Morphological and developmental studies on the eggs of four Coryphopterus species (Actinopterygii: Gobiidae) in the Caribbean Sea

Background. Morphology of eggs and embryonic development of the genus Coryphopterus are documented for the first time. The species C. venezuelae, C. dicrus, C. eidolon, and C. thrix have been found to have a similar ecology, but details about their reproduction are still unclear. The aim of the present study was to investigate if egg morphology, mode of attachment, and development differ between the species; which could be attributed to use of different microhabitats and/or resources. Materials and methods. Fish were kept in aquaria and their eggs were collected every 6 h. Embryonic development in the eggs was documented under a dissecting microscope. Additionally egg morphology and mode of egg attachment were studied by a scanning electron microscope. Results. The time of embryonic development was 66 h in all species. Egg dimensions were 0.7–1.1 mm in length and 0.3–0.5 mm in width. The eggs were attached to the substrate by an adhesive apparatus typical for gobiids, a net like structure around the micropylar pole, and composed of filaments, 1.5–2.2 μm in diameter. The zona radiata was of 0.5–0.8-μm thick. Conclusion. No differences in the period of embryonic development, egg shape or means of attachment could be found between the species studied, but variations in egg dimensions and their attaching structures were noted. The zona radiata is very thin in comparison to other fish eggs, though comparative data of fish with a similar ecology are needed

Morphological and developmental studies on the eggs of four Coryphopterus species (Actinopterygii: Gobiidae) in the Caribbean Sea

Background. Morphology of eggs and embryonic development of the genus Coryphopterus are documented for the first time. The species C. venezuelae, C. dicrus, C. eidolon, and C. thrix have been found to have a similar ecology, but details about their reproduction are still unclear. The aim of the present study was to investigate if egg morphology, mode of attachment, and development differ between the species; which could be attributed to use of different microhabitats and/or resources. Materials and methods. Fish were kept in aquaria and their eggs were collected every 6 h. Embryonic development in the eggs was documented under a dissecting microscope. Additionally egg morphology and mode of egg attachment were studied by a scanning electron microscope. Results. The time of embryonic development was 66 h in all species. Egg dimensions were 0.7–1.1 mm in length and 0.3–0.5 mm in width. The eggs were attached to the substrate by an adhesive apparatus typical for gobiids, a net like structure around the micropylar pole, and composed of filaments, 1.5–2.2 μm in diameter. The zona radiata was of 0.5–0.8-μm thick. Conclusion. No differences in the period of embryonic development, egg shape or means of attachment could be found between the species studied, but variations in egg dimensions and their attaching structures were noted. The zona radiata is very thin in comparison to other fish eggs, though comparative data of fish with a similar ecology are needed

Insights into the relationships of Palearctic and Nearctic lymnaeids (Mollusca : Gastropoda) by rDNA ITS-2 sequencing and phylogeny of stagnicoline intermediate host species of Fasciola hepatica

Fascioliasis by Fasciola hepatica is the vector-borne disease presenting the widest latitudinal, longitudinal and altitudinal distribution known. F. hepatica shows a great adaptation power to new environmental conditions which is the consequence of its own capacities together with the adaptation and colonization abilities of its specific vector hosts, freshwater snails of the family Lymnaeidae. Several lymnaeid species only considered as secondary contributors to the liver fluke transmission have, however, played a very important role in the geographic expansion of this disease. Many of them belong to the so-called "stagnicoline" type group. Stagnicolines have, therefore, a very important applied interest in the Holarctic region, to which they are geographically restricted. The present knowledge on the genetics of stagnicolines and on their parasite-host interrelationships is, however, far from being sufficient. The present paper analyses the relationships between Palaearctic and Nearctic stagnicoline species on the base of the new light furnished by the results obtained in nuclear rDNA ITS-2 sequencing and corresponding phylogenetic studies of the lymnaeid taxa Lymnaea (Stagnicola) occulta, L. (S.) palustris palustris (topotype specimens) and L.(S.) p. turricula from Europe. Natural infections with F. hepatica have been reported in all of them. Surprisingly, ITS-2 length and G C content of L. occulta were similar and perfectly fitted within the respective ranges known in North American stagnicolines. Nucleotide differences and genetic distances were higher between L. occulta and the other European stagnicolines than between L. occulta and the North American ones. The ITS-2 sequence of L. p. turricula from Poland differed from the other genotypes known from turricula in Europe. The phylogenetic trees using the maximum-parsimony, distance and maximum-likelihood methods confirmed (i) the inclusion of L. occulta in the branch of North American stagnicolines, (iii) the link between the North American stagnicolines-L. occulta group with Galba truncatula, and (iii) the location of the L. p. turricula genotype from Poland closer to L. p. palustris than to other European L. p. turricula genotypes. The Palaearctic species occulta is included in the genus Catascopia, together with the Nearctic species catascopium, emarginata and elodes. The results suggest a potential of transmission capacity for C. occulta higher than that of other European stagnicolines or Omphiscola glabra. The relatively low genetic distances between C. occulta and G. truncatula and the clustering of both species in the same clade suggest that C.occulta may be potentially considered as the second lymnaeid intermediate host species of F. hepatica in importance in eastern and northern Europe, and probably also western and central Asia, after G. truncatula. L. p. turricula may be considered as a potential secondary vector of F. hepatica, at a level similar tot that of L.p. palustris

Insights into the relationships of Palearctic and Nearctic lymnaeids (Mollusca : Gastropoda) by rDNA ITS-2 sequencing and phylogeny of stagnicoline intermediate host species of

Fascioliasis by Fasciola hepatica is the vector-borne disease presenting the widest latitudinal, longitudinal and altitudinal distribution known. F. hepatica shows a great adaptation power to new environmental conditions which is the consequence of its own capacities together with the adaptation and colonization abilities of its specific vector hosts, freshwater snails of the family Lymnaeidae. Several lymnaeid species only considered as secondary contributors to the liver fluke transmission have, however, played a very important role in the geographic expansion of this disease. Many of them belong to the so-called "stagnicoline" type group. Stagnicolines have, therefore, a very important applied interest in the Holarctic region, to which they are geographically restricted. The present knowledge on the genetics of stagnicolines and on their parasite-host interrelationships is, however, far from being sufficient. The present paper analyses the relationships between Palaearctic and Nearctic stagnicoline species on the base of the new light furnished by the results obtained in nuclear rDNA ITS-2 sequencing and corresponding phylogenetic studies of the lymnaeid taxa Lymnaea (Stagnicola) occulta, L. (S.) palustris palustris (topotype specimens) and L.(S.) p. turricula from Europe. Natural infections with F. hepatica have been reported in all of them. Surprisingly, ITS-2 length and G C content of L. occulta were similar and perfectly fitted within the respective ranges known in North American stagnicolines. Nucleotide differences and genetic distances were higher between L. occulta and the other European stagnicolines than between L. occulta and the North American ones. The ITS-2 sequence of L. p. turricula from Poland differed from the other genotypes known from turricula in Europe. The phylogenetic trees using the maximum-parsimony, distance and maximum-likelihood methods confirmed (i) the inclusion of L. occulta in the branch of North American stagnicolines, (iii) the link between the North American stagnicolines-L. occulta group with Galba truncatula, and (iii) the location of the L. p. turricula genotype from Poland closer to L. p. palustris than to other European L. p. turricula genotypes. The Palaearctic species occulta is included in the genus Catascopia, together with the Nearctic species catascopium, emarginata and elodes. The results suggest a potential of transmission capacity for C. occulta higher than that of other European stagnicolines or Omphiscola glabra. The relatively low genetic distances between C. occulta and G. truncatula and the clustering of both species in the same clade suggest that C.occulta may be potentially considered as the second lymnaeid intermediate host species of F. hepatica in importance in eastern and northern Europe, and probably also western and central Asia, after G. truncatula. L. p. turricula may be considered as a potential secondary vector of F. hepatica, at a level similar tot that of L.p. palustris