Planorbidae, lymnaeidae and physidae of Peru (Mollusca: Basommatophora)

In the course of several trips to Peru I had the opportunity of collecting topotypic specimens of Biomphalaria andecola (Orbigny, 1835), B. helophila (Orbigny, 1835), B. pucaraensis (Preston, 1909), Drepanotrema limayanum (Lesson, 1830), D. kermatoides (Orbigny, 1835), and Lymnaea viatrix Orbigny, 1835, besides B. tenagophila (Orbigny, 1835), Helisoma trivolvis (Say, 1817), H. duryi (Wetherby, 1879), Physa acuta Draparnaud, 1801, and seemingly P. peruviana Gray, 1828. B. pucaraensis is considered a junior synonym of B. peregrina (Orbigny, 1835).     

Planorbidae, Lymnaeidae and Physidae of Ecuador (Mollusca: Basommatophora)

In the course of a trip to Ecuador I had the opportunity of collecting topotypic specimens of the following nominal species of pulmonate molluscs: Biomphalaria cousini Paraense, 1966; Planorbis equatorius Cousin, 1887; P. canonicus Cousin, 1887; Lymnaea cousini Jousseaume, 1887 and P. boetzkesi Miller, 1879. Additional findings were: Helisoma trivolvis (Say, 1817), Biomphalaria peregrina (Orbigny 1835), Drepanotrema anatinum (Orbigny, 1835), D. kermatoides (Orbigny, 1835), D. lucidum (Pfeiffer, 1839), D. surinamense (Clessin, 1884), Lymnaea columella Say, 1817 and Physa acuta Draparnaud, 1805. P. boetzkesi and P. canonicus are considered junior synonyms of Gyraulus hindsianus (Dunker, 1848) and Biomphalaria peregrina (Orbigny, 1835), respectively.     

尖膀胱螺的生物学特征及光照对其生长繁殖影响的初步研究

尖膀胱螺Physa acuta是世界广泛分布的淡水螺类,在我国属外来入侵种.本文着重对该螺的形态特征、繁殖、发育及光照对螺生长和繁殖发育的影响等进行了实验观察和研究.尖膀胱螺个体中等,左旋,壳口无厣.喜聚居于水生植物较多、营养丰富的淡水区域.尖膀胱螺为雌雄同体,异体受精,有时也可自体受精.性成熟个体在条件适宜的情况下(温度、食物和光照)每天都可产卵,卵孵化率近100％.尖膀胱螺胚胎发育共经历卵裂期、囊胚期、原肠期、担轮幼虫期、面盆幼虫期、仔螺形成及出膜期7个时期.一般情况下,螺卵7～10 d可孵化,60 d即可性成熟.25℃、24 h连续光照条件下,尖膀胱螺体重明显增加,40 d就可以性成熟并产卵.     

Populations of the European freshwater pulmonate Physa acuta are not reproductively isolated from American Physa heterostropha or Physa integra

Abstract. It has long been speculated that Physa acuta , a pulmonate snail widespread and invasive in fresh waters of the old world, may have originated in North America. But the identification of a new-world cognate has been complicated by the confused systematics and taxonomy of the Physidae in America. More than 40 species of physids are currently recognized in the United States, many with variable and overlapping morphology. We have previously established that premating reproductive isolation is negligible among physid snails. Here we report the results from no-choice crosses each involving 2 populations of the widespread American species Physa heterostropha and Physa integra , both with each other and with P. acuta , designed to compare measures of reproductive success between species and between populations within species. Samples of P. acuta were collected from France and Ireland, P. heterostropha from eastern Pennsylvania and South Carolina, and P. integra from southern Indiana and northern Michigan. The 6 intrapopulation controls varied quite significantly in their survival, age at first reproduction, parental fecundity, F₁ viability, and F₁ fertility under our culture conditions. Measures of survival and reproduction in the 6 interpopulation crosses were generally intermediate, but in no case significantly worse than the more poorly performing control. Thus we were unable to detect evidence of reproductive isolation among our 6 populations of snails from 2 continents. All should be referred to the oldest available nomen, P. acuta .     

Microsatellite variation in the freshwater snail Physa acuta

We present data for seven new markers isolated from a microsatellite‐enriched DNA library from the freshwater snail Physa acuta. Six of them appear to be conserved in Physa cubensis. These loci might be useful for analysing population structure and reconstructing the story of invasion of freshwaters on a worldwide scale by P. acuta.     

Characterization of 15 polymorphic microsatellite markers in the freshwater snail Aplexa marmorata (Mollusca, Gastropoda)

We describe 15 new variable microsatellites in the freshwater snail Aplexa (Physa) marmorata, as well as conditions for multiplexing and simultaneous genotyping sets of loci. Two to 11 alleles were detected per locus over the five populations studied, and up to eight alleles per locus and population. The observed heterozygosity was extremely low, most probably as the consequence of high selfing rates. The genetic differentiation among populations was large. These markers will constitute efficient tools for investigating the population structure in fragmented habitats. Cross-species amplification in three Physa species (P. acuta, P. fontinalis and P. gyrina) was rather unsuccessful.     

Snail predation by larvae of Sepedon scapularis Adams (Diptera: Sciomyzidae), a potential biocontrol agent of snail intermediate hosts of schistosomiasis in South Africa

Malacophagous larvae of the fly Sepedon scapularis Adams were shown experimentally to be effective predators of three species of aquatic pulmonate snails tested as prey: Bulinus africanus (Krauss) an important intermediate host of Schistosoma haematobium (Bilharz), Bulinus tropicus (Krauss) and the invasive species Physa acuta Draparnaud. Survival of S. scapularis larvae from instar to instar was negatively affected by the size of prey snails, since larvae tended to be asphyxiated by the mucous secretions of the snails, or by the larval hydrofuge hairs becoming entangled in snail faeces. In experiments to test the choice of S.scapularis larvae for different species and sizes of snails, B.africanus was significantly disfavoured compared with the other two snail species. Small snails (< 3 mm) were more frequently killed by all three larval instars of S.scapularis. First instars killed few, if any, large snails (> 7 mm), whereas second and third instars preyed effectively on all sizes of snails. Third instars killed significantly more snails than younger instars. For larvae offered only one species of snail as prey, the mean total number of snails killed per larva during its entire development was 49 B.africanus, 45 B.tropicus or 34 P.acuta. It is concluded that S.scapularis is potentially useful as a biological control agent for use against indigenous Bulinus and exotic Physa snails.     

Predation potential of the water bugs Sphaerodema rusticum on the sewage snails Physa acuta

The sewage snail Physa acuta is a serious threat to certain economic plants and to the purification plant of sewage works by rendering the biofilters ineffective. Various attempts are being made to control it. The efficacy of the predacious water bugs Sphaerodema rusticum was judged experimentally, in the laboratory in the potential control of P. acuta. It is revealed that, when supplied separately, the first, second and third instar and the adult S. rusticum did not attack P. acuta belonging to 3.1-8 mm, 5.1-8 mm, 7.1-8 mm and 相似文献   

A study on snail location by Fasciola hepatica using radioisotopically labelled miracidia.

A number of common freshwater molluscs were exposed to Fasciola hepatica miracidia labelled in vivo with radioselenium. Radioactivity was rapidly incorporated in all lymnaeid species tested (L. stagnalis, L. tomentosa and L. truncatula) whereas no radioactivity could be demonstrated in non-lymnaeid pulmonate species (Aplexa hypnorum, Physa acuta, Physa fontinalis, Anisus vortex, Gyraulus albus and Planorbis planorbis) or in the prosobranchs Valvata cristata and Valvata piscinalis. However, the prosobranchs Bithynia leachii, Bithynia tentaculata and Potamopyrgus jenkinsi showed a slow but significant uptake of radioactivity which was presumably explained by uptake of labelled miracidia through a 'filter-feeding' mechanism. Sphaerium corneum, a true filter-feeder, showed a similar course of uptake of radioactivity.     

Freshwater snails and Schistosomiasis mansoni in the state of Rio de Janeiro, Brazil: IV - Sul Fluminense Mesoregion

In this paper, the forth of a series dealing with the survey of freshwater gastropods of the state of Rio de Janeiro, the results of collections carried out in the Sul Fluminense Mesoregion from 2000 to 2002 are presented and revealed the occurrence of 18 species: Antillorbis nordestensis; Biomphalaria glabrata; Biomphalaria peregrina; Biomphalaria straminea; Biomphalaria tenagophila; Drepanotrema anatinum; Drepanotrema cimex; Drepanotrema lucidum; Ferrissia sp.; Gundlachia ticaga; Gundlachia sp.; Heleobia sp.; Lymnaea columella; Melanoides tuberculatus; Physa acuta; Physa marmorata; Pomacea sordida and Pomacea sp. As to the snail hosts of Schistosoma mansoni the most frequent species was B. tenagophila, found in all municipalities surveyed, except Parati. Besides new records the present study extends the distribution of B. peregrina and B. straminea in the state. No specimens were found harbouring larval forms of S. mansoni although different kinds of cercariae had been observed. An account about the current schistosomiasis transmission sites in this Mesoregion is presented as well.     

Miracidia of an Egyptian strain of Schistosoma mansoni differentiate between sympatric snail species

The host-finding behavior of miracidia of 2 strains of Schistosoma mansoni from Egypt and Brazil was studied by recording their responses to snail-conditioned water (SCW) from the Egyptian sympatric snails, Biomphalaria alexandrina, Physa acuta, Lymnaea cailliudi, and Balinus truncatus, as well as from Biomphalaria arabica and Biomphalaria glabrata. Miracidia of the Egyptian strain significantly preferred SCW from their compatible hosts B. alexandrina and B. arabica and showed no or a weak response to SCW from the other sympatric species, whereas miracidia of the Brazilian strain did not differentiate between SCW from different snail species.     

北京发现尖膀胱螺

尖膀胱螺(Physa acuta)为世界性广布淡水螺类,系多种重要寄生虫如广州管圆线虫(Angiostrongylis cantonensis)和卷棘口吸虫(Echinostoma revolutum)的中间宿主.在20世纪70年代淡水贝类调查中,北京地区未曾发现该螺的分布.2007年笔者在北京地区开展主要寄生虫流行病学调查,在朝阳公园、玉渊潭、圆明园及奥运村附近河流中相继发现该螺,此螺入侵北京地区并大量孳生应引起相关部门高度重视.     

Life-cycle of Euparyphium albuferensis n. sp. (Trematoda: Echinostomatidae) from rats in Spain

The morphology of the different life-history stages and life-cycle of Euparyphium albuferensis are described and drawn. The freshwater snail Gyraulus chinensis (Gastropoda: Planorbidae) serves as the natural and experimental first intermediate host. This and other freshwater snails, such as Lymnaea truncatula, L. peregra, L. palustris and Physa acuta, serve as second intermediate hosts. Adult worms, possessing 45 collar spines, were obtained naturally from Rattus norvegicus and R. rattus, and experimentally from albino rats, mice and golden hamsters. Chickens, ducks and pigeons were not suitable experimental definitive hosts. E. albuferensis differs from the most closely related species, E. murinum Tubangui, 1931, in its larger body, suckers and oesophageal measurements, in the distribution of vitelline follicles and in the morphology of the collar spines.     

Multiple unfolding states of glutathione transferase from Physa acuta (Gastropoda [correction of Gastropada]: Physidae)

The equilibrium unfolding of the major Physa acuta glutathione transferase isoenzyme (P. acuta GST(3)) has been performed using guanidinium chloride (GdmCl), urea, and acid denaturation to investigate the unfolding intermediates. Protein transitions were monitored by intrinsic fluorescence. The results indicate that unfolding of P. acuta GST(3) using GdmCl (0-3.0M) is a multistep process, i.e., three intermediates coexist in equilibrium. The first intermediate, a partially dissociated dimer, exists at low GdmCl concentration (approximately at 0.7M). At 1.2M GdmCl, a dimeric intermediate with a compact structure was observed. This intermediate undergoes dissociation into structural monomers at 1.75M of GdmCl. The monomeric intermediate started to be completely unfolding at higher GdmCl concentrations (>1.8M). Unfolding using urea (0-7.0M) and acid-induced structures as well as the fluorescence of 8-anilino-1-naphthalenesulfonate in the presence of different GdmCl concentrations confirmed that the unfolding is a multistep process. At concentrations of GdmCl or urea less than the midpoints or at the midpoint pH (pH 4.2-4.6), the unfolding transition is protein concentration independent and involved a change in the subunit tertiary structure yielding a partially active dimeric intermediate. The binding of glutathione to the enzyme active site stabilizes the native dimeric state.     

Freshwater snails and schistosomiasis mansoni in the state of Rio de Janeiro, Brazil: VI--Noroeste Fluminense Mesoregion

In this paper, the last of a series dealing with the survey of freshwater gastropods of the state of Rio de Janeiro, the results of collections carried out in the Noroeste Fluminense Mesoregion from 2002 to 2005 are presented and revealed the occurrence of 20 species: Antillorbis nordestensis; Biomphalaria glabrata; B. straminea; B. tenagophila; Drepanotrema anatinum; D. cimex; D. depressissimum; D. lucidum; Ferrissia sp.; Gundlachia ticaga; Gundlachia sp.; Heleobia sp.; Idiopyrgus sp.; Lymnaea columella; Melanoides tuberculatus; Physa acuta; P. marmorata; Plesiophysa guadeloupensis; Pomacea lineata; and Pomacea sp. Concerning the snail hosts of schistosomiasis the three natural vectors were identified and, although no specimens were found harbouring larval forms of Schistosoma mansoni, different kinds of cercariae had been observed.     

Planorbidae, lymnaeidae and physidae of Argentina (mollusca: basommatophora)

In the course of several trips to Argentina I had the opportunity of collecting specimens of Acrorbis petricola Odhner,1937, Biomphalaria orbignyi Paraense, 1975, B. peregrina (Orbigny, 1835), B. tenagophila (Orbigny, 1835) Lymnaea viatrix Orbigny, 1835, Antillorbis nordestensis (Lucena, 1954), B. intermedia (Paraense & Deslandes, 1962), B. oligoza Paraense, 1974, B. straminea (Dunker, 1848), Drepanotrema anatinum (Orbigny, 1835), D. cimex (Moricand, 1837), D. depressissimum (Moricand, 1837), D. heloicum (Orbigny, 1835), D. kermatoides (Orbigny, 1835), D. lucidum (Pfeiffer, 1839), L. columella Say, 1817, Physa acuta Draparnaud, 1805, and P. marmorata Guilding, 1828.     

Unusual snail species involved in the transmission of Fasciola hepatica in watercress beds in central France

Four freshwater pulmonate species (Lymnaea ovata, L. stagnalis, Physa acuta, Planorbis leucostoma) were living in several watercress beds known for their relationships with human cases of fasciolosis, whereas L. truncatula was never found. The aims of these studies were to determine the prevalence of natural infections with Fasciola hepatica in snails and to verify if these species might ensure the full larval development of this trematode (with cercarial shedding) when they were experimentally subjected to F. hepatica only, or to co-infections with an other trematode species. Investigations were so carried out in six snail populations living in watercress beds (including three for P. acuta) and in four others originating from three brooks or a pond (as controls). Snails naturally infected with F. hepatica were found in two watercress beds inhabited by L. ovata (prevalence of infection: 1.4%) and P. leucostoma (0.1%), respectively. The L. ovata from the watercress bed could be infected at a higher size than those from the control population and the prevalence of this infection was greater in the bed population. Similar findings were noted for L. stagnalis. Despite single or dual infections, the results obtained with the four populations of P. acuta were unsuccessful. In contrast, the co-infections of young P. leucostoma with Paramphistomum daubneyi and F. hepatica resulted in the shedding of some F. hepatica cercariae. According to the authors, the occurrence of fasciolosis in these watercress beds would be the consequence of frequent natural encounters between parasite and snails (L. ovata, L. stagnalis), or of co-infections with P. daubneyi and F. hepatica (P. leucostoma). In watercress beds only colonized by P. acuta, a lymnaeid species would have ensured the larval development of F. hepatica but it would have been eliminated by P. acuta, as this last species was known to be invasive and could colonize open drainage ditches on siliceous soil.     

Dyssymmetrical cytotomy and orientation of the spindles in early isolated blastomeres of gastropod molluscs]

While removing the vitelline membrane mechanically or by trypsinization, one or two blastomeres were isolated from two-, four- and eight-celled embryos Lymnaea stagnalis, Physa fontinalis and Ph. acuta. If a pair of blastomeres was isolated prior to the formation of the III and IV cleavage spindles, it became similar to a two-cell embryo; the spindles oriented in parallel to each other and the contact zone of blastomeres preserving the previous localization of the nuclei and the subsequent division was equal. If a pair of blastomeres was isolated in metaphase, the localization of spindles did not change and the relative size of sister blastomeres after the subsequent division resembled the normal size (in particular, the III division was unequal). In the course of division of isolated single blastomeres, as well as pairs of blastomeres with parallel spindles, mutual turns of sister cells along the plane of new furrow, always dexiotropic in Lymnaea and laetropic in Physa, were observed in all cycles. The ability of dissymmetrical invariant turns during cytotomy, shown earlier when studying the whole embryos, is, thus, inherent to each blastomere irrespective of the neighbour ones but is supressed during the normal development after the III division mechanically due to the dense cellular packing projected by the orientation of spindles.     

Environment-dependent inbreeding depression in a hermaphroditic freshwater snail

Inbreeding depression was simultaneously studied under contrasted environments, laboratory and natural conditions, using individuals originating from 14 families of the freshwater snail Physa acuta. Both survival and growth of juveniles showed inbreeding depression under laboratory conditions. The same fitness components were monitored with mature snails either kept under laboratory conditions or released at a natural site and analysed using capture-mark-recapture models. Genetic composition of both samples was similar. Inbreeding depression on survival was highest in the laboratory while strong outbreeding depression was revealed in the field. Thus inbreeding depression may not be always higher under natural conditions, at the opposite of what is commonly assumed. We suggest that inbreeding depression is dependent on metabolic requirements imposed by the environment. Other evidences showing that inbreeding depression is environment-dependent are reviewed. We conclude that genetic models should include both genetic and environmental variance in inbreeding depression for studying mating system evolution.