Showing papers on "Bulinus truncatus published in 1996"
TL;DR: Examination of the consequences of selfing and bottlenecks on genetic polymorphism using microsatellite markers in 14 natural populations of the hermaphrodite freshwater snail Bulinus truncatus revealed an unexpectedly high levels of genetic variation.
Abstract: Hermaphrodite tropical freshwater snails provide a good opportunity to study the effects of mating system and genetic drift on population genetic structure because they are self-fertile and they occupy transient patchily distributed habitats (ponds). Up to now the lack of detectable allozyme polymorphism prevented any intrapopulation studies. In this paper, we examine the consequences of selfing and bottlenecks on genetic polymorphism using microsatellite markers in 14 natural populations (under a hierarchical sampling design) of the hermaphrodite freshwater snail Bulinus truncatus. These population genetics data allowed us to discuss the currently available mutation models for microsatellite sequences. Microsatellite markers revealed an unexpectedly high levels of genetic variation with <=41 alleles for one locus and gene diversity of 0.20-0.75 among populations. The values of any estimator of F(is) indicate high selfing rates in all populations. Linkage disequilibria observed at all loci for some populations may also indicate high levels of inbreeding. The large extent of genetic differentiation measured by F(st), R(st) or by a test for homogeneity between genic distributions is explained by both selfing and bottlenecks. Despite a limited gene flow, migration events could be detected when comparing different populations within ponds.
82 citations
TL;DR: Results allow the definition of a self‐fertilization syndrome in hermaphrodite freshwater snails: selfing populations (such as those of B. straminea and B. truncatus studied here) are characterized by high selfing rates in spite of copulations, limited deleterious effects of selfing, limited neutral genetic polymorphism, and large heterozygote deficiencies.
Abstract: This paper examines the consequences of self-fertilization on life-history traits and neutral genetic polymorphism in natural populations of three species of hermaphrodite freshwater snails: Biomphalaria straminea, Bulinus globosus, and the aphallic species Bulinus truncatus. Life-history traits (fecundity, growth, hatching rate, and survival of offspring) are compared under laboratory conditions between isolated (obligatory selfing) and paired (outcrossing possible) snails in one population of B. straminea and B. globosus and two populations of B. truncatus. The genetic polymorphism of the same four populations is analyzed using electrophoretic markers in B. straminea and B. globosus and microsatellite markers in B. truncatus. In B. truncatus and B. straminea, isolated snails have a higher fecundity than paired snails, whereas the contrary is observed in B. globosus. For all populations, no difference in hatching rate and offspring survival is detected between the two treatments. Genetic analyses using microsatellite markers conducted in B. truncatus on progeny of paired snails reveal a high selfing rate in spite of high copulation rates, highlighting the difficulties of obtaining outcrossing in highly selfing snails. The high survival of selfed offspring in B. truncatus and B. straminea indicates that inbreeding depression is limited. The extent of inbreeding depression in B. globosus is less clear. Overall, fitness decrease in this species is limited to fecundity. The extent of allozyme polymorphism is very limited whereas a much higher variability is observed with microsatellites. Biomphalaria straminea and B. truncatus populations are also characterized by very low observed heterozygosities and large heterozygote deficiencies, whereas the B. globosus population does not exhibit such a deficiency. Overall these results allow the definition of a self-fertilization syndrome in hermaphrodite freshwater snails: selfing populations (such as those of B. straminea and B. truncatus studied here) are characterized by high selfing rates in spite of copulations, limited deleterious effects of selfing, limited neutral genetic polymorphism, and large heterozygote deficiencies.
59 citations
TL;DR: Snails that are produced from snails previously exposed to low doses were more sensitive to the tested extracts, which may give primary indication of no possibility of inherited resistance.
34 citations
TL;DR: This study tested whether a reallocation of resources from the lost male function to the female function occurs in aphallic snails at the level of both sex organs (sex allocation) and life-history traits.
Abstract: In the hermaphrodite freshwater snail Bulinus truncatus, two sexual morphs, euphallic (regular hermaphrodites) and aphallic individuals without a male copulatory organ, co-occur at various ratios in natural populations. Both aphallic and euphallic individuals can reproduce by selfing, but when outcrossing aphallic individuals can only play the female role. A comparison of life-history traits and sex allocation in these two forms provides the opportunity to investigate the evolution and maintenance of sexual polymorphisms. This study was performed to test whether a reallocation of resources from the lost male function to the female function occurs in aphallic snails at the level of both sex organs (sex allocation) and life-history traits. In a first experiment we compared life-history traits over a whole life-cycle under selfing between the two sexual morphs. In a second experiment, the sex organs were weighed to test for a difference in sex allocation between the two morphs. No difference in resource allocation to female function between the two morphs was observed in either experiment. This is in contrast to patterns frequently observed in sexually polymorphic plants, and in a previous study performed on aphally in the same snail species. We discuss the genetic and physiological hypotheses that could explain these results, and their consequences for the evolution and maintenance of phally polymorphism in B. truncatus.
19 citations
TL;DR: It is proposed that the sexual morph of an individual at a given temperature is determined by a temperature threshold value depending on both the individual genotype and probabilistic processes.
Abstract: In some species of self-fertile pulmonate snails, two sexual morphs co-occur in natural populations: regular individuals and aphallic individuals that cannot transmit sperm to other snails. Purely aphallic populations therefore reproduce obligatorily by selfing. Understanding the evolution of aphally and selfing in these snails requires a precise knowledge of phally determination. In this paper, we investigate the genetic and environmental determination of aphally in Bulinus truncatus by a survey of the family (offspring) aphally ratio of 233 individuals originating from seven natural populations and a study of the reaction norm of the family aphally ratio to temperature using 60 individuals from 10 selfed lineages of one population. Our results indicate a high genetic variability for the determination of aphally between populations and within some populations, associated with a high level of genetic determination. Our second experiment indicates a significant temperature and lineage effect though no interaction between these two effects. We discuss our results in the framework of threshold models developed for dimorphic traits with polygenic inheritance. We propose that the sexual morph of an individual at a given temperature is determined by a temperature threshold value depending on both the individual genotype and probabilistic processes.
18 citations
Journal Article•
TL;DR: Temperature variations, high amounts of organic material in water, high oxygen content inWater, and absence of plant-life are factors which could limit the development of the intermediate snail hosts in the waste stabilization ponds of the Interstate School of Rural Equipment Engineers in Ouagadougou, Burkina Faso.
Abstract: In subsaharan Africa wastewater purification to protect the health of the population could create stagnate water reservoirs for parasitic vectors such as snails which are intermediate hosts of bilharzia Laboratory studies of the survival of Bulinus truncatus, an intermediate host of Schistosoma haematobium, and Biomphalaria pfeifferi, an intermediate host of Schistosoma mansoni, in waste water purified in stabilization ponds showed that Biomphalaria pfeifferi thrives to dirty water (60 mg/l < or = COD < or = 1060 mg/l) while Bulinus truncatus survived only in slightly cleaner water (60 mg/l < or = COD < or = 200 mg/l) Field studies showed that Biomphalaria pfeifferi disappeared after 48 hours as compared to 25 days in the laboratory In both laboratory and field studies Bulinus truncatus survived only 24 hours in raw waste water The duration of survival grew longer as quality of the water improved Temperature variations, high amounts of organic material in water, high oxygen content in water, and absence of plant-life are factors which could limit the development of the intermediate snail hosts (ie Bulinus truncatus and Biomphalaria pfeifferi) in the waste stabilization ponds of the Interstate School of Rural Equipment Engineers in Ouagadougou, Burkina Faso
8 citations
TL;DR: The results indicate a strong genetic basis for aphally, with large genetic differences among populations and some genetic variability for Aphally within populations, and the adaptive and stochastic factors that may shape the distribution of the genetic variability are discussed.
Abstract: We investigated the genetic variability for phally polymorphism within and between natural populations of the hermaphrodite self-fertile freshwater snail Bulinus truncatus. Phally polymorphism is characterized by the co-occurrence in natural populations of regular hermaphrodite individuals (euphallic) and individuals deprived of the male copulatory organ (aphallic). The two morphs can both self-fertilize and outcross. However, aphallic individuals cannot outcross as males. We examined the variation of the aphally ratio in 22 natural populations from Niger over two successive years. During the second years, populations were sampled three times at 3 week intervals. The aphally ratio was highly variable among populations at a given sampling data and remained relatively stable over time. For 10 of these populations, one population from Corsica and two from Sardinia, we also estimated the between- and within- population variability, analysing the aphally ratio of 346 families under laboratory conditions. The aphally ratio varied significantly among populations and was highly correlated with the aphally ratio of the natural populations. Some within-population variability, associated with a high value of the broad sense heritability, was observed in four populations out of 13. In these populations, aphallic individuals produced significantly more aphallic offspring than euphallic individuals. Our results indicate a strong genetic basis for aphally, with large genetic differences among populations and some genetic variability for aphally within populations. We discuss the adaptive and stochastic factors that may shape the distribution of the genetic variability for aphally.
8 citations
TL;DR: It is concluded that the Namibian populations belong to a single species, B. tropicus, of which B. parietalis (Mousson, 1887) is probably a synonym, and lack of a potential intermediate host therefore precludes transmission of Schistosoma haematobium in this area.
Abstract: Freshwater snails collected in central Namibia, south-western Africa, from 15 populations belonging to the Bulinus truncatus/tropicus complex (Planorbidae) are characterised in respect of their chromosome number, morphology, egg proteins and enzymes. The population samples were all consistently diploid and euphallic. The findings are compared with observations on this group of snails in other areas of Africa. It is concluded that the Namibian populations belong to a single species, B. tropicus (Krauss, 1848), of which B. parietalis (Mousson, 1887) is probably a synonym. No evidence was found of any occurrence of the tetraploid species B. truncatus or of snails belonging to the B. africanus group; lack of a potential intermediate host therefore precludes transmission of Schistosoma haematobium in this area.
5 citations
01 Dec 1996
3 citations
Journal Article•
TL;DR: The two molluscicides affected more on the mortality of Biomphalaria alexandrina than Bulinus truncatus and Copper sulphate was more effective than Bayluscide on the fungal species of both snails.
Abstract: Biomphalaria alexandrina and Bulinus truncatus are the main vectors of human Bilharziasis in Egypt. The mycotic inhabitants of both control and treated snails were surveyed at 7 and 15 days intervals. The two molluscicides affected more on the mortality of Biomphalaria alexandrina than Bulinus truncatus. The highest population of zoosporic fungi was collected from Biomphalaria alexandrina, the lowest from Bulinus truncatus. Copper sulphate was more effective than Bayluscide on the fungal species of both snails. Achlya, Dictyuchus and Saprolegnia were the common genera while Leptolegnia caudata and Pythium ultimum completely missed from treated snails. The total colonies of zoosporic fungi were lowered after. 15 days of treatment. The two molluscicides inhibited the cell division of both tested snails.
3 citations
01 Jan 1996
TL;DR: In this paper, a study on the survivability of Bulinus truncatus, hote intermediaire de Schistosoma haematobium, and Biomphalaria pfeifferi dans les eaux usees epurees par lagunage is presented.
Abstract: En Afrique subsaharienne, l'epuration des eaux usees en vue de proteger la sante des populations pourrait conduire dans le cas de stagnation de ces eaux a la creation de gites de vecteurs de parasites tels que les mollusques hotes intermediaires de la bilharziose. L'etude en laboratoire sur la possible survie de Bulinus truncatus, hote intermediaire de Schistosoma haematobium, et de Biomphalaria pfeifferi, hote intermediaire de Schistosoma mansoni dans les eaux usees epurees par lagunage a montre que Biomphalaria pfeifferi s'adaptait facilement aux eaux chargees (60 mg/l≤demande chimique en oxygene≤1060 mg/l) alors que Bulinus truncatus ne survivait que dans les eaux moins chargees (60 mg/l≤demande chimique en oxygene≤200 mg/l). In situ, la cohorte de Biomphalaria pfeifferi a disparu au bout de 48 heures alors que cette duree etait de 25 jours en laboratoire. Que ce soit en laboratoire ou in situ, la cohorte de Bulinus truncatus n'a survecu dans les eaux usees brutes que pendant 24 heures. La survie devenait plus longue lorsque la qualite de l'eau s'ameliorait. La forte amplitude thermique, la charge organique de l'eau, la teneur en oxygene de l'eau, l'absence de vegetation sont des facteurs pouvant limiter le developpement des mollusques hotes intermediaires (Bulinus truncatus, Biomphalaria pfeifferi) dans les eaux des bassins de lagunage comme dans le cas du lagunage de l'Ecole Inter-Etats d'Ingenieurs de l'Equipement Rural de Ouagadoudou au Burkina Faso.
Journal Article•
TL;DR: The reproductive capacity of irradiated Biomphalaria and Bulinus snails was highly suppressed and this will interrupt Schistosomiasis transmission and the maximum survival periods of laboratory populations of Biomphaaria snails were less than those of field ones which means a high sensitivity of laboratory snails to X-ray.
Abstract: Biomphalaria alexandrina and Bulinus truncatus snails were exposed to sublethal doses 0.2, 3, 5, 10 and 20 rad of X-ray. The survival and reproductive rates of these snails were highly affected by these doses. The maximum survival periods of laboratory populations of Biomphalaria snails were less than those of field ones which means a high sensitivity of laboratory snails to X-ray. The reproductive capacity of irradiated Biomphalaria and Bulinus snails was highly suppressed and this will interrupt Schistosomiasis transmission. A deleterious effect of gametogenesis of irradiated Biomphalaria was histologically proved. After 3 weeks of snail irradiation with high dose (40 rad) the hermaphrodite gland became completely evacuated.
Journal Article•
TL;DR: Cercaria bulini I as mentioned in this paper is a distome cercaria with three pairs of penetration glands, 12 pairs of flame cells, and lacks the intestinal cecae.
Abstract: Bulinus truncatus snails collected from water bodies of the South Shuna region, north of the Dead Sea, were found infected with a pharyngeal longifurcate distome cercaria. This new form of cercaria is named Cercaria bulini I. It has three pairs of penetration glands, 12 pairs of flame cells, and lacks the intestinal cecae. This cercaria is an active swimmer and develops within an elongated sporocyst. Other details on the morphology, behavior, and development of C. bulini I are presented.
Journal Article•
TL;DR: A total of 1535 persons of different age, sex and occupation from 5 villages in Qalyoubia Governorate in Nile Delta were subjected to clinical, stool, urine and intradermal tests accompanied by a questionnaire, revealing decreased rates of schistosomiasis and snail infectivity.
Abstract: A total of 1535 persons of different age, sex and occupation from 5 villages (Tanan, El-Sad, Sandiun, Kalama and Taha-nob) in Qalyoubia Governorate in Nile Delta were subjected to clinical, stool, urine and intradermal tests accompanied by a questionnaire for 500 of them Snail vectors of Schistosome parasites were collected from 2 villages (El-Sad and Taha-nob) and snail densities in the waterways as well as the prevalence rate of infection with schistosomal cercariae were recorded The results revealed that the average prevalence rate of Schistosoma haematobium in the 5 cillages was 49% (range 23% - 71%) and that of S mansoni was 133% (range 114-144%) The overall prevalence of both types was 182% (range 137-214%) The average density of Biomphalaria alexandrina in the 2 village was 1647% and that of Bulinus truncatus was 75%, the ratio was 2:1 The infectivity with schistosomal cercariae was very low with an average of 25% in B Alexandrina and 15% in B truncatus Factors responsible for the decreased rates of schistosomiasis and snail infectivity were discussed
TL;DR: A new form of cercaria is named Cercaria bulini I, which has three pairs of penetration glands, 12 pairs of flame cells, and lacks the intestinal cecae and develops within an elongated sporocyst.
Abstract: Bulinus truncatus snails collected from water bodies of the South Shuna region, north of the Dead Sea, were found infected with a pharyngeal longifurcate distome cercaria. This new form of cercaria is named Cercaria bulini I. It has three pairs of penetration glands, 12 pairs of flame cells, and lacks the intestinal cecae. This cercaria is an active swimmer and develops within an elongated sporocyst. Other details on the morphology, behavior, and development of C. bulini I are presented.