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At least 1,261 records · Page 70Linked to original sources
PubMed1992

Effect of testosterone on the ovotestis of the land snail Theba pisana.

The effect of testosterone on the histological pattern of the gonads of the land snail Theba pisana was studied. It was found that testosterone accelerated spermatogenesis, as indicated by the large increase in the number of spermatozoa and the decrease in the number of primary spermatocytes. The diameter of the acini in treated snails was greater than in the normal controls. Conversely, testosterone led to reduction of the number of mature ova.

Animals↗
PubMed2003

Evolutionary implications of a high selfing rate in the freshwater snail Lymnaea truncatula.

Self-compatible hermaphroditic organisms that mix self-fertilization and outcrossing are of great interest for investigating the evolution of mating systems. We investigate the evolution of selfing in Lymnaea truncatula, a self-compatible hermaphroditic freshwater snail. We first analyze the consequences of selfing in terms of genetic variability within and among populations and then investigate how these consequences along with the species ecology (harshness of the habitat and parasitism) might govern the evolution of selfing. Snails from 13 localities (classified as temporary or permanent depending on their water availability) were sampled in western Switzerland and genotyped for seven microsatellite loci. F(IS) (estimated on adults) and progeny array analyses (on hatchlings) provided similar selfing rate estimates of 80%. Populations presented a low polymorphism and were highly differentiated (F(ST) = 0.58). Although the reproductive assurance hypothesis would predict higher selfing rate in temporary populations, no difference in selfing level was observed between temporary and permanent populations. However, allelic richness and gene diversity declined in temporary habitats, presumably reflecting drift. Infection levels varied but were not simply related to either estimated population selfing rate or to differences in heterozygosity. These findings and the similar selfing rates estimated for hatchlings and adults suggest that within-population inbreeding depression is low in L. truncatula.

Alleles↗
PubMed2003

Diagnosis of Fasciola gigantica in snail using the polymerase chain reaction (PCR) assay.

The 124-bp repetitive and highly abundant DNA sequence--used as a specific probe for the detection of Fasciola hepatica infection in snails--was tested in the detection of F. gigantica infection in Lymnaea natalensis. The probe did not show any positive PCR results with Lymnaea natalensis, Physa acuta, Biomphalaria alexandrina and Bulinus trucatus or with Schistosoma mansoni, S. haematobium and Echinostoma liei. However, the probe was found capable to detect F. gigantica infection within L. natalensis at very early stages of the prepatent period and at very low concentrations. Thus, the present assay is specific and sensitive for the detection of F. gigantica within its intermediate host. It confirmed the idea that 124-bp repetitive and highly abundant DNA sequence in Fasciola sp. genome could be used as an epidmiological tool for examination of fasciolosis intermediate host. The nucleic acid-based assay could eliminate both inherent uncertainties and lengthy periods of time required for visual examination of the snails. Also, the assay is valuable in epizootiology of F. gigantica, vector suitability and host-parasite relationship.

Animals↗
PubMed2003

[Effect of 6-hydroxydopamine on the electrical characteristics of snail neurons in long-term sensitization].

Studies of the influence of neurotoxin 6-hydroxydopamine selectively destroying the catecholamine terminals on long-term sensitization, and the role of dopamine in manifestation of characteristics of a membrane of identified neurons during elaboration of plasticity, were fulfilled. Injection of saline was used as the control. It is shown that preliminary injection of 6-hydroxydopamine reduces duration of long-term sensitization, but does not block it completely. It was shown that injection of 6-hydroxydopamine prevents diminishing of membrane and threshold potentials in withdrawal interneurons during formation of long-term sensitization. The experiments demonstrate that shift of electrical characteristics of withdrawal interneurons caused by injection of neurotoxin 6-hydroxydopamine to both naive snails and sensitized snails, statys during at least 10 days.

Animals↗
PubMed2004

[Neuroeffector connections of multimodal neurons in the African snail (Achatina fulica)].

Using a new method of animal preparation, the efferent connections of giant paired neurons on the dorsal surface of visceral and right parietal ganglia of snail, Achatina fulica, were examined. It was found that spikes in giant neurons d-VLN and d-RPLN evoke postjunctional potentials in different points of the snail body and viscerae (in the heart, in pericardium, in lung cavity and kidney walls, in mantle and body wall muscles, in tentacle retractors and in cephalic artery). The preliminary analysis of synaptic latency and facilitation suggests a direct connections between giant neurons and investigated efferents.

Animals↗
PubMed1992

Biological control of the snail intermediate hosts of Schistosoma mansoni in Martinique, French West Indies.

In Martinique water-cress beds constituted the last transmission sites for schistosomiasis. The competitor snail, Melanoides tuberculata, was introduced at the beginning of 1983 to a group of water-cress beds and eliminated the snail hosts, Biomphalaria glabrata and B. straminea, in less than two years. Following this first success, M. tuberculata was introduced to the other groups of beds which were inventoried at the beginning of the eighties. At the present time, B. glabrata and B. straminea have totally disappeared from eight sites and only a few individuals have been recorded from 12 sites. The two remaining water-cress beds have dried up and were abandoned.

Animals↗
PubMed2004

Effect of nerve cell currents on MRI images in snail ganglia.

We performed extracellular potential recording with dissected snail ganglia inside an MRI scanner to investigate correlation between neuronal activity and MR image intensity. To increase neuronal activity we applied a nitric oxide donor, sodium-nitrosocystein, to the ganglia. The MR image intensity change in the ganglia region is correlated with the neuronal activity and was up to 5.49+/-1.94%. Since the snail has non-magnetic hemocyanins as oxygen carrying protein, it seems that the image intensity change is mainly due to the local magnetic fields produced by the neuronal currents.

Animals↗
PubMed2005

The effects of 6-hydroxydopamine on the electrical characteristics of snail neurons in long-term sensitization.

The effects of the neurotoxin 6-hydroxydopamine on the formation of long-term sensitization and changes in the membrane characteristics of identified neurons were studied. Injections of the neurotoxin 6-hydroxydopamine blocked the acquisition of long-term sensitization; when neurotoxin injections were given after the formation of long-term sensitization, they had no subsequent effect on conduction parameters. At the cellular level, recording of the electrical characteristics of common snail defensive behavior command neurons (LPa3, RPa3, LPa2, and RPa2) showed that the effects of 6-hydroxydopamine consisted of a small depolarization shift in the membrane potential and a change in the action potential generation threshold. Formation of long-term sensitization after injections of 6-hydroxydopamine did not lead to further decreases in the membrane and threshold potentials of command neurons as compared with snails only given injections of 6-hydroxydopamine. The changes in electrical measures of command neurons induced by administration of the neurotoxin 6-hydroxydopamine lasted at least two weeks.

Adrenergic Agents↗
PubMed2005

Food composition and feeding habits of some fresh water fishes in various water systems at Abbassa, Egypt, with special reference to snails transmitting diseases.

Study of feeding habits of freshwater fishes collected from ponds at World Fish Center (ICLARM) showed that the African catfish, Clarias gariepinus and Forskal catfish, Bagras bayad had the highest proportion of full stomachs (31-58% & 44-45% respectively). In cichlid fishes, the rate of full stomachs was much lower, being 0.0-12.5% and showed higher incidence of empty stomachs that varied from 37.5% for Oreochromis niloticus to 78.3% for Sarotherodon galilaeus. Food items were analyzed by the percentage of point assessment (P%), abundance (N%) and frequency of occurrence (F%). Results of the three methods of analyses (Index of relative importance, I.R.I) emphasized the importance of plants (1214.7) as a major food resource in the stomach of Nile tilapia, O. niloticus followed by shell fragments (628.5), whereas, snail soft bodies were the main food category in the diet of hybrid tilapia O. niloticus x O. aureus (2539.3). Shell fragments (652) and snail soft bodies (296.9) were the 1st in relative importance as foods of O. aurea. In case of S. galillae, shell fragments (338) came 2nd in I.R.I. after plants (559). Present investigation shows that shell fragments were represented by 11.1% and 15.1% in the diet of African catfish, C. gariepinus by (N%) and (P%) methods, however, they came as the second food item in its diet by I.R.I (1237.3). According to F% method, both shell fragments and Crustacea were present in the diet of C. gariepinus considerable proportions each of 47.4%. Shell fragments were represented by low proportions in the diet of B. bayad 3.9, 2.1 and 22.2 by N%, P% and F% respectively.

Animal Feed↗
PubMed2005

The molluscicidal activities of some Euphorbia milii hybrids against the snail Indoplanorbis exustus.

The objective of this study was to observe the molluscicidal activities of Euphorbia milli, known as "poysean" in Thailand, against Indoplanorbis exustus. Latex from 12 different E. milii hybrids was screened for its molluscicidal activities. Indoplanorbis exustus were exposed for 24 and 48 hours to the latex at various concentrations ranging from 6 to 25 ppm and mortality rates were recorded. Eight hybrids of latex were effective. The six most effective hybrids were E. milii Dang-udom, E. milii Arunroong, E. milii Raweechotchuong, E. milii Srisompote, E. milii Sri-umporn and E. milii Tongnopakun, which killed all snails after 24 hours of exposure. Under the same conditions, latex of E. milii Dowpraket and E. milii Promsatid killed 50% of the snails. Such results indicate that these 6 hybrids seem promising as natural molluscicidal agents.

Animals↗
PubMedDate not supplied

[Dynamic defensive and feeding reactions to the acquisition of sensitization in edible snails].

In snails changes of defensive and alimentary behaviour and of reactions of command and modulator neurones of these kinds of behaviour were studied during elaboration of sensitization. After a single action of 50% chinine solution on mollusc's head, a short-term (during 50-70 min) and long-term (hours or days) facilitation was found of animals defensive reactions and responses of command neurones of defensive behaviour to tactile and chemical sensory stimuli. Alimentary behaviour of the snails and reactions of modulator neurones of alimentary behaviour to carrot juice presentation were inhibited in sensitized animals. Dynamics differences of defensive responses to tactile and chemical stimuli in the same sensitized animals were observed. Short-term responses facilitation under sensitization correlated chiefly with depolarization of the membrane potential of defensive behaviour neurones and with an increase of plasmatic membrane excitability. Prolonged facilitation of responses was due mainly to a change of effectiveness of synaptic transmission. The described model of sensitization elaboration can be a base for studying of molecular-cellular mechanisms, underlying the learning.

Animals↗
PubMed1999

Compatibility in snail--fluke associations.

The compatibility of the species forming the fluke-snail complex is biochemical in nature. Trematode larvae are capable of modulating the immunological response of the host, while snails are capable of secreting substances affecting the mobility of the parasites invasive stages.

Animals↗
PubMed2006

[Study of determination method of trace elements in white jade snail].

The contents of six trace elements, Ca, Mg, Fe, Zn, Cu and Co, in white jade snail were determined by ICP-AES and AAS using nitrifying method of high pressure nitrifying pot. The results of two analysis methods were compared, showing no obvious differences. The recoveries were 92.4%-103.0%, and the relative standard deviations were less than 2.98%. The experiment proved that white jade snail contains rich useful trace elements, and is a kind of green food with high nutrition.

Animals↗
PubMed1991

[Development of a bioassay from gonadal cellular cultures of the snail Helix aspersa: influence of nerve ganglion extracts on the synthetic activity of the target cells].

To realize bioassays a primary culture method was carried out with dissociated cells from the garden snail gonads. ADN and protein syntheses of gonadal cells were estimated using the liquid scintillation method. The gonadal cells were obtained from either adults of Petits Gris and Gros Gris, or young Gros Gris. The results were remarkably homogeneous. The brain extracts added to the culture medium had an inhibitory dose dependent effect on the synthetic activity of gonadal cells. The effected bioassays permit quantitative estimation on the variations of the brain extracts effect in relation to the physiological states of the snail and on the evolution of target cells' receptors during the growth of Gros Gris.

Animals↗
PubMed1991

[Asynchronous development of the genital tract in the snail, Helix aspersa, during growth and reproduction].

During the growth of laboratory-raised Helix aspersa, the development of the albumen gland and spermoviduct was studied in relation to age, weight and different stages of reproduction such as mating and egg-laying. The results showed that the population can be divided into 2 categories because of different growth rates and asynchronous development of the genital tract. The fast-growing snails are larger and reach sexual maturity (female type maturity) in a shorter period than slow growing snails (male type maturity). During growth, the maturation of the genital tract was not directly proportional to the weight of the animal. Within each class of similar weight and age of population, 2 groups were identified; in one group, the genital tract was significantly less developed than in the other. This asynchrony of genital tract development could still be found between mating partners of the same weight, the genital tract could be 3 times smaller in one than in the other partner. However, this difference disappeared between mating and egg-laying. These observations suggest: that asynchronous development of the genital tract could be a strategy for the developing population of Helix aspersa; and that (a) mating factor(s) is (are) involved in the regulation of the growth and function of the genital tract.

Animals↗
PubMed1990

Detection of shared antigens of human liver flukes Opisthorchis viverrini and its snail host, Bithynia spp.

The relationship between Opisthorchis viverrini and its snail intermediate host including Bithynia funiculata, B. siamensis siamensis and B. siamensis goniomphalos was carried out on the correlation of shared antigens and infection rates. B. funiculata and B. s. siamensis were equally susceptible to O. viverrini with relatively high infection rates of 72.2% and 69.9% respectively whereas B. s. goniomphalos gave lowest percentage of infection of only 9.6%. By immunoelectrophoresis, crude extract of O. viverrini adult worm produced the same number of two common precipitin bands of four different electrophoretic mobilities against anti-B. funiculata and anti-B. s. siamensis sera and one precipitin band in the antigen well region against anti-B. s. goniomphalos serum. The three snail antigens produced the same number of two common precipitin bands against anti-O. viverrini serum.

Animals↗
PubMed1990

[Snail distribution and susceptible zones of schistosomiasis in endemic areas around Poyang Lake].

To understand the situation of snail distribution and to explore the criteria of susceptible zones of schisosomiasis in endemic areas around Poyang Lake, a total of 1,222,910 mu of marshland in lake regions were surveyed for three years from 1982 through 1984 by 400 skillful observers. This article reports the relation between mean density of infected snails and incidence of acute schistosomiasis in marshland. We divided all susceptible marshlands of Poyang Lake area into three types, and found that about one fourth of the area belongs to the first type of susceptible zones, i.e., with high risk to schistosomiasis infection. Longitudinal observation showed that the types of susceptible zones changed very little unless measures of schistosomiasis control were taken. The results of field study suggested that we should put stress of schistosomiasis control on the first type of susceptible marshlands of Poyang Lake in future.

Animals↗
PubMedDate not supplied

[Interrelations of the emotionally positive and negative areas of the brain in the edible snail].

Fine wire electrodes were surgically implanted in two regions of a snail's brain (Helix aspersa). To receive electrical stimulation of the brain, the tethered snail was required to displace the end of a rod. Self-stimulation delivered to the parietal ganglion resulted in nonrepetition of the operant response, whereas self-stimulation delivered to the mesocerebrum resulted in an increase in response frequency. In neurophysiological experiments it was found that extracellular stimulation of mesocerebrum inhibits spontaneous activity of serotonergic cells modulating avoidance reactions, and decreases synaptic input of a command cell for avoidance behaviour. These findings make possible intracellular investigations of the mechanisms of positive and negative reinforcement.

Animals↗