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PubMedDate not supplied

Influence of temperature on survival, growth and fecundity of the freshwater snail Indoplanorbis exustus (Deshayes).

To note the effect of temperature on survival, growth and fecundity, newly hatched (zero day old) snails Indoplanorbis exustus were cultured at 10 degrees, 15 degrees, 20 degrees, 25 degrees, 30 degrees and 35 degrees C constant temperatures and room temperature (17.5 degrees-32.5 degrees C). Individuals exposed to 10 degrees C died within 3 days while those reared at 15 degrees, 20 degrees, 25 degrees, 30 degrees, 35 degrees C and room temperature survived for a period of 6, 27, 18, 16, 12 and 17 weeks respectively. An individual added on an average 0.21 mm and 0.45 mg, 0.35 mm and 7.94 mg, 0.63 mm and 15.5 mg, 0.81 mm and 27.18 mg, 1.07 mm and 41.48 mg and 0.78 mm and 31.2 mg to the shell diameter and body weight respectively at those temperatures per week. The snails cultured at 15 degrees C died prior to attainment of sexual maturity. On an average, an individual produced 31.9 and 582.77, 54.86 and 902.18, 56.01 and 968.45, 49.32 and 798.68 and 62.34 and 1143.97 capsules and eggs respectively at 20 degrees, 25 degrees, 30 degrees, 35 degrees C and room temperature (17.5 degrees-32.5 degrees C).

Animals↗
PubMedDate not supplied

Molluscicide control of snail vectors of schistosomiasis.

A review of the methodology recommended by the World Health Organization for the use of molluscicides for the control of snail vectors of schistosomiasis is presented. Discussion of the principle molluscicides used, their advantages and disadvantages, the techniques and equipment required for their application and evaluation of effect as well as the biological control of snails is included.

Animals↗
PubMed2002

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 </= 3 mm size classes respectively. In the remaining trials predation rate varied from zero to eight (average 2.3) individuals per predator per day. In experiments with P. acuta belonging to all the size classes supplied together, none, except the first instar S. rusticum, attacked the prey individuals belonging to the lowest (</= 3 mm) size class. The first and second instar S. rusticum, in both trials did not attack P. acuta larger than 4 mm and 5 mm in shell length respectively. The water bugs belonging to the third, fourth, fifth instar and adult stages though preyed upon P. acuta with 3.1-8 mm shell length. The average rate of predation by a single S. rusticum varied from 0.14-3.08 individuals per day depending upon the size of P. acuta and the stage of S. rusticum. A single S. rusticum, irrespective of instar and adult stages, destroyed on average 4.16 P. acuta daily irrespective of sizes. It is estimated that one S. rusticum could destroy 1,360 P. acuta in its life time. The results clearly indicate that the water bug S. rusticum may be used to control the snails P. acuta.

Analysis of Variance↗
PubMed2005

The annual reproductive cycle of the snail Megalobulimus abbreviatus (Bequaert, 1948) (Gastropoda, Pulmonata).

Morphological changes in the sexual organs of the pulmonates were observed throughout a year and correlated with reproductive-cycle periods. Reproductive-organ weights of the snail Megalobulimus abbreviatus were recorded seasonally and gonad sections were analyzed morphologically. The weights were used to obtain the organosomatic index. Mean oocytic diameter and oocytic maturation index were based on gonad sections. It was concluded that M. abbreviatus is an iteroparous snail whose annual reproductive cycle is characterized by mating and egg laying throughout spring and early summer, and also by reproductive system preparation, occurring over the remainder of the summer until the end of winter, for a new breeding season.

Animals↗
PubMed2000

Snail size as a determinant of prepatent period duration in Helisoma anceps infected with Halipegus occidualis (Digenea: Hemiuridae).

Pulmonate snails (Helisoma anceps) of varying sizes were exposed to 2, 4, 8, or 16 eggs of Halipegus occidualis and observed over several months to determine the duration of the prepatent period. Infection probability was positively correlated with number of eggs ingested. The number of eggs ingested did not, however, have a significant effect on the duration of the prepatent period, presumably because low infectivity of the eggs (15%) dictated that most patent infections arose from a single miracidium. There was a significant, positive correlation between snail length (measured at time of exposure) and duration of prepatent period, suggesting that density-dependent effects are, in part, responsible for the initiation of cercariae production in H. occidualis.

Animals↗
PubMed2001

Physid snails as sentinels of freshwater nematomorphs.

Freshwater nematomorphs, or gordiids, are parasitic as larvae, but free-living in aquatic environments as adults. Studies based on the collection of adults have reported gordiids to be widespread, but discontinuous in distribution. However, a relatively short adult life span and unknown life history make the detection of adults difficult. An alternative approach to investigate gordiid distribution is to use cysts. Of all paratenic hosts, snails were chosen because they lacked internal defense reactions to the cysts and become easily infected. Here, it is reported that the occurrence of gordiids on the basis of the cyst stage is much more common than previously reported, thus altering the perception of how common these worms are. Using this modified survey procedure, gordiid cysts were found at 70% of sites examined, in an area where extensive sampling over 3 yr yielded adults only at a single site. Of 1,000 snails dissected, 395 were infected with gordiids (intensity range: 1-465). Furthermore, different types of human-modified landscapes did not affect gordiid distribution, suggesting that as urban and suburban areas sprawl, human encounters or pseudoparasitism with nematomorphs may increase. The results of this study indicate that use of organismal-specific sampling techniques can be critical in studies of parasite distribution and biodiversity.

Animals↗
PubMed2006

Extremely high secondary production of introduced snails in rivers.

The functional importance of invasive animals may be measured as the degree to which they dominate secondary production, relative to native animals. We used this approach to examine dominance of invertebrate secondary production by invasive New Zealand mudsnails (Potamopyrgus antipodarum) in rivers. We measured secondary production of mudsnails and native invertebrates in three rivers in the Greater Yellowstone Area (Wyoming, USA): Gibbon River, Firehole River, and Polecat Creek. Potamopyrgus production was estimated by measuring in situ growth rates and multiplying by monthly biomass; native invertebrate production was estimated using size frequency and instantaneous growth methods. Mudsnail growth rates were high (up to 0.06 d(-1)) for juvenile snails and much lower for adult females (0.003 d(-1)). Potamopyrgus production in Polecat Creek (194 g x m(-2) x yr(-1)) was one of the highest values ever reported for a stream invertebrate. Native invertebrate production ranged from 4.4 to 51 g x m(-2) x yr(-1). Potamopyrgus was the most productive taxon and constituted 65-92% of total invertebrate productivity. Native invertebrate production was low in all streams. Based on a survey of production measures from uninvaded rivers, the distribution of secondary production across taxa was much more highly skewed toward the invasive dominant Potamopyrgus in the three rivers. We suggest that this invasive herbivorous snail is sequestering a large fraction of the carbon available for invertebrate production and altering food web function.

Animals↗
PubMed2005

Probabilistic risk assessment for snails, slugs, and endangered honeycreepers in diphacinone rodenticide baited areas on Hawaii, USA.

Three probabilistic models were developed for characterizing the risk of mortality and subacute coagulopathy to Poouli, an endangered nontarget avian species, in broadcast diphacinone-baited areas on Hawaii, USA. For single-day exposure, the risk of Poouli mortality approaches 0. For 5-d exposure, the mean probability of mortality increased to 3% for adult and 8% for juvenile Poouli populations. For Poouli that consume snails containing diphacinone residues for 14 d, the model predicted increased levels of coagulopathy for 0.42 and 11% of adult and juvenile Poouli populations, respectively. Worst-case deterministic risk characterizations predicted acceptable levels of risk for nonthreatened or endangered species such as northern bobwhite quail and mallards. Also, no acute toxicity was noted for snails and slugs that feed on diphacinone baits.

Animals↗
PubMed2006

Role of sediment organic matter quality and feeding history in dietary absorption and accumulation of pyrene in the mud snail (Hydrobia ulvae).

Organic matter (OM) input to marine sediments varies seasonally both in quantity and quality. Because sedimentary OM (SOM) constitutes food for many benthic organisms, its properties should affect the dietary uptake of sediment-associated contaminants. We explored the effect of SOM quality/food value on short- and long-term pyrene accumulation in the mud snail (Hydrobia ulvae) and performed dual-tracer pulse-chase experiments to investigate the feeding mechanisms driving dietary pyrene uptake. The quality of the SOM was manipulated by enriching sediments either with high-quality microalgae or low-quality lignin, adding equal amounts of total organic carbon. Long- and short-term bioaccumulation increased with increasing SOM quality, as did pyrene ingestion rate (IR(pyr)), which also was affected by feeding history. By feeding selectively, snails concentrated pyrene 10-fold in ingested compared to ambient sediment, independent of SOM quality. Average pyrene absorption efficiency (AE(pyr): -65%) varied inversely with SOM quality and IR(pyr). Both AE(pyr) and gut passage time (alpha 1/IR(pyr)) agreed with theoretical models incorporating the time-dependence of absorption efficiency. Thus, SOM quality moderates dietary contaminant uptake in deposit feeders, and in H. ulvae, this occurs via OM-induced alterations of ingestion rate. Consequently, enhanced sediment-associated contaminant uptake is predicted for deposit feeders following phytoplankton blooms, principally because of OM quality-driven increases in the ingestion rate.

Animal Feed↗
PubMed2001

The garden snail (Helix aspersa) as a bioindicator of organophosphorus exposure: effects of dimethoate on survival, growth, and acetylcholinesterase activity.

The garden snail (Helix aspersa) is currently used as bioindicator of metallic pollution. Our objective was to extend its use to organic chemicals by studying the effects and tissue concentrations of the organophosphorus pesticide dimethoate following dietary uptake. After exposure for four weeks to increasing doses of pesticide in the diet, the median lethal concentration (LC50) was determined to be 3,700 microg/g food. Clinical signs indicated a no-observed-effect concentration of 100 microg/g and a lowest-observed-effect concentration of 250 microg/g. The growth parameters were decreased with increasing exposure to the pesticide. The median effective concentration (EC50), which was evaluated based on both shell diameter and dry weight inhibitions, was 665 and 424 microg/g, respectively, and the EC10 was 180 and 145 microg/g, respectively. Accumulation in the viscera was related to the amount of dimethoate in the food. The bioconcentration factors were low (>6 x 10(-3)). Acetylcholinesterase (AChE) activity was strongly decreased (80% from 250 microg/g). In conclusion, we demonstrated that the species H. aspersa could be a useful sentinel organism for organophosphorus contamination surveys. Among the effects measured, the inhibition of AChE activities and clinical signs were the most sensitive, followed by the growth parameters. These results confirm the suitability of the garden snail for development of sublethal toxicity tests using primary consumers and aboveground organisms.

Acetylcholinesterase↗
PubMed2003

Phylogenetic relationships between the tideland snails Batillaria flectosiphonata in the Ryukyu Islands and B. multiformis in the Japanese Islands.

Phylogenetic relationships between two sibling species of Japanese tideland snails, namely, Batillaria multiformis from the Japanese Islands and B. flectosiphonata from the Ryukyu Islands, were analyzed on the basis of the nucleotide sequences of the mitochondrial gene for cytochrome oxidase I. Populations of B. multiformis were genetically distinct from those of B. flectosiphonata with the exception of a population from Amami-Oshima Island, which corresponded to the boundary between the distributions of these two species. Individuals with the mitochondrial gene of B. multiformis and those with the mitochondrial gene of B. flectosiphonata were collected from the same tidal flat on Amami-Oshima Island. All the snails with the mitochondrial gene of B. multiformis could be divided into two genetically distinct groups but there was no geographical structure to the distribution of these two groups. Individual populations of B. flectosiphonata in the Amami, Okinawa, Miyako and Yaeyama insular groups each consisted exclusively of a unique set of haplotypes, with the exception of a population at a northern site on Okinawajima Island, which included a few individuals with sequences related to those of individuals in the Amami insular group. All individuals from South Ryukyu formed a well-supported monophyletic group, while the monophyly of individuals from Central Ryukyu was not supported. The monophyly of B. multiformis was clearly demonstrated but there was no evidence to support that of B. flectosiphonata. Batillaria multiformis might have been derived from immigrants from the Ryukyu Islands, which became isolated and diverged genetically on the Japanese Islands.

Animals↗
PubMed1978

Hyperpolarization caused by external high potassium in snail neurons.

Two-thirds of the tested subesophageal ganglion cells of Japanese snail, Euhadra peliomphala, was hyperpolarized when they were perfused by high K-Ringer. This hyperpolarization was accompanied with a marked decrease in membrane resistance and was independent of cell types classified by ACh-induced response. Pentobarbital was found to convert high K-induced hyperpolarization into depolarization, or to augment K-depolarization. The high K-induced hyperpolarization was considered as the result of summated IPSP's elicited by the presynaptic inhibitory fibers which were primarily depolarized by high K. Pentobarbital may remove this synaptic inhibition and disclose the original K-depolarization underlying the cell. In Cl-free media, high K caused a marked depolarization instead of hyperpolarization, or augmented the depolarization observed in normal Ringer. This suggested that the subsynaptic membrane became permeable to Cl ions during the inhibitory presynaptic activity when high K was applied. ACh was found not to be responsible for this synaptic inhibition, because d-tubocurarine, which is known to block the Cl-dependent ACh response of the snail neurons, did not affect the high K-induced hyperpolarization. The possibility of indirect action of high K on the membrane potential through synaptically mediated inhibition was discussed as a cause of its hyperpolarizing effect.

Acetylcholine↗
PubMed1996

Action of the herbicide butachlor on cholinesterases in the freshwater snail Pila globosa (Swainson).

Butachlor action on acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) activates in central nervous tissue of the snail Pila globosa was assayed following the method of ELLMAN et al1, in vitro by adding butachlor directly (10-100 mu moles), to tissue homogenates and in in vivo by exposing the snails to sub-lethal concentration (26.6 ppm) and taking out the tissue for experimentation at different intervals (3, 6, 12, 24 and 48 h) of exposure. The enzyme activities decreased in a dose-dependent manner in vitro, and up to 12-24 h in vivo after which they showed recovery towards the control. The inhibition of cholinesterases by butachlor in vitro indicates a direct action of the herbicide on these enzymes. Presumably butachlor exercises its neurotoxic effects through cholinergic impairment in a way similar to that of organophosphates and carbamates.

Acetanilides↗
PubMed1996

Waste yield, proximate and mineral composition of three different types of land snails found in Nigeria.

Some aspects of the chemical and anatomical weight composition of land snails in Nigeria were analysed with a view to assessing the waste yield, carcass yield and their nutritional evaluation on wet weight basis. Proximate analysis of Archachatina, Archatina and Limicolaria species was carried out on the carcass. Moisture and protein contents were high in all samples, fat and ash contents were generally low while crude fibre was not detected. The concentrations of iron, copper, zinc, manganese, sodium, calcium, magnesium, potassium and cobalt were determined in the carcass. Values of iron, calcium, magnesium, sodium and potassium were consistently high while both chromium and cobalt were not detected. Anatomical fractionation showed the shell to vary between 17.12 - 31.99%, carcass varied between 36.97 - 45.14% and the intestine varied between 18.80 - 22.74%. Snails interact with man in a variety of ways, the beneficial interactions are enumerated.

Animals↗
PubMed2002

Enzootic Angiostrongylus cantonensis in rats and snails after an outbreak of human eosinophilic meningitis, Jamaica.

After an outbreak in 2000 of eosinophilic meningitis in tourists to Jamaica, we looked for Angiostrongylus cantonensis in rats and snails on the island. Overall, 22% (24/109) of rats harbored adult worms, and 8% (4/48) of snails harbored A. cantonensis larvae. This report is the first of enzootic A. cantonensis infection in Jamaica, providing evidence that this parasite is likely to cause human cases of eosinophilic meningitis.

Angiostrongylus cantonensis↗
PubMed2001

Increase in number and size of kidney concretions as a result of PCP exposure in the freshwater snail Planorbarius corneus (Gastropoda, Pulmonata).

Molluscan kidneys are able to excrete solids in the urine in the form of concretions. It is thought that increased formation of these concretions occur under pollutant, environmentally or reproductive induced stress. This study examined the formation of concretions in the kidney of the freshwater snail Planorbarius corneus L. experimentally exposed to pentachlorophenol (PCP). Light microscopic histopathological analysis of the PCP-exposed P. corneus revealed significantly enhanced production of the kidney concretions when compared to the kidneys of control individuals. Measurements of the number of kidney concretions, the apparent area of the concretions, and the epithelial area filled with concretions indicated an increase in the number and size of concretions in all treated snails. Lipofuscin content of excretory cell concretions was detected.

Animals↗
PubMed1993

Killing effect of gamma irradiation on Angiostrongylus cantonensis in snails.

Cobalt-60 gamma irradiation was used to kill the larvae of Angiostrongylus cantonensis in four groups of snails that were irradiated at a rate of 15.4 Gy/min for 16.23 min (0.25 kGy), 32.47 min (0.50 kGy), 48.70 min (0.75 kGy), and 64.94 min (1.00 kGy), respectively. Third-stage (infected stage) larvae were isolated from these snails and 50 were administered to each experimental animal via an esophageal tube. At a dosage of 0.25 kGy, the mean +/- SD number of worms recovered from 30 rats and 30 mice was 15.6 +/- 6.5 and 11.3 +/- 6.2, respectively. These were significantly different from the number of worms recovered from the nonirradiated (control) groups, which were 28.9 +/- 9.6 (P < 0.05) and 16.6 +/- 10.3 (P < 0.05) for rats and mice respectively. Worms and cellular infiltrations in lung tissue of rats were histopathologically identified in the 0.25-kGy-irradiated group as well as in the control group. Worms and eosinophilic meningitis were also noted in the brain tissue of mice in control groups. No worms or pathologic findings were observed in the heart, lung, or brain tissue of rats or mice infected with larvae irradiated at or exceeding 0.50 kGy. It is therefore concluded that a dosage of 0.50 kGy is sufficient to prevent successful infection in mice and rats.

Angiostrongylus cantonensis↗
PubMed2004

Genetic diversity and molecular markers in introduced and Thai native apple snails (Pomacea and Pila).

The genetic diversity and species-diagnostic markers in the introduced apple snail, Pomacea canaliculata and in the native Thai apple snails; Pila ampullacea, P. angelica, P. pesmei, and P. polita, were investigated by restriction analysis of COI and are reported for the first time. Twenty-one composite haplotypes showing non-overlapping distributions among species were found. Genetic heterogeneity analysis indicated significant differences between species (P < 0.0001) and within P. pesmei (P < 0.0001) and P. angelica (P < 0.0004). No such heterogeneity was observed in Pomacea canaliculata (P > 0.0036 as modified by the Bonferroni procedure), P. ampullacea (P = 0.0824-1.000) and P. polita (P = 1.0000). A neighbor-joining tree based on genetic distance between pairs of composite haplotypes differentiated all species and indicated that P. angelica and P. pesmei are closely related phylogenetically. In addition, the 16S rDNA of these species was cloned and sequenced. A species-specific PCR for P. canaliculata was successfully developed with a sensitivity of detection of approximately 50 pg of the target DNA template. The amplification of genomic DNA (50 pg and 25 ng) isolated from the fertilized eggs, and juveniles (1, 7, and 15 d after hatching) of Pomacea canaliculata was also successful, and suggested that Pomacea canaliculata and Pila species can be discriminated from the early stages of development.

Animals↗