Paramphistomum daubneyi: production dynamics and infectivity of metacercariae originating from snails dissected at regular intervals

Experimental infections of Galba truncatula with Paramphistomum daubneyi were carried out at 24 degrees C to study the dynamics of larval development in snails dissected at regular intervals and to determine if metacercarial production might be improved. When the shell height of snails (4, 5, 6 or 7 mm) at exposure increased (experiment A), the total number of metacercariae was significantly higher in the 6- and 7-mm snails than in the other two groups, and the differentiation period was shortened (the first cercariae encysted at day 35 post-exposure (p.e.) instead of day 40 in the 4- and 5-mm groups). When the number of miracidia (two, three or five) for each 6-mm high G. truncatula increased (experiment B), a significant decrease of snail survival at day 30 p.e., a significant augmentation of prevalence, and a significant increase of metacercarial production were noted. In the two- and three-miracidium groups, the number of metacercariae was close to that found in the 6-mm snails from experiment 1, whereas they showed slower growth from day 45 to day 65 in the five-miracidium group. In the two groups of lambs infected with metacercariae encysted at days 45 or 60 p.e., no difference in the numbers of adult worms was noted. In contrast, in the case of 35-day encysted larvae, the number of adult worms was clearly lower. Snail dissection allowed higher metacercarial production, a saving of 12-15 days at 24 degrees C to obtain these larvae, and a substantial decrease of their cost price for commercial production.     

The effect of some biological and physical factors on infection of Biomphalaria glabrata with Angiostrongylus cantonensis.

Several biological and physical factors which may influence infection of Biomphalaria glabrata snails with the first stage larvae of Angiostrongylus cantonensis were studied. These factors were: the size of snails, the number of first stage larvae to which snails were exposed, the age of larvae, individual exposure compared with mass exposure of snails, the length of exposure period and the effect of temperature and light. The results showed that young snails, 2 mm in diameter, became infected with significantly smaller numbers of third stage larvae than larger snails (4, 8, 12 and 16 mm). No significant differences in the intensity of infection were evident between the larger size groups. The number of third stage larvae recovered from snails was directly related to the number of first stage larvae to which the snails were exposed. The mean percentage recovery per snail was more or less constant regardless of the infective dose. First stage larvae showed a slight reduction in their survival rate within 7 and 4 days, at 24 degrees C and 26 degrees C respectively, after which a sharp decrease in their survival rate occurred. However, the infectivity of larvae was progressively reduced from the second day at these two temperatures. The mean intensity of infection in snails was independent of whether the infection was by mass or individual exposure. The average number of first stage larvae entering a snail was greatest during the first half hour of exposure, this decreased considerably during the second half hour, and thereafter the number of larvae which entered a snail was low. It was concluded that 26 degrees C was the optimal temperature for infection and that the presence or absence of light had no effect on the infection.     

Biology and conservation of the rare New Zealand land snail Paryphanta busbyi watti (Mollusca, Pulmonata)

Abstract. The biology of Paryphanta busbyi watti , an endangered carnivorous land snail, was studied mostly by following large juvenile and adult snails with harmonic radar. The snails are nocturnally active and most (79%) hide during the day under leaf litter or in dense vegetation. Fecal analysis showed that the diet is primarily earthworms, but some cannibalism of smaller snails occurs. Empty shells appear to be an additional source of dietary calcium. Mating occurred most frequently between April and July. Mating snails stayed together for 4–7 days, and each pair reversed their positions at least twice. Four snails were first found mating 151–1240 d after they acquired adult shells, and 7 snails were observed mating a second time after 66–298 d. We found 8 nests and observed 6 snails ovipositing; 5 snails laid eggs in holes they dug and one laid eggs in a crevice between rocks. In 2 instances, oviposition was recorded 52 and 140 d after mating. Snails were estimated to lay on average ∼17.5 eggs per year in 3–5 clutches. Most oviposition was observed in August/September, but some occurred between November and February. Of the snails that died, pigs killed 13.6% and humans inadvertently killed another 13.6%. Other snails died from unknown causes mostly during the drier and warmer months, from November to April. This large land snail survives in the presence of introduced predators, but some life history traits could predispose it to a rapid decline in numbers if new predators arrive.     

Effects of snail size and diet on encystment of Echinostoma caproni cercariae in juvenile Helisoma trivolvis (Colorado strain) and observations on survival of infected snails

The effects of snail size and diet on encystment of Echinostoma caproni cercariae in juvenile Helisoma trivolvis (Colorado strain) snails were studied. Encystment in neonatal (<1-mm shell diameter) and juvenile (2- to 3-mm shell diameter) snails was compared 24 hr postinfection (PI) after individual exposure of snails of each size to 1, 5, 10, 25, or 50 cercariae. Significantly more cysts were recovered from juvenile snails exposed to 10, 25, or 50 cercariae than from neonatals with comparable exposure. The maximum number of cysts recovered from juveniles exposed to 50 cercariae was 42, compared with a maximum of 15 cysts in neonatals comparably exposed. Size of H. trivolvis was a major factor in determining cyst burden in this planorbid. A diet of either Romaine lettuce leaf or hen's egg yolk did not have a significant effect on the number of cysts recovered at 24 hr PI from juvenile snails exposed to 25 or 75 cercariae. Survival of infected versus uninfected neonatals was also examined for 7 days. Neonatals exposed to 10 cercariae showed a significant decrease in survival at 6 and 7 days PI when compared with uninfected controls.     

Effects of snail size on encystment of Echinostoma caproni in juvenile Biomphalaria glabrata (NMRI strain) and observations on the survival of infected snails

The effects of snail size on encystment of Echinostoma caproni cercariae in neonatal and juvenile Biomphalaria glabrata (NMRI strain) snails were studied. Encystment in neonatal (0.7-1.1 mm shell diameter) and juvenile (2-3 mm shell diameter) snails was compared 24 h post-infection (PI) following individual exposure of snails of each size to 1, 5, 10, 25 and 50 cercariae. Significantly more cysts were recovered from juveniles exposed to 1, 5, 10 and 50 cercariae than from neonatals with comparable exposure. Size of B. glabrata was a major factor in determining cyst burden in this planorbid. Survival of infected versus uninfected neonatals and juveniles was also examined for 7 days. Neonatals exposed to 10 cercariae showed a significant decrease in survival at 3, 6 and 7 days PI when compared to the uninfected controls. There was no significant decrease in the survival of juveniles exposed to 10 cercariae compared to uninfected controls at any time point. Snail size was a factor in mortality associated with echinostome cercarial penetration and encystment.     

Effects of Schistosomatium douthitti infection on the growth, survival, and reproduction of Lymnaea catascopium

Lymnaea catascopium snails infected with Schistosomatium douthitti grew faster than uninfected control snails during the first 2 months postexposure, but thereafter grew more slowly, and by 8 months postexposure were significantly smaller. When reared in isolation, uninfected snails survived significantly longer (mean survival time, 515 days) than snails exposed to three miracidia each (400 days), which in turn survived longer than snails exposed to 10 miracidia per snail (223 days). When maintained in aquaria in contact with other snails, snails exposed to three miracidia each survived longer (227 days), but not significantly longer, than control snails (198 days). Production of large numbers of eggs by control snails grown under the latter conditions may account for their reduced survival. The ovotestes and accessory genitalia of snails infected with S. douthitti were much reduced in size in comparison with uninfected control snails. These effects were most pronounced in snails which had been infected for over 100 days. Egg production was normally totally inhibited if snails were infected before the onset of sexual maturity. If infected after the onset of maturity, eggs were produced only during the prepatent period.     

Leucocytosis in Biomphalaria glabrata sensitized and resensitized to Echinostoma lindoense

Leucocytosis was shown to occur in the pulmonate gastropod Biomphalaria glabrata exposed to the trematode Echinostoma lindoense. In these sensitized snails, the leukocyte count in the hemolymph was elevated 3 to 5 days postexposure to miracidia, and prior to complete encapsulation of sporocysts. This increase continued 1 to 5 days after destruction of sensitizing, irradiated E. lindoense sporocysts. Counts returned to normal levels after this period. A significant and more rapid increase in numbers of circulating leukocytes occurred 1 to 6 hr after reexposure of snails to a sensitizing dose of nonirradiated E. lindoense sporocysts. The leukocyte counts usually returned to normal levels after this period, except in snails in which some resensitizing sporocysts remained alive.     

Schistosomatium douthitti: effects of Lymnaea catascopium age on susceptibility to infection

Laboratory-reared Lymnaea catascopium snails (1–269 days old) were exposed individually to different numbers of Schistosomatium douthitti miracidia. Increasing the exposure dosage from 3 to 10 miracidia generally increased infection rates, in some age classes up to 100%. Successful re-exposure of snails not infected after a primary exposure was possible. Neonatal snails were least likely to become infected, primarily because miracidia were not attracted to them. Snails 12–55 days old were most susceptible to infection. Miracidia were readily attracted to these snails, and many were ingested and subsequently penetrated the host esophageal wall. Miracidial penetration of external snail surfaces was rare. Susceptibility of older snails (65–269 days) progressively declined with age. Many miracidia were entangled and immobilized in mucus produced by these snails, and fewer were ingested. No conspicuous host cellular responses to mother sporocysts were observed in any of the snails sectioned. A comparison of susceptibility of deliberately stunted snails and comparably aged controls of normal size indicated that the former were more susceptible.     

COPULATORY ACTIVITY AND SPERM PRODUCTION IN BULINUS (PHYSOPSIS) GLOBOSUS (GASTROPODA: PLANORBIDAE)

Young Bulinus (Physopsis) globosus performed male copulatoryactivity and cross-fertilized other snails before their femalereproductive tracts were mature. The two most immature snailsshowed preputial eversion when secretion was present only inthe muciparous gland and at the carrefour region of the oviduct.Sixteen snails showed preputial eversion and four snails cross-fertilizedother snails when their oothecal glands and/or major portionof the oviducts contained either no secretion or only scantyamounts. When paired with a partner snail for 12 or 20 consecutive days,adult snails copulated as males on approximately 60% of thedays paired and up to 8 consecutive days. Virgin snails raisedin isolation copulated as male at the same rate as non-virgin,community-raised snails. Ability to copulate as male was notdependent upon previous experience as male or female. Aftera single copulation as male after 7 days isolation, the hermaphroditicducts of maleacting snails contained 87 000 sperm. Sperm productionoccurred at approximately 50 000 sperm.d-¹, until at 10 dayspost-copulation, snails contained 639 000 sperm. (Received 25 May 1982;     

The effects of starvation and refeeding on egg laying and the synthetic activity of the albumen gland in Bulinus truncatus, a snail vector of urinary schistosomiasis

1. The effects of starvation (for 1, 2, 3, 6, 9 and 12 days, respectively) and refeeding (12 days starvation and 1, 2 and 3 days refeeding, respectively) on egg laying and albumen gland activity in the freshwater snail, Bulinus truncatus were studied. 2. The egg laying of starving snails rapidly decreased and ceased by day 6 of starvation. Egg laying was restored 24 hr after refeeding. The recorded decrease in albumen gland wet weight was proportional to the starvation periods. The DNA contents of the glands of the different experimental groups was not statistically different from the controls. 3. Albumen gland synthetic activity expressed as 14C-glucose incorporation into galactogen/microgram DNA and 3H-amino acids into total protein was determined. The glands showed an abrupt decrease in synthetic activity after 1 day of starvation and gradually decreased further until days 9-12. The decrease in activity of the glands was more rapid than that of egg laying. Upon refeeding, the activity of the glands recovered rapidly, simultaneous with the increase in wet weight and egg laying. 4. In conclusion, there is a correlation between egg laying and the in vitro activity of albumen glands. The results show a short-term effect of starvation on the fecundity of the snails. Such studies could be useful in field studies as well as snail control by applying molluscicides under optimal conditions.     

Effect of alternating the magnetic field on phosphate metabolism in the nervous system of Helix pomatia

The effect of extremely low frequency magnetic fields (50 Hz, 0.5 mT) - ELF-MF, on phosphate metabolism has been studied in the isolated ganglions of the garden snail Helix pomatia, after 7 and 16 days of snail exposure to ELF-MF. The influence of ELF-MF on the level of phosphate compounds and intracellular pH was monitored by 31P NMR spectroscopy. Furthermore, the activity of enzymes involved in phosphate turnover, total ATPases, Na+/K+-ATPase and acid phosphatase has been measured. The exposure of snails to the ELF-MF for the period of 7 days shifted intracellular pH toward more alkaline conditions, and increased the activity of investigated enzymes. Prolonged exposure to the ELF-MF for the period of 16 days caused a decrease of PCr and ATP levels and decreased enzyme activity, compared to the 7-day treatment group. Our results can be explained in terms of: 1. increase in phosphate turnover by exposure to the ELF-MF for the period of 7 days, and 2. adaptation of phosphate metabolism in the nervous system of snails to prolonged ELF-MF exposure.     

EFFECTS OF SHORT-TERM CULTURE ON POPULATIONS OF HEMOPOIETIC PROGENITOR CELLS FROM MOUSE MARROW

We have studied the response of progenitor cells in mouse marrow to short-term cultivation in cell culture. In the presence of a feeder layer of mouse renal tubules, the number of granulocyte progenitors able to form colonies in cell culture showed a net increase. No such increase in numbers of stem cells detected by the spleen colony assay was observed under the same conditions, although there was some stimulation of uptake of tritiated thymidine into these cells. A rapid decrease in the numbers of both types of progenitor cells occurred in the cultures in the absence of a feeder layer. However, when marrow cell populations that had been cultivated for 2 days in the absence of a feeder layer were transplanted into irradiated mice, the surviving stem cells detected by the in vivo assay showed a prolonged phase of rapid growth, resulting in a more pronounced 'overshoot' in the growth curve.     

The role of spotted green pufferfish Tetraodon nigroviridis in controlling golden apple snail Pomacea canaliculata: an effective biological control approach involving a new agent

The golden apple snail Pomacea canaliculata is invasive in South China and poses serious harm to agricultural production and aquatic ecosystems. In the present study, we investigated the predatory potential of the spotted green pufferfish Tetraodon nigroviridis (50?mm in body length) on snails of various sizes in fresh and brackish water (4.5 ppt salinity). The survival and damage rates of 50 snails were estimated at 1, 3, 5 and 7 days. The survival rate of snails, including 10 adult snails (20–35?mm shell height), decreased less than 25% in the presence of pufferfish, and this decrease was more profound in brackish than in fresh water. Approximately 98% of the snails died in brackish water in the presence of only four pufferfish. The pufferfish also inflicted a high rate of snail injury resulting from attacks involving bites. In addition, the pufferfish affected the behaviour of the snails, with more than 95% of snails exhibiting tightly closed opercula. Thus, the results of this study suggest that pufferfish are effective for the biological control of golden apple snails.     

Preservation of gastrointestinal bacteria and their microenvironmental associations in rats by freezing.

The use of frozen rat gastrointestinal tissue samples for both the recovery of viable bacteria and for observation of microbial communities associated with the tissue was investigated. A decrease of 1 log in lactobacilli, bifidobacteria, and anaerobes was observed when the numbers of bacteria recoverable from frozen tissue (stored 7 to 9 days) were compared to those recoverable from fresh nonfrozen tissue (zero time control). However, freezing did not appear to decrease the numbers of recoverable coliforms. Tissues, cleaved with razor blades after being frozen and stored for 7 to 9 days, showed bacterial communities situated on the mucosa and in the lumen of gastrointestinal specimens. This freezing technique preserved structures not previously observed in the gastrointestinal tract. This indicates that freezing is a good method to use to study such fragile microenvironments.     

The effect of size of M line Biomphalaria glabrata on the course of development of Echinostoma paraensei

M line Biomphalaria glabrata snails of 4-, 6-, 8-, 10-, 12-, or 20-mm shell diameter were individually exposed to 10 miracidia each of Echinostoma paraensei. Snails 10 mm in size or larger were found to be significantly less likely to harbor intraventricular sporocysts than snails in smaller size categories. The percentage of snails with intraventricular sporocysts that also developed hemocyte encapsulation responses generally increased with snail size, whereas the number of snails that ultimately became heavily parasitized with large numbers of daughter rediae decreased significantly with snail size. However, at least some snails in each size category developed such disseminated infections. Comparative histological study of 6- and 12-mm snails revealed that parasites readily penetrated both groups of snails, but were more likely to be encapsulated and destroyed in larger snails. Encapsulation reactions were noted from 1 to 15 days postexposure (dpe) in 12-mm snails, indicating that unlike other commonly studied models of trematode-gastropod interactions, snail resistance is not always manifested during the first few days following exposure. Upon infection with E. paraensei, both 6- and 12-mm snails showed significant increases in the number of circulating hemocytes/mm3 of hemolymph. In 6-mm snails, such increases occurred concurrently with successful parasite development. Hemocyte counts in 6-mm snails were significantly elevated from 4 to 15 dpe whereas in 12-mm snails they were significantly elevated from 2 to 30 dpe. A significant degree of resistance to E. paraensei develops as B. glabrata grows and attains sexual maturity. A mechanistic understanding of this phenomenon awaits further investigation.     

Effects of aestivation and starvation on the neutral lipid and phospholipid content of Biomphalaria glabrata infected with Schistosoma mansoni

The effects of aestivation or starvation on the neutral lipid and phospholipid content of Biomphalaria glabrata patently infected with Schistosoma mansoni were determined by high-performance thin-layer chromatography-densitometry. Infected-aestivated snails were maintained in a moist chamber at 24 +/- 1 C and a relative humidity of 98 +/- 1%. Infected-starved snails were maintained in artificial spring water (ASW) at 23 +/- 1 C without exogenous food. Infected snails (the controls) were maintained in ASW at 23 +/- 1 C and fed lettuce ad libitum. The 3 groups were maintained in the laboratory for 7 days, and then the lipids from the digestive gland-gonad complex (DGG) were extracted and analyzed by class. Infected-aestivated snails exhibited greater mortality rate and weight loss after 7 days than did the infected-starved snails. The steryl ester concentration in the infected-starved snails was significantly increased (P = 0.010) compared with the controls but not compared with infected-aestivated snails; the concentration of phosphatidylcholine in infected-aestivated snails was significantly decreased (P = 0.007) compared with the controls but not when compared with the infected-starved snails. Aestivation or starvation had a significant effect on the concentration of certain lipid classes in the DGG of B. glabrata infected with S. mansoni.     

Protein phosphorylation patterns during aestivation in the land snailOtala lactea

Protein phosphorylation patterns were investigated in whole tissues and subcellular fractions of active and aestivatingOtala lactea (Müller) (Pulmonata, Helicidae). Measurement of overall protein phosphorylation showed that incorporation of³²P increased until the second day after injection and remained constant for the remaining 4 days of the time course. Comparison of tissues from aestivating and active snails on day 3 showed a decreased protein phosphorylation in aestivating snails (44% of active). No differences in total and protein-associated radioactivity for foot, mantle or haemolymph were observed. Subcellular fractionation of the hepatopancreas localized the changes to plasma membrane, microsomal, and cytosolic fractions: values for aestivating animals were reduced to 71, 37 and 58% of the corresponding active values. Separation of the individual subcellular fractions on isoelectric focusing columns revealed differences in the phosphate incorporation patterns. Plasma membrane from aestivating animal hepatopancreas had a lower overall level of incorporation and fewer radioactive peaks in the pH 7–10 region than did the plasma membrane fraction from active animals. SDS-PAGE analysis of plasma membrane fractions from active and aestivating snails showed a relative decrease in phosphorylation between 60–80 kDa and 30–40 kDa. IEF analysis of cytosolic proteins from aestivating snail hepatopancreas also showed peaks of radioactivity that were apparently shifted by 0.3 pH units toward higher pI values. Increased phosphate incorporation was observed at a peak that corresponded to the pI value for pyruvate kinase in aestivating snails but definite assignment of peaks was not possible. SDS-PAGE analysis of cytosolic proteins showed an aestivation-related decrease in relative protein phosphorylation between 30–35 kDa and 40–45 kDa. A relative increase in phosphorylation during aestivation was observed for proteins between 16–22 kDa. Overall, the data indicate that snails dramatically alter their protein phosphorylation pattern in hepatopancreas during aestivation. (Mol Cell Biochem143: 7–13, 1995)Abbreviations CY cytosol - dpm radioactive disintegrations per minute - IEF isoelectrofocusing - GP glycogen phosphorylase - MC microsomes - MT mitochondria - PAGE polyacrylamide gel electrophoresis - PKF phosphofructokinase - PK pyruvate kinase - PM plasma membrane - SDS sodium dodecyl sulphate     

Cellular changes in bone marrow of malaria-infected mice. III. Chemotaxis of granulocytes

The number of bone marrow cells and their chemotactic activity was studied during malaria infection. Two days after infection of Balb/c mice with Plasmodium berghei, an increase in granulocyte number was observed in the blood. A modified Boyden chamber chemotaxis assay was employed to investigate the mechanism of granulocyte accumulation in the blood. Bone marrow cells from normal mice, from mice during a primary lethal infection and from immune mice after challenge were compared. The complement factor C5a showed chemotactic activity for bone marrow cells; a significant decrease of chemotaxis was only observed after 6 days of primary infection. Extracts of spleen, liver and infected erythrocytes lacked chemotactic activity, or caused inhibition of cell migration. Serum from mice with a 2-day primary infection contained chemotactic activity. The active component was heat labile, protease sensitive and had an estimated molecular weight of 250,000.     

Effects of chronic exposures of selected heavy metals on the glutathione S-transferase activity of freshwater snails Lymnaea natalensis in Zimbabwe

The effect of the heavy metals (cadmium, copper, mercury and lead) on snail glutathione S-transferase (GST) was investigated in 2015. Groups of Lymnaea natalensis snails were exposed to heavy metals for 28 days at concentrations reportedly found in the Mguza Dam. Water and food were changed daily. Samples were collected at days 1, 7, 14, 21 and 28 post exposure. Inhibition of GST activity, following cadmium exposures, ranged between 58 and 60%, with a decrease of 30% on day 28. When snails were exposed to copper, inhibition significantly decreased by 16%, 29%, 49% and 72% inhibition when tested on days 1, 7, 14 and 21, respectively. Inhibition on day 28 was 44%. Mercury exposures resulted in significant increases in GST inhibition, namely, 47%, 62% and 79% inhibition on days 1, 7 and 14, respectively. Inhibition on day 21 was 82%, whereas on day 28 it was significantly lower, at 29%. Concerning lead exposures, inhibition levels on day 1, 7 and 21 had mean inhibition of 60%. Inhibition on days 14 and 28 was significantly lower, with a mean inhibition of 30%. These results suggest that chronic exposures could inhibit GST activity for a certain period, after which inhibition is reduced, possibly as a result of adaptation.     

雌雄福寿螺耐寒能力的差异

为了解福寿螺耐寒性是否存在性别差异,对华南地区的雌雄福寿螺进行了过冷却研究及低温胁迫下存活率调查,并对入冬前后其体内耐寒性生理生化物质进行测定.结果表明: 雌雄螺的过冷却点均值分别为-6.83 ℃和-6.26 ℃,雌螺过冷却点显著低于雄螺;进入冬季后,福寿螺自由水含量明显下降,结合水、甘油、脂肪、糖原含量均出现明显上升,除甘油外,其余各耐寒性生理指标均存在极显著的性别差异;未经过冷驯化的雌雄福寿螺经过10 ℃处理7 d后存活率均在90%以上,继续在5 ℃下培养7 d后存活率出现明显的性别差异和壳高差异.野外调查发现在福寿螺自然种群中雌螺多于雄螺.表明福寿螺雌螺的耐寒能力强于雄螺.这对进一步探索福寿螺的生态适应性、自然性比及其耐寒性机制有一定的参考价值.