Snails Feeding Research Articles

Inertial effects on free surface pumping with an undulating surface

Free surface flows driven by boundary undulations are observed in many biological phenomena, including the feeding and locomotion of water snails. To simulate the feeding strategy of apple snails, we develop a centimetric robotic undulator that drives a thin viscous film of liquid with the wave speed $V_w$ . Our experimental results demonstrate that the behaviour of the net fluid flux $Q$ strongly depends on the Reynolds number $Re$ . Specifically, in the limit of vanishing $Re$ , we observe that $Q$ varies non-monotonically with $V_w$ , which has been successfully rationalised by Pandey et al. (Nat. Commun., vol. 14, no. 1, 2023, p. 7735) with the lubrication model. By contrast, in the regime of finite inertia ( ${Re} \sim O(1)$ ), the fluid flux continues to increase with $V_w$ and completely deviates from the prediction of lubrication theory. To explain the inertia-enhanced pumping rate, we build a thin-film, two-dimensional model via the asymptotic expansion in which we linearise the effects of inertia. Our model results match the experimental data with no fitting parameters and also show the connection to the corresponding free surface shapes $h_2$ . Going beyond the experimental data, we derive analytical expressions of $Q$ and $h_2$ , which allow us to decouple the effects of inertia, gravity, viscosity and surface tension on free surface pumping over a wide range of parameter space.

Feeding snails (Archachatina marginata) with leaves: growth performance, carcass characteristics, nutrient digestibility, proximate composition and minerals contents of snail meat

Feeding snails (Archachatina marginata) with leaves: growth performance, carcass characteristics, nutrient digestibility, proximate composition and minerals contents of snail meat

Trophic Transfer and Toxic Potency of Rare Earth Elements along a Terrestrial Plant-Herbivore Food Chain.

Extensive rare earth element (REE) mining activities have caused REE contamination of ambient agricultural soils, posing threats to associated food webs. Here, a simulated lettuce-snail food chain was conducted to evaluate the trophic transfer characteristics and the consequent effects of REEs on consumers. After 50-day exposure to soil, lettuce roots dose-dependently accumulated 9.4-76 mg kg-1 REEs and translocated 3.7-20 mg kg-1 REEs to shoots. Snails feeding on REE-contaminated shoots accumulated 3.0-6.7 mg kg-1 REEs with trophic transfer factors of 0.20-0.98, indicating trophic dilution in the lettuce-snail system. REE profiles in lettuce and snails indicated light REE (LREE) enrichment only in snails and the varied REE profiles along the food chain. This was corroborated by toxicokinetics. Estimated uptake (Ku) and elimination (Ke) parameters were 0.010-2.9 kgshoot kgsnail-1 day-1 and 0.010-1.8 day-1, respectively, with higher Ku values for LREE and HREE. The relatively high Ke, compared to Ku, indicating a fast REE elimination, supports the trophic dilution. Dietary exposure to REEs dose-dependently affected gut microbiota and metabolites in snails. These effects are mainly related to oxidative damage and energy expenditure, which are further substantiated by targeted analysis. Our study provides essential information about REE bioaccumulation characteristics and its associated risks to terrestrial food chains near REE mining areas.

Evaluation of protein sources in snail (Helix aspersa Múller) diets on the antioxidant bioactivity of peptides in meat and slime

Objective: This work evaluates the effect of a dietary supply of amaranth, oats and lentils as a protein source on anthropometric measurements, the chemical composition in meat, as well as antioxidant activity in meat peptides and secretion of the snail (Helix aspersa Múller).
 Design/methodology/approach: We worked with three groups of snails of 36 individuals and a control group fed with the same diet varying the protein source: amaranth, oats and lentils. A sample was taken every seven days and the shell's weight, width and length were measured. Five individuals from each group were sacrificed and the meat from which they were sacrificed was extracted: weight, moisture and protein. The hydrolysis soluble proteins in meat and slime were obtained and the antioxidant activity was measured using the reducing radicals DPPH• and ABTS•.
 Results: Snail meat was obtained with an increase of more than double in weight when 10% of Am was supplied as a protein source.
 Likewise, the dimensions of the shell will increase by 5%-11%. In FSM, it was obtained up to 79.8% moisture, 11.2% protein, 1.2% fat and 2.5% collagen. When obtaining snail meat flour, it was reduced to 12±1.9% humidity with up to 24.53 g/g of soluble protein. When hydrolyzing the proteins, it was observed that the peptides obtained presented the IC50 of DPPH scavenging activity of 21.58±2.7, 5.45± 1.8, 12.69±1.7 and IC50 of ABTS removal activity 8.86±0.9, 1.62±0.04, 10.84±1.0, for HFSM, HSMF and SS samples, respectively.
 Limitations on study/implications: It is necessary to carry out other studies on the functionality of snail meat proteins and thus propose their implementation in food formulations to maximize their commercialization.
 Findings/conclusions: Feeding snails with amaranth helps to increase the quality of protein in fresh meat and flour. Likewise, requests for soluble proteins from beef, flour and secretion are alternatives for preparing functional foods.

Land snails feeding on dead frogs

Land snails feeding on dead frogs

Morphological Characteristics and Chemical Composition of Flesh and Haemolymph of Snails Fed Compounded Diet using Quail Droppings Meal as Protein Source

This study investigated the morphological characteristics, and chemical composition of Archachatina marginata (African Giant Land Snail) reared on Quail droppings meal (QDM.) substituted for protein sources in snail feed. Five trial snail feeds (Diet I-V) were fed to fifty snails (average weight 157.3 g) for 12 weeks. The morphological characteristics of the snail and its flesh and haemolymph chemical composition were determined using standard methods. There was an appreciable increase in the growth parameters (weight, shell width and shell length) across the treatment groups. The feed conversion ratio (FCR) ranges from 2.74 to 3.75, and snails served Diet I gave the highest FCR. The result of the proximate analysis revealed that snail flesh possessed a higher amount of protein, fat, ash, fibre and energy except carbohydrate than hemolymph. Increasing QDM in the diets increased the proximate contents of the snail's flesh and hemolymph, except fat and fibre. The minerals found in all the treatments are not toxic, and snails fed diet V possessed the highest mineral contents (sodium, potassium, calcium, magnesium, iron and phosphorus). The result showed that diet V resulted in the best morphological parameters and feed utilisation of A. marginata snail. Substituting protein sources with QDM in snail feed improved the nutritional quality of snails, reducing the cost of the compounded ration.

Effect of common salt (NaCl) on reproductive tract dimension, haemolymph haemocyte count and biochemical parameters of Giant African Land snail (A. marginata) during dry season

A study was conducted on the effect of common salt (NaCl) on reproductive tract dimension, haemolymph haemocyte count and biochemical parameters of Giant African Land snail (GALs), Archachatina marginata during the dry season. Forty (40) snails with a weight range of 150 g–180 g were used for this study. Four (4) treatment with each consisting of ten (10) replicates were assigned as follows: T1 (Control: concentrate +0 g of salt (NaCl)), T2 (concentrate +0.05 g of salt (NaCl)), T3 (concentrate+0.15 g of salt (NaCl) and T4 (concentrate + 0.25 of salt (NaCl)). The experiment lasted 13 weeks. Haemolymph was collected at the end of 13 weeks to assess haemocyte count, total protein, albumin, globulin, alanine transaminase (ALT) and aspartate transaminase (AST). The haemocyte count was determined using a Neubeur haemocytometer, while haemolymph biochemical parameters were determined using spectrophotometric methods with the appropriate kit. The snails were also dissected for complete isolation of the reproductive tract for morphometric measurements. Key organs concerned were: Ovo-testis, albumen, little hermaphrodite duct and hepatopancreas. The weight and length of each of these organs were taken together with complete tract weight. Ovo-testis from each treatment was also harvested for histology. A mortality record was taken as the experiment progresses. The result showed that serum biochemical parameters were not significantly (P > 0.05) affected by a various inclusion level of salt used. But it had a significant effect on ovotesis length, albumen weight, little hermaphrodite weight and reproductive tract weight. However, no significant effect was seen in ovotestis weight, albumen length, little hermaphrodite length and hepatopancreas weight and length. It was also discovered that common salt (NaCl) significantly affected (P < 0.01) haemocyte count and mortality record of GALS. Snails fed 0.25 g NaCl had the highest haemocyte count, followed by those fed 0.15 g, while snails fed 0 g and 0.05 g recorded the least value. It was also discovered that 0 g NaCl inclusion into the diet of snail (A. marginata) recorded the highest mortality (60 %) followed by 0.05 g NaCl inclusion level which gave 30 % mortality. However, the inclusion level of 0.15 g and 0.25 g NaCl into snail feed recorded no mortality. Histological evaluation of the ovotestis revealed that snail given 0.25 g inclusion into the concentrate diet had active acini with spermatogonium and well-formed oocyte, followed by those group with 0.15 g with active acini with several ova. It is obvious from this study that NaCl had an immune-modulatory influence on GAS during the dry season via mitigation of mortality without negatively affecting the haemolymph biochemical parameter. Inclusion used in this study also boost reproductive apparatus functions which are usually not active during this period. It is therefore recommended that both 0.15 g and 0.25 g/kg be included into the diet of A. marginata during the dry season to mitigate challenges that confront snail farming during the period to boost production and reduce economic losses due to mortality during this season.

Utilisation Gold Snail Flour Fermented Papain Enzyme in Feed as Biofermentor to Increase Growth of Channa Striata

This study aimed to measure the optimal concentration of the enzyme papain that can be used in the snail goldfish fermentation to improve the performance of Channa Striata. This research conducted in May to September 2019 In Freshwater Fish Seed Center (BBI) Limbung, Gowa Regency. The feed used is pellet feed made from the gold snail, which segmented with the papain enzyme papaya. This study uses a Completely Randomized Design (CRD) consisting of four treatments and three replications, namely: A 1.5%, B 2.25%, C.3% and D. Control (0%). The data obtained were processed using Analysis of Variance (ANOVA) Duncan. The results showed the feeding of golden snails fermented by the enzyme papain with different concentrations provided (P &lt;0.05) the level of protein digestibility, fiber digestibility, protein retention, feed efficiency, albumin reserves, and calcium growth. However, no significant effect (P&gt; 0.05) on fat retention and Channa Striata fish seed survival. Protein digestibility, fiber digestibility, protein retention, feed use efficiency, albumin content, and balance growth. The highest value at the time of preparation B (2.25%) with the respective values (87.66%), (91.24%), (58.07%) (79.05%), (9.77%), (94gr) while the level of protein digestibility, fiber digestibility, protein retention, feed efficiency, albumin content, and concentration growth. The lowest obtained in treatment D (0%), were (60.09%), (81.72%), (32.56%), (54%), (7.88%) and (89.11gr). Water quality in the maintenance media during the study was 26-290C, pH 7-8, Oxygen 4-6mg / l and ammonia 0.013-0.11 mg / l.

Evaluation of molluscicidal activity of three mangrove species (Avicennia schaueriana, Laguncularia racemosa and Rhizophora mangle) and their effects on the bioactivity of Biomphalaria glabrata Say, 1818.

ABSTRACTSchistosomiasis is a disease of global extent reaching populations in social vulnerability. One of the control measures of this parasitosis is the use of molluscicidal substances that can fight snails of the genus Biomphalaria, intermediate hosts of Schistosoma mansoni. The aim of this work was to study the toxic activity of three mangrove species (Avicennia schaueriana Stapf. & Leech, ex Moldenke, 1939, Laguncularia racemosa (L.) CF Gaertn, 1807 and Rhizophora mangle L. 1753) on the biological activities of snails Biomphalaria glabrata. Hydroalcoholic extracts were prepared from the stem and leaves of each of the three plant species to which mollusks were exposed. The phytochemical analysis of plants showed the presence of important metabolites in the leaves and stems of L. racemosa and R. mangle, such as tannins and saponins, but the absence of these metabolites in A. schaueriana. Leaf and stem extracts of the three plant species showed low molluscicidal activity, not reaching the standards determined by the World Health Organization (WHO, 1983). L. racemosa and R. mangle has interfered with motility, feeding and oviposition of snails, unlike the extracts of A. schaueriana, which had no effect on these activities.

BŪSIMŲ PRADINIŲ KLASIŲ MOKYTOJŲ MOKSLINIO POŽIŪRIO Į GYVUS OBJEKTUS UGDYMAS: VYNUOGINĖS SRAIGĖS STEBĖJIMO ATVEJIS

The study programme of Primary Education includes Didactics of Natural Science Education (10 ECTS) and Culture and Technologies of Regional Studies (summer practicum) (5 ECTS). The latter study subject aims at educational learning of regional culture, animate and inanimate nature. In natural science education it is particularly important to ensure that curriculum is implemented through active engagement of learners: exploring, experimenting, exchanging experience and discovering. It is important to ensure that learning is conducted employing natural means and school learners are familiarised with real natural objects and phenomena. Therefore, the summer practicum for future primary teachers is organised in green learning environments through exploration and active involvement. During the summer practicum, which lasts two weeks, students take part in field or hiking trips, complete a big variety of assignments. One of them is familiarisation with the Burgundy snail: its observation and related research assignments. The snail is an appropriate object to learn animate nature as early as pre-school age. Since natural science education is based on the scientific approach, all the research assignments carried out at school contain the structure of a scientific method (observation, hypothesis, experiment, interpretation, conclusions). Growing snails in the classroom, learners are able to get acquainted with the features characteristic of organisms, parts of their bodies; a close access to snails allows for school learners‘ understanding of differences between animate and inanimate objects; a longer care of snails enables school students to observe the process of their reproduction: laying of eggs and development; while feeding snails it is possible to identify what they eat and what food they dislike; observing snails it is not difficult to notice their reactions to the environment and what organs help them to orient in the surrounding environment, etc. Keeping a living creature in the classroom, school children learn to follow hygiene regulations and to responsibly behave with animals. Possessing experience in raising animals, children are able to apply their knowledge and abilities in new contexts, i.e. speaking about feeding, keeping and living conditions of other animals, etc. Following the principle that “personal experience is much more important than the read truth”, school students received a task to keep and observe a Burgundy snail for a week. The students recorded experiments with the snails and reflected their activities in their observation diaries. The article presents the results received after the analysis of observation diaries of 19 students containing information collected while observing the Burgundy snail. The pedagogical influence of such activities on development of students’ scientific approach is also evaluated in the article. Keywords: development of scientific attitude, future primary teachers, observation of snails, research works.

Carrion consumption and its importance in a freshwater trophic generalist: the invasive apple snail Pomacea canaliculata

Trophic flexibility is a relevant trait in the potential for organisms to establish widely, maintain high abundances and spread after invasion. Pomacea canaliculata is an apple snail that feeds primarily on aquatic macrophytes, although it also consumes other trophic resources that likely play an important role in its persistence and contribute to its effects in invaded wetlands. In the present study we determined the ingestion rates in P. canaliculata for carrion and subsequent effects on growth, and performed field and laboratory experiments to investigate the mechanism of carrion detection. We observed P. canaliculata snails of all sizes feeding on carrion. The specific ingestion rates of carrion decreased with snail size and were 20 times lower than when feeding on lettuce. The growth rates of snails feeding only on carrion were 15–30% higher than those of fasting snails and 30% of those snails feeding on lettuce or lettuce and carrion. We found no evidence of distant chemoreception of carrion. The importance of carrion for P. canaliculata is mostly as an alternative resource when its preferred food is absent, and not as a complementary resource that could enhance growth. Nevertheless, the ability of P. canaliculata to profit from carrion may help explain its potential to establish widely and to have effects on aquatic vegetation.

ALTERNATE FOOD-CHAIN TRANSFER OF THE TOXIN LINKED TO AVIAN VACUOLAR MYELINOPATHY AND IMPLICATIONS FOR THE ENDANGERED FLORIDA SNAIL KITE (ROSTRHAMUS SOCIABILIS).

Avian vacuolar myelinopathy (AVM) is a neurologic disease causing recurrent mortality of Bald Eagles ( Haliaeetus leucocephalus ) and American Coots ( Fulica americana ) at reservoirs and small impoundments in the southern US. Since 1994, AVM is considered the cause of death for over 170 Bald Eagles and thousands of American Coots and other species of wild birds. Previous studies link the disease to an uncharacterized toxin produced by a recently described cyanobacterium, Aetokthonos hydrillicola gen. et sp. nov. that grows epiphytically on submerged aquatic vegetation (SAV). The toxin accumulates, likely in the gastrointestinal tract of waterbirds that consume SAV, and birds of prey are exposed when feeding on the moribund waterbirds. Aetokthonos hydrillicola has been identified in all reservoirs where AVM deaths have occurred and was identified growing abundantly on an exotic SAV hydrilla ( Hydrilla verticillata ) in Lake Tohopekaliga (Toho) in central Florida. Toho supports a breeding population of a federally endangered raptor, the Florida Snail Kite ( Rostrhamus sociabilis ) and a dense infestation of an exotic herbivorous aquatic snail, the island applesnail ( Pomacea maculata ), a primary source of food for resident Snail Kites. We investigated the potential for transmission in a new food chain and, in laboratory feeding trials, confirmed that the AVM toxin was present in the hydrilla/A. hydrillicola matrix collected from Toho. Additionally, laboratory birds that were fed apple snails feeding on hydrilla/A. hydrillicola material from a confirmed AVM site displayed clinical signs (3/5), and all five developed brain lesions unique to AVM. This documentation of AVM toxin in central Florida and the demonstration of AVM toxin transfer through invertebrates indicate a significant risk to the already diminished population of endangered Snail Kites.

耳萝卜螺对菹草的牧食研究

水生态系统中存在螺–草互利现象。然而，植食性螺类与水生植物之间是否存在这种互利关系目前尚无定论。耳萝卜螺是水体中常见的淡水螺类，常常匍匐岸边或附着在水生植物茎及叶片上。菹草是水体中常见的沉水植物，常常大量繁殖引起水体富营养化。为此我在实验室可控条件下，研究了耳萝卜螺牧食对菹草生长的影响。结果表明：耳萝卜螺的牧食对菹草生长有显著影响，牧食损害使菹草的相对生长率、块茎数量及重量下降；耳萝卜螺对菹草的牧食率随耳萝卜螺规格的变化而改变，耳萝卜螺规格越小对菹草的牧食率越高。 There is a mutual beneficial phenomenon between snails and grass in the aquatic ecosystem. However, we have not reached the conclusion on the existence of mutual relationship between plant feeding snails and hydrophyte. Radix auricularia is common freshwater snails in the water, which prostrates on the shore or attaches on the aquatic plant stems and leaves. Radix auricularia, which is a common water submerged plant, blooms frequently and causes eutrophication. This is the reason why under the controlled conditions, I did the research on the Radix auricularia which has grazing effects on the growth of Potamogeton crispus. The result shows that: Radix auricularia has grazing effect on the growth of Potamogeton crispus; grazing of Radix auricularia has quite effect on the growth Potamogeton crispus; the grazing rate of Radix auricularia to Potamogeton crispus will be altered by the change of the specifications of Radix auricularia, as well as the weight of tubers. And the smaller in the specifications of Radix auricularia, the higher in the grazing rate of Potamogeton crispus.

Morphology of sensory papillae on the feeding proboscis of cone snails (Mollusca, Gastropoda)

AbstractCone snails, predatory marine gastropods, have developed a specialized prey capture method in which a long, distensible proboscis is used to identify prey and inject venom via a hydraulically propelled hollow radular tooth. Using brightfield, epifluorescence, confocal, and transmission and scanning electron microscopy, we describe the morphology of ciliated sensory structures concentrated on the tip of the proboscis. The number and morphology of these sensory papillae are linked to the type of preferred prey: cone snails feeding on worms and mollusks have short, cone or finger‐shaped papillae, whereas fish‐hunting cone snails have long tubular papillae in addition to short conical papillae. Sensory papillae are well positioned to provide information necessary to locate, identify, and dispatch prey. Proboscis tips and their sensory papillae regenerated within 10 d following experimental ablation, and snails with regenerated proboscis tips were able to locate and envenomate prey. The remarkable intrageneric variation found in the morphology of these sensory structures is probably linked to the specialized prey that cone snail species have evolved to hunt.

Effects of feeding snails with pineapple waste on feed consumption, growth and cost benefits

The effect of inclusion of 0, 5, 10, and 15% of pineapple waste (PW) in the diet of growing snails (Archachatina marginata), on feed consumption, growth, dressing percentage and cost benefits was studied. Each treatment was replicated thrice with 7 snails per replicate in a completely randomized design. Variables studied were: feed intake, weight gain, shell length and width, feed conversion ratio and cost per weight gain. The weight gain until 10% level of inclusion compared favourably with the control diet. The feed conversion ratio was similar, respect to control, at all levels of inclusion. The feed intake reduced as the level of PW increased (p<0.05). The shell length and width were not affected by varying PW level. The dressing percent at 0, 5 and 10% levels of inclusion were not influenced by treatments. The cost/weight gain reduced as level of inclusion of PW increased in the diet. Pineapple waste could be included up to 10% in the diet of growing snails.

Induced chemical defenses in a freshwater macrophyte suppress herbivore fitness and the growth of associated microbes

The freshwater macrophyte Cabomba caroliniana induces a chemical defense when attacked by either the crayfish Procambrus clarkii or the snail Pomacea canaliculata. Induction by either consumer lowers the palatability of the plant to both consumers. When offered food ad libitum, snails feeding on non-induced C. caroliniana grew 2.6-2.7 times more than those feeding on induced C. caroliniana. Because snails fed less on induced plants, this could be a behavioral effect (reduced feeding), a physiological effect of the induced metabolites on the consumer, or both. To assess these possibilities, we made artificial diets with lipid extracts of induced versus non-induced C. caroliniana and restricted control snails to consuming only as much as treatment snails consumed. Growth measured as shell diameter was significantly lower on the diet containing extract from induced, as opposed to non-induced, plants; change in snail mass was more variable and showed a similar, but non-significant, trend. Thus, snails may reduce feeding on induced plants to avoid suppression of fitness. The induced defenses also suppressed growth of co-occurring microbes that might attack the plant through herbivore-generated feeding scars. When two bacteria and three fungi isolated from C. caroliniana surfaces were cultured with the lipid extract from induced and non-induced C. caroliniana, both extracts inhibited the microbes, but the induced extract was more potent against three of the five potential pathogens. Thus, induced plant defenses can act against both direct consumers and microbes that might invade the plant indirectly through herbivore-generated wounds.

Feeding and growth of native, invasive and non-invasive alien apple snails (Ampullariidae) in the United States: Invasives eat more and grow more

The United States hosts one native and five non-native species of aquatic apple snails (Ampullariidae). All are currently found in or around the Everglades in Florida. Two of these introduced species have devastated wetlands in Southeast Asia, but little is known about how they may impact the Everglades. To evaluate potential impacts of introduced apple snails relative to the native species, we investigated plant species preference, consumption rates, growth rates, and growth efficiencies in five introduced and the single native species across eight native macrophytes common in the Everglades. Three of the non-native snails are invasive, one has shown no tendency to expand, and one appears to have minimal direct impact on macrophytes due to its diet. All snails exhibited similar feeding preferences, with Utricularia sp. being the most preferred, Bacopa caroliniana, Sagittaria latifolia, and Nymphaea odorata being of intermediate preference, and Eleocharis cellulosa, Pontederia cordata, Panicum hemitomon and Typha sp. being least preferred (avoided as foods). Consumption and growth was minimal for P. diffusa on all macrophytes. On Utricularia sp. and Bacopa caroliniana, the invasive species Pomacea insularum and P. canaliculata tended to eat more, grow more, and have higher conversion efficiencies than the native P. paludosa or the non-invasive P. haustrum. These contrasts were more often significant for P. insularum than for P. canaliculata. The greater rates of expansion by the invasive species may derive from their enhanced feeding and growth rates.

Poultry as reservoir hosts for fishborne zoonotic trematodes in Vietnamese fish farms

Fishborne zoonotic trematodes (FZT) are widespread in Vietnam and Southeast Asia. It is now recognized that the risk of being infected from eating raw fish dishes applies not only to humans, but also to domestic animals (e.g., cats, dogs, and pigs) and fish-eating birds. The role of ducks and chicken, commonly raised on fish farms, as reservoir hosts, however, has not been adequately investigated. To study this question, chickens and ducks from integrated poultry-fish farms in Nghia Lac and Nghia Phu communes, Nam Dinh province, Vietnam were surveyed for FZT infections. A total of 50 ducks and 50 chickens from each commune were examined. Results revealed that 12% of chickens and 30% of ducks were infected with various species of trematodes, including two zoonotic species, Centrocestus formosanus and Echinostoma cinetorchis. Both occurred in chickens whereas only E. cinetorchis was found in ducks. Prevalence of these zoonotic species was 12% and 7% in ducks and chickens, respectively. Among other trematodes, Hypoderaeum conoideum, also a zoonotic fluke, was the most prevalent (20–30%). The feeding of snails and fish remains to poultry, either intentionally or by discharge of waste from the slaughter of ducks and chickens into the ponds, was identified as risk factors for trematode infection. The FZT species and low prevalence found in poultry in these communes indicate their role as reservoir hosts is minor.

Effects of macrophytes on feeding and life‐history traits of the invasive apple snail Pomacea canaliculata

Summary1. Biological invasions have become a serious threat to ecosystems worldwide. Various factors can contribute to the success of biological invasion. We examined how different macrophyte food affected feeding and life‐history traits of the invasive herbivorous snail Pomacea canaliculata, and whether differences in snail life‐history traits could explain its successful infestation of agricultural and non‐agricultural wetlands in Asia.2. We tested five cultivated and five wild semi‐aquatic macrophytes. Snail daily feeding rate varied substantially with plant species, ranging from 1.3% to 22% of its body mass. Snails fed with four (Amaranthus gangeticus, Apium graveolens dulce, Ipomoea aquatica and Nasturtium officinale) of the five cultivated macrophyte species exhibited high survivorship, fast growth and high fecundity. Snails fed with Colocasia esculenta, however, grew poorly, did not reproduce and eventually died.3. Of the five wild species (Eichhornia crassipes, Ludwigia adscendens, Murdannia nudiflora, Myriophyllum aquaticum and Polygonum hydropiper), M. nudiflora supported a high snail survival, but snails had slower growth and lower fecundity than those reared on the four palatable cultivated species. Snails fed with L. adscendens grew substantially slower than those fed with M. nudiflora, and produced only a small clutch of eggs. Snails fed with E. crassipes, M. aquaticum and P. hydropiper had very low survivorship, grew very little and did not reproduce.4. We determined six plant properties and their correlation with the feeding, growth and reproduction of the apple snails. Cultivated macrophytes in general had a higher nutritional value and lower physical and chemical defences. Phenolic content was negatively correlated with snail feeding rate, while plant nitrogen and phosphorus contents were positively correlated with snail egg production and growth, respectively.5. These results indicate that, due to their higher nutritional value and lower chemical and physical defences, cultivated macrophytes are in general desirable for the apple snail which may partly explain its successful invasion into wet agricultural areas in Asia. This snail may also selectively graze poorly defended wild macrophytes in non‐agricultural wetlands, leading to changes in floral diversity and wetland functioning. Management of this and other apple snails with similar life‐history traits should thus focus on the prevention of their further spread.

Wetland Restoration and Invasive Species: Apple snail (Pomacea insularum) Feeding on Native and Invasive Aquatic Plants

Abstract The apple snail Pomacea insularum is an aquatic invasive gastropod native to South America that has the potential to cause harm to aquatic ecosystems, wetland restoration, and agriculture. To predict the potential impact of this snail on aquatic ecosystems, we tested the feeding rate of P. insularum, under laboratory nonchoice experiments, for 3 species of invasive macrophytes and 13 species of native aquatic plants that are important for wetland restoration and health. High levels of consumption were recorded for four native species (Ceratophyllum demersum, Hymenocallis liriosme, Ruppia maritima, and Sagittaria lancifolia) and three invasive species (Colocasia esculenta, Alternanthera philoxeroides, and Eichhornia crassipes). In contrast, less than 10% of the biomass of Spartina alterniflora, Scirpus californicus, Thalia dealbata, and Typha latifolia was consumed by P. insularum over the test period. The palatability of macrophytes was negatively correlated with dry matter content, making our results generalizable to all regions where this invader may be present. Based on our results, wetland restoration in areas invaded by P. insularum should focus on emergent structural species with low palatability. Apple snails should not be considered as agents of biocontrol for invasive plants; although apple snails fed on invasive plants at a high rate, their consumption of many native species was even greater.