The distribution of apple snail Pomacea canaliculata is islandwide but Pomacea scalaris is only found in southern Taiwan. In order to gain more information on the not well-known invasive species of P. scalaris, the growth and feeding of P. canaliculata and P. scalaris were studied. The hatching period of P. canaliculata (10.4¡Ó1.3 days) was shorter than that of P. scalaris (12.2¡Ó2.3 days). And, the hatching size of P. canaliculata was also smaller. Two weeks after hatching, a significant higher growth rate in P. canaliculata had been found. The 75-day growth equations for P. canaliculata and P. scalaris were y = 0.29x + 1.09 (p < 0.001) and y = 0.16x + 1.68 (p < 0.001), respectively. Feeding structures of mandible, radulae, central tooth and stomach in P. canaliculata were larger than that of P. scalaris. But, there was no significant difference in the length of gut between the two species. Food passing time in P. canaliculata (1.4¡Ó0.7 days) was less than that of P. scalaris (2.9¡Ó0.7 days). And, the approximate digestibility per day of P. canaliculata (44.41¡Ó24.02%) was higher than that of P. scalaris. Through the analyses of £_13C, £_15N, stomach content and feces, it is known that they have the same trophic level with similar food sources. Additionally, the values of £_13C and £_15N were significantly different between sites of JiouRu and Wugou-shui, Pingtung. In other words, the feeding environments were different between the two sites. Based on the results, it is concluded that the superiority of growth and feeding performance in P. canaliculata is important in shaping its wide distribution in Taiwan.

The apple snail, Pomacea canaliculata has made a tremendous threat to agricultural crops as well as environmental ecology in Taiwan. Although various control methods are available, there are certain limitations in each of the applications. The present study was conducted to evaluate the application potential of food preference in attractant usage to apple snails. It has been found that apple snails actively searched animal materials. Fish blood and egg glair were as attractive as banana (Musa sp.). With equal weight, blood clots from cobia (Rachycentron canadum) and pig (Sus sp.) were more attractive than banana, and cooked pig blood was as attractive as banana. The response of snails to concentrated extracts from fish blood (with molecular weight > 5000) was stronger than banana. There were no significant differences in snails¡¦ responses to blood from pig, cobia, freshwater and seawater milk fish (Chanos chanos). Furthermore, protein was probably the attractive source to apple snails and frozen-treated blood increased attractive response. As expected, blood clots from cobia and pig were more attractive than banana in the field. In summary, the results show that animal protein is potentially applicable as attractive components for apple snails.

The apple snail, Pomacea canaliculata has made a tremendous threat to aquatic agricultural crops for many years. But safe and effective methods to eliminate them are still not available. Traditionally, pesticides are the most common way to kill apple snails. However, the occurrence of drug resistance and drug residual causes even more serious problems. The present study was conducted to evaluate the effectiveness of attractants to apple snails in the fields. The experiments included the effectiveness of different attractants and trap designs under different environmental conditions. It was found that attractants of banana pulp, chicken blood and condensed fish soluble were effective with at least 12-hour trapping time. The sizes of attracted snails were similar to the ambient snails. Snails (Pomacea scalaris, Sinotaia quadrata, Planorbioidae spp.), insects (Sphaerodema rustica, water scorpion),tadpole and fishes (Poecilia reticulate, Trichogaster trichopterus) were also found in the traps. Besides, two-opening traps with funnel entrance were more effective than the traps without funnel entrance. In general, in still water with ambient density of apple snails range from 6.2¡Ó 6.1 to 50.3¡Ó14.2 individual/m2,the relationship between attracted snails and ambient snail density was negative in chicken blood group (p < 0.001), positive in condensed fish soluble (p < 0.05) and no trend in banana group (p > 0.05). The results support the hypothesis that areas with abundant food usually have high snails density and those snails are less attracted by potential food items.

No description available.

Pomacea canaliculata es un gasterópodo dulceacuícola perteneciente a la familia Ampullariidae, cuyo rango natural de distribución se extiende desde el sur de Brasil hasta el sur bonaerense. Esta especie ha sido introducida accidental o intencionalmente en numerosos países, y es considerada uno de los 100 peores invasores a nivel mundial. El objetivo de esta tesis fue analizar los determinantes de la distribución espacial de P. canaliculata a distintas escalas espaciales. Específicamente se estudió el grado de dependencia de la respiración aérea, la velocidad de desprendimiento, el efecto de la corriente sobre la dispersión y el efecto de la temperatu-ra y el tiempo de exposición sobre la actividad. También se caracterizó cuantitativamente su microhábitat y se exploraron la distribución entre y dentro de los arroyos de la cuenca de las Lagunas Encadenadas del Oeste y sus patrones tempora-les de actividad. Los resultados obtenidos aquí mostraron que la restricción en la respiración aérea afecta negativamente la actividad y la supervivencia y que sus efectos empeoran con la temperatura y la polución del agua. La actividad se incre-menta con temperaturas entre 10 y 30C pero el tiempo de exposición carece de importancia, salvo a temperaturas superiores a 30C y en aguas polutas. La velocidad de desprendimiento fluctuó entre 0.07 y 1.64 m.s-1, indicando que P. canaliculata puede soportar, por un período corto, velocidades que se encuentran entre las máximas registradas en los arroyos de la cuenca de las Encadenadas del Oeste. Velocidades de la corriente menores a 0.3 m.s-1 no influyen sobre la tasa y dirección de dispersión por reptación. No hay una respuesta reotáctica positiva que compense los eventos de deriva aguas abajo, probablemente dificultando la coloniza-ción de tramos cercanos a las sierras. Los microhábitats más utilizados por esta especie se caracterizaron por su proximi-dad a la orilla o a sustratos emergentes aptos para ventilar el pulmón, velocidades de la corriente que no interfieren con las actividades de rutina (menores a 0.3 m.s-1) y sedimentos finos ricos en materia orgánica o abundancia de macrófitas y detritos. La efectividad de algunas medidas de control podría incrementarse reuniendo esfuerzos donde se concentran los caracoles debido a su dependencia del acceso al aire. El por-centaje de caracoles activos en la cuenca de las Encadena-das del Oeste fluctuó entre 0 y 100% durante el año. En la estación fría la mayoría de los caracoles estaban inactivos pero aparentemente no entran en un estado letárgico profundo y persistente, sino que muestran una respuesta rápida a cambios de temperatura, reactivándose tan pronto como las condiciones sean favorables. A pesar de que algunas variables ambientales influyeron sobre la distribución de P. canaliculata entre y dentro de los arroyos de la cuenca de las Encadenadas del Oeste, ninguna resultó determinante de su presencia. Todos los arroyos serían habitables para esta especie, aunque sólo en algunos las poblaciones podrían permanecer a largo plazo. Probablemente, las condiciones climáticas e hidrológicas, muy variables e impredecibles en esta región, sean determinantes de eventos de extinción-colonización y, en consecuencia, de su distribución en esta cuenca. / Pomacea canaliculata is a freshwater snail belonging to the family Ampullariidae, whose natural range of distribution extends from southern Brazil to southern Buenos Aires Province in Argentina. This species has been introduced either accidentally or intentionally to many countries and is considered to be one of the 100 worst invaders worldwide. The aim of this thesis was to analyze the determinants of the spatial distribution of P. canaliculata at different spatial scales. Specifically, the dependence on aerial respiration, the effect of water velocity on detachment and dispersal, and the effects of temperature and exposure time on activity were investigated. In addition, its microhabitat was characterized quantitatively and the distribution among and within streams in the Encadenadas del Oeste basin (Buenos Aires Province, Argentina) and the temporal patterns of activity were explored. The experimental results showed that a restriction in aerial respiration negatively affected activity and survival and that its effects worsened with increasing temperatures and water fouling. Activity increased with temperature between 10 and 30C but exposure time was irrelevant, except at temperatures above 30C and in fouled waters. The detachment velocity ranged from 0.07 to 1.64 m.s-1, indicating that P. canaliculata can resist, at least for short periods, velocities that were among the highest recorded in the streams of Encadenadas del Oeste basin. Current velocities below 0.3 m.s-1 did not influence dispersal rate and direction by crawling. A positive rheotactic response able to compensate the natural events of downstream drifting was not evident, so that the colonization of piedmont sections is unlikely. The microhabitats most frequently used by this species were characterized by their proximity to the shore or an emergent substratum suitable for lung ventilation, by water velocities not interfering with routine activities (below 0.3 m.s-1), and by fine sediments rich in organic matter or abundance of macrophytes and detritus. The effectiveness of some control measures could be increased by focusing efforts on areas where the snails are concentrated due to their dependence on access to air. The percentage of active snails in Encadenadas del Oeste basin fluctuated between 0 and 100% along the year. During the cold season most of the snails were inactive though they apparently not enter a deep and persistent lethargic state but show a rather quick response to temperature changes, being able to reactivate as soon as conditions become favorable. Despite the fact that some environmental variables influenced the distribution of P. canaliculata among and within the streams of Encadenadas del Oeste basin, none was determinant of its presence. All streams would be habitable for this species, but only in some of them populations would be able to persist long term. Probably, the climatic and hydrological conditions, which are highly variable and unpredictable in this region, are determi-nants of extinction-colonization events and, consequently, of its distribution in the streams of this basin.

Pomacea canaliculata es un gasterópodo de agua dulce perteneciente a la familia Ampullariidae (Architaenioglossa, Caenogastropoda), cuyo rango de distribución natural abarca desde el sur de Brasil hasta el sur Bonaerense. Se lo considera uno de los 100 peores invasores a escala global debido a su voracidad, altas tasas reproductivas y alta plasticidad en su ciclo vital. El objetivo principal de este trabajo de tesis fue estudiar la norma de reacción de diversas características del ciclo vital de P. canaliculata frente a la disponibilidad trófica. Específicamente se estudió cómo afectan distintos niveles de disponibilidad trófica constantes, el crecimiento, la talla y la edad a la que alcanzan la madurez, la cantidad de recursos que destinan a la reproducción y la forma de su conchilla. Finalmente, se estudió el efecto de una interrupción abrupta en la alimentación sobre la reproducción, el crecimiento y la supervivencia. Los resultados mostraron una superioridad en los parámetros específicos de ingestión y eficiencia de crecimiento de las hembras respecto de los machos y en los juveniles respecto de los adultos. P. canaliculata puede completar normalmente su ciclo vital bajo un amplio rango de disponibilidades tróficas. Frente a distintas disponibilidades tróficas la estrategia de las hembras fue madurar a distintas edades y a una talla semejante, mientras que en los machos fue madurar a edades semejantes pero a tallas muy distintas. La disponibilidad trófica no afectó el éxito reproductivo de los machos, mientras que en las hembras las restricciones en la disponibilidad trófica provocaron descensos, principalmente en el número de huevos. En caracoles en reproducción, un corte abrupto de la alimentación redujo la supervivencia más en machos que en hembras, y produjo una caída en el número de cópulas y de puestas. Un efecto maternal en el cual el vigor de la progenie de hembras que crecieron con baja disponibilidad trófica se incrementa respecto de las hembras sin restricciones alimentarias parece indicar una estrategia adaptativa transgeneracional. La forma de la conchilla parece cambiar en algún grado con la disponibilidad trófica pero sin ningún patrón claro y monótono; el dimorfismo sexual no parece verse alterado por la disponibilidad trófica. Aparecen indicios que sugieren que el contenido de nitratos del agua y la materia orgánica del sustrato en ambientes naturales tienen relación con parámetros poblacionales como la densidad de puestas y la talla máxima de P. canaliculata; por el contrario, los iones inorgánicos y los factores fisicoquímicos analizados no mostraron relación con éstos. La estrategia evolutiva de Pomacea canaliculata frente a la disponibilidad trófica parece basarse en una alta plasticidad de su ciclo vital, abarcando el crecimiento, la maduración y el esfuerzo reproductivo, así como en un alto grado de diferenciación sexual en estas características. / Pomacea canaliculata is a freshwater snail belonging to the family Ampullariidae (Architaenioglossa, Caenogastropoda) whose natural range extends from Southern Brazil to Southern Pampas in Argentina. It has been nominated as one of the 100 worst invaders at a global scale, owing to its voracious feeding habits, high reproductive rates and plastic life history traits. The main aim of this Thesis was to study the reaction norms to trophic availability of several life history traits in P. canaliculata. Specifically, the way in which growth, age and size at maturity, reproductive effort and shell shape are affected by different chronic levels of trophic availability was investigated. In addition, the effect of an abrupt shortage of food on reproduction, growth and survivorship was investigated. The results obtained showed higher values of specific parameters of ingestion and growth efficiency in females than in males and in juvenile snails relative to adults. P. canaliculata is able to complete its life cycle under a wide range of trophic availability. Confronted with different trophic availabilities, the strategy of females was to mature at different ages but always at almost the same size, whereas for males it was to mature at the same age but at very different sizes. Trophic availability did not affect the reproductive success of males while for females restricted trophic availabilities caused a drop mainly in the number of eggs laid. For snails which were already in reproductive state, an abrupt shortage of food reduced the survivorship of males in a higher degree than in females and a drop in the number of copulations and egg masses laid. A maternal effect, in which the progeny of females grown under low trophic availabilities showed a higher vigor than those from females fed ad libitum, suggests a transgeneration adaptive strategy. Shell shape seems to be affected by trophic availability though without producing a clear and monotonous pattern; sexual dimorphism seems not to be affected by trophic availability. The nitrate content of water and the organic matter of sediments seem to be related to demographic parameters of P. canaliculata, like density of egg masses and maximum sizes; on the other hand, inorganic ions and physicochemical variables did not show any relation with them. The evolutionary strategy of Pomacea canaliculata relative to trophic availability seems to be based on a high plasticity in life history, including growth, maturity and reproductive effort, and on a high degree of sexual differentiation in these traits.

The distribution of apple snail Pomacea canaliculata are island-wide but Pomacea scalaris is only found in southern Taiwan. In order to gain more information on the not well-known alien invasive species, comparative studies on the reproduction and thermal tolerance of P. canaliculata and P. scalaris were conducted. Sexual dimorphism in shell morphology has been found in both species, with wider operculum in males. Positive correlation between shell length and penis sheath length or penis length has been observed in male P. canaliculata and P. scalaris, based on the samples collected during the period of December 2004 and March 2006, The width of penis sheath in P. canaliculata was greater than in P. scalaris. Positive correlation between shell length and the height and width of vestigial penis in female P. canaliculata and P. scalaris was also found. The width of vestigial penis in P. scalaris was greater than in P. canaliculata. Gonadosomatic index (GSI) in male P. canaliculata and P. scalaris was 68 and 60% and 31 and 33% in females. Their reproductive cycle was annual without seasonal peaks. Significant difference in thermopreferrenda was found between P. canaliculata and P. scalaris. The 24, 48 and 72-h lethal thermal minima temperatures in P. canaliculata and P. scalaris were similar, i.e. 9.8¡V11.8¢J. And, the 24, 48 and 72-h lethal thermal maxima temperatures were 33.1¡V35.9¢J. Based on the results, it is known that P. canaliculata and P. scalaris reproduce year-round and temperature is not a major factor in shaping the species distribution pattern in Taiwan.

The Pomacea apple snails are amphibious operculate freshwater gastropods. They exhibit different stress tolerant abilities as some of them are invasive (e.g., Pomacea maculata and Pomacea canaliculata) and others are non-invasive species (e.g., Pomacea diffusa). By using a comparative approach, I have profiled the perivitelline fluid of P. maculata, compared the physiological and proteomic responses of P. canaliculata and P. diffusa to thermal and hypoxic stressors, and examined their sequence divergences. 74 proteins were identified from the PVF of P. maculata. Comparison of gene expression levels between albumen gland (the organ that secrets PVF) and other organs showed that 24 PVF genes were specifically expressed in albumen gland. Base substitution analysis of PVF and housekeeping orthologs between P. maculata and its congener P. canaliculata showed that these reproductive genes have higher evolutionary rate. The LT50 of P. canaliculata was significantly higher than that of P. diffusa. More than 3,350 proteins were identified from the hepatopancreas of the snails exposed to acute and chronic thermal stress using iTRAQ-coupled mass spectrometry. Chronic exposure caused differential expression of more proteins, with many of them related to restoration of damaged molecules, ubiquitinating dysfunctional molecules, and utilization of energy reserves in both species; but only in P. diffusa there was a shift from carbohydrate to lipid catabolism. Analysis of orthologous genes encoding the differentially expressed proteins revealed nine candidate genes may have undergone positive selection (Ka/Ks > 0.5). A 72 h mortality experiment showed that P. canaliculata is much more tolerant to hypoxia than P. diffusa. The two species were then exposed to four levels of dissolved oxygen (6.7, 4.1, 2.0 and 1.0 mg O2 L-1) for 8 h, and their gill proteins were analyzed using iTRAQ-coupled LC-MS/MS. Compared with P. diffusa, P. canaliculata had more up-regulated signal transduction proteins and down-regulated proteins which are involved in glycolysis and the tricarboxylic acid cycle. Evolutionary analysis indicated that selection has acted on some of the hypoxia responsive genes. The comparative method and results provide a framework for studying the genetic basis of species invasion and predicting their further expansion in a changing climate for non-model species.

The apple snail Pomacea canaliculata Lamarck is a native of South America but has invaded Hong Kong since early 1980s. Its feeding has resulted in a tremendous loss in semi-aquatic agriculture, especially rice (Oryza sativa L.) and other aquatic crops such as taro (Colocasia esculenta L.) and water spinach (Ipomoea aquatica Forssk). While spreading to freshwater wetlands, its feeding threatens macrophyte diversity. Owing to its voracious appetite, this invasive snail has also become a competitor of lowland indigenous mollusks. On ecosystem level, over-grazing by high density of apple snails could also induce excessive release of nutrients from macrophytes to water bodies, thus promoting phytoplankton growth and primary production. Measures to control invasive apple snails fall into three categories: mechanical / cultural, chemical, and biological. Among them, biological control methods are appealing because they are usually considered relatively less labor-intensive and more cost-effective. However, both the control efficacy and potential non-target effects should be carefully evaluated before adopting a species in biological control. Although various fish species have been proposed as biological control agents for apple snails, their effectiveness and non-target effects on wetland flora and fauna are largely unknown. This study investigated the feasibility of black carp (Mylopharyngodon piceus Richardson) as bio-control agent for apple snails in both laboratory and field experiments. The laboratory experiment compared the feeding of black carp, common carp (Cyprinus carpio L.) and white-spotted catfish (Clarias fuscus Lacepède) on apple snails. These three species are indigenous and widely aquacultured in southern China. The three species of fish of comparable body length were each offered apple snails of various sizes ad libitum in aquaria. Black carp (fork length: 165 mm; maximum gap width: 16 mm) was the most effective predator, with a predatory rate of 70.5 apple snails in 48 hours. Common carp and white-spotted catfish of similar fork lengths consumed only 58.6 and 15.7 apple snails on average within the same experimental period. Apple snails preyed upon by black carp and common carp were juveniles, with their respective shell length ranged from 3 - 16mm and 3 - 17mm, while that for white-spotted catfish ranged from 3 - 21mm. An 8-week mesocosm experiment was conducted in a constructed wetland during the dry season of 2011 to determine whether black carp (fork length: 170 -185 mm) is as effective as common carp (fork length: 170 - 195 mm) as a bio-control agent for apple snails, but causes less herbivory to macrophytes and predation to non-Pomacea snails. Both species of carp preyed effectively on P. canaliculata, removing almost all apple snail individuals (~ 200 per enclosure) that were small enough to fit into their mouths. The effects of the two fish species on macrophytes were different. Black carp reduced herbivory on macrophytes through reducing apple snail density. However, common carp reduced apple snail density but did not result in a lower level of herbivory because it also grazed on macrophytes. Non-target mollusk density was reduced by both fish species. A one-year whole-pond experiment was also conducted in June 2012 to June 2013 to investigate the applicability of black carp as a biological control agent of apple snails in constructed freshwater wetlands. Three separate constructed freshwater wetlands were used as replicates of the experiment. Each wetland was divided into a control side without black carp and a treatment side with black carp. Four individuals of black carp (fork length 260 - 310 mm) were released to the side of wetland assigned as treatment. Prior to starting the experiment and every three months, density of apple snails and other macro-invertebrates, apple snail egg clutch size and abundance, water quality parameters (total nitrogen, ammonia nitrogen, total phosphorus and reactive phosphorus) were recorded. Black carp was highly tolerant to the low dissolved oxygen in the shallow stagnant waters. It was an effective predator of juvenile apple snails (<5 – 25mm), but it did not result in significant reduction of adult apple snails (shell length >25mm) nor affected their reproduction. In addition, black carp preyed on non-apple snail macro-invertebrates, especially mollusks. In conclusion, our study has shown that juvenile black carp (minimum total length: 300mm) is a suitable bio-control agent of apple snails in shallow water wetlands as it is tolerant of stagnant poor water quality and is an effective predator of apple snails. A major decline of 89.2% in average overall density of apple snail has been recorded in the treatment plots of the three experimental sites after one year. Juvenile snails would be eradicated before they get to mature minimum size (male SL: 25.2 ± 3.3mm; female: 29.8 ± 3.6mm) for reproduction. Given the longevity of black carp, a low stocking density (80-89 individuals ha-1) is sufficient to control apple snail populations. However, black carp reduces the abundance and diversity of non-target macro-invertebrates. Therefore the benefits of the biological control must be weighed against the potential undesirable effects on wetland diversity before adopting in the pest management. To maximize the control efficacy, mechanical methods to eradicate adult snails, for instance hand-picking in the shallow water, should be implemented with biological control effort in an integrated apple snail management program.

In this thesis I examined factors limiting population success of apple snails (Pomacea spp.) in Florida wetlands. First, I examined effects of summertime hydropattern in replicated wetlands on reproduction and juvenile growth. Annual reproductive effort of Florida apple snails (Pomacea paludosa) and the invasive apple snail P. maculata under was not affected by deeper water in the summer. When juvenile P. paludosa were forced to grow in reportedly favorable and relatively deeper summertime depths survival was high between treatments and growth was unaffected. In the other chapter I examined interactions between the two snails with a series of observations and experiments. I examined historical data on the assemblages and found that P. paludosa were locally extinguished in one of the wetlands within six years of invasion by P. maculata. Two field experiments gave conflicting results about the importance of interspecific inhibition of P. paludosa by the invasive snail, but in either case resource reduction could not be demonstrated. Lab exposure to P. maculata chemical cues strongly inhibited P. paludosa growth, although P. paludosa did not behaviorally avoid mucus of P. maculata. In mesocosms Pomacea paludosa growth was reduced with increasing exposure to adult P. maculata waterborne cues, and the results suggest that contact with mucus at a low exposure may even have a greater inhibiting effect. This interspecific direct chemical growth inhibition was novel for gastropods, but could be more generally important, and its potential impacts to P. paludosa populations should be explored further. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2020. / FAU Electronic Theses and Dissertations Collection