Gastropod Populations Research Articles

Limited Migration From Physiological Refugia Constrains the Rescue of Native Gastropods Facing an Invasive Predator.

Biological invasions have caused the loss of freshwater biodiversity worldwide. The interplay between adaptive responses and demographic characteristics of populations impacted by invasions is expected to be important for their resilience, but the interaction between these factors is poorly understood. The freshwater gastropod Amnicola limosus is native to the Upper St. Lawrence River and distributed along a water calcium concentration gradient within which high-calcium habitats are impacted by an invasive predator fish (Neogobius melanostomus, round goby), whereas low-calcium habitats provide refuges for the gastropods from the invasive predator. Our objectives were to (1) test for adaptation of A. limosus to the invasive predator and the low-calcium habitats, and (2) investigate if migrant gastropods could move from refuge populations to declining invaded populations (i.e., demographic rescue), which could also help maintain genetic diversity through gene flow (i.e., genetic rescue). We conducted a laboratory reciprocal transplant of wild F0 A. limosus sourced from the two habitat types (high calcium/invaded and low calcium/refuge) to measure adult survival and fecundity in home and transplant treatments of water calcium concentration (low/high) and round goby cue (present/absent). We then applied pooled whole-genome sequencing of 12 gastropod populations from across the calcium/invasion gradient. We identified patterns of life-history traits and genetic differentiation across the habitats that are consistent with local adaptation to low-calcium concentrations in refuge populations and to round goby predation in invaded populations. We also detected restricted gene flow from the low-calcium refugia towards high-calcium invaded populations, implying that the potential for demographic and genetic rescue is limited by natural dispersal. Our study highlights the importance of considering the potentially conflicting effects of local adaptation and gene flow for the resilience of populations coping with invasive predators.

Impact of Mining of Marine Gastropods Habitat: Basis for Information Education Communication(IEC) for Environmental Sustainability

An alarming socio-economic and environmental impact of mining in the Municipality of Carrascal, Surigao del Sur led to this study. It is important to assess the impact of mining on marine habitats and the diversity of gastropods in the area. The collection of gastropods is done in the selected four sampling areas, which include Brgy. Adlay, Brgy. Caglayag, Brgy. Dahican, and Brgy. Gango. Based on the sampling, 228 marine gastropod species were collected, consisting of 53 genera belonging to 10 families. The findings highlight the low diversity of the marine gastropods in the study area as the diversity index is less than 1.99. In addition, the physico-chemical parameter assessment of the study area reveals conditions ranging from slightly alkaline water with low oxygen content to very warm temperatures. These conditions suggest a delicate balance in the aquatic ecosystems, which could be sensitive to changes and affect marine gastropod populations and distributions. With regards to the average concentration of nickel (mg/kg) sediments as a result of the mining activities in the study area, the atomic absorption spectrophotometry result shows that Brgy. Gango is heavily polluted in comparison to other sampling areas. Additionally, the multiple regression analysis reveals that there is a positive and significant association between the nickel concentration and the diversity of gastropods in Brgy. Gango. This could indicate that some gastropod species, specifically those that are found in areas with high nickel concentrations, have acquired tolerance to nickel pollution. However, the regression analysis reveals that in the other sampling sites, such as Brgy. Adlay and Brgy. Caglayag, the presence of nickel sediments as a result of mining activities has a negative and significant impact on the marine habitat and diversity of gastropods. The findings suggest the importance of developing an information education and communication program addressing the negative impacts of mining and promoting environmental sustainability in the research locale.

Glutamate, glycine, and especially the secretions of Ruditapes phillipinarum induce efficient foraging by juvenile Rapa whelks

Chemical signals are known to influence interactions within and among species of aquatic organisms, including gastropods. However, despite the indispensable roles of chemical signals in species interactions, little is known about their effectiveness, especially in gastropods. The rapa whelk Rapana venosa (Valenciennes, 1846) is an ecologically and economically important gastropod, but it has also become a global invasive species. Currently, bottlenecks exist in the breeding of R. venosa related to foraging behaviour and efficiency in juveniles, while significant problems also exist in controlling invasive populations of the gastropod. Here, we aimed to identify chemical signaling molecules that could effectively improve their foraging behaviour and efficiency and potentially solve the bottlenecks in aquaculture production and control the invasiveness of R. venosa. The foraging behaviour of R. venosa during the search phase was evaluated in response to various signaling molecules as to activity time, motion path, and successful perception rate, and a standard scoring metric was proposed. The results showed that bivalve (Ruditapes philippinarum) secretion and glutamic acid and glycine, could effectively induce foraging behaviour in R. venosa. In contrast, 4-dodecylbenzene sulfonic acid and dodecyl sulfate, did not induce significant foraging behaviour. The induced foraging behaviour by a single amino acid was less effective than that of the entire bivalve secretion. These findings could be helpful in improving breeding efficiency, efficient trapping, and controlling invasive populations of aquatic gastropods.

Mangrove gastropod distribution based on dominant vegetation classes and their relationship with physicochemical characteristics on fringe mangroves of Lembongan Island, Bali, Indonesia

Abstract. Ernawati NM, Dewi APWK, Sugiana IP, Dharmawan IWE, Ma’ruf MS, Galgani GA. 2024. Mangrove gastropod distribution based on dominant vegetation classes and their relationship with physicochemical characteristics on fringe mangroves of Lembongan Island, Bali, Indonesia. Biodiversitas 25: 156-166. Mangrove ecosystems are important in supporting diverse marine life, offering refuge, reproductive grounds, and sustenance to various species. However, mangroves possess distinct zoning patterns determined by dominant species due to environmental variations that significantly impact the biodiversity of biota, particularly gastropods. A study on the Indonesian island of Nusa Lembongan revealed distinct communities of coexisting gastropod species in each mangrove vegetation zone. We discovered 29 distinct species of mangrove gastropods, with the Sonneratia mangrove zone having the most and the Lumnitzera zone having the least. Certain species, including Amphidromus perversus, Cerithium adustum, and Echinolittorina sundaica, were detected in only one of the mangrove zones. In each mangrove zone, the composition of gastropod species changed depending on the substrate type, e.g., soil, mangrove trunks, or mangrove leaves. The Shannon-Wiener diversity index values range from low to high diversity, and the community structure index values in mangrove zones vary. The evenness index varied by region, with Avicennia, Bruguiera, and Sonneratia having the highest index value. The findings indicate that mangrove vegetation zones are essential for maintaining diverse gastropod populations, with distinct composition and abundance patterns influenced by the distance of each mangrove zone from the ocean. This data may influence conservation efforts to preserve mangrove habitats and the diverse array of organisms that depend on them.

Morphometric variations of two patellid limpets between artificial breakwaters and natural reefs

Artificial shorelines often differ from natural reefs in shape, composition, and habitat complexity. They promote higher accumulation of pollutants and increased physiological stress, which lead to changes in species distributions and ecosystem functioning. This can promote trophic shifts and reduced genetic diversity of gastropod populations inhabiting artificial shorelines and might promote morphological changes, which may influence behaviour, vulnerability to predation, feeding efficiency, sex ratios, reproductive development, and overall fitness. This study explores inter- and intraspecific shell morphometric variations in Patella rustica and P. caerulea between breakwaters (ripraps) and natural reefs in three sites of Ceuta (North Africa, Spain), including a physicochemical assessment of the studied locations: shore orientation, inclination and wave exposure, and substratum nature, heterogeneity and roughness. Limpets on artificial substrata had a slightly smaller extra-visceral cavity and flattened shell profile, which suggests that the desiccation and temperature stress driven by the lithological composition and roughness of the studied substrata might have influenced the registered shell shape variation. However, the high morphometric variation registered for both species across sites and substrata suggests that limpets' morphology might be responding to a complex interaction of environmental and ecological factors rather than solely rock type. The findings of this study highlight the complex interplay between rock type and local environmental conditions in shaping patellid limpets’ shell morphology and provide insights into the adaptive mechanisms that drive shell shape variation in limpet populations in the face of coastal sprawl and anthropogenic global change.

Gastrópodes potenciais hospedeiros intermediários de parasitos na região do Parque Nacional dos Lençóis Maranhenses/Brasil, um destino turístico internacional

Abstract Several aquatic ecosystems present favorable conditions for the establishment of freshwater gastropod populations in Maranhão (Brazil). However, research on these snails in this Brazilian state is more focused on Baixada Maranhense, an endemic area for schistosomiasis in Maranhão. Considering the need to expand information on the occurrence of limnic gastropods in Maranhão, a qualitative study was carried out in the Microregion of Lençóis Maranhenses. The capture of freshwater snails was carried out between June 2016 and November 2019. Were obtained 3,244 specimens of freshwater gastropods: 2,372 specimens of Biomphalaria straminea (Dunker, 1848); 17 specimens of Biomphalaria schrammi (Crosse, 1864); 19 specimens of Drepanotrema lucidum (Pfeiffer, 1939); 115 specimens of (Hydrobiidae; Rissooidea); 24 specimens of Physa marmorata Guilding, 1828; 73 specimens of Pomacea maculata (Perry, 1810); 613 specimens of Pomacea sp. (Perry, 1810). Were also found 11 shells of Biomphalaria glabrata (Say, 1818). The greatest richness of snails was observed in Tutóia. The most abundant species during the study was B. straminea (73,45%). Pomacea sp. was the most representative species with constant frequency (57,15%) in the Lençóis Maranhenses Microregion, present in lentic and lotic ecosystems. The forecast maps indicate the possibility of occurrence and establishment of freshwater gastropods species throughout the investigated region. The presence of gastropods that are hosts of parasites represents a risk to human health, especially in the Lençóis Maranhenses area, which is one of Brazil's tourist destinations. Studies on the occurrence and distribution of limnic gastropods are of great relevance for understanding the conservation status of existing species. Furthermore, they are necessary to monitor snails that act as parasite hosts.

Morphological Variation between Life and Death Gastropod Populations in the Nile Delta: A Pollution-Induced Evolution

Wetland ecosystems of the Nile Delta face severe threats due to natural climatic changes and anthropogenic activities. Life and death assemblage comparisons can be implemented as a historical record to detect anthropogenic-induced environmental changes in the past few decades. A geometric morphometric approach was applied to quantify the pollution-induced morphological variation between life and death populations of the gastropod Melanoides tuberculata. The results indicated that life populations differ significantly from the death ones, where the first tend to be much smaller, more globular, and with a depressed aperture and whorl section. In addition, the phenetic diversity of the life populations was also decreased, and the allometric growth was shifted. These morphological changes in the life populations are well-known adaptations for reducing the cost of shell maintenance in polluted water. No distinct morphospace was found between life populations from different habitats, suggesting that habitats have no significant role in the current pollution-induced evolution.

Long‐term responses to large‐scale disturbances: spatiotemporal variation in gastropod populations and communities

The Anthropocene is characterized by complex, primarily human‐generated, disturbance regimes that include combinations of long‐term press (e.g. climate change, pollution) and episodic pulse (e.g. cyclonic storms, floods, wildfires, land use change) disturbances. Within any regime, disturbances occur at multiple spatial and temporal scales, creating complex and varied interactions that influence spatiotemporal dynamics in the abundance, distribution and biodiversity of organisms. Moreover, responses to disturbance are context dependent, with the legacies of previous disturbances affecting responses to ensuing perturbations. We use three decades of annual data to evaluate the effects of repeated pulse disturbances and global warming on gastropod populations and communities in Puerto Rico at multiple spatial scales. More specifically, we quantify 1) the relative importance of large‐scale and small‐scale aspects of disturbance on variation in abundance, biodiversity and species composition; and 2) the spatial scales at which populations and communities integrate information in the spatially heterogenous environments created by disturbances. Gastropods do not exhibit consistent decreases in abundance or biodiversity in association with global warming: abundance for many species has increased over time and species richness does not evince a temporal trend. Nonetheless, gastropods are sensitive to hurricane severity, spatial environmental variation and successional trajectories of the flora. In addition, they exhibit context dependent (i.e. legacy effects) responses that are scale dependent. The Puerto Rican biota has evolved in a disturbance‐mediated system. This historical exposure to repeated, severe hurricane‐induced disturbances has imbued the biota with high resistance and resilience to the current disturbance regime, resulting in an ability to persist or thrive under current environmental conditions. Nonetheless, these ecosystems may yet be threatened by worsening direct and indirect effects of climate change. In particular, more frequent and severe hurricanes may prevent the establishment of closed canopy forests, negatively impacting populations and communities that rely on these habitats.

Terrestrial gastropod species-specific responses to forest management: Implications for Parelaphostrongylus tenuis transmission to moose

Landscape management can influence the distribution, abundance, and diversity of the terrestrial gastropods that host known parasites of managed species of ungulates. Multiple taxa of terrestrial gastropods are important intermediate hosts in the lifecycle of the parasitic nematode Parelaphostrongylus tenuis, for which white-tailed deer (Odocoileus virginianus) are definitive hosts. Moose (Alces alces) become infected with P. tenuis when they incidentally ingest gastropod intermediate hosts, leading to morbidity and mortality. Populations of moose in Minnesota have declined and P. tenuis infection has been identified as a leading cause of mortality. We investigated the role of forest management disturbance on the terrestrial gastropod community, and specifically known intermediate host species of P. tenuis, on the Grand Portage Indian Reservation in northeastern Minnesota, USA, where moose are an important subsistence species to the Grand Portage Band of Lake Superior Chippewa. Field crews surveyed gastropods through timed searches of soil and litter, and opportunistic collections from browse and pellets of white-tailed deer and moose. We digested all identified gastropods to determine prevalence of P. tenuis infection. We examined gastropod community responses to management and forest cover type using multivariate regressions. We additionally used regressions to examine total gastropod richness and abundance, as well as P. tenuis intermediate host responses to cover type, soil moisture class, canopy cover, treatment, and years since treatment. Digestions detected no infected gastropods from the 621 identified specimens. Gastropod community assemblages differed with recent understory treatment, but no other predictors. Total gastropod abundance, richness, and host abundance (liberal definition, including Deroceras spp.) were lower in sites treated within the last five years. For known intermediate host taxa, we observed species-specific responses to forestry treatments through time. Specifically, Deroceras spp. recolonized sites post-treatment (0–30 years), Discus cronkhitei were higher in abundance immediately following treatment, and the Succinea ovalis group, along with pooled intermediate hosts, displayed no discernable patterns. Our results underscore the complexity of P. tenuis lifecycles and transmission dynamics to moose, the importance of management disturbance and disturbance frequency in regulating gastropod populations, and the potential of forest management treatments to reduce P. tenuis infection in moose.

Aquatic Hermaphrodite Snails Exposed to Polychlorinated Biphenyls (PCBs) Experience Increased Mortality, Reduced Reproduction, and Endocrine Disruption

Populations of freshwater gastropods are decreasing globally. To investigate one aspect of decline, we exposed the benthic dwelling hermaphroditic snail Planorbella (= Helisoma) trivolvis (Say) (Marsh Rams-horn) to polychlorinated biphenyls (PCBs). Marsh Rams-horn is a simultaneous hermaphrodite, suggesting that disruption of reproductive success is independent of snail interaction and more dependent on internal controls. We examined the impact of exposure to PCBs on mortality, reproductive success, and tissue hormone concentrations. Exposure to Aroclor®1254 in concentrations found in natural habitats caused higher mortality and reduced reproductive success. Additionally, tissue estrogens were significantly elevated while testosterone remined unchanged in PCB-exposed snails. Given the importance of hermaphroditic freshwater gastropods in ecosystems, worldwide population decline, and ubiquity of PCBs, identifying the impact of exposure informs our ability to combat population loss.

Long‐term responses of gastropods to simulated hurricanes in a tropical montane rainforest

AbstractClimate‐induced disturbances such as hurricanes affect the structure and functioning of ecosystems, especially those in the Caribbean Basin, where high‐energy storms have long affected ecosystem dynamics. Because climate change will likely continue to alter the frequency and intensity of hurricanes in the Caribbean, it is increasingly important to understand the mechanistic bases for ecosystem responses. Although long‐term surveys and nonmanipulative “natural experiments” provide considerable insight, manipulative experiments are required to decouple confounded factors associated with high‐intensity storms. To address this, we exploited a replicated factorial design to experimentally isolate the long‐term effects of canopy opening and debris deposition on population‐ and community‐level characteristics of gastropods in the Luquillo Experimental Forest of Puerto Rico. The canopy trimming experiment included four treatments: (1) the reference treatment received no manipulations; (2) canopy trimmed, but debris from trimming not deposited on the forest floor (trim only); (3) canopy not trimmed, but debris deposited on the forest floor (debris only); and (4) canopy trimmed and debris deposited on the forest floor (trim and debris). After 10 years, the trim and debris treatment was repeated to simulate reoccurring hurricane events, whereas the trim‐only and debris‐only treatments were not subject to additional manipulation at this time. We evaluated responses to treatment and time for gastropod populations (abundance) and communities (biodiversity and composition). Population‐level responses were species specific. Three species and total gastropod abundance exhibited consistent responses to treatments regardless of time, four species exhibited consistent temporal trends regardless of treatment, and five species exhibited an interaction in which the effects of time depended on treatment. In general, point‐, α‐, and γ‐biodiversity decreased through time, whereas β‐biodiversity increased through time. Gastropod populations and communities were resistant and resilient to the simulated disturbances, exhibiting quick recovery from any short‐term changes in abundance or biodiversity. From an evolutionary perspective, long‐term exposure to hurricane‐induced disturbances likely leads to species‐specific adaptations that enhance resistance and resilience.

Interactions of Undescribed Drilus Beetle Larvae with Pestiferous Limicolaria flammea (Gastropoda: Achatinidae): Are There Prospects for Biocontrol?

The garden snail, Limicolaria flammea is a seasonal pest of several horticultural crops in most of the agroecological areas in Nigeria. The level of damage to crops is especially enormous in the South because of its ability to feed on different crops and the timing of abundance, the early rain season, which usually coincide with onset of rain-fed crop production which expose seedlings and grown-up crop plants to serious damage. In this study, we recorded occurrence data of Limicolaria flammea in okra, carrot, sweet potato, lettuce and maize within a single multi-crop organic farm in order to understand its food preference. Activities of the predatory beetle larvae, Drilus sp was observed within the environment. The appearance of the larvae was described and its interaction with L. flammea was studied to generate some data on the proportions of snail mortality caused by Drilus sp and other mortality factors that naturally regulate the population dynamics of L. flammea within the environment. There was no statistically significant difference in the average number of snails recorded in the different cropping fields [F (4,15) =1.369, P=0.291]. The activities of Drilus larvae against L. flammea was higher in okra and carrot plots as snail mortality due to the larvae attack were significantly higher compared to what was recorded in other crop plots [F (4, 30) =3.998, P=0.01].The Drilus larvae predate on L. flammea by appertural entry, biting through the soft tissues around the mantle to gain entrance and moult into instar larvae within the snail shell in 15-20 days, leaving its exuviae behind in the shell in all the specimens observed (n=40). The Drilus species being reported in this study is morphologically distinct from other described species in available literature. The study suggested that the Drilus species is less known and there are potentials that the species could be useful in inundative biocontrol approaches for the management of pestiferous gastropod populations.

Response of freshwater snails to invasive crayfish varies with physiochemical exposure cues and predator experience

Abstract Invasive species represent one of the greatest threats to freshwater biodiversity. The successful colonisation and establishment of populations of invasive predators in waterbodies may expose the pre‐existing fauna to novel predation strategies to which they are not pre‐adapted. Despite this, there is still a paucity of information on behavioural responses within biological invasion research. Here we present the results of a series of 24‐hr mesocosm experiments that examined the handling times and responses of four Gastropoda species (Radix balthica, Physa fontinalis, Gyraulus albus, Potamopyrgus antipodarum) exposed to physical and chemical cues associated with the invasive crayfish, Pacifastacus leniusculus. We specifically considered four physicochemical treatments: (1) control (no cue); (2) conspecific chemical; (3) crayfish chemical; and (4) physical presence (but confined). In addition, we considered the effect of previous predator experience of the gastropod (predator naïve or aware) and additonally assessed survivourship in encounter trials. Handling time was found to vary significantly between gastropod species with survivorship from predation mirroring handling times observed. P. fontinalis required the greatest handling time (average of 58 s) and had the highest survivorship rate. In marked contrast, P. antipodarum were rapidly consumed, with an average handling time of 6 s and no individuals surviving after 4‐hr in the encounter trials. Handling time varied by gastropod size but also shell morphology. The response to the physical and chemical cues varied between gastropod species. R. balthica and P. fontinalis demonstrated vertical avoidance behaviour most readily whilst P. albus and P. antipodarum displayed active migration only to the physical presence cue. In most instances, the response was immediate with vertical migration (above the reach of the crayfish at 15 cm on the mesocosm wall) evident within an hour. Predation regime was found to exert a significant effect on the avoidance response of the gastropods. This was particularly notable in relation to the crayfish chemical cue and to a lesser extent the injured conspecific chemical cue. Predator‐naïve populations reacted with strong vertical avoidance behaviour in response to the crayfish chemical cue, whilst, in the case of P. fontinalis, predator aware individuals reacted most strongly to the conspecific chemical cue. Our results highlight the multifaceted challenge of understanding predator–prey relationships, particularly in the face of novel invasive species, and provide much‐needed evidence to begin to tackle this complex process. Gaining a better understanding of such interactions is vital in order to underpin management strategies and to enable evolutionary trajectories in invaded ecosystems to be assessed. Previous predator experience in combination with species identity are important attributes in determining predation risk when gastropod populations are exposed to novel predators and their associated predation cues.

Gastropods in the Intertidal Shore of Kota Kinabalu, Sabah (Malaysian Borneo)

Intertidal gastropods provide numerous ecological benefits and are responsible for the dynamics of the intertidal shores habitat and its community assemblages. This study examined the community structure of gastropods in the intertidal shore located near the city of Kota Kinabalu, the capital of Sabah where coastal areas are rapidly developed for various purposes and consequently destroying natural habitats. A total of 36 gastropods species from 15 families were recorded. The Planaxis sulcatus was the most abundant species with a density of 480 ind. m-2 followed by Nodilittorina pyramidalis (182 ind. m-2) and Cellana radiata (97 ind. m-2) respectively. The number of species and their abundance, respectively, are almost three times lower than the number ever recorded for intertidal shores located in non-urban areas or remote locations. This suggests that the rapidly growing coastal urban areas threatening the diversity and abundance of intertidal gastropods. The density of gastropod (i.e. P. sulcatus & N. pyramidalis) was significantly (p<0.05) high at the lower intertidal shore where slope gradient is steeper with rocks and crevices are the major component of substrates compared to the upper or middle zone which is flatter and composed mainly of coral rubble and sand. Our study suggests that gastropod communities in intertidal shores located adjacent to the urban areas are threatened especially by anthropogenic factors such as frequent human visitations and modification of natural habitat. Future development in the intertidal shore should minimise habitat destruction and should consider infrastructures that encourage gastropod populations to grow and highlighting their ecological role for conservation reasons.

Angiostrongylus cantonensis in urban populations of terrestrial gastropods and rats in an impoverished region of Brazil.

The nematode Angiostrongylus cantonensis is the most common cause of neuroangiostrongyliasis (manifested as eosinophilic meningitis) in humans. Gastropod molluscs are used as intermediate hosts and rats of various species are definitive hosts of this parasite. In this study, we identified several environmental factors associated with the presence and abundance of terrestrial gastropods in an impoverished urban region in Brazil. We also found that body condition, age and presence of co-infection with other parasite species in urban Rattus norvegicus, as well as environmental factors were associated with the probability and intensity of A. cantonensis infection. The study area was also found to have a moderate prevalence of the nematode in rodents (33% of 168 individuals). Eight species of molluscs (577 individuals) were identified, four of which were positive for A. cantonensis. Our study indicates that the environmental conditions of poor urban areas (presence of running and standing water, sewage, humidity and accumulated rain and accumulation of construction materials) influenced both the distribution and abundance of terrestrial gastropods, as well as infected rats, contributing to the maintenance of the A. cantonensis transmission cycle in the area. Besides neuroangiostrongyliasis, the presence of these hosts may also contribute to susceptibility to other zoonoses.

Factors influencing Molluscan (Gastropod) populations in Thirumeni Lake, Tamil Nadu, India.

Factors influencing Molluscan (Gastropod) populations in Thirumeni Lake, Tamil Nadu, India.

Study of Gastropods and Bivalves Potential in Mangrove Ecosystem in Sebubus , Paloh

This study aims to obtain data on the abundance of gastropods and bivalves, the density, and the diversity in the mangrove ecosystem in Sebubus Village, Paloh District. The data obtained from this study shed a light in the management of aquatic ecosystems as well as the reference in conserving and identifying mollusks with economic value. Observations from 20 stations revealed that the number of gastropod populations was higher than the population of bivalves. Gastropod abundance was mostly found in Padak and bivalves was mostly found in Engkalan A. Thus, it is necessary to provide information regarding the fishing limits around the mangrove forest o the community. It is necessary to establish a an asylum for gastropods and bivalves as well as support for their sustainability

Locomotor responses to salt stress in native and invasive mud-tidal gastropod populations (Batillaria).

Plasticity in salt tolerance can be crucial for successful biological invasions of novel habitats by marine gastropods. The intertidal snail Batillaria attramentaria, which is native to East Asia but invaded the western shores of North America from Japan 80 years ago, provides an opportunity to examine how environmental salinity may shape behavioral and morphological traits. In this study, we compared the movement distance of four B. attramentaria populations from native (Korea and Japan) and introduced (United States) habitats under various salinity levels (13, 23, 33, and 43 PSU) during 30 days of exposure in the lab. We sequenced a partial mitochondrial CO1 gene to infer phylogenetic relationships among populations and confirmed two divergent mitochondrial lineages constituting our sample sets. Using a statistical model‐selection approach, we investigated the effects of geographic distribution and genetic composition on locomotor performance in response to salt stress. Snails exposed to acute low salinity (13 PSU) reduced their locomotion and were unable to perform at their normal level (the moving pace of snails exposed to 33 PSU). We did not detect any meaningful differences in locomotor response to salt stress between the two genetic lineages or between the native snails (Japan vs. Korea populations), but we found significant locomotor differences between the native and introduced groups (Japan or Korea vs. the United States). We suggest that the greater magnitude of tidal salinity fluctuation at the US location may have influenced locomotor responses to salt stress in introduced snails.

Impact of fire and the recovery of molluscs in south‐east Australian salt marsh

SummaryFire has long been recognised as a natural force in structuring Northern Hemisphere salt marshes, yet little is known about the impact of fire on molluscs and native vegetation dynamics of Southern Hemisphere coastal salt marshes. Following a fire at Ash Island, Hunter River New South Wales, Australia in the summer 2012, we assessed patterns of recovery through time of gastropod populations and resident salt marsh vegetation including biomass for three keystone native plant species, Native Rush (Juncus kraussii Hochst.), a chenopod (Sarcocornia quinqueflora Bunge ex Ungen‐Sternberg A.J. Scott), Salt Couch (Sporobolus virginicus, L. Kunth) and the invasive Spiny Rush (Juncus acutus). In temperate east‐coast Australian salt marshes, Spiny Rush is displacing native salt marsh vegetation. After twelve months, the biomass of Native Rush recovered to similar pre‐burn levels. While fire affected the abundance, richness and composition of the gastropod assemblage differences were also largely driven by spatial variability. Gastropod assemblages associated with two of the higher elevation native species (Native Rush and Salt Couch) were impacted the most by fire. Greater abundance (between 1 and 5 orders of magnitude difference in abundance) and richness of gastropods were found in unburnt compared with burnt Native Rush and Salt Couch vegetation, while more gastropods were found in Spiny Rush in one site. Species prevalent in burnt vegetation included larger species of gastropods Ophicardelus ornatus (Ferussac, 1821) and Phallomedusa solida (Martens, 1878) with an unexpected spike in number of the smaller gastropod Tatea huonensis (Tenison‐Woods, 1876) in the spiny rush at one site only. In salt marsh habitats, many gastropods have planktonic larval dispersal stages which are dependent on the tidal height for transport and the structural complexity provided by vegetation at settlement. Since fire appears to negatively affect salt marsh gastropod populations within structurally complex Native Rush and Salt Couch, due consideration of the importance of these refuges for gastropods is recommended when fire or other disturbances occur in ecologically endangered salt marsh in the Southern Hemisphere. Managers need to consider spatial heterogeneity of molluscs and their recovery in the event of fire in Southern Hemisphere salt marshes.

A cascade of biological invasions and parasite spillback in man-made Lake Kariba

Parasite spillback, the infection of a non-indigenous organism by a native parasite, is a highly important although understudied component of ecological invasion dynamics. Here, through the first analysis of the parasite fauna of lymnaeid gastropods of Lake Kariba (Zimbabwe). We illustrate how the creation of an artificial lake may lead to a cascade of biological invasions in which an invasive aquatic plant promotes the proliferation of invasive gastropods, which in turn alters the epidemiology of trematodiases of potential medical and veterinary importance. Using a new multiplex Rapid Diagnostic PCR assay, we assessed the prevalence of Fasciola sp. infections in the gastropod populations. Both gastropod hosts and trematode parasites were identified using DNA barcoding. We provide the first record of the invasive North-American gastropod Pseudosuccinea columella in Lake Kariba. This species was found at 14 out of 16 sampled sites and its abundance was strongly positively correlated with the abundance of the invasive South-American water hyacinth (Eichhornia crassipes). About 65% of the P. columella specimens analysed were infected with a hitherto unknown Fasciola species. Phylogenetic analyses indicate close affinity to Fasciola hepatica and F. gigantica, which cause fasciolosis, an important liver disease affecting both ruminants and humans. In addition, another non-native Lymnaeid species was found: a Radix sp. that clustered closely with a Vietnamese Radix species. Radix sp. hosted both amphistome and Fasciola trematodes. By linking an invasion cascade and parasite spillback, this study shows how both processes can act in combination to lead to potentially important epidemiological changes.