Tarebia Granifera Research Articles

The role of gastropods in African swine fever virus ecology

The spread of the African swine fever virus (ASF virus) genotype ii in the Eurasian region has been very successful and often inexplicable. The virus spreads rapidly and persists in areas with wild boar populations, but areas without feral pig populations are also affected. The virus has shown the ability to survive for a long time in the environment without a population of susceptible hosts, both pigs and Ornithodoros soft ticks. Published data indicated that ASF viruses persist significantly longer in an environment with some freshwater snails (especially Pomacea bridgesii, Tarebia granifera, Asolene spixii, Melanoides tuberculate, and Physa fontinalis), compared to freshwater without snails. Data obtained in this study suggest that gastropods theoretically can be the hosts of the ASF virus. Also, we have proven the possibility of long-term existence of an infectious virus when infected in vitro.

Distribution, abundance, population structures, and potential impacts of the invasive snail, Tarebia granifera in aquatic ecosystems of north-eastern South Africa.

Aquatic ecosystems globally have been invaded by molluscs. Tarebia granifera is a highly successful invader, often becoming the dominant aquatic invertebrate species in an invaded ecosystem. Resultingly, it has been suggested that T. granifera may have severe negative impacts on these invaded ecosystems. Limited information is available regarding the population structures and densities of T. granifera, particularly in invaded countries such as South Africa, and information on this could assist in developing management and control strategies for this invasive species. The present study aimed to assess the current distribution, densities, and population structures of T. granifera in invaded habitats on the Limpopo and Phongolo River systems in South Africa. This was accomplished by collecting aquatic molluscs from sites across these systems. Water quality parameters were measured at each site and water samples were collected for chemical nutrient analyses. The density of snails was determined for each site and the population size and structure as well as birth rate was calculated for T. granifera. Tarebia granifera was found to be the dominant molluscan species in habitats where it was present and all size classes from newborn to mature adults were found throughout at some of the highest densities globally. Worryingly, native molluscan species, were often absent or in much lower densities than reported in literature at sites where T. granifera was present, suggesting a negative effect on the native molluscan density and diversity. Contrary to most previous studies, there were no significant correlations between T. granifera and the selected water quality parameters. Higher densities and newborn recruitment of T. granifera were observed in the spring than in autumn, likely in response to shifts in environmental conditions. This study provides crucial insights into the population structure, densities, and impacts of T. granifera in invaded habitats, particularly for relatively newly invaded regions such as southern Africa.

One Health monitoring reveals invasive freshwater snail species, new records, and undescribed parasite diversity in Zimbabwe

BackgroundSnail-borne trematodes afflict humans, livestock, and wildlife. Recognizing their zoonotic potential and possible hybridization, a One Health approach is essential for effective control. Given the dearth of knowledge on African trematodes, this study aimed to map snail and trematode diversity, focusing on (i) characterizing gastropod snail species and their trematode parasites, (ii) determining infection rates of snail species as intermediate hosts for medically, veterinary, and ecologically significant trematodes, and (iii) comparing their diversity across endemic regions.MethodsA cross-sectional study conducted in 2021 in Chiredzi and Wedza districts in Zimbabwe, known for high human schistosomiasis prevalence, involved malacological surveys at 56 sites. Trematode infections in snails were detected through shedding experiments and multiplex rapid diagnostic polymerase chain reactions (RD-PCRs). Morphological and molecular analyses were employed to identify snail and trematode species.ResultsAmong 3209 collected snail specimens, 11 species were identified, including schistosome and fasciolid competent snail species. We report for the first time the invasive exotic snail Tarebia granifera in Zimbabwe, which was highly abundant, mainly in Chiredzi, occurring at 29 out of 35 sites. Shedding experiments on 1303 snails revealed a 2.24% infection rate, with 15 trematode species identified through molecular genotyping. Five species were exclusive to Chiredzi: Bolbophorus sp., Schistosoma mansoni, Schistosoma mattheei, Calicophoron sp., and Uvulifer sp. Eight were exclusive to Wedza, including Trichobilharzia sp., Stephanoprora amurensis, Spirorchid sp., and Echinostoma sp. as well as an unidentified species of the Plagiorchioidea superfamily. One species, Tylodelphys mashonensis, was common to both regions. The RD-PCR screening of 976 non-shedding snails indicated a 35.7% trematode infection rate, including the presence of schistosomes (1.1%) Fasciola nyanzae (0.6%). In Chiredzi, Radix natalensis had the highest trematode infection prevalence (33.3%), while in Wedza, R. natalensis (55.4%) and Bulinus tropicus (53.2%) had the highest infection prevalence.ConclusionsOur xenomonitoring approach unveiled 15 trematode species, including nine new records in Zimbabwe. Schistosoma mansoni persists in the study region despite six mass deworming rounds. The high snail and parasite diversity, including the presence of exotic snail species that can impact endemic species and biomedically important trematodes, underscores the need for increased monitoring.Graphical

Multiple invasions and predation: The impact of the crayfish Cherax quadricarinatus on invasive and native snails

AbstractThe pace of biological invasions has increased in recent decades, leading to multiple invasions and the potential dominance of invasive species, destabilizing local ecological networks. This provides opportunities to study new ecological species interactions, including predation. Tropical freshwaters have been particularly concerned by aquatic invasions and we focused here on the Martinique island (Lesser Antilles). We examined the predator–prey relationships involving invasive Thiarid snails (Tarebia granifera and Melanoides tuberculata) and the native Neritina punctulata, both confronted with a newcomer predator, the redclaw crayfish (Cherax quadricarinatus). We conducted several mesocosm experiments to assess the impact of crayfish predation on snail survival and the passive and active antipredator responses of snails. A first experiment indicated snail survival rates between 50% and 80%, depending on crayfish size and sex. Notably, there was a negative correlation between snail survival and male crayfish size and the predation method (shell crushing vs. “body sucking”) varied with crayfish size. The second experiment suggested no refuge size for snails, with both very small (<5 mm) and very large (>5 mm) unable to escape predation, regardless of crayfish size (from 77 to 138 mm) or sex. Finally, we investigated the escape behavior of Thiarids regarding three crayfish cues. Melanoides tuberculata tend to bury in the substrate and T. granifera to climb up aquarium walls, what was expected from their shell morphologies, and both responding to crayfish cues within minutes. Overall, C. quadricarinatus proves to be an efficient snail predator with limited escape options for snails, potentially contributing to the decline of certain snail populations in Martinique. This omnivorous predator might impact other native species across different groups, including shrimps and fish. Our study underscores the urgent need for monitoring efforts, solidifying the redclaw crayfish reputation as a dangerous invasive species for freshwater macrobenthic faunas worldwide.

Community composition of invasive, outbreak, and non-pest snail species along a source spring-to-fishpond gradient in a spatially structured aquacultural region

Agricultural lands are integrated into and interact with natural areas. Such is the case of Emek HaMa'ayanot, northern Israel, comprising a springs-rich area characterized by multiple land-uses, including spring-water-based aquaculture, recreational springs, and nature reserves. Aquacultural farms suffer from pest snails that carry fish disease; in the study region, these species are invasive (Thiara scabra, Tarebia granifera, Pseudosuccinea columella) and outbreak endemic (Melanoides tuberculata). Previous snail control efforts have focused on individual fishponds without considering management on larger environmental scales in the waterways from the source springs to the fish farms. To broaden our understanding of the status of the pest snail problem in the study area prior to suggesting environmental managerial solutions, we quantified changes in the community composition of snail species along the springs-to-fishponds gradients in a spatially explicit system. We found a remarkable increase in pest snail abundances along these gradients, indicating that pest snails might be invading upstream towards the springs. There were always nearly 100% pest snails in the endpoint sites for water tracks that ended in fishponds. Moreover, pest snails dominated the site when it was used as a fishpond, even though the site was also a spring. In contrast, in a water track that does not end in a fish farm, the relative abundances of non-pest snail species was similar between the source spring and the downstream endpoint, in spite of an increase in pest snail abundance at a midpoint site. These results suggest that invasive pest snails are actively moving upstream and that the fishponds have a marked upstream effect on the ability of non-pest snails to resist pest species invasions. We suggest further investigation of possible strategies for biocontrol of the observed invasion of the snails into natural areas as a basis for environmental management efforts. Finally, the observations made during this study could have practical global implications for snail management in aquaculture and agriculture, and for the control of snails and snail vectors implicated in animal and human diseases.

Keanekaragaman dan Distribusi Gastropoda Air Tawar di Sungai Ciapus, Jawa Barat, Indonesia

Despite being part of food web and bioindicator in freshwater ecosystems, gastropods are globally jeopardized. Therefore, the occurence of freshwater gastropods need to be assessed. This research aimed to examine diversity and distribution of freshwater gastropods along the Ciapus River in Bogor, West Java, Indonesia. The research was conducted from February to May 2020. Sampling was carried out within limited 15 minutes time period using five 1 × 1 m plots established at each of four survey stations. Gastropods were collected from the bottom of river, rock surface and riverbanks within 15-100 cm of water depth. Environmental parameters were recorded. Data was analyzed using biodiversity index parameters and diversity t-test. The survey collected a total 587 individuals from 7 species of freshwater gastropods. The abundance, species richness and diversity of gastropods in the Ciapus river were different between upstream and downstream, location with high altitude tend to have low number of species. Glyptophysa stagnalis became the only species recorded from upstream area. Meanwhile, there were 4 species, which were collected in other three stations and 2 species that recorded from two stations. In three stations, Tarebia granifera was the most dominant species.

Study of Gastropod Community Structure After Development of Tourism Activities on the Senjoyo River

It is thought that the development of the Senjoyo River as a tourist attraction in Semarang Regency will cause changes to the natural ecosystem in the area, one of which is changing the structure of the existing gastropod community. This research is a quantitative analysis research using a survey method that aims to examine the structure of the gastropod community after the development of tourism activities on the Senjoyo River. Gastropod samples were taken from 10 different observation stations along the Senjoyo River, which are located at 7˚22'23"S and 110˚31'37"E. Observation station locations were determined by the purposive random sampling method, based on tourism activity density. The result showed types of gastropods that were found in the Senjoyo River namely, Sulcospira testudinaria, Tarebia granifera, Brotia costula, Thiara scraba, and Melanoides tuberculata with clustered distribution patterns (Id>1). Statistical analysis showed that location affected gastropod abundance (Asymp. Sig of 0.043), with the highest abundance found at station seven (45,11 individuals/m2). So station seven, with sandy and muddy substrate conditions, moderate current speed (0.257 m/s), and rarely found human activity, is the most suitable location to support the survival of gastropods in the Senjoyo River. Furthermore, the gastropod community structure indicates environmental changes at observation stations nine and ten, the locations where the most activities and construction of tourism facilities were found. That was indicated by the low diversity (H’= 0.00-0.01) and evenness (E = 0.00) index of gastropods, and there is dominance by Sulcospira testudinaria (C= 0.98-1.00).

Benthic macroinvertebrates community in relation to environmental variables of the Cimandiri River and Estuary, Indonesia

Benthic macroinvertebrates, the community that lives in the river and coastal, play important role in the transfer of organic materials. This study aimed to determine the diversity of it in Cimandiri river and estuary. Also, to understand the relation between the community with environmental variables. The research was conducted in September and November 2020, which taken from 10 locations at Cimandiri waters. Benthic macroinvertebrates were collected using the Ekman grab sampler with three replications. Moreover, physicochemical parameters of water and sediment were measured. In general, about 35 taxa belonging to six Classes, including Gastropod, Bivalve, Insect, Malacostraca, Clitellata, and Polychaeta have been found during sampling. Furthermore, Stenelmis sp., one of Insects was predominant benthic invertebrates in the river, whereas Tarebia granifera predominated inhabit the estuary. Margalef richness and Shannon-Wiener diversity index in the river area were about 2.69 and 1.47, while in the estuary was around 1.59 and 0.87. Canonical Correspondence Analysis shows that the number of individuals of 25 taxa tended to correlate with water temperature, TDS, salinity, total of nitrate (TN), total of phosphorus (TP), and total of organic matters (TOM). While, 10 other taxa correlated with pH, turbidity, dissolved of oxygen (DO), ammonia, and the total of suspended solids (TSS).

Trematodes obtained from snails in giant gourami ponds supplied by well water in Tien Giang province, Vietnam

A study on trematode obtained from freshwater snails in 30 grow-out giant gourami ponds supplied by well water was conducted in Chau Thanh district, Tien Giang province, Vietnam. The snails were sampled in the flooding season (October 2020), the intermediary season (January 2021) and the non-flooding season (April 2021). Eight snail species belonging to 8 genera, 4 families were found including Sermyla tornatella (48.6%), Sinotaia lithophaga (19.3%), Filopaludina sumatrensis (15.4%), Melanoides tuberculata (6.4%), Pomacea sp. (4.7%), Bithynia siamensis (4.2%), Thiara scabra (0.8%) and Tarebia granifera (0.6%). Cercariae were recovered from only two snail species of Melanoides tuberculata with Xiphidio cercariae and Furcocercous cercariae with a prevalence of 7.4%, and Bithynia siamensis with Xiphidio cercariae and Pleurolophocercous cercariae with the infection rate of 6.9%. The trematodes were found in 8 ponds (26.7%), 7 ponds (23.3%), and 3 ponds (10.0%) in the intermediary season, the non-flooding season, and the flooding season, respectively (P>0.05). More research on the epidemiology of trematodes in snails in fishponds should be done to contribute to food safety and sustainable aquaculture.

Spatial and seasonal distribution of human schistosomiasis intermediate host snails and their interactions with other freshwater snails in 7 districts of KwaZulu-Natal province, South Africa

The spatial and seasonal distribution, abundance, and infection rates of human schistosomiasis intermediate host snails and interactions with other freshwater snails, water physicochemical parameters, and climatic factors was determined in this study. A longitudinal malacology survey was conducted at seventy-nine sites in seven districts in KwaZulu-Natal province between September 2020 and August 2021. Snail sampling was done simultaneously by two trained personnel for fifteen minutes, once in three months. A total of 15,756 snails were collected during the study period. Eight freshwater snails were found: Bulinus globosus (n = 1396), Biomphalaria pfeifferi (n = 1130), Lymnaea natalensis (n = 1195), Bulinus tropicus (n = 1722), Bulinus forskalii (n = 195), Tarebia granifera (n = 8078), Physa acuta (n = 1579), and Bivalves (n = 461). The infection rates of B. globosus and B. pfeifferi are 3.5% and 0.9%, respectively. In our study, rainfall, pH, type of habitats, other freshwater snails and seasons influenced the distribution, abundance, and infection rates of human schistosomiasis intermediate host snails (p-value < 0.05). Our findings provide useful information which can be adopted in designing and implementing snail control strategies as part of schistosomiasis control in the study area.

Aquatic invertebrate community structure and functions within a Ramsar wetland of a premier conservation area in South Africa

The Ramsar-accredited Makuleke Wetlands are located in the Makuleke Concession in the northern Pafuri region of the Kruger National Park in South Africa. The Pafuri area holds up to 75% of Kruger National Park’s total biodiversity, emphasising the Makuleke Wetlands’ international environmental importance. The Makuleke Wetlands are composed of the floodplains of the Luvuvhu and Limpopo rivers, with an estimated 31 wetlands present within the floodplains. Ten floodplain wetlands were assessed in the Makuleke region, eight of which are fed by the Limpopo River and the other two from the Luvuvhu River. Water and aquatic invertebrate communities were sampled at each site during surveys in April and September 2015 to provide baseline information on the aquatic biota of this Ramsar site. Multivariate data analytical techniques were used to assess the role of season and water quality in structuring the aquatic invertebrate communities of the wetlands. Macroinvertebrate functional feeding group ratios were also calculated as an indication of wetland ecosystem structure and function. Aquatic invertebrate diversity was some of the highest recorded for wetlands in South Africa, indicating the important role these habitats play in supporting high biodiversity in the Makuleke region. Worryingly, one of the most prolific invasive molluscan species, Tarebia granifera, was present in the wetlands and is a significant threat to native biodiversity of this conservation area. Community characteristics and ecosystem structure and function of the aquatic invertebrates further indicated that the Makuleke Wetland habitats were of good quality and provided a sufficient stable substrate for all aquatic invertebrates. Functionally, the system was characterised as reliant on heterotrophic inputs as autotrophic sources are limited. This is the first study of its kind for the region and lays the groundwork for future ecosystem studies on these important wetlands in the second-largest floodplain of South Africa.

Freshwater gastropod community in South Konawe District, Southeast Sulawesi, Indonesia

Abstract. Oetama D, Purnama MF. 2022. Freshwater gastropod community in South Konawe District, Southeast Sulawesi, Indonesia. Biodiversitas 23: 3364-3372. The freshwater gastropod population in South Konawe District, Southeast Sulawesi, Indonesia, consists of aquatic and terrestrial snail communities. This resource (gastropod) is an ecological and economic potential that needs to be maintained and utilized optimally and sustainably. This research was conducted in April-July 2021 and aimed to determine the ecological index of the inland gastropod community in the South Konawe District. The sampling location was determined qualitatively using the purposive sampling method and a simple random sampling technique (Quantitative based). Gastropod samples were collected manually (hand picking) with a paralon pipe (3.5 inches), Sieve (1 mm), and Gloves. The total gastropods obtained at 33 sampling locations in this district were 2635 individuals. The inland gastropods comprised 19 genera and 33 species spread over 9 families, namely Achantinidae, Ampullariidae, Ariophantidae, Lymnaeidae, Neritidae, Pachychilidae, Planorbidae, Thiaridae, and Viviparidae. The average abundance of gastropods reached 79.85 ind./m2 and the abundance of gastropod species ranged from 0.58-13.48 ind./m2. Overall, the analysis of gastropod ecology index showed a stable condition, where the diversity of gastropod species was categorized as high (H'= 3.03), moderate evenness (E= 0.87), and high species richness (R= 4.06). There were no dominant species (C= 0.08) and the gastropod distribution showed a clustered pattern (Ip= 0.02). These ecological index values indicated that the gastropod community in the inland waters of South Konawe District was in a stable condition. Although the gastropod community in the inland waters of the South Konawe District simultaneously has the same area as the invasive gastropod from the family Thiaridae, namely Melanoides tuberculata (O.F.Müller, 1774) and Tarebia granifera (Lamarck, 1816).

Diversity and distribution of benthic invertebrates dwelling rivers of the Kruger National Park, South Africa

Meiobenthos (or meiofauna) are microscopic invertebrates that inhabit biofilms and interstitial spaces in rivers. They are diverse and extremely abundant, and they perform essential ecological functions by linking microbial production to higher trophic levels (e.g. macrobenthic invertebrates and fishes). However, meiobenthic communities remain poorly studied in Africa. Here, we sampled meio- and macrobenthic invertebrate communities associated with biofilms and sediments across an upstream–downstream gradient along the Olifants, Sabie and Crocodile rivers flowing through the Kruger National Park (KNP). We expected to link differences in community structure to environmental gradients as those rivers show different degrees of anthropogenic stress as they enter the park. Both meio- and macrobenthic communities differed across rivers and also structured along an upstream–downstream gradient. The upstream sites, which were the closest to the park borders, consistently showed a lower diversity in all three rivers. There, the invasive snail Tarebia granifera strongly dominated (making up 73% – 87% of the macrobenthos), crowding hard substrates, while concomitantly the abundances of biofilm-dwelling meiobenthos like nematodes and rotifers were substantially reduced. Nevertheless, the diversity and evenness of communities then tended to increase as water flowed downstream through the park, suggesting a beneficial effect of protected river reaches on benthic invertebrate diversity. However, for the Crocodile River, which makes up the southern border of the park, this trend was less conspicuous, suggesting that this river may experience the greatest threats. More generally, benthic invertebrate communities were driven by the concentrations of phosphates, sulphates, ammonium and organic matter and by substrate characteristics.Conservation implications: Meiobenthic organisms are very abundant in KNP rivers and react to environmental gradients; thus, they should be more considered for bio-monitoring or conservation of comprehensive assemblages of animals. Interestingly, protected reaches tended to show a reduced dominance of the invasive T. granifera and a higher diversity of benthic invertebrates.

Trematode larval infections in snails collected from aquaculture ponds in Ha Noi and Yen Bai, Vietnam

The hot-spots of transmission of food-borne zoonotic trematodes in northern Vietnam have been known as the integrated fish-livestock (VAC- Garden, Fish pond, Poultry shed) ponds. A cross-sectional study was conducted in Ha Noi capital and Yen Bai province to investigate the trematode larval infections (cercariae) in freshwater snails in these areas. Snails were collected from 35 VAC ponds, including 25 grow-out and 10 nursery ponds. A total of 13,895 specimens of 12 snail species were examined for cercariae shedding. Six of 12 snail species including Melanoides tuberculata, Tarebia granifera, Radix auriculata, Gyraulus convexiusculus, Bithynia fuchsiana and Parafosarulus manchouricus, shed cercariae. Seven cercarial types were detected. The amount of snails and the prevalent infection in nursery ponds were 1.14 and 1.3 times higher than in grow-out ponds, respectively. Thus, VAC ponds in northern Vietnam are still the hot-spot for trematode larval infection.

Development of the regulation of hydrobiological monitoring in circulation cooling system of the Zaporizhzhia nuclear power plant

The article proposes a new approach to solving the problem of biofouling at the facilities of the circulating cooling system of the Zaporizhzhia Nuclear Power Plant (ZNPP) by regulating hydrobiological studies. In the course of the studies, 4 species of hydrobionts were found that formed massive fouling on water supply facilities: filamentous algae Oedogonium sp. and Ulotrix zonata with a total biomass of 123.6±18.44 g/m2, tropical molluscs Melanoides tuberculata and Tarebia granifera of the Thiaridae family with a biomass of 20.09 g/m2. The shells of dead mollusks drifted along the pipes of the circulation system with the flow of water and interfered with the operation of pumping stations. Also, the blue-green algae Microcystis aeruginosa, which dominated the phytoplankton of the cooling pond, belonged to the potential bio-hindrances. The hydrobiological regulation was developed with the aim of timely detection of hydrobionts capable of active reproduction and creation of biological obstacles. It provides for four types of monitoring: current (operational), extreme (control), deployed (research) and background (hydrobiological monitoring of the Kakhovka reservoir in the zone of influence of waste warm waters). For each type of monitoring, the subjects of control (a group of hydrobionts), control parameters (species composition, abundance, biomass) and frequency of control are determined. The regulation of hydrobiological monitoring makes it possible to minimize the consequences or prevent the occurrence of accidents and emergencies in the operation of the ZNPP cooling circulation systems associated with biological obstacles, and can be used as an example for solving similar problems at other power facilities. The article also contains practical recommendations for improving the ecological state of the cooling pond and preventing the massive development of dangerous aquatic organisms by introducing biomeliorator fish with a different food spectrum into the reservoir

Diversity report of freshwater gastropods in Buton Island, Indonesia

Abstract. Purnama MF, Sirza LOMJ, Sari SF, Salwiyah, Haslianti, Abdullah, Suwarjoyowirayatno, Findra MN, Nurhikma, Agriansyah A, Hidayat H, Syukur, Anwar K. 2022. Diversity report of freshwater gastropods in Buton Island, Indonesia. Biodiversitas 23: 1938-1949. This study was located in Buton Island consisted of 5 administrative districts/cities (Baubau City, Buton District, South Buton District, Muna District and North Buton District) and was conducted for 1 year (August 2019-August 2020). The output is to reveal the potential richness of the biodiversity of freshwater gastropods as a first step to optimize the utilization of freshwater gastropod resources in the Buton Islands. Determination of sampling location for gastropods was carried out by purposive sampling method and the selection of gastropod samples using simple random sampling method at a predetermined location based on the presence of gastropods. Gastropod samples (epifauna/infauna) were collected manually without special fishing gear with gloves, paralone pipes (3.5 inches), and filter (1 mm). The gastropods found in Buton Island consist of 18 genera and 40 species. Freshwater gastropods spread over 8 families, namely Cyclophoridae, Planorbidae, Lymnaeidae and Thiaridae. Among the species, there are several invasive alien species (IAS) such as Tarebia granifera, Melanoides tuberculata and Achatina fulica. These three species always dominate the habitat space where they are found. Most gastropod communities in 5 districts/cities live in fast-flowing rivers with rock, gravel and sand substrates. Only a few of them are found in artificial inland waters such as rice fields, embankments, dams and drainage. This study became a first step to optimize the utilization of gastropod resources and sustainable management, especially related to the conservation of native species from the threat of IAS.

COMMUNITY STRUCTURE OF FRESHWATER GASTROPODS IN NORTH KOLAKA REGENCY SOUTHEAST SULAWESI

This research was conducted in January-March 2021 in North Kolaka Regency. The purpose of this study was to determine the structure of the freshwater gastropod community in North Kolaka Regency. This research applies a combination method (qualitative-quantitative) in determining the sampling location and sampling process. Determination of the sampling location using purposive sampling method based on the presence of gastropod communities and quantitative sampling using simple random sampling technique. Gastropod samples were collected manually using a metal hand scoop and gloves. The total gastropod sample obtained at 17 sampling points was 4250 individuals. The gastropod community structure in North Kolaka Regency consists of 19 genera and 33 species spread over 9 families, namely Achantinidae, Ampullariidae, Ariophantidae, Lymnaeidae, Neritidae, Pachychilidae, Planorbidae, Thiaridae and Viviparidae. The results of the analysis of the gastropod community structure showed a relatively stable condition, where the average abundance of gastropods reached 91.94 ind./m2 and the abundance of gastropod species ranged from 0.29-16 ind./m2. Gastropod species diversity was categorized as moderate with a maximum value (H' = 2.96) or close to H'&gt;3 (high category), moderate evenness (E = 0.85), high species richness (R = 4.35), dominance which showed that there was no dominant species (C = 0.08) and the distribution of gastropods showed a clustered pattern (Ip = 0.01). The freshwater types in North Kolaka Regency are generally rocky rivers so that the gastropod community is dominated by the Neritidae and Thiaridae families, especially the Tarebia granifera, Melanoides tuberculata and Clithon corona.

Distribution, drivers and population structure of the invasive alien snail Tarebia granifera in the Luvuvhu system, South Africa

AbstractInvasive alien species continue to spread and proliferate in waterways worldwide, but environmental drivers of invasion dynamics lack assessment. Knowledge gaps are pervasive in the Global South, where the frequent heavy human‐modification of rivers provides high opportunity for invasion. In southern Africa, the spatio‐temporal ecology of a widespread and high‐impact invasive alien snail, Tarebia granifera, and its management status is understudied. Here, an ecological assessment was conducted at seven sites around Nandoni Reservoir on the Luvuvhu River in South Africa. The distribution and densities of T. granifera were mapped and the potential drivers of population structure were explored. T. granifera was widespread at sites impacted to varying extents due to anthropogenic activity, with densities exceeding 500 individuals per square meter at the most impacted areas. T. granifera predominantly preferred shallow and sandy environments, being significantly associated with sediment (i.e., chlorophyll‐a, Mn, SOC, SOM) and water (i.e., pH, conductivity, TDS) variables. T. granifera seemed to exhibit two recruitment peaks in November and March, identified via size‐based stock assessment. Sediment parameters (i.e., sediment organic matter, sediment organic carbon, manganese) and water chemistry (i.e., pH, total dissolved solids, conductivity) were found to be important in structuring T. granifera populations, with overall snail densities highest during the summer season. We provide important autecological information and insights on the distribution and extent of the spread of T. granifera. This may help in the development of invasive alien snail management action plans within the region, as well as modelling efforts to predict invasion patterns elsewhere based on environmental characteristics.

Complete mitochondrial genome of the freshwater snail Tarebia granifera (Lamarck, 1816) (Gastropoda: Cerithioidea: Thiaridae)

The freshwater gastropod Tarebia granifera (Lamarck, 1816) is found in Taiwan, Hainan, and Guangdong provinces in China, and is one of the main intermediate hosts of trematodes that infect humans. The taxonomic positions of some cerithioidean families are still unclear, and whole mitochondrial genome studies are scarce in the Thiaridae. In this study, we describe the complete mitogenome of Tarebia granifera (Lamarck, 1816). The mitogenome is 15,555 bp in length, with a total of 37 genes, including 13 protein-coding genes, 2 rRNA genes, and 22 tRNA genes. It is consistent with the essential features of previously studied mitochondrial genomes of species belonging to the superfamily Cerithioidea. Our study demonstrates the usefulness of mitogenomic data for resolving phylogenetic relationships of families within Cerithioidea and may also contribute to the prevention and control of the parasitic diseases caused by trematodes, which use T. granifera as an intermediate host.

Informing spread predictions of two alien snails using movement traits

Invasive alien species are a growing global problem, and aquatic ecosystems have been regarded as particularly vulnerable. Biological invasions can alter ecosystem functioning, threaten native biodiversity and burden the global economy. Understanding alien species ability to disperse via locomotion following arrival to new environments is critical for prediction of spread rates. Here, we quantified in-field densities and compared movement traits between two widespread invasive alien snails, Tarebia granifera and Physa acuta. We measured the: (i) net distance and velocity to determine dispersal potential; and (ii) turning angles (both absolute and relative) and straightness index as proxies for exploratory behaviour. Tarebia granifera exhibited a significantly greater velocity and covered a significantly larger net distance (i.e., greater spread rate) than Physa acuta. In-field densities were marked for both species (T. granifera: mean 351 individuals m−2; P. acuta: mean 235 individuals m−2), but differed spatially. The exploratory behavior (i.e., mean or absolute turning angles and straightness index) did not differ significantly between the two alien species; both species showed a slight tendency to turn counterclockwise. The present study suggests a more rapid capacity to self-disperse in T. granifera than P. acuta, which could facilitate rapid spread within and between aquatic systems. Thus, this current study highlights the often-overlooked role of animal behaviour in promoting invasion; this autecological information can help inform predictive models for the spread of alien snails within freshwater ecosystems.