Neither variation loss, nor change in selfing rate is associated with the worldwide invasion of Physa acuta from its native North America

Cannabis sativa: A look at protozoa, helminths, insect vectors, and pests

Active principles extracted from plants, such as essential oils, have been commonly described in the literature as therapeutic targets for numerous pathological conditions. Cannabis sativa, which has an ancient and peculiar history, has been used for various purposes, from recreational to compounds of pharmacotherapeutic and industrial importance, such as pesticides based on this plant. It is a plant that contains approximately 500 described cannabinoid compounds and is the target of in vitro and in vivo studies at different locations. This review clarifies the role of cannabinoid compounds in parasitic infections caused by helminths and protozoa. In addition, this study briefly presented the use of C. sativa constituents in the formulation of pesticides for vector control, as the latter topic is justified by the economic burden faced by several regions where vector-borne diseases are a troubling reality. Studies involving cannabis compounds with pesticidal potential should be encouraged, especially those that evaluate their effectiveness against the different life cycles of insects, seeking to interrupt vector proliferation after egg laying. Actions aimed at the management and cultivation of plant species with ecologically correct pharmacotherapeutic and pesticide potentials are becoming urgent.

Current Status and Conservation of Springs in Taiwan: Water Quality Assessment and Species Diversity of Aquatic Animals

Even though spring ecosystems are ecologically unique and socio-culturally important worldwide, they hardly attract research attention. The aims of this study were to evaluate the environmental status of water quality, and to inventory the species diversity of aquatic animals in 65 springs in Taiwan from 2012 to 2017, of which seven springs were unable to be sampled due the fact that they were dried or sealed up. The environmental status of 58 springs with complete water quality data was assessed by the River Pollution Index (RPI). Based on the RPI, the water quality of these 58 sampled springs was mainly non-/mildly polluted (26 springs, 44.8%) and lightly polluted (23 spring, 39.6%), and nine (15.5%) springs were moderately polluted. However, when applied to springs, the RPI may intensify the pollution rankings because dissolved oxygen is an assessing factor, and hypoxia may naturally be observed in the springs. To avoid this concern, we suggest choosing the concentration of coliform instead of dissolved oxygen content in the RPI when it is applied to springs. During the 6 years of the study period, we collected 48 fish species in 44 springs, 24 gastropoda and bivalve species in 46 springs, 16 shrimp species in 34 springs, and 14 crab species in 18 springs. Within the species collected, 31 fish, 20 gastropoda and bivalves, 12 shrimps, and 14 crabs are native species of Taiwan. They totaled 27.2 to 35% of the known aquatic native species of the island. Thus, springs in Taiwan may be considered to be a conservation hotspot of aquatic animals. Other than native species, exotic aquatic animals also represent threats, as seventeen fishes (35.4%), four gastropoda and bivalves (16.6%), and two shrimps (12.5%) were found in the springs of Taiwan. The springs in Taiwan show diverse and vital ecosystem services, such as delivering social, cultural, and economic value, conserving native and endangered freshwater animals, developing new academic theories, and supplying habitat refugees from climate change. Unfortunately, springs in Taiwan currently are also threatened by multiple anthropogenic disturbances, such as the overconsumption of groundwater by land development and urbanization, deterioration of water quality by agricultural, domestic, and industrial pollution, and inappropriate tourism and management tactics. To restore and sustain the springs in Taiwan, effective strategies and practical measures are urgently required to minimize human-caused threats and revitalize social awareness of springs.

<i>PHYSELLA ACUTA </i>(DRAPARNAUD, 1805) (MOLLUSCA: GASTROPODA: PHYSIDAE) IN THE ĐANHIM RIVER BASIN (LÂM ĐỒNG PROVINCE, VIETNAM): GENETIC AND MORPHOLOGICAL IDENTIFICATION

Invasive freshwater molluscs of the genus Physella (Gastropoda: Physidae) were discovered in the basin of the Dong Nai River, Vietnam for the first time. Based on the analysis of morphological features and the nucleotide sequence of the fragment of the COI mitochondrial gene, these molluscs were identified as belonging to the species Physella acuta (Draparnaud, 1805). The paper summarizes the available information on the distribution of this species in the waterbodies of Vietnam, provides the morphological characteristics of the studied individuals, and compares them with other populations of the species found in tropic and subtropic regions. It is shown that, despite the more than twenty-year history of registration of Physella acuta in Vietnam, the species remains relatively rare in the country's waterbodies. The presence in the studied sample of individuals of different size groups suggests that, in the basin of the Dong Nai River, self-reproducing population of Physella acuta has been established.

Micro-endemic species of snails and amphipods show population genetic structure across very small geographic ranges

Understanding variation in population genetic structure, even across small distances and for species with extremely limited ranges, is critical for conservation planning and the development of effective management strategies for imperiled species. Organisms that occupy the same geographic extent can maintain different population structures, ranging from highly diverged to panmictic. Such differences can result from differences in biological characteristics such as dispersal ability or demographic history. We used microsatellite loci to evaluate population genetic structure and variation of four desert spring invertebrates having high to low dispersal ability: the lung snail Physa acuta, two species of gilled snails (Juturnia kosteri and Pyrgulopsis roswellensis; family Hydrobiidae) and the amphipod Gammarus desperatus. The study location represents entire species ranges for the micro-endemic hydrobiids and G. desperatus, while P. acuta is ubiquitous throughout much of North America. We found little evidence of significant population genetic structure for P. acuta and J. kosteri, but much more for P. roswellensis and G. desperatus. Our results demonstrate differences in habitat preference and/or dispersal ability between the species. This information provides insight into how gene flow shapes varying population genetic structure between species across small spatial scales (<100 km2). Most importantly, our results suggest that conservation agencies should not consider these micro-endemic species to be composed of single populations, but rather, that management plans for such species should account for population genetic variation across the species' ranges.

Molecular Phylogenetics of Physa acuta (Pulmonata: Basommatophora): an Invasive species in Central Punjab Pakistan

Physids belong to Class Gastropoda; belong to Phylum Mollusca and being bioindicators, intermediate hosts of parasites and pests hold a key position in the ecosystem. There are three species of Genus Physa i.e. P. fontinalis, Physa acuta and P. gyrina water bodies of Central Punjab and were characterized on the basis of molecular markers High level of genetic diversity was revealed by polymorphic RAPD, however SSR markers were not amplified. The multivariate analysis revealed polymorphism ranging from 9.09 percent to 50 percent among the three Physid species. Total number of 79 loci were observed for the three species under study and 24 loci were observed to be polymorphic. These RAPD fragment(s) can be developed into co dominant markers (SCAR) by cloning and can be further sequenced for the development of the Physa species specific markers to identify the introduced and native species in Pakistan.

Cercarial trematodes in freshwater snails from Bangkok, Thailand: prevalence, morphological and molecular studies and human parasite perspective

We investigated the prevalence, morphological characters and molecular classifications of trematode cercariae in freshwater snails randomly collected from 59 sampling localities in Bangkok from May 2018 to March 2019. We used a crushing technique to observe the cercarial stage inside each snail body and amplified the internal transcribed spacer 2 regions of cercarial DNA using polymerase chain reaction methodology. The associated phylogenetic tree was reconstructed using Bayesian inference analyses. A total of 517 of 15 621 examined snails were infected with trematode cercariae, and the infected snails were classified into 11 species of seven families with a 3.31% overall prevalence of the infection. The Bithynia siamensis siamensis snail displayed the highest prevalence of infection (16.16%), whereas the Physella acuta snail exhibited the lowest prevalence (0.08%) of infection. Eight morphological types of cercariae were observed. The highest prevalence of infection was observed in mutabile cercaria (1.86%). Based on molecular investigations, the phylogram revealed eight cercaria types assigned to at least nine digenean trematode families, of which five belong to groups of human intestinal flukes. Although, with the exception of schistosome cercaria, trematode cercariae are not known to directly damage humans, understanding the general biology of trematode cercariae (including diversity, distribution, infection rates and host range) is important and necessary for the prevention and control of parasitic transmission that impacts aquatic cultivations, livestock farming and human health.

The roles of spatial and environmental variables in the appearance of a globally invasive Physa acuta in water bodies created due to human activity

Anthropogenic pollution of freshwater environments is a subject of serious international concern since they affect freshwater and land environments. The disturbances in the functioning of ecosystems that result from various forms of human activity permit them to be settled by alien species. Research was carried out in 84 anthropogenic water bodies using quantitative methods for sampling, laboratory analysis and multivariate statistical methods. The appearance of P. acuta in these water bodies seems to depend on their water chemistry. Physa acuta primarily occurred in waters with a very low content of ammonia, medium salinity and hardness, and in waters with a higher pH. The density of P. acuta decreased along with its dominance index, which indicates that in water bodies in which its density was low, the other snail species achieved higher densities. This suggest competitive displacement of native species at high densities of P. acuta. Cluster analysis showed that water bodies in which P. acuta was abundant were similar in the snail community composition in contrast to water bodies in which it wasn't present. Research on colonisation of freshwater habitats by alien species in freshwater habitats is important because in the future, the number of alien species is likely to increase as a result of climate change and their ability to overcome the existing barriers as well as with the progressive colonisation of new areas outside of their native range.

Morphological and molecular identification of the invasive freshwater snail Physa acuta (Gastropoda: Physidae) into Llanquihue Lake, Chilean Patagonia

The sewage snail Physa acuta, native to North America, is an effective invasive species around the world. In Chile, it was first reported in 2014 in the north central area of the country. So far, the species has not been recorded in southern Chile. Sampling performed in 2015 in three localities from Llanquihue Lake, Chilean Patagonia, only provided native freshwater snails. However, new collections performed in February 2018 in the same three sites were successful for physid specimens suggesting a biological invasion entailing a large southward range expansion of these snails. Here we performed morphological, microstructural and phylogenetic analyses to investigate whether the new samples belong to Physa acuta. The shell morphology, male copulatory complex and radula microstructure of the new material agree with those of the sewage snail. The molecular phylogenetic analyses using the cytochrome c oxidase subunit 1 (COI) gene confirmed morphological identification. We suggest to take prompt measures to prevent the expansion of Physa acuta in Llanquihue Lake or nearby aquatic ecosystems.

Phylogeography and genetics of the globally invasive snail Physa acuta Draparnaud 1805, and its potential to serve as an intermediate host to larval digenetic trematodes

BACKGROUND

Physa acuta is a globally invasive freshwater snail native to North America. Prior studies have led to conflicting views of how P. acuta populations are connected and genetic diversity is partitioned globally. This study aims to characterize phylogeographic and population genetic structure within the native range of P. acuta, elucidate its invasion history and assess global patterns of genetic diversity. Further, using meta-analytic methods, we test the 'Enemy-Release hypothesis' within the P. acuta - digenetic trematode system. The 'Enemy-Release hypothesis' refers to the loss of native parasites following establishment of their host within an invasive range. Population genetic data is combined with surveys of trematode infections to map range-wide trematode species richness associated with P. acuta, and to identify relevant host-population parameters important in modeling host-parasite invasion.

RESULTS

Phylogenetic analyses using mtDNA uncovered two major clades (A & B). Clade A occurs globally while clade B was only recovered from the Western USA. All invasive populations sampled grouped within Clade A, where multiple independent source populations were identified from across North America. Significant population genetic structure was found within the native range of P. acuta, with some evidence for contemporary geographic barriers between western and eastern populations. Mito-nuclear discordance was found suggesting historical isolation with secondary contact between the two mitochondrial clades. Trematode species richness was found to differ significantly between native and invasive populations, in concordance with the 'Enemy-Release hypothesis'. Further, our data suggests a positive relationship between nucleotide diversity of invasive populations and trematode prevalence and richness.

CONCLUSIONS

This study includes a wider geographic sampling of P. acuta within its native range that provides insight into phylogeographic and population genetic structure, range-wide genetic diversity and estimation of the invasion history. Meta-analysis of P. acuta - trematode surveys globally is consistent with the 'Enemy-Release hypothesis'. Additionally, results from this study suggest that host demographic parameters, namely genetic diversity as a proxy for population size, may play an essential role in how parasite communities assemble within invasive host populations. This knowledge can be used to begin to construct a framework to model host-parasite invasion dynamics over time.

Bioinvasion Triggers Rapid Evolution of Life Histories in Freshwater Snails

Biological invasions offer interesting situations for observing how novel interactions between closely related, formerly allopatric species may trigger phenotypic evolution in situ. Assuming that successful invaders are usually filtered to be competitively dominant, invasive and native species may follow different trajectories. Natives may evolve traits that minimize the negative impact of competition, while trait shifts in invasives should mostly reflect expansion dynamics, through selection for colonization ability and transiently enhanced mutation load at the colonization front. These ideas were tested through a large-scale common-garden experiment measuring life-history traits in two closely related snail species, one invasive and one native, co-occurring in a network of freshwater ponds in Guadeloupe. We looked for evidence of recent evolution by comparing uninvaded or recently invaded sites with long-invaded ones. The native species adopted a life history favoring rapid population growth (i.e., increased fecundity, earlier reproduction, and increased juvenile survival) that may increase its prospects of coexistence with the more competitive invader. We discuss why these effects are more likely to result from genetic change than from maternal effects. The invader exhibited slightly decreased overall performances in recently colonized sites, consistent with a moderate expansion load resulting from local founder effects. Our study highlights a rare example of rapid life-history evolution following invasion.

A Complex System of Glacial Sub-Refugia Drives Endemic Freshwater Biodiversity on the Tibetan Plateau

Although only relatively few freshwater invertebrate families are reported from the Tibetan Plateau, the degree of endemism may be high. Many endemic lineages occur within permafrost areas, raising questions about the existence of isolated intra-plateau glacial refugia. Moreover, if such refugia existed, it might be instructive to learn whether they were associated with lakes or with more dynamic ecosystems such as ponds, wetlands, or springs. To study these hypotheses, we used pulmonate snails of the plateau-wide distributed genus Radix as model group and the Lake Donggi Cona drainage system, located in the north-eastern part of the plateau, as model site. First, we performed plateau-wide phylogenetic analyses using mtDNA data to assess the overall relationships of Radix populations inhabiting the Lake Donggi Cona system for revealing refugial lineages. We then conducted regional phylogeographical analyses applying a combination of mtDNA and nuclear AFLP markers to infer the local structure and demographic history of the most abundant endemic Radix clade for identifying location and type of (sub-)refugia within the drainage system. Our phylogenetic analysis showed a high diversity of Radix lineages in the Lake Donggi Cona system. Subsequent phylogeographical analyses of the most abundant endemic clade indicated a habitat-related clustering of genotypes and several Late Pleistocene spatial/demographic expansion events. The most parsimonious explanation for these patterns would be a scenario of an intra-plateau glacial refugium in the Lake Donggi Cona drainage system, which might have consisted of isolated sub-refugia. Though the underlying processes remain unknown, an initial separation of lake and watershed populations could have been triggered by lake-level fluctuations before and during the Last Glacial Maximum. This study inferred the first intra-plateau refugium for freshwater animals on the Tibetan Plateau. It thus sheds new light on the evolutionary history of its endemic taxa and provides important insights into the complex refugial history of a high-altitude ecosystem.

Schistosomes with wings: how host phylogeny and ecology shape the global distribution of Trichobilharzia querquedulae (Schistosomatidae)

Migratory waterfowl play an important role in the maintenance and spread of zoonotic diseases worldwide. An example is cercarial dermatitis, caused when larval stages of schistosomes that normally develop in birds penetrate human skin. Members of the genus Trichobilharzia (Schistosomatidae), transmitted mainly by ducks, are considered to be major etiological agents of cercarial dermatitis globally. To better understand the diversity and distribution of Trichobilharzia spp., we surveyed ducks from the United States, eastern Canada, Argentina, South Africa and New Zealand. To aid in species identification of the Trichobilharzia worms recovered, regions of the Cox1, ND4 and ITS1 were sequenced. Furthermore, we provide molecular phylogenetic evidence for the cosmopolitan distribution and trans-hemispheric gene flow for one species, Trichobilharzia querquedulae, previously thought to be restricted to North America. These new samples from endemic non-migratory duck species indicate that T. querquedulae transmission occurs within each of the regions we sampled and that it is specific to the blue-winged+silver teal duck clade. Prevalence within this host group is >95% across the known range of T. querquedulae, indicating that transmission is common. Genetic divergence is evenly distributed among continents, and no phylogenetic structure associated with geography was observed. The results provide strong support for the global distribution and transmission of T. querquedulae and represent, to our knowledge, the first report of a cosmopolitan schistosome confirmed by genetic data. These data are the first known to support trans-hemispheric genetic exchange in a species responsible for causing cercarial dermatitis, indicating that the epidemiology of this group of poorly known zoonotic parasites is more complex than previously expected.

Molecular Evolution of Freshwater Snails with Contrasting Mating Systems

Because mating systems affect population genetics and ecology, they are expected to impact the molecular evolution of species. Self-fertilizing species experience reduced effective population size, recombination rates, and heterozygosity, which in turn should decrease the efficacy of natural selection, both adaptive and purifying, and the strength of meiotic drive processes such as GC-biased gene conversion. The empirical evidence is only partly congruent with these predictions, depending on the analyzed species, some, but not all, of the expected effects have been observed. One possible reason is that self-fertilization is an evolutionary dead-end, so that most current selfers recently evolved self-fertilization, and their genome has not yet been strongly impacted by selfing. Here, we investigate the molecular evolution of two groups of freshwater snails in which mating systems have likely been stable for several millions of years. Analyzing coding sequence polymorphism, divergence, and expression levels, we report a strongly reduced genetic diversity, decreased efficacy of purifying selection, slower rate of adaptive evolution, and weakened codon usage bias/GC-biased gene conversion in the selfer Galba compared with the outcrosser Physa, in full agreement with theoretical expectations. Our results demonstrate that self-fertilization, when effective in the long run, is a major driver of population genomic and molecular evolutionary processes. Despite the genomic effects of selfing, Galba truncatula seems to escape the demographic consequences of the genetic load. We suggest that the particular ecology of the species may buffer the negative consequences of selfing, shedding new light on the dead-end hypothesis.