Native Amphipod Research Articles

Heat Tolerance of Gammarus fossarum (Crustacea, Amphipoda) Is Influenced by the Level of Stress Associated with Reproduction and the Water Quality of Their Habitat

To elucidate how rising temperatures influence native amphipods, and how the expansion of wastewater treatment plants (WWTPs) with a fourth purification stage can alter temperature-related effects, studies were conducted in anthropogenically influenced rivers in Southwest Germany. Gammarids were sampled up- and downstream of two WWTPs, and exposed to elevated temperatures in the laboratory. Gammarids separated from precopula pairs were more sensitive to exposure-related stress and to a temperature increase than animals that were not in the reproductive phase. Furthermore, females were significantly more sensitive than males. Adult gammarids sampled individually at the WWTP with three purification stages showed a similar tolerance to elevated temperature at the up- and downstream site. In contrast, mortality following heat stress was substantially lower in animals sampled downstream of the WWTP with four treatment stages than in those sampled at the upstream site. We assume that the increased sensitivity of artificially separated precopula pairings reflect the situation under high hydraulic stress after heavy rainfall. Our results further illustrate the importance of WWTP upgrades in the context of climate change: gammarids sampled downstream the upgraded fourth-stage WWTP were likely exposed to lower levels of micropollutants, and thus may have allocated energy from detoxification to heat stress responses.

Habitat-based variation in the trophic ecology of the world’s highest-altitude self-sustaining population of invasive rainbow trout

Rainbow trout (Oncorhynchus mykiss) have been widely introduced outside of their natural range and are one of the World’s most invasive species. Illegally introduced into the isolated, high-altitude (4520 m) Chungará catchment of northern Chile, rainbow trout have now been present in the system for ∼30 years and to our knowledge are the World’s highest known self-sustaining population. However, nothing is known about the status and impacts of these trout in the system. We analysed stomach contents and stable isotopes (δ13C, δ15N, δ34S) from liver and muscle to study the trophic ecology of rainbow trout from lake, river mouth and riverine habitats in the Chungará catchment to understand their basic ecology and to characterise their potential trophic interactions with native taxa. Both stomach contents and stable isotope values showed spatial differences in diet and habitat use, but also revealed that diet varied temporally within habitats. The trophic position of rainbow trout was similar in the three habitats examined and was constant over time, apart from the riverine population. Predation by rainbow trout had different potential effects across pelagic, benthic, and riverine habitats in the Chungará catchment, through the consumption of zooplankton, native amphipods, aquatic insects, and the endemic cypriniodontid fish Orestias chungarensis.

Whole-sediment toxicity bioassays with Hyalella curvispina as a valuable bioanalytical tool for assessing pesticide risks in watercourses with different types of agro-productive activities

The current Argentine agricultural production model is dependent on agrochemicals such as fertilizers and pesticides. Extensive agriculture and horticulture are the two major productive activities that use copious amounts of pesticides. Extensive agriculture is characterized by areas of 50 to 100 ha of a single crop, while peri-urban horticulture is characterized by intense land use, with farms ranging from 1 to 3 ha cultivated with a variety of vegetables. Despite the relevance of pesticides, data on their effects on the biota associated with nearby watercourses are scarce. Given this paucity of knowledge, the objective of the present work was to assess the relative impact of extensive agriculture and horticulture on sediment quality in representative watercourses by conducting whole-sediment toxicity bioassays with the native amphipod Hyalella curvispina. The lower Gualeguay Basin, in the Province of Entre Ríos, was selected as a representative watercourse impacted by extensive agriculture, and the Carnaval Creek, on the periphery of La Plata, Province of Buenos Aires, was selected as a horticulture-impacted watercourse. Growth inhibition (sublethal effect) was observed in both systems, whereas mortality (lethal effect) was largely observed in horticulture. The observed effects were integrated with pesticide concentrations in the same sediments and correlated by multivariate analysis, revealing that toxicity was mainly due to insecticides, particularly λ-cyhalothrin. Therefore, horticultural practices and their associated pesticide use could potentially endanger the benthic fauna of nearby watercourses.

Differential effects of microplastic exposure on leaf shredding rates of invasive and native amphipod crustaceans

There is growing concern surrounding the pervasive impacts of microplastic pollution, but despite increasing interest in this area there remains limited understanding of its disruption to biological communities and the ecosystem services they provide. One such service is the breakdown of leaf litter in freshwaters by invertebrate shredders, such as Gammarus spp., that directly and indirectly provides resources for many other species. This study investigates the effect of microplastic exposure on leaf consumption by two Gammarus species in Ireland, the native Gammarus duebeni celticus, and the invasive Gammarus pulex. Individuals were exposed to 40–48 μm polyethylene particles for 24 h at a range of concentrations (20–200,000 MP/L), with the amount of leaf consumption in that time frame recorded. Microplastics did not affect the feeding rate of either species at environmentally relevant concentrations, indicating that ecosystem services currently provided by our study species are sustainable. However, at higher microplastic concentrations the feeding rate of G. d. celticus was significantly reduced, whereas G. pulex remained unaffected, drawing attention to species-specific and native-invader differences in microplastic impacts. The results of our study further contribute to the observed pattern that invasive species, including various amphipod species, often display a higher tolerance to environmental stressors compared to their native counterparts. This research highlights the need for mitigation of ongoing and increasing microplastic pollution that could differentially influence key ecosystem services and functions.

Comparative mitogenomics of native European and alien Ponto-Caspian amphipods

European inland surface waters are home to a rich diversity of native amphipod crustaceans, many of which face threats from invasive Ponto-Caspian counterparts. In this study, we analyse mitochondrial genomes to deduce phylogenetic relationships and compare gene order and nucleotide composition between representative native European and invasive Ponto-Caspian taxa across five families, ten genera and 20 species (with 13 newly sequenced herein). We observe various gene rearrangement patterns in the phylogenetically diverse native species pool.Pallaseopsis quadrispinosaandSynurella ambulansexhibit notable deviations from the typical organisation, featuring extensive translocations of tRNAs and the nad1 gene, as well as a tRNA-F polarity switch in the latter. The monophyletic invasive Ponto-Caspian gammarids display a conserved gene order, primarily differing from native species by a tRNA-E and tRNA-R translocation, which reinforces previous findings. However,Chaetogammarus warpachowskyishows extensive rearrangement with translocations of six tRNAs. The invasive corophiid,Chelicorophium curvispinum, maintains a highly conserved gene order despite its distant phylogenetic position. We also discover that native species have a significantly higher GC and lower AT content compared to invasive species. The mitogenomic differences observed between native and invasive amphipods warrant further investigation and could provide insights into the mechanisms underlying invasion success.

New species, new story: The impact of invasive non‐host predators on host‐trematode interactions

Abstract Predation is considered one of the key drivers shaping the relationships between animals. There is increasing evidence that non‐host aquatic taxa use free‐living parasite stages as prey, including motile cercariae of digenean trematodes. However, species‐specific predator differences in cercarial consumption are poorly understood, especially when invasive consumers are involved. We used experimental approaches to investigate the possible predator‐induced reduction in trematode‐host encounters in freshwater benthic communities. Four gammarid species, two native European (Gammarus jazdzewskii and G. pulex) and two invasive Ponto‐Caspian (Dikerogammarus villosus and Pontogammarus robustoides), were selected as predators of echinostomatid cercariae (Echinoparyphium aconiatum). We hypothesised that (i) all predators will prey on cercariae, but the amount of prey consumed will vary, the invaders will be more voracious than native species, and (ii) the effect of predator‐induced dilution of cercariae will depend on the environmental condition, i.e., the presence of the natural target host (the planorbid snail Planorbarius corneus) and alternative food resource; the exposure of predators to these two basic environmental factors will reduce their consumption rates of cercariae. The extent of the dilution effect caused by gammarids was highly predator species‐dependent and also varied depending on experimental conditions. Overall, all gammarids preyed on cercariae and reduced infection levels in the target snail host, but the invaders were more efficient than the native species. Furthermore, decreased consumption rates of cercarial prey were observed in the presence of both the target snail hosts and alternative food resources, except for invasive P. robustoides consuming more cercariae when a snail host was present. The observed differences among predators in the consumption of cercariae may be a result of complex interaction traits of parasites, predators and target hosts, such as different predatory behaviour of invasive and native amphipods, change in parasite behaviour in response to the presence/chemical signals of the target host and a predator‐induced “ecology of fear” interfering with the dilution effect of parasites. We provided evidence that gammarids can cause a significant reduction in parasite‐host encounters. The high consumption rates, especially in the presence of easily available alternative food resources, emphasise the importance of free‐living cercariae as an energy resource in aquatic food webs. The observed predator differences in the consumption of cercariae are further evidence of the higher competitive ability of invasive species. Simultaneously, our results indicate that the appearance of new predators in the environment may interfere with established host‐parasite interactions.

Biological Invasions Affect Resource Processing in Aquatic Ecosystems: The Invasive Amphipod Dikerogammarus villosus Impacts Detritus Processing through High Abundance Rather than Differential Response to Temperature.

Anthropogenic stressors such as climate warming and invasive species and natural stressors such as parasites exert pressures that can interact to impact the function of ecosystems. This study investigated how these stressors interact to impact the vital ecosystem process of shredding by keystone species in temperate freshwater ecosystems. We compared metabolic rates and rates of shredding at a range of temperatures up to extreme levels, from 5 °C to 30 °C, between invasive and native amphipods that were unparasitised or parasitised by a common acanthocephalan, Echinorhynchus truttae. Shredding results were compared using the relative impact potential (RIP) metric to investigate how they impacted the scale with a numerical response. Although per capita shredding was higher for the native amphipod at all temperatures, the higher abundance of the invader led to higher relative impact scores; hence, the replacement of the native by the invasive amphipod is predicted to drive an increase in shredding. This could be interpreted as a positive effect on the ecosystem function, leading to a faster accumulation of amphipod biomass and a greater rate of fine particulate organic matter (FPOM) provisioning for the ecosystem. However, the high density of invaders compared with natives may lead to the exhaustion of the resource in sites with relatively low leaf detritus levels.

Survival and Accumulation of Microcystins in a Native Amphipod Shredder, Gammarus Pulex under Environmentally Relevant Cyanotoxin Exposure

Microcystin release in freshwaters is a major public health and ecological threat, affecting survival and trophic interactions across food web components. Although bioaccumulation has been suggested to represent an important pathway for microcystin uptake and trophic transfer across different food web compartments, it is rarely known how microcystin exposure may affect survival and accumulation among lower trophic levels under environmentally realistic scenario. Therefore, in this study, survival and microcystin accumulations in the UK native amphipod species, Gammarus pulex were monitored during a 96-hour static acute toxicity experiment. Animals were exposed to a range of environmentally relevant microcystin concentrations (0.01–10μg/L) across two treatment types, purified MC-LR and crude extract of microcystin-producing Microcystis aeruginosa. Survival of G. pulex individuals across the two treatments showed no evidence of significant difference from the control. Microcystin concentrations observed in G. pulex exposed to the purified MC-LR and crude extract ranged from (12.8 – 27.5) ng/g of MC-LR and (5.6-12.8) ng/g of MC-LR respectively. Microcystin concentrations measured in animals showed strong positive correlations with toxin concentrations in the experimental media across the two treatments, suggesting G. pulex can bioaccumulate microcystins, therefore may represent a potential vector for microcystin exposure to higher food web consumers. These results highlight the fact that exposure of benthic food web components to environmental microcystin concentrations may constitute an important route of toxin transfer within freshwater food webs.

How much waste can the amphipod Gammarus insensibilis remove from aquaculture effluents? A first step toward IMTA

In recent years marine amphipods have been highlighted as an alternative live feed resource for Integrated Multi-Trophic Aquaculture (IMTA). Gammarus insensibilis Stock, 1966 is a native amphipod from the Mediterranean Sea and the north Atlantic Ocean and it is highly abundant in southern Spain marsh ponds. Its high potential for being intensively reared has been demonstrated in previous studies, as this species can feed on detritus and presents an interesting nutritional profile. In the present work, G. insensibilis specimens were maintained in closed batches at three different densities (100, 500 and 1000 ind L−1) and fed on dry or wet detritus (uneaten food and faeces from a fish RAS effluent) in order to assess for the first time the amount of wastes that they were able to remove. In parallel, a trial was performed to study the effect of dissolved inorganic nitrogen compounds (highly abundant in aquaculture effluents) on their survival, and the median lethal concentrations (LC50) in 96 h were calculated. Amphipods in all experiments and conditions showed promising survival rates higher than 80%. No advantages were observed when gammarids were maintained at high densities due to the significantly higher ammonium concentrations in these treatments, having an effect on intake but allowing sub-lethal conditions. Indeed, Gammarus insensibilis showed the highest tolerance for nitrate (1308 mg N-NO3− L−1), followed by nitrite (39.77 mg N-NO2− L−1) and ammonium (33.23 mg N-NH4+ L−1). Individuals at low densities removed significantly higher amounts of detritus, between 154.98 and 169.78 mg (dry weight detritus) per g (wet weight amphipods) and day. No differences were observed between removal rate of dry or wet detritus. Thus, authors recommend the use of wet detritus for a better handling and up-scaled trials in open or RAS systems equipped with a biofilter in order to avoid high ammonium concentrations impacting on intake.

Interactive effects of resource quality and temperature drive differences in detritivory among native and invasive freshwater amphipods

AbstractInvasive non‐native species and climate change are two of the greatest pressures facing freshwater communities; however, how they interact to impact ecosystem function remains poorly understood despite the potential for impacts on key functional behaviours, such as detritivory, which could have wide‐reaching impacts.We quantified the rates of detrital processing and survival of one U.K. native (Gammarus pulex) and two invasive non‐native (Dikerogammarus villosus and Dikerogammarus haemobaphes) freshwater amphipod species, across three temperatures (8°C, 14°C, and 20°C), and three leaf diets of varying resource quality (oak, sycamore, and alder) in laboratory microcosms. We also compared amphipod survival across the different temperature and diet treatments.Rates of detrital processing varied between the native and invasive non‐native amphipod species, with native G. pulex having a faster processing rate than both invasive non‐native species at the lower temperatures. However, as the temperature treatments increased, between‐species differences decreased, while the effects of leaf diets became more apparent. Although the survival probability did not vary with amphipod species, amphipod survival was higher at lower temperatures and in treatments containing higher quality leaf diets.We propose that the invasive non‐native Dikerogammarus species will affect native communities through lower rates of detrital processing; however, this impact may change under predicted climatic warming and be increasingly similar to native amphipod species.

Behavioural responses of invasive (Gmelinoides fasciatus) and native (Gammarus lacustris) amphipods to predators on different bottom substrates

Behavioural responses of invasive (Gmelinoides fasciatus) and native (Gammarus lacustris) amphipods to predators on different bottom substrates

The Ponto-Caspian and native amphipod life history in the Daugava River, Latvia

Population structure, reproductive parameters and other life history traits are among the main preconditions for alien amphipods’ successful invasion. In the freshwaters of Northern Europe, i.e. Latvia, the overall life history of alien Ponto-Caspian amphipods is little known. Furthermore, the population structure and reproductivity of native Gammarus pulex have not been studied in Latvian freshwaters. The aim of the study was to describe the life history of Gammarus varsoviensis, Pontogammarus robustoides and the coexistent G. pulex. Their population structure, reproductive period and fecundity in the Daugava River were evaluated as part of this study from 2017 to 2019. The results revealed that the reproductive period of G. varsoviensis and P. robustoides lasted from four to five months, with up to three generations per year and a high proportion of juveniles. The average number of eggs for G. varsoviensis was 31 (maximum: 69) and for P. robustoides 28 (maximum: 81), with ovigerous females of both species being an average of 11.3 mm. Gammarus pulex had one generation per year with a high proportion of juveniles. The average number of eggs per brood was 27 (maximum: 41) with the average size of ovigerous females being 10.7 mm.

Superior predatory ability and abundance predicts potential ecological impact towards early-stage anurans by invasive \u2018Killer Shrimp\u2019 (Dikerogammarus villosus)

Invasive alien species negatively impact upon biodiversity and generate significant economic costs worldwide. Globally, amphibians have suffered considerable losses, with a key driver being predation by large invasive invertebrate and vertebrate predators. However, there is no research regarding the potential ecological impact of small invertebrate invaders. The invasive freshwater amphipod Dikerogammarus villosus can act as a top predator capable of displacing native amphipods and preying heavily upon a range of native species. Listed as one of Europe’s top 100 worst invaders, D. villosus has significantly restructured freshwater communities across western Europe and is expected to invade North America in the near future. Here we explore the ecological impact of invasive D. villosus upon UK native and invasive amphibians (Rana temporaria and Xenopus laevis respectively) using the “Relative Impact Potential” (RIP) metric. By combining estimations of per capita effects (i.e. functional response; FR) and relative field abundances, we apply the RIP metric to quantify the potential ecological impact of invasive D. villosus upon embryonic and larval amphibian prey, compared to the native amphipod Gammarus pulex. Both native and invasive amphipods consumed early-stage amphibians and exhibited potentially destabilising Type II FRs. However, larger body size in invasive D. villosus translated into a superior FR through significantly lower handling times and subsequently higher maximum feeding rates—up to seven times greater than native G. pulex. Higher invader abundance also drove elevated RIP scores for invasive D. villosus, with potential impact scores predicted up to 15.4 times greater than native G. pulex. Overall, D. villosus is predicted to have a greater predatory impact upon amphibian populations than G. pulex, due primarily to its larger body size and superior field abundance, potentially reducing amphibian recruitment within invaded regions.

Ontogenetic shift in the trophic role of the invasive killer shrimp Dikerogammarus villosus: a stable isotope study

The introduction of the amphipod Dikerogammarus villosus in European fresh waters is to date recognized as a threat to the integrity of invaded communities. Predation by D. villosus on native benthic invertebrates is assumed as the key determinant of its ecological impact, yet available information describe the species as a primary consumer as well as a carnivore depending on local conditions. Here, we assessed the trophic position (TP) of D. villosus in Lake Trasimeno, a recently invaded lentic system in central Italy, using the CN isotopic signatures of individuals captured in winter spanning two orders of magnitude in body size. TP estimations were compared with those characterizing the native amphipod Echinogammarus veneris and other representative invertebrate predators. On average, D. villosus showed a trophic position higher than E. veneris, and comparable with that of odonate nymphs. An in-depth analysis revealed that large-sized individuals had a trophic position of 3.07, higher than odonates and close to that of the hirudinean predator Erpobdella octoculata, while small-sized specimens had a trophic position of 2.57, similar to that of E. veneris (2.41). These findings indicate that size-related ontogenetic shifts in dietary habits may per se vary the nature of the interaction between Dikerogammarus villosus and native invertebrates from competition to predation. Information collated from published isotopic studies corroborated the generality of our results. We conclude that intra-specific trophic flexibility may potentially amplify and make more multifaceted the impact of the species on other invertebrate species in invaded food webs.

Estuarine sediment toxicity testing with an indigenous subtropical amphipod

This study reports on a sediment toxicity test developed with a native amphipod strain of Ptilohyale barbicornis where sediments from 10 estuarine stations along the western coastline of Taiwan were evaluated with respect to trace metals and PAHs. The test was validated by determining dose–response relationships for aqueous copper, and cadmium and sodium dodecyl sulfate as well as copper-spiked sediment, showing a sensitivity of P. barbicornis indicating its capability serving as a toxicity test species. A significant negative correlation between growth effects after 28 days of exposure to field-collected contaminated sediments and PAHs concentrations was observed. Similarly, the chronic toxicity test showed that growth was mostly inhibited compared to controls, body lengths in particular being significantly different from controls (p < 0.05). Various estuarine sediment pollutants in the quality guidelines can be further evaluated using P. barbicornis to understand their comprehensive biological effects and ecological risks.

Experimental assessment of the predatory pressure effect of gammarids on the structure of the macrozoobenthic community (Communicated by Academician Mikhail E. Nikiforov)

Alien amphipods were found in Belarus in the early 2000s. During long-term observations of the macrozoobenthic community in the rivers, a decrease of native amphipods was revealed in the southern part of Belarus. Several laboratory experiments were conducted to reveal the predatory effects of four alien species ( Dikerogammarus haemobaphes (Eichwald, 1841), Echinogammarus ischnus (Stebbing, 1898), Obesogammarus crassus (Sars, 1894), Obesogammarus obesus (Sars, 1896) on some macrozoobenthic groups. D. haemobaphes has a maximum predation rate and a broad food spectrum in comparison with other studied species. The above-mentioned data can be one of the reasons of wide spreading and very abandoned populations of D. haemobaphes in various rivers in Belarus.

Native Gammarus fossarum affects species composition of macroinvertebrate communities: evidence from laboratory, field enclosures, and natural habitat

Despite the fact that native species of amphipods have been recognized as active predators similarly to invasive species, little is known about their predatory impact on aquatic communities. In this study, we used a laboratory experiment, a field enclosure experiment, and an analysis of natural community data to demonstrate how Gammarus fossarum affects the species composition of benthic communities by imposing survival selection on its prey. Our laboratory single-prey experiment brought a clear evidence that tube-less chironomids are vulnerable prey and that the predation rate on the tube-dwelling chironomids decreases with increasing tube toughness (from the soft tubes made of detritus to the hard tubes made of sand or calcium carbonate grains). We found that the introduction of G. fossarum to field enclosures significantly changed the species composition of a macroinvertebrate community at an experimental spring fen site. The soft-bodied, slow moving, and tube-less taxa were depleted the most. It appears that the observed patterns were a result of predator’s preference rather than encounter rate. Survival selection was detected also in natural communities across a large spatial scale. In accordance with the experiments, high densities of G. fossarum limited the proportion or abundance of vulnerable prey. Our study (1) provides the first convincing evidence that biotic interactions have a structuring effect on the spring fen communities, (2) documents how the predatory effect in a community depends on an interplay between the prey handling behaviour of the predator and species-specific susceptibility of prey, and (3) shows that an omnivorous native amphipod may have a strong impact on aquatic communities despite it is regarded less aggressive than its invasive relatives.

Pathogens of Dikerogammarus haemobaphes regulate host activity and survival, but also threaten native amphipod populations in the UK.

Dikerogammarus haemobaphes is a non-native amphipod in UK freshwaters. Studies have identified this species as a low-impact invader in the UK, relative to its cousin Dikerogammarus villosus. It has been suggested that regulation by symbionts (such as Microsporidia) could explain this difference in impact. The effect of parasitism on D. haemobaphes is largely unknown. This was explored herein using 2 behavioural assays measuring activity and aggregation. First, D. haemobaphes were screened histologically post-assay, identifying 2 novel viruses (D. haemobaphes bi-facies-like virus [DhbflV], D. haemobaphes bacilliform virus [DhBV]), Cucumispora ornata (Microsporidia), Apicomplexa, and Digenea, which could alter host behaviour. DhBV infection burden increased host activity, and C. ornata infection reduced host activity. Second, native invertebrates were collected from the invasion site at Carlton Brook, UK, and tested for the presence of C. ornata. PCR screening identified that Gammarus pulex and other native invertebrates were positive for C. ornata. The host range of this parasite, and its impact on host survival, was additionally explored using D. haemobaphes, D. villosus, and G. pulex in a laboratory trial. D. haemobaphes and G. pulex became infected by C. ornata, which also lowered survival rate. D. villosus did not become infected. A PCR protocol for DhbflV was also applied to D. haemobaphes after the survival trial, associating this virus with decreased host survival. In conclusion, D. haemobaphes has a complex relationship with parasites in the UK environment. C. ornata likely regulates populations by decreasing host survival and activity, but despite this benefit, the parasite threatens susceptible native wildlife.

Differences in the abilities of native and invasive amphipods to tolerate poor water quality and recolonise degraded habitats

It has been hypothesised that freshwater pollution may favour the establishment of tolerant invaders at the expense of less-tolerant residents. To test this, this study capitalises on the aftermath of a farm pollution incident, a slurry discharge to a small British stream, which eliminated the resident macroinvertebrate assemblage. Stream transplant bioassay experiments at the discharge site revealed a higher pollution tolerance of the invasive amphipod Crangonyx pseudogracilis and the isopod Asellus aquaticus than that of the native amphipod Gammarus duebeni celticus and the invasive Gammarus pulex. A. aquaticus recolonised the stream up to the discharge point within days, followed by C. pseudogracilis, then G. pulex, with G. duebeni celticus undetected after a month. Values of a macroinvertebrate-derived biotic index of organic water quality, the Average Score Per Taxon (ASPT), gradually increased up to the discharge point in the 30 days following the incident. In a larger-scale survey (72 river and 12 pond sites), inclusion/exclusion of Gammarus spp. had no effect on ASPT values, while inclusion of C. pseudogracilis increased values, despite an assumed equivalence of these amphipods in the index. Pollution could facilitate the establishment of tolerant invaders, and this has implications for biomonitoring.

Identificación molecular y distribución potencial del anfípodo terrestre &lt;i&gt;Talitroides topitotum&lt;/i&gt; (Crustacea:Amphipoda:Talitridae) en Costa Rica

El anfípodo terrestre, Talitroides topitotum, es un talítrido distribuido mundialmente en regiones subtropicales y templadas, con un amplio rango de distribución altitudinal, temperatura y humedad. Se colectaron y procesaron especímenes desde el año 2012 al 2016, mediante remoción-filtración de sustratos húmedos. Se identificaron taxonómicamente por características fenotípicas diagnósticas, se determinó su estado de desarrollo y se separaron por sexo. Se extrajo ADN de anfípodos completos, seguido de una PCR de los genes citocromo oxidasa subunidad 1 y del ARN ribosomal de la subunidad 16S. Se obtuvo un árbol filogenético por máxima verosimilitud con un modelo GTR-GAMMA. El análisis de la distribución potencial de T. topitotum se estimó utilizando 19 variables bioclimáticas. En este estudio, se amplía la distribución previamente reportada y en altitudes entre los 1900 a 595 m s.n.m. Se analizaron 39 localidades, en las cuales: 1) Hay presencia de T. topitotum, 2) no hubo presencia de anfípodos terrestres, 3) no hubo presencia de Talitroides sp., pero sí de un anfípodo nativo. La abundancia proporcional de T. topitotum se inclina hacia las hembras adultas, una proporción alta de juveniles y no se detectaron individuos machos. El análisis bioinformático determinó el posicionamiento taxonómico de la especie T. topitotum dentro del agrupamiento de anfípodos terrestres, además, la especie exógena diverge de Cerrorchestia hyloraina demostrando una separación filogenética entre especies, las cuales pueden estar compartiendo hábitats. T. topitotum, según el modelo de máxima entropía, posee una alta capacidad de dispersión y estaría siendo favorecida, en cuanto a su asentamiento y propagación, por elementos climáticos como temperatura, precipitación y humedad, y factores como la altitud. Nuestros hallazgos son relevantes para la toma de decisiones de manejo y monitoreo del desplazamiento de especies nativas de anfípodos terrestres en la región.