Myxobolus shuifuensis sp. n. (Myxozoa: Myxobolidae) infecting the exotic mrigal Cirrhinus mrigala feral in China.

Myxobolus species represents a group of cosmopolitan metazoan parasites commonly harbored in the farmed and wild fish populations. Here, a species of Myxobolus is found in the kidney of an exotic mrigal Cirrhinus mrigala feral in the Yangtze River and utilized for an integrative characterization. Ellipsoidal myxospores are measured at 15.68 ± 0.8 (13.93-17.11) × 11.42 ± 0.54 (10.34-12.3) × 7.94 ± 0.35 (7.58-8.5) µm in dimension. The polar capsules are pyriform, and unequal in size. The morphological and morphometric characteristics of the present isolates are distinct from those of other congeners. Molecularly, the pairwise comparison based on the SSU rDNA sequence indicates that the present amplicon does not match any sequences available in the GenBank database and shares the highest similarity of 92.12% to Myxobolus pavlovskii (MG520369). Accordingly, we propose a name Myxobolus shuifuensis sp. n. for the present isolates. Phylogenetical trees indicate an apparent host-associated phylogenetic pattern. M. shuifuensis sp. n. groups loosely with other Myxobolus species isolated from Cirrhinus fish. Insead, it forms a sister clade to some myxosporeans belonging to the Thelohanellus genus. This result underpins the species identification and provides evidence for challenging the taxonomic separation among both morphologically comparable genera.

Gut milieu shapes the bacterial communities of invasive silver carp.

Silver carp is an invasive fish present in the Gobindsagar reservoir, India and has a profound impact on aquaculture. Understanding taxonomic diversity and functional attributes of gut microbiota will provide insights into the important role of bacteria in metabolism of silver carp that facilitated invasion of this exotic species. Microbial composition in foregut, midgut, hindgut and water samples was analysed using 16S rRNA gene amplicon sequencing. The bacterial communities of water samples were distinct from gut microbiota, and unique microbial assemblages were present in different regions of gut depicting profound impact of gut environment on microflora. Proteobacteria was the most abundant phyla across all samples. Ecological network analysis showed dominance of competitive interactions within posteriors region of the gut, promoting niche specialization. Predictive functional profiling revealed the microbiota specialized in digestive functions in different regions of the gut, which also reflects the dietary profile of silver carp.

First genetic record of the non-native muzzled blenny Omobranchus punctatus (Teleostei: Blenniidae) in the Atlantic Coast of Central and South America.

In this study we sequenced two mitochondrial (COI and 16S rRNA) and one nuclear (18S rRNA) gene fragment of an introduced muzzled blenny (Omobranchus punctatus) specimen collected from the Orinoco Delta (Gulf of Paria estuary) in Venezuela. This is the first genetic data generated for this species' introduced range in Central and South America, suggesting an introduction from the Indian Ocean.

Differential activities of the multixenobiotic resistance mechanism in freshwater fishes inhabiting environments of Patagonia Argentina.

Environmental impairment resulted from urbanizations can produce damage on freshwater species including strong physiological effects at individual or population level. The multixenobiotic resistance (MXR) is a defence mechanism which has been demonstrated in several aquatic organisms. The key mediators of MXR activity are ATP-binding cassette (ABC) proteins like P-glycoprotein (P-gp). This system protects aquatic organisms against the accumulation of xenobiotics by extruding them from cells in an energy-dependent manner. MXR has been pointed out as relevant in the ecotoxicological context and has been proposed as a biomarker for pollution assessment. Since fish species are common target in freshwater biomonitoring programs, the purpose of the study was to evaluate the MXR mechanism in native Hatcheria macraei (Patagonian catfish) and exotics Salmo trutta (brown trout), Oncorhynchus mykiss (rainbow trout) and Oncorhynchus tshawytscha (Chinook salmon) freshwater fishes widespread in Argentine Patagonia. We characterized the MXR mechanism using a combination of functional assays and Western blot analysis. Our results in different tissues such as liver, gills, muscle and epidermis indicate that the fishes studied have different species-specific levels of MXR activity, being gills and liver the tissues with greater detoxifying activity. Induction of MXR transport activity was also identified in liver tissue from rainbow trout from urban stream suggesting their suitability in the biomonitoring of aquatic environments subjected to urban contaminants.

Predicting New Zealand riverine fish reference assemblages.

Biomonitoring is a common method to monitor environmental change in river ecosystems, a key advantage of biomonitoring over snap-shot physicochemical monitoring is that it provides a more stable, long-term insight into change that is also effects-based. In New Zealand, the main biomonitoring method is a macroinvertebrate sensitivity scoring index, with little established methods available for biomonitoring of fish. This study models the contemporary distribution of common freshwater fish and then uses those models to predict freshwater fish assemblages for each river reach under reference conditions. Comparison of current fish assemblages with those predicted in reference conditions (as observed/expected (O/E) ratios) may provide a suitable option for freshwater fish biomonitoring. Most of the fish communities throughout the central North Island and lower reaches show substantial deviation from the modelled reference community. Most of this deviation is explained by nutrient enrichment, followed by downstream barriers (i.e. dams) and loss of riparian vegetation. The presence of modelled introduced species had relatively little impact on the presence of the modelled native fish. The maps of O/E fish assemblage may provide a rapid way to identify potential restoration sites.

Proposing priorities of intervention for the recovery of native fish populations using hierarchical ranking of environmental and exotic species impact.

The freshwater populations of native fish species (Ns) have reached critical levels in many parts of the world due to combined habitat deterioration by human interventions and exotic fish species (Es) invasions. These alarming conditions require combined and well-designed interventions for restoring environmental quality and restricting Es invasion. The aim of the study is to propose a method to design spatially explicit priorities of intervention for the recovery of Ns populations in highly impacted freshwater systems by exotic multi-species invasion and water quality (WQ) degradation. WQ and Es are used as Ns descriptors, which require intervention. The method uses gradient analysis (ordination method of Canonical Correspondence Analysis) for assessing the weights of Ns descriptors' effects, which are further used to develop weighted severity indices; the severity index of WQ (Swq) and Es invasion (Se), respectively. Swq and Se are further merged to one combined total severity index St. The proposed method provides a) a ranking of the sites, based on the values of St, which denotes the priority for combined intervention in space and can be visualized in maps, b) a ranking of the most important Ns descriptors for each site to perform site-specific interventions, and c) Es rankings based on their potential threat on Ns for species-specific interventions. WQ, Es and Ns data from 208 sampling sites located in the Emilia-Romagna Region (Northern Italy) were used as a case study for the presentation of the proposed method. The application of the method showed that the north and northwestern lowland areas of Emilia-Romagna region presented the higher priority for intervention since the Ns of these areas are the most impacted from combined Es invasions and WQ degradation. Specific Es belonging to cyprinids, which are mostly responsible for the decline of aquatic vegetation and the increase of water turbidity, and a top Es predator (Wels catfish) were mostly present in these areas. Additionally, the most important WQ stressors of Ns were found to be COD, BOD and temperature that are all connected to oxygen depletion. The aforementioned conditions in the areas described by high priority for intervention can be used as a basis for the development of specific Ns conservation practices targeting the containment of the most harmful Es, the restoration of aquatic vegetation and the improvement of oxygen conditions.

Dispersion of the invasive common carp Cyprinus carpio in southern South America: changes and expectations, westward and southward.

Common carp Cyprinus carpio possess multiple traits that contribute to their success as an invasive species. They have been introduced across the globe, and abundant populations can have numerous negative effects. Although ecological niche-based modelling techniques have been used to predict the potential range of C. carpio invasion in U.S.A., occurrence and abundance patterns have not yet been considered on a regional scale. In the present review new locations are documented, the status of the southernmost population has been studied and the probability of new lakes and reservoirs being colonized by C. carpio has been obtained and related to environmental conditions. The new localities for C. carpio have expanded its distribution westward, into the Andean Region, and present results from the South American southernmost population have shown a well-established population. Analysis of presence data provided two principal results: (1) the probability of a site being with C. carpio can be inferred using environmental variables and (2) the probability of a site being with C. carpio is a useful tool for the prediction of future invasions. Selective fishing on the Negro basin could constitute a potential mitigation measure, decreasing the abundance of the species and thus reducing the species' potential for southward expansion. These results reinforce the idea that artisanal fisheries, food production and conservation interests should be taken into account by local government management agencies in any discussion regarding the southern distribution of C. carpio in the near future.

Parasites of two coexisting invasive sailfin catfishes (Siluriformes: Loricariidae) in a tropical region of Mexico

Currently many species of Amazon sailfin catfishes (Loricariidae) have been introduced to wild environments outside their native range. There is, however, little knowledge about their role as vectors of parasites that can infect native fish or even humans through its consumption. The aim of the present study was to determine the parasitic fauna of the invasive sailfin catfish species Pterygoplichthys pardalis (leopard pleco) and P. disjunctivus (vermiculated pleco) from freshwater systems in the southeast of Mexico. Four ectoparasite species were found in P. pardalis (1 protozoan: Ichthyophthirius multifiliis ; 2 monogeneans: Urocleidoides vaginoclastrum and Heteropriapulus heterotylus ; 1 digenean: Clinostomum sp.), and only one in Heteropriapulus disjunctivus (H. heterotylus ). No endoparasites were found. Ichthyophthirius multifiliis , U. vaginoclaustrum and Clinostomum sp. , were considered as rare species (prevalence <5%) since they were found in a single individual of P. pardalis . H. heterotylus was the only species shared among both host species and it occurs throughout the year. This monogenean species represents 96% of total parasites recorded in P. pardalis and 100% in P. disjunctivus. Monthly values of prevalence, intensity and abundance of H. heterotylus in both host species showed important intra-annual variations, but not differ significantly between both hosts.(AU)

Actualmente muchas especies de peces conocidos como plecos o peces diablo (Loricariidae) han sido introducidas en ambientes silvestres fuera de su área de distribución natural. Sin embargo, hay poco conocimiento acerca de su papel como vectores de parásitos que puedan infectar a los peces nativos o incluso los seres humanos a través de su consumo. El objetivo del presente estudio fue determinar la fauna parasitaria de las especies de plecos Pterygoplichthys pardalis (pleco leopardo) y P. disjunctivus (pleco vermiculado) en sistemas de agua dulce del sureste de México. Fueron encontradas cuatro especies de ectoparásitos en P. pardalis (1 protozoario: Ichthyophthirius multifiliis ; 2 monogeneos: Urocleidoides vaginoclastrum y Heteropriapulus heterotylus ; 1 digeneo: Clinostomum sp.) y una en P. disjunctivus (H. heterotylus ). No se encontraron endoparásitos. Ichthyophthirius multifiliis, U. vaginoclaustrum y Clinostomum sp. fueron consideradas como especies raras (prevalencia <5%), ya que estuvieron en un solo individuo de P. pardalis . Heteropriapulus heterotylus fue la única especie compartida entre ambas especies de peces y que estuvo presente durante todo el año, y representó el 96% del total de parásitos registrados en P. pardalis y el 100% en P. disjunctivus. La prevalencia, intensidad media y abundancia media de H. heterotylus mostraron importantes variaciones intra-anuales en ambas especies de peces, pero no difirió significativamente entre ambos hospederos.(AU)

Diet shift of Red Belly Pacu Piaractus brachypomus (Cuvier, 1818) (Characiformes: Serrasalmidae), a Neotropical fish, in the Sepik-Ramu River Basin, Papua New Guinea

Introduction of fish species is a globally widespread practice that causes losses of native species and homogenization of diversity within and across continents. Diet assessments are important tools to depict the ecological function of species introduced into novel ecosystem and possible direct and indirect ecological effects. In this study, we compare the diet of Piaractus brachypomus, a mainly frugivorous Neotropical fish, introduced into the Sepik-Ramu River Basin (Papua New Guinea) nearly two decades ago, to that of similar size individuals from Neotropical populations in the Amazon and Orinoco River basins (South America). In contrast to native populations that feed mainly on terrestrial plants and invertebrates, the diet of introduced P. brachypomus is mainly composed of fish remains and aquatic plants, while terrestrial plants are frequently consumed but in relatively smaller amounts. These findings show that P. brachypomus has an inherently plastic diet that can be adjusted when displaced to a novel geographic area. While trophic plasticity increases the likelihood of a species to establish breeding populations after its introduction, it also reduces our ability to predict negative effects on native species.

La introducción de peces es una práctica que se extiende globalmente y que causa perdida de especies nativas y homogenización de la diversidad dentro y entre continentes. Los estudios de dieta son herramientas útiles para definir la función ecológica de una especie introducida en un ecosistema nuevo y los posibles efectos directos e indirectos. En este estudio describimos la dieta de Piaractus brachypomus, una especie de pez Neotropical principalmente frugívora, que fue introducida en el río Sepik (Papua Nueva Guinea) hace casi dos décadas; y la comparamos con aquella de individuos de tamaño corporal similar de poblaciones nativas en las cuencas de los ríos Amazonas y Orinoco (América del Sur). En contraste con las poblaciones nativas que se alimentan principalmente de frutas y semillas, plantas e invertebrados terrestres, la dieta de individuos de P. brachypomus introducidos se compone principalmente de restos de peces y plantas acuáticas, mientras que plantas terrestres son consumidas frecuentemente pero en pequeñas cantidades. Estos resultados indican que P. brachypomus tiene una dieta plástica que puede adaptarse cuando la especie se desplaza a un área geográfica nueva. A pesar de que la plasticidad trófica aumenta la probabilidad de que una especie establezca poblaciones reproductivas después de la introducción, también reduce nuestra habilidad de predecir los efectos negativos sobre especies nativas.

Interactions between benthic macroinvertebrates and fishes in a low order stream in Campos de Cima da Serra, RS, Brazil / Interações entre macroinvertebrados bentônicos e peixes em um rio de baixa ordem nos Campos de Cima da Serra, RS, Brasil

Benthic macroinvertebrates constitute the link between organic matter input in streams and fishes. However, the possibility of influence of predators on the invertebrates is still a controversial issue. The possibility of alteration of the benthic community by the modification in predation in a stream in the South of Brazil was studied by means of an exclusion experiment under semi-natural conditions. The exclusion showed an increase in the abundance of Plecoptera in the river where the rainbow trout was introduced, the larvae of Trichoptera also increased in abundance in the units of fish exclusion. This difference does not confirm the pressure applied by the trout on the benthic macro fauna due to differences in ichthyofauna and in the habitat of both rivers. Nevertheless, it points to the need for the development of studies concerning the trophic relations and the possible effects of this introduction in the aquatic biota.

Os macroinvertebrados bentônicos exercem a ligação entre a entrada de matéria orgânica nos rios e os peixes. Porém, a possibilidade de influência dos predadores sobre os invertebrados é uma questão ainda controversa. A possibilidade de alteração da comunidade bentônica, pela modificação na predação em um rio no sul do Brasil, foi estudada através de um experimento de exclusão em condições seminaturais. A exclusão resultou no aumento na abundância de Plecoptera no rio onde é feita a introdução de truta arco-íris; as larvas de Trichoptera também aumentaram em abundância nas unidades onde se efetuou a exclusão. Essa diferença não pode ser atribuída à presença das trutas, devido às diferenças na ictiofauna e de habitat dos dois rios. Entretanto mostra a necessidade de desenvolvimento de estudos acerca das relações tróficas e possíveis efeitos desta introdução sobre a biota aquática