Freshwater tropical fish

The Baixada Maranhense Environmental Protection Area of the Brazilian state of Maranhão encompasses a biologically rich region that includes the basins of four principal rivers, the Mearim, Pericumã, Pindaré, and Turiaçu, which form a complex of wetlands. The present study provides a comprehensive inventory of the fish fauna of the rivers that drain the Baixada Maranhense based on the identification of voucher specimens that were deposited in a scientific collection. Expeditions were conducted between 2014 and 2020...

Thiamine (vitamin B1 ) is required by all living organisms in multiple metabolic pathways. It is scarce in natural systems, and deficiency can lead to reproductive failure, neurological issues, and death. One major cause of thiamine deficiency is an overreliance on diet items containing the enzyme thiaminase. Thiaminase activity has been noted in many prey fishes and linked to cohort failure in salmonid predators that eat prey fish with thiaminase activity, yet it is generally unknown whether evolutionary history, fish traits, and/or environmental conditions lead to production of thiaminase...

Tropical freshwater lakes are well known for their high biodiversity, and particularly the East African Great Lakes are renowned for their adaptive radiation of cichlid fishes. While comparative phylogenetic analyses of extant species flocks have revealed patterns and processes of their diversification, little is known about evolutionary trajectories within lineages, the impacts of environmental drivers, or the scope and nature of now-extinct diversity. Time-structured palaeodata from geologically young fossil records, such as fossil counts and particularly ancient DNA (aDNA) data, would help fill this large knowledge gap...

During a research on morphological diversity of gill ectoparasites on native and non-native fishes from tributaries (Palizada, El Recreo and Lacantún rivers) of the Usumacinta River Basin in the states of Campeche, Tabasco, and Chiapas (southern Mexico), the following monogenoids were found: Icelanonchohaptor tropicalis n. sp. on Usumacinta buffalo Ictiobus meridionalis (Günther, 1868) (Catostomidae); Heteropriapulus simplexiodes n. sp. and Heteropriapulus heterotylioides n. sp. on catfishes Pterygoplichthys pardalis (Castelnau, 1855) (Loricariidae) (type host) and Pterygoplichthys disyunctivus (Weber, 1991); Ligictaluridus mirabilis (Mueller 1937; Klassen and Beverley-Burton1985 from the southern blue catfish Ictalurus meridionalis (Günther, 1864) (Ictaluridae); Aristocleidus mexicanus Mendoza-Franco and Vidal-Martínez, 2001 on Eugerres mexicanus (Steindachner, 1863) (Gerreidae) (all monogenoidean species in the Dactylogyridae); and Diplectanocotyla megalopis Rakotofiringa and Oliver1987 (Diplectanidae) on tarpon Megalops atlanticus Valenciennes, 1847 (Megalopidae)...

Biological invasions are expected to alter food web structure, but there are limited empirical data directly comparing invaded versus uninvaded food webs, particularly in species-rich, tropical systems. We characterize for the first time the food web of Lake Gatun - a diverse and highly-invaded tropical freshwater lake within the Panama Canal. We used stable isotope analysis to reconstruct the trophic structure of the fish community of Lake Gatun, and to compare it to that of a minimally-invaded reference lake, Lake Bayano...

Globally, small temporarily closed estuaries are the least considered for fisheries assessment and management due to a low scientific priority and regional importance. However, these ecosystems are highly exposed to anthropogenic pressures and may deteriorate without assessing its aquatic resources. In this study, fish diversity and guild structure of Chettuva-a temporarily closed tropical estuary in the western coast of India-was investigated. A total of 70 fish taxa belonging to 32 families were recorded with the quantitative predominance of families; Mugilidae, Cichlidae, and Leiognathidae...

Tropical lands harbour the highest number of species, resulting in the ubiquitous latitudinal diversity gradient (LDG). However, exceptions to this pattern have been observed in some taxa, explained by the interaction between the evolutionary histories and environmental factors that constrain species' physiological and ecological requirements. Here, we applied a deconstruction approach to map the detailed species richness patterns of Actinopterygian freshwater fishes at the class and order levels and to disentangle their drivers using geographical ranges and a phylogeny, comprising 77% (12 557) of all described species...

Understanding how anthropization impacts the assembly of species onto communities is pivotal to go beyond the observation of biodiversity changes and reveal how disturbances affect the environmental and biotic processes shaping biodiversity. Here, we propose a simple framework to measure the assembly processes underpinning functional convergence/divergence patterns. We applied this framework to northern Amazonian fish communities inventoried using environmental DNA in 35 stream sites and 64 river sites. We found that the harsh and unstable environmental conditions characterizing streams conveyed communities towards functional convergence, by filtering traits related to food acquisition and, to a lower extent, dispersal...

AIMS: The bacterial communities associated with the gastrointestinal tract are primarily involved in digestion, physiology and immune response against pathogenic bacteria for the overall development and health of the host. Hilsa shad (Tenualosa ilisha), a tropical anadromous fish, found predominantly in Bangladesh and India, has so far been poorly investigated for its gut bacterial communities. In this study, both culture-based and metagenomic approaches were used to detect intestinal isolates of hilsa, captured from both freshwater and seawater to investigate the community structure of intestinal microbiota...

The expansion of oil palms has led to land-use change and deforestation in the tropics, affecting biodiversity. While the impacts of the crop on terrestrial biodiversity have been extensively reviewed, the effects on freshwater biodiversity remain relatively unexplored. We reviewed the research assessing the impacts of forest-to-oil palm conversion on freshwater biota, and the mitigating effect of riparian buffers on these impacts. First, we search for studies comparing taxon richness, abundance, and community composition of macroinvertebrates, amphibians, and fish in streams in forests (primary and disturbed) and oil palm plantations with and without riparian buffers...

Dietary information from aquatic organisms is instrumental in predicting biological interactions and understanding ecosystem functionality. In freshwater habitats, generalist fish species can access a diverse array of food sources from multiple food chains. These may include primary photosynthetic production and detritus derived from both oxic and anoxic decomposition. However, the exploitation of anoxic decomposition products by fish remains insufficiently explored. This study examines feeding habits of striped catfish (Pangasianodon hypophthalmus) at both adult and juvenile stages within a tropical reservoir, using stable carbon, nitrogen, and sulfur isotope ratios (δ13 C, δ15 N, and δ34 S, respectively) and fatty acid (FA) analyses...

Redclaw crayfish (Cherax quadricarinatus) is a large, tropical freshwater crustacean species with considerable potential of commercial production. In recent years, infection with DIV1 in redclaw crayfish is being reported in aquaculture industries, causing high mortality and huge economic losses. However, many characteristics of this virus, including pathogenesis, transmission mechanism, and host immunity, remain largely unknown.MicroRNAs are known to play important roles in numerous biological processes, and many microRNAs are reported to be involved in the regulation of immune responses...

Organisms that are similar in size, morphological characteristics, and adaptations, including vertebrates, often coexist by partitioning the available resources (food, space, and time). So, studies of the dynamics of these cases of coexistence are scientifically interesting. Here, we study a coexistence case of two species of freshwater turtles inhabiting the forest waterbodies of West Africa, focusing on the dietary habits of the two species. We found that both turtle species are omnivorous generalists, eating both vegetal and animal matter abundantly...

BACKGROUND: Tilapia is one of the most essential farmed fishes in the world. It is a tropical and subtropical freshwater fish well adapted to warm water but sensitive to cold weather. Extreme cold weather could cause severe stress and mass mortalities in tilapia. The present study was carried out to investigate the effects of cold stress on the up-regulation of antifreeze protein (AFP) genes in Nile tilapia (Oreochromis niloticus). Two treatment groups of fish were investigated (5 replicates of 15 fish for each group in fibreglass tanks/70 L each): 1) a control group; the fish were acclimated to lab conditions for two weeks and the water temperature was maintained at 25 °C during the whole experimental period with feeding on a commercial diet (30% crude protein)...

Venomous fish are commonly found in Brazilian waters. The most important marine venomous fish species are stingrays (Dasyatidae, Gimnuridae, Myliobatidae, and Rhinopteridae families), catfish (Ariidae family), scorpionfish and lionfish (both Scorpaenidae family), and toadfish (Batrachoididae family). Meanwhile, Potamotrygonidae stingrays and Pimelodidae catfish are the most important venomous freshwater fish. The mechanisms of envenomation vary and involve various venomous apparatuses and glands. Despite not being highly developed, these venomous apparatuses in fish appear rudimentary, using structures such as fins and rays to inoculate toxins and rarely presenting with specialized structures...

One of the largest restoration programs in the world, the Comprehensive Everglades Restoration Plan (CERP) aims to restore freshwater inputs to Everglades wetlands and the Florida Bay estuary. This study predicted how the Florida Bay ecosystem may respond to hydrological restoration from CERP within the context of contemporary projected impacts of sea-level rise (SLR) and increased future temperatures. A spatial-temporal dynamic model (Ecospace) was used to develop a spatiotemporal food web model incorporating environmental drivers of salinity, salinity variation, temperature, depth, distance to mangrove, and seagrass abundance and was used to predict responses of biomass, fisheries catch, and ecosystem resilience between current and future conditions...

Implementation of the European Water Framework Directive in tropical areas such as the French West Indies (FWI) requires to select relevant aquatic sentinel species for investigating the ecological status of surface waters. The present work aimed to study the biological response of the widespread fish Sicydium spp. towards river chemical quality in Guadeloupe island through a set of proper biomarkers. During a 2-year survey, the hepatic EROD activity, the micronucleus formation and the level of primary DNA strand breaks in erythrocytes were measured respectively as an enzymatic biomarker of exposure and genotoxicity endpoints in fish living upstream and downstream of two chemically-contrasted rivers...

Labeo rohita is a widely cultivated tropical freshwater carp and found in rivers of South Asian region. A new cell line, designated LRM, has been developed from the muscle tissue of L. rohita . Muscle cells were subcultured up to 38 passages in a Leibovitz's-15 (L-15) supplemented with 10% FBS (Fetal Bovine Serum) and 10 ng/ml bFGF. The LRM cells exhibited fibroblastic morphology with a doubling time of 28 h, and a plating efficiency of 17%. A maximum growth rate was observed for LRM cells at 28 °C, 10% FBS and 10 ng/ml bFGF...

Ocean warming is associated with the tropicalization of fish towards higher latitudes. However, the influence of global climatic phenomena like the El Niño Southern Oscillation (ENSO) and its warm (El Niño) and cold (La Niña) phases on tropicalization has been overlooked. Understanding the combined effects of global climatic forces together with local variability on the distribution and abundance of tropical fish is essential for building more accurate predictive models of species on the move...

Poeciliids are widely recognised as successful invaders, possessing traits associated with invasion success. Native to Central America and south-eastern Mexico, the twospot livebearer (Pseudoxiphophorus bimaculatus) is a species recently recognised as invasive in both Central and Northern Mexico. Despite its invasive status, limited research exists on its invasion process and the potential threats it poses to native species. In this study, we conducted a comprehensive review of the current knowledge on the twospot livebearer and mapped its current and potential distribution worldwide...