Search Results (23)

This article has examined the effects of magnetic fields with intensities of 1 mT, 3 mT, and 5 mT on two species of cichlid fish (family Cichlidae). This study focused specifically on assessing the influence of these magnetic fields on larval development, the survival rate, and the occurrence of deformities in the larvae of the jaguar cichlid (Parachromis managuensis) and the green terror (Andinoacara rivulatus). The analysis of the study results indicates that the effects of magnetic field exposure depend both on its intensity and on the fish species being studied. Magnetic fields, depending on the applied intensity, can influence changes in body size as well as the size of the yolk sac. In jaguar cichlid larvae, increased survival was observed in the groups exposed to the magnetic field; however, this was accompanied by a higher number of deformities compared with the control group. In the case of the green terror, the highest survival rates were recorded in the control group and in the group exposed to a magnetic field of 3 mT, while increased numbers of deformities were also noted in the exposed groups. The obtained results may be of significant importance for ornamental fish aquaculture, where appropriately selected magnetic field parameters could support larval growth and survival, reducing losses in breeding. Full article

A field study on the biparental convict cichlids (Amatitlania siquia) in Lake Xiloá, Nicaragua was conducted to understand how the loss of a parent’s parental care affects the antipredator behavior of both parents and offspring during intruder events. We hypothesized that the combined efforts of two parents would result in increased intruder aggression and decreased offspring dispersion compared to single-parents of either sex, and that single-females and males would differ in their ability to deter predators and manage offspring dispersion. Both parents in a pair chased half the intruders that single-females did and the same number as single-males, suggesting that the presence of a partner deters intruders from encroaching and affords parents more time to engage in other parental care duties. Compared to single-parents, offspring accompanied by both parents were seldom left alone and showed greater shoal cohesion—both of which would presumably lower their risk of predation. Although there were sex differences between single-parents in terms of how often they left their offspring unattended and called to them using pelvic fin-flicks, neither sex was found to be more effective at managing the distribution of their offspring. This field study provides empirical evidence to support the need for biparental care in this species and gives insight into the selection pressures shaping parental investment. Full article

Clinostomum is a genus of parasitic trematodes found worldwide, infecting a wide range of hosts, including freshwater fishes, snails, birds and occasionally humans. In this study, clinostomid metacercariae were collected from Nile tilapia raised in fish farms in the Upper Tana River region, Kenya. The prevalence of infection was 17.2%, with metacercariae infecting the skin, gills and buccal cavity of the fish. Using light microscopy, scanning electron microscopy (SEM) and molecular methods targeting both nuclear ribosomal (ITS1, 5.8S, ITS2) and mitochondrial (COI) regions, the metacercariae were identified as C. cutaneum, C. phalacrocoracis, C. tilapiae and Euclinostomum heterostomum. The three species of Clinostomum have previously been reported to infect fish or piscivorous birds in Kenya, while this is the first report of E. heterostomum in this country. SEM analysis revealed new ultrastructural features of C. cutaneum, including an excretory pore surrounded by minute spiny papillae, an everted cirrus and dome-shaped papillae on the tegumental area around the genital pore. The cirrus lacked basal papillae, showing morphological variation between the adult and metacercarial stages. Our study, therefore, provides new insights into the phenotypic identification of flukes that may be pathogenic to fishes and humans and, therefore, of scientific and practical importance. Full article

The upper Malagarazi (uM) Basin is situated in Southeastern Burundi and Northwestern Tanzania, and partially covered by the Malagarazi Nature Reserve (MNR). A checklist of fishes from the uM, in Burundi, is presented based on a literature review, a re-examination of historical collections, and a study of new collections (2013–2022). A total of 74 native species, including 14 endemics and two introduced Oreochromis, distributed over 38 genera and 16 families, are reported. Of the aforementioned species, 60 native (81%) and one introduced are present in the MNR. The most important families in the uM and the MNR are the Cyprinidae (21 versus 17 species, respectively) and Cichlidae (12 versus 11). Other families are represented by less than 10 species in both the uM and the MNR. Furthermore, of the 14 species endemic to the uM (19%), only eight (57%) are reported from the MNR; the others are confined to some non-included affluent rivers. Moreover, eight taxa still await formal description. Finally, as some endemic and native species are not included within the current borders of the MNR, adjustments are proposed and the need for a new protected area is considered. Full article

Fish in the Volga-Kama River System (the largest river system in Europe) are important as a crucial food source for local populations; fish have the highest trophic level among hydrobionts. The purpose of this research is to describe the diversity of non-indigenous and native fish in the Volga and Kama Rivers, in the European part of Russia. This dataset encompasses data from June 2001 to September 2021 and comprises 1888 records (36,376 individual observations) for littoral and pelagic habitats from 143 sampling sites, representing 52 species from 42 genera in 22 families. The dataset has a Darwin Core standard format and has been fully released in the Global Biodiversity Information Facility (GBIF) under CC-BY 4.0 International license. The data are validated with several international databases such as FishBase, Eschmeyer’s Catalog of Fishes, the Barcode of Life Data System, and the SAS.Planet geoinformations system. Newly established populations have been found for several species belonging to the following Actinopteri families: Alosidae, Anguillidae, Cichlidae, Ehiravidae, Gobiidae, Odontobutidae, Syngnathidae, and Xenocyprididae. Therefore, this dataset can be used in the particular taxon species distribution analysis, which are especially important for non-indigenous species. Full article

An annotated checklist of the ichthyofauna of the Upemba National Park, draining part of the Upper Lualaba basin and situated in the southern part of the Democratic Republic of the Congo, is presented, based on a literature review, a re-examination of museum collections, and a study of recent collections (2012–2020). In total, 247 native and 1 introduced species, Heterotis niloticus, are reported. The native species belong to 78 genera, 26 families, and 15 orders. Of these, 45 species (18%) are endemic to the park, 35 species (14%) await formal description, and 5 taxa (2%) need further study to clarify their status. With 51 species, the Cyprinidae is by far the most species-rich family, followed by the Mormyridae (26), Mochokidae (26), Alestidae (18), Distichodontidae (18), Amphiliidae (17), and Cichlidae (16). The remaining families are represented by less than 15 species. Comments about the species distribution and the fish fauna shared with adjacent ecoregions are provided. Although the park provides some protection for the fish species living within its borders by limiting human access to the core zone, the annex and buffer zones are both subject to strong anthropogenic pressure. These observations underscore the need for the implementation and further elaboration of fish-related preservation guidelines and plans to enable better protection/conservation of the park’s ichthyofauna. Full article

The mitogenomic evolution of old-world cichlids is still largely incomplete in Western Africa. In this present study, the complete mitogenome of the Cameroon endemic cichlid, Coptodon camerunensis, was determined by next-generation sequencing. The mitogenome was 16,557 bp long and encoded with 37 genes (13 protein-coding genes, two ribosomal RNA genes, 22 transfer RNA genes, and a control region). The C. camerunensis mitogenome is AT-biased (52.63%), as exhibited in its congener, Coptodon zillii (52.76% and 53.04%). The majority of PCGs start with an ATG initiation codon, except COI, which starts with a GTG codon and five PCGs and ends with the TAA termination codon and except seven PCGs with an incomplete termination codon. In C. camerunensis mitogenome, most tRNAs showed classical cloverleaf secondary structures, except tRNA-serine with a lack of DHU stem. Comparative analyses of the conserved blocks of two Coptodonini species control regions revealed that the CSB-II block was longer than other blocks and contained highly variable sites. Using 13 concatenated PCGs, the mitogenome-based Bayesian phylogeny easily distinguished all the examined old-world cichlids. Except for Oreochromini and Coptodinini tribe members, the majority of the taxa exhibited monophyletic clustering within their respective lineages. C. camerunensis clustered closely with Heterotilapia buttikoferi (tribe Heterotilapiini) and had paraphyletic clustering with its congener, C. zillii. The Oreochromini species also displayed paraphyletic grouping, and the genus Oreochromis showed a close relationship with Coptodinini and Heterotilapiini species. In addition, illustrating the known distribution patterns of old-world cichlids, the present study is congruent with the previous hypothesis and proclaims that prehistoric geological evolution plays a key role in the hydroclimate of the African continent during Mesozoic, which simultaneously disperses and/or colonizes cichlids in different ichthyological provinces and Rift Lake systems in Africa. The present study suggests that further mitogenomes of cichlid species are required, especially from western Africa, to understand their unique evolution and adaptation. Full article

The study of assemblages of fish in their early phases in estuaries is an essential approach to understanding the functioning of these types of ecosystems and their role as nursery grounds for some marine fish species. The main aim of this study was to analyze the ichthyoplankton assemblage in the Bons Sinais Estuary, specifically to clarify the use of this area by species of socio-economic interest. This study identified 22 fish larval taxa among families, genera, and species. Gobiidae (54%), a group of resident species, dominated the community. The larval taxa of socio-economic importance (Thryssa sp., Clupeidae, Sillago sihama, Johnius dussumieri, Pellona ditchela, Pomadasys kaakan, Cichlidae, and Mugilidae) accounted for 23% of the total abundance. Larval density (N°/100 m³) varied spatially and temporally, with higher density and diversity values both in the middle zone and in the wet season. Multivariate analyses revealed that salinity, temperature, and water transparency had a strong influence on larval abundance and density. While most fish larvae were in the post-flexion stage, there was a predominance of pre-flexion larvae in the lower estuary and in the post-flexion stage in the middle and upper zones, especially for marine fish resources, showing the role of this estuarine habitat as a nursery area. Full article

To better understand the diversity and evolution of cichlids, we sequenced, assembled, and annotated the complete mitochondrial genomes of three Nile tilapiine species (Coptodon zillii, Oreochromis niloticus, and Sarotherodon galilaeus) dominating the Nile River waters. Our results showed that the general mitogenomic features were conserved among the Nile tilapiine species. The genome length ranged from 16,436 to 16,631 bp and a total of 37 genes were identified (two ribosomal RNA genes (rRNAs), 22 transfer RNA genes (tRNAs), 13 protein-coding genes (PCGs), and 1 control region). The ND6 was the only CDS that presented a negative AT skew and a positive GC skew. The most extended repeat sequences were in the D-loop followed by the pseudogenes (trnS^GCU). The ND5 showed relatively high substitution rates whereas ATP8 had the lowest substitution rate. The codon usage bias displayed a greater quantity of NNA and NNC at the third position and anti-bias against NNG. The phylogenetic relationship based on the complete mitogenomes and CDS was able to differentiate the three species as previously reported. This study provides new insight into the evolutionary connections between various subfamilies within cichlids while providing new molecular data that can be applied to discriminate between Nile tilapiine species and their populations. Full article

Understanding the interspecific morphological variability of Caquetaia kraussii (Perciformes: Cichlidae) between different localities in its distribution range is becoming essential, as this species constitutes a valuable resource for the economy and subsistence of the local human communities where it is endemic in Colombia and Venezuela. In order to develop efficient farming and handling plans for this species, a deep understanding of the factors and mechanisms generating morphological variability is crucial. This study analyzes the morphological variability of C. kraussii by using geometric morphometrics in four localities distributed between the Dique and North channels, which are part of the Bolívar department in Colombia. Likewise, the effect of environmental variables such as temperature (T°), dissolved oxygen (OD) and pH on morphological variability was analyzed using a partial least squares approach. The results show that environmental stress has an influence on ~10% of the body shape of C. kraussii, whereas ~90% of the body shape is not directly influenced by environmental parameters, suggesting an effect from stress related to sexual dimorphism. Similarly, the analyses show shape variation among localities, mainly between populations of lotic environments and those of lentic environments. This morphological disparity seems to be subject to environmental and sexual stresses in the different localities. Full article

C. kraussii is an endemic fish species from Colombia and Venezuela and represents a valuable food resource for local human communities. Due to its economic importance, the management and captive breeding of this species are of special interest. However, the anatomical similarities between sexes have been a problem for visual identification. It is also important to indicate that C. kraussii has cryptic morphological behavior between sexes, a topic that has been one of the main problems for the implementation of management plans. The following research studied individuals from three different localities along the Canal del Dique, Bolívar Department in Colombia, in which the body shape of C. kraussii was analyzed using geometric morphometric analysis. The analyses detected the presence of intralocality sexual dimorphism in two of the three localities analyzed, showing a low morphological variability among males, presenting conserved body shape, as well as a greater morphological disparity among females. This sexual shape dimorphism may be associated with the environmental variation among different locations. These results suggest the presence of two evolutionary forces acting asymmetrically between the sexes of C. kraussii, with males mostly subject to sexual selection pressure, while females are mainly subject to environmental pressures. Full article

The development of techniques that assist in the processes of taxonomic identification is of utmost importance, considering the scarcity of specialists and literature available in remote and diverse areas. Environmental studies such as the Biodiversity Monitoring Program of the Carajás National Forest in northern Brazil (FLONA de Carajás—PA, 6°6′29′′ S, 50°18′16′′ W) face challenges in this regard. These challenges include the particularity of the morphological and evolutionary characteristics of the fauna, present in a very diverse area of intense anthropogenic intervention by the use of resources of economic interest. Thus, this work sought to analyze the efficiency of using Artificial Neural Networks (ANN), more specifically the “XCeption” algorithm, configured for the taxonomic identification of samples captured during this monitoring program. These samples were previously identified using traditional taxonomic identification keys. The taxa Aequidens tetramerus, Astyanax abramis, Bryconops spp., Knodus spp., and Moenkhausia spp. were used. After capturing the images, the content was assigned to different folders, named “Training” and “Test”. This procedure seeks to quantify the model’s ability to classify data characteristically different from that presented in the training base. The accuracy results obtained during the training phase of the algorithm used, executed in about 16 hours, were 98% for the Training phase and 92% for the Validation phase, with some categories presenting better prediction results, such as classes 4 (100%) and 2 (85%). The testing phase, executed in about 1 hour, obtained an accuracy value of 78.26%, with a 95% confidence interval (63.64–89.05%) and a kappa of 70%. The applied methodology presented high accuracy, configuring itself as an important tool for identifying fish species in extremely diverse and remote environments. Full article

Mangroves have been recognized worldwide as crucial nursery areas for fish larvae and juveniles. Although they are critical for managing coastal fish stocks, information about larval fish communities in African island mangroves is scarce and these potential nursery areas in São Tomé Island have remained understudied. Fish larvae were collected over four weeks from October to November 2020 using light traps, passive plankton tows and seine nets in a multi-habitat approach. To overcome species identification constraints, both morphology and molecular analysis were considered. A total of 4 010 larvae were caught across all methods belonging to 16 families or 26 species. A few species dominated the ichthyoplankton community and the most abundant families were Cichlidae—especially the invasive Oreochromis mossambicus (47%)—and Gobiidae (43%), constituted by 7 taxa. The remaining 14 families only accounted for about 10% of total larvae captured. Three new species were recorded for the first time in the island mangroves and another three species were documented for the first time in the São Tomé Island. Taxa composition and richness varied considerably between sampling techniques. The highest taxa richness and diversity were recorded in the Malanza mangrove (25 species) while Praia das Conchas (9 species) was not able to sustain similar levels of biodiversity. Differences on fish larvae composition were found within the studied mangroves, depicting a strong influence of habitat type and a relative position within each system. These community composition patterns were marginally influenced by local environmental conditions such as temperature and dissolved oxygen. Overall, a total of eleven taxa have commercial interest and their presence as juveniles and larvae in São Tomé mangroves reinforces the need for conservation of these ecosystems and shows direct implications for the sustainability of the local fisheries. Full article

African cichlid fishes harbor an extraordinary diversity of sex-chromosome systems. Within just one lineage, the tribe Haplochromini, at least 6 unique sex-chromosome systems have been identified. Here we focus on characterizing sex chromosomes in cichlids from the Lake Victoria basin. In Haplochromis chilotes, we identified a new ZW system associated with the white blotch color pattern, which shows substantial sequence differentiation over most of LG16, and is likely to be present in related species. In Haplochromis sauvagei, we found a coding polymorphism in amh that may be responsible for an XY system on LG23. In Pundamilia nyererei, we identified a feminizing effect of B chromosomes together with XY- and ZW-patterned differentiation on LG23. In Haplochromis latifasciatus, we identified a duplication of amh that may be present in other species of the Lake Victoria superflock. We further characterized the LG5-14 XY system in Astatotilapia burtoni and identified the oldest stratum on LG14. This species also showed ZW differentiation on LG2. Finally, we characterized an XY system on LG7 in Astatoreochromis alluaudi. This report brings the number of distinct sex-chromosome systems in haplochromine cichlids to at least 13, and highlights the dynamic evolution of sex determination and sex chromosomes in this young lineage. Full article

The black soldier fly, Hermetia illucens (BSF, Diptera: Stratiomyidae) is an insect with high protein value and a potential feed agent for animals aimed for human consumption. The growth parameters of BSF larvae reared on four substrates—restaurant-waste, fruit-waste, fish-waste, and commercial tilapia food—for 41 days before processing for inclusion into Oreochromis niloticus (Perciformes: Cichlidae, Nile tilapia) commercial fry diets at 30% (70:30) were determined. On fly larvae, the food substrate based on restaurant waste yielded the greatest larval weight and length. BSF larvae fed a fish-waste diet showed the shortest developmental time. The fruit-waste diet induced the lowest weight and length in the fly larvae/pre-pupae (immature stage). The pre-pupal protein values were similar to commercial food. On fry-fish, the diets with pre-pupae grown on fish waste showed the greatest yields regarding weight (biomass), length, and nutritional content. These results suggest the BSF has the potential to be used in fish feed and provides an alternative for commercial cultivation. Full article