Habitat Diversity Mitigates the Impacts of Human Pressure on Stream Biodiversity.

Recent decades have witnessed substantial changes in freshwater biodiversity worldwide. Although research has shown that freshwater biodiversity can be shaped by changes in habitat diversity and human-induced pressure, the potentials for interaction between these drivers and freshwater biodiversity at large spatial extents remain unclear. To address these issues, we employed a spatially extensive multitrophic fish and insect database from 3323 stream sites across the United States, to investigate the ability of habitat diversity to modulate the effect of human pressure on the richness and abundance of fish and insects. We found evidence that high levels of habitat diversity were associated with increased richness and abundance of fish and insects (including whole-assemblage and individual trophic guilds). We also show that the effects of human pressure on the richness and abundance of fish and insects tend to become positive at high levels of habitat diversity. Where habitat diversity is low, human pressure strongly reduces insect richness and abundance, whereas these reductions are attenuated at high levels of habitat diversity. Structural equation modeling revealed that human pressure reduced habitat diversity, indirectly negatively affecting the richness and abundance of fish and insects. These findings illustrate that, in addition to promoting greater fish and insect biodiversity, habitat diversity may mitigate the deleterious effects of human pressures on these two stream assemblages. Overall, our study suggests that maintaining high levels of habitat diversity is a useful way to protect freshwater biodiversity from ongoing increases in human pressure. However, if human pressures continue to increase, this will reduce habitat diversity, further threatening stream assemblages.

A New Species of Anacanthorus (Dactylogyridae, Anacanthorinae) Parasitizing Gills of Hoplias aff. malabaricus (Bloch, 1794) (Characiformes, Erythrinidae) from the Caatinga Domain.

INTRODUCTION: Anacanthorus silvoi n. sp. (Dactylogyridae, Anacanthorinae) is described from the gills of Hoplias aff. malabaricus (Bloch, 1794) from the Salgado River, Ceará state, Brazil. MATERIALS AND METHODS: The monogeneans were affixed onto slides using Gray and Wess's medium for examination of their sclerotized structures. For analysis of internal organs, a single specimen was preserved in 5% formalin, stained with Gomori's trichrome, and mounted in Gray and Wess's medium. RESULTS: Anacanthorus silvoi n. sp. is characterized by having a short broad tube MCO with a medial constriction (i.e., MCO with distal region wider than the proximal region, and flexed lateral flap in the distal region in A. cururutuiensis and a MCO with a small projection in the form of a hook in the distal region in A. siphonocommus). CONCLUSIONS: The present study corroborates previous studies that the absence of an accessory piece is a characteristic shared by all Anacanthorus members parasites of Erythrinidae.

Transition from endogenous to exogenous feeding in longfin yellowtail Seriola rivoliana larvae under simultaneous effects of daily temperature fluctuation and rotifer Brachionus rotundiformis enrichment.

Temperature and nutrition are suggested as the primary factors affecting larval survival during the transition from endogenous to exogenous feeding in fish. However, little is known about its simultaneous impact during this period. In this study, Seriola rivoliana eggs were subjected to a constant 24 °C (CTE) and a daily temperature fluctuation (DTF) between 22.8 and 25.2 °C until oil droplet exhaustion (5.5 days after hatching). On the other hand, marine fish larvae mostly rely on live feed, with certain nutritional deficiencies such as poor long-chain fatty acids. Thus, rotifer Brachionus rotundiformis enrichment was simultaneously evaluated with temperature using three enrichment diets: Ori-green, S.presso, and a Domestic emulsion. For this purpose, the five experimental groups were established in triplicate using six 100-L tanks with three 10-L containers inside (18 experimental units in total). One hundred eggs were incubated, using a green water system, and 10 rotifers mL-1 were offered at mouth opening. After oil droplet exhaustion, survival was only affected by temperature (P < 0.01), being higher at DTF compared to CTE. At the same stage, Domestic emulsion resulted in bigger larvae than Ori-green. In a further assay at 3.7 DAH, the relative expression of the trypsin gene was higher at Domestic emulsion compared to S.presso and Ori-green. This study indicates that daily temperature fluctuation can improve larval performance and low levels of EPA and DHA in Domestic emulsion enriched rotifers were not critical for Seriola rivoliana at first feeding.

Highly divergent satellitomes of two barley species of agronomic importance, Hordeum chilense and H. vulgare.

In this paper, we have performed an in-depth study of the complete set of the satellite DNA (satDNA) families (i.e. the satellitomes) in the genome of two barley species of agronomic value in a breeding framework, H. chilense (H1 and H7 accessions) and H. vulgare (H106 accession), which can be useful tools for studying chromosome associations during meiosis. The study has led to the analysis of a total of 18 satDNA families in H. vulgare, 25 satDNA families in H. chilense (accession H1) and 27 satDNA families in H. chilense (accession H7) that constitute 46 different satDNA families forming 36 homology groups. Our study highlights different important contributions of evolutionary and applied interests. Thus, both barley species show very divergent satDNA profiles, which could be partly explained by the differential effects of domestication versus wildlife. Divergence derives from the differential amplification of different common ancestral satellites and the emergence of new satellites in H. chilense, usually from pre-existing ones but also random sequences. There are also differences between the two H. chilense accessions, which support genetically distinct groups. The fluorescence in situ hybridization (FISH) patterns of some satDNAs yield distinctive genetic markers for the identification of specific H. chilense or H. vulgare chromosomes. Some of the satellites have peculiar structures or are related to transposable elements which provide information about their origin and expansion. Among these, we discuss the existence of different (peri)centromeric satellites that supply this region with some plasticity important for centromere evolution. These peri(centromeric) satDNAs and the set of subtelomeric satDNAs (a total of 38 different families) are analyzed in the framework of breeding as the high diversity found in the subtelomeric regions might support their putative implication in chromosome recognition and pairing during meiosis, a key point in the production of addition/substitution lines and hybrids.

A molecular approach to identify parrotfish (Sparisoma) species during early ontogeny.

Sparisoma species (parrotfish) comprise an important functional group contributing to coral-reef resilience. The morphological diagnostic characteristics for species identification are clearly described for adult forms but not for the early stages. Consequently, many taxonomical listings of Sparisoma larvae are restricted to the genus level. The aims of this study are to determine whether the morphological and molecular identification techniques are useful to assign the species taxonomic level to Sparisoma larvae occurring in the Gulf of Mexico and whether there is a set of diagnostic features that could be used to discriminate between species in larvae of different developmental stages. Morphological assignment of Sparisoma was performed based on morphological and meristic features for 30 larvae collected in the Gulf of Mexico from late August to mid-September 2015. To corroborate and complement the morphological assignments, molecular identification was carried out using DNA sequences from regions of two mitochondrial genes, mitochondrial cytochrome oxidase I (mtDNA COI) and mitochondrial 16S rRNA (mtDNA 16S rRNA). COI and 16S gene trees for Sparisoma and related fish taxa were constructed using sequences available in the NCBI (National Center for Biotechnology Information) GenBank and BOLD (Barcode of Life Data) databases. Two morphotypes were identified based on morphology, but no diagnostic characteristics for species discrimination were found. Molecular identification, in contrast, successfully discriminated four early development stages of Sparisoma atomarium, three stages of Sparisoma radians, and two stages of Sparisoma chrysopterum and Sparisoma aurofrenatum, therefore demonstrating the successful and necessary application of molecular taxonomic approaches for species-level identifications of Sparisoma larvae.

Gross, histologic, and ultrastructural features of iridophoromas in Siamese fighting fish (Betta splendens).

Pigment-containing and light-reflecting cell neoplasms, generically termed chromatophoromas, affect fish, reptiles, and amphibians. Chromatophoromas of light-reflecting cells are named iridophoromas. In this study, we aimed to describe the gross, histologic, and ultrastructural findings of 71 cases of iridophoromas in farmed Siamese fighting fish (Betta splendens). Macroscopically, iridophoromas appeared as whitish, gray, or black friable masses or plaques in the fin, trunk/tail, or head of the fish. Forty-five tumors (63%) were malignant and invaded the adjacent skeletal muscle and/or metastasized to other organs, whereas 26 (37%) tumors were restricted only to the skin, but due to the cytologic similarity to the malignant counterpart, we were not able to classify them as malignant or benign. Sixty-five (91%) tumors were classified as iridophoromas, whereas 6 (8%) were diagnosed as mixed chromatophoromas. Despite immunolabeling for PNL-2, melan A, or S-100 failing to demonstrate antigen expression, ultrastructural analysis identified light-reflecting neoplastic cells, unequivocally confirming iridophoromas as the predominant tumor. The high incidence of iridophoromas in Siamese fighting fish from the same breeding facility, coupled with a higher occurrence in royal blue and fancy copper color patterns and in young males, suggests a potential genetic/hereditary factor in the tumorigenesis of these neoplasms.

Integrative morphological, cytogenetic and molecular characterization of the Andean climbing catfish Astroblepus mindoensis (Regan, 1916) (Siluriformes:Astroblepidae).

Astroblepus species, commonly known as Andean climbing catfish, exhibit a unique challenge in species delimitation, leading to ongoing taxonomic debates. Here we report data on Astroblepus mindoensis, a vulnerable species endemic to Ecuador, obtained by an integrative approach that includes cytogenetic analysis, molecular identification of the specimens, and recording of morphological and morphometric characters useful for species diagnosis. Thus, this study aimed to associate the karyotype data of the specimens analyzed with morphological and molecular characters, improving and expanding the existing taxonomic information, thus contributing to the systematics of the species. Our morphology results, unlike Regan's original description, which is brief and ambiguous, provide a more detailed morphometric and meristic description. Molecular phylogenetic reconstruction and genetic distance based on a fragment of the cytochrome c oxidase subunit I (COI) showed that our samples constitute a well-supported and monophyletic clade within the A. grixalvii species complex. The cytogenetic analysis identified distinct chromosomal markers, including a single cluster of major ribosomal genes (on chromosome pair 3) and of minor ribosomal genes (on chromosome pair 12) with their localization differing from those reported in other Astroblepus species analyzed. Additionally, the presence of a heteromorphic chromosome pair in males suggests the presence of an XX/XY sex-determination system that has not been identified in other congeneric species. Further investigation is necessary to determine if these chromosomes are associated with the accumulation of repeated sequences, as typically occurs with sex chromosomes, and to assess their presence in other species of the genus.

Alobophora sandrae n. gen. n. sp. (Digenea: Caballerotrematidae) infecting Arapaima gigas sensu lato (Osteoglossiformes: Arapaimidae) with a revision of Caballerotrema, key to Caballerotrematidae, and updated phylogeny.

We propose and describe Alobophora sandrae Cajiao-Mora & Bullard n. gen., n. sp. (Digenea: Caballerotrematidae) for specimens we collected from arapaima, Arapaima gigas sensu lato (Osteoglossiformes: Arapaimidae) in the Amazon River near Leticia, Colombia. Alobophora differs from Caballerotrema Prudhoe, 1960 by lacking head collar projections and by having clustered corner spines and a narrow head collar (4-5× wider than pharynx), whereas Caballerotrema has head collar projections, lacks clustered corner spines, and has a broad head collar (7-8× wider than pharynx). We reassign Caballerotrema annulatum (Diesing, 1850) Ostrowski de Núñez & Sattmann, 2002 to the new genus, as Alobophora annulata (Diesing, 1850) Cajiao-Mora and Bullard n. comb., and provide a supplemental description of Caballerotrema brasiliense Prudhoe, 1960 based on specimens we collected from arapaima. We also examined the holotype and a paratype of Caballerotrema piscicola (Stunkard, 1960) Kostadinova & Gibson, 2001 and concluded that C. piscicola is a junior subjective synonym of C. brasiliense. Our 28S phylogeny recovered A. sandrae sister to A. annulata, with that clade sister to a clade comprising C. brasiliense and an innominate species of Caballerotrema. Caballerotrematidae was recovered sister to Echinostomatidae. We also provide a dichotomous key to caballerotrematids based on head collar projections, corner spine arrangement, proportional pharynx and head collar breadth, testes shape and arrangement, body surface spine shape and distribution, vitellarium distribution, and abundance of prostatic cells.

Title: Alobophora sandrae n. gen. n. sp. (Digenea : Caballerotrematidae) infectant Arapaima gigas sensu lato (Osteoglossiformes : Arapaimidae) avec une révision de Caballerotrema, une clé des Caballerotrematidae et une phylogénie mise à jour. Abstract: Nous proposons et décrivons Alobophora sandrae Cajiao-Mora & Bullard n. gen., n. sp. (Digenea : Caballerotrematidae) pour les spécimens que nous avons collectés chez l'arapaïma, Arapaima gigas sensu lato (Osteoglossiformes : Arapaimidae) dans le fleuve Amazone près de Leticia (Colombie). Alobophora diffère de Caballerotrema Prudhoe, 1960 par l'absence de projections du collier céphalique et par la présence d'épines angulaires groupées et d'un collier céphalique étroit (4 à 5 fois plus large que le pharynx), tandis que Caballerotrema présente des projections du collier céphalique, n'a pas d'épines angulaires groupées et a un collier céphalique large (7 à 8 fois plus large que le pharynx). Nous réaffectons Caballerotrema annulatum (Diesing, 1850) Ostrowski de Núñez & Sattmann, 2002 au nouveau genre, sous le nom d'Alobophora annulata (Diesing, 1850) Cajiao-Mora et Bullard n. comb., et fournissons une description supplémentaire de Caballerotrema brasiliense Prudhoe, 1960 basée sur des spécimens que nous avons collectés sur des arapaïmas. Nous avons également examiné l'holotype et un paratype de Caballerotrema piscicola (Stunkard, 1960) Kostadinova & Gibson, 2001 et avons conclu que C. piscicola est un synonyme subjectif junior de C. brasiliense. Notre phylogénie 28S a trouvé A. sandrae groupe-frère d'A. annulata, avec ce clade frère d'un clade comprenant C. brasiliense et une espèce non nommée de Caballerotrema. Les Caballerotrematidae ont été trouvés comme groupe-frère des Echinostomatidae. Nous fournissons également une clé dichotomique des Caballerotrematidae basée sur les projections du collier de la tête, la disposition des épines d'angle, la largeur proportionnelle du pharynx et du collier de la tête, la forme et la disposition des testicules, la forme et la distribution des épines de la surface du corps, la distribution du vitellarium et l'abondance des cellules prostatiques.

Challenges and solutions in FISH for formalin-fixed paraffin-embedded tissue: A scoping review.

Fluorescence in situ hybridization (FISH) has revolutionized molecular cytogenetic analysis since the 1980s, enabling precise localization of DNA sequences in cells and tissues. Despite its relevance, applying FISH to formalin-fixed paraffin-embedded (FFPE) tissue samples encounters significant technical challenges. This review addresses the main issues encountered in this context, such as inadequate fixation, contamination, block and slide age, inadequate pretreatment, and FISH technique. Proposed solutions include optimized pretreatment protocols, monitoring of blockage, careful selection of probes, and thorough analysis of results. Implementing good laboratory practices and quality control strategies are essential to ensure reliable results. Additionally, the use of emerging technologies such as artificial intelligence and digital pathology offers new perspectives for improving the efficiency and accuracy of FISH in FFPE samples. This review highlights the importance of a careful and personalized approach to overcome the technical challenges associated with FISH in FFPE samples, strengthening its role in research and clinical diagnosis. RESEARCH HIGHLIGHTS: Few FISH studies on FFPE: The scarcity of studies specifically addressing FISH applications in FFPE tissues highlights a critical gap in the literature. Troubleshooting FISH in FFPE tissues: Identifying and addressing common challenges in FISH techniques when applied to FFPE samples, such as signal quality and hybridization efficiency. Critical aspects of FISH technique: Discuss the main technical considerations crucial for successful FISH in FFPE tissues, including sample preparation, probe selection, and protocol optimization.

Coping with collapse: Functional robustness of coral-reef fish network to simulated cascade extinction.

Human activities and climate change have accelerated species losses and degradation of ecosystems to unprecedented levels. Both theoretical and empirical evidence suggest that extinction cascades contribute substantially to global species loss. The effects of extinction cascades can ripple across levels of ecological organization, causing not only the secondary loss of taxonomic diversity but also functional diversity erosion. Here, we take a step forward in coextinction analysis by estimating the functional robustness of reef fish communities to species loss. We built a tripartite network with nodes and links based on a model output predicting reef fish occupancy (113 species) as a function of coral and turf algae cover in Southwestern Atlantic reefs. This network comprised coral species, coral-associated fish (site occupancy directly related to coral cover), and co-occurring fish (occupancy indirectly related to coral cover). We used attack-tolerance curves and estimated network robustness (R) to quantify the cascading loss of reef fish taxonomic and functional diversity along three scenarios of coral species loss: degree centrality (removing first corals with more coral-associated fish), bleaching vulnerability and post-bleaching mortality (most vulnerable removed first), and random removal. Degree centrality produced the greatest losses (lowest R) in comparison with other scenarios. In this scenario, while functional diversity was robust to the direct loss of coral-associated fish (R = 0.85), the taxonomic diversity was not robust to coral loss (R = 0.54). Both taxonomic and functional diversity showed low robustness to indirect fish extinctions (R = 0.31 and R = 0.57, respectively). Projections of 100% coral species loss caused a reduction of 69% of the regional trait space area. The effects of coral loss in Southwestern Atlantic reefs went beyond the direct coral-fish relationships. Ever-growing human impacts on reef ecosystems can cause extinction cascades with detrimental consequences for fish assemblages that benefit from corals.

First record of the rare tubeshoulder Holtbyrnia anomala Krefft 1980 (Teleostei, Platytroctidae) in the southwest Atlantic.

Holtbyrnia anomala is a bathypelagic platytroctid widely distributed in the Atlantic Ocean. In this contribution, we report, for the first time, the occurrence of this species in the tropical southwest Atlantic. A single specimen was collected in 2000 on the continental slope off Rio de Janeiro, Brazil, at an average depth of 1158 m. This report also represents the first record of Holtbyrnia anomala in the Brazilian Economic Exclusive Zone.

Bleomycin-induced chromosomal aberrations in Epstein-Barr virus-transformed human lymphoblastoid cells.

We have evaluated the induction of complete (i.e., without open ends) and incomplete (i.e., with non-rejoined or open ends) chromosomal aberrations by the radiomimetic antibiotic bleomycin (BLM) in human lymphoblastoid cells immortalized with the Epstein-Barr virus (EBV). An EBV-induced lymphoblastoid cell line (T-37) was exposed to BLM (10-200 µg/mL) for 2 h at 37ºC, and chromosomal aberrations were analyzed 24 h after treatment, using PNA-FISH with pan-telomeric and pan-centromeric probes. Both complete (multicentrics, rings, compound acentric fragments, and interstitial deletions) and incomplete (incomplete chromosomes or IC, and terminal acentric fragments or TAF) chromosomal aberrations increased significantly in BLM-exposed cells, although the concentration-response relationship was non-linear. Of the acentric fragments (ace) induced by BLM, 40 % were compound fragments (CF, ace +/+). TAF (ace, +/-) and interstitial fragments (IAF, ace -/-) were induced at similar frequencies (30 %). 230 ICE were induced by BLM, of which 52 % were IC and 48 % TAF. The average ratio between total incomplete chromosome elements (ICE) and multicentrics was 1.52. These findings suggest that human lymphoblastoid cells exhibit less repair capacity than human lymphocytes, with respect to BLM-induced ICE, and that chromosomal incompleteness is a common event following exposure of these cells to BLM.

Variability of Bile Baseline Excitation-emission Fluorescence of Two Tropical Freshwater Fish Species.

The quantification of pollutant metabolites in fish bile is an efficient approach to xenobiotic pollution monitoring in freshwaters since these measurements directly address exposure. Fluorescence excitation-emission matrix spectroscopy (EEMS) has demonstrated to be a highly specific and cost-effective technique for polycyclic aromatic hydrocarbon (PAH) and PAH-metabolite identification and quantification. EEMS ability to quantify these compounds strongly depends on the intensity and variability of the bile baseline fluorescence (BBF). We found large differences in BBF among Aequidens metae (AME) individuals and of these with Piaractus orinoquensis (PIO). Moreover, BBF was large enough that solvent dilutions of over 1:400 were needed to avoid inner filter effects. We used parallel factor analysis (PARAFAC) to model the intra- and inter-species BBF variability. PARAFAC successfully decomposed the EEMS set into three fluorophores present in all samples, although in concentrations spreading over ~ 3 orders of magnitude. One of the factors was identified as tryptophan. Tryptophan and Factor 2 were covariant and much more abundant in AME than in PIO, while Factor 3 was ~ 6 times more abundant in PIO than in AME. Also, tryptophan was ~ 10x more abundant in AME specimens immediately caught in rivers than in their laboratory-adapted peers. The PARAFAC decomposition effectiveness was confirmed by the positive proportionality of scores to dilution ratios. A large inner filter indicates that Factor 2 is as strong a light absorber as tryptophan. Our results stress the need to include bile matrix variable components for the detection and quantification of pollutant metabolites using PARAFAC.

Effects of hypoxia on the reproductive endocrine axis of the pejerrey (Odontesthes bonariensis).

Recently, hypoxic areas have been identified in water bodies of the Pampas region due to human activity. The objective of this work was to study the effect of low concentrations of dissolved oxygen (hypoxia) on the reproductive endocrine axis of a pampas fish (Odontesthes bonariensis). Groups of 8 males and 8 females were subjected to severe hypoxia (2-3 mg l-1) and normoxia (7-9 mg l-1) in 3000 l tanks by duplicate during the reproductive season (spring). After 21 days, 4 males and 4 females from each tank were sacrificed, and blood was drawn to measure estradiol (E2) and testosterone (T). The brain, pituitary gland and a portion of the gonads were extracted and processed to measure the expression of: gnrh1, cyp19a1b, fshß, lhß, fshr, lhcgr and cyp19a1a. From the second experimental week, no spawning was found in the hypoxic females, while at the end of the treatment period no male released sperm. Fish under hypoxic conditions showed signs of gonadal regression, reduction of GSI and plasma levels of sex steroids. Furthermore, the expression of gnrh1 in both sexes, cyp19a1b and fshr in males and only fshß and cyp19a1a in females decreased in comparison with normoxic fish. After 40 days under normal conditions, signs of reproductive recovery were observed in the treated fish. The results obtained demonstrated that hypoxia generated an inhibition of some components of the pejerrey's reproductive endocrine axis, but the effect was reversible.

Satellite DNAs and the evolution of the multiple X1X2Y sex chromosomes in the wolf fish Hoplias malabaricus (Teleostei; Characiformes).

Multiple sex chromosomes usually arise from chromosomal rearrangements which involve ancestral sex chromosomes. There is a fundamental condition to be met for their long-term fixation: the meiosis must function, leading to the stability of the emerged system, mainly concerning the segregation of the sex multivalent. Here, we sought to analyze the degree of differentiation and meiotic pairing properties in the selected fish multiple sex chromosome system present in the wolf-fish Hoplias malabaricus (HMA). This species complex encompasses seven known karyotype forms (karyomorphs) where the karyomorph C (HMA-C) exhibits a nascent XY sex chromosomes from which the multiple X1X2Y system evolved in karyomorph HMA-D via a Y-autosome fusion. We combined genomic and cytogenetic approaches to analyze the satellite DNA (satDNA) content in the genome of HMA-D karyomorph and to investigate its potential contribution to X1X2Y sex chromosome differentiation. We revealed 56 satDNA monomers of which the majority was AT-rich and with repeat units longer than 100 bp. Seven out of 18 satDNA families chosen for chromosomal mapping by fluorescence in situ hybridization (FISH) formed detectable accumulation in at least one of the three sex chromosomes (X1, X2 and neo-Y). Nine satDNA monomers showed only two hybridization signals limited to HMA-D autosomes, and the two remaining ones provided no visible FISH signals. Out of seven satDNAs located on the HMA-D sex chromosomes, five mapped also to XY chromosomes of HMA-C. We showed that after the autosome-Y fusion event, the neo-Y chromosome has not substantially accumulated or eliminated satDNA sequences except for minor changes in the centromere-proximal region. Finally, based on the obtained FISHpatterns, we speculate on the possible contribution of satDNA to sex trivalent pairing and segregation.

Expression and regulation of the CXCL9-11 chemokines and CXCR3 receptor in Atlantic salmon (Salmo salar).

Chemokines are cytokines that mediate leukocyte traffic between the lymphoid organs, the bloodstream, and the site of tissue damage, which is essential for an efficient immune response. In particular, the gamma interferon (IFN- γ) inducible chemokines CXCL9, CXCL10, and CXCL11, and their receptor CXCR3, are involved in T cell and macrophage recruitment to the site of infection. The nature and function of these chemokines and their receptor are well-known in mammals, but further research is needed to achieve a similar level of understanding in fish immunity. Thus, in this study, we seek to identify the genes encoding the components of the Atlantic salmon (Salmo salar) CXCL9, CXCL10, CXCL11/CXCR3 axis (CXCL9-11/CXCR3), predict the protein structure from the amino acid sequence, and explore the regulation of gene expression as well as the response of these chemokines and their receptor to viral infections. The cxcl9, cxcl10, cxcl11, and cxcr3 gene sequences were retrieved from the databases, and the phylogenetic analysis was conducted to determine the evolutionary relationships. The study revealed an interesting pattern of clustering and conservation among fish and mammalian species. The salmon chemokine sequences clustered with orthologs from other fish species, while the mammalian sequences formed separate clades. This indicates a divergent evolution of chemokines between mammals and fish, possibly due to different evolutionary pressures. While the structural analysis of the chemokines and the CXCR3 receptor showed the conservation of critical motifs and domains, suggesting preserved functions and stability throughout evolution. Regarding the regulation of gene expression, some components of the CXCL9-11/CXCR3 axis are induced by recombinant gamma interferon (rIFN-γ) and by Infectious pancreatic necrosis virus (IPNV) infection in Atlantic salmon cells. Further studies are needed to explore the role of Atlantic salmon CXCL9-11 chemokines in regulating immune cell migration and endothelial activation, as seen in mammals. To the best of our knowledge, there have been no functional studies of chemokines to understand these effects in Atlantic salmon.

Integrative taxonomy reveals a new species of Characidium (Characiformes: Crenuchidae) shared by tributaries of upper Tapajós and Xingu river basins, Brazil.

A new species of Characidium shared by adjacent tributaries of the upper portions of the Tapajós and Xingu river basins is described. Characidium varii, new species, can be distinguished from the congeners by having distinctly speckled pattern of colouration, including dark blotches on cheek and ventral surface of head, by having conspicuous dark marks on fins, along with a single row of dentary teeth, isthmus completely covered by scales, 14 circumpeduncular scales, and swimbladder reduced. Molecular data reinforce the validation of the new species. The distribution of C. varii supports the hypothesis of the existence of a faunistic mixing between Tapajós and Xingu river basins, corresponding to the region of the Serra do Cachimbo and surrounding areas, previously proposed in the literature.

Microbiota diversity of three Brazilian native fishes during ice and frozen storage.

This study aimed to assess the bacterial microbiota involved in the spoilage of pacu (Piaractus mesopotamics), patinga (female Piaractus mesopotamics x male Piaractus brachypomus), and tambacu (female Colossoma macropomum × male Piaractus mesopotamics) during ice and frozen storage. Changes in the microbiota of three fish species (N = 22) during storage were studied through 16S rRNA amplicon-based sequencing and correlated with volatile organic compounds (VOCs) and metabolites assessed by nuclear magnetic resonance (NMR). Storage conditions (time and temperature) affected the microbiota diversity in all fish samples. Fish microbiota comprised mainly of Pseudomonas sp., Brochothrix sp., Acinetobacter sp., Bacillus sp., Lactiplantibacillus sp., Kocuria sp., and Enterococcus sp. The relative abundance of Kocuria, P. fragi, L. plantarum, Enterococcus, and Acinetobacter was positively correlated with the metabolic pathways of ether lipid metabolism while B. thermosphacta and P. fragi were correlated with metabolic pathways involved in amino acid metabolism. P. fragi was the most prevalent spoilage bacteria in both storage conditions (ice and frozen), followed by B. thermosphacta. Moreover, the relative abundance of identified Bacillus strains in fish samples stored in ice was positively correlated with the production of VOCs (1-hexanol, nonanal, octenol, and 2-ethyl-1-hexanol) associated with off-flavors. 1H NMR analysis confirmed that amino acids, acetic acid, and ATP degradation products increase over (ice) storage, and therefore considered chemical spoilage index of fish fillets.

Effect of temperature on the embryonic and larvae development of discus fish Symphysodon aequifasciatus and time of first feeding.

This study aimed to analyze the influence of different temperatures on the embryonic and larval development of discus fish Symphysodon aequifasciatus and determine the time required for the beginning of exogenous feeding. Eggs and larvae were obtained from natural spawns and distributed in five treatments: 24.0, 26.0, 28.0, 30.0, and 32.0 °C. To assess the developmental stages and embryonic structures, samples were taken at regular intervals and checked under an optical microscope. At the end of the experimental period, statistical analysis was performed, followed by Tukey's test. As a result, it was possible to observe the significant effects of temperature on the variables. It was noted that the temperature accelerated the embryonic and larval development of the discus and also contributed to a reduction in the time between the incubation period and the feeding transition. It was also noted that the incubation of eggs and larvae at a temperature of 24.0 °C can cause damage to embryos, such as malformation of the body as well as anomalies in the circulatory system.