Light diffraction by sarcomeres produces iridescence in transmission in the transparent ghost catfish.

Despite the elaborate varieties of iridescent colors in biological species, most of them are reflective. Here we show the rainbow-like structural colors found in the ghost catfish (Kryptopterus vitreolus), which exist only in transmission. The fish shows flickering iridescence throughout the transparent body. The iridescence originates from the collective diffraction of light after passing through the periodic band structures of the sarcomeres inside the tightly stacked myofibril sheets, and the muscle fibers thus work as transmission gratings. The length of the sarcomeres varies from ~1 µm from the body neutral plane near the skeleton to ~2 µm next to the skin, and the iridescence of a live fish mainly results from the longer sarcomeres. The length of the sarcomere changes by ~80 nm as it relaxes and contracts, and the fish shows a quickly blinking dynamic diffraction pattern as it swims. While similar diffraction colors are also observed in thin slices of muscles from non-transparent species such as the white crucian carps, a transparent skin is required indeed to have such iridescence in live species. The ghost catfish skin is of a plywood structure of collagen fibrils, which allows more than 90% of the incident light to pass directly into the muscles and the diffracted light to exit the body. Our findings could also potentially explain the iridescence in other transparent aquatic species, including the eel larvae (Leptocephalus) and the icefishes (Salangidae).

Genome-wide sequence divergence of satellite DNA could underlie meiotic failure in male hybrids of bighead catfish and North African catfish (Clarias, Clariidae).

Hybrid sterility, a hallmark of postzygotic isolation, arises from parental genome divergence disrupting meiosis. While chromosomal incompatibility is often implicated, the underlying mechanisms remain unclear. This study investigated meiotic behavior and genome-wide divergence in bighead catfish (C. macrocephalus), North African catfish (C. gariepinus), and their sterile male hybrids (important in aquaculture). Repetitive DNA analysis using bioinformatics and cytogenetics revealed significant divergence in satellite DNA (satDNA) families between parental species. Notably, one hybrid exhibited successful meiosis and spermatozoa production, suggesting potential variation in sterility expression. Our findings suggest that genome-wide satDNA divergence, rather than chromosome number differences, likely contributes to meiotic failure and male sterility in these catfish hybrids.

Hindering the biofilm of microbial pathogens and cancer cell lines development using silver nanoparticles synthesized by epidermal mucus proteins from Clarias gariepinus.

Scientists know very little about the mechanisms underlying fish skin mucus, despite the fact that it is a component of the immune system. Fish skin mucus is an important component of defence against invasive infections. Recently, Fish skin and its mucus are gaining interest among immunologists. Characterization was done on the obtained silver nanoparticles Ag combined with Clarias gariepinus catfish epidermal mucus proteins (EMP-Ag-NPs) through UV-vis, FTIR, XRD, TEM, and SEM. Ag-NPs ranged in size from 4 to 20 nm, spherical in form and the angles were 38.10°, 44.20°, 64.40°, and 77.20°, Where wavelength change after formation of EMP-Ag-NPs as indicate of dark brown, the broad band recorded at wavelength at 391 nm. Additionally, the antimicrobial, antibiofilm and anticancer activities of EMP-Ag-NPs was assessed. The present results demonstrate high activity against unicellular fungi C. albicans, followed by E. faecalis. Antibiofilm results showed strong activity against both S. aureus and P. aeruginosa pathogens in a dose-dependent manner, without affecting planktonic cell growth. Also, cytotoxicity effect was investigated against normal cells (Vero), breast cancer cells (Mcf7) and hepatic carcinoma (HepG2) cell lines at concentrations (200-6.25 µg/mL) and current results showed highly anticancer effect of Ag-NPs at concentrations 100, 5 and 25 µg/mL exhibited rounding, shrinkage, deformation and granulation of Mcf7 and HepG2 with IC50 19.34 and 31.16 µg/mL respectively while Vero cells appeared rounded at concentration 50 µg/mL and normal shape at concentration 25, 12.5 and 6.25 µg/ml with IC50 35.85 µg/mL. This study evidence the potential efficacy of biologically generated Ag-NPs as a substitute medicinal agent against harmful microorganisms. Furthermore, it highlights their inhibitory effect on cancer cell lines.

Phylogenomics of the narrowly endemic Eurycheilichthys (Siluriformes: Loricariidae): Sympatric species with non-sister relationships suggest mainly allopatric speciation.

Armored catfishes of the genus Eurycheilichthys are endemic to Southern Brazil and Misiones (Argentina) comprising nine species of small size, with a high degree of sympatry and species diversity distributed in two river basins. Here we use new genome-wide data to infer a species phylogeny and test species boundaries for this poorly known group. We estimate 1) the phylogenetic relationships of the species of Eurycheilichthys based on 29,350 loci in 65 individuals of nine species plus outgroups, and 2) the population structure and differentiation based on 43,712 loci and 62 individuals to estimate how geography may have acted on speciation and formation of the sympatric species groups. Analyses support the monophyly of the genus and suggest two species-inclusive clades (East and West) with high support and very recently diverged species. Western clade contains E. limulus (from upper Jacuí River basin) that is sister to Western species of the Taquari-Antas basin plus E. paucidens. The Eastern clade contains E. pantherinus (from Uruguay River basin) sister to the Eastern species of the Taquari-Antas basin E. coryphaenus, plus the central-distributed species E. planus and E. vacariensis, and the more widely-distributed species E. luisae. Eurycheilichthys luisae is not monophyletic and may contain one or more cryptic species or hybrid individuals. A stronger diversity on structure of lineages on the Taquari-Antas, when compared to upper Uruguay and Jacuí River basins, and the fact that most of the sympatrically distributed taxa have non-sister relationships suggest a scenario of mainly allopatric speciation and may indicate a more dynamic landscape with headwater capture events among these tributaries.

Phylogenomics of the leafhopper genus Neoaliturus Distant, 1918 (Hemiptera: Cicadellidae: Deltocephalinae) reveals genetically divergent lineages in the invasive beet leafhopper.

Phylogenomic analysis based on nucleotide sequences of 398 nuclear gene loci for 67 representatives of the leafhopper genus Neoaliturus yielded well-resolved estimates of relationships among species of the genus. Subgenus Neoaliturus (Neoaliturus) is consistently paraphyletic with respect to Neoaliturus (Circulifer). The analysis revealed the presence of at least ten genetically divergent clades among specimens consistent with the previous morphology-based definition of the leafhopper genus "Circulifer" which includes three previously recognized "species complexes." Specimens of the American beet leafhopper, N. tenellus (Baker), collected from the southwestern USA consistently group with one of these clades, comprising specimens from the eastern Mediterranean. Some of the remaining lineages are consistent with ecological differences previously observed among eastern Mediterranean populations and suggest that N. tenellus, as previously defined, comprises multiple monophyletic species, distinguishable by slight morphological differences.

Choline-mediated hepatic lipid homoeostasis in yellow catfish: unravelling choline's lipotropic and methyl donor functions and significance of ire-1α signalling pathway.

Choline plays a crucial role in hepatic lipid homeostasis by acting as a major methyl-group donor. However, despite this well-accepted fact, no study has yet explored how choline's methyl-donor function contributes to preventing hepatic lipid dysregulation. Moreover, the potential regulatory role of Ire-1α, an ER-transmembrane transducer for the unfolded protein response (UPRer), in choline-mediated hepatic lipid homeostasis remains unexplored. Thus, this study investigated the mechanism by which choline prevents hepatic lipid dysregulation, focusing on its role as a methyl-donor and the involvement of Ire-1α in this process. To this end, a model animal for lipid metabolism, yellow catfish (Pelteobagrus fulvidraco) were fed two different diets (adequate or deficient choline diets) in vivo for 10 weeks. The key findings of studies are as follows: 1. Dietary choline, upregulated selected lipolytic and fatty acid ß-oxidation transcripts promoting hepatic lipid homeostasis. 2. Dietary choline ameliorated UPRer and prevented hepatic lipid dysregulation mainly through ire-1α signalling, not perk or atf-6α signalling. 3. Choline inhibited the transcriptional expression level of ire-1α by activating site-specific DNA methylations in the promoter of ire-1α. 4. Choline-mediated ire-1α methylations reduced Ire-1α/Fas interactions, thereby further inhibiting Fas activity and reducing lipid droplet deposition. These results offer a novel insight into the direct and indirect regulation of choline on lipid metabolism genes and suggests a potential crosstalk between ire-1α signalling and choline-deficiency-induced hepatic lipid dysregulation, highlighting the critical contribution of choline as a methyl-donor in maintaining hepatic lipid homeostasis.

Dietary chenodeoxycholic acid attenuates high-fat diet-induced growth retardation, lipid accumulation and bile acid metabolism disorder in the liver of yellow catfish Pelteobagrus fulvidraco.

This experiment was conducted to investigate whether dietary chenodeoxycholic acid (CDCA) could attenuate high-fat (HF) diet-induced growth retardation, lipid accumulation and bile acid (BA) metabolism disorder in the liver of yellow catfish Pelteobagrus fulvidraco. Yellow catfish (initial weight: 4·40 (sem 0·08) g) were fed four diets: the control (105·8 g/kg lipid), HF diet (HF group, 159·6 g/kg lipid), the control supplemented with 0·9 g/kg CDCA (CDCA group) and HF diet supplemented with 0·9 g/kg CDCA (HF + CDCA group). CDCA supplemented in the HF diet significantly improved growth performance and feed utilisation of yellow catfish (P < 0·05). CDCA alleviated HF-induced increment of hepatic lipid and cholesterol contents by down-regulating the expressions of lipogenesis-related genes and proteins and up-regulating the expressions of lipololysis-related genes and proteins. Compared with the control group, CDCA group significantly reduced cholesterol level (P < 0·05). CDCA significantly inhibited BA biosynthesis and changed BA profile by activating farnesoid X receptor (P < 0·05). The contents of CDCA, taurochenodeoxycholic acid and glycochenodeoxycholic acid were significantly increased with the supplementation of CDCA (P < 0·05). HF-induced elevation of cholic acid content was significantly attenuated by the supplementation of CDCA (P < 0·05). Supplementation of CDCA in the control and HF groups could improve the liver antioxidant capacity. This study proved that CDCA could improve growth retardation, lipid accumulation and BA metabolism disorder induced by HF diet, which provided new insight into understanding the physiological functions of BA in fish.

TBK1 upregulates the interferon response against virus by the TBK1-IRF3/7 axis in yellow catfish (Pelteobagrus fulvidraco).

Yellow catfish (Pelteobagrus fulvidraco) is an important economic species of freshwater fish, widely distributed in China. Recently, viral diseases of yellow catfish have been identified in Chian (Hubei province), arising more attention to the viral immunity in P. fulvidraco. Tumor necrosis factor (TNF) receptor-associated factor NF-κB activator (TANK)-binding kinase 1 (TBK1) plays an essential role in IFN production and innate antiviral immunity. In the present study, we characterized the P. fulvidraco TBK1 (PfTBK1) and reported its function in interferon response. The full-length open reading frame (ORF) is 2184 bp encoding a protein with 727 amino acids, which is composed of four conserved domains, including KD, ULD, CCD1, and CCD2, similar to TBK1 in other species. Pftbk1 was widely expressed in all detected tissues by qPCR and was not inducible by the spring viremia of carp virus (SVCV), a single-strand RNA virus. In addition, the cellular distribution indicated that PfTBK1 was only located in the cytoplasm. Moreover, PfTBK1 induced strong IFN promoter activities through the Jak-stat pathway, and PfTBK1 interacted with and significantly phosphorylated IFN regulatory factor 3/7 (IRF3/7) in P. fulvidraco, promoting the nuclear translocation of pfIRF3 and PfIRF7, and PfTBK1 upregulated IFN response by PfTBK1-PfIRF3/7 axis. Above all, PfTBK1 triggered IFN response and strongly inhibited the replication of SVCV in EPC cells through induction of IFN downstream IFN-stimulated genes (ISGs). Summarily, this work reveals that PfTBK1 plays a positive regulatory role in IFN induction through the TBK1-IRF3/7 axis, laying a foundation for further exploring the molecular mechanism of the antiviral process in P. fulvidraco.

Characterization and expression profiles of toll-like receptor genes (TLR2 and TLR5) in immune tissues of hybrid yellow catfish under bacterial infection.

The yellow catfish (Pelteobagrus fulvidraco) is one of the most economically important freshwater species in Asia. However, pathogenic bacterial infections often cause high rates of mortality and economic losses in practical aquaculture. Previous studies in mammals have shown that Toll-like receptor 2 (TLR2) and Toll-like receptor 5 (TLR5) are involved in the recognition of cell wall components such as lipopolysaccharides and flagella of various bacteria, thereby acting as key regulators in the innate immunity response. However, TLR2 and TLR5 in yellow catfish have not been characterized. In the present study, TLR2 and TLR5 were examined through comparative genomic approaches. The gene structure, collinearity, protein spatial structure, and phylogenetic relationships were compared with those in multiple representative vertebrates. Meanwhile, quantitative real-time PCR was conducted to explore transcriptional changes in TLR2 and TLR5 in immune tissues after infection with exogenous A. hydrophila and E. tarda. The results demonstrated the presence of TLR2 and TLR5 in yellow catfish. However, a systematic analysis showed that TLR2 was not associated with the arrangement of diverse neighboring genes. The expression of hybrid yellow catfish TLR2 transcripts in multiple tissues (including liver, spleen, kidney, and intestine) was significantly up-regulated after infection with A. hydrophila and E. tarda, suggesting that hybrid yellow catfish TLR2 and TLR5 may participate in the immune process. Taken together, the results indicate that TLR2 and TLR5 are conserved in terms of evolution and possess significant antibacterial activity as well as regulatory properties in immune-related tissues and thus play key roles in host defense against pathogen invasion.

Molecular characterization, expression analysis and function identification of Pf_IL-12p35, Pf_IL-23p19 and Pf_IL-12p40 genes in yellow catfish (Pelteobagrus fulvidraco).

The interleukin-12 (IL-12) family is a class of heterodimeric cytokines that play crucial roles in pro-inflammatory and pro-stimulatory responses. Although some IL-12 and IL-23 paralogues have been found in fish, their functional activity in fish remains poorly understood. In this study, Pf_IL-12p35a/b, Pf_IL-23p19 and Pf_IL-12p40a/b/c genes were cloned from yellow catfish (Pelteobagrus fulvidraco), four α-helices were found in Pf_IL-12p35a/b and Pf_IL-23p19. The transcripts of these six genes were relatively high in mucus and immune tissues of healthy individuals, and in gill leukocytes. Following Edwardsiella ictaluri infection, Pf_IL-12p35a/b and Pf_IL-23p19 mRNAs were induced in brain and kidney (or head kidney), Pf_IL-12p40a mRNA was induced in gill, and Pf_IL-12p40b/c mRNAs were induced in brain and liver (or skin). The mRNA expression of these genes in PBLs was induced by phytohaemagglutinin (PHA) and polyinosinic-polycytidylic acid (poly I:C), while lipopolysaccharides (LPS) induced the mRNA expression of Pf_IL-12p35a and Pf_IL-12p40b/c in PBLs. After stimulation with recombinant (r) Pf_IL-12 and rPf_IL-23 subunit proteins, either alone or in combination, mRNA expression patterns of genes related to T helper cell development exhibited distinct differences. The results suggest that Pf_IL-12 and Pf_IL-23 subunits may play important roles in regulating immune responses to pathogens and T helper cell development.

Enhancement of autophagy can alleviate oxidative stress, inflammation, and apoptosis induced by ammonia stress in yellow catfish Pelteobagrus fulvidraco.

Ammonia in aquatic environments is toxic to fish, directly impacting their growth performance and development. Activation of autophagy can facilitate intracellular component renewal and enhance an organism's adaptability to adverse environments. Therefore, this study investigates the impact of autophagy on the yellow catfish under acute ammonia stress. In this study, the yellow catfish intraperitoneally injected with 0.9 % sodium chloride were placed with 0 (CON group) and 125 (HA group) mg/L T-AN (Total ammonia nitrogen) dechlorinated water. The yellow catfish intraperitoneally injected with 30 mg/kg fish CQ (Chloroquine, HA + CQ group) and 1.5 mg/kg fish RAPA (rapamycin, HA + RAPA group) were placed in dechlorinated water containing 125 mg/L T-AN. The results showed that activation of autophagy by injecting with RAPA can alleviate oxidative stress (catalase, superoxide dismutase, total antioxidant capacity significantly increased, H2O2 content significantly decreased), and inflammatory response (pro-inflammatory factors TNF-α, MyD88, IL 1-ß gene expression decreased significantly), apoptosis (baxa, Bcl2, Tgf-ß, Smad2, Caspase3, Caspase 9 gene expression decreased significantly) induced by ammonia stress. In addition, activation of autophagy in yellow catfish can enhance ammonia detoxification by promoting the urea cycle and synthesis of glutamine (the mRNA level of CPS Ⅰ, ARG, OTC, ASS, ASL, and GS increased in the HA + RAPA group). The data above demonstrates that activating autophagy can alleviate oxidative stress, inflammatory responses, and cell apoptosis induced by ammonia stress. Therefore, enhancing autophagy is proposed as a potential strategy to mitigate the detrimental impacts of ammonia stress on yellow catfish.

Occurrence and characterization of Proteus mirabilis from infected farmed African catfish in Ogun State, Nigeria.

BACKGROUND: Bacterial pathogens are the causative agents of some of the most serious disease problems in cultured fish causing mortalities and severe economic losses. This study was conducted to determine the occurrence and characterization of Proteus mirabilis from infected farmed African catfish in Ogun State, Nigeria. METHODOLOGY: The bacteria were isolated from diseased farmed African catfish (Clarias gariepinus, n=128) with clinical signs of skin haemorrhages, ulceration, and ascites purposively sampled from farms within three senatorial districts namely Ogun East (OE; n=76), Ogun Central (OC; n=30) and Ogun West (OW; n=22) in Ogun State. The isolates were identified based on morphological characteristics, biochemical tests, and 16S rRNA gene characterisation. The 16S rRNA gene sequences were analysed using BLAST, submitted to the NCBI database, and an accession number was generated. RESULTS: The occurrence of Proteus mirabilis in infected Clarias gariepinus was 13.16%, 25%, and 31.25% in OE, OC, and OW, respectively. A significantly higher incidence was recorded in OW compared to other areas. All the Proteus mirabilis isolates were motile, gram-negative, short rod, non-lactose fermenter bacteria that showed positive catalase reactions, negative oxidase, and positive for methyl-red. The Proteus mirabilis isolates (OP 594726.1) were closely related to isolates from Pakistan, Italy, and India CONCLUSIONS: We conclude that Proteus mirabilis colonises farmed Clarias gariepinus in Ogun State, Nigeria and the identified strain showed an evolutionary relationship with known pathogenic NCBI reference strains from other countries.

Decoding the molecular phylogenetics of ornamental catfishes (siluriformes) of North East India using DNA barcoding approach.

BACKGROUND: Catfishes (order Siluriformes) are among the most diverse and widely distributed fish groups in the world. They are not only used for human consumption but are also a major part of the ornamental fish trade. Being a Biodiversity Hotspot, the North Eastern Region of India is home to a diverse population of ornamental fishes. Catfishes contain a humongous number of species; in this study, the authors have tried to elucidate the phylogenetic relationship of some important ornamental catfishes found in North East India using DNA barcodes. METHODS AND RESULTS: In this study, we have tried to explore the phylogenetic history of 13 species (41 specimens) of ornamental catfishes spanning 12 genera and 9 families of Siluriformes using DNA barcoding. Pairwise genetic distances using Kimura 2-Parameter (K2P) were calculated at intra-specific and inter-specific levels. A Neighbor-Joining tree was constructed to understand the phylogenetic relationship among the nine different catfish families. All the specimens under this study clustered with their respective species under the same family and formed three sub-clades. However, Olyra longicaudata, belonging to the Bagridae family, did not cluster with other species from the same family. In this study, the authors have suggested a revision of the classification of O. longicaudata back to its original family, Olyridae. CONCLUSIONS: In this study, the maximum intraspecific genetic distance of 0.03 and the minimum interspecific genetic distance of 0.14 were observed among the species. Therefore, it is evident that there is a barcoding gap among the species, which helped in the correct identification of the species. Thus, DNA barcoding helped complement the phenetic approach and also revealed a different phylogenetic relationship among the catfishes belonging to the Bagridae family.

Genetic diversity, spatial connectivity, and population structure of Asian silurid catfish Wallago attu (Bloch and Schneider, 1801) in the Ganga River System: insights from mitochondrial DNA analysis.

BACKGROUND: The Ganga River System (GRS) is a biodiversity hotspot, its ecological richness is shaped by a complex geological history. In this study, we examined the genetic diversity, spatial connectivity, and population structure of the Asian Silurid catfish, Wallago attu, across seven tributaries of the GRS. METHODS AND RESULTS: We employed three mitochondrial DNA (mtDNA) regions: cytochrome c oxidase subunit I (COXI), cytochrome b (Cyt b), and control region (CR). Our comprehensive dataset encompassed 2420 bp of mtDNA, derived from 176 W. attu individuals across 19 sampling sites within the seven rivers of GRS. Our findings revealed high gene diversity (Hd:0.99) within W. attu populations. Analysis of Molecular Variance (AMOVA) highlighted that maximum genetic variations were attributed within the populations, and the observed genetic differentiation among the seven populations of W. attu ranged from low to moderate. Network analysis uncovered the presence of three distinct genetic clades, showing no specific association with seven studied rivers. Bayesian skyline plots provided insights into the demographic history of W. attu, suggesting a recent population expansion estimated to have occurred approximately 0.04 million years ago (mya) during the Pleistocene epoch. CONCLUSIONS: These results significantly enhance our understanding of the genetic diversity and spatial connectivity of W. attu, serving as a vital foundation for developing informed conservation strategies and the sustainable management of this economically valuable resource within the Ganga River System.

Complete mitochondrial genome of critically endangered catfish Hemibagrus punctatus (Jerdon, 1849) and comparative analysis for insights into the phylogeny of hemibagrids through mitogenomic approach.

BACKGROUND: Hemibagrus punctatus (Jerdon, 1849) is a critically endangered bagrid catfish endemic to the Western Ghats of India, whose population is declining due to anthropogenic activities. The current study aims to compare the mitogenome of H. punctatus with that of other Bagrid catfishes and provide insights into their evolutionary relationships. METHODS AND RESULTS: Samples were collected from Hemmige Karnataka, India. In the present study, the mitogenome of H. punctatus was successfully assembled, and its phylogenetic relationships with other Bagridae species were studied. The total genomic DNA of samples was extracted following the phenol-chloroform isoamyl alcohol method. Samples were sequenced, and the Illumina paired-end reads were assembled to a contig length of 16,517 bp. The mitochondrial genome was annotated using MitoFish and MitoAnnotator (Iwasaki et al., 2013). A robust phylogenetic analysis employing NJ (Maximum composite likelihood) and ASAP methods supports the classification of H. punctatus within the Bagridae family, which validates the taxonomic status of this species. In conclusion, this research enriches our understanding of H. punctatus mitogenome, shedding light on its evolutionary dynamics within the Bagridae family and contributing to the broader knowledge of mitochondrial genes in the context of evolutionary biology. CONCLUSIONS: The study's findings contribute to a better understanding of the mitogenome of H. punctatus and provide insights into the evolutionary relationships within other Hemibagrids.

Infection of endemic chub Squalius tenellus with the intestinal tapeworm Caryophyllaeus brachycollis (Cestoda): histopathology and ultrastructural surveys.

The endemic chub Squalius tenellus (Heckel, 1843) was introduced more than 100 years ago to Lake Blidinje (Bosnia-Herzegovina). Only 1 species of enteric helminth was found in a sample of 35 chubs, the tapeworm Caryophyllaeus brachycollis (Janiszewska, 1953). The paper includes histopathological investigation with identification of innate immune cells involved in host reaction and molecular data allowed correct designation of the cestode species. Of 35 specimens of chub examined, 21 (60%) harboured individuals of C. brachycollis and a total of 1619 tapeworms were counted, the intensity of infection ranged from 1 to 390 worms per fish (46.2 ± 15.3, mean ± s.e.). Histopathological and ultrastructural investigations showed strict contact between the worm's body and the epithelia and increase in the number of mucous cells, rodlet cells among the epithelial cells. Within the tunica propria-submucosa, beneath the site of scolex attachment, numerous neutrophils and mast cells were noticed. This is the first study of the occurrence of C. brachycollis in chub from Lake Blidinje and on the response of the innate immune cells of S. tenellus to this tapeworm. Interestingly, in 3 very heavily infected chubs, perforation of the intestinal wall was documented; this is uncommon among cestodes which use fish as a definitive host.

Evolutionary morphology of haptoral anchors in monogenoids (Dactylogyridae) of marine catfish (Siluriformes: Ariidae) from the Atlantic coast of South America.

Exploring the phylogenetic signal of morphological traits using geometric morphometry represents a powerful approach to assess the relative weights of convergence and shared evolutionary history in shaping species' forms. We evaluated the phylogenetic signal in shape and size of ventral and dorsal haptoral anchors of 10 species of monogenoids (Hamatopeduncularia, Chauhanellus and Susanlimocotyle) occurring in marine catfish (Siluriformes: Ariidae) from the Atlantic coast of South America. The phylogenetic relationships among these species were mapped onto the morphospaces of shape and size of dorsal and ventral anchors. Two different tests (squared change-parsimony and Kmult) were applied to establish whether the spatial positions in the phylomorphospace were influenced by phylogenetic relationships. A significant phylogenetic signal was found between anchor form and parasite phylogeny. Allometric effects on anchor shape were non-significant. Phylogenetically distant species on the same host differed markedly in anchor morphology, suggesting little influence of host species on anchor form. A significantly higher level of shape variation among ventral anchors was also found, suggesting that the evolutionary forces shaping ventral anchor morphology may operate with differing intensities or exhibit distinct mechanisms compared to their dorsal counterparts. Our results suggest that phylogenetic relationships were a key driver of changes in shape (but not size) of anchors of monogenoids of South American ariids. However, it seems that the emergence of the digitiform haptor in Hamatopenducularia and in some species of Chauhanellus played an important role in the reduction in anchor size and may cause secondary losses of anchors in other groups of monogenoids.

A reference genome for the Andean cavefish Trichomycterus rosablanca (Siluriformes, Trichomycteridae): Building genomic resources to study evolution in cave environments.

Animals living in caves are of broad relevance to evolutionary biologists interested in understanding the mechanisms underpinning convergent evolution. In the Eastern Andes of Colombia, populations from at least two distinct clades of Trichomycterus catfishes (Siluriformes) independently colonized cave environments and converged in phenotype by losing their eyes and pigmentation. We are pursuing several research questions using genomics to understand the evolutionary forces and molecular mechanisms responsible for repeated morphological changes in this system. As a foundation for such studies, here we describe a diploid, chromosome-scale, long-read reference genome for Trichomycterus rosablanca, a blind, depigmented species endemic to the karstic system of the department of Santander. The nuclear genome comprises 1 Gb in 27 chromosomes, with a 40.0× HiFi long-read genome coverage having an N50 scaffold of 40.4 Mb and N50 contig of 13.1 Mb, with 96.9% (Eukaryota) and 95.4% (Actinopterygii) universal single-copy orthologs (BUSCO). This assembly provides the first reference genome for the speciose genus Trichomycterus, serving as a key resource for research on the genomics of phenotypic evolution.

Hyaluronic acid impacts hematological endpoints and spleen histological features in African catfish (Clarias gariepinus).

Since its identification in the vitreous humour of the eye and laboratory biosynthesis, hyaluronic acid (HA) has been a vital component in several pharmaceutical, nutritional, medicinal, and cosmetic uses. However, little is known about its potential toxicological impacts on aquatic inhabitants. Herein, we investigated the hematological response of Clarias gariepinus to nominal doses of HA. To achieve this objective, 72 adult fish were randomly and evenly distributed into four groups: control, low-dose (0.5 mg/l HA), medium-dose (10 mg/l HA), and high-dose (100 mg/l HA) groups for two weeks each during both the exposure and recovery periods. The findings confirmed presence of anemia, neutrophilia, leucopoenia, lymphopenia, and eosinophilia at the end of exposure to HA. In addition, poikilocytosis and a variety of cytomorphological disturbances were observed. Dose-dependent histological alterations in spleen morphology were observed in the exposed groups. After HA removal from the aquarium for 2 weeks, the groups exposed to the two highest doses still exhibited a notable decline in red blood cell count, hemoglobin concentration, mean corpuscular hemoglobin concentration, and an increase in mean corpuscular volume. Additionally, there was a significant rise in neutrophils, eosinophils, cell alterations, and nuclear abnormalities percentages, along with a decrease in monocytes, coupled with a dose-dependent decrease in lymphocytes. Furthermore, only the highest dose of HA in the recovered groups continued to cause a significant increase in white blood cells. White blood cells remained lower, and the proportion of apoptotic RBCs remained higher in the high-dose group. The persistence of most of the haematological and histological disorders even after recovery period indicates a failure of physiological compensatory mechanisms to overcome the HA-associated problems or insufficient duration of recovery. Thus, these findings encourage the inclusion of this new hazardous agent in the biomonitoring program and provide a specific pattern of hematological profile in HA-challenged fish. Further experiments are highly warranted to explore other toxicological hazards of HA using dose/time window protocols.

Molecular characterization and antibiotics resistance of Aeromonas species isolated from farmed African catfish Clarias gariepinus Burchell, 1822.

BACKGROUND: Aeromonas species are one of the most important etiologies of diseases in fish farms, leading to clinical manifestation and mortality and are associated with public health risks. This study aimed to investigate the prevalence, phenotypic and molecular characteristics of Aeromonas species isolated from farmed Clarias gariepinus using 16 S rRNA sequencing. Additionally, their antibiogram and multiple antibiotic resistance index were determined using a disc diffusion test. RESULTS: A total of 230 Aeromonas strains were isolated from Clarias gariepinus with 40.9% obtained from diseased fish, and 25% isolated from apparently healthy ones. Five different species including Aeromonas caviae, Aeromonas veronii, Aeromonas hydrophila, Aeromonas dhakensis and Aeromonas enteropelogenes were fully identified and genetically characterized. Based on the available literature, this is the first report of Aeromonas enteropelogenes from the study area. The phylogenetic analysis showed genetic heterogeneity and distance within the species and the reference strains. The multiple resistant Aeromonas species were susceptible to ciprofloxacin, gentamycin, and florfenicol. The Aeromonas species' multiple antibiotic resistance index values varied between 0.20 and 0.80 and were isolated from the farms where antibiotics were intensively used. CONCLUSIONS: The diversity of multidrug-resistant Aeromonas species isolated from fish farms is a major threat to fish production giving us more understanding of epidemiology and the multidrug Aeromonas species with a MAR index of greater than 0.2 were isolated from farms where antibiotic use was widespread. As a result, a considerably increased danger of multiple antibiotic resistance spreading to the fish culture environment may impact aquaculture production. Hence there is a need for appropriate and monitored drug usage.