The ocean sunfish (Mola mola, Linnaeus 1758) is a rare, pelagic, cosmopolitan species of negligible commercial interest and subject to unintended bycatch. It is a little-known species, and strandings are rare; we benefited from the stranding of an adult female to conduct a multidisciplinary investigation (toxicology, parasitology, microbiology, pathology) that evaluated multiple findings. Trace element concentrations (in fish tissues and parasites), organic compounds, and microplastics were analyzed. Trace elements were present at low levels in the animal's tissues and at higher concentrations in the parasites (i.e., Zn: 0.056 mg/kg in liver, 0.074 mg/kg in muscle, and 0.322 mg/kg in cestodes). The unexpected detection of pyrethroids was one of the most significant toxicological findings. Microbiological analyses and histological investigations did not yield significant findings correlated to the cause of death. A severe parasitic infection was otherwise detected in the intestine (over 3000 adult cestodes). Morphologic and molecular analyses of helminths identified cestodes belonging to the Triaenophoridae family, and adult trematodes of the family Accacoeliidae. The severe gastrointestinal parasitic burden observed might have plausibly contributed to a state of general weakening. It may have exerted a subtractive effect on essential elements, which ultimately might have contributed to the animal's defedation.
The current study aimed to assess the potential biological and cellular impacts of dietary supplementation with chitosan-flaxseed oil nanocomposite (CFN) in boosting the growth performance indices, digestive enzyme activity, innate immune capacity, economic significance, gene expression, and histopathological alterations in the Nile tilapia exposed to chronic cold stress. Nile tilapia were distributed into six experimental groups, the first three groups were reared under optimum water temperature (25 °C) and fed 0 mg/kg CFN (control), 20 mg/kg CFN or 40 mg/kg -incorporated diets, respectively. However, the other three groups were reared under cold stress conditions (18 °C), and received the same previously mentioned diets, respectively. Growth performance and economic significance analysis were monitored throughout the experiment. Serum and tissue samples were collected after 60 days to evaluate immune indices (lysozyme, nitric oxide, and IgM), glucose, growth hormone (GH), digestive enzymes (amylase and lipase), gene expression (interleukin-8, tumor necrosis factor-alpha, interleukin-1ß, lysozyme-G, lysozyme-C, transforming growth factor-beta, nuclear factor kappa β, myeloperoxidase, and Toll-like receptor-5, and glutathione perioxidase-1), and histopathological changes. A subsequent bacterial challenge with Pseudomonas aeruginosa was carried out, where the clinical disorders and mortalities were monitored. The outcomes showed remarkable declines in various growth metrics, immune variables with dysregulation in the immune-linked genes in fish exposed to chronic cold stress circumstances, compared to fish reared at optimum temperature. Nonetheless, dietary intervention with CFN mitigated the negative impacts induced by cold stress exposure, where the growth, immune indices, and digestive enzymes were notably enhanced in the supplemented groups in relation to the non-supplemented group. The histopathological alterations in the intestine and spleen were also markedly alleviated. Additionally, the expression profiles of both inflammatory cytokines and apoptosis were positively modified. Furthermore, fish resilience to P. aeruginosa infection was triggered, which was evident by the amelioration of the clinical signs and declining mortality rates in CFN-enriched groups. Taken together, CFN is a promising antibacterial dietary additive which promotes the growth, health, and performance of the Nile tilapia.
Pseudomonas aeruginosa represents a considerable public health threat due to its role in severe human infections and a significant economic burden in aquaculture. To assess the prevalence, antibiogram, virulence, and resistance genes, and pathogenicity of P. aeruginosa, 200 Oreochromis niloticus were obtained from commercial fish farms in Port Said, Egypt, and underwent clinical, postmortem, and bacteriological examinations. Herein, the overall prevalence of P. aeruginosa was 20%, and the liver was recognized as the most prominently affected organ. Sequencing of the oprL gene showed that the examined strains shared notable genetic homology with other P. aeruginosa strains from the United Kingdom, USA, India, China, and Japan. The recovered P. aeruginosa strains showed remarkable resistance to tetracycline, amoxicillin, trimethoprim- sulfamethoxazole, amoxicillin-clavulanic acid, gentamycin, erythromycin, and cefotaxime. Notably, a 6.4% imipenem resistance rate was observed among the retrieved strains, indicating a carbapenem-resistant phenotype. PCR ascertained that the most common virulence genes inherited by the recovered strains were the oprL (100%), toxA (94.9%), aprA (47.4%), exoS (38.4%), and phzM (35.9%) genes. A total of 64.1% of the tested P. aeruginosa strains were multidrug-resistant (MDR) to seven classes and harbored the blaTEM, sul1, tetA, blaCTX-M1, and aadA1 genes. Additionally, 6.4% of P. aeruginosa strains were extensively drug-resistant (XDR) to eight classes and harbored the blaTEM, sul1, tetA, blaCTX-M1, blaNDM-1, and aadA1 genes. The pathogenicity assay revealed a positive correlation between isolate virulence and the recorded mortality rate. In summary, the detection of XDR and MDR P. aeruginosa in O. niloticus poses a potential public health concern. These strains commonly harbor the resistance genes tetA, sul1, blaTEM, aadA1, blaCTX-M1, and blaNDM-1, alongside the virulence genes oprL, toxA, aprA, exoS, and phzM.
Streptococcosis caused by Streptococcus iniae is an emerging bacterial disease affecting marine aquaculture worldwide. In recent years, recurrent outbreaks have been observed in golden rabbitfish (Siganus guttatus) cultured in marine cages across the northern and central coastal provinces of Vietnam. This study investigated the epidemiology, pathogenicity, virulence gene profiles and antimicrobial susceptibility of S. iniae associated with disease outbreaks in rabbitfish aquaculture. Between 2023 and 2025, streptococcosis outbreaks were documented across 46 marine cage farms in multiple coastal provinces, with cumulative mortality ranging from 10%-45%, particularly during warm-water periods (28-33°C). Bacteriological examination consistently yielded S. iniae, which was confirmed by biochemical tests and species-specific PCR assays. An experimental challenge demonstrated the high virulence of a representative isolate, with a median lethal dose (LD50) of 6.8 × 103 CFU/fish. Histopathological examination revealed severe multi-organ lesions, including prominent involvement of the brain, kidney, liver, spleen, gills and intestine, consistent with systemic bacterial infection. Molecular screening of virulence-associated genes identified six distinct gene profiles among isolates, indicating substantial genetic heterogeneity within the circulating pathogen population. Several genes, including pdi, simA, cpsB, cpsC, cpsD, pgm, hasA and ydfG were detected in all isolates (100%), whereas others showed marked variability, with prevalence ranging from approximately 17% to 89% among isolates. Antimicrobial susceptibility testing revealed heterogeneous resistance patterns, with high resistance to neomycin (NE) and moderate resistance to trimethoprim-sulfamethoxazole (TRS), while most isolates remained susceptible to tetracyclines (TEs) and β-lactam antibiotics. The widespread occurrence of outbreaks across multiple provinces and over consecutive years suggests sustained circulation of S. iniae within interconnected marine cage aquaculture systems. These findings provide new epidemiological insights into an emerging streptococcal disease affecting rabbitfish aquaculture and highlight the need for improved surveillance and disease management strategies in rapidly expanding marine cage-farming sectors.
Eight species of nemipterid fishes (Nemipteridae) in three genera, collected in coastal waters of Tanzania, are reviewed. Six species were collected during an ecosystem survey conducted by the R/V Dr. Fridtjof Nansen off the coast of Tanzania in 2023 (Nemipterus bipunctatus, N. elaine, N. zysron, Parascolopsis flavimarginatus sp. nov., Scolopsis bimaculata, and S.curite) and two species were found in a museum collection (Parascolopsis akatamae and Scolopsis ghanam). Among these, Nemipterus elaine, previously known only from Mozambique, is recorded from Tanzania for the first time; previous records of N. japonicus and N. randalli from the southwestern Indian Ocean can also be attributed to N. elaine. Parascolopsis akatamae is a new record for Tanzania. Parascolopsis flavimarginatus sp. nov., described from a single specimen, is morphologically similar to P. akatamae and P. eriomma in possessing a high number of gill rakers on the first gill arch (16-19 in these three species, vs. 8-14 gill rakers in other congeners), but can be distinguished by scales on top of head extending forward to above the anterior margin of pupil (vs. scales not extending anterior to a line through middle of eye), and the spinous portion of the dorsal fin being translucent with a broad yellow margin (vs. spinous portion entirely salmon pink, a mixture of salmon pink and yellow, or with a broad reddish margin). Parascolopsis flavimarginatus sp. nov. further differs from all other species of the genus in having a more slender body (body depth of 3.6 in SL, vs. 2.4-3.3 in SL in other species). In addition, the new species differs from all congeners except Parascolopsis tosensis in having a lower number of pectoral-fin rays (14 vs. 15-17 in other species). Descriptions of each species are based on voucher specimens and are accompanied by photographs of fresh specimens. Using tissue samples obtained from fresh voucher material, a phylogenetic analysis of the COI gene region was conducted for all eight species collected from Tanzanian waters.
Predators have evolved sophisticated behavioral patterns that enable efficient prey capture. The scale-eating cichlid Perissodus microlepis exhibits pronounced morphological asymmetry in mouth-opening direction, corresponding to behavioral laterality in attack direction. Given that recognizing and tracking the flank of prey are crucial for successful predation, we hypothesized that the morphological asymmetry also influences their spatial positioning relative to prey during attack initiation. To test this idea, we simultaneously tracked predator and prey movements using DeepLabCut and analyzed the predatory sequence. Not only strike direction but also the lateralized approach initiation position was correlated with mouth asymmetry. Additionally, trajectory analyses revealed two distinct predation strategies based on the predator's relative position to the prey at the start of the approach: a rear approach, whereby predators move in from behind and strike at close range with strong body flexion, and a side approach, whereby predators initiate from lateral positions at shorter distances and rush forward. Although rear and side attacks differ in their kinematics and strike timing, both strategies achieve high predation success by applying strong forces to the prey's flank. Overall, this study advances our understanding of the predation strategies of scale-eating cichlids, providing insights into their evolutionary significance.
This study aimed to evaluate how immobilizing tilapia fish scale type 1 collagen onto poly(lactic acid) (PLA), following chemical modification with hexamethylenediamine (HMDA), affects the adhesion and proliferation of mouse osteoblast-like cells (OLCs). PLA films were chemically modified by HMDA immersion to introduce amino groups (-NH2) (PLA-NH2). Tilapia fish scale type 1 collagen was subsequently immobilized onto the PLA-NH2 surface via a water-soluble carbodiimide condensation reaction, producing (TFColl-PLA-NH2). Surface properties of the films were characterized using contact angle measurements and X-ray photoelectron spectroscopy (XPS). Biological evaluation was conducted by culturing OLCs on PLA, PLA-NH2, and TFColl-PLA-NH2 films, followed by quantification of cell numbers. The contact angles of PLA-NH2 and TFColl-PLA-NH2 were significantly lower than PLA (P < 0.05). XPS confirmed successful immobilization of tilapia collagen onto the PLA surface. At all time points, TFColl-PLA-NH2 showed the highest cell numbers, followed by PLA-NH2, while PLA had the lowest (P < 0.05). PLA-NH2 promoted calcification more effectively than PLA (P < 0.05), and TFColl- PLA-NH2 further enhanced calcification compared with PLA-NH2 (P < 0.05). PLA surface treatment with HMDA is an effective and straightforward method. Tilapia fish scale type 1 collagen has potential for application as a novel biomaterial source.
During a survey of unidentified anthiadid specimens in the Smithsonian fish collection, we discovered a rare mesophotic anthiadid species, Pseudanthias calloura, originally described from Palau. The species is represented by old material collected in the 1960s from the Macclesfield Bank in the South China Sea (SCS), indicating a broader geographical distribution than previously recognized. Subsequent osteological examinations revealed an unusual predorsal configuration in P. calloura, characterized by a close alignment of the two anteriormost neural spines and the insertion of all supraneurals anterior to the first neural spine. We formally document the occurrence of P. calloura in the SCS and provide a detail description of the species, including previously unreported osteological features based on SCS specimens. Given the widely recognized non-monophyletic nature of Pseudanthias, we also discuss the potential phylogenetic position of P. calloura among its closest relatives. Finally, we review the anthiadid species reported from Macclesfield Bank.
Parrotfishes (Family Scaridae) are keystone herbivores in coral reef ecosystems, regulating algal growth and facilitating coral recruitment through bioerosive feeding. We report the first confirmed records of Scarus quoyi (Valenciennes, 1840) and Scarus zufar (Randall & Hoover, 1995) from the Gulf of Mannar, southeastern India. Specimens (24.0 cm and 24.9 cm TL, respectively) were collected in April 2025 from artisanal fish traps operating at 10-15 m depth near Therespuram. Morphometric and meristic analyses confirmed species identity based on diagnostic features, including the characteristic dark green cheek blotch in S. quoyi and the yellow caudal base patch with irregular vertical bands in S. zufar. These records represent significant eastward range extensions: S. quoyi from the western Pacific into the Bay of Bengal, and S. zufar from its type locality in Oman through the Arabian Sea to India's southeastern coast. The occurrence of S. zufar in mixed rocky-coral substrates may explain its previous absence from coral-focused surveys. These findings underscore the importance of continued systematic surveys and morphological documentation in biodiversity hotspots, particularly for taxonomically challenging groups exhibiting ontogenetic color variation.
This study documents the first recorded occurrence of six commercially important grouper fish species (Teleostei: Perciformes: Epinephelidae) from the Lakshadweep Islands, India. The species documented in this study are the Snubnose grouper Epinephelus macrospilos (Bleeker, 1855), Brownspotted grouper Epinephelus chlorostigma (Valenciennes, 1828), Dotted grouper Epinephelus epistictus (Temminck and Schlegel, 1842), Slender grouper Anyperodon leucogrammicus (Valenciennes, 1828), White-edged lyretail Variola albimarginata Baissac, 1953 and Oblique-banded grouper Epinephelus radiatus (Day, 1868). Both morphological examination and molecular analysis were carried out to characterize and confirm the identity of these species. This investigation represents the first documentation of these six grouper species from the Lakshadweep Islands. The results enhance current understanding of the marine biodiversity of the region and provide valuable information for the management and sustainability of its commercially important fisheries.
To address the challenge of hand intrusion detection in frozen tuna cutting operations where operators wear thermal-insulating gloves, this study proposes a hand detection method based on dual-domain background modeling with absolute accuracy constraints. To tackle issues arising from low-resolution infrared arrays, such as defective pixels, random noise, and complex low-temperature backgrounds, a data preprocessing pipeline integrating defective pixel correction, exponential moving average (EMA), and median filtering is developed. A dual-domain background suppression (DDBS) strategy, combining spatial-domain and temporal-domain models with sensor absolute accuracy constraints, is employed to extract hand foregrounds under complex thermal conditions. Temperature thresholding, connected-component analysis, and hole-filling are further applied to effectively separate hands from frozen tuna. An experimental platform incorporating a Raspberry Pi 4B and an MLX90640 sensor was constructed, and a dataset comprising 1173 infrared frames was collected for validation purposes. Experimental results demonstrate that the proposed method achieves an accuracy of 94.12%, precision of 91.69%, recall of 97.55%, and F1-score of 94.53% for hand intrusion detection, with an average processing time of approximately 1.84 ms per frame. This provides a cost-effective, real-time solution for hand safety monitoring in frozen food processing operations.
We describe a new species, Oxyurichthys jiwaniensissp. nov. based on integrated taxonomic approach and otolith shape parameters. The specimens were collected from Jiwani Hor, Balochistan. This new species is distinguished from other Oxyurichthys by the combination of following characters, overall body cylindrical two separate dorsal fins D1 VI; D2 I, 10; A 10-11; P 13; V 5 rays per-side of the pelvic fin. The pelvic fins are united to form a well-developed disc, the frenum (anterior connecting membrane) is present but the posterior membrane between fin tips is thin or weakly developed and remarkably lacking spine. The spine in anal fin was also absent. The caudal fin (11 rays) short with a blue bloch on the caudal fin dorsally. The body exhibits brown dorsal with minute black and golden dots on the entire dorsal surface. The body ventrally is creamy with only few scattered tiny black dots. The head and operculum are blue-green, covered with small spots distributed across the entire head region. The gill rakers number 10 on the first arch 12 on second arch, 15 on third arch, and 11 on the 4th arch. Scales ctenoid with a row of ctenii is evident on the scales base. The pattern of sensory papillae was observed around the eyes and across the preopercle, opercle, and chin regions. The new species closely resembles jester goby, Oxyurichthyspaulae, but it can be distinguished by the shape of head, black tip on its pelvic fin, and brown bands across its body which is defining characteristics of the jester goby. This study, for the first time, adds to existing knowledge of gobionelline goby diversity revealing that despite population declines, novel species continue to emerge from the northern Arabian Sea coast of Balochistan.
The gobiid genus Valenciennea Bleeker, 1856 comprises 17 bottom-dwelling species distributed on shallow coral reefs throughout the tropical and subtropical Indo-Pacific. Twelve species have Indo-Pacific distributions: within the Indian Ocean, six of these species are only found in the eastern part, while the other six occur in both eastern and western regions. Valenciennea persica is endemic to the northwestern Indian Ocean. Valenciennea puellaris (Tomiyama, 1956), originally described from Japan, and V. strigata (Broussonet, 1782), originally described from French Polynesia and long regarded as widely distributed across the Indo-Pacific, are each shown here to comprise two distinct species. Analysis of mitochondrial COI sequences, detailed re-examination of material from ichthyological collections, and comprehensive colour-pattern comparisons support recognition of the Indian Ocean population of V. puellaris as a new species for science, described herein as V. schliewenisp. nov. Similarly, the southwestern Indian Ocean population of V. strigata has also been shown to represent a distinct species, herein described as V. zaboaesp. nov. Each of the two new species is readily distinguished from all congeners by a distinctive colour pattern in live specimens, as well as by a combination of meristic characters (second dorsal- and anal-fin rays, scale counts), first dorsal- and caudal-fin morphology, head and body proportions, and residual pigmentation in preserved specimens. Georeferenced photographic data from iNaturalist and GBIF (703 records of V. puellaris, 797 of V. strigata) were also used to characterise colour-pattern variation across the Indo-Pacific.
Aporocotyle is the second richest genus of fish blood flukes within the family Aporocotylidae. These cosmopolitan trematodes infect the heart, bulbus arteriosus, and blood vessels of marine fishes belonging to the orders Gadiformes, Ophidiiformes, Perciformes, Pleuronectiformes, and Scorpaeniformes. In this study, three species of Aporocotyle, i.e. A. argentinensis, A. mariachristinae, and A. ymakara, from teleost fishes collected in the San Matías Gulf, Patagonia, Argentina, are morphologically and genetically characterized. Re-examination of these blood flukes provided new detailed drawings, measurements, photomicrographs, confocal and scanning electron microscopy (SEM) images. Aporocotyle argentinensis is redescribed based on type-, voucher- and newly collected material from the bulbus arteriosus, heart and gill blood vessels of the Argentine hake Merluccius hubbsi from Argentina. We generated partial sequences for the large subunit of the nuclear ribosomal RNA (28S rRNA) and the mitochondrial cytochrome c oxidase subunit 1 (cox1) genes for A. argentinensis and A. ymakara and used these sequences to investigate the phylogenetic relationships of these blood flukes. Our morphological analyses highlighted the taxonomic importance of the distribution of tegumental spines, the extension of the posterior caeca, and the presence of a genital atrium to circumscribe and classify species of Aporocotyle. Phylogenetic analyses recovered A. mariachristinae and A. ymakara as closely related taxa and placed the new sequences of A. argentinensis in a clade together with previously published sequences of isolates identified as A. argentinensis from three hake species (Merluccius hubbsi, M. gayi and M. australis) from Argentina, Chile, Peru and the Falkland Islands. This study provides a comprehensive review of the diversity of Aporocotyle in the southwest Atlantic, contributing to a better understanding of the systematics and evolutionary history of these blood flukes.
Economidichthys mornosensis, a new species, is described from the Mornos River delta in southwestern Greece. It is related to Economidichthys pygmaeus, from which it is distinguished by having a large black blotch on the first dorsal fin in males, a short perianal organ, and a scaleless back along the complete base of the second dorsal fin. Molecular data suggest that the new species can be distinguished from E. pygmaeus by a minimum K2P distance of 5.7 % in the mtDNA COI barcode region. Economidichthys mornosensis is endemic to a very small area, and potentially Critically Endangered.
Hematological analyses are widely used to assess the health and physiological status of animals, including fish. Automated hematology analyzers enable rapid and reproducible hematological measurements; however, their application in fish requires species-specific analytical validation due to the presence of nucleated blood cells. This study evaluated the analytical performance of the Sysmex XN-1000V hematology analyzer operated under avian settings (PLT-F channel), in juvenile gilthead seabream (Sparus aurata), one of the cornerstone species of Mediterranean marine aquaculture. Analytical validation included assessment of precision, linearity, carryover, and sample stability. Results were compared with manual reference methods (hemocytometer counts and blood smear-based estimates). In addition, the influence of two anticoagulants (lithium heparin and K₂EDTA) was examined, and the analyzer's ability to detect lipopolysaccharide (LPS)-induced changes in non-erythroid cell population was evaluated. The analyzer showed good precision for most parameters (CV < 5%), although higher variability was observed for granulocyte percentage. Linearity was excellent (R2 ≥ 0.98), and carryover remained below 1% for all variables. Sample stability was significantly better at 4 °C than at room temperature (25 °C), supporting refrigerated storage for up to 24 hours prior to analysis. Comparison with manual reference methods revealed strong correlations and agreement for red blood cell counts and hematocrit, whereas discrepancies were identified in non-erythroid cells differentials. Among anticoagulants, lithium heparin yielded more consistent and reliable results than K₂EDTA. Erythrocyte-related parameters showed the highest analytical reliability, whereas the leucocyte differentiation within the non-erythroid fraction required complementary microscopic evaluation, particularly when assessing LPS-induced inflammatory changes. Overall, the Sysmex XN-1000V demonstrated suitable analytical performance for routine hematological assessment in gilthead seabream when operated under avian settings. These findings support its application in aquaculture health monitoring programs, provided that appropriate anticoagulants are used, samples are promptly processed or refrigerated, and automated results are complemented by microscopic review when leukocyte counts are suspected.
Clinostomum species (spp.) are significant fish-borne zoonotic helminths worldwide, causing yellow grub disease which diminishes the quality, marketability, and productivity of infected fish stocks. Despite their veterinary and public health relevance, detailed molecular investigations of Clinostomum spp. infecting Nile tilapia in Egypt remain limited, especially in Upper Egypt. A total of 400 Nile tilapias were collected from fish farms in Sohag Governorate, Upper Egypt, and initially screened for encysted metacercariae through visual inspection and subsequent light microscopic examination. Recovered parasites were fixed, stained, and identified based on detailed morphological features. For robust molecular confirmation, high-quality genomic DNA was successfully extracted from metacercariae derived from 40 heavily infected representative samples. Targeting of the internal transcribed spacer 2 (ITS2) regions was performed using polymerase chain reaction (PCR) with specific primers. The resulting sequences were examined using BLAST searches and maximum likelihood phylogenetic reconstruction to confirm species identity, and the validated sequences were subsequently deposited in GenBank™. In this study, microscopic examination revealed parasites exhibiting characteristic morphological features of Clinostomum spp., which were detected in 35.0% (140/400; 95% CI: 30.33-39.67) of the examined Nile tilapia (Oreochromis niloticus). The parasite was detected most frequently in tilapia weighing 50-200 g, at a rate of 44.8%, suggesting increased susceptibility among smaller fish. Molecular analyses confirmed the presence of Clinostomum spp. in all positive specimens. The validated sequence (GenBank accession number PQ330909) confirmed through phylogenetic reconstruction identified the encysted metacercariae as Clinostomum phalacrocoracis, showing strong genetic similarity to isolates previously reported from other regions. Overall, these results demonstrate a high prevalence of Clinostomum phalacrocoracis infection in Nile tilapia populations in Upper Egypt, with smaller fish showing the highest frequency. Molecular analyses provide definitive confirmation of Clinostomum phalacrocoracis, complementing morphological identification and offering a comprehensive characterization of the metacercariae. This study also situates the findings within the broader context of previous reports on Nile tilapia in Egypt, providing an updated overview of the parasite's distribution and genetic relationships. Collectively, the evidence underscores the need for enhanced monitoring and management strategies to protect fish health and mitigate potential zoonotic risks in regional aquaculture systems.
The Redspot Emperor, Lethrinus lentjan Lacepède, 1802, is a commercially vital species in the Arabian Gulf fisheries, yet its parasite fauna remains inadequately documented. This study provides the first comprehensive morpho-molecular and epidemiological characterization of a monogenean parasite infecting L. lentjan in this region. Seasonal sampling of 400 fish from Jubail and Dammam revealed a Benedenia sp. (cf. akajin) exclusively parasitizing the gills. Integrated morphological analysis showed greatest similarity to Benedenia akajin, but differences in microhabitat (gills vs. body surface) and larger body size were observed. Molecular phylogeny based on partial 28 S rDNA (GenBank PX711249) confirmed close affinity with B. akajin (99.2% sequence similarity) and revealed limited genetic differentiation (0.8% uncorrected p-distance), with moderate nodal support (ML bootstrap 52%). Epidemiological analysis identified clear seasonal and spatial patterns: infection prevalence and intensity peaked during summer (up to 96% in Jubail) and were consistently higher in Jubail than in Dammam. Furthermore, a positive trend was found between host size and parasite burden. This study identifies a previously uncharacterized Benedenia population, closely related to B. akajin, as a significant parasite of L. lentjan in the Arabian Gulf. Given the limitations of the current evidence (single molecular marker, moderate phylogenetic support, and morphological overlaps with congeners); the parasite is provisionally designated as Benedenia sp. (cf. akajin). The findings delineate key risk factors - summer temperatures, the Jubail area, and larger host size - providing a scientific foundation for targeted health surveillance and sustainable management of this fishery.
The family Sciaenidae comprises around 300 species and 70 genera, with the Indo-West Pacific (IWP) region exhibiting the highest species richness. The genus Boesemania Trewavas, 1977 was established as a monotypic group based on the swim bladder and otolith morphology of Johnius microlepis Bleeker. Corvina polykladiskos Bleeker was recognized as the third species of the genus Bahaba. Based on recent morphology and molecular evidence, we assign Bahaba polykladiskos to the genus Boesemania.Boesemania polykladiskos is distinguished from Boesemania microlepis by its distinctly larger scales, the number of lateral-line, upper and lower trans-lateral-line rows, and sagitta and swim-bladder morphology. Phylogenetic analysis of 24 sciaenid species representing 23 genera from the Indo-West Pacific region further confirms that Boesemania is monophyletic and that Boesemania polykladiskos is the sister species of Boesemania microlepis. The two Boesemania species are commercially important fish in their native range and play an essential role in the global luxury dried swim-bladder trade. However, significant knowledge gaps persist regarding their ecology, biology, and population status. Consequently, this paper also addresses the need for further research and conservation measures for these species.
Fatty acids are crucial for steroidogenesis and gonadal development in fish. A 90-day feeding experiment was conducted before maturation to assess the effects of different dietary levels of linoleic acid (LA) and linolenic acid (LNA) on gonadal development and reproductive performance in Channa striata broodstocks. A total of 300 male and female broodstocks were divided into five treatment groups, each with three replicates, using a completely randomized design. The fish were fed five experimental diets that were isonitrogenous (42%) and isolipidic (12%), containing 0% (B0), 0.5% LA + 1% LNA (B1), 0.5% LA + 0.5% LNA (B2), 1% LA + 1% LNA (B3), and 1% LA + 0.5% LNA (B4). Factorial diets were analyzed using two-way ANOVA (LA and LNA as fixed factors), complemented by one-way ANOVA across all five diets. Reproductive parameters (GSI, fecundity, egg size, fertilization, hatching, and larval survival) improved with supplementation and were significantly improved by a dominant LA main effect (P < 0.05), being the highest in fish fed B3. The fertilization rate also showed a significant LA × LNA interaction (P = 0.001). Liver, gonad, and egg n-3 and n-6 Lc-PUFA increased with dietary LA, and a significant LA × LNA interaction governed the DHA/EPA ratio in all three tissues (P ≤ 0.011) and hepatic DHA accumulation (P = 0.005), each higher in B3. Plasma 11-ketotestosterone (males) and 17β-estradiol and vitellogenin (females) were elevated by dietary LA and each showed a significant interaction. Hepatic Δ6/Δ5 fads2 and gonadal cyp17a1 and cyp19a1 responded through individual main effects without any interaction. Overall, dietary LA drove Lc-PUFA accumulation and reproductive output, whereas LA and LNA acted synergistically to elevate the tissue DHA/EPA balance and reproductive endocrine responses. 1% LA with 0.5-1% LNA (B3) most effectively enhanced the reproductive performance of striped murrel broodstock.