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The Indian halibut Psettodes erumei (Family Psettodidae), a primitive lineage of flatfishes exhibiting both sinistral and dextral morphs, provides a unique model for examining the evolutionary significance of morphological asymmetry in flatfishes. This study tested whether eye-sidedness influences somatic growth, body shape, and reproductive traits in P. erumei from the western Arabian Gulf. A total of 215 individuals were collected between 2020 and 2022, with sinistral and dextral morphs occurring in near-equal proportions. Model selection based on Akaike weights revealed that sex, rather than eye-sidedness, was the primary factor influencing length–weight relationships and growth, with females attaining significantly larger asymptotic lengths. Eye-sidedness had no detectable effect on gonadosomatic index patterns or length at 50% maturity. While Procrustes regression detected statistically significant differences in body landmarks and semilandmarks between morphs, these differences were minor and likely biologically negligible. Overall, the results support the hypothesis that eye-sidedness in P. erumei does not confer a measurable evolutionary advantage and imply that differences in developmental mechanisms, rather than adaptive advantages, played a primary role in fixing directional asymmetry in most flatfish lineages. Future research into the molecular and developmental pathways governing eye-sidedness will be essential for understanding why the vast majority of flatfish species exhibit monomorphic asymmetry.

The mitogenomic evolution of the Psettodes flatfishes is still poorly known from their range distribution in eastern Atlantic and Indo-West Pacific Oceans. The study delves into the matrilineal evolutionary pathway of these primitive flatfishes, with a specific focus on the complete mitogenome of the Psettodes belcheri species, as determined through next-generation sequencing. The mitogenome in question spans a length of 16,747 base pairs and comprises a total of 37 genes, including 13 protein-coding genes, 2 ribosomal RNA genes, 22 transfer RNA genes, and a control region. Notably, the mitogenome of P. belcheri exhibits a bias towards AT base pairs, with a composition of 54.15%, mirroring a similar bias observed in its close relative, Psettodes erumei, which showcases percentages of 53.07% and 53.61%. Most of the protein-coding genes commence with an ATG initiation codon, except for Cytochrome c oxidase I (COI), which initiates with a GTG codon. Additionally, four protein-coding genes commence with a TAA termination codon, while seven others exhibit incomplete termination codons. Furthermore, two protein-coding genes, namely NAD1 and NAD6, terminate with AGG and TAG stop codons, respectively. In the mitogenome of P. belcheri, the majority of transfer RNAs demonstrate the classical cloverleaf secondary structures, except for tRNA-serine, which lacks a DHU stem. Comparative analysis of conserved blocks within the control regions of two Psettodidae species unveiled that the CSB-II block extended to a length of 51 base pairs, surpassing the other blocks and encompassing highly variable sites. A comprehensive phylogenetic analysis using mitochondrial genomes (13 concatenated PCGs) categorized various Pleuronectiformes species, highlighting the basal position of the Psettodidae family and showed monophyletic clustering of Psettodes species. The approximate divergence time (35−10 MYA) between P. belcheri and P. erumei was estimated, providing insights into their separation and colonization during the early Miocene. The TimeTree analysis also estimated the divergence of two suborders, Psettodoidei and Pleuronectoidei, during the late Paleocene to early Eocene (56.87 MYA). The distribution patterns of Psettodes flatfishes were influenced by ocean currents and environmental conditions, contributing to their ecological speciation. In the face of climate change and anthropogenic activities, the conservation implications of Psettodes flatfishes are emphasized, underscoring the need for regulated harvesting and adaptive management strategies to ensure their survival in changing marine ecosystems. Overall, this study contributes to understanding the evolutionary history, genetic diversity, and conservation needs of Psettodes flatfishes globally. However, the multifaceted exploration of mitogenome and larger-scale genomic data of Psettodes flatfish will provide invaluable insights into their genetic characterization, evolutionary history, environmental adaptation, and conservation in the eastern Atlantic and Indo-West Pacific Oceans.

Here, a comprehensive study was designed to estimate the human risk assessment attributed to exposure of polycyclic aromatic hydrocarbons (PAHs)in sediment and fish in most polluted shore area in north of Persian Gulf. To this end, a total of 20 sediment and inhabitual Fish, as one of most commercial fish, samples were randomly collected from 20 different stations along Bushehr Province coastline. The 16 different components of PAHs were extracted from sediment and edible parts of inhabitual fish and measured with high-performance liquid chromatography (HPLC) and gas chromatography (GC), respectively. In addition, dietary daily intake (DDI) values of PAHs via ingestion Indian halibut and the incremental lifetime cancer risk (ILCR) attributed to human exposure to sediments PAHs via (a) inhalation, (b) ingestion, and (c) dermal contact for two groups of ages: children (1–11 years) and adults (18–70 years) were estimated. The results indicated that all individual PAHs except for Benzo(b)flouranthene (BbF) and Benzo(ghi) perylene (BgP) were detected in different sediment sample throughout the study area with average concentration between 2.275 ± 4.993 mg.kg –1 dw. Furthermore, Naphthalene (Nap) with highest average concentration of 3.906 ± 3.039 mg.kg –1 dw was measured at the Indian halibut. In addition, the human risk analysis indicated that excess cancer risk (ECR) attributed to PAHs in sediment and fish in Asaluyeh with high industrial activities on oil and derivatives were higher the value recommended by USEPA (10 −6 ). Therefore, a comprehensive analysis on spatial distribution and human risk assessment of PAHs in sediment and fish can improve the awareness on environmental threat in order to aid authorities and decision maker to find a sustainable solution.

In this study, sole fish (Psettodes erumei) muscle mass was used for the isolation of inflammation suppressing peptide through the enzymatic hydrolysis process. The amino acid composition revealed high amount of histidine, alanine, lysine in the crude muscle tissue. The anti-inflammatory assays performed on enzymatic hydrolysates showed that protein inhibition and membrane protection activity was highest for 12th h trypsin hydrolysate to be 81.64 ± 1.54% and 73.3 ± 1.03% respectively. This active hour hydrolysate was subjected to partial separation and chromatographic purification where the peak showing the highest anti-inflammatory activity was subjected to liquid chromatography-mass spectrometry (LC–MS/MS) which revealed a short novel peptide sequence of MTQML with a molecular weight 622 Da. The peptide was observed to be functionally stable and in vitro study revealed that the peptide was non-cytotoxic and reduced the expression of nitric oxide as well as nuclear factor kappa B (NFκB) complex. This leads to the downregulation of the NFκB signaling pathway and suppression of inflammation. Furthermore, molecular docking analysis confirmed the binding of peptide to cytokine and NFκB-p65 receptors to their inhibiting site at lower binding energy. This novel bioactive peptide could be used as non-toxic inflammation suppressing therapeutic in nutraceutical as well as pharmaceutical applications.

Background The monophyly of flatfishes has not been supported in many molecular phylogenetic studies. The monophyly of Pleuronectoidei, which comprises all but one family of flatfishes, is broadly supported. However, the Psettodoidei, comprising the single family Psettodidae, is often found to be most closely related to other carangimorphs based on substantial sequencing efforts and diversely analytical methods. In this study, we examined why this particular result is often obtained. Results The mitogenomes of five flatfishes were determined. Select mitogenomes of representative carangimorph species were further employed for phylogenetic and molecular clock analyses. Our phylogenetic results do not fully support Psettodes as a sister group to pleuronectoids or other carangimorphs. And results also supported the evidence of long-branch attraction between Psettodes and the adjacent clades . Two chronograms, derived from Bayesian relaxed-clock methods, suggest that over a short period in the early Paleocene, a series of important evolutionary events occurred in carangimorphs. Conclusion Based on insights provided by the molecular clock, we propose the following evolutionary explanation for the difficulty in determining the phylogenetic position of Psettodes : The initial diversification of Psettodes was very close in time to the initial diversification of carangimorphs, and the primary diversification time of pleuronectoids, the other suborder of flatfishes, occurred later than that of some percomorph taxa. Additionally, the clade of Psettodes is long and naked branch, which supports the uncertainty of its phylogenetic placement. Finally, we confirmed the monophyly of flatfishes, which was accepted by most ichthyologists.

In this study, concentrations of Cd, Co, Cu, Ni, Pb, Fe, and Hg were determined in commercially valuable fish from Khuzestan shore, northwest of the Persian Gulf. It was also our intention to evaluate potential risks to human health associated with seafood consumption. The liver and skin showed higher metal concentrations than the muscle. The results showed that heavy metal concentrations in different food habitats increase in the following order: benthic omnivorous fish < zooplanktivore fish < phytoplanktivore fish < piscivore fish. Also, the comparison indicated that benthic species ( Euryglossa orientalis , Otolithes ruber ) were more contaminated than pelagic species ( Liza abu and Psettodes erumei ). Therefore, the concentration of heavy metals in edible part of fish species did not exceed the permissible limits proposed by Food and Agriculture Organization (FAO) ( 1983 ), WHO ( 1996 ), Regional Organization for the Protection of the Marine Environment (ROPME) ( 1999 ), and FAD ( 2001 ) which are suitable for human consumption, except for Ni and Cd in E. orientalis and Pb in O. ruber .

This study investigated the prevalence, morphology, molecular identification, and histopathological effects of larval tapeworms (plerocercoids) infecting the skeletal muscles of the Indian halibut ( Psettodes erumei ) collected from the coastal waters of the Arabian Gulf. Numerous oval or round blastocysts, measuring 13–26 mm, were found embedded within the muscular tissues of the Indian halibut, rendering the fish unsuitable for human consumption. Morphological and molecular analyses identified the plerocercoids as Dasyrhynchus giganteus (family Dasyrhynchidae), with an overall prevalence of 15.4%. The seasonal prevalence was the highest in summer (14.6%), followed by spring (10.6%), winter (4.4%), and autumn (3.5%). Infection rates increased with fish size. Histopathological examination revealed fibrous connective tissue capsules surrounding the larvae, causing muscular atrophy and degenerative changes, with few inflammatory eosinophilic cells. Molecular and phylogenetic analysis of the 28S rDNA gene sequences confirmed the specimens as D. giganteus , clustered closely with other sequences of D. giganteus with 100% bootstrap values. This study provided valuable insights into the parasitic infection dynamics, seasonal variation, molecular identification, and histopathological effects, highlighting the importance of monitoring fish for food safety and public health implications.

The Spermonde Islands are at the center of the world's coral triangle, crossed by the Wallace Line, so its resources must be managed sustainably. The Indian halibut Psettodes erumei is the most primitive species of flatfish, which is thought to have suffered from exploitation. This research aims to assess the utilization status of the P. erumei stock in the Spermonde Islands. The P. erumei samples were taken from the fishers catch who landed at the Fish Landing Port, Makassar City. The population and exploitation parameters observed were growth, mortality, selectivity curve, capture probability, virtual population, and recruitment. The number of P. erumei samples obtained during the research was 419, with an average length of 28.9 cm (between 6.7 and 77.5 cm). The asymptote length (Loo) was 78.75 cm and the growth rate (K) was 0.73, while the growth performance index (cp) was 3.85. The first capture length (Lc) was 16.39 cm, the capture length at probability 0.25 (L25) was 14.24 cm, at 0.75 (L75) it was 18.55 cm, and at the time of full recruitment to the capture fishery (L100) it was 22.5 cm. The total death rate (Z) was 4.07, the instantaneous natural death rate (M) was 0.72, and the fishing death rate (F) was 3.353. Current exploitation (E) was estimated at 0.82, indicating that the current exploitation level is far beyond the limit of sustainable utilization (0.5). The condition of being highly exploited indicates that a sustainable management is urgently needed.

Examinations of nematodes collected from some marine fishes off the southwestern coast of Java, Indonesia in 2000 and 2001 revealed the presence of the following six species: ascaridoids Ichthyascaris grandis sp. n. from the intestine of Lophiomus setigerus (Vahl), I. cf. longispicula Li, Liu, Liu et Zhang, 2012 from the intestine of Conger cinereus Rüppel, Ichthyascaris sp. from the body cavity of Lobotes surinamensis (Bloch), and Raphidascaroides halieutaeae Yin, 1983 from the intestine of Halieutaea stellata (Vahl), and philometrids Philometra ivaschkini Parukhin, 1976 from the stomach wall of Trichiurus lepturus Linnaeus and P. psettoditis Moravec, Walter et Yuniar, 2012 from the body cavity (liver) of Psettodes erumei (Bloch et Schneider). Descriptions of these nematodes based on light and scanning electron microscopical studies are provided. The new species I. grandis sp. n. is mainly characterised by large body measurements (males and females up to 41.8 mm and 73.6 mm long, respectively), the length of spicules (0.99-1.05 mm), the tail tip usually without rudimentary spines and by the presence of 44-53 pairs of caudal papillae, eight to twelve of which being postanals. In addition to new data on the morphology of R. halieutaeae and other nematodes recorded, the 11 species of Raphidascaroides Yamaguti, 1941 poorly described from marine fishes in South Asia and reviewed in the monograph of Sood (2017) are considered species inquirendae and incertae sedis.Examinations of nematodes collected from some marine fishes off the southwestern coast of Java, Indonesia in 2000 and 2001 revealed the presence of the following six species: ascaridoids Ichthyascaris grandis sp. n. from the intestine of Lophiomus setigerus (Vahl), I. cf. longispicula Li, Liu, Liu et Zhang, 2012 from the intestine of Conger cinereus Rüppel, Ichthyascaris sp. from the body cavity of Lobotes surinamensis (Bloch), and Raphidascaroides halieutaeae Yin, 1983 from the intestine of Halieutaea stellata (Vahl), and philometrids Philometra ivaschkini Parukhin, 1976 from the stomach wall of Trichiurus lepturus Linnaeus and P. psettoditis Moravec, Walter et Yuniar, 2012 from the body cavity (liver) of Psettodes erumei (Bloch et Schneider). Descriptions of these nematodes based on light and scanning electron microscopical studies are provided. The new species I. grandis sp. n. is mainly characterised by large body measurements (males and females up to 41.8 mm and 73.6 mm long, respectively), the length of spicules (0.99-1.05 mm), the tail tip usually without rudimentary spines and by the presence of 44-53 pairs of caudal papillae, eight to twelve of which being postanals. In addition to new data on the morphology of R. halieutaeae and other nematodes recorded, the 11 species of Raphidascaroides Yamaguti, 1941 poorly described from marine fishes in South Asia and reviewed in the monograph of Sood (2017) are considered species inquirendae and incertae sedis.

This study aimed to compare the concentrations of heavy metals in Psettodes erumei as host fish and larvae of Hysterothylacium spp. as its parasite. Moreover, to evaluate the larvae as bio-indicators the uptake of heavy metals, the infected and non-infected fish were also compared. Fresh P. erumei species (n = 19) were randomly sampled during four months from Bushehr County, Iran. The digestive tract of each fish was examined for nematode parasites using a stereomicroscopy. The isolated nematodes were identified, and content of Fe, Cu, Zn, Co, Ni, Cr, As, Cd, Hg, and Pb were measured using ICP-OES. The metal concentrations were simultaneously analyzed for the muscles of infected fish and their parasites, as well as non-infected ones. Of the 19 P. erumei examined, 13 (68.4%) P. erumei were infected with Hysterothylacium spp. larvae. The parasites had significantly higher level of Fe, Cu, Zn, and Ni (with mean value of 7.59, 0.572, 1.223, and 4.623 mg/kg, respectively) than the muscles of the host fishes (with mean value of 3.29, 0.0010, 0.586, and 0.277 mg/kg, respectively) ( p  < 0.05). Infected hosts showed significantly lower amounts of As element in their muscles (0.050 mg/kg) than non-infected hosts (0.113 mg/kg) ( p  < 0.05). The findings emphasize the potential role of Hysterothylacium spp. larvae as bio-indicators for monitoring heavy metals pollution in marine ecosystems.