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In this study, we aimed to clarify the taxonomic status of Belonidae species distributed in the Mediterranean Sea and the Black Sea by conducting detailed genetic and morphological markers. A total of 550 needlefish samples were caught between January 2022 and January 2024. The data set used in the study contains a total of 171 sequences for the COI gene and 120 sequences for the 12s rRNA gene from different Belonidae species, including data from GenBank. Systematic analysis of needlefish species was investigated by using sequencing of mtDNA COI and 12s rRNA gene regions and morphological characters in the Turkish Marine Waters. A separate analysis of the two mitochondrial genes supported by morphological characters revealed that each species is grouped within itself. The genetic and morphological analyses showed that Belone belone acus and Belone belone euxini which are considered as the subspecies of Belone belone are not subspecies of the genus Belone and should be considered at the species level, Belone belone . Belone svetovidovi is also considerably different from Belone belone and should be considered as a different species. T. acus imperialis , which is thought to be distributed in the Mediterranean Sea, is not a subspecies of Tylosorus acus and should be revised as Tylosorus imperialis which genetically differs from Tylosorus acus and also other Tylosorus species at the species level.

Understanding factors driving diversity across biodiversity hotspots is critical for formulating conservation priorities in the face of ongoing and escalating environmental deterioration. While biodiversity hotspots encompass a small fraction of Earth's land surface, more than half the world's plants and two-thirds of terrestrial vertebrate species are endemic to these hotspots. Tropical Southeast (SE) Asia displays extraordinary species richness, encompassing four biodiversity hotspots, though disentangling multiple potential drivers of species richness is confounded by the region's dynamic geological and climatic history. Here, we use multilocus molecular genetic data from dense multispecies sampling of freshwater fishes across three biodiversity hotspots, to test the effect of Quaternary climate change and resulting drainage rearrangements on aquatic faunal diversification. While Cenozoic geological processes have clearly shaped evolutionary history in SE Asian halfbeak fishes, we show that paleo-drainage re-arrangements resulting from Quaternary climate change played a significant role in the spatiotemporal evolution of lowland aquatic taxa, and provide priorities for conservation efforts.

Isopods infest fish worldwide, but their role as disease vectors remains poorly understood. Here, we describe infestation of Atlantic bonefish ( Albula vulpes ) in Belize with isopods in two of three locations studied, with infestation rates of 15 and 44%. Isopods fed aggressively, and infested fish showed missing scales and scars. Gross morphologic and molecular phylogenetic analyses revealed the isopods to cluster within the family Aegidae and to be most closely related to members of the genus Rocinela , which are globally distributed micro-predators of fish. Metagenomic analysis of 10 isopods identified 11 viruses, including two novel reoviruses ( Reovirales ) in the families Sedoreoviridae and Spinareoviridae . The novel sedoreovirus clustered phylogenetically within an invertebrate-specific clade of viruses related to the genus Orbivirus , which contains arboviruses of global concern for mammal health. The novel spinareovirus clustered within the fish-infecting genus Aquareovirus , which contains viruses of global concern for fish health. Metagenomic analyses revealed no evidence of infection of bonefish with the novel aquareovirus, suggesting that viremia in bonefish is absent, low, or transient, or that isopods may have acquired the virus from other fish. During field collections, isopods aggressively bit humans, and blood meal analysis confirmed that isopods had fed on bonefish, other fish, and humans. Vector-borne transmission may be an underappreciated mechanism for aquareovirus transmission and for virus host switching between fish and other species, which has been inferred across viral families from studies of deep virus evolution.

A new genus and species of monogenean belonging to Axinidae, Ondoella sajori n. g., n. sp. , is described based on specimens collected from the gill of Japanese halfbeak, Hyporhamphus sajori (Temminck & Schlegel) (Beloniformes: Hemiramphidae) from the Seto Inland Sea, Japan. Ondoella n. g. differs from all other genera of axinids mainly by the possession of an unarmed cirrus. Ondoella n. g. is characterised by the following features: (i) the spherical cirrus present; (ii) spines on the cirrus absent; (iii) the genital pore with a crown of a row of spines; (iv) the elongate body; (v) the vaginal pore with a horn-like spine, and (vi) vaginal pore dorsolateral. The phylogenetic analysis based on 28S rDNA sequences suggests that O. sajori and Axinidae constitute a monophyletic group. A comprehensive list of parasites known to infect H . sajori provided.

The garfish Belone belone represents the only valid endemic Belone species for the Mediterranean Sea and the eastern Atlantic Ocean. It shows a wide global distribution range, with a high commercial value and ecological relevance in the pelagic domain. Despite this, there needs to be more knowledge regarding the otoliths of this species, with the total absence of descriptions regarding asterisci and lapilli from Mediterranean populations and a lack of studies on the reliability of shape analysis on its sagittae. The present paper aims to provide the first main contours description of the three otoliths pairs from a Mediterranean population, providing an accurate investigation of morphology, morphometry, and intra-specific variability of sagittae, lapilli, and asterisci. Results showed (i) the absence of directional bilateral asymmetry and sexual asymmetry for the three otoliths pairs, (ii) a different morphology and morphometry of sagittae, lapilli and asterisci than those described in the literature, and (iii) an enhanced variability between sagittae morphometry and shape between the three investigated size classes. All these data confirmed the reliability of the studied species of shape analysis, showing a geographical and size-related variability of otoliths features probably related to genetics, environmental conditions, and life habits variations.

Flying fishes (Exocoetidae) are a highly specialized group of Beloniformes, with 4 subfamilies, 7 genera, and 78 species. However,only a small number of species of flying fishes have the mitochondrial genome described sof ar. Considering the importance of mitogenomes in evolution, in this study we aimed to expand the description of mitochondrial genomes and the phylogenetic relationships of Exocoetidae. We used publicly available DNA-Seq libraries to assemble the mitochondrial genomes of 7 species of flying fishes. The mitochondrial genomes of Exocoetidae showed conserved features among all species. With 22 tRNAs, 2 rRNAs, and 13 protein-coding genes, they share common features among vertebrates. was reconstructedaspolyphyletic, with four clades, which reinforces previous studies that recovered as non-monophyletic.Werecoveredallfour subfamilies as monophyletic,with Parexocoetinae as the sister group of all other subfamilies.The genetic distance between Exocoetidae species was two times smaller than the genetic distance among the species, indicating a low genetic divergence in the family. Hereby, this study expanded the knowledge of mitochondrial genome features and presented one of the most comprehensive mitochondrial genome datasets used for studying flying fishestodate. This was achievable using publicly available data, reinforcing the importanceof the re-use of such data in the fields of mitogenomics and phylogenetics.

This study presents an extensive review of published and unpublished occurrence records of fish species in the Rio Negro drainage system within the Brazilian territory. The data was gathered from two main sources: 1) litterature compilations of species occurrence records, including original descriptions and revisionary studies; and 2) specimens verification at the INPA fish collection. The results reveal a rich and diversified ichthyofauna, with 1,165 species distributed in 17 orders (+ two incertae sedis), 56 families, and 389 genera. A large portion of the fish fauna (54.3% of the species) is composed of small-sized fishes < 10 cm in standard length. The main groups are Characiformes (454 species; 39.0%), Siluriformes (416; 35.7%), Gymnotiformes (105; 9.0%), and Cichliformes (102; 8.8%). The species composition differs between the main aquatic environments, such as: main channel (159 species), lakes (296), tributary rivers (596), small streams (234), seasonal beaches (186), and rapids (41). Part of the ichthyofauna is shared with adjacent basins, such as the Orinoco, rivers of the Guiana Shield, lower Solimões/Amazonas and upper Amazonas, which contributes to the remarkable ichthyofaunal diversity of the basin. A high rate of species endemism was observed in Characidae (24), Loricariidae (18), Cichlidae (18) and Callichthyidae (18), totalling 156 species (13.4%) endemic to the basin. An estimation of the species richness for the Rio Negro basin, considering 23 published references, resulted in 1,466 and 1,759 species (Jackknife 1 and 2, respectively), which seems reasonable when considering the large number of morphotypes left out of the present list and the low sampling effort in many areas of the basin. The results presented herein provide an additional tool for environmental managers and decision makers for conservation purposes of one of the richest and most well-preserved sub-basins of the Rio Amazonas system.

Southern Vietnam, particularly the Mekong Delta, is popular in inland fish species diversity. In this study, fish species diversity across six stations from the estuary to the upstream of Cua Tieu River, which is situated in the Tien Giang province in Southern Vietnam, has been studied from January 2018 to June 2020. Altogether, 2088 specimens were collected and classified, and these belonged to 115 species, 98 genera, and 54 families of 15 orders that were recognized and identified. The names of species, genera, families, and orders are cited. In the total of 115 species, the Perch-like order (Perciformes) is the most diverse group, with 50 species (consist of 43.48% of total species). The catfish order (Siluriformes) is the second-most diverse group, consisting of 19 species (16.52% of total species). The carp order (Cypriniformes) consists of 8 species (6.96%), and the herring order (Clupeiformes) consists of 7 species (6.09%). Three orders of fishes, needle fish order (Beloniformes), Spiny eel order (Synbranchiformes), and flounder order (Pleuronectiformes), consist of 6 species (5.22%), and other orders consist of 1–3 species (0.87–2.61%). Among the 115 species recorded, 4 species were classified as vulnerable (VU) in the Red Data Book of Viet Nam ( 2007 ) (which is 3.48% of the total species collected). These are Elops saurus , Anodontostoma chacunda , Datnioides polota , and Toxotes chatareus . According to the IUCN Red list ( 2020 ), 1 species is endangered (EN) (0.87%), 1 species is vulnerable (VU) (0.87%), 3 species of fish are near threatened (NT) (2.61%), 6 species are data deficient (DD) (5.22%), and 58 species are least concern (LC) (50.43%). The result also recorded 41 fish as migratory species (26 freshwater species and 15 marine species), which is 35.65% of total species collected. Some migratory species are important and endemic species of the Mekong River, such as Bagarius yarrelli , Boesemania microlepis , Yasuhikotakia modesta , Cyclocheilos enoplos , Pangasianodon hypophthalmus , Pangasius conchophilus , Pangasius krempfi , Pangasius pleurotaenia , Phalacronotus bleekeri.

Rhadinorhynchus hiansi Soota and Bhattacharya, 1981, has remained unknown since its original incomplete description from 2 male specimens collected from the flat needlefish Ablennes hians Valenciennes (Belonidae) off Trivandrum, Kerala, India. Recent collections of fishes along the Pacific coast of Vietnam in 2016 and 2017 produced many specimens of the same species from the striped bonito Sarda orientalis Temminck and Schlegel (Scombridae) off the southern Pacific coast of Vietnam at Nha Trang. We describe females for the first time, assign a female allotype status, and provide an expanded description of males from a larger collection completing missing information on hooks and hook roots, receptacle, lemnisci, cement glands, Saefftigen's pouch, and trunk spines. Specimens of R. hiansi characteristically have no dorsal spines in the posterior field of trunk spines and a long proboscis with 36–48 dorso-ventrally differentiated proboscis hooks per row becoming progressively smaller posteriorly then increasing in size near the posterior end to a maximum at the posterior-most ring. Trunk, testes, and lemnisci in our specimens were considerably larger than those reported in the original description, but the proboscis was relatively smaller. The females had long reproductive system and corrugated elliptic eggs without polar prolongation of fertilization membrane. Energy Dispersive X-ray Analysis (EDXA) demonstrates high levels of calcium and phosphorus in large gallium cut hooks and high levels of sulfur in tip cuts of large and small hooks and in spines. This EDXA pattern is a characteristic fingerprint of R. hiansi. The molecular profile of R. hiansi is described from 18S rDNA and COI genes, and phylogenetic relationships with most closely related species are discussed.

A total of 21 Pharao flyingfish Cypselurus naresii (Günther) from the Gulf of Tonkin off Vietnam was examined for monogeneans. Ten individuals were parasitised by 72 specimens of two new axinid species of two rare and little known genera, Unnithanaxine Price, 1962 containing only one species, U. parawa (Unnithan, 1957), and Loxuroides Price, 1962 containing two species, L. sasikala (Unnithan, 1957) and L. fungilliformis Zhang, Ding, Liu & Wang, 1999. Unnithanaxine naresii n. sp. and Loxuroides pricei n. sp. are described and differentiated from the related species. Unnithanaxine naresii n. sp. is morphologically similar to U. parawa but is distinguished by the size of the clamps and reproduction organs, the number of spines in the lateral groups of the genital atrium, and in parasitism in a host fish species of a different genus. Loxuroides pricei n. sp. differs from L. fungilliformis in the greater size of the body, the number of clamps, testes, spines on cirrus and genital atrium, and in parasitism in a different host family. Similarly, L. pricei can be separated from L. sasikala in having a shorter distance from the anterior extremity to genital atrium or vaginal region, fewer testes, and a slightly greater number of spines on cirrus and genital atrium.