Marine Fish Species Research Articles

Intestinal Fatty Acid Binding Protein Gene Variation in European Sea Bass (Dicentrarchus labrax)

Fatty acid binding proteins (FABPs), which belong to the multigene family, play an important role in homeostasis, lipid uptake and transport in tissues. Intestinal fatty acid binding protein (I-FABP) is a small cytosolic protein and is highly active in intracellular fatty acid metabolism in fish gut. The European Sea bass (Dicentrarchus labrax) is an important commercial marine fish species in the Mediterranean region. In the present study, the partial I-FABP gene region of European sea bass was sequenced for detecting single nucleotide polymorphism (SNP) using DNA sequencing. We identified one SNP (g.2450T>C) in the noncoding region of the I-FABP gene in European sea bass. In this study, the relationship between the g.2450T>C locus of the I-FABP (fabp2) gene and body length, post-anal length, body weight and fillet weight was found significant (PC locus in I-FABP which could affect growth and muscle fat content, can be used for marker-assisted selection (MAS) studies in European sea bass.

Nutritional composition, heavy metal contents and lipid quality of five marine fish species from Cameroon coast

The nutritional value, heavy metal content and lipid quality of five marine fishes from, Cameroon coast were be investigated. Fish samples from Ilisha africana, Sardinella, maderensis, Cyprinus carpio, Arius parkii and Ethmalosa fimbriata were collected at, the Douala sea port, carried to the laboratory, washed with distilled water and, processed. Proximal composition, minerals, lipid quality and heavy metal analyses, were performed using AOAC standard methods. Results show that proteins (18.43%), and lipids (3.69%) contents were higher in Ilisha africana. Cyprinus carpio had the, highest ash content (4.59%). Contents of minerals and heavy metals were found as, follows: P > Mg > K > Ca > Na > Fe > Zn > Cu > Mn and Hg > Pb > Cd > As. Oils extracted from C. carpio, A. parkii and E. fimbriata were semi-siccative while those of I. africana and S. maderensis were siccative. Thus, these fish species are good sources of proteins and, minerals that can be used for managing mineral deficiencies in humans and animals.

Navigating the scales of diversity in subtropical and coastal fish assemblages ascertained by eDNA and visual surveys

Environmental DNA (eDNA) metabarcoding emerges as a powerful method, allowing a more exhaustive investigation of fish fauna than any other methods. Yet, the general use of eDNA as a replacement of traditional methods such as visual surveys or physical sampling remains debatable. Therefore, a prior understanding of eDNA’s spatial resolution is necessary. This study aimed to compare the assessments of fish diversity at three spatial scales by eDNA, underwater visual census (UVC), and diver-operated video (DOV) surveys across 21 reef sites in northern Taiwan. The specific objectives were to explore the regional species pool (γ-diversity), reveal spatial patterns of fish assemblages (β-diversity), and disentangle the relationships between fish assemblages and benthic composition (α-diversity). At the γ-diversity level, a total of 438 marine fish species were detected across methods. eDNA exhibits an extraordinary power to explore the regional species pool given sufficient replication, a power which is unachievable by DOV and UVC. At the β-diversity level, all the methods successfully revealed the same spatial patterns of beta diversity and the distance decay of similarity in fish assemblages. At the α-diversity level, none of the methods is capable of investigating the entire resident fish fauna, but visual surveys are more suitable for scrutinizing interactions between fish and benthos. Instead of undiscriminatingly recommending a combination of eDNA with traditional survey methods, we suggest implementing specific surveys in accordance with the ecological questions of interest.

Estimation of ecological carrying capacity of small-scale fish in marine ranch of the Pearl River Estuary, China

Small-scale marine fish are a critical part of the food chain and energy flow of the marine ecosystem. The ecological carrying capacity (ECC) is important to better understand the marine fishery ecosystems. However, few studies have focused on the ECC of small-scale marine fish species. This study proposed the estimation model of the ECC for small-scale fish species, and estimated the ECC of 18 small-scale fish species in the targeted sea areas (artificial reef area near Wanshan Island, WAR; non-artificial reef area near Wanshan Island, N- WAR; artificial reef area near Miaowan Island, MAR; non-artificial reef area near Miaowan Island, N- MAR; and control area near Wailingding Island, C-WLD) in the Pearl River Estuary (PRE), China. The result shows that the ECC of the 18 small-scale fish species in the marine ranch of the PRE is ranged from 85.92 t/km 2 to 551.33 t/km 2. In terms of magnitude: WAR > MAR > N- WAR > N- MAR > C-WLD, and their ECCs accounted for 50.68%, 16.89%, 13.74%, and 10.79% and 7.90% of the total ECC, respectively. These findings show that artificial reefs can improve the fishery resource carrying capacity and can therefore be beneficial both ecologically and economically.

Water temperature explains part of the variation in basal plasma cortisol level within and between fish species.

Within the thermal tolerance range of fish, metabolism is known to escalate with warming. Rapid thermic changes also trigger a series of physiological responses, including activation of the stress axis, producing cortisol. Fish have adapted to their environment by producing a low level of plasmatic cortisol when unstressed (basal), so that thriving in their natural temperature should not impact their basal cortisol levels. Yet, surprisingly, little is known on how temperature affects cortisol within and between fish species. Here, we conducted a phylogenetic meta-analysis to (1) test whether temperature can explain the differences in basal cortisol between species and (2) evaluate the role of temperature on differences in cortisol levels between individuals of a same species. To do this, we retrieved basal plasma cortisol data from 126 studies, investigating 33 marine and freshwater fish species, and correlated it to water temperature. Intra-species variability in basal plasma cortisol levels was further investigated in two species: the European sea bass Dicentrarchus labrax and the Nile tilapia Oreochromis niloticus. Factors such as life stage, sex and weight were also considered in the analyses. Overall, our phylogenetic analysis revealed a clear positive correlation between basal cortisol level and the temperature at which the fish live. The role of temperature has also been confirmed within D. labrax, while it failed to be significant in O. niloticus. In this paper, the influence of habitat, life stage, sex and weight on basal plasma cortisol levels is also discussed. Since some abiotic parameters were not included in the analysis, our study is a call to encourage scientists to systematically report other key factors such as dissolved oxygen or salinity to fully depict the temperature-cortisol relationship in fishes.

Impacts of marine fishing ban on the ecology of hilsa In the Nijhum Dwip Seascape in Bangladesh

Bangladesh government has imposed a 65-day marine fishing ban since 2015 to conserve marine fisheries, particularly to boost hilsa (Tenualosa ilisha) production. However, the ecological impacts of the marine fishing bans on water quality and hilsa’s growth are not assessed yet. Thus, this study aims to contribute here using data from coastal waters and fish from pre-contacted fishers in the Nijhum Dwip seascape during and outside the fishing ban in 2021 – 2022. Data were analyzed using R software. The measured mean dissolved oxygen, temperature, pH, electrical conductivity, total dissolved solids, and transparency of the sample water were 7.1 ± 1.13 mg/l, 31.1 ± 0.71°C, 8.45 ± 0.07, 40000 ± 2828 μS/cm, 18000 ± 1414 mg/L and 63.5 ± 2.12 cm at 1 week prior to the ban ends (July) and 8.45 ± 0.21 mg/l, 22.35 ± 0.49°C, 8.45 ± 0.07, 20500 ± 1060.66 μS/cm, 10350 ± 212.13 mg/l and 63.5 ± 7.78 cm before the ban starts (February). The values might be varied due to seasonal differences. The mean length (38 cm) and weight (601 g) of sampled hilsa during the ban periodwere comparatively larger than the mean length (29 cm) and weight (229 g) of hilsa which were sampled during the outside fishing ban period. Therefore, this study concludes that the marine fishing ban has positive impact on the growth and size of hilsa. This study suggests that further research is required to assess the fishing ban’s impact on the growth and production of other coastal and marine fish species across the Bay of Bengal. Dhaka Univ. J. Biol. Sci. 32(1): 33-43, 2023 (January)

DNA Barcodingof Commercial Fish Sold in MuarFish Market, Johor

Due to the high demand in the fisheries market, species identification is vital for commercial fish to avoid mislabeling and fraud in marketplaces. The increasingly threatening human activities like overfishing, blast fishing, poison fishing, and trawling have become the major threats to fish and caused an urgent need for documentation of both marine and freshwater fishes. Commercial fish products sometimes are sold by their parts, such as fins which further create confusion for identification purposes.Morphological identification also requires highly skilled ichthyologists to avoid misidentification. Thus, identification through DNA barcoding can be utilized as it holds the potential for accurate and rapid identification. Here we identified the commercial marine fish species sold in Muar Fish Market, Johor, using the Cytochrome Oxidase subunit I (COI) gene of mitochondrial DNA (mtDNA). A 700 base-pair sequence of the COI region was targeted by amplifying extracted DNA from 28 fin samples collected from the fish market. From 28 samples, we successfully sequenced 16 samples, and by using phylogenetic analysis, (Neighbor-Joining (NJ), Maximum Parsimony (MP) and Bayesian Inference (BI)) we successfully identified the samples belonging to nine families (Scombridae, Platycephalidae, Carangidae, Ariidae, Polynemidae, Coryphaenidae, Sphyraenidae, Muraenesocidae, Engraiulidae), 12 genera and 16 species. This study reports the first documentation of commercial fish sold in Muar through the DNA barcoding technique. This technique should be expanded further to identify any species with important conservation implications, such as endangered species, for improved management of fisheries in Malaysia

Length–weight Relationships of 19 Marine Fish Species from the Southern Coast of Black Sea Associated with Small-Scale Fisheries

This study presents the length-weight relationship (LWRs) estimates for 19 marine fish species belonging to 12 families from the southern coast of the Black Sea. The species were sampled using small-scale fishing gears such as gillnets and trammel nets at depths of 0-120 m from 2010 to 2021. The LWRs were calculated by the linear regression of natural log-transformed data concerning W = a × TLb. Growth type was evaluated according to Pauly’s t-test. The slope (b-value) ranged between 2.5643 and 3.5745, corresponding to the commonly expected range (2.50–3.50) except for Spicara flexuosum. The coefficient of determination values (r2) were above 0.90 except for Chromis chromis, Gobius niger, Neogobius melanostomus, Sardina pilchardus and Uranoscopus scaber. This study targeted specimens from small-scale fisheries-related gears; therefore, the results are primarily of interest to local fisheries management. The new LWRs cover substantially larger TLmax values than any previous study, and thus we can assume that all size classes of the species are adequately represented, and the new LWRs are more significant and species-specific than any previous estimate. This paper offers new insights into LWRs for the Umbrina cirrosa from the southern coast of the Black Sea.

Partial validation of a TaqMan quantitative polymerase chain reaction for the detection of the three genotypes of Infectious spleen and kidney necrosis virus.

Megalocytiviruses (MCVs) are double-stranded DNA viruses known to infect important freshwater and marine fish species in the aquaculture, food, and ornamental fish industries worldwide. Infectious spleen and kidney necrosis virus (ISKNV) is the type species within the genus Megalocytivirus that causes red seabream iridoviral disease (RSIVD) which is a reportable disease to the World Animal Health Organization (WOAH). To better control the transboundary spread of this virus and support WOAH reporting requirements, we developed and partially validated a TaqMan real-time qPCR assay (ISKNV104R) to detect all three genotypes of ISKNV, including the two genotypes that cause RSIVD. Parameters averaged across 48 experiments used a 10-fold dilution series of linearized plasmid DNA (107-101 copies), carrying a fragment of the three-spot gourami iridovirus (TSGIV) hypothetical protein revealed that the assay was linear over 7 orders of magnitude (107-101), a mean efficiency of 99.97 ± 2.92%, a mean correlation coefficient of 1.000 ± 0.001, and a limit of detection (analytical sensitivity) of ≤10 copies of TSGIV DNA. The diagnostic sensitivity and specificity for the ISKNV104R qPCR assay was evaluated and compared to other published assays using a panel of 397 samples from 21 source populations with different prevalence of ISKNV infection (0-100%). The diagnostic sensitivity and specificity for the ISKNV104R qPCR assay was 91.99% (87.28-95.6; 95% CI) and 89.8% (83.53-94.84). The latent class analysis showed that the ISKNV104R qPCR assay had similar diagnostic sensitivities and specificities with overlapping confidence limits compared to a second TaqMan qPCR assay and a SYBR green assay. This newly developed TaqMan assay represents a partially validated qPCR assay for the detection of the three genotypes of the species ISKNV. The ISKNV104R qPCR assay once fully validated, will serve as an improved diagnostic tool that can be used for ISKNV surveillance efforts and diagnosis in subclinical fish to prevent further spread of MCVs throughout the aquaculture and ornamental fish industries.

De novo transcriptomes for two species of snappers from the Western Atlantic (Lutjanus griseus and Lutjanus synagris).

Transcriptomes are appropriate resources for studying species that lack sequenced genomes, as they can serve as references for a broad suite of genetic applications, including: phylogenetic assessments, population genomics, and evaluate responses to environmental fluctuations. Here, we present the transcriptomes of two species of marine fishes of commercial and ecological relevance in the Western Atlantic: Lutjanus griseus and L. synagris. This project represents a step forward on developing genomic resources for important species of the Atlantic Ocean.

Marine top secrets: Ichthyoplankton in surface water uncover hidden knowledge on fish diversity and distribution

Most marine fish species exploit the upper water layers during their early life stages, thus accounting for a considerable component of neuston communities. During this period, the early life stages of fish are subjected to coastal or oceanic currents, and developed and dispersed to ultimate adult habitats according to their specific ecological requirements. Despite the ecological importance of these pelagic communities, knowledge about species assemblages of fish eggs and larvae, particularly in an oligotrophic sea is scarce. To overcome this knowledge gap and to evaluate the contribution of such communities to invasive biology, we collected neuston ichthyoplankton above the coastal, shelf and bathyal waters of the Eastern Mediterranean Sea (Israeli coast), an oligotrophic basin prone to a dynamic invasion of tropical biota. To obtain species-level knowledge of fish diversity, we used DNA-based methods that uncovered the presence of 137 species which is one third of the total local Osteichthyes fauna, evidencing that neuston ichthyoplankton can be significantly diverse. In addition, we showed that neuston communities can provide new knowledge regarding cryptic or rare species, and have a potential to contain new non-indigenous species, by documenting fish larvae of three unreported species for the Mediterranean Sea. Last, we posit that ichthyoplankton biomonitoring in surface water layer can provide a holistic perspective regarding fish biodiversity throughout the marine environment.

Host responses against the fish parasitizing ciliate Cryptocaryon irritans.

The parasitic ciliate Cryptocaryon irritans, which infects almost all marine fish species occurring in both tropical and subtropical regions throughout the world. The disease, cryptocaryonosis, accounts for significant economic losses to the aquaculture industry. This review attempts to provide a comprehensive overview of the biology of the parasite, host-parasite interactions and both specific and non-specific host defense mechanisms are responsible for the protection of fish against challenge infections with this ciliate. Also, this article reflects the current interest in this subject area and the quest to develop an available vaccine against the disease. Due to the high frequency of clinical fish cryptocaryonosis, the study of fish immune responses to C. irritans provides an optimal experimental model for understanding immunity against extracellular protozoa.

The Effect of Short-Term Upwelling Events on Fish Assemblages at the South-Eastern Coast of the Baltic Sea

Multiple stressors, such as overfishing, pollution, climate change, biological invasions etc., are affecting fish communities, and thus can have versatile effects on marine ecosystems and socio-economic activities as well. Understanding the changes in the fish community structure is ecologically and economically important, yet a very complex issue, requiring comprehensive analysis of multiple factors. The role of regional oceanographic variability, namely, coastal upwelling, is often neglected when it comes to the analysis of fish assemblages. In this perspective, we were aiming, for the first time in the Baltic Sea, to assess the upwelling influence on fish communities and fish community-based ecological indices used under Marine Strategy Framework Directive. The study covered a long-term period (2000–2019) for upwelling identified by satellite data analysis and fish gillnet surveys, performed in three distinct locations in the coastal waters of the SE Baltic Sea. Overall, our study revealed that temporal dynamics of fish abundance and community composition were associated with the presence of coastal upwelling. The study outcomes suggest that the fish community was more diverse and a higher number of some fish species was observed before upwelling. During upwelling, there was more evident dominance of 1–2 main marine fish species. Through the changes in fish abundance and species composition upwelling was also responsible for the changes in fish community structure-based indices for marine environment status, i.e., in the majority of the cases a decrease in Trophic, Piscivorous Fish, and Diversity indices were observed. Our study demonstrates that upwelling can affect both, the quantitative and qualitative characteristics of coastal fish communities, therefore, it is important to consider this when predicting shifts in the distribution of fish stocks or assessing environmental status indicators, especially under changing climate. We believe that our approach adds novel information to the study of coastal ecosystems of the Baltic Sea and is important for better management of socio-economic activities in the coastal zone.

Molecular Identification of Photobacterium damselae in Wild Marine Fish from the Eastern Mediterranean Sea

Infectious diseases caused by marine bacterial pathogens inflict increasing economic losses to fisheries and aquaculture, while also posing a growing risk to public health and affected species conservation. In this study, four wild marine fish species were collected at five fishing sites in Israel, divided into two regions—north (Acre, Haifa, Shefayim) and center-south (Tel-Aviv and Ashdod), and screened for Photobacterium damselae. An initial screening was carried out using PCR analysis with specifically designed primers on DNA extracted from livers and kidneys. P. damselae-positive samples had their 16S rRNA amplicons sequenced. Later, an attempt to specify relevant sub-species was performed, using a three-layered gene screen: Car, ureC and toxR. Of 334 fish samples, 47 (14%) were found to be P. damselae-positive, of which 20 were identified as P. damselae subsp. piscicida (Phdp), two as P. damselae subsp. damselae (Phdd) and 25 could not be identified to subspecies. Our results strengthen the view that fish residing in a polluted environment are receptive of pathogenic microorganisms. To assess how the presence of pathogens may affect population management and conservation, this research should be followed by studies aimed at: (i) quantifying levels of pollutants that may affect pathogen emergence, and (ii) creating a standard pollution-level index as a basis for setting criteria, above which authorities should take measures of precaution.

Assessment of Histamine Levels and Histamine-producing Bacteria in <i>Euthynnus affinis</i> Marketed in Tanga and Mtwara Coastal Areas, Tanzania

Histamine (scombrotoxin) food poisoning is a community health risk associated with consumption of some marine fish species and it has been proposed that some anaerobic bacteria contribute to this form of food poisoning. However, histamine levels and histamine producing bacteria in fish marketed in Tanzania have not been appraised. This study was conducted to determine histamine levels and histamine-producing bacteria in the <i>E. affinis</i> (tuna) value chain in Tanga and Mtwara regions. High-performance thin-layer chromatography (HPTLC) was used to determine histamine levels, Bacteriology and biochemical tests were employed to determine histamine-producing bacteria. A total of 64 tuna fish samples were collected from deep sea fish market and Sahare Tanga and ferry market, Mtwara coasts. The mean level of histamine was found to be 86.4±43.9 in Tanga and 64.8±47.5 in Mtwara and the overall mean was 77.1±46.4. All fish 64 samples were positive for histamine; however, the mean level was within the recommended limit for consumed fishery products according to European Union regulation of 200 mg/kg (m) to 400 mg/kg (m) (EC, 2005).<i> Klebsiella spp, pseudomonas spp, </i>and <i>proteus spp</i> were isolated and confirmed as histamine-producing bacteria based on bacteriology and biochemical characteristics. It concluded that although within the recommended levels, all fish samples were positive to histamine and three bacterial species associated with its production isolated. To prevent raising histamine to concern levels, maintenance of hygiene and low temperature along the production chain should be observed.

Tenacibaculosis caused by Tenacibaculum maritimum: Updated knowledge of this marine bacterial fish pathogen.

Tenacibaculosis occurs due to the marine bacterial pathogen Tenacibaculum maritimum. This ulcerative disease causes high mortalities for various marine fish species worldwide. Several external clinical signs can arise, including mouth erosion, epidermal ulcers, fin necrosis, and tail rot. Research in the last 15 years has advanced knowledge on the traits and pathogenesis mechanisms of T. maritimum. Consequently, significant progress has been made in defining the complex host-pathogen relationship. Nevertheless, tenacibaculosis pathogenesis is not yet fully understood. Continued research is urgently needed, as demonstrated by recent reports on the re-emerging nature of tenacibaculosis in salmon farms globally. Current sanitary conditions compromise the development of effective alternatives to antibiotics, in addition to hindering potential preventive measures against tenacibaculosis. The present review compiles knowledge of T. maritimum reported after the 2006 review by Avendaño-Herrera and colleagues. Essential aspects are emphasized, including antigenic and genomic characterizations and molecular diagnostic procedures. Further summarized are the epidemiological foundations of the T. maritimum population structure and elucidations as to the virulence mechanisms of pathogenic isolates, as found using biological, microbiological, and genomic techniques. This comprehensive source of reference will undoubtable serve in tenacibaculosis prevention and control within the marine fish farming industry. Lastly, knowledge gaps and valuable research areas are indicated as potential guidance for future studies.

Heavy metal concentration in marine edible fishes and associated health risks: An assessment from Tamil Nadu coast, Bay of Bengal

To assess food safety, the edible portion (muscle tissue) of the 91 different species of marine fish was studied and analyzed for metal contents. The fish samples were collected during 2017–2018 from the southwestern Bay of Bengal region at Kalpakkam coast. The hierarchy of the metals in muscle tissue was in the order of Fe > Zn > Al > Cr > Ni > Mn > Cu > Pb > Co > Cd, as reported in studied fishes. Among fish species, Lates calcarifer (469.69 mg/kg dry weight (dw) and Siganus lineatus (64.74 mg/kg dw) had the highest and lowest total metal content in their muscle tissue. Fe & Zn together contributed ̴ 70% of the total metal content of 72 fish species. The observed elevated concentrations of Al (1.96–46.6, average: 20.39 mg/kg dw) and Cr (1.93–55.24, average: 15.2 mg/kg dw) in fish compared to other regions could be attributed to localized contamination. The PCA results suggested a higher accumulation of Al, Cd, Cu, & Zn, in pelagic-neritic fishes and Co, Cr, Fe, Mn, Ni, & Pb in demersal fishes in comparison to fishes occupying other habitats. The levels of metals in fish muscle are in compliance with the maximum regulatory limit specified for fish by the Food Safety and Standards of India (FSSAI), European Commission (EC), Joint Food and Agricultural Organization of the United States/World Health Organization (FAO/WHO), suggesting that the fishes are safe for human consumption. The non-carcinogenic (estimated daily intake; target hazard quotient, hazard index) and carcinogenic risk (target cancer risk) assessment performed indicated no apparent risk to the adult consumer.

Morphological Variability of the Smelts (Osmeriformes: Osmeridae) of the Russian Far East

This paper presents the first study comparing the smallmouth smelts – the Japanese smelt Hypomesus nipponensis McAllister, 1963, the pond smelt H. olidus (Pallas, 1814), the marine smelt H. japonicus (Brevoort, 1856) – and the Asiatic smelt Osmerus dentex Steindachner et Kner, 1870 with the use of the variance of fluctuating asymmetry, the coefficient of variation, and the mean values of characters of these species. The comparison showed that the Asiatic smelt was characterized by the largest sum of dispersions of all characters, while the marine smelt had the smallest sum, which was obviously associated with more stable conditions of embryonic and early postembryonic development of the marine smelt. Japanese and pond smelts were similar in coefficients of variation for all traits. The Asiatic smelt displayed the maximum sum of coefficients of variation of all characters; while the marine smelt had the minimal sum of coefficients of variation of the characters, which may indicate relative morphological stability of this species in the range of its occurrence. A greater variability of smelts spawning in fresh water is in good agreement with the conclusion of G.V. Nikolsky et al. that the variability of traits in freshwater fish species is higher than in marine fish species. According to the average values for the characters, the four species of smelts differed only in the number of rays in the pectoral fins, while the minimum value was typical of the pond smelt, and the maximum value – for the marine smelt. The Japanese (24) and pond (26) smelts showed the minimum differences from other species, and the marine and Asiatic smelts – maximum differences (28).

A global ecological signal of extinction risk in marine ray-finned fishes (class Actinopterygii)

Abstract Many marine fish species are experiencing population declines, but their extinction risk profiles are largely understudied in comparison to their terrestrial vertebrate counterparts. Selective extinction of marine fish species may result in rapid alteration of the structure and function of ocean ecosystems. In this study, we compiled an ecological trait dataset for 8,185 species of marine ray-finned fishes (class Actinopterygii) from FishBase and used phylogenetic generalized linear models to examine which ecological traits are associated with increased extinction risk, based on the International Union for the Conservation of Nature Red List. We also assessed which threat types may be driving these species toward greater extinction risk and whether threatened species face a greater average number of threat types than non-threatened species. We found that larger body size and/or fishes with life histories involving movement between marine, brackish, and freshwater environments are associated with elevated extinction risk. Commercial harvesting threatens the greatest number of species, followed by pollution, development, and then climate change. We also found that threatened species, on average, face a significantly greater number of threat types than non-threatened species. These results can be used by resource managers to help address the heightened extinction risk patterns we found.

Morfologia e filogenia molecular das metacestodes de tripanorhynchid que infectam os peixes comerciais do Mar Mediterrâneo

ABSTRACT Members of the order Trypanorhyncha are cestode parasites that are frequently found infecting the muscles of several marine fish species, affecting fish health, and resulting in consumers’ rejection of fish. Fifty-two specimens of marine fish were freshly caught throughout the year 2020 from boat landing sites at the Alexandria coast along the Mediterranean Sea in Egypt, including the grey trigger fish Balistes carolinensis (F: Balistidae); the mottled grouper Mycteroperca rubra (F: Serranidae) and the common sole Solea vulgaris (F: Soleidae). Blastocysts were isolated and ruptured; the generated pleurocerci were described morphologically and morphometrically by light and scanning electron microscopy. Also, multiple-sequence alignment was performed, and a phylogenetic tree was constructed following maximum likelihood analysis of the 18s and 28s ribosomal RNA sequences of the recovered worms. Thirty fish were infected; the infection was recorded as blastocysts embedded in fish flesh. Three different parasitic species were recovered and classified morphologically as Gymnorhynchus isuri, Pseudotobothrium dipsacum and Heteronybelinia estigmena. The taxonomic position of these parasites was justified by molecular analysis of their 18s and 28s rRNAs, which revealed high percentages of homology with species recovered from the GenBank. The accession numbers ON157059, ON139663 and ON139662 were respectively assigned to the recovered parasites after their deposition in GenBank. The results obtained from the molecular analyses confirmed the morphological records of the recovered parasites. Since metacestodes are found in the musculature of infected fish specimens, it is necessary to remove these areas in the commercialization of fish.