Transition from endogenous to exogenous feeding in longfin yellowtail Seriola rivoliana larvae under simultaneous effects of daily temperature fluctuation and rotifer Brachionus rotundiformis enrichment.

Temperature and nutrition are suggested as the primary factors affecting larval survival during the transition from endogenous to exogenous feeding in fish. However, little is known about its simultaneous impact during this period. In this study, Seriola rivoliana eggs were subjected to a constant 24 °C (CTE) and a daily temperature fluctuation (DTF) between 22.8 and 25.2 °C until oil droplet exhaustion (5.5 days after hatching). On the other hand, marine fish larvae mostly rely on live feed, with certain nutritional deficiencies such as poor long-chain fatty acids. Thus, rotifer Brachionus rotundiformis enrichment was simultaneously evaluated with temperature using three enrichment diets: Ori-green, S.presso, and a Domestic emulsion. For this purpose, the five experimental groups were established in triplicate using six 100-L tanks with three 10-L containers inside (18 experimental units in total). One hundred eggs were incubated, using a green water system, and 10 rotifers mL-1 were offered at mouth opening. After oil droplet exhaustion, survival was only affected by temperature (P < 0.01), being higher at DTF compared to CTE. At the same stage, Domestic emulsion resulted in bigger larvae than Ori-green. In a further assay at 3.7 DAH, the relative expression of the trypsin gene was higher at Domestic emulsion compared to S.presso and Ori-green. This study indicates that daily temperature fluctuation can improve larval performance and low levels of EPA and DHA in Domestic emulsion enriched rotifers were not critical for Seriola rivoliana at first feeding.

Oil spill impact on Brazilian coral reefs based on seawater polycyclic aromatic hydrocarbon contamination, biliary fluorescence and enzymatic biomarkers in damselfish Stegastes fuscus (Teleostei, Pomacentridae).

The crude oil contamination along the Brazilian Northeast coast significantly impacted reef ecosystems. This study assessed polycyclic aromatic hydrocarbons (PAHs) in seawater, fluorescence of bile PAHs, and biochemical biomarkers in damselfish Stegastes fuscus across four coral reef areas pre- and post-oil contamination. Serrambi (SE) and Japaratinga (JP1) were identified as suitable reference areas. PAH concentrations significantly increased in water post-contamination, predominantly 2 to 3 ring parent and alkylated PAHs. Biliary PAHs naphthalene, phenanthrene, chrysene, pyrene and benzo(a)pyrene increased on Paiva post-spill versus pre-spill to 173 %, 449 %, 334 %, 331 % and 131 %, respectively. Significant increases in ethoxy-resorufin-O-deethylase (EROD) (852 %), catalase (CAT) (139 %) and decrease in lipid peroxidation (LPO) (40 %) and acetylcholinesterase (AChE) (75 %) were verified in Paiva samples. Biliary PAHs and biochemical biomarkers were altered in S. fuscus after exposure to PAHs dissolved from the oil. Stegastes fuscus emerges as a promising sentinel organism for coastal reef oil pollution monitoring.

Paronatrema davidbowiei n. sp. (Trematoda: Syncoeliidae), a new parasite of the pelagic thresher (Alopias pelagicus) and its phylogenetic relationships within the suborder Hemiurata Skrjabin & Guschanskaja, 1954.

A new species of hemiurid trematode found on the gills and in the aorta of the pelagic thresher Alopias pelagicus from the eastern Pacific, off Costa Rica, is described based on an integrative taxonomic approach that includes the use of light and scanning electron microscopy, and 28S rDNA sequencing. Phylogenetic analysis was also performed to explore, for the first time, the relationships of a member of the subfamily Otiotrematinae within the suborder Hemiurata. Paronatrema davidbowiei n. sp. can be distinguished from the congeners by having tegumental spines on the dorsal surface of the forebody, papillae on the oral sucker, and different morphology or number of testicular follicles. BLAST analysis revealed that sequences of Paronatrema davidbowiei n. sp. had the highest degree of similarity with Hirudinella spp. (Hirudinellidae). Results from Maximum Likelihood and Bayesian phylogenetic analyses, returning trees with the exact same topology and strong branch support, distinguished between the two superfamilies included in the suborder Hemiurata: Azygioidea and Hemiuroidea. Our analysis placed the new species in a clade with Copiatestes filiferus, the only existing sequence of the family Syncoeliidae.

The Abrolhos Nominally Herbivorous Coral Reef Fish Acanthurus chirurgus, Kyphosus sp., Scarus trispinosus, and Sparisoma axillare Have Similarities in Feeding But Species-Specific Microbiomes.

Coral reefs rely heavily on reef fish for their health, yet overfishing has resulted in their decline, leading to an increase in fast-growing algae and changes in reef ecosystems, a phenomenon described as the phase-shift. A clearer understanding of the intricate interplay between herbivorous, their food, and their gut microbiomes could enhance reef health. This study examines the gut microbiome and isotopic markers (δ13C and δ15N) of four key nominally herbivorous reef fish species (Acanthurus chirurgus, Kyphosus sp., Scarus trispinosus, and Sparisoma axillare) in the Southwestern Atlantic's Abrolhos Reef systems. Approximately 16.8 million 16S rRNA sequences were produced for the four fish species, with an average of 317,047 ± 57,007 per species. Bacteria such as Proteobacteria, Firmicutes, and Cyanobacteria were prevalent in their microbiomes. These fish show unique microbiomes that result from co-diversification, diet, and restricted movement. Coral-associated bacteria (Endozoicomonas, Rhizobia, and Ruegeria) were found in abundance in the gut contents of the parrotfish species Sc. trispinosus and Sp. axillare. These parrotfishes could aid coral health by disseminating such beneficial bacteria across the reef. Meanwhile, Kyphosus sp. predominantly had Pirellulaceae and Rhodobacteraceae. Four fish species had a diet composed of turf components (filamentous Cyanobacteria) and brown algae (Dictyopteris). They also had similar isotopic niches, suggesting they shared food sources. A significant difference was observed between the isotopic signature of fish muscular gut tissue and gut contents, pointing to the role that host genetics and gut microbes play in differentiating fish tissues.

Preparation and characterization of sustainable active packaging based on myofibrillar proteins and protein hydrolysates from the cutting by-product of Scomberomorus brasiliensis filleting on the band saw machine.

Protein hydrolysates derived from aquaculture by-products hold significant promise as key components in the formulation of active films. In our study, we investigated the impact of different protein hydrolysates levels (0.4%, 0.8%, and 1.2%) obtained from the cutting by-product of Serra Spanish mackerel on the mechanical (PHSSM), morphological, optical, thermal, and antioxidant properties, as well as the degradability of biodegradable films. Four treatments were produced, varying the concentrations of PHSSM: C (control, without PHSSM), T4 (with 0.4% PHSSM), T8 (with 0.8% PHSSM), and T12 (with 1.2% PHSSM). These films were based on myofibrillar proteins from fish by-products and pectin extracted from yellow passion fruit. The incorporation of PHSSM led to enhanced barrier properties, resulting in a proportional reduction in water vapor permeability compared to the control film. However, high PHSSM levels (>0.8%) compromised film homogeneity and increased fracture susceptibility. Tensile strength remained unaffected (p > 0.05). PHSSM-enriched films exhibited reduced transparency and lightness, regardless of PHSSM concentration. The addition of PHSSM imparted a darker, reddish-yellow hue to the films, indicative of heightened visible light barrier properties. Moreover, increased PHSSM content (0.8% and 1.2%) appeared to accelerate film degradation in soil. Fourier transform infrared spectroscopy confirmed the presence of pectin-protein complexes in the films, with no discernible differences among the treated samples in the spectra. Incorporating PHSSM also enhanced film crystallinity and thermal resistance. Furthermore, an improvement in the antioxidant activity of the films was observed with PHSSM addition, dependent on concentration. The T8 emerged as the promising candidate for developing active primary packaging suitable for oxidation-sensitive foods.

METAZOAN PARASITE COMMUNITY OF THE YELLOW SNAPPER LUTJANUS ARGENTIVENTRIS: FACTORS THAT INFLUENCING SPECIES COMPOSITION AND RICHNESS.

A total of 366 individuals of Lutjanus argentiventris (Peters, 1869) were collected over a 5-yr period (October 2018 to June 2022) from Acapulco Bay, Mexico. Parasite communities in Lutjanus argentiventris were quantified and analyzed to determine the main factors that generate changes in species richness and/or species composition over time. The digeneans and copepods were the best-represented parasite groups. The parasite communities were characterized by a high numerical dominance of ectoparasites, mainly isopod larvae. Species richness at the component community level (9-23 species) was similar to the reported richness in other Lutjanus spp. The parasite communities of Lutjanus argentiventris exhibited high variability in species composition, suggesting that each parasite species may respond differently to environmental changes. However, the species richness and diversity were fairly stable over time; therefore, a clear pattern of interannual variation was not observed. Variations in the community structure probably were due to factors such as host traits (e.g., feeding behavior and body size), and possible interannual differences in environmental factors amplified by the occurrence of the anomalous event of La Niña.

Gobionellus stomatus Starks 1913 (Oxudercidae: Gobionellinae): range extension for the coastal zone of the Brazilian Amazon region.

Gobionellus stomatus, a fish species endemic to Brazil, was previously known to occur from the State of Piauí to the State of Rio Grande do Sul. Here we present the first record of this species for the State of Maranhão, specifically for the Upaon-Açu island, extending its distribution further west, to the coastal zone of the Amazon region. This species inhabits estuarine ecosystems susceptible to environmental pressures, such as pollution and the introduction of non-native species. Despite G. stomatus being classified as of least concern for conservation, it is crucial to highlight potential risks associated with human activities in these environments, emphasizing the importance of preservation measures to mitigate future impacts on the populations of this species, as well as of other estuarine gobies.

Contaminants of Emerging Concern (CECs): Assessment of health and dietary risk in the consumption of Plagioscion squamosissimus in one of the largest rivers in a semi-arid region (Rio São Francisco, Brazil).

The São Francisco River, significant in semi-arid areas, faces impacts from hydroelectric plants and agricultural pesticides. Despite extensive research on its aquatic life, especially fish reproductive biology, there's a notable lack of studies on toxicity and its human health implications. This gap highlights the need for targeted research in this vital ecological zone. Consequently, this study aimed to scrutinize the concentrations of Contaminants of Emerging Concern (CECs), including Polychlorinated Biphenyls (PCBs), Polybrominated Diphenyl Ethers (PBDEs), Organochlorine Pesticides (OCPs), pyrethroid pesticides (PPs), triazine pesticides (TPs), and Organophosphorus Pesticides (OPPs) in the water, sediment, and fish (Plagioscion squamosissimus). The findings revealed the presence of all compound classes in sediment, albeit in limited quantities in water. Biotic components exhibited higher concentrations in nerve tissue, followed by the liver and muscle, indicative of a bioaccumulation trend. It is noteworthy that more concerning levels were observed in both water and sediments. In particular, Fenvalerate in water and Prometon in sediments demonstrated the highest Bioaccumulation Factor (BAF) values. While for non-carcinogenic effects and Cancer Risk (CR), the parameters were calculated and all classified in the areas of acceptable or insignificant according to chemical safety agencies. However, the compounds under scrutiny demand vigilant attention, given their nearly ubiquitous presence across various matrices and demonstrated bioaccumulative capacity, potentially posing future repercussions for human health.

PREVALENCE OF OPECOELID TREMATODES (TREMATODA: DIGENEA: OPECOELIDAE) IN THE WOOLLY SCULPIN CLINOCOTTUS ANALIS FROM THE PACIFIC COAST OF THE BAJA CALIFORNIA PENINSULA.

Prevalence values for 3 digenean species of the family Opecoelidae were calculated during a half-year period from 20 individuals per month of the fish species Clinocottus analis, collected from an intertidal environment of Baja California, Mexico. Trematode species recovered were Opecoelus adsphaericus, Opecoelus cameroni, and Opecoelus pacificus. Of these, only O. adsphaericus was present throughout the study, whereas O. pacificus and O. cameroni were recorded for 1 or 2 mo, respectively, exhibiting relatively low prevalence values. The decrease in prevalence of O. adsphaericus coincides with the appearance of O. pacificus and O. cameroni; these last 2 species were found only in the largest hosts, and their presence represents new records for Mexican marine fauna.

Caribbean red snapper fishing performance indicators in Brazilian amazon shelf: Is it the beginning of the end of a fishing system?

Red snapper fishing (Lutjanus purpureus) is an important fishing activity for the Brazilian economy due to its export. The scarcity of up-to-date information on this system's ecology, economy, and social characteristics contributes to inefficient management. We analyze whether the commercial snapper fishery on the Amazon continental shelf is socioecologically sustainable. For this, an assessment tool was used that can be applied to fishing systems with little data, the Fisheries Performance Indicators (FPI). The results showed that the critical points of this activity are mainly related to the Ecological indicator (2.3) and the Economic indicator (2.8). The best indicator was the Community (3.8). The problems that put at risk the permanence of the activity and its maintenance are: (i) fishing for juveniles; (ii) illegal vessels; (iii) lack of collaboration of the fishing sector with science, and (iv) unreliability of data supplied. All the points mentioned make the snapper fishery on the north coast of Brazil socio-ecologically unsustainable in the long term.

Distinctive color variation in Rhinolepadichthys geminus (Gobiesocidae: Diademichthyinae) from Alor Islands, Indonesia: morphological and molecular insights.

Rhinolepadichthys geminus, one of three recently described species in the genus Rhinolepadichthys (previously known as Lepadichthys lineatus complex), is characterized by several distinct diagnostic morphological and color features, including a pair of yellow stripes on the body ventral midline. However, one of three specimens recently collected from the Alor Islands, Indonesia, possessed a yellow circular line, instead of a pair of yellow stripes, indicating that the latter were not an invariable feature. Morphological and molecular evidence confirmed the identity of the specimen and intraspecific significance of the color variation.

Unveiling the reproductive and migrative behavior of Trichiurus lepturus in a tropical environment: Insights and implications.

This study aimed to understand the reproductive biology and migrative behavior of the largehead hairtail Trichiurus lepturus in a tropical area, specifically off Pernambuco coast, northeastern Brazil. Commercial catches from fish corrals provided samples for analysis, including measurements, weight recording, and examination of gonads to determine its maturation stage. Reproductive analyses were performed, such as sex ratio, gonado-somatic index, and sizes at first maturity. There was a slightly higher proportion of females among the 141 largehead hairtail specimens analysed. No significant differences were observed in length distributions between males and females. However, during the winter, significant differences were observed in length distributions for grouped sexes. The species exhibited a seasonal migratory pattern, with a higher presence on the continental shelf during the winter. The study identified strategic allocation of energy in feeding activities and temporal spacing of reproductive cycles, as indicated by the sex ratio and abundance of individuals during different seasons. Fish corrals probably do not harm largehead hairtail population off the southwestern Atlantic tropical coast, with minimal capture of individuals below the size of first maturity. The insights of the study into reproductive and migration patterns contribute to future assessments and management strategies for this species and corral fisheries.

Temperature and immune challenges modulate the transcription of genes of the ubiquitin and apoptosis pathways in two high-latitude Notothenioid fish across the Antarctic Polar Front.

Thermal variations due to global climate change are expected to modify the distributions of marine ectotherms, with potential pathogen translocations. This is of particular concern at high latitudes where cold-adapted stenothermal fish such as the Notothenioids occur. However, little is known about the combined effects of thermal fluctuations and immune challenges on the balance between cell damage and repair processes in these fish. The aim of this study was to determine the effect of thermal variation on specific genes involved in the ubiquitination and apoptosis pathways in two congeneric Notothenioid species, subjected to simulated bacterial and viral infections. Adult fish of Harpagifer bispinis and Harpagifer antarcticus were collected from Punta Arenas (Chile) and King George Island (Antarctica), respectively, and distributed as follows: injected with PBS (control), LPS (2.5 mg/kg) or Poly I:C (2 mg/kg) and then submitted to 2, 5 and 8 °C. After 1 week, samples of gills, liver and spleen were taken to evaluate the expression by real-time PCR of specific genes involved in ubiquitination (E3-ligase enzyme) and apoptosis (BAX and SMAC/DIABLO). Gene expression was tissue-dependent and increased with increasing temperature in the gills and liver while showing an opposite pattern in the spleen. Studying a pair of sister species that occur across the Antarctic Polar Front can help us understand the particular pressures of intertidal lifestyles and the effect of temperature in combination with biological stressors on cell damage and repair capacity in a changing environment.

Combining population genomics and biophysical modelling to assess connectivity patterns in an Antarctic fish.

Connectivity is a fundamental process of population dynamics in marine ecosystems. In the last decade, with the emergence of new methods, combining different approaches to understand the patterns of connectivity among populations and their regulation has become increasingly feasible. The Western Antarctic Peninsula (WAP) is characterized by complex oceanographic dynamics, where local conditions could act as barriers to population connectivity. Here, the notothenioid fish Harpagifer antarcticus, a demersal species with a complex life cycle (adults with poor swim capabilities and pelagic larvae), was used to assess connectivity along the WAP by combining biophysical modelling and population genomics methods. Both approaches showed congruent patterns. Areas of larvae retention and low potential connectivity, observed in the biophysical model output, coincide with four genetic groups within the WAP: (1) South Shetland Islands, (2) Bransfield Strait, (3) the central and (4) the southern area of WAP (Marguerite Bay). These genetic groups exhibited limited gene flow between them, consistent with local oceanographic conditions, which would represent barriers to larval dispersal. The joint effect of geographic distance and larval dispersal by ocean currents had a greater influence on the observed population structure than each variable evaluated separately. The combined effect of geographic distance and a complex oceanographic dynamic would be generating limited levels of population connectivity in the fish H. antarcticus along the WAP. Based on this, population connectivity estimations and priority areas for conservation were discussed, considering the marine protected area proposed for this threatened region of the Southern Ocean.

Karyotypic changes and diversification time in Epinephelidae groupers (Perciformes). Implications on reproductive isolation.

Groupers (Epinephelidae and Serranidae) have attracted special attention to fish farming, and their species offer good opportunities for successful hybridizations. Cytogenetic data allow a better understanding of the role of karyotypic diversification in the acquisition of post-zygotic reproductive isolation (RI). Thus, chromosomal analyses were performed on E. striatus (Caribbean Sea), E. coioides and E. tauvina (Indo-Pacific Region), using standard procedures and mapping of six repetitive DNA classes by the in situ hybridization. The three species have 2n=48 chromosomes. The karyotypes of E. coioides and E. striatus are composed only of acrocentric chromosomes (FN=48), while E. tauvina has 8 submetacentric chromosomes (FN=56). Heterochromatin has a preferential centromeric distribution, and the microsatellite repeats are dispersed throughout the chromosomes of all species. The 18S and 5S rDNA sites are unique but show a colocalization arrangement in E. tauvina and E. striatus. The chromosomal organization suggests that the three species still maintain a significant amount of syntenic regions. The range of the karyotype divergence and the RI levels showed low, but goes turn proportionally greater in relation to the divergence time between the parental species. The slow acquisition of postzygotic RI is consistent with the high karyotype homogeneity presented by Epinephelidae family.

The white grunt, Haemulon plumierii (Lacepède, 1801) as paratenic and definitive host of two acanthocephalan species, with the description of a new species of Dollfusentis (Palaeacanthocephala: Leptohynchoididae) from the Yucatán Peninsula, Mexico.

Acanthocephalans are a group of obligate endoparasites that alternate between vertebrates and invertebrates to complete their life cycles. Occasionally, the same individual host acts as a definitive or paratenic host for different acanthocephalan species. In this study, acanthocephalans were sampled in marine fish in three localities of the Yucatán Peninsula; adults and cystacanths were recovered from the intestine and body cavity, respectively, of Haemulon plumierii from off the coast of Sisal, Yucatán. Ribosomal DNA sequences (small and large subunits) were used to test the phylogenetic position of the species of the genus Dollfusentis, whereas the mtDNA gene cox 1 was used for assessing species delimitation. The cox 1 analysis revealed an independent genetic lineage, which is recognized herein as a new species, Dollfusentis mayae n. sp. The new species is morphologically distinguished from the other six congeners by having a cylindrical proboscis armed with 22-25 longitudinal rows bearing 12 hooks each. The cystacanths were morphologically identified as Gorgorhynchus medius by having a cylindrical trunk covered with tiny irregular spines on the anterior region, and a cylindrical proboscis armed with 17-18 longitudinal rows of 21 hooks each; small and large subunit phylogenetic analyses yielded G. medius within the family Isthomosacanthidae, suggesting that Gorgorhynchus should be transferred to this family from Rhadinorhynchidae where it is currently allocated.

Unveiling the co-phylogeny signal between plunderfish Harpagifer spp. and their gut microbiomes across the Southern Ocean.

Understanding the factors that sculpt fish gut microbiome is challenging, especially in natural populations characterized by high environmental and host genomic complexity. However, closely related hosts are valuable models for deciphering the contribution of host evolutionary history to microbiome assembly, through the underscoring of phylosymbiosis and co-phylogeny patterns. Here, we propose that the recent diversification of several Harpagifer species across the Southern Ocean would allow the detection of robust phylogenetic congruence between the host and its microbiome. We characterized the gut mucosa microbiome of 77 individuals from four field-collected species of the plunderfish Harpagifer (Teleostei, Notothenioidei), distributed across three biogeographic regions of the Southern Ocean. We found that seawater physicochemical properties, host phylogeny, and geography collectively explained 35% of the variation in bacterial community composition in Harpagifer gut mucosa. The core microbiome of Harpagifer spp. gut mucosa was characterized by a low diversity, mostly driven by selective processes, and dominated by a single Aliivibrio Operational Taxonomic Unit (OTU) detected in more than 80% of the individuals. Nearly half of the core microbiome taxa, including Aliivibrio, harbored co-phylogeny signal at microdiversity resolution with host phylogeny, indicating an intimate symbiotic relationship and a shared evolutionary history with Harpagifer. The clear phylosymbiosis and co-phylogeny signals underscore the relevance of the Harpagifer model in understanding the role of fish evolutionary history in shaping the gut microbiome assembly. We propose that the recent diversification of Harpagifer may have led to the diversification of Aliivibrio, exhibiting patterns that mirror the host phylogeny. IMPORTANCE: Although challenging to detect in wild populations, phylogenetic congruence between marine fish and its microbiome is critical, as it highlights intimate associations between hosts and ecologically relevant microbial symbionts. Our study leverages a natural system of closely related fish species in the Southern Ocean to unveil new insights into the contribution of host evolutionary trajectory on gut microbiome assembly, an underappreciated driver of the global marine fish holobiont. Notably, we unveiled striking evidence of co-diversification between Harpagifer and its microbiome, demonstrating both phylosymbiosis of gut bacterial communities and co-phylogeny of some specific bacterial symbionts, mirroring the host diversification patterns. Given Harpagifer's significance as a trophic resource in coastal areas and its vulnerability to climatic and anthropic pressures, understanding the potential evolutionary interdependence between the hosts and its microbiome provides valuable microbial candidates for future monitoring, as they may play a pivotal role in host species acclimatization to a rapidly changing environment.

Low similarity between parasite communities of ten sympatric carangid species.

Host phylogeny and ecological convergence are two factors thought to influence the structure of parasite communities. The aims of this study were to determine the diversity of metazoan parasites of 10 sympatric fish species of the family Carangidae from the southeastern Gulf of California, and to analyze their similarity at infracommunity and component community levels, in order to determine if the host species, particularly those congeneric with similar ecological characteristics, exhibit similar assemblages of parasites. In total, 874 fish specimens were examined and 40 parasite species were identified. The component community was composed by 21 parasite species in Caranx caninus, 20 in C. caballus, 11 in C. vinctus, five in Chloroscombrus orqueta, four in Carangoides otrynter, seven in Hemicaranx leucurus, eight in Selene brevoortii, 14 in S. peruviana, and 11 in Trachinotus rhodopus. The metazoan parasite communities of C. vinctus, Ch. orqueta, H. leucurus, and S. brevoortii are reported here for the first time. The parasite communities of the remaining six carangid species have been reported from regions other than the Gulf of California. All fish species differed significantly regarding the diversity of their parasite infracommunities. This possibly is due to different patterns of habitat use among fish species, and because of the differential host specificity among parasite taxa. Nonetheless, when the analysis was restricted to common parasite species, some fish showed similar parasite infracommunities, particularly congeners of the genus Selene as well as C. caballus and C. vinctus. The component communities of species of Selene were highly similar (>65%), but the three species of Caranx were not. This result supports the hypothesis that congeneric fish species with similar ecological filters harbor similar parasite communities. However, the difference observed between C. caninus and C. caballus suggests that these species, despite being evolutionary and ecologically related, have different physiological or immunological characteristics (compatibility filters) that may result in different parasite communities.

Characterization of Sodium Channel Peptides Obtained from the Venom of the Scorpion Centruroides bonito.

Five peptides were isolated from the venom of the Mexican scorpion Centruroides bonito by chromatographic procedures (molecular weight sieving, ion exchange columns, and HPLC) and were denoted Cbo1 to Cbo5. The first four peptides contain 66 amino acid residues and the last one contains 65 amino acids, stabilized by four disulfide bonds, with a molecular weight spanning from about 7.5 to 7.8 kDa. Four of them are toxic to mice, and their function on human Na+ channels expressed in HEK and CHO cells was verified. One of them (Cbo5) did not show any physiological effects. The ones toxic to mice showed that they are modifiers of the gating mechanism of the channels and belong to the beta type scorpion toxin (ß-ScTx), affecting mainly the Nav1.6 channels. A phylogenetic tree analysis of their sequences confirmed the high degree of amino acid similarities with other known bona fide ß-ScTx. The envenomation caused by this venom in mice is treated by using commercially horse antivenom available in Mexico. The potential neutralization of the toxic components was evaluated by means of surface plasmon resonance using four antibody fragments (10FG2, HV, LR, and 11F) which have been developed by our group. These antitoxins are antibody fragments of single-chain antibody type, expressed in E. coli and capable of recognizing Cbo1 to Cbo4 toxins to various degrees.

Halichoeres sanchezi n. sp., a new wrasse from the Revillagigedo Archipelago of Mexico, tropical eastern Pacific Ocean (Teleostei: Labridae).

A new labrid fish species, Halichoeres sanchezi n. sp., is described from eight specimens collected in the Revillagigedo Archipelago in the tropical eastern Pacific Ocean, off the coast of Mexico. The new species belongs to the Halichoeres melanotis species complex that is found throughout the region, differing by 2.4% in the mtDNA cytochrome c oxidase I sequence from its nearest relative, H. melanotis from Panama, and 2.9% from Halichoeres salmofasciatus from Cocos Island, off Costa Rica. The complex is distinguished from others in the region by having a black spot on the opercular flap and a prominent black area on the caudal fin of males. The juveniles and initial phase of the new species closely resemble those of H. salmofasciatus and Halichoeres malpelo from Malpelo Island of Colombia, differing in having an oblong black spot with a yellow dorsal margin on the mid-dorsal fin of initial-phase adults as well as on juveniles. In contrast, the terminal-phase male color pattern is distinct from other relatives, being vermilion to orangish brown with dark scale outlines, a white patch on the upper abdomen, and a prominent black band covering the posterior caudal peduncle and base of the caudal fin. The new species adds to the list of endemic fish species for the isolated archipelago and is an interesting case of island endemism in the region. The discovery was made during the joint 2022 collecting expedition to the archipelago, which featured a pioneering collaborative approach to an inventory of an island ichthyofauna, specifically including expert underwater photographers systematically documenting specimens in situ, before hand-collection, and then photographed fresh, tissue-sampled, and subsequently vouchered in museum collections.