Marine organisms, especially top predators such as sharks, are susceptible to environmental pollutants like microplastics (MPs) and phthalate esters (PAEs), leading to ecosystem risks. Research on contamination in these apex species is, however, still limited. This study investigated MPs and PAEs in multiple shark species (Isurus oxyrinchus, Alopias superciliosus, Alopias pelagicus, Carcharhinus brevipinna, and Sphyrna zygaena) off Taiwan\'s eastern coast. Gastric tissue analyses revealed ubiquitous microplastics (2-31 particles), which positively correlated with body lengths and weights for Isurus oxyrinchus. Blue, fiber-shaped (1-2 mm), and rayon-based MPs are likely associated with textile fiber pollution. The PAEs concentration mean was 7035 ± 6829 ng/g, ww, having DEHP and DiNP as primary compounds. This study highlights pervasive contamination in Pacific Ocean sharks, emphasizing anthropogenic impact on top oceanic predators and providing essential insights for food safety and MP accumulation.

The complex evolutionary patterns in the mitochondrial genome (mitogenome) of the most species-rich shark order, the Carcharhiniformes (ground sharks) has led to challenges in the phylogenomic reconstruction of the families and genera belonging to the order, particularly the family Triakidae (houndsharks). The current state of Triakidae phylogeny remains controversial, with arguments for both monophyly and paraphyly within the family. We hypothesize that this variability is triggered by the selection of different a priori partitioning schemes to account for site and gene heterogeneity within the mitogenome. Here we used an extensive statistical framework to select the a priori partitioning scheme for inference of the mitochondrial phylogenomic relationships within Carcharhiniformes, tested site heterogeneous CAT + GTR + G4 models and incorporated the multi-species coalescent model (MSCM) into our analyses to account for the influence of gene tree discordance on species tree inference. We included five newly assembled houndshark mitogenomes to increase resolution of Triakidae. During the assembly procedure, we uncovered a 714 bp-duplication in the mitogenome of Galeorhinus galeus. Phylogenetic reconstruction confirmed monophyly within Triakidae and the existence of two distinct clades of the expanded Mustelus genus. The latter alludes to potential evolutionary reversal of reproductive mode from placental to aplacental, suggesting that reproductive mode has played a role in the trajectory of adaptive divergence. These new sequences have the potential to contribute to population genomic investigations, species phylogeography delineation, environmental DNA metabarcoding databases and, ultimately, improved conservation strategies for these ecologically and economically important species.

The threat of population declines caused by pelagic longline fisheries in the Atlantic has increased the concern to find strategies that minimize the bycatch and mortality of non-target marine animals. Gear modification, such as the use of circle hooks instead of conventional J-hooks, has been identified as an effective bycatch reduction strategy in different pelagic longline fisheries around the world. This study aimed to verify the effectiveness of the use of circle hooks by quantifying catch rates, relative size selectivity, and anatomical hooking position for the most common target species (swordfish, Xiphias gladius, and blue shark, Prionace glauca), and some bycatch species (loggerhead sea turtles, Caretta caretta, and shortfin mako, Isurus oxyrinchus) caught by the Azorean longline fishing fleet. The trial was conducted for five consecutive years (2000-2004) using eight different types of hooks. In general, the blue shark catches using circle hooks were significantly higher compared to J (Mustad 9/0). The circle hooks also showed high probabilities of catching juvenile blue sharks. Conversely, the circle hooks were efficient in reducing the loggerhead sea turtle bycatch and were related to fewer catches of small sea turtle individuals. The use of circle hooks was also associated with reduced swordfish catches compared to J (Mustad 9/0), and the effect of hook types on length at capture was only significant for Circle (L. & P. 18/0-CLP18) and Ringed Tuna (RT). No significant differences were observed comparing hook type to either catch rates or size selectivity for shortfin mako. Additionally, circle hooks were more likely to lodge in the mouth than in deeper anatomical positions, when compared to J (Mustad 9/0), for the four species analysed. The present study demonstrated that the use of circle hooks could mitigate the impact of the pelagic longline fisheries in the Azores by decreasing the bycatch of sea turtles and reducing animal injuries caused by deep hooking.

Sharks are known to contain high levels of mercury in their meat. However, few studies have directly assessed the changes in mercury concentration in the human body according to shark meat intake. One hundred and ninety-seven participants that traditionally consume shark meat during the Chuseok holiday were recruited from two areas of Gyeongsangbuk-do, South Korea to examine their blood mercury level before and after the holiday season. Blood mercury levels were measured before and after the holiday season. Characteristics such as the consumption of shark meat, intake amount, and the effect on mercury concentration were assessed during the survey. Univariable and multivariable analysis (Linear Mixed Model) were done for assessing the association between shark meat consumption of holiday season and blood mercury level. Among the total participants, 83 consumed shark meat during holiday. In the univariable analysis, a significant increase in blood mercury levels before and after Chuseok was observed only for the group that consumed shark meat during holiday. The multivariable analysis (adjusted for identified confounders that affect both exposure and outcome considering repeated measurements) showed that consuming shark meat was significantly associated with increased blood mercury levels by 3.56 μg/L (95% confidence interval [CI], 2.64-4.67 μg/L). In the model considering the amount consumed as two group, the level of increase was 2.61 μg/L (95% CI, 1.63-3.58 μg/L) for those consuming <100 g, and 6.20 μg/L (95% CI, 4.77-7.62 μg/L) for those consuming ≥100 g compared to group without consuming shark meat. Considering amount consumed as continuous value, 0.02 μg/L (95% CI, 0.01-0.02 μg/L) of blood mercury increase was significantly associated with consuming 1 g. Consumption of shark meat significantly elevated blood mercury levels, exceeding commonly suggested reference concentrations in less than 2 weeks. These findings suggest the need for public health warnings and regulations regarding shark meat consumption.

Oviparous elasmobranch embryos (Chondrichthyes) have been the focus of several embryological studies; they are useful models for studying early ontogeny in vertebrates, as can help explore the existence of common developmental patterns among species. Skates (Rajiformes) are the most speciose order of oviparous elasmobranchs, however, few studies are focused on embryo development and only based on one skate family: Rajidae. Here, we extended the study of embryo development to other skate family, Arhynchobatidae, which represent about 1/3 of all skate species. Three adult female bignose fanskates (Sympterygia acuta) were held in captivity in order to provide the first complete embryonic development timeline for any species within the Arhynchobatidae family. Our results allowed further comparisons at the embryonic scale of different oviparous elasmobranch families, providing an updated cross-species overview of the early ontogeny. Incubation in S. acuta lasted 97 ± 1.4 days at 11-21.7 °C, and hatching size was 93.2 ± 0.2 mm in total length and 49.2 ± 0.3 mm in disc width. Early embryos of S. acuta were anatomically similar to other oviparous elasmobranch embryos, with several structures appearing at the same time, but late embryonic development was comparatively delayed. The late resorption of both the external yolk sac and the external gill filaments, and also the delay in the slit opening could indicate a low metabolic demand in S. acuta, which would probably be coupled with its seasonal reproductive cycle. Some structures such as external gill filaments and claspers appeared at a similar time in some species of Rajidae and also in Arhynchobatidae, but at different times in species of the same family, showing an inconsistency also found within shark families. Although the sequential scheme remained relatively constant, small heterochronies would be present within skates, within sharks, and also between skates and sharks.

The \"blue shark\", Prionace glauca (class: Chondrichthyes), is a pelagic shark species commonly found in tropical and temperate oceans. This shark is mainly sold in Asian countries as food and as traditional Chinese medicine. According to the Red List of the International Union for the Conservation of Nature, P. glauca is classified as low-risk to near endangered. P. glauca cartilage contains collagen type II, which makes it suitable as a bioactive ingredient in cosmeceutical products. This study evaluated the effects of a gel containing various concentrations (0.125-5%) of lyophilized hydrolyzed P. glauca cartilage on the human inner wrist skin compared to a placebo (base). A skin properties evaluation test was conducted before and after applying various concentrations (0.125-5%) of the P. glauca cartilage gel for 10 and 20 min on the inner wrists of participants using a skin analyzer that determined the moisture level, oil level, texture level, complexion level, and the 3D level. Adding lyophilized hydrolyzed shark cartilage (LHSC) significantly improved the moisture, texture, and complexion of the skin while controlling oil and providing a wrinkle-smoothing effect. The result indicated that LHSC formulations were prepared at different concentrations, and they had significantly enhanced effects on skin hydration and elasticity (texture) and the smoothing of wrinkles (3D level). The LHSC also effectively controlled oil secretion and the complexion.

Oral denticles of sharks are composed by a crown, dentine covered by a layer of enameloid and pulp cavity, the same structure of the dermal denticles found across the body surface of most elasmobranchs. In addition, oral papillae and taste buds are distributed among denticles within the oropharyngeal cavity, playing a fundamental role for tasting as part of the chemosensory system of fishes. Scanning electron microscopy (SEM) has been employed as an important tool for the study of dermal denticles and other structures, as well as histology and more recently computed tomography (CT) scan analysis. Herein, the authors used two methods for the study of the morphology of the oropharyngeal cavity of Lamna nasus (Lamniformes), an oceanic and pelagic shark: SEM and CT scan. The general morphology of oral denticles studied herein is related to abrasion strength as they are diamond-shaped, lack lateral cusps and have less pronounced ridges. In addition, smooth ridges and broad rounded denticles could be related to prevent abrasion during food consumption and manipulation. Oral papillae had a round shape and were observed only under SEM. The densities of papillae were estimated in 100 per cm2 , whereas denticles were 1760 and 1230 cm2 over the dorsal and ventral regions, respectively. The high numbers of denticles are inversely proportional to papillae density; denticles seem to restrict papillae distribution. Regarding the differences between methodologies, under SEM, only the crown was visualized, as well the papillae, allowing the estimation of size and density of both structures. Nonetheless, under CT scan, the whole components of denticles were clearly visualized: different views of the crown, peduncle, basal plate, and pulp cavity. On the contrary, oral papillae were not visualized under CT due to the tissue preparation. Furthermore, both methods are complementary and were important to extract as much information as possible from denticles and papillae.

Metal contamination has never been assessed in Ampullae of Lorenzini. This study employed Rhizoprionodon lalandii, as an ecotoxicological model to investigate potential metal accumulation in Ampullae of Lorenzini jelly. No differences between sexes were observed regarding jelly metal concentrations at Rio das Ostras (RJ) or Santos (SP). Statistically significant correlations were noted between total lengths (TL) and condition factors and several metals at both sampling sites, demonstrating the potential for Chondrichthyan sensory capacity disruption and possible effects on foraging success. Maternal metal transfer to Ampullae jelly was confirmed. Rhizoprionodon lalandii is thus, a good model to assess Ampullae of Lorenzini contamination, as this electrosensory organ seems to be highly vulnerable to metal contamination.

During development of the olfactory bulb (OB), glial cells play key roles in axonal guiding/targeting, glomerular formation and synaptic plasticity. Studies in mammals have shown that radial glial cells and peripheral olfactory glia (olfactory ensheathing cells, OECs) are involved in the development of the OB. Most studies about the OB glia were carried out in mammals, but data are lacking in most non-mammalian vertebrates. In the present work, we studied the development of the OB glial system in the cartilaginous fish Scyliorhinus canicula (catshark) using antibodies against glial markers, such as glial fibrillary acidic protein (GFAP), brain lipid-binding protein (BLBP), and glutamine synthase (GS). These glial markers were expressed in cells with radial morphology lining the OB ventricle of embryos and this expression continues in ependymal cells (tanycytes) in early juveniles. Astrocyte-like cells were also observed in the granular layer and surrounding glomeruli. Numerous GS-positive cells were present in the primary olfactory pathway of embryos. In the developmental stages analysed, the olfactory nerve layer and the glomerular layer were the regions with higher GFAP, BLBP and GS immuno-reactivity. In addition, numerous BLBP-expressing cells (a marker of mammalian OECs) showing proliferative activity were present in the olfactory nerve layer. Our findings suggest that glial cells of peripheral and central origin coexist in the OB of catshark embryos and early juveniles. These results open the path for future studies about the differential roles of glial cells in the catshark OB during embryonic development and in adulthood.

Wild animals are under selective pressure to optimise energy budgets; therefore, quantifying energy expenditure, intake and allocation to specific activities is important if we are to understand how animals survive in their environment. One approach toward estimating energy budgets has involved measuring oxygen consumption rates under controlled conditions and constructing allometric relationships across species. However, studying \'giant\' marine vertebrates (e.g. pelagic sharks, whales) in this way is logistically difficult or impossible. An alternative approach involves the use of increasingly sophisticated electronic tags that have allowed recordings of behaviour, internal states and the surrounding environment of marine animals. This Review outlines how we could study the energy expenditure and intake of free-living ocean giants using this \'biologging\' technology. There are kinematic, physiological and theoretical approaches for estimating energy expenditure, each of which has merits and limitations. Importantly, tag-derived energy proxies can hardly be validated against oxygen consumption rates for giant species. The proxies are thus qualitative, rather than quantitative, estimates of energy expenditure, and have more limited utilities. Despite this limitation, these proxies allow us to study the energetics of ocean giants in their behavioural context, providing insight into how these animals optimise their energy budgets under natural conditions. We also outline how information on energy intake and foraging behaviour can be gained from tag data. These methods are becoming increasingly important owing to the natural and anthropogenic environmental changes faced by ocean giants that can alter their energy budgets, fitness and, ultimately, population sizes.