Carcharias Taurus Research Articles

Novel adomavirus associated with proliferative skin lesions affecting the dermal denticles of a sand tiger shark (Carcharias taurus).

A captive sand tiger shark (Carcharias taurus) presented with progressive, hard, raised, miliary skin lesions localized to the lateral trunk and peduncle. Histopathologic evaluation of biopsy samples revealed dysplastic proliferation of odontogenic epithelium with the production of collagenous material. Inclusion bodies and viral particles were not observed with light or transmission electron microscopy, respectively. However, using next generation sequencing with Illumina MiSeq and PCR followed by Sanger sequencing, the complete genome of a novel adomavirus, tentatively named sand tiger shark adomavirus (STAdoV), was obtained from the affected tissue. The genome was circular and 18.5 kilobases with bidirectionally transcribed genes, namely EO1, EO2 & 4, EO3, LO4, LO5, LO6, LO7, LO8, and SET. In situ hybridization using RNAscope® technology and a STAdoV specific probe localized viral DNA to the nuclei of proliferating epithelial cells. Adomaviruses are an emerging viral group with structural and replicative genes sharing a complex evolutionary history with adenoviruses and small circular DNA tumor viruses including papillomaviruses and polyomaviruses. Adomaviruses are described in a number of fish species in association with both necrotizing and proliferative diseases. BLAST analysis of the viral genome revealed greatest nucleotide identity (71.29%) to guitarfish adomavirus (GAdoV), another elasmobranch virus associated with proliferative (epidermal) skin lesions. Lesions in the index animal persisted for approximately 1 year during which time four conspecifics developed similar proliferations. Ultimately, lesions in all sharks regressed spontaneously without recurrence for 2 years.

A novel protocol for three-dimensional mapping of sand tiger shark (Carcharias taurus) enclosure use in aquaria: Implications for management.

This study investigated sand tiger shark (STS; Carcharias taurus) spatial use and exclusion in public aquarium enclosures using a novel protocol for three-dimensional mapping. Fifty-one STS were observed in 14 enclosures, and swimming pattern, depth, and location were recorded in ZooMonitor. Data were converted into quantitative, three-dimensional representations using ArcGIS® Pro v. 2.9. All observed STS except one swam in circular patterns, and 80% (n = 41) showed a directional swimming bias. Most STS (80%; n = 41) predominantly utilized the top two-thirds of the enclosures, though 83% (n = 34) of those had swimming obstructions in the bottom of the enclosure. Avoidance of obstructed areas, sections <7 m wide, as well as behavioral spatial separation, resulted in utilization of between 27% and 66% of available enclosure space. STS underutilized corners, pinch-points, and obstructed areas requiring abrupt directional changes and instead exhibited continual, unimpeded swimming patterns. In addition, this study found no relationship between directional swimming bias or use of smaller enclosure volumes and spinal deformity, a health issue affecting 26% of STS 10 years ago but now with an incidence of 6%. Using novel protocols for three-dimensional mapping and volume estimation, this study demonstrated that enclosures facilitating unimpeded, continuous swimming are most usable for STS and provides important information that will be useful for future enclosure design.

Community science informs movement and reproductive ecology of sand tigers Carcharias taurus off North Carolina, United States of America

Sand tigers are frequently observed at shipwrecks and other artificial reef habitats off North Carolina (USA), but data about occupancy, movement ecology, and site fidelity are lacking. Spot A Shark USA researchers used Wildbook© photoidentification software to spot map sand tigers in images provided by recreational SCUBA divers, or collected from remotely operated vehicles, and an offshore live-streaming camera. We uniquely identified 1837 sand tigers, 101 of which were resighted on more than one date between 2005–2021. Sand tigers of both sexes and various ages were found year-round along the northern, central and southern coast. We identified shipwrecks or artificial reef sites with consistently high numbers of shark encounters reported, sometimes with seasonal occupancy patterns. Resighted sharks were often encountered at the same or nearby locations, confirming high levels of residency and site fidelity to specific locations. Together, the mating scars seen on 121 female sand tigers and 202 females documented with rotund abdomens consistent with pregnancy highlight the importance of NC waters for reproduction. We also quantified other characteristics of the sand tigers visible in the photographs including wounds, parasitic copepods, and attached fishing gear. Our results reflect the importance of habitats off the NC coast to the movement and reproductive ecology of sand tigers at multiple life history stages. Sand tiger populations have declined in the Northwest Atlantic, so information about residence at specific locations, seasonal patterns of occupancy, and sex-dependent behaviors associated with migration and reproduction are important to future management and conservation of the species.

Interactive three-dimensional atlas of the mineralized skeleton of the sand tiger shark Carcharias taurus.

Non-invasive computed tomography (CT) of an adult sand tiger shark Carcharias taurus Rafinesque, 1810 is used to provide an interactive three-dimensional 'general' shark (Selachimorpha) anatomy atlas. Given its post-cranial body morphology, the sand tiger shark appeared to be a well-chosen candidate and through comparison of the sand tiger shark with several other representatives of all eight established orders of sharks, we confirm that the relatively large degree of mineralization of the endoskeleton, along with the overall size, makes the sand tiger shark an ideal candidate for skeletal segmentation and construction of a skeletal atlas using conventional CT. This atlas both increases accessibility to the internal morphological features of the sand tiger shark and provides a more generalized overview of the skeletal anatomy of sharks and can aid as a supplement to destructive fresh dissection of specimens in the future and the construction of future skeletal atlases of other less mineralized sharks.

Centralized red muscle in Odontaspis ferox and the prevalence of regional endothermy in sharks.

The order Lamniformes contains charismatic species such as the white shark Carcharodon carcharias and extinct megatooth shark Otodus megalodon, and is of particular interest given their influence on marine ecosystems, and because some members exhibit regional endothermy. However, there remains significant debate surrounding the prevalence and evolutionary origin of regional endothermy in the order, and therefore the development of phenomena such as gigantism and filter-feeding in sharks generally. Here we show a basal lamniform shark, the smalltooth sand tiger shark Odontaspis ferox, has centralized skeletal red muscle and a thick compact-walled ventricle; anatomical features generally consistent with regionally endothermy. This result, together with the recent discovery of probable red muscle endothermy in filter feeding basking sharks Cetorhinus maximus, suggests that this thermophysiology is more prevalent in the Lamniformes than previously thought, which in turn has implications for understanding the evolution of regional endothermy, gigantism, and extinction risk of warm-bodied shark species both past and present.

Endangered shark species traded as “cação” in São Paulo during the COVID-19 lockdown: DNA-barcoding a snapshot of products

BackgroundElasmobranch populations are declining, predominantly driven by overfishing, and over a third of global sharks, rays, and chimeras are estimated to be threatened with extinction. In terms of trade, Brazil is ranked the eleventh-largest shark producer and the top importer of shark meat in the world. Research has shown that elasmobranchs are sold in Brazil under the name “cação” (a generic designation for cartilaginous fish) to overcome consumer resistance.Methodology and resultsThis study used DNA barcoding to investigate the sale of sharks in the State of São Paulo during the COVID-19 lockdown. A total of 35 samples of “cação” were analysed, revealing six different shark species on sale, including Carcharhinus falciformis, Carcharhinus signatus, Carcharias taurus, Isurus oxyrinchus, and Isurus paucus, that are threatened with extinction according to the IUCN red list. This study demonstrates that vulnerable elasmobranchs are being commercialised under the label “cação” in the São Paulo State and Brazil.ConclusionsComparison of shark products traded before and during the COVID-19 pandemic showed no significant difference, suggesting lockdown did not affect patterns of species commercialisation. Effective fisheries and sale monitoring, correct product labelling legislation and increased consumer awareness that “cação” is shark are needed for appropriate conservation and management of shark populations in Brazil.

Northerly range expansion and first confirmed records of the smalltooth sand tiger shark, Odontaspis ferox, in the United Kingdom and Ireland.

Three Odontaspis ferox (confirmed by mtDNA barcoding) were found in the English Channel and Celtic Sea in 2023 at Lepe, UK (50.7846, -1.3508), Kilmore Quay, Ireland (52.1714, -6.5937), and Lyme Bay, UK (50.6448, -2.9302). These are the first records of O. ferox in either country, and extend the species' range by over three degrees of latitude, to >52° N. They were ~275 (female), 433 (female), and 293 cm (male) total length, respectively. These continue a series of new records, possibly indicative of a climate change-induced shift in the species' range.

A new Bartonian elasmobranch assemblage from the Kutch Basin, western India, and its significance in the context of paleoclimate change

ABSTRACT The upper part of the Harudi Formation of the Kutch basin in Gujarat, western India, has recently yielded a heretofore undocumented assemblage of elasmobranchs, including extinct sand tiger sharks Brachycarcharias lerichei and Striatolamia macrota, extinct tiger sharks Galeocerdo eaglesomei and G. clarkensis, requiem shark Carcharhinus mancinae, as well as sawfish Pristis sp. A bony fish taxon represented by Trichiurus sp. was also recovered. After a 43-years gap, this study provides a taxonomic update on the middle Eocene sharks of Kutch. Their coexistence with the larger benthic foraminifera Nummulites obtusus and planktonic foraminifera Orbulinoides beckmanni dates this fish fauna to 40–41.03 Ma, which corresponds to the time frame of the Bartonian transgression and extreme warming event Middle Eocene Climatic Optimum (MECO). The MECO elasmobranch assemblage of Kutch comes from shelf settings with bathymetry of 30–60 m, and it differs from those associated with Paleocene–Eocene hyperthermal events and deposited in the bay complex. It seems that G. clarkensis and C. mancinae emerged in Kutch during MECO. The global stratigraphic distribution demonstrates that B. lerichei and S. macrota originated in North America, and their appearance in Kutch expands their geographic range into the eastern Tethys realm, possibly as a result of MECO-linked Bartonian/Kirther transgression.

Shark teeth zinc isotope values document intrapopulation foraging differences related to ontogeny and sex

Trophic ecology and resource use are challenging to discern in migratory marine species, including sharks. However, effective management and conservation strategies depend on understanding these life history details. Here we investigate whether dental enameloid zinc isotope (δ66Znen) values can be used to infer intrapopulation differences in foraging ecology by comparing δ66Znen with same-tooth collagen carbon and nitrogen (δ13Ccoll, δ15Ncoll) values from critically endangered sand tiger sharks (Carcharias taurus) from Delaware Bay (USA). We document ontogeny and sex-related isotopic differences indicating distinct diet and habitat use at the time of tooth formation. Adult females have the most distinct isotopic niche, likely feeding on higher trophic level prey in a distinct habitat. This multi-proxy approach characterises an animal’s isotopic niche in greater detail than traditional isotope analysis alone and shows that δ66Znen analysis can highlight intrapopulation dietary variability thereby informing conservation management and, due to good δ66Znen fossil tooth preservation, palaeoecological reconstructions.

Updated Checklist of Chondrichthyan Species in Croatia (Central Mediterranean Sea)

Almost half of all chondrichthyan species in the Mediterranean Sea are threatened with extinction, according to the IUCN Red List. Due to a substantial lack of access to data on chondrichthyan catches in the Mediterranean Sea, especially of threatened species, the implementation of conservation measures is extremely insufficient. This also concerns the Adriatic Sea. Here we present a detailed and up-to-date assessment of the species occurring in Croatian waters, as the last checklist of chondrichthyans in Croatian waters was conducted in 2009. Occurrence records from historical data, literature and citizen science information have been compiled in order to present a comprehensive list of species occurrences. We found 54 chondrichthyan species between 1822 and 2022, consisting of a single chimaera, 23 rays and skates, and 30 shark species. Here, four additional species are listed but are considered doubtful. Five species are reported here for the first time for Croatian waters that were not listed in the survey from 2009. Nearly one-third of the species reported here are critically endangered in the entire Mediterranean Sea, based on the IUCN Red List. Additionally, we revisited the Croatian records of the sandtiger shark Carcharias taurus Rafinesque, 1810 and discussed its potential confusion with the smalltooth sandtiger shark Odontaspis ferox (Risso, 1810). Our results thus provide novel insights into the historical and current distribution patterns of chondrichthyan fishes in the Croatian Sea and provide a basis for further research as well as conservation measures.

Marine reserve use by a migratory coastal shark, Carcharias taurus

Networks of small no-take marine protected areas (MPAs) are a popular approach to protect mobile marine species at key sites along their migration routes. Understanding how individuals vary in their use of these sites is needed to ensure MPA networks are optimised to offer maximum protection benefits. Using diver-led surveys, coded acoustic tags and a continental-scale collaborative network of acoustic receivers, we investigated variation in the use of three Australian MPAs by aggregating grey nurse sharks, Carcharias taurus. The Wolf Rock MPA was used year-round by C. taurus and as a gestation site, with females spending up to 254 d at the site with 2.2–3.7 year absences between residencies. In contrast, Flat Rock and Cherubs Cave-Henderson Rock MPAs were used as a transitory aggregation site with males and females occurring at the site for 30 min–59 d intervals between June–January, only. Migratory movements ranged up to 1500 km along the coastline, intersected 18 MPAs and/or recognised C. taurus aggregation sites, and connected temperate waters at Montague Island (36.25° S) with that of the southern Great Barrier Reef (23.40° S). Our study demonstrates how local receiver arrays and national collaborative acoustic telemetry networks are powerful tools to reveal use, fidelity and connectivity of MPA networks by marine migratory species. As the east Australian C. taurus population is critically endangered and at particular risk of anthropogenic threats, ongoing monitoring of the species' movement behaviour and complementary management outside protected area boundaries is warranted to assist its protection.

First Confirmed Record of the Smalltooth Sand Tiger, Odontapis Ferox, in Galicia (NW Spain)

The smalltooth sand tiger shark Odontaspis ferox (Risso, 1810) appears to have an extensive and fragmented distribution in tropical and warm-temperate worldwide oceans. One female of O. ferox was caught and released by a small-scale fishery vessel in Ría de Arousa (Northwest of Spain), subsequently stranded still alive on the coast (42°33’18.4"N 8°49’18.3"O) after a few hours. The individual (336 cm total length, weight ~ 300 kg) was identified based on a collection of features including the characteristic dentition, body morphology and by molecular assignment. This is the first confirmed record of O. ferox in Galician waters. This finding complements the knowledge of the geographic distribution and occurrence of this rare and sparse species in the Northeastern Atlantic.

Population distribution, aggregation sites and seasonal occurrence of Australia’s western population of the grey nurse shark Carcharias taurus

Western Australia (WA) is host to a genetically discrete population of grey nurse sharks Carcharias taurus, listed by the IUCN as Near Threatened based on mean annual catch rates prior to protection within Australian waters in 1997. Only one small aggregation has been documented in WA to date with little data available on population dynamics, or spatial and temporal distribution along the WA coastline. We analysed C. taurus data from 16 years (2006-2021) of diver observations (2347 sightings) and commercial fisheries bycatch records (574 sharks), finding evidence of 4 new aggregation sites. Sightings at Shark Cave, a popular dive site near Perth, were related to water temperature and time of year (non-linear), with sightings per unit effort generally higher during the warmer months of summer and autumn (20-22°C). Evidence of fishing injuries was found on 17% of all C. taurus photo-tagged at Shark Cave. Strong site philopatry was apparent at most sites, and included a male shark that returned for 12 consecutive years to the Exmouth Navy Pier. This study confirms the range of Australia’s western population of C. taurus from near the South Australia/WA border, north to Shark Bay, with distribution extending further north along the coast when sea temperatures are lower (May-December). The beneficial role of citizen science in large observation studies such as this one is supported. However, while this research greatly increases the C. taurus knowledge base in WA, a large information deficit still exists. The identification and assessment of further aggregation sites is recommended, underpinning future management and protection measures for this iconic species.

Quaternary fossil shark (Neoselachii: Galeomorphii and Squalomorphii) diversity from southern Brazil

Sharks are cartilaginous fish that appeared 245 million years ago and became a highly diversified group, occupying several niches successfully. On the coast of Rio Grande do Sul, Brazil, shark fossils are commonly found ex situ associated with accumulations of biodetrital gravels along the current beach line. The present study consisted of a faunistic and paleobiologic survey of sharks from the Quaternary in the southern region of the Rio Grande do Sul Coastal Plain (RSCP), southern Brazil. Based on taxonomy, about 3611 fossilized shark teeth collected on the beaches of Cassino and Hermenegildo were analyzed. A total of 13 taxa were identified, among them cf. Carcharhinus brachyurus, cf. Carcharhinus leucas, cf. Carcharhinus longimanus, Carcharhinus sp., Carcharias taurus, Carcharodon carcharias, Galeocerdo cuvier, Galeorhinus galeus, Isurus oxyrinchus, Notorynchus cepedianus, Rhizoprionodon sp., Sphyrna sp. and Squatina sp. Besides the already known species, here we also report the presence of Carcharhinus brachyurus, Carcharhinus longimanus, Galeorhinus galeus, Rhizoprionodon sp. and Squatina sp. as the first fossil record in the Pleistocene of Brazil for these taxa in the region. The study showed that the fossil taxa identified are similar to those extant taxa that inhabit the coast of Rio Grande do Sul. Evidence of climate oscillations that occurred during the Quaternary can be seen throughout the presence of the species Carcharhinus leucas, Carcharodon carcharias, and Galeocerdo cuvier (when compared to the composition of the modern shark fauna). Since, currently, the occurrence of these species are given as rare in the region. The present study expanded the occurrence of fossil species on the coast of the state of Rio Grande do Sul and confirmed the occurrence of populations of Carcharias taurus, Carcharodon carcharias, Carcharhinus sp., and Carcharhinus leucas during the Quaternary.

The Relative Abundance and Occurrence of Sharks off Ocean Beaches of New South Wales, Australia.

Simple SummaryCoastal sharks are especially susceptible to anthropogenic pressures due to their use of nearshore habitats. It is therefore necessary to distinguish species-specific variation in occurrence among ocean beaches and identify key environmental drivers that may influence shark distribution patterns. For swell-influenced coastal beaches, however, information on shark abundance and occurrence is still limited. The relative abundance and occurrence of sharks off 42 ocean beaches of New South Wales (NSW), Australia, was investigated using a long-term drone-based monitoring program from 2017–2021. Overall, there were 36,384 drone flights conducted, sighting a total of 281 sharks. Shark observations occurred in <1% of drone flights, indicating that potentially dangerous sharks, and sharks in general, are rare off NSW beaches. Key environmental predictors, such as the distance to the nearest estuary, headland, and island, as well as ocean temperature and wave height, were identified for species-specific shark distribution. This study demonstrated that existing drone-based monitoring programs used to reduce shark bite incidents can also provide valuable information about the distribution of potentially dangerous, vulnerable, and endangered coastal sharks. This information will be beneficial for implementing evidence-based conservation strategies and may also assist in minimising negative human-shark interactions.There is still limited information about the diversity, distribution, and abundance of sharks in and around the surf zones of ocean beaches. We used long-term and large-scale drone surveying techniques to test hypotheses about the relative abundance and occurrence of sharks off ocean beaches of New South Wales, Australia. We quantified sharks in 36,384 drone flights across 42 ocean beaches from 2017 to 2021. Overall, there were 347 chondrichthyans recorded, comprising 281 (81.0%) sharks, with observations occurring in <1% of flights. Whaler sharks (Carcharhinus spp.) had the highest number of observations (n = 158) recorded. There were 34 individuals observed for both white sharks (Carcharodon carcharias) and critically endangered greynurse sharks (Carcharias taurus). Bull sharks (Carcharhinus leucas), leopard sharks (Stegostoma tigrinum) and hammerhead species (Sphyrna spp.) recorded 29, eight and three individuals, respectively. Generalised additive models were used to identify environmental drivers for detection probability of white, bull, greynurse, and whaler sharks. Distances to the nearest estuary, headland, and island, as well as water temperature and wave height, were significant predictors of shark occurrence; however, this varied among species. Overall, we provide valuable information for evidence-based species-specific conservation and management strategies for coastal sharks.

Energetic consequences of resource use diversity in a marine carnivore.

Understanding how intraspecific variation in the use of prey resources impacts energy metabolism has strong implications for predicting long-term fitness and is critical for predicting population-to-community level responses to environmental change. Here, we examine the energetic consequences of variable prey resource use in a widely distributed marine carnivore, juvenile sand tiger sharks (Carcharias taurus). We used carbon and nitrogen isotope analysis to identify three primary prey resource pools-demersal omnivores, pelagic forage, and benthic detritivores and estimated the proportional assimilation of each resource using Bayesian mixing models. We then quantified how the utilization of these resource pools impacted the concentrations of six plasma lipids and how this varied by ontogeny. Sharks exhibited variable reliance on two of three predominant prey resource pools: demersal omnivores and pelagic forage. Resource use variation was a strong predictor of energetic condition, whereby individuals more reliant upon pelagic forage exhibited higher blood plasma concentrations of very low-density lipoproteins, cholesterol, and triglycerides. These findings underscore how intraspecific variation inresource use may impact the energy metabolism of animals, and more broadly, that natural and anthropogenically driven fluctuations in prey resources could have longer term energetic consequences.

The influence of bait position on the catch of target and non-target sharks in a SMART drumline bather protection program

There is increasing support for shark bite mitigation measures, such as SMART (Shark-Management-Alert-in-Real-Time) drumlines that minimise impacts on target sharks and other marine animals. On the east coast of Australia, SMART drumlines are used in a shark management program to catch and relocate white (Carcharodon carcharias), tiger (Galeocerdo cuvier), and bull sharks (Carcharhinus leucas; herein referred to as target sharks). This study examines the effect of bait position relative to the seabed on SMART drumline catches in eastern Australian waters, aiming to optimise catches of target sharks while reducing bycatch. Over 17 months, SMART drumlines were deployed at Ballina and Evans Head, New South Wales. Trace extensions were attached to 3.2 m standard traces to test the effect of bait height above the seabed on shark catch in an experimental design that alternated bait position every fortnight. White and tiger shark catches accounted for 67% of the total catch, whereas bull sharks were infrequently caught (3%). Bait position above the seabed did not significantly influence catch probability of white and tiger sharks. However, catches of Critically Endangered grey nurse sharks (Carcharias taurus) and false alarm events significantly increased when baits were closer to the seabed. Catches of white and tiger sharks varied throughout the year and were linked to seasonal water temperature changes. The standard traces effectively caught target shark species whilst reducing catches of grey nurse sharks and false alarm events, highlighting that the trace length currently used for NSW SMART drumline deployments is optimal.

The sociality of Atlantic sturgeon and sand tiger sharks in an estuarine environment

Social network analyses are used by ecologists to examine the various drivers of animal social structures. While social behaviours are found throughout the animal kingdom, their roles in structuring marine communities are poorly understood. Comparisons of sociality across marine fishes in the same location and time are rare. A large acoustic telemetry network in Delaware Bay allowed us to analyse the sociality of Atlantic sturgeon, Acipenser oxyrinchus oxyrinchus , and sand tiger sharks, Carcharias taurus . Both species co-occur in the bay, are long-lived, make seasonal migrations and aggregate for unknown reasons. However, these species occupy distinctly different trophic positions and ecological niches. We found little evidence for sociality among Atlantic sturgeon. However, sand tigers exhibited evidence for preferential co-occurrence, modularity and assortment by maturity. In addition, we found that these species preferentially associate with conspecifics. Our findings suggest that sand tigers exhibit a higher degree of sociality than Atlantic sturgeon while in the Delaware Bay. From these findings, we outline the social structures of two evolutionary distinct species while they co-occur in the Delaware Bay. Additionally, we explored the influence that environmental acoustic conditions have on social network metrics and make recommendations for future analyses using acoustic telemetry in estuarine environments. • We analysed sociality of Atlantic sturgeon and sand tiger sharks in Delaware Bay. • Sand tigers exhibited preferential co-occurrence, modularity and maturity assortment. • Atlantic sturgeon exhibited little sign of sociality. • Sand tigers and Atlantic sturgeon preferentially assorted by species. • Environmental variables may influence network formation in short time windows.

Reproductive Cycle and Periodicity of In Situ and Aquarium Female Sand Tiger Sharks Carcharias taurus from the Western North Atlantic

Fundamental characteristics of the reproductive biology of female sand tiger sharks Carcharias taurus are needed to understand the periodicity, seasonality and environmental factors essential for reproduction in this iconic species. Animals in managed care, such as aquariums, provide the unique opportunity for longitudinal study in contrast to in situ sharks that are examined opportunistically, and at a single point in time. Additionally, comparison of reproductive observations from successfully reproducing in situ sharks and aquarium sharks may help elucidate reasons for lack of reproduction among aquarium sharks and aid the development of assisted reproductive techniques for managed populations. Reproductive status of in situ and aquarium female sharks was assessed using ultrasonography and plasma hormone (17β-estradiol, testosterone, and progesterone) monitoring. The reproductive cycle was divided into eight stages based on ovarian activity and uterine contents. In situ sharks were sampled from Delaware Bay (n = 29), North Carolina (n = 39) and South Carolina (n = 11) during April-November from 2015–2020. Nineteen aquarium females from five aquaria were examined longitudinally for two or more consecutive years. Reproductive regionalization was observed among in situ females with the majority (83%) of North Carolina females in an active state of reproduction and all Delaware females in a resting reproductive state. All aquarium females had a pattern of reproductive cycling that was consistent with alternating years of activity and rest with confirmed biennial (n = 7) or triennial (n = 3) reproductive cycles with spring seasonality. In contrast to in situ females, aquarium females often retained uterine eggs for 9-20 months after ovulation in the absence of a developing embryo(s). Pre-ovulatory aquarium females had significantly higher concentrations of 17β-estradiol, testosterone and progesterone than other reproductive stages. For females in the ovulatory stage, in situ females had higher testosterone than aquarium females. Endocrine differences between successfully reproducing in situ females and aquarium females likely contribute to the limited reproductive success observed for this species in managed care and may be a reflection of diminished seasonal cues and environmental differences.

Determination of fluorine distribution in shark teeth by laser-induced breakdown spectroscopy.

Quantifying the chemical composition of fast-growing hard tissues in the environment can shed valuable information in terms of understanding ecosystems both prehistoric and current. Changes in chemical composition can be correlated with environmental conditions and can provide information about the organism's life. Sharks can lose 0.1 to 1.1 teeth/day, depending on species, which offers a unique opportunity to record environmental changes over a short duration of time. Shark teeth contain a biomineral phase that is made up of fluorapatite [Ca5(PO4)3F], and the F distribution within the tooth can be correlated to tooth hardness. Typically, this is determined by bulk acid digestion, energy-dispersive X-ray spectroscopy (EDS), or wavelength-dispersive spectroscopy. Here we present laser-induced breakdown spectroscopy (LIBS) as an alternative and faster approach for determining F distribution within shark teeth. Using a two-volume laser ablation chamber (TwoVol3) with innovative embedded collection optics for LIBS, shark teeth were investigated from sand tiger (Carcharias Taurus), tiger (Galeocerdo Cuvier), and hammerhead sharks (Sphyrnidae). Fluorine distribution was mapped using the CaF 603 nm band (CaF, Β 2Σ+ → X 2Σ+) and quantified using apatite reference materials. In addition, F measurements were cross referenced with EDS analyses to validate the findings. Distributions of F (603 nm), Na (589 nm), and H (656 nm) within the tooth correlate well with the expected biomineral composition and expected tooth hardness. This rapid methodology could transform the current means of determining F distribution, particularly when large sample specimens (350 mm2, presented here) and large quantities of specimens are of interest.