Reassessment of the possible size, form, weight, cruising speed, and growth parameters of the extinct megatooth shark, Otodus megalodon (Lamniformes: Otodontidae), and new evolutionary insights into its gigantism, life history strategies, ecology, and extinction

Palaeontologia Electronica, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 1, 2025

Otodus megalodon (Lamniformes: Otodontidae) is an iconic Neogene shark, but the lack of well-preserved skeletons has hampered our understanding various aspects its biology. Here, we reassess some biological properties using a new approach, based on known vertebral specimens O. and 165 species extinct extant neoselachian sharks across ten orders. Using median neurocranial caudal fin proportions relative to trunk proportion among non-mitsukurinid/non-alopiid lamniforms, show that could have had slender body possibly reached about 24.3 m in length. Allometric considerations indicate stout plan like white shark (Carcharodon carcharias) for incurred excessive hydrodynamic costs, further supporting interpretation likely slenderer than C. carcharias. A 24.3-m-long may weighed around 94 t, with estimated cruising speed 2.1-3.5 km h-1. reanalysis growth bands suggests size at birth 3.6-3.9 megalodon, previous interpretations ovoviviparity embryos' intrauterine oophagous behavior, less need nursery areas. Additional inferred patterns corroborated by fossil record support hypothesis emergence carcharias during Early Pliocene least partly responsible demise due competition resources. These are working hypotheses expected serve as reasonable reference points future studies biology megalodon.

Language: Английский

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Evidence of cascading ecosystem effects following the loss of white sharks from False Bay, South Africa

Frontiers in Marine Science, Journal Year: 2025, Volume and Issue: 12

Published: March 25, 2025

Language: Английский

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Basking sharks of the Arctic Circle: year-long, high-resolution tracking data reveal wide thermal range and prey-driven vertical movements across habitats

Animal Biotelemetry, Journal Year: 2025, Volume and Issue: 13(1)

Published: May 9, 2025

Abstract Background Understanding the movement ecology of marine megaplanktivores is essential for conserving these ecologically significant species and managing their responses to environmental change. While telemetry has advanced our knowledge filter-feeding mammal migrations, annual patterns large sharks, such as basking sharks ( Cetorhinus maximus ), remain poorly understood. This particularly case near high latitude range limits where climate impacts are intensifying. In this study, we deployed pop-up satellite archival tags (PSATs) on C. in northern Norway investigate individual possible drivers over an entire cycle. Results Geolocated tracks from two females revealed contrasting migration strategies: one shark performed a return spending boreal winter close Azores, while other resided north Arctic Circle until January before moving North Sea spring. Across diverse habitats, both utilized wide thermal range. included previously unrecorded short-term exposures sub-zero temperatures, extending known tolerance species. High-resolution time series data recovered PSATs enabled use signal processing gradient-based filtering techniques vertical relation physical biological environment. oceanic elevated mesopelagic was observed together with diel migration, whereas shelf areas depth-use were confined by topography more variable, reflective dynamic hydrographic conditions prey distributions. With zooplankton distributions being structured ambient light, density gradients, local topography, alignment frequented depths isolumes, mixed layer depths, bathymetric contours, bioluminescence events suggests actively track layers across habitats. Conclusions Recorded eurythermy behavioural plasticity suggest be well-adapted ocean conditions. These traits may critical responding rapid climate-driven changes abiotic biotic environments high-latitudes, providing insights into how endangered filter-feeders might navigate shifting ecosystems. Graphical

Language: Английский

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Ecological erosion and expanding extinction risk of sharks and rays

Science, Journal Year: 2024, Volume and Issue: 386(6726)

Published: Dec. 5, 2024

The true state of ocean biodiversity is difficult to assess, and there are few global indicators track the primary threat overfishing. We calculated a 50-year Red List Index extinction risk ecological function for 1199 sharks rays found that since 1970, overfishing has halved their populations worsened by 19%. Overfishing largest species in nearshore pelagic habitats risks loss ecomorphotypes 5 22% erosion functional diversity. Extinction higher countries with large human coastal but lower nations stronger governance, larger economies, greater beneficial fisheries subsidies. Restricting fishing (including incidental catch) trade sustainable levels combined prohibiting retention highly threatened can avert further depletion, widespread population connectivity, top-down predator control.

Language: Английский

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Forensic‐Based and Environmentally Responsible Protocol to Manage Shark Fatal Bites on Humans Can Better Contribute to Conservation Needs

Aquatic Conservation Marine and Freshwater Ecosystems, Journal Year: 2025, Volume and Issue: 35(2)

Published: Feb. 1, 2025

ABSTRACT Although sharks are important for marine ecosystems, they still suffer culling campaigns after human fatalities. A case study from the Caribbean shows how rapid use of several complementary and reproducible forensic techniques not only allowed confirmation species implicated in bite but also accurate assessment size animal. Six non‐lethal fishing sessions led to capture shark individuals that were released either being eliminated due their unsuitable or absence remains stomach. Such an ecologically responsible risk management can contribute conservation.

Language: Английский

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Refining the trophic diversity, network structure, and bottom‐up importance of prey groups for temperate reef fishes

Ecosphere, Journal Year: 2025, Volume and Issue: 16(2)

Published: Feb. 1, 2025

Abstract Marine fish communities are highly diverse and contribute significantly to ecosystem processes. However, understanding their specific functional roles the importance of different prey groups for sustaining has been limited by historical classification fishes into a few coarse trophic guilds. Using diet information perform high‐resolution 298 temperate reef species distributed across south‐western Australia, we built metacommunity subregional networks evaluate most important relationships energy pathways in reefs. We identified 26 specialized guilds within herbivores, zoobenthivores, zooplanktivores, piscivores, cleaners. Zoobenthivorous had highest richness diversity with 191 nine Consumers crustaceans showed greater redundancy at level. In contrast, low echinodermivores could represent risk local capacity top‐down control sea urchins region. Finer scale analysis family level that piscivorous may influence pathways, some consuming other fishes, while others consume lower levels, particularly crustaceavores. Evidence predation on herbivorous was only found turf grazers, suggesting herbivory might not function as major direct link between primary producers higher levels. Among consumed micro‐crustaceans decapods accounted 33% all proportions. The macrophytes community likely resides indirectly through pathway detritivorous invertebrates, crustaceans, which more than themselves. Comparison region warmer locations per node strength interactions. Yet, structural properties consistent meta‐network regarding modularity. Considering predator–prey interactions enhances our blue‐print functions shallow marine systems. Identifying significance consumers is ecological forecasting prioritization conservation resource management regulations current fast‐changing world.

Language: Английский

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Legacies of Ecosystem Modification: Factors Affecting Long-Term Variation in the Abundance of Juvenile Bull Sharks in a Subtropical Estuary

Estuaries and Coasts, Journal Year: 2025, Volume and Issue: 48(3)

Published: March 13, 2025

Language: Английский

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Vertebral elemental composition reveals ontogenetic changes in habitat use in a Northeast Atlantic mesopredator shark

Estuarine Coastal and Shelf Science, Journal Year: 2025, Volume and Issue: unknown, P. 109255 - 109255

Published: March 1, 2025

Language: Английский

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Salinity drives the distribution of a top-order predator, the tiger shark (Galeocerdo cuvier), in an inverse estuary

Scientific Reports, Journal Year: 2025, Volume and Issue: 15(1)

Published: March 25, 2025

Understanding how dynamic environmental processes influence the distributions of top-order predators is fundamental to assess top-down effects on ecosystems. Tiger sharks (Galeocerdo cuvier) are a large top-predator that can trigger trophic cascades and structure communities. However, physical these animals in coastal systems largely unknown. Here, we influencing tiger shark movements inverse estuary Shark Bay, Western Australia, shallow embayment with salinities consistently above adjacent ocean. We applied Bayesian generalized linear mixed-effects models generate predictions suitable habitat for this region. These habitats were associated dense seagrass beds reflected spatial variability hypersaline water (< 40). Under future climate scenarios, areas worldwide predicted experience estuarine conditions. anticipate study will become applicable numerous other species gill-breathing fauna ecosystems across globe.

Language: Английский

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Ocean leadership: Can the European Union influence the global shark meat trade?

Marine Policy, Journal Year: 2025, Volume and Issue: 177, P. 106659 - 106659

Published: March 30, 2025

Language: Английский

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