Search results for "Sharks"

Vimentin and desmin of a cartilaginous fish, the shark Scyliorhinus stellaris: Sequence, expression patterns and in vitro assembly

2002

In the shark Scyliorhinus stellaris we have biochemically identified and cDNA-cloned orthologs of human vimentin and desmin, SstV and SstD, as deduced from immunoblotting and sequence alignment with teleost, frog and human vimentin and desmin, respectively. This allowed us to further clarify the relationship of previously identified lower vertebrate intermediate filament proteins to mammalian vimentin and desmin. Immunofluorescence microscopy with antibodies H5 and VIM13.2 showed vimentin expression in shark eye and brain and absence in epithelia, which resembles the situation in higher vertebrates. In addition, SstV is expressed in many mesenchymal cell types which corresponds to the case …

Pliocene colonization of the Mediterranean by Great White Shark inferred from fossil records, historical jaws, phylogeographic and divergence time an…

2020

Aim: Determine the evolutionary origin of the heretofore poorly characterized contemporary Great White Shark (GWS; Carcharodon carcharias) of the Mediterranean Sea, using phylogenetic and dispersal vicariance analyses to trace back its global palaeo-migration pattern. Location: Mediterranean Sea. Taxon: Carcharodon carcharias. Methods: We have built the largest mitochondrial DNA control region (CR) sequence dataset for the Mediterranean GWS from referenced historical jaws spanning the 19th and 20th centuries. Mediterranean and global GWS CR sequences were analysed for genetic diversity, phylogenetic relationships and divergence time. A Bayes factor approach was used to assess two scenarios …

Ontogenetic trophic segregation between two threatened smooth-hound sharks in the Central Mediterranean Sea

2020

AbstractElasmobranchs are among the species most threatened by overfishing and a large body of evidence reports their decline around the world. As they are large predators occupying the highest levels of marine food webs, their removal can alter the trophic web dynamic through predatory release effects and trophic cascade. Suitable management of threatened shark species requires a good understanding of their behaviour and feeding ecology. In this study we provide one of the first assessments of the trophic ecology of the “vulnerable” smooth-hounds Mustelus mustelus and M. punctulatus in the Central Mediterranean Sea, based on stomach contents and stable isotope analyses. Ontogenetic diet ch…

The Pillars of Hercules as a bathymetric barrier to gene flow promoting isolation in a global deep-sea shark (Centroscymnus coelolepis).

2015

Catarino, Diana ... et. al.-- 19 pages, 5 figures, 4 tables, data accessibility http://dx.doi.org/10.5061/dryad.ss368, supporting information http://dx.doi.org/10.1111/mec.13453

Trophic position of Otodus megalodon and great white sharks through time revealed by zinc isotopes

2022

AbstractDiet is a crucial trait of an animal’s lifestyle and ecology. The trophic level of an organism indicates its functional position within an ecosystem and holds significance for its ecology and evolution. Here, we demonstrate the use of zinc isotopes (δ66Zn) to geochemically assess the trophic level in diverse extant and extinct sharks, including the Neogene megatooth shark (Otodus megalodon) and the great white shark (Carcharodon carcharias). We reveal that dietary δ66Zn signatures are preserved in fossil shark tooth enameloid over deep geologic time and are robust recorders of each species’ trophic level. We observe significant δ66Zn differences among the Otodus and Carcharodon popu…

By-catch of cetaceans and other species of conservation concern during pair trawl fishing operations in the Adriatic Sea (Italy)

2010

By-catch is one of the main sources of anthropogenic mortality in marine species of conservation concern worldwide. Between 2006 and 2008, the Consorzio Nazionale Interuniversitario per le Scienze del Mare (CoNISMa) coordinated a monitoring programme of cetacean by-catch in Italian pelagic trawlers, funded in compliance with European Regulation 812/2004. Sixteen independent observers monitored a total of 3141 hauls. The observation coverage ranged between 0.9 and 6.3% of the regional fishing effort. Almost all by-catch events were recorded in the northern Adriatic Sea. By-catch rates of bottlenose dolphins (Tursiops truncatus) and loggerhead turtles (Caretta caretta) were 0.0006 and 0.0255 …

Past aquatic environments in the Levant inferred from stable isotope compositions of carbonate and phosphate in fish teeth

2019

Here we explore the carbon and oxygen isotope compositions of the co-existing carbonate and phosphate fractions of fish tooth enameloid as a tool to reconstruct past aquatic fish environments and harvesting grounds. The enameloid oxygen isotope compositions of the phosphate fraction (δ18OPO4) vary by as much as ~4‰ for migratory marine fish such as gilthead seabream (Sparus aurata), predominantly reflecting the different saline habitats it occupies during its life cycle. The offset in enameloid Δ18OCO3-PO4 values of modern marine Sparidae and freshwater Cyprinidae from the Southeast Mediterranean region vary between 8.1 and 11.0‰, similar to values reported for modern sharks. The mean δ13C …

Autecology, lifestyle and hydrodynamics of early vertebrates

2018

Capítulo 1. Introducción general Los vertebrados constituyen uno de los grupos de animales más exitosos, contando con más de 60000 especies distintas y ocupando la gran mayoría de ecosistemas marinos y continentales. Su origen y evolución han sido temas centrales para biólogos y paleontólogos durante décadas, pero las discusiones en este sentido se han visto obstaculizadas porque los grupos actuales (ciclóstomos, condrictios y osteíctios) constituyen solo una pequeña representación de toda la diversidad que existió en el pasado. Por lo tanto, el registro fósil es crucial para arrojar luz sobre estos aspectos permitiendo desvelar el momento y el tempo de la aparición de los diferentes caract…

Sicilian Cenozoic sharks from the collections of G. G. Gemmellaro Museum

2006

The determination of maturity stages in male elasmobranchs (Chondrichthyes) using a segmented regression of clasper length on total length

2013

A novel statistical method for estimating the stages of maturity in male sharks and skates based on a segmented regression (SRM) is proposed. We hypothesize that this method is able to find the transition points in the three-phase relationship between total length (TL) and clasper length (CL). We applied an SRM to TL–CL data of nine species, from large pelagic sharks (e.g., Carcharhinus falciformis) to small coastal skates (e.g., Rioraja agassizi), captured in the southwestern Atlantic and northeastern Pacific. As expected, SRM detected two breakpoints, defining three maturity stages (immature, maturing, and mature), in six out of nine species. For three species, it was not possible to fin…