Search results for "forme"
showing 10 items of 1192 documents
Biomechanical insights into the dentition of megatooth sharks (Lamniformes: Otodontidae)
2021
AbstractThe evolution of gigantism in extinct otodontid sharks was paralleled by a series of drastic modifications in their dentition including widening of the crowns, loss of lateral cusplets, and acquisition of serrated cutting edges. These traits have generally been interpreted as key functional features that enabled the transition from piscivory to more energetic diets based on marine mammals, ultimately leading to the evolution of titanic body sizes in the most recent forms (including the emblematic Otodus megalodon). To investigate this hypothesis, we evaluate the biomechanics of the anterior, lateral, and posterior teeth of five otodontid species under different loading conditions by…
Assessing metabolic constraints on the maximum body size of actinopterygians: locomotion energetics of Leedsichthys problematicus (Actinopterygii, Pa…
2018
Maximum sizes attained by living actinopterygians are much smaller than those reached by chondrichthyans. Several factors, including the high metabolic requirements of bony fishes, have been proposed as possible body‐size constraints but no empirical approaches exist. Remarkably, fossil evidence has rarely been considered despite some extinct actinopterygians reaching sizes comparable to those of the largest living sharks. Here, we have assessed the locomotion energetics of Leedsichthys problematicus, an extinct gigantic suspension‐feeder and the largest actinopterygian ever known, shedding light on the metabolic limits of body size in actinopterygians and the possible underlying factors th…
Use of nursery areas by the extinct megatooth shark Otodus megalodon (Chondrichthyes: Lamniformes)
2020
Nursery areas are fundamental for the success of many marine species, particularly for large, slow-growing taxa with low fecundity and high age of maturity. Here, we examine the population size-class structure of the extinct gigantic shark Otodus megalodon in a newly described middle Miocene locality from Northeastern Spain, as well as in eight previously known formations (Temblor, Calvert, Pisco, Gatún, Chucunaque, Bahía Inglesa, Yorktown and Bone Valley). In all cases, body lengths of all individuals were inferred from dental parameters and the size-class structure was estimated from kernel probability density functions and Gaussian mixture models. Our analyses support the presence of fi…
Evidence of endothermy in the extinct macropredatory osteichthyan Xiphactinus audax (Teleostei, Ichthyodectiformes)
2020
Xiphactinus audax is the largest macropredatory osteichthyan ever known (Everhart et al., 2010). Some of the largest specimens exceed 5 m in total length, although the discovery of a few large, isolated teeth suggests that this teleost could reach even larger body sizes (Vavrek et al., 2016, and references therein). Fossil remains of this species have only been reported from the Upper Cretaceous of North America, across the Western Interior Basin (Schwimmer et al., 1997; Vavrek et al., 2016). The discovery of several virtually complete individuals in this area has provided valuable information about the anatomy, the dimensions, and the ecology of this species (Cope, 1872; Bardack, 1965). Xi…
Linking species habitat and past palaeoclimatic events to evolution of the teleost innate immune system
2017
Host-intrinsic factors as well as environmental changes are known to be strong evolutionary drivers defining the genetic foundation of immunity. Using a novel set of teleost genomes and a time-calibrated phylogeny, we here investigate the family of Toll-like receptor ( TLR ) genes and address the underlying evolutionary processes shaping the diversity of the first-line defence. Our findings reveal remarkable flexibility within the evolutionary design of teleost innate immunity characterized by prominent TLR gene losses and expansions. In the order of Gadiformes, expansions correlate with the loss of major histocompatibility complex class II ( MHCII ) and diversifying selection analyses sup…
Use of DNA barcoding in the assignment of commercially valuable fish species from Romania
2017
DNA barcoding is a molecular technique frequently used either for biodiversity monitoring and fish conservation or in the identification of the species of origin for raw and processed food from restaurants or fish markets. The most important aspect of this technique is that it works for all stages of life and can be used to distinguish between closely related taxa. Also, the technique has been used to unmask attempts of frauds in fish markets where more desirable and expensive fish are sometimes substituted with lower valued species. Our study aims to test the utility of the COI barcoding gene in the correct identification of several economically and ecologically valuable fish species, and …
The Legal International Wildlife Trade Favours Invasive Species Establishment: The Monk and Ring-Necked Parakeets in Spain
2018
The international wildlife trade is a lucrative business. Although a huge variety of animal groups are trafficked, the Psittaciformes (parrots) are amongst the most traded avian groups. Deliberate or accidental releases of imported parrots have led to the establishment of feral populations in many countries. Far from their native habitats, parrots may cause economic and ecological damage, and may even favour the transmission of zoonotic diseases. Despite this, the links between numbers of imported individuals and the establishment of non-native populations is not well known. In this study, we analysed data on imports of two well-known invasive parrots, the Monk Parakeet Myiopsitamonachus an…
Ecology of the Atlantic black skipjack Euthynnus alletteratus (Osteichthyes: Scombridae) in the western Mediterranean Sea inferred by parasitological…
2016
Between 2008 and 2011, the head of 150 Euthynnus alletteratus (Osteichthyes: Scombridae) caught inshore off the southeastern Iberian coast (western Mediterranean Sea) were examined for parasites. Two monogeneans, four didymozoid trematodes and four copepods were found. Parasite abundance showed a positive relationship with the annual sea surface temperature, except for Pseudocycnus appendiculatus, but negative with the sea depth (Capsala manteri, Neonematobothrium cf. kawakawa and Caligus bonito). Prevalences and mean abundances differed significantly among sampling areas, except for C. manteri, Oesophagocystis sp. 2 and Ceratocolax euthynni, and sampling years (Melanocystis cf. kawakawa, N…
Successive Losses of Central Immune Genes Characterize the Gadiformes' Alternate Immunity.
2016
Great genetic variability among teleost immunomes, with gene losses and expansions of central adaptive and innate components, has been discovered through genome sequencing over the last few years. Here, we demonstrate that the innate Myxovirus resistance gene (Mx) is lost from the ancestor of Gadiformes and the closely related Stylephorus chordatus, thus predating the loss of Major Histocompatibility Complex class II (MHCII) in Gadiformes. Although the functional implication of Mx loss is still unknown, we demonstrate that this loss is one of several ancient events appearing in successive order throughout the evolution of teleost immunity. In particular, we find that the loss of Toll-like r…
Two seas, two lineages: How genetic diversity is structured in Atlantic and Mediterranean greater amberjack Seriola dumerili Risso, 1810 (Perciformes…
2016
The vastness of the ocean and our limited ability to observe and monitor the organisms therein make molecular markers particularly useful tools in the investigation of the ecology and evolutionary biology of fish. Nowadays, due to increased demand of fish foods, genetic researches are focused on new candidate species for aquaculture, such as Seriola species. Here, the analyses of eight polymorphic nuclear microsatellites loci and three mitochondrial (mt) DNA genes (16S-rRNA, Cyt-b, and D-Loop) in the greater amberjack, Seriola dumerili, detected breakpoint between Atlantic and Mediterranean populations, presumably arisen by the oceanographic features of the Almeria-Oran Front opposed to the…