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Keywords = Lamniformes

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12 pages, 1283 KiB  
Article
Phylogeographic Analyses of the Shortfin Mako, Isurus oxyrinchus Rafinesque, 1810 (Chondrichthyes: Lamniformes) from the Central Mediterranean Sea, a Critically Endangered Species in the Region
by Noel Vella and Adriana Vella
Fishes 2023, 8(10), 520; https://doi.org/10.3390/fishes8100520 - 20 Oct 2023
Cited by 4 | Viewed by 2151
Abstract
The Shortfin mako shark, Isurus oxyrinchus Rafinesque, 1810, is a globally distributed highly migratory pelagic shark species, occurring mostly in temperate and tropical regions, including the Mediterranean Sea where it is by-caught during fishing activities targeting other economically important fish species. The aim [...] Read more.
The Shortfin mako shark, Isurus oxyrinchus Rafinesque, 1810, is a globally distributed highly migratory pelagic shark species, occurring mostly in temperate and tropical regions, including the Mediterranean Sea where it is by-caught during fishing activities targeting other economically important fish species. The aim of this study is to investigate the genetic connectivity of the Shortfin mako from the central Mediterranean Sea to previously studied populations. The mtDNA control region (CR), 977 bp, of 37 I. oxyrinchus specimens collected between 2004 and 2012 from landings in Malta were analysed, and we identified nine haplotypes, including three newly discovered haplotypes that may be unique to the Mediterranean Sea and which represent 16.7% of the studied individuals. These haplotypes, together with variations in haplotype frequencies, led to significant FST and ϕST values between the Mediterranean population and other global populations, with the exception of that from the north Atlantic Ocean. This study provides the first insight of the mtDNA CR diversity of this critically endangered species in the Mediterranean Sea and highlights the importance of conserving this species in the region. Full article
(This article belongs to the Section Biology and Ecology)
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12 pages, 3983 KiB  
Article
The Palaeobiology of the False Mako Shark, Parotodus benedenii (Le Hon, 1871): A View from the Pliocene Mediterranean Sea
by Alberto Collareta, Simone Casati and Andrea Di Cencio
J. Mar. Sci. Eng. 2023, 11(10), 1990; https://doi.org/10.3390/jmse11101990 - 16 Oct 2023
Cited by 5 | Viewed by 3034
Abstract
The extinct “false mako” shark, Parotodus benedenii (Lamniformes: Otodontidae), is essentially known from large, robust teeth that are widespread but overall rare in Oligocene to Pliocene deposits worldwide. More than 150 years after its description, this species still represents a palaeontological conundrum, as [...] Read more.
The extinct “false mako” shark, Parotodus benedenii (Lamniformes: Otodontidae), is essentially known from large, robust teeth that are widespread but overall rare in Oligocene to Pliocene deposits worldwide. More than 150 years after its description, this species still represents a palaeontological conundrum, as very little is known about its body aspect and palaeoecology. Here, we describe new specimens of P. benedenii from the Pliocene of Tuscany, central Italy. These new finds comprise some of the geologically youngest finds of P. benedenii worldwide, witnessing to the survival of false makos until the Late Pliocene at least, which in turn suggests that P. benedenii may have been the latest surviving member of the family Otodontidae. Building upon a thorough literature review, we provide an updated synthesis of the palaeobiology of P. benedenii. In light of the morphological evidence, and considering previously published suggestions, P. benedenii may be reconstructed as a large-sized, carnivorous shark that dwelt in pelagic settings and fed primarily on large, soft prey and scavenging items. Thus, some ecological partitioning did likely exist between P. benedenii and other elasmobranch apex predators of the Neogene mid-latitude seas (including, in Pliocene times, the extant species Carcharodon carcharias, Carcharhinus leucas and Galeocerdo cuvier). Full article
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12 pages, 1853 KiB  
Article
Allometric Growth of the Enigmatic Deep-Sea Megamouth Shark Megachasma pelagios Taylor, Compagno, and Struhsaker, 1983 (Lamniformes, Megachasmidae)
by Chan-gyu Yun and Yuuki Y. Watanabe
Fishes 2023, 8(6), 300; https://doi.org/10.3390/fishes8060300 - 3 Jun 2023
Cited by 5 | Viewed by 4918
Abstract
Megamouth sharks Megachasma pelagios Taylor, Compagno, and Struhsaker, 1983, are a large-bodied, planktivorous, deep-sea species with peculiar morphology. Since their initial description in the late 20th century, many individuals of different sizes have been reported, but few studies examined ontogenetic changes in body [...] Read more.
Megamouth sharks Megachasma pelagios Taylor, Compagno, and Struhsaker, 1983, are a large-bodied, planktivorous, deep-sea species with peculiar morphology. Since their initial description in the late 20th century, many individuals of different sizes have been reported, but few studies examined ontogenetic changes in body shapes. Here, we assess the growth changes in their heads and fins based on length measurements from nine different-sized individuals (177–544 cm in total length). Bivariate analyses showed that the head becomes larger relative to body length with increasing body size (i.e., positive allometry), whereas the relative size of the caudal fin remains constant (i.e., isometric growth). This trend differs from basking sharks and apparently resembles whale sharks and some baleen whales, although they are all large-bodied filter feeders. Given that relative mouth size is linked to feeding modes, our results suggest that megamouth sharks have different feeding modes from ram-feeding basking sharks and may have some similarity with suction-feeding whale sharks and engulfment-feeding baleen whales. Full article
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16 pages, 55782 KiB  
Article
Hierarchical Microstructure of Tooth Enameloid in Two Lamniform Shark Species, Carcharias taurus and Isurus oxyrinchus
by Jana Wilmers, Miranda Waldron and Swantje Bargmann
Nanomaterials 2021, 11(4), 969; https://doi.org/10.3390/nano11040969 - 9 Apr 2021
Cited by 11 | Viewed by 4204
Abstract
Shark tooth enameloid is a hard tissue made up of nanoscale fluorapatite crystallites arranged in a unique hierarchical pattern. This microstructural design results in a macroscopic material that is stiff, strong, and tough, despite consisting almost completely of brittle mineral. In this contribution, [...] Read more.
Shark tooth enameloid is a hard tissue made up of nanoscale fluorapatite crystallites arranged in a unique hierarchical pattern. This microstructural design results in a macroscopic material that is stiff, strong, and tough, despite consisting almost completely of brittle mineral. In this contribution, we characterize and compare the enameloid microstructure of two modern lamniform sharks, Isurus oxyrinchus (shortfin mako shark) and Carcharias taurus (spotted ragged-tooth shark), based on scanning electron microscopy images. The hierarchical microstructure of shark enameloid is discussed in comparison with amniote enamel. Striking similarities in the microstructures of the two hard tissues are found. Identical structural motifs have developed on different levels of the hierarchy in response to similar biomechanical requirements in enameloid and enamel. Analyzing these structural patterns allows the identification of general microstructural design principles and their biomechanical function, thus paving the way for the design of bioinspired composite materials with superior properties such as high strength combined with high fracture resistance. Full article
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