Comparative morphology of rostral cartilages in extant mackerel sharks (Chondrichthyes, Lamniformes, Lamnidae) using CT scanning

A comparative study of rostral morphology of extant mackerel sharks (Lamniformes, Lamnidae) is presented. Based on computed tomography (CT) scans of fresh specimens, 3D reconstructions, dried museum chondrocrania and the available literature, detailed morphological descriptions of the rostral cartilages are provided for the type species of all three extant lamnid genera, namely Carcharodon carcharias (Linnaeus, 1758), Isurus oxyrinchus Rafinesque, 1810 and Lamna nasus (Bonnaterre, 1788), and compared with those of I. paucus Guitart Manday, 1966 and L. ditropis Hubbs & Follett, 1947. Despite intraspecific variation, the rostral cartilages of all extant lamnids present significant differences that allow genusand species-level identification, which is especially of use to identify fossil rostral nodes of these particular taxa. The main differences were found to be in overall calcification of the rostrum (Lamna > Isurus > Carcharodon), general configuration of the rostral open space, position of the base of the lateral rostral cartilages, (non-)abutting lateral cartilages, (absent) rostral keels and shape of the rostral node. In cross section, the base of the rostral node is rounded in Lamna, Y-shaped in Isurus and uncalcified in juvenile and subadult Carcharodo (tesserae absent)

Cold case: The early disappearance of the Bramble shark (<i>Echinorhinus brucus</i>) in European and adjacent waters

Surveys of marine resources suffer from the lack of long time series, particularly concerning targeted species currently not of high value. The disappearance of a marine species, even of large size, can go completely unnoticed. Large shark species are among the most affected by depletion because of their life history traits. In European and adjacent waters, the rare Bramble shark (Echinorhinus brucus; formerly known as the Spinous shark) is suspected of being threatened, but the lack of population data precludes its evaluation. As a result, the species is currently unregulated and listed as "Data Deficient" by the International Union for Conservation of Nature (IUCN)

Lepadogaster purpurea (Actinopterygii: Gobiesociformes: Gobiesocidae) from the eastern Mediterranean Sea: Significantly extended distribution range

The Cornish sucker, Lepadogaster purpurea (Bonnaterre, 1788), a clingfish species thus far known from the north-eastern Atlantic south to western Africa, the Canary Islands and Madeira, and the western Mediterranean basin, was recently collected in Sicily (Italy), Croatia and Greece. Species identification was based on morphological and/or molecular data. These new Mediterranean records of L. purpurea are the first evidence of the species’ occurrence in the eastern Mediterranean basin and significantly extend its known distribution range, which likely mirrors that of its sister species Lepadogaster lepadogaster (Bonnaterre, 1788)

The phylogenetic origin and evolution of acellular bone in teleost fishes: insights into osteocyte function in bone metabolism

International audienceVertebrate bone is composed of three main cell types: osteoblasts, osteoclasts and osteocytes, the latter being by far the most numerous. Osteocytes are thought to play a fundamental role in bone physiology and homeostasis, however they are entirely absent in most extant species of teleosts, a group that comprises the vast majority of bony 'fishes', and approximately half of vertebrates. Understanding how this acellular (anosteocytic) bone appeared and was maintained in such an important vertebrate group has important implications for our understanding of the function and evolution of osteocytes. Nevertheless, although it is clear that cellular bone is ancestral for teleosts, it has not been clear in which specific subgroup the osteocytes were lost. This review aims to clarify the phylogenetic distribution of cellular and acellular bone in teleosts, to identify its precise origin, reversals to cellularity, and their implications. We surveyed the bone type for more than 600 fossil and extant ray-finned fish species and optimised the results on recent large-scale molecular phylogenetic trees, estimating ancestral states. We find that acellular bone is a probable synapomorphy of Euteleostei, a group uniting approximately two-thirds of teleost species. We also confirm homoplasy in these traits: acellular bone occurs in some non-euteleosts (although rarely), and cellular bone was reacquired several times independently within euteleosts, in salmons and relatives, tunas and the opah (Lampris sp.). The occurrence of peculiar ecological (e.g. anadromous migration) and physiological (e.g. red-muscle endothermy) strategies in these lineages might explain the reacquisition of osteocytes. Our review supports that the main contribution of osteocytes in teleost bone is to mineral homeostasis (via osteocytic osteolysis) and not to strain detection or bone remodelling, helping to clarify their role in bone physiology