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Fishes : a guide to their diversity
Offers a broad overview of the morphological diversity of fishes, arranged in a modern classification system.
Book
The African coelacanth genome provides insights into tetrapod evolution
The discovery of a living coelacanth specimen in 1938 was remarkable, as this lineage of lobe-finned fish was thought to have become extinct 70 million years ago. The modern coelacanth looks remarkably similar to many of its ancient relatives, and its evolutionary proximity to our own fish ancestors provides a glimpse of the fish that first walked on land. Here we report the genome sequence of the African coelacanth, Latimeria chalumnae. Through a phylogenomic analysis, we conclude that the lungfish, and not the coelacanth, is the closest living relative of tetrapods. Coelacanth protein-coding genes are significantly more slowly evolving than those of tetrapods, unlike other genomic features. Analyses of changes in genes and regulatory elements during the vertebrate adaptation to land highlight genes involved in immunity, nitrogen excretion and the development of fins, tail, ear, eye, brain and olfaction. Functional assays of enhancers involved in the fin-to-limb transition and in the emergence of extra-embryonic tissues show the importance of the coelacanth genome as a blueprint for understanding tetrapod evolution.
Journal Article
Synovial joints were present in the common ancestor of jawed fish but lacking in jawless fish
Synovial joints, characterized by reciprocally congruent and lubricated articular surfaces separated by a cavity, can simultaneously provide mobility and load bearing. Here, we study the early evolution of synovial joints by examining the morphological, genetic, and molecular features required for the development and function of the joints in elasmobranchs and cyclostomes. We show the presence of cavitated and articulated joints in the skeleton of elasmobranchs, such as the little skate ( Leucoraja erinacea ) and bamboo shark ( Chiloscyllium plagiosum ). However, our results do not support the presence of articular cavities between cartilaginous elements in cyclostomes such as sea lampreys ( Petromyozon marinus ) and hagfish ( Myxine glutinosa ). Immunostaining reveals the expression of lubrication-related proteoglycans like aggrecan and glycoproteins such as hyaluronic acid receptor (CD44) at the articular surfaces in little skates. Analysis of joint development in little skate embryos shows the expression of growth differentiation factor-5 (Gdf5) and β -catenin at the joint interzones like tetrapods. Muscle paralysis in little skate embryos leads to joint fusion, suggesting that muscle activity is necessary for the formation of synovial cavity and development of normal articular surfaces, in a manner similar to zebrafish and tetrapods. Together, these data suggest that synovial joints originated in the common ancestor of extant gnathostomes. A review of fossils from the extinct clades along the gnathostome stem suggests that joints with reciprocally articulating surfaces arose in the dermal skeleton of the common ancestor of all jawed vertebrates. Synovial joints in cartilaginous tissue were a subsequent gnathostome innovation.
Journal Article
The shocking secret of the electric eel... and more!
Tag along with scientists as they uncover intriguing adaptations that help animals survive in their environments. Discover the electric eels hunting tactics and an unexpected defense strategy, why some fish sleep in mucous cocoons, how jumping spiders hear from across a room, what the shape of a European eels head reveals about its diet, and why midshipman fish sing only at night.
Book
Fishes
There are more than 33,000 species of living fishes, accounting for more than half of the extant vertebrate diversity on Earth. This unique and comprehensive reference showcases the basic anatomy and diversity of all 82 orders of fishes and more than 150 of the most commonly encountered families, focusing on their distinctive features. Accurate identification of each group, including its distinguishing characteristics, is supported with clear photographs of preserved specimens, primarily from the archives of the Marine Vertebrate Collection at Scripps Institution of Oceanography. This diagnostic information is supplemented by radiographs, additional illustrations of particularly diverse lineages, and key references and ecological information for each group. An ideal companion to primary ichthyology texts, Fishes: A Guide to Their Diversity gives a broad overview of fish morphology arranged in a modern classification system for students, fisheries scientists, marine biologists, vertebrate zoologists, and everyday naturalists. This survey of the most speciose group of vertebrates on Earth will expand the appreciation of and interest in the amazing diversity of fishes.
eBook
Ontogenetic shifts in sound production and shared sonic mechanisms in two priacanthid fishes
Sound production in teleost fishes relies on diverse anatomical adaptations, yet convergent mechanisms involving extrinsic sonic muscles acting on the swim bladder are widespread. This study investigates the acoustic and morphological features of two priacanthid species, Indo-Pacific glasseye Heteropriacanthus carolinus and moontail bullseye Priacanthus hamrur to explore interspecific similarities in sound production. Using recordings and anatomical analyses, we show that both species rely on a forced-response mechanism, where the contraction rate of fast sonic muscles determines the fundamental frequency. This is corroborated by the smaller diameter of sonic fibres compared to epaxial fibres in both species. Despite belonging to different genera, both species exhibit extrinsic sonic muscles originating from the first pleural rib and inserting on the anterior swim bladder. However, P. hamrur displays anterior bladder projections potentially involved in enhanced hearing, absent in H. carolinus . Acoustic signals were broadly similar between species, suggesting that the morphological shift in muscle insertion does not affect sound structure. Comparative analysis across geographically distant populations of H. carolinus (Indian and Pacific Oceans) revealed variation in acoustic features that was size-dependent rather than region-specific. Juveniles emitted continuous pulse trains with high fundamental frequencies, whereas adults produced more segmented calls with lower frequencies. These ontogenetic differences reflect developmental modulation of vocal output, not anatomical changes. Overall, our findings highlight the conserved nature of sonic mechanisms in Priacanthidae, the influence of body size on acoustic variation, and the potential role of swim bladder morphology in auditory enhancement rather than sound generation.
Journal Article
Vampyromorph coleoid predation by an ichthyosaurian from the Early Jurassic Lagerstätte of Bascharage, Luxembourg
Many Early Jurassic marine predators were seemingly adapted to hunt soft and fast prey items such as cephalopods. However, deciphering what these animals ate and, therefore, the intensity of their competition is challenging, as fossilised gut content is biased by multiple factors. In this paper, we report a loligosepiid vampyromorph coleoid in the gut of a specimen of the ichthyosaurian Stenopterygius triscissus from the early Toarcian Bascharage Lagerstätte of Southern Luxembourg. This is the first report of octobrachian predation in ichthyosaurians. The coeval pachycormid teleosts Pachycormus macropterus and Saurostomus esocinus have recently been reported to feed on loligosepiid octobrachians as well. We use this opportunity to compare the functional anatomy of these taxa and re-evaluate the affinities of coleoids preserved as ichthyosaurian gut content.
Journal Article
Evolutionary regime shifts in age and size at maturation of exploited fish stocks
Worldwide declines of fish stocks raise concerns about deleterious consequences of harvesting for stock abundances and individual life histories, and call for appropriate recovery strategies. Fishes in exploited stocks mature earlier at either larger or smaller sizes due to both genetic and plastic responses. The latter occur commonly when reduced competition for food leads to faster growth. Using a size-structured consumer-resource model, which accounts for both genetic and plastic responses, we show that fisheries-induced evolutionary changes in individual life history and stock properties can easily become irreversible. As a result of annual spawning, early maturation at small sizes and late maturation at large sizes can become alternative, evolutionarily and ecologically stable states under otherwise identical environmental conditions. Exploitation of late-maturing populations can then induce an evolutionary regime shift to smaller maturation sizes associated with stepwise, 1-year decreases in age at first reproduction. Complete and early fishing moratoria slowly reverse this process, but belated or partial closure of fisheries may accelerate or even instigate further evolution to smaller sizes at maturation. We suggest that stepwise decreases in maturation age can be used as early warnings of upcoming evolutionary changes, and should inspire timely restrictions of fisheries.
Journal Article
Jaws and teeth of the earliest bony fishes
Jaws... and teeth
There are very few fossils that record the earliest history of jawed vertebrates. Fossil remains of crown-group osteichthyans (bony fishes, including tetrapods) are known as far back as the Silurian (418 million years ago), but tracing the osteichthyans any further has proven difficult. Now Botella
et al
. report the first unambiguous evidence for osteichthyan characters in two previously known Late Silurian fish (423–416 million years old), demonstrating that they are not only the oldest, but phylogenetically the most primitive osteichthyans known to date.
The first unambiguous evidence for osteichthyan (bony fishes, including tetrapods) characters in two previously known Late Silurian (423–416 Myr) fishes is reported, demonstrating that they are not only the oldest, but phylogenetically the most primitive osteichthyans known to date
Extant jawed vertebrates, or gnathostomes, fall into two major monophyletic groups, namely chondrichthyans (cartilaginous fishes) and osteichthyans (bony fishes and tetrapods). Fossil representatives of the osteichthyan crown group are known from the latest Silurian period, 418 million years (Myr) ago, to the present. By contrast, stem chondrichthyans and stem osteichthyans are still largely unknown. Two extinct Palaeozoic groups, the acanthodians and placoderms, may fall into these stem groups or the common stem group of gnathostomes, but their relationships and monophyletic status are both debated. Here we report unambiguous evidence for osteichthyan characters in jaw bones referred to the late Silurian (423–416-Myr-old) fishes
Andreolepis hedei
and
Lophosteus superbus
, long known from isolated bone fragments, scales and teeth, and whose affinities to, or within, osteichthyans have been debated
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. The bones are a characteristic osteichthyan maxillary and dentary, but the organization of the tooth-like denticles they bear differs from the large, conical teeth of crown-group osteichthyans, indicating that they can be assigned to the stem group.
Andreolepis
and
Lophosteus
are thus not only the oldest but also the most phylogenetically basal securely identified osteichthyans known so far.
Journal Article