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Most teleost fish propel themselves with lateral body waves powered by their axial muscles. These muscles also power suction feeding through rapid expansion of the mouth cavity. They consist of muscle segments (myomeres), separated by connective tissue sheets (myosepts). In adult teleosts, the fast axial muscle fibres follow pseudo‐helical trajectories, which are thought to distribute strain (relative fibre length change) approximately evenly across transverse sections during swimming, thereby optimizing power generation. To achieve strain equalization, a significant angle to the longitudinal axis on the frontal plane (azimuth) is necessary near the medial plane, increasing strain. Additionally, a deviation from longitudinal orientation on the sagittal plane (elevation) is required laterally to decrease strain. Despite several detailed morphological studies, our understanding of muscle‐fibre orientations in the entire axial musculature of fish remains incomplete. Furthermore, most research has been done in post‐larval stages, leaving a knowledge gap regarding the changing axial muscle architecture during larval development. Larval fish exhibit different body size, body shape and swimming kinematics compared to adults. They experience relatively high viscous forces, requiring higher tail‐beat amplitudes to overcome increased drag. Additionally, larval fish swim with higher tail‐beat frequencies. Histological studies have shown that in larval fish, muscle fibres in the anal region transition from an almost longitudinal orientation to a pseudo‐helical pattern by 3 dpf (days post‐fertilization). However, these studies were limited to a few sections of the body and were prone to shrinkage and tissue damage. Here, we introduce a novel methodology for quantifying muscle‐fibre orientations along the entire axial muscles. We selected 4 dpf larval zebrafish for our analyses, a stage where larvae are actively swimming but not yet free‐feeding. High‐resolution confocal 3D scans were obtained from four genetically modified zebrafish expressing green fluorescent protein in fast muscle fibres. Fluorescence variation allowed segmentation of individual muscle fibres, which were then converted to fish‐bound coordinates by correcting for the fish's position and orientation in the scan, and normalized to pool results across individuals. We show that at 4 dpf, muscle‐fibre trajectories exhibit a helical pattern tapering towards the tail. Average fibre angles decrease from anterior to posterior, with azimuth varying over the dorsoventral axis and elevation varying over the mediolateral axis. Notably, only the anteriormost 20% of the body displayed higher azimuth angles near the medial plane. Angles between neighbouring fibres were substantial, particularly at the rim of the epaxial and hypaxial muscles. The revealed muscle‐fibre architecture at this age presumably contributes to the swimming performance of these larvae, but that swimming performance is probably not the only driving factor for the fibre pattern. Our methodology offers a promising avenue for exploring muscle‐fibre orientations across ontogenetic series and provides a foundation for in‐depth functional studies on the role of muscle architecture in facilitating swimming performance of larval fish. [ABSTRACT FROM AUTHOR]

Shape of the myosepts and arrangement of the muscle fibres were recorded in the lateral musculature of the tail of Rana temporaria embryos and larvae. Well developed myomeres are present as early as st. 18-19. The main characteristics-ie. those related to functional properties-of myoseptal shape as well as of muscle fibre arrangement, remain unchanged throughout further development until degeneration of the tail occurs during metamorphosis. The rather simple myoseptal shape observed in Rana-as compared to the multiple cone-form observed in most fishes-shows a close agreement to hypothetical myosept models described in papers by Jarman (1961), van der Stelt (1968) and Willemse (1966). The muscle fibres in the m. lateralis of Rana are arranged in trajectorial patterns that show a close similarity to the trajectorial patterns observed in 'typical teleosts'. Both arrangements agree with trajectorial models based on the mathematical analyses of Alexander (1968). Neurulas anaesthetized with 1:10000 MS-222 and exposed up two weeks to this anaesthetic developed the same shape of the myosepts and arrangement of muscle fibres as in controls. Thus even the details of the function-related features of the myomere structure develop without functioning. In this field possible feedback meachisms are either not affected by anaesthesia or do not exist at all. [ABSTRACT FROM AUTHOR]

The distribution of intercellular junctions between premyotomal and myotomal cells of Xenopus embryos has been described. Intermediate junctions, gap junctions, and small desmosomes are found between unsegmented mesoderm cells. In the region of myotome formation gap junctions appear to be absent, although close appositions of cell membranes are found. Both gap and intermediate junctions are numerous between cells of the segmented myotomes; they occur within the myotomes close to the myosepts and at interdigitations between the myotomes across the myosepts. Gap junctions between the myotomes are found in embryos that have hatched and can swim. The observed distribution of gap junctions is correlated with physiological data on electrical coupling. Electrical connections via gap junctions may produce contraction of the axial musculature remote from motor innervation. [ABSTRACT FROM AUTHOR]

In the m. lateralis of Selachii a well-developed perimysium is found, while a similar structure is lacking in Teleostei. The Selachian perimysial fibres are arranged in distinct planes. In such planes two predominant fibre directions are found; the angle between each of them and the body-axis is 60-70°. Additionally the myosepts contain fibre bundles which are arranged in oblique loops. These myoseptal fibre-loops are present in Squalus, well as in the Teleosts we examined. In order to investigate the functional significance of these fibre arrangements we constructed a model, consisting of a steel strip representing the axial skeleton and a bundle of stretched rubber tubes representing the lateral musculature. Both components of this model have to be firmly interconnected. This is easily achieved by winding oblique loops of cotton thread around them, thus tying them to each other. When we now release the stretched rubber tubes, they contract, resulting in a proper bending of the model. An optimal value for the angle between the body-axis and the direction of the fibres is found. On the basis of the morphological similarity between the perimysial and the myoseptal loop fibres on the one hand and the cotton thread loops on the other, it is suggested that a functional similarity exists as well. So it is suggested that the functional significance of the perimysial fibre system, and of the myoseptal fibre loops, is the achievement of a firm contact between the lateral muscle mass and the axial skeleton. [ABSTRACT FROM AUTHOR]

Dinosaur locomotion and biomechanics, especially of their pelvic girdles and hindlimbs, have been analyzed in numerous studies. However, detailed volumetric musculoskeletal models of their tails are rarely developed. Here, we present the first detailed threedimensional volumetric reconstruction of the caudal epaxial and hypaxial musculature of the Late Jurassic sauropod Giraffatitan brancai, and highlight the importance and necessity of 3D modeling in musculoskeletal reconstructions. The tail of this basal macronarian is relatively short compared to diplodocids and other coexisting macronarians. The center of mass lies well in front of the hindlimbs, which support only ca. half the body weight. Still, our reconstruction suggests a total weight for the entire tail of ca. 2500 kg. We conclude that the hypaxial and tail-related hindlimb muscles (most specifically the M. caudofemoralis longus and its counterpart the M. ilioischiocaudalis) in Giraffatitan were well developed and robustly built, compensating for the shorter length of the M. caufodemoralis longus, the main hindlimb retractor muscle, in comparison with other sauropods. Our methodology allows a better-constrained reconstruction of muscle volumes and masses in extinct taxa, and thus force and weight distributions throughout the tail, than non-volumetric approaches. [ABSTRACT FROM AUTHOR]

The histological differentiations of myotomes and myosepts in the teleost Brachydanio rerio were studied in relation to function and shape development of the myotomes. The presence of contractile elements, intercellular space, growth by cell proliferation and the collagenous structure of the myosepts were considered as important characteristics. To a certain extent, the first deformations of the somites could be explained with these characteristics. It is suggested that firm attachment of the myosept collagen to the notochord sheath and the asymmetrical growth of the myotomes, might be of importance for the development of the oblique orientation of the muscle fibres. The sequence of the differentiation processes is not the same for all muscle cells. Cells next to the notochord synthetize myofilaments before they become polynuclear, while cells elsewhere in the myotome become polynuclear by fusion before they start to synthetize myofilaments. Some aspects of the histological differentiation of the myotomes in B. rerio were compared with myotome development in the chick, Gallus domesticus. [ABSTRACT FROM AUTHOR]

During the myotomal myogenesis in pike ( Esox lucius) two phases of muscle differentiation can be distinguished. In the first phase, the somite cells-derived stock, the primary myoblasts (of mesodermal origin), fuse to form multinucleate myotubes. Participation of myotomal cells of mesodermal origin is insufficient for further muscle development. In the second stage mesenchymal cells migrate, via myosepts, into the myotome between myotubes. Immunocytochemical detection of proliferating cell nuclear antigen (marker of S phase of cell cycle) showed their mitotic activity. Transmission electron microscope analysis revealed that the differentiation of these cells depends on their position. Cells remaining in the myosepts develop into fibroblasts and produce collagen fibres, while those that have migrated into the myotomes transform into secondary myoblasts. Mesenchymal cells in the studied species are believed to participate in hypertrophy and hyperplasy of muscle fibres. Thus the muscle fibres in pike ( E. lucius) are of mesodermal-mesenchymal origin. [ABSTRACT FROM AUTHOR]

The tendon sheaths (peritenons) of the paravertebral tendons of the tails of Wistar rats were studied using scanning electron microscopy. A phenomenological classification of the osteoid structures of the peritenons is given, with the identification of their persistent and permanent varieties. Sesamoid islets, needle-like and lamellar growths, and rudiments of osteons are classified as persistent. Persistent osteoid structures are well prepared for transformations aimed at strengthening the intracellular matrix under mechanical stress. Permanent osteoid structures are microgranules and faceted deposits of calcium phosphates involved in structural and mechanical processes and hetero- and homogeneous nucleation. Hyaluronate loosens the matrix of sesamoid islets, which increases the mobility of sesamoid globules and creates the prerequisites for their directed migration to areas of increased mechanical stress and foci of possible mineralization of extracellular substance, including fibrillar collagen. Hyaluronate sticks together granules and deposits of structured calcium phosphates and contributes to their growth and fixation in areas of increased risk of mechanical stress. This is a fundamentally important adaptive mechanism for strengthening the tendon tissue, acting in advance. [ABSTRACT FROM AUTHOR]

One of the main issues in the processing sector of the tambaqui Colossoma macropomum is the removal and/or fragmentation of intermuscular bones (IBs), which negatively impacts its production chain. In this sense, we quantitatively examined the IB variation in farmed tambaqui (n = 127) by comparing the direct anatomical dissection with the high-resolution X-ray imaging method. The number of IBs from the anatomical dissection on the left side of the fish (27.3 ± 5.70 bones) was comparable to that of X-ray analysis (26.9 ± 6.03 bones) (p > 0.05). In addition, 76% of deviation in IB number between the two studied methods was one to three, indicating both methods are equally efficient for identifying and quantifying IBs. We found a strong positive correlation (R = 0.8, p < 0.001) between the X-ray and the dissection methods. Our predictive models indicated that more than 50% of variation in IB length can be explained by growth parameters. Our results demonstrated that the X-ray method can provide accurate phenotypic data (in vivo) for IB counting and length measurements by extrapolating from the standard length, body weight and trunk over axis area of tambaqui. [ABSTRACT FROM AUTHOR]

Tendon tissue is actively used as a raw material in the production of collagen gels. This does not always take into account the structure and physicochemical properties of the intracapsular bundles and sheaths (peritenons) of the tendons. To refine these data, the intracapsular bundles and peritenons of the paravertebral tendons of Wistar rats were studied by scanning electron microscopy and X-ray phase and thermal analyses, as well as infrared (IR) spectroscopy. It has been established that intracapsular tendon collagen fibers are assembled into cylindrical bundles sutured with fibrillar knots. The most important locations of fibrillar knots are crimps in the boundary layers of intracapsular bundles and peritenons, endotenons, and remodeling zones of collagen fibrils. Peritenons have a framework structure that forms solid blocks of collagen arrays in the outer and inner layers. Tissue-specific peritenon structures are sesamoid islets and globules, needlelike and lamellar growths, and osteon-like lamellae involved in the strengthening and ossification of tendons by the mechanisms of heterogeneous and homogeneous nucleation of calcium phosphates. The main components of the mineral phase are pyrophosphates of the family of Ca2P2O7·nH2O and hydroxyapatites. In the tendon bundles, pyrophosphates are decondensed, which prevents the formation of hydroxyapatite. In peritenons, pyrophosphates are condensed into monoclinic phenotypes that induce hydroxyapatite synthesis. There are also differences in the state of hydroxyapatite: in bundles, it is crystalline, while it is amorphous in peritenons. According to thermal analysis and IR spectroscopy, the extracellular matrix of intracapsular tendon bundles is more mobile and fibrillar collagen is partially coagulated, hydrophobic, and resistant to maceration. In peritenons, the extracellular matrix is viscous and the collagen fibers are hydrophilic and sensitive to maceration. The data obtained are important in predicting the specialized properties of collagen-containing materials, taking into account the structural and metabolic features of the anatomical components of the tendons. [ABSTRACT FROM AUTHOR]

The environmental health impact of titanium dioxide nanoparticles (TiO2 NPs) is of emerging concern, but their effects and ecotoxicity resulting from the interaction between TiO2 NPs and metals, such as cadmium (Cd), on aquatic organisms remain limited. Thus, the current study aimed to evaluate the ecotoxic effects of TiO2 NPs and Cd (alone or in co-exposure) on zebrafish embryos and larvae, based on using multiple biomarkers. Embryos were exposed to environmentally relevant TiO2 NPs (0.1, 1.0, and 10 µg L−1) and Cd (10 µg L−1) concentrations, either alone or in a mix, for 168 h, whereas the control group was kept in reconstituted water. Results showed that the isolated TiO2 NPs have low toxicity to zebrafish embryos and larvae. However, Cd — alone or in co-exposure with TiO2 NPs — induced toxic effects in zebrafish, such as cardiotoxicity, as well as morphological and morphometric changes. The present study has shown TiO2 NPs/Cd interactive effects, including decreased toxicity, on the assessed models. Results have evidenced the potential environmental risk of the nanoparticle and metal mixtures, mainly at early vertebrate developmental stages. [ABSTRACT FROM AUTHOR]

Abstract: Different high pressure treatments (200–400MPa) were tested to establish the best processing conditions for cold-smoked fish fillets of dolphinfish (Coryphaena hippurus). The water holding capacity (WHC) decreased at 400MPa, while the shear strength by Kramer cell and Warner Bratzler and colour (L ∗, a ∗, and b ∗) values rose at all the pressures applied; although in the case of the myotomes and myosepts the increase in shear strength was higher at 400MPa, and the same was true for the a ∗ and b ∗ values. Lipid oxidation was prevented by the phenolic compounds from the smoking process. The best sensory attribute scores were achieved for cold-smoked dolphin fish pressurized at 300MPa. During chilled storage the behaviour of WHC, shear strength, lipid oxidation, and colour in the sample pressurized at 300MPa was quite stable, although sensory attributes declined over storage and fell off sharply after 65d. Total volatile base levels rose over the storage period but did not exceed 35mg TVBN/100g. High pressure did not extend the shelf life, but it was able to diminish bacterial counts during early storage. Since pressurized products have achieved better acceptance than non pressurized ones, it could be utilised to obtain new products. [Copyright &y& Elsevier]

The review summarizes the literature and our own experimental data on the features of the structure, function, and protein metabolism in skeletal muscles of teleost fish (Teleostei). Despite the conserved basic mechanisms of muscle growth (myogenesis) and degradation in vertebrates, fish are characterized by unique features related to their poikilothermy, indeterminate growth, and a special role of skeletal muscle as a depot of plastic and energy substrates. Fish skeletal muscles show high plasticity in terms of their ability to undergo substantial anabolic or catabolic changes in response to environmental variables, such as temperature, photoperiod, and food availability. Under optimal (anabolic) conditions, fish muscle tissue grows by hypertrophy and hyperplasia at an extremely high rate, while during the periods of high energy demand, including migration, starvation, and gonad maturation, catabolism of skeletal muscle proteins temporarily dominates. However, degradation of fish muscle tissue can be profound enough to exceed its regenerative capacity: both genetic programs and responses to exogenous signals of excessive strength and duration can be implemented via this scenario. An extreme and demonstrative example of the mobilization of muscle protein reserves and utilization of resulting amino acids for energy production and synthesis of stage-specific gonadal proteins are Pacific salmonids whose exhaustion during spawning is so great that results in their death. Fish myopathies and the potential of fish as objects for human disease modeling are also considered. [ABSTRACT FROM AUTHOR]

The aim of this study was a longitudinal description of the ontogeny of the adult electric organ of Campylomormyrus rhynchophorus which produces as adult an electric organ discharge of very long duration (ca. 25 ms). We could indeed show (for the first time in a mormyrid fish) that the electric organ discharge which is first produced early during ontogeny in 33-mm-long juveniles is much shorter in duration and has a different shape than the electric organ discharge in 15-cm-long adults. The change from this juvenile electric organ discharges into the adult electric organ discharge takes at least a year. The increase in electric organ discharge duration could be causally linked to the development of surface evaginations, papillae, at the rostral face of the electrocyte which are recognizable for the first time in 65-mm-long juveniles and are most prominent at the periphery of the electrocyte. [ABSTRACT FROM AUTHOR]

The structural details of some muscles, connective tissue elements, and bone structures of the visceral apparatus in the ember parrotfish Scarus rubroviolaceus were studied. In the lower jaw, a lock mechanism has been found that limits the degree of adduction of the anguloarticulare relative to the suspensorium. The impact of numerous subdivisions of m. adductor mandibulae on the elements of the front jaws in the process of the fish's mouth closing is discussed. [ABSTRACT FROM AUTHOR]

The structural details of some muscles, ligaments, aponeurotic structures, and osteological features of the pharyngeal jaw apparatus of ember parrotfish Scarus rubroviolaceus were studied. During the preparation, the evidence of the presence of a palatal organ in this species, which is convergently similar to that of benthic fish species of Cyprinidae and Catostomidae, has been found. The indirect effect of contraction of m. geniohyoideus and m. sternohyoideus on the operation of the pharyngeal jaw is discussed. Based on the results of anatomy and analysis of the literature, the interpretation of previously obtained morphofunctional data characterizing the apparatus of the pharyngeal jaws of parrotfish (Scaridae) is corrected using S. rubroviolaceus as an example. [ABSTRACT FROM AUTHOR]

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Shi drum ( Umbrina cirrosa L.) larvae were maintained under three photoperiod regimes: a natural photoperiod regime (16L:8D), continuous light (24L) and equal durations of light and dark (12L:12D) from the end of the vitelline phase to the end of the metamorphosis. Muscle and body parameters were studied at hatching and at 4, 10, 14, 39 and 55 days post hatching (dph). During the vitelline phase, the total body length growth was scarce, whereas the muscle grew significantly, being the hypertrophy of the main mechanism involved. Both the total body length and the hypertrophy were significantly greater at 16L:8D than in the rest of photoperiod regimes. At 10 and 14 dph, the greatest body length was reached at 16L:8D, followed by the 24L group, showing the 12L:12D group the lowest values. At 14 dph, the hypertrophy and hyperplasia were also higher at 16L:8D than in the rest of groups. At 39 dph, the highest values of body length were reached in both 16L:8D and 12L:12D regimes, this latter group reaching the highest values of hypertrophy, thus showing a compensatory growth when comparing with the previous stages. The end of the metamorphosis took place at 50-55 dph in all the groups, with 2.7-3.1 cm of body length ( P > 0.05). At this stage, the transverse area of the white muscle was similar among the groups, but the greatest hypertrophy was reached at 16L:8D, whereas the highest hyperplasia was reached at 24L. [ABSTRACT FROM AUTHOR]

In the view of an urgent necessity to improve the quantity and the quality of farmed fish species, there is a strong need to improve our basic knowledge on the effects of first feeding during the developmental stages of fish larvae. High mortality, mainly due to food deprivation or inappropriate food quality, has been observed in many larval fish species, but knowledge about the morphological, biochemical and molecular processes related to this topic is still poorly understood. The understanding of the early larval ontogeny as well as the larval nutritional requirements and the molecular and cellular mechanisms elicited by fish larvae during food deprivation and starvation are thus of primary importance. At this regard, this study investigates, in Dover sole larvae, the effects of starvation and starving/re-feeding procedures at a morphological, histological, biochemical and molecular level. The results evidenced that starved larvae progressively decrease in growth, lipid content, affected their gastrointestinal tract and muscle development and increased cortisol and heat shock protein 70 levels. On the contrary, starved and re-fed larvae showed, after the restoration of a favourable feeding condition, a compensatory growth. In conclusion, this is the first study analysing through a multidisciplinary approach the effects of food deprivation on the development of an important economic species, the Dover sole. [ABSTRACT FROM AUTHOR]

The muscle segments offish have a folded shape, termed a chevron, which is thought to be optimal for the undulating body movements of swimming. However, the mechanism shaping the chevron during embryogenesis is not understood. Here, we used time-lapse microscopy of developing zebrafish embryos spanning the entire somitogenesis period to quantify the dynamics of chevron shape development. By comparing such time courses with the start of movements in wildtype zebrafish and analysing immobile mutants, we show that the previously implicated body movements do not play a role in chevron formation. Further, the monotonie increase of chevron angle along the anteroposterior axis revealed by our data constrains or rules out possible contributions by previously proposed mechanisms. In particular, we found that muscle pioneers are not required for chevron formation. We put forward a tension-and-resistance mechanism involving interactions between intra-segmental tension and segment boundaries. To evaluate this mechanism, we derived and analysed a mechanical model of a chain of contractile and resisting elements. The predictions of this model were verified by comparison with experimental data. Altogether, our results support the notion that a simple physical mechanism suffices to self-organize the observed spatiotemporal pattern in chevron formation. [ABSTRACT FROM AUTHOR]

We present a comprehensive review of larval morphology in the Neotropical toad genus Melanophryniscus. The taxa studied included 23 species with representatives of recognized phenetic groups and different larval ecomorphological guilds: pond, stream, and phytotelm-dwelling tadpoles. Their external morphology variation is congruent with current phenetic arrangement based on adult features, but also reflects the habitat where larvae develop. Lotic tadpoles (i.e. M. tumifrons group and M. krauczuki) in general exhibit a more depressed body, a longer tail with lower fins, and larger oral discs than lentic forms (i.e. M. stelzneri group, M. moreirae, M. sanmartini, and M. langonei). Despite their peculiar, confined microhabitat, phytotelm larvae do not diverge markedly from non-arboreal species. The distinctive features of all species are the presence of a pineal end organ and the placement of the intestinal reversal point at the left of the abdomen in typical larval stages. The buccal cavity and musculoskeletal anatomy are quite conserved between species, yet some characteristics differ from those of other bufonids. The presence of one pair of subhyoid muscles is apparently an exclusive trait of Melanophryniscus among Bufonidae. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 112, 417-441. [ABSTRACT FROM AUTHOR]

A new species of Astyanax from the Rio Paraguaçu basin, Bahia, Brazil, is described. This new species is distinguished from its congeners known to occur in Brazilian drainages by the presence of small bony hooks on all fins of mature males. Furthermore, the new species can be diagnosed by its colour pattern, which consists of a unique vertically elongated humeral blotch, a conspicuous dark drop-shaped horizontal blotch over the caudal peduncle, tapering anteriorly and not extending to the median caudal-fin rays, and by the absence of a conspicuous broad dark midlateral stripe. The new species differs further by having the greatest body depth just anterior to the dorsal-fin origin, 32-35 perforated scales in the lateral line and a reduced number of branched anal-fin rays (16-20). Apparently, the new species does not fit into any species complex of Astyanax. The occurrence of bony hooks on all fins of Astyanax is discussed. [ABSTRACT FROM AUTHOR]

The potential of electrical impedance was investigated to differentiate thawed sea bass fillets ( Dicentrarchus labrax) previously subjected to different freezing conditions. The HP 4284A Precise LCR meter was used to measure impedance magnitude ( |Z|) and phase ( ϕ) at 27 frequencies from 0.1 to 1000 kHz. A needle-type multi electrode array was tested as a probe for impedance measurements. The study showed that fast and non-invasive control method based on measurement of ϕ on thawed fillets could assess the freezing conditions of white fish at higher frequencies of measurements (500-1000 kHz). The advantages of ϕ when compared with |Z| include its independence on temperature, on puncture depth of the probe and on duration of storage prior to freezing. Usage of a needle-type multi electrode array reduced the effect of muscle tissue anisotropy; however, even at 1 MHz, the differences in electrical measurements varied around 10-11% depending on muscle fibre direction. [ABSTRACT FROM AUTHOR]

To investigate the interactive effects of temperature and photoperiod on the growth performance, feeding parameters and muscle growth dynamics in juvenile Atlantic halibut ( Hippoglossus hippoglossus L.), a total of 1212 juvenile halibut, including 383 tagged fish (mean initial weight of tagged individuals: 17.6 ± 0.3 g SE), were reared under a simulated natural light regime for Bergen (60°25′N) or continuous light at 9, 12 and 15 °C from 3 December 2007 until 11 March 2008. The mean weight and growth rate were significantly higher at 12 and 15 °C than at 9 °C. In addition, significantly higher mean weight and growth rate were observed in halibut reared under continuous light at a low temperature, indicating an interactive effect of temperature and photoperiod on growth performance. No effect of temperature or photoperiod was found with respect to feed conversion efficiency, whereas a higher feed consumption at increasing temperature and a higher overall daily feeding rate at continuous light at a low temperature were observed. Indications of continuous light having a stronger effect at low temperatures on muscle growth dynamics were found. A difference in the size class distribution of fibre diameter was found between photoperiod treatments at 9 °C, suggesting that continuous light resulted in elevated hypertrophic growth at low temperature. This may suggest that the increased growth rate found at continuous light at 9 °C may be a result of hypertrophic growth in juvenile halibut. [ABSTRACT FROM AUTHOR]

This study addresses the effects of increased mechanical load on the vertebral bone of post-smolt Atlantic salmon by forcing them to swim at controlled speeds. The fish swam continuously in four circular tanks for 9 weeks, two groups at 0.47 body lengths (bl) × s−1 (non-exercised group) and two groups at 2 bl × s−1 (exercised group), which is just below the limit for maximum sustained swimming speed in this species. Qualitative data concerning the vertebral structure were obtained from histology and electron microscopy, and quantitative data were based on histomorphometry, high-resolution X-ray micro-computed tomography images and analysis of bone mineral content, while the mechanical properties were tested by compression. Our key findings are that the bone matrix secreted during sustained swimming had significantly higher mineral content and mechanical strength, while no effect was detected on bone in vivo architecture. mRNA levels for two mineralization-related genes bgp and alp were significantly upregulated in the exercised fish, indicating promotion of mineralization. The osteocyte density of the lamellar bone of the amphicoel was also significantly higher in the exercised than non-exercised fish, while the osteocyte density in the cancellous bone was similar in the two groups. The vertebral osteocytes did not form a functional syncytium, which shows that salmon vertebral bone responds to mechanical loading in the absence of an extensive connecting syncytial network of osteocytic cell processes as found in mammals, indicating the existence of a different mechanosensing mechanism. The adaptive response to increased load is thus probably mediated by osteoblasts or bone lining cells, a system in which signal detection and response may be co-located. This study offers new insight into the teleost bone biology, and may have implications for maintaining acceptable welfare for farmed salmon. [ABSTRACT FROM AUTHOR]

Teleost muscle first arises in early embryonic life and its development is driven by molecules present in the egg yolk and modulated by environmental stimuli including temperature and oxygen. Several populations of myogenic precursor cells reside in the embryonic somite and external cell layer and contribute to muscle fibres in embryo, larval, juvenile and adult stages. Many signalling proteins and transcription factors essential for these events are known. In all cases, myogenesis involves myoblast proliferation, migration, fusion and terminal differentiation. Maturation of the embryonic muscle is associated with motor innervation and the development of a scaffold of connective tissue and complex myotomal architecture needed to generate swimming behaviour. Adult muscle is a heterogeneous tissue composed of several cell types that interact to affect growth patterns. The development of capillary and lymphatic circulations and extramuscular organs - notably the gastrointestinal, endocrine, neuroendocrine and immune systems - serves to increase information exchange between tissues and with the external environment, adding to the complexity of growth regulation. Teleosts often exhibit an indeterminate growth pattern, with body size and muscle mass increasing until mortality or senescence occurs. The dramatic increase in myotomal muscle mass between embryo and adult requires the continuous production of muscle fibres until 40-50% of the maximum body length is reached. Sarcomeric proteins can be mobilised as a source of amino acids for energy metabolism by other tissues and for gonad generation, requiring the dynamic regulation of muscle mass throughout the life cycle. The metabolic and contractile phenotypes of muscle fibres also show significant plasticity with respect to environmental conditions, migration and spawning. Many genes regulating muscle growth are found as multiple copies as a result of paralogue retention following whole-genome duplication events in teleost lineages. The extent to which indeterminate growth, ectothermy and paralogue preservation have resulted in modifications of the genetic pathways regulating muscle growth in teleosts compared to mammals largely remains unknown. This review describes the use of compensatory growth models, transgenesis and tissue culture to explore the mechanisms of muscle growth in teleosts and provides some perspectives on future research directions. [ABSTRACT FROM AUTHOR]

The article presents a study which explores the use of an Extant Phylogenetic Bracket approach in order to examine the thoracic epaxial musculature of diplodocid and dicraeosaurid sauropods. In order to reconstruct the thoracic epaxial muscles of sauropods, researchers used the topographic indicators of muscle attachment locations. Researchers observed three epaxial muscle groups located in the dorsal vertebral column. They found that the thoracic epaxial musculature in eusauropods is significant for trunk support, and its variation in other eusauropods is directly linked to bony support structures.

The aim of this study has been the biochemical demonstration of the presence of γ-aminobutyric acid (GABA) in the Mediterranean sea fan Eunicella cavolini by means of high-performance liquid chromatography, and the description of the distribution pattern of GABA and its related molecules, glutamic acid decarboxylase (GAD), vesicular GABA transporter (VGAT) and one of the GABA receptors (GABAB R) by immunohistochemical methods. The interrelationships of GABA, GAD and GABA receptor immunoreactivity have been established by using double-immunohistochemical methods and confocal microscopy. The immunodetection of monoclonal and/or polyclonal antibodies has revealed GABA immunoreactivity throughout the polyp tissue, both in neuronal and non-neuronal elements. GAD immunoreactivity has been mostly localized in the neuronal compartment, contacting epithelial and muscular elements. GABAB R immunoreactivity appears particularly intense in the nematocytes and in the oocyte envelope; its presence in GAD-immunoreactive neurons in the tentacles suggests an autocrine type of regulation. Western blot analysis has confirmed that a GABAB R, with a molecular weight of 142 kDa, similar to that of rat brain, is present in E. cavolini polyp tissue. The identification of the sites of the synthesis, vesicular transport, storage and reception of GABA strongly suggests the presence of an almost complete set of GABA-related molecules for the functioning of the GABAergic system in this simple nervous system. The distribution of these different immunoreactivities has allowed us to hypothesize GABA involvement in nematocyst discharge, in body wall and enteric muscular contraction, in neuronal integration and in male gametocyte differentiation. [ABSTRACT FROM AUTHOR]

Dicentrarchus labrax is a major finfish of interest in Mediterranean aquaculture. As the development of its hatchery production had gone with an increase of its larval rearing temperature, we studied the effect of a constant high (20°C) and two lower (13 and 15°C) temperatures on its early white muscle growth, with developmental and allometric approaches. D. labrax, sampled at hatching and at three developmental stages corresponding to main events in fish early life (first exogenous feeding, notochord flexion and completion of fin ray counts), were histologically processed in order to follow changes in the white myotomal muscle size, cellularity and localisation of proliferative nuclei. Morphometric analyses showed that, for 13, 15 and 20°C incubated/reared D. labrax, the total cross-sectional area of white muscle increased slowly in eleutheroembryos shorter than 5.2 mm, and four times faster in longer fish (free-swimming larvae). White muscle growth occurred both by hypertrophy (increase in muscle fibre size) and hyperplasia (increase in total number of muscle fibres) in all sampled fish, but both processes were higher in free-swimming larvae than in eleutheroembryos. The morphometric establishment of a higher hyperplastic growth of white muscle in free-swimming larvae was confirmed at immunological level by a high occurrence of proliferative nuclei. Early thermal environment was demonstrated to affect the growth process of white muscle on a different way in eleutheroembryos and free-swimming larvae: in the former, white muscle hypertrophy was stimulated at 20°C and hyperplasia at lower temperature, whereas in the latter, both white muscle hypertrophy and hyperplasia were more stimulated at 20°C than at lower temperatures. This was verified at once when the fish length and the white muscle total cross-sectional area were used as explicative variables. [ABSTRACT FROM AUTHOR]

A detailed description of the postcranial skeleton of the Hyposaurinae is presented, based on the hitherto known and new postcranial material. The postcranial skeleton of the hyposaurine Dyrosauridae differs from that of all other crocodilians by the high neural spines, which can reach up to four times the length of the vertebral body, thoracic ribs, which are five times longer than the adjacent vertebral body, dorsal osteoderms lacking an external keel, deep haemal arches, which reach up to 3·4 times the length of the vertebral body, an ilium with a prominent craniodorsal tubercle, and a scapula with an expanded and lateromedially flattened scapular wing, which makes the scapula 1·5 times as large as the coracoid. The similarity of the postcranium of Dyrosaurus, Hyposaurus, Congosaurus and Rhabdognathus allows a uniform skeletal reconstruction for the Hyposaurinae. Only fragmentary material is known from the Phosphatosaurinae. The comparative osteological description of all hyposaurine specimens known to date establishes a basis for future constructional morphological analyses and the reconstruction of their evolutionary history. [ABSTRACT FROM AUTHOR]

BSTRACT: Ocean-ranched and farm-reared Atlantic salmon were compared on the basis of compositional and functional/mechanical properties of the raw and the corresponding smoked muscle. Several procedures based on different salting methods (brine and dry salting) and smoking temperature (20 °C and 30 °C) were tested, as well as an electrostatic smoking method. Also, raw material samples were studied without and with frozen storage (-20 °C) for 30 d prior to salting/smoking, and the effect of frozen storage on the smoked muscle was evaluated. The electrostatic method induced considerably lower shear force values than the other smoking treatments. Ocean-ranched salmon were more susceptible to protein aggregation and loss of binding properties (water and fat) than farmed fish as a consequence of frozen storage of the raw material or smoking treatment. [ABSTRACT FROM AUTHOR]