Microplastic ingestion in five demersal, bathydemersal and bathypelagic fish species from the eastern Weddell Sea, Antarctica.

Antarctica has traditionally been viewed as a relatively isolated ecosystem. Although still considered pristine, it is increasingly also being affected by microplastic pollution. Reported high sea floor concentrations raise concern that these ecosystems might act as major sink for microplastic pollution. This is significant as species in those remote ecosystems are likely more sensitive to rapid environmental change due to a high level of specialization, and lower tolerance levels. Microplastic ingestion in fish has barely been assessed in high latitude environments. Here we aimed to provide baseline data for the eastern Weddell Sea, which is particularly remote, and suggested for an area of conservation. By analyzing gastrointestinal tracts of 40 specimens from five species, we report an overall microplastic incidence rate of 0.23. This is lower than recent studies have found for other species in the Southern Ocean, and below global means. The highest incidence rate was detected in L. squamifrons (0.67), followed by P. evansii (0.29). The most common polymer was polyethylene recovered as 8 particles (42.1 %) from one specimen, while from the remaining 11 microplastics polyester was most common (36.8 %). This study shows that even in a remote region of the Antarctic Ocean with almost no vessel traffic, fisheries or touristic activity, bathydemersal and bathypelagic fish exhibit microplastic particles in their gastrointestinal tract.

Fitting fangs in a finite face: A novel fang accommodation strategy in a 280-million-year-old ray-finned fish.

Though Paleozoic ray-finned fishes are considered to be morphologically conservative, we report a novel mode of fang accommodation (i.e., the fitting of fangs inside the jaw) in the Permian actinopterygian †Brazilichthys macrognathus, whereby the teeth of the lower jaw insert into fenestrae of the upper jaw. To better understand how fishes have accommodated lower jaw fangs through geologic time, we synthesize the multitude of ways living and extinct osteichthyans have housed large mandibular dentition. While the precise structure of fang accommodation seen in †Brazilichthys has not been reported in any other osteichthyans, alternate strategies of upper jaw fenestration to fit mandibular fangs are present in some extant ray-finned fishes-the needlejaws Acestrorhynchus and the gars of the genus Lepisosteus. Notably, out of our survey, only the two aforementioned neopterygians bear upper jaw fenestration for the accommodation of mandibular fangs. We implicate the kinetic jaws of neopterygians in this trend, whereby large mandibular fangs are more easily fit between the multitude of upper jaw and palatal bones. The restricted space available in early osteichthyan jaws may have led to a proliferation of novel ways to accommodate large dentition. We recommend a greater survey of Paleozoic actinopterygian jaw morphology, in light of these results and other recent reevaluations of jaw structure in early fossil ray-fins.

Review of the parasitic nematodes of marine fishes from off the American continent.

The ichthyofauna of the Atlantic and Pacific coasts off the American continent is very rich. Consequently, a high biodiversity of nematodes parasitizing these vertebrates is also expected. Currently, data on nematode parasites of marine fish off the Americas are fragmented. A review of all adult nematode species reported parasitizing marine fish from off the American continent is herein presented, as well as comments on their patterns of diversity, life cycles and advances in the taxonomic and phylogenetic knowledge. A total of 209 valid species, 19 species inquirendae and 6 dubious records have been recorded, the majority from the fish taxa Eupercaria and Perciformes. The families Sciaenidae, Serranidae and Lutjanidae, as well as the tropical and temperate Atlantic waters, exhibited the highest records of parasitic nematodes. The Cucullanidae, Philometridae and Cystidicolidae were the most speciose families of nematodes, which may be related to technological advances and relatively recent efforts of taxonomists, resulting in description of new taxa and the resolution of taxonomic problems. Numerous taxonomic questions still need resolution and, even though genetic data have been important for this process, the database is very scarce. This is the first review on all currently known nematode species parasitizing marine fish off the Americas and may serve as an important basis of reference for future approaches on these organisms.

Lung evolution in vertebrates and the water-to-land transition.

A crucial evolutionary change in vertebrate history was the Palaeozoic (Devonian 419-359 million years ago) water-to-land transition, allowed by key morphological and physiological modifications including the acquisition of lungs. Nonetheless, the origin and early evolution of vertebrate lungs remain highly controversial, particularly whether the ancestral state was paired or unpaired. Due to the rarity of fossil soft tissue preservation, lung evolution can only be traced based on the extant phylogenetic bracket. Here we investigate, for the first time, lung morphology in extensive developmental series of key living lunged osteichthyans using synchrotron x-ray microtomography and histology. Our results shed light on the primitive state of vertebrate lungs as unpaired, evolving to be truly paired in the lineage towards the tetrapods. The water-to-land transition confronted profound physiological challenges and paired lungs were decisive for increasing the surface area and the pulmonary compliance and volume, especially during the air-breathing on land.

All life on Earth started out under water. However, around 400 million years ago some vertebrates, such as fish, started developing limbs and other characteristics that allowed them to explore life on land. One of the most pivotal features to evolve was the lungs, which gave vertebrates the ability to breathe above water. Most land-living vertebrates, including humans, have two lungs which sit on either side of their chest. The lungs extract oxygen from the atmosphere and transfer it to the bloodstream in exchange for carbon dioxide which then gets exhaled out in to the atmosphere. How this important organ first evolved is a hotly debated topic. This is largely because lung tissue does not preserve well in fossils, making it difficult to trace how the lungs of vertebrates changed over the course of evolution. To overcome this barrier, Cupello et al. compared the lungs of living species which are crucial to understand the early stages of the water-to-land transition. This included four species of lunged bony fish which breathe air at the water surface, and a four-legged salamander that lives on land. Cupello et al. used a range of techniques to examine how the lungs of the bony fish and salamander changed shape during development. The results suggested that the lungs of vertebrates started out as a single organ, which became truly paired later in evolution once vertebrates started developing limbs. This anatomical shift increased the surface area available for exchanging oxygen and carbon dioxide so that vertebrates could breathe more easily on land. These findings provide new insights in to how the lung evolved into the paired structure found in most vertebrates alive today. It likely that this transition allowed vertebrates to fully adapt to breathing above water, which may explain why this event only happened once over the course of evolution.

The complex rostral morphology and the endoskeleton ossification process of two adult samples of Xiphias gladius (Xiphiidae).

The authors studied the morphology of the upper and lower jaws, vertebrae and dorsal-fin rays of the teleost fish Xiphias gladius to analyse the skeletal architecture and ossification pattern. The analogies and differences among these segments were investigated to identify a common morphogenetic denominator of the bone tissue osteogenesis and modeling. The large fat glands in the proximal upper jaw and their relationship to the underlying cartilage (absent in the lower jaw) suggested that there is a mechanism that explains rostral overgrowth in the Xiphiidae and Istiophoriidae families. Thus far, the compact structure of the distal rostrum has been interpreted as being the result of remodeling. Nonetheless, no evidence of cutting cones, scalloped outer border of osteons and sequence of bright-dark bands in polarized light was observed in this study, suggesting a primary osteon texture formed by compacting of collagen matrix and mineral deposition in the fat stroma lacunae of the bone, but without being oriented in layers of the collagen fibrils. A similar histology also characterizes the circular structures present in the other examined segments of the skeleton. The early phases of fibrillogenesis carried out by fibroblast-like cells occurred farther from the already-calcified bone surface inside the fat stroma lacunae. The fibrillar matrix was compacted and underwent mineral deposition near the previously calcified bone surface. This pattern of collagen matrix synthesis and calcification was different from that of mammalian osteoblasts, especially concerning the ability to build a lacuno-canalicular system among cells. Necrosis or apoptosis of the latter and refilling of the empty lacunae by mineral deposits might explain the anosteocytic bone formation.

A severe microsporidian disease in cultured Atlantic Bluefin Tuna (Thunnus thynnus).

One of the most promising aquaculture species is the Atlantic bluefin tuna (Thunnus thynnus) with high market value; disease control is crucial to prevent and reduce mortality and monetary losses. Microsporidia (Fungi) are a potential source of damage to bluefin tuna aquaculture. A new microsporidian species is described from farmed bluefin tunas from the Spanish Mediterranean. This new pathogen is described in a juvenile associated with a highly severe pathology of the visceral cavity. Whitish xenomas from this microsporidian species were mostly located at the caecal mass and ranged from 0.2 to 7.5 mm. Light and transmission electron microscopy of the spores revealed mature spores with an average size of 2.2 × 3.9 µm in size and a polar filament with 13-14 coils arranged in one single layer. Phylogenetic analysis clustered this species with the Glugea spp. clade. The morphological characteristics and molecular comparison confirm that this is a novel microsporidian species, Glugea thunni. The direct life-cycle and the severe pathologies observed makes this parasite a hard risk for bluefin tuna cultures.

Comparative anatomical studies on the cranial nerves of the fully formed embryos of the Nile tilapia Oreochromis niloticus (Ostiechthyes-Cichlidae). I. Nervus glossopharyngeus / Estudos anatômicos comparativos dos nervos cranianos de embriões totalmente formados da tilápia do Nilo Oreochromis niloticus (Ostiechthyes-Cichlidae). I. Nervus glossopharyngeus

The organization of the roots, ganglia and the peripheral distribution of the cranial nerves of the fully formed embryos of Oreochromis niloticus are examined in the transverse serial sections. These nerves carry fibers, which were also analyzed. The results of this study demonstrated that the glossopharyngeal nerve originates by means of only one root, which leaves the cranium through the glossopharyngeal foramen. This nerve gives fibers (visceromotor) to the first internal and external levator arcus branchialis muscles. There is a single epibranchial (petrosal) ganglion located extracranially. Nervus glossopharyngeus has three rami; pharyngeus, pretramticus and posttrematicus. The ramus pharyngeus carries only viscerosensory fibers; general for the pharyngeal epithelium and special ones for the pseudobranch. General viscerosensory fibers are also carried by rami pretrematicus and posttrematicus for the pharyngeal epithelial lining. The special sensory fibers are carried by the ramus pretrematicus for the taste buds and by ramus posttrematicus for the gill filaments. The ramus pretrematicus also carries visceromotor fibers for the first adductor arcus branchialis and to the first obliquus ventralis muscles.

A organização das raízes, gânglios e a distribuição periférica dos nervos cranianos dos embriões totalmente formados de Oreochromis niloticus são examinados nas seções transversais seriais. Esses nervos carregam fibras, que também foram analisadas. Os resultados deste estudo demonstraram que o nervo glossofaríngeo se origina por meio de apenas uma raiz, que sai do crânio pelo forame glossofaríngeo. Este nervo fornece fibras (visceromotoras) para os primeiros músculos levantadores do arco branquial interno e externo. Existe um único gânglio epibranquial (petroso) localizado extracranialmente. Nervus glossopharyngeus tem três ramos; faríngeo, pretramticus e póstrematicus. O ramo faríngeo contém apenas fibras viscerossensoriais ­ gerais para o epitélio faríngeo e especiais para o pseudobrânquio. Fibras viscerossensoriais gerais também são transportadas por ramos pretrematicus e posttrematicus para o revestimento epitelial da faringe. As fibras sensoriais especiais são transportadas pelo ramus pretrematicus para as papilas gustativas e pelo ramus posttrematicus para os filamentos branquiais. O ramo pretrematicus também carrega fibras visceromotoras para o primeiro adutor arcus branchialis e para o primeiro músculo oblíquo ventral.

Comparative anatomical studies on the cranial nerves of the fully formed embryos of the Nile tilapia Oreochromis niloticus (Ostiechthyes-Cichlidae). I. Nervus glossopharyngeus / Estudos anatômicos comparativos dos nervos cranianos de embriões totalmente formados da tilápia do Nilo Oreochromis niloticus (Ostiechthyes Cichlidae). I. Nervus glossopharyngeus

The organization of the roots, ganglia and the peripheral distribution of the cranial nerves of the fully formed embryos of Oreochromis niloticus are examined in the transverse serial sections. These nerves carry fibers, which were also analyzed. The results of this study demonstrated that the glossopharyngeal nerve originates by means of only one root, which leaves the cranium through the glossopharyngeal foramen. This nerve gives fibers (visceromotor) to the first internal and external levator arcus branchialis muscles. There is a single epibranchial (petrosal) ganglion located extracranially. Nervus glossopharyngeus has three rami; pharyngeus, pretramticus and posttrematicus. The ramus pharyngeus carries only viscerosensory fibers; general for the pharyngeal epithelium and special ones for the pseudobranch. General viscerosensory fibers are also carried by rami pretrematicus and posttrematicus for the pharyngeal epithelial lining. The special sensory fibers are carried by the ramus pretrematicus for the taste buds and by ramus posttrematicus for the gill filaments. The ramus pretrematicus also carries visceromotor fibers for the first adductor arcus branchialis and to the first obliquus ventralis muscles.

A organização das raízes, gânglios e a distribuição periférica dos nervos cranianos dos embriões totalmente formados de Oreochromis niloticus são examinados nas seções transversais seriais. Esses nervos carregam fibras, que também foram analisadas. Os resultados deste estudo demonstraram que o nervo glossofaríngeo se origina por meio de apenas uma raiz, que sai do crânio pelo forame glossofaríngeo. Este nervo fornece fibras (visceromotoras) para os primeiros músculos levantadores do arco branquial interno e externo. Existe um único gânglio epibranquial (petroso) localizado extracranialmente. Nervus glossopharyngeus tem três ramos; faríngeo, pretramticus e póstrematicus. O ramo faríngeo contém apenas fibras viscerossensoriais — gerais para o epitélio faríngeo e especiais para o pseudobrânquio. Fibras viscerossensoriais gerais também são transportadas por ramos pretrematicus e posttrematicus para o revestimento epitelial da faringe. As fibras sensoriais especiais são transportadas pelo ramus pretrematicus para as papilas gustativas e pelo ramus posttrematicus para os filamentos branquiais. O ramo pretrematicus também carrega fibras visceromotoras para o primeiro adutor arcus branchialis e para o primeiro músculo oblíquo ventral.

Comparative anatomical studies on the cranial nerves of the fully formed embryos of the Nile tilapia Oreochromis niloticus (Ostiechthyes-Cichlidae). I. Nervus glossopharyngeus

Abstract The organization of the roots, ganglia and the peripheral distribution of the cranial nerves of the fully formed embryos of Oreochromis niloticus are examined in the transverse serial sections. These nerves carry fibers, which were also analyzed. The results of this study demonstrated that the glossopharyngeal nerve originates by means of only one root, which leaves the cranium through the glossopharyngeal foramen. This nerve gives fibers (visceromotor) to the first internal and external levator arcus branchialis muscles. There is a single epibranchial (petrosal) ganglion located extracranially. Nervus glossopharyngeus has three rami; pharyngeus, pretramticus and posttrematicus. The ramus pharyngeus carries only viscerosensory fibers; general for the pharyngeal epithelium and special ones for the pseudobranch. General viscerosensory fibers are also carried by rami pretrematicus and posttrematicus for the pharyngeal epithelial lining. The special sensory fibers are carried by the ramus pretrematicus for the taste buds and by ramus posttrematicus for the gill filaments. The ramus pretrematicus also carries visceromotor fibers for the first adductor arcus branchialis and to the first obliquus ventralis muscles.

Resumo A organização das raízes, gânglios e a distribuição periférica dos nervos cranianos dos embriões totalmente formados de Oreochromis niloticus são examinados nas seções transversais seriais. Esses nervos carregam fibras, que também foram analisadas. Os resultados deste estudo demonstraram que o nervo glossofaríngeo se origina por meio de apenas uma raiz, que sai do crânio pelo forame glossofaríngeo. Este nervo fornece fibras (visceromotoras) para os primeiros músculos levantadores do arco branquial interno e externo. Existe um único gânglio epibranquial (petroso) localizado extracranialmente. Nervus glossopharyngeus tem três ramos; faríngeo, pretramticus e póstrematicus. O ramo faríngeo contém apenas fibras viscerossensoriais gerais para o epitélio faríngeo e especiais para o pseudobrânquio. Fibras viscerossensoriais gerais também são transportadas por ramos pretrematicus e posttrematicus para o revestimento epitelial da faringe. As fibras sensoriais especiais são transportadas pelo ramus pretrematicus para as papilas gustativas e pelo ramus posttrematicus para os filamentos branquiais. O ramo pretrematicus também carrega fibras visceromotoras para o primeiro adutor arcus branchialis e para o primeiro músculo oblíquo ventral.

The oldest Devonian circumpolar ray-finned fish?

Actinopterygians (ray-finned fishes) are the most diverse group of living fishes, but have a sparse Devonian fossil record restricted to low palaeolatitudes. Here we report a new actinopterygian from the Paraná Basin of Brazil, which occupied a circumpolar position in the Palaeozoic. Available geological evidence supports a Middle Devonian or older age for this taxon, which shares features of the mandibular symphysis with the latest Devonian Tegeolepis. A phylogenetic analysis resolves these two as sister taxa. This new record expands the palaeogeographic distribution of Devonian ray-fins and suggests that gaps in their fossil record might be filled by exploring poorly sampled high-latitude localities within the Malvinokaffric Realm.

Fish Behavior for the Exotic Pet Practitioner.

Interpreting fish behavior is an important component of providing veterinary care. There are over 28,000 species of fish and while only a handful are commonly encountered by exotic pet and public display veterinarians, there are still hundreds of species to consider. Three models-natural history (species typical modal action patterns), medical (disease state), and learning experience (classical and operant conditioning)-are useful for taking an actionable, holistic approach to interpreting behavior. Models help clinicians formulate appropriate differentials, ensuring they do not exclusively consider disease, particularly in unfamiliar species.

Description of Raphidascaris (Ichthyascaris) multipapillata sp. nov., Redescription of Hysterothylacium simile Li et al., 2013 and New Records of Some Other Ascaridoid and Seuratoid Nematodes from Marine Fishes in Japan.

PURPOSE: Many nematode species parasitizing marine fishes were reported from Japanese waters. However, considering the wealth of fish species in this zoogeographically interesting region and the host specificity of nematodes, the number of hitherto recorded fish nematodes probably represents only a very small part of the potential Japanese fauna of these organisms. Therefore, new data are needed to recognise the species composition of these parasites in this region. METHODS: Helminthological examinations of some marine fishes from off Japan, carried out in the years 2005-2017, revealed one new and five insufficiently known species of ascaridoid and seuratoid nematodes. These were studied with the use of light and scanning electron microscopy. RESULTS: All six nematode species recorded are described: Anisakidae: Raphidascaris (Ichthyascaris) multipapillata sp. nov. (male and females) from the intestine of Labracoglossa argenteiventris Peters (Kyphosidae) in the Sea of Japan, Raphidascaris (Ichthyascaris) sp. (third-stage larvae) probably from the digestive tract of Seriola dumerili (Risso) and S. rivoliana Valenciennes (both Carangidae) in the western North Pacific Ocean off Ishigaki-jima Island, Okinawa Prefecture, Hysterothylacium simile Li et al., 2013 (males and females) from the stomach of Lateolabrax japonicus (Cuvier) (Lateolabracidae) in the Sea of Japan, Hysterothylacium sp. 1 (female) from the pyloric caeca of Jaydia lineata (Temminck et Schlegel) (Apogonidae) in the Seto Inland Sea, Hysterothylacium sp. 2 (third- and fourth-stage larvae) from the intestine and mesentery of Etelis coruscans Valenciennes (Lutjanidae) and Pseudorhombus pentophthalmus Günther (Paralichthyidae) in the western North Pacific Ocean off Ishigaki-jima Island, Okinawa Prefecture and the Seto Inland Sea, respectively; and Cucullanidae: Cucullanus sp. (female) from the intestine of Semicossyphus reticulatus (Valenciennes) (Labridae) in the Seto Inland Sea. Raphidascaris (I.) multipapillata sp. n. differs from congeners mainly in the high number (79) of pairs of caudal papillae, spicules 402 µm long and in the structure of the male and female tail tips. Hysterothylacium simile is redescribed, being recorded from off Japan for the first time. CONCLUSIONS: In addition to the discovery of the new nematode species R. (I.) multipapillata sp. nov. and a redescription of H. simile providing some new morphological data of this parasite, the findings of all other species represent new host and geographical records. The present study extends the knowledge of the species composition and host-parasite relationships of nematodes parasitizing marine fishes.

Major Histocompatibility Complex in Osteichthyes.

Based on analysis of available genome sequences, five gene lineages of MHC class I molecules (MHC I-U, -Z, -S, -L and -P) and one gene lineage of MHC class II molecules (MHC II-D) have been identified in Osteichthyes. In the latter lineage, three MHC II molecule sublineages have been identified (MHC II-A, -B and -E). As regards MHC class I molecules in Osteichthyes, it is important to take note of the fact that the lineages U and Z in MHC I genes have been identified in almost all fish species examined so far. Phylogenetic studies into MHC II molecule genes of sublineages A and B suggest that they may be descended from the genes of the sublineage named A/B that have been identified in spotted gar (Lepisosteus oculatus). The sublineage E genes of MHC II molecules, which represent the group of non-polymorphic genes with poor expression in the tissues connected with the immune system, are present in primitive fish, i.e. in paddlefish, sturgeons and spotted gar (Lepisosteus oculatus), as well as in cyprinids (Cyprinidae), Atlantic salmon (Salmo salar), and rainbow trout (Oncorhynchus mykiss). Full elucidation of the details relating to the organisation and functioning of the particular components of the major histocompatibility complex in Osteichthyes can advance the understanding of the evolution of the MHC molecule genes and the immune mechanism.

Tooth replacement in early sarcopterygians.

Teeth were an important innovation in vertebrate evolution but basic aspects of early dental evolution remain poorly understood. Teeth differ from other odontode organs, like scales, in their organized, sequential pattern of replacement. However, tooth replacement patterns also vary between the major groups of jawed vertebrates. Although tooth replacement in stem-osteichthyans and extant species has been intensively studied it has been difficult to resolve scenarios for the evolution of osteichthyan tooth replacement because of a dearth of evidence from living and fossil sarcopterygian fishes. Here we provide new anatomical data informing patterns of tooth replacement in the Devonian sarcopterygian fishes Onychodus, Eusthenopteron and Tiktaalik and the living coelacanth Latimeria based on microfocus- and synchrotron radiation-based X-ray microtomography. Early sarcopterygians generated replacement teeth on the jaw surface in a pattern similar to stem-osteichthyans, with damaged teeth resorbed and replacement teeth developed on the surface of the bone. However, resorption grades and development of replacement teeth vary spatially and temporally within the jaw. Particularly in Onychodus, where teeth were also shed through anterior rotation and resorption of bone at the base of the parasymphyseal tooth whorl, with new teeth added posteriorly. As tooth whorls are also present in more stem-osteichthyans, and statodont tooth whorls are present among acanthodians (putative stem-chondrichthyans), rotational replacement of the anterior dentition may be a stem-osteichthyan character. Our results suggest a more complex evolutionary history of tooth replacement.

Fish Otoliths from the Cabarruyan Piacenzian-Gelasian fauna found in the Philippines.

We studied fish otoliths from twelve sediment samples of a well-preserved late Pliocene to early Pleistocene fauna originally from the northwest Philippines that were originally deposited in relatively deepwater marine environment. The fish fauna is systematically described, its paleoenvironmental character is explored, and its diversity is analyzed. Four unknown species have been encountered: Parascombrops schwarzhansi n. sp., Maurolicus sp., Pteropsaron sp., and Priolepis sp., of which one is described as new species and three were left in open nomenclature as their local recent counterparts are not well known yet. In addition, a variant Benthosema, Benthosema aff. fibulatum, is described. Overall, fifty-three taxa of fish otoliths were found, of which eighteen were identified at the species level and an additional twenty-seven at the genus level. Most extant species nowadays occur around the Philippines in relatively deep water (about 200 m depth), which is congruent with earlier studies on mollusks and echinoderms from the same deposits. This is the first study on a fossil fish otolith assemblage from the Philippines. Its diversity is very high and analysis by rarefaction curves suggests that additional sampling would add more fish species to the presented fauna list.

Vitellogenin receptor and fatty acid profiles of individual lipid classes of oocytes from wild and captive-reared greater amberjack (Seriola dumerili) during the reproductive cycle.

The greater amberjack Seriola dumerili (Risso, 1810) is a large migratory pelagic fish occurring in tropical and temperate waters with a great potential for the world aquaculture industry. Previous studies showed that wild-caught female greater amberjack reared in sea cages and handled during the reproductive season, underwent extensive ovarian atresia. This atresia, however, was not related to an insufficient liver transcription or oocyte uptake of vitellogenin (Vtg). In the present study, the structure of two greater amberjack vitellogenin receptors, namely Vtgr (Lr8-) and Lrp13, was characterized. Moreover, vtgr and lrp13 gene expression and the fatty acid profiles of specific phospholipids and neutral lipids were compared in the ovaries of wild and captive-reared greater amberjack during different phases of the reproductive cycle (i.e. early gametogenesis, advanced gametogenesis and spawning). Ovarian vtgr and lrp13 transcription was more active during early gametogenesis, suggesting that vitellogenin receptor transcripts were synthesized by previtellogenic oocytes and remained in the cellular mRNA pool until oocytes resumed meiosis and entered into secondary growth (i.e. vitellogenesis). Rearing of wild-caught greater amberjack in captivity together with handling during the reproductive season was associated with a reduced vtgr and lrp13 transcription and with a diminished capacity of oocytes in the early phase of gametogenesis (primary oocyte growth) to enter into vitellogenesis. During early gametogenesis, remarkable differences in the fatty acid composition were observed between wild and captive-reared individuals: all phospholipids of captive fish displayed dramatic increases of saturates (16:0 and 18:0) and decreases of arachidonic acid (ARA) and docosahexaenoic acid (DHA). The present study confirms the susceptibility of greater amberjack reproductive function to handling stress and suggests that the consequent extensive atresia of vitellogenic follicles originated during the primary oocytes growth when the capacity of oocytes to synthesize vitellogenin receptors was reduced. The study also suggests that this reduced capacity was associated with an altered oocyte phospholipid fatty acid composition during early gametogenesis.

Specific humoral immunity in Osteichthyes.

The fish immune system is extremely complex and has considerable adaptive potential. In Osteichthyes, the system is formed by lymphopoietic organs which are important for the differentiation and maturation of the immune system cells. These organs include the anterior kidney (phronephros), the thymus, the spleen, the posterior kidney (mesonephros), and mucosa-associated lymphoid tissues (MALT). Apart from the lymphocytic organs and the MALT system, the immune system components include defensive cells and their products. Those identified in fish include, inter alia, monocytes/macrophages, melanomacrophages, neutrophilic granulocytes, thrombocytes, B cells, plasma cells, and T cells. The roles of the individual components of the organisation of the immune system, the organs, and lymphoid tissue as well as the constituents conditioning the innate and adaptive immunity mechanisms are considered equally important, especially in the context of functional interdependence. The progress in the exploration of the processes of specific humoral immunity in Osteichthyes and the possibilities of their practical application is increasingly promising in view of the expected need for protection of fish against diseases. The paper discusses selected issues concerning recent knowledge about haematopoiesis of B cells, plasmablasts, plasma cells, and immunoglobulins (IgM, IgD, IgT/IgZ).

Evolution of the facial musculature in basal ray-finned fishes.

BACKGROUND: The facial musculature is a remarkable anatomical complex involved in vital activities of fishes, such as food capture and gill ventilation. The evolution of the facial muscles is largely unknown in most major fish lineages, such as the Actinopterygii. This megadiverse group includes all ray-finned fishes and comprises approximately half of the living vertebrate species. The Polypteriformes, Acipenseriformes, Lepisosteiformes, Amiiformes, Elopiformes, and Hiodontiformes occupy basal positions in the actinopterygian phylogeny and a comparative study of their facial musculature is crucial for understanding the cranial evolution of bony fishes (Osteichthyes) as a whole. RESULTS: The facial musculature of basal actinopterygians is revised, redescribed, and analyzed under an evolutionary perspective. We identified twenty main muscle components ontogenetically and evolutionarily derived from three primordial muscles. Homologies of these components are clarified and serve as basis for the proposition of a standardized and unifying myological terminology for all ray-finned fishes. The evolutionary changes in the facial musculature are optimized on the osteichthyan tree and several new synapomorphies are identified for its largest clades, including the Actinopterygii, Neopterygii, and Teleostei. Myological data alone ambiguously support the monophyly of the Holostei. A newly identified specialization constitutes the first unequivocal morphological synapomorphy for the Elopiformes. The myological survey additionally allowed a reinterpretation of the homologies of ossifications in the upper jaw of acipenseriforms. CONCLUSIONS: The facial musculature proved to be extremely informative for the higher-level phylogeny of bony fishes. These muscles have undergone remarkable changes during the early radiation of ray-finned fishes, with significant implications for the knowledge of the musculoskeletal evolution of both derived actinopterygians and lobe-finned fishes (Sarcopterygii).

Neurocranial anatomy of an enigmatic Early Devonian fish sheds light on early osteichthyan evolution.

The skull of 'Ligulalepis' from the Early Devonian of Australia (AM-F101607) has significantly expanded our knowledge of early osteichthyan anatomy, but its phylogenetic position has remained uncertain. We herein describe a second skull of 'Ligulalepis' and present micro-CT data on both specimens to reveal novel anatomical features, including cranial endocasts. Several features previously considered to link 'Ligulalepis' with actinopterygians are now considered generalized osteichthyan characters or of uncertain polarity. The presence of a lateral cranial canal is shown to be variable in its development between specimens. Other notable new features include the presence of a pineal foramen, the some detail of skull roof sutures, the shape of the nasal capsules, a placoderm-like hypophysial vein, and a chondrichthyan-like labyrinth system. New phylogenetic analyses place 'Ligulalepis' as a stem osteichthyan, specifically as the sister taxon to 'psarolepids' plus crown osteichthyans. The precise position of 'psarolepids' differs between parsimony and Bayesian analyses.

Genome-wide comparison of the protein-coding repertoire reveals fast evolution of immune-related genes in cephalochordates and Osteichthyes superclass.

Amphioxus is used to investigate the origin and evolution of vertebrates. To better understand the characteristics of genome evolution from cephalochordates to Osteichthyes, we conducted a genome-wide pairwise comparison of protein-coding genes within amphioxus (a comparable group) and parallel analyses within Osteichthyes (two comparable groups). A batch of fast-evolving genes in each comparable group was identified. Of these genes, the most fast-evolving genes (top 20) were scrutinized, most of which were involved in immune system. An analysis of the fast-evolving genes showed that they were enriched into gene ontology (GO) terms and pathways primarily involved in immune-related functions. Similarly, this phenomenon was detected within Osteichthyes, and more well-known and abundant GO terms and pathways involving innate immunity were found in Osteichthyes than in cephalochordates. Next, we measured the expression responses of four genes belonging to metabolism or energy production-related pathways to lipopolysaccharide challenge in the muscle, intestine or skin of B. belcheri; three of these genes (HMGCL, CYBS and MDH2) showed innate immune responses. Additionally, some genes involved in adaptive immunity showed fast evolution in Osteichthyes, such as those involving "intestinal immune network for IgA production" or "T-cell receptor signaling pathway". In this study, the fast evolution of immune-related genes in amphioxus and Osteichthyes was determined, providing insights into the evolution of immune-related genes in chordates.