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Teleosts
Kinds of Teleosts Terms modified by Teleosts Selected AbstractsFirst cloning and functional characterization of a melatonin receptor in fish brain: a novel one?JOURNAL OF PINEAL RESEARCH, Issue 2 2002Pascaline Gaildrat Melatonin, a neuroendocrine transducer of photoperiod, influences a number of physiological functions and behaviors through specific seven transmembrane domains receptors. We report here the first full-length cloning and functional characterization of a melatonin receptor (P2.6) in a fish, the pike (Teleost). P2.6 encodes a protein that is ,80% identical to melatonin receptors previously isolated partially in non-mammals and classified as members of the Mel1b subtype; but, it shares only 61% identity with the full-length human Mel1b melatonin receptor (hMT2). Expression of P2.6 results in ligand binding characteristics similar to that described for endogenous melatonin receptors. Selective antagonists of the hMT2 (4-phenyl-2-propionamidotetraline and luzindole) were poor competitors of 2-[125I]iodomelatonin binding to the recombinant receptor. In Chinese hamster ovary cells expressing both the cystic fibrosis transmembrane conductance regulator chloride channel and P2.6 receptor, melatonin counteracted the forskolin induced activation of the channel. The results are best explained by a selective inhibition of the adenylyl cyclase. By reverse transcription-polymerase chain reaction, P2.6 mRNA appeared expressed in the optic tectum and, to lesser extent, in the retina and pituitary. In conclusion, these results, together with those of a phylogenetic analysis, suggest that P2.6 might belong to a distinct subtype group within the vertebrate melatonin receptor family. [source] Genome duplication, subfunction partitioning, and lineage divergence: Sox9 in stickleback and zebrafishDEVELOPMENTAL DYNAMICS, Issue 3 2003William A. Cresko Abstract Teleosts are the most species-rich group of vertebrates, and a genome duplication (tetraploidization) event in ray-fin fish appears to have preceded this remarkable explosion of biodiversity. What is the relationship of the ray-fin genome duplication to the teleost radiation? Genome duplication may have facilitated lineage divergence by partitioning different ancestral gene subfunctions among co-orthologs of tetrapod genes in different teleost lineages. To test this hypothesis, we investigated gene expression patterns for Sox9 gene duplicates in stickleback and zebrafish, teleosts whose lineages diverged early in Euteleost evolution. Most expression domains appear to have been partitioned between Sox9a and Sox9b before the divergence of stickleback and zebrafish lineages, but some ancestral expression domains were distributed differentially in each lineage. We conclude that some gene subfunctions, as represented by lineage-specific expression domains, may have assorted differently in separate lineages and that these may have contributed to lineage diversification during teleost evolution. Developmental Dynamics, 2003. © 2003 Wiley-Liss, Inc. [source] The function of the Egr1 transcription factor in cartilage formation and adaptation to microgravity in zebrafish, Danio rerioJOURNAL OF APPLIED ICHTHYOLOGY, Issue 2 2010M. Muller Summary Osteoporosis is one of the major concerns for an ageing human population and for passengers on long-term space flights. Teleosts represent a potentially interesting alternative for studying bone physiology. In zebrafish (Danio rerio), the cartilaginous elements that form the pharyngeal arches derive from cranial neural crest cells, whose proper patterning and morphogenesis require reciprocal interactions with other tissue types such as pharyngeal endoderm, ectoderm and mesoderm. We show how the zebrafish can be used to study the function of signal transduction pathways, such as the Fgf pathway, or that of particular genes, such as the zinc finger transcription factor Egr1, in pharyngeal skeleton formation and maintenance. We investigate the changes caused by microgravity and chemical treatments on zebrafish. We analyze early gene expression modification using whole genome microarray experiments and the long-term consequences by staining bone structures. [source] Intestinal morphology and histology of the striped catfish Pseudoplatystoma fasciatum (Linnaeus, 1766) fed dry dietsAQUACULTURE NUTRITION, Issue 6 2009A.P.O. RODRIGUES Abstract This study unveils histological features of the intestinal tract of juvenile striped catfish Pseudoplatystoma fasciatum (Linnaeus, 1776) in three size classes (weight, standard length): I , 36.84 ± 10.19 g, 14.52 ± 1.54 cm; II , 59.03 ± 11.47 g, 17.17 ± 1.06 cm; III , 89.72 ± 18.70 g, 20.79 ± 1.55 cm, respectively. Histological organization of the juvenile speckled catfish intestine bears features common to the carnivorous fish, but the organ presents some convolutions that indicate a certain degree of dietary flexibility, a surprising trend, common only to omnivorous Siluriforms. The architecture of the mucosa of the speckled catfish intestine indicates that the species concentrates digestion and absorption of nutrients in the medium intestine, a common feature among carnivorous Teleosts. [source] Zebrafish IRX1b in the embryonic cardiac ventricle,DEVELOPMENTAL DYNAMICS, Issue 4 2004Elaine M. Joseph Abstract The synchronous contraction of the vertebrate heart requires a conduction system. While coordinated contraction of the cardiac chambers is observed in zebrafish larvae, no histological evidence yet has been found for the existence of a cardiac conduction system in this tractable teleost. The homeodomain transcription factor gene IRX1 has been shown in the mouse embryo to be a marker of cells that give rise to the distinctive cardiac ventricular conduction system. Here, I demonstrate that zebrafish IRX1b is expressed in a restricted subset of ventricular myocytes within the embryonic zebrafish heart. IRX1b expression occurs as the electrical maturation of the heart is taking place, in a location analogous to the initial expression domain of mouse IRX1. The gene expression pattern of IRX1b is altered in silent heart genetic mutant embryos and in embryos treated with the endothelin receptor antagonist bosentan. Furthermore, injection of a morpholino oligonucleotide targeted to block IRX1b translation slows the heart rate. Developmental Dynamics 231:720,726, 2004. © 2004 Wiley-Liss, Inc. [source] Developmental toxicity of estrogenic alkylphenols in killifish (Fundulus heteroclitus)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2000Sue A. Kelly Abstract Estrogenic alkylphenols have been identified in the aquatic environment, and concern has arisen over the ability of these compounds to interact with and potentially disrupt vertebrate endocrine systems. Here we report that waterborne nonylphenol (NP) and 4- tert -octylphenol (4- t -OP) are toxic to the embryos and larvae of Fundulus heteroclitus, an estuarine teleost, causing both lethal and sublethal developmental abnormalities. Hatch success in surviving embryos is also adversely affected by alkylphenol exposure. Correlation analysis has indicated that decreased hatch success is strongly correlated to deformities in the torso/abdomen and tail of embryos. Larval exposure to the alkylphenols demonstrates that NP and 4- t -OP are lethal at concentrations an order of magnitude less than those lethal to embryos (NP larval 96-h LC50 = 0.95 ,M [204 ,g/L]; NP embryo 96-h LC50 = 24 ,M [5 mg/L]). In evaluating the role of estrogenicity in developmental toxicity of the alkylphenols, we have found that tamoxifen, an estrogen receptor antagonist, can prevent embryo-lethality for NP and 4- t -OP While these embryos survive, some sublethal abnormalities are still evident, particularly in the torso and tail. The results of these studies suggest that the alkylphenols have the potential to cause developmental toxicity in aquatic organisms and that this may occur through disruption of estrogen-based signals. [source] An evolutionary view on tooth development and replacement in wild Atlantic salmon (Salmo salar L.)EVOLUTION AND DEVELOPMENT, Issue 1 2008A. Huysseune SUMMARY To gain an insight into the evolution of tooth replacement mechanisms, we studied the development of first-generation and replacement teeth on the dentary of wild Atlantic salmon (Salmo salar L.), a protacanthopterygian teleost, using serially sectioned heads of early posthatching stages as well as adults. First-generation teeth develop within the oral epithelium. The anlage of the replacement tooth is first seen as a placode-like thickening of the outer dental epithelium of the predecessor, at its lingual and caudal side. Ongoing development of the replacement tooth germ is characterized by the elaboration of a population of epithelial cells, termed here the middle dental epithelium, apposed to the inner dental epithelium on the lingual side of the tooth germ. Before the formation of the new successor, a single-layered outer dental epithelium segregates from the middle dental epithelium. The dental organs of the predecessor and the successor remain broadly interconnected. The absence of a discrete successional dental lamina in salmon stands in sharp contrast to what is observed in other teleosts, even those that share with salmon the extraosseous formation of replacement teeth. The mode of tooth replacement in Atlantic salmon displays several characters similar to those observed in the shark Squalus acanthias. To interpret similarities in tooth replacement between Atlantic salmon and chondrichthyans as a case of convergence, or to see them as a result of a heterochronic shift, requires knowledge on the replacement process in more basal actinopterygian lineages. The possibility that the middle dental epithelium functionally substitutes for a successional lamina, and could be a source of stem cells, whose descendants subsequently contribute to the placode of the new replacement tooth, needs to be explored. [source] Embryo of an annual fish (Austrolebias charrua) in the last dormancy stage, diapause IIIGENESIS: THE JOURNAL OF GENETICS AND DEVELOPMENT, Issue 1 2009Article first published online: 22 JAN 200 Embryo of an annual fish (Austrolebias charrua) in the last dormancy stage, diapause III. The embryo, surrounded by a transparent vitelline envelope, is in the pre-hatching stage. A prominent eye and part of the pigmented body and tail are apparent. Why annual fishes? Annual fishes (Order Cyprinodontiformes) are a special kind of teleost, found in Africa and South America, with developmental strategies closely related to their life cycle. These fishes inhabit temporary pools that undergo drying during summer, when all adults die. The embryos remain buried in the bottom mud and are resistant to desiccation. In the subsequent rainy season they hatch a few hours after the pool is flooded and a new reproductive cycle begins. This developmental pattern is characterized by the presence of a unique stage between cleavage and embryogenesis, dispersion-aggregation of blastomeres and because the embryos show reversible developmental arrests (diapauses) at different stages. Annual fish embryos are transparent, large, hardy and easy to maintain in the laboratory. Adults show continuous production of eggs and juveniles reach sexual maturity a few weeks after hatching (an unusual condition in fishes). Their particular developmental features confer unique opportunities for research on cell behavior during early development, the effect of environmental factors on development, the regulation of diapauses and the mechanisms involved in sex determination, among others topics. Image provided by Nibia Berois, Universidad de la República, Montevideo, Uruguay. [source] Lack of glucose and hsp70 responses in haddock Melanogrammus aeglefinus (L.) subjected to handling and heat shockJOURNAL OF FISH BIOLOGY, Issue 1 2008L. O. B. Afonso Juvenile haddock Melanogrammus aeglefinus (c. 39 g) were exposed to either a handling stressor (1 min out of water) or heat shock (increase from 10 to 15° C for 1 h), and plasma cortisol, plasma glucose and gill hsp70 levels were determined before, and at 1, 3, 6, 12, 24 and 48 h post-stress. The pattern of cortisol increase was similar following both stressors, with levels increasing by 25-fold at 1 h post-stress, but returning to pre-stress levels (2,5 ng ml,1) by 3 h. In contrast, neither handling nor heat shock caused an increase in plasma glucose levels. Although gill hsp70 was detected, presumably constitutive levels, in both control and heat shocked groups, there were not significant changes in gill hsp70 levels after exposure to heat shock. The lack of glucose and hsp70 responses to these typical stressors is consistent with previous studies on Atlantic cod Gadus morhua, and suggests that the stress physiology of Gadidae differs from the ,typical' teleost. [source] Reproduction Phase-Related Expression of ,-Endorphin-Like Immunoreactivity in the Nucleus Lateralis Tuberis of the Female Indian Major Carp Cirrhinus mrigala: Correlation with the Luteinising Hormone Cells-Ovary AxisJOURNAL OF NEUROENDOCRINOLOGY, Issue 5 2006A. J. Sakharkar Abstract The present study aimed to determine whether ,-endorphin immunoreactivity (bEP-ir) in the neurones of the nucleus lateralis tuberis (NLT) is linked to the seasonal cycle and shows correlation with the number of luteinising hormone (LH) cells in the pituitary gland and ovaries in the teleost, Cirrhinus mrigala. Although LH cells were moderately immunostained during the resting phase (December to January), the morphological profile suggested increased synthetic and secretory activity during the preparatory (February to April) and prespawning (May to June) phases. However, LH immunoreactivity was greatly reduced (P < 0.001) in the spawning (July to August) phase, suggesting massive discharge of the hormone; this pool was partly replenished in the postspawning (September to November) phase. The ovaries grew rapidly in the preparatory and prespawning phases; maximal size was attained during spawning, when ovulation occurred. Thereafter, the ovaries regressed. The NLT of C. mrigala is divisible into the pars lateralis (NLTl) and medialis (NLTm). During the postspawning and resting phases, bEP-ir was readily detectable in the NLTm as well as NLTl neurones. However, a steady reduction in the immunoreactivity was observed in the NLTm neurones during the preparatory through spawning phases (P < 0.001), suggesting a negative correlation with the LH cells-ovary axis. Thus, the inhibitory influence of ,-endorphin on the gonadotrophin-releasing hormone (GnRH)-LH axis appears to be attenuated during the preparatory through spawning phases. This may be necessary for the rapid stimulation of the axis culminating in spawning. Neurones of the NLTl also showed a gradual reduction in bEP-ir during the preparatory and prespawning phases (P < 0.01) and may therefore play a similar role. However, significant augmentation of the immunoreactivity was noticed in these neurones during the spawning phase (P < 0.001), the physiological significance of which is unknown. Although the present study demonstrated a temporal correlation between the ,-endorphin in the NLT, LH cells and the ovary, we suggest that the peptide in the NLTl and NLTm may show functional duality during the spawning phase. [source] Pigmentary function and evolution of tyrp1 gene duplicates in fishPIGMENT CELL & MELANOMA RESEARCH, Issue 6 2009Ingo Braasch Summary The function of the tyrosinase-related protein 1 (Tyrp1) has not yet been investigated in vertebrates basal to tetrapods. Teleost fishes have two duplicates of the tyrp1 gene. Here, we show that the teleost tyrp1 duplicates have distributed the ancestral gene expression in the retinal pigment epithelium (RPE) and melanophores in a species-specific manner. In medaka embryos, tyrp1a expression is found in the RPE and in melanophores while tyrp1b is only expressed in melanophores. In zebrafish embryos, expression of tyrp1 paralogs overlaps in the RPE and in melanophores. Knockdown of each zebrafish tyrp1 duplicate alone does not show pigmentary defects, but simultaneous knockdown of both tyrp1 genes results in the formation of brown instead of black eumelanin accompanied by severe melanosome defects. Our study suggests that the brown melanosome color in Tyrp1-deficient vertebrates is an effect of altered eumelanin synthesis. Black eumelanin formation essentially relies on the presence of Tyrp1 and some of its function is most likely conserved from the common ancestor of bony vertebrates. [source] Conserved neurochemical pathways involved in hypothalamic control of energy homeostasisTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 3 2007Paul M. Forlano Abstract The melanocortin system, which includes ,-melanocyte-stimulating hormone (,-MSH) and its endogenous antagonist, agouti-related protein (AgRP), is fundamental for the central control of energy homeostasis in mammals. Recent studies have demonstrated that many neuropeptides involved in the control of ingestive behavior and energy expenditure, including melanocortins, are also expressed and functional in teleost fishes. To test the hypothesis that the underlying neural pathways involved in energy homeostasis are conserved throughout vertebrate evolution, the neuroanatomical distribution of ,-MSH in relation to AgRP was mapped in a teleost (zebrafish, Danio rerio) by double-label immunocytochemistry. Zebrafish ,-MSH- and AgRP-immunoreactive (ir) cells are found in discrete populations in the ventral periventricular hypothalamus, the proposed arcuate homologue in teleosts. Major ascending projections are similar for both peptides, and dense ir-fibers innervate preoptic and ventral telencephalic nuclei homologous to paraventricular, lateral septal, and amygdala nuclei in mammals. Furthermore, ,-MSH and AgRP-ir somata and fibers are pronounced at 5 days post fertilization when yolk reserves are depleted and larvae begin to feed actively, which supports the functional significance of these peptides for feeding behavior. The conservation of melanocortin peptide function and projection pathways further support zebrafish as an excellent genetic model system to investigate basic mechanisms involved in the central regulation of energy homeostasis. J. Comp. Neurol. 505:235,248, 2007. © 2007 Wiley-Liss, Inc. [source] Expression of a novel zebrafish zinc finger gene, gli2b, is affected in Hedgehog and Notch signaling related mutants during embryonic developmentDEVELOPMENTAL DYNAMICS, Issue 2 2005Zhiyuan Ke Abstract Gli zinc-finger proteins are known as downstream mediators of the evolutionary conserved Hedgehog pathway. In zebrafish, gli2 functions differently from Gli2 in mammals. This difference could be due to the gli2 duplication in teleosts evolution and partial redundancy between two duplicated genes. Here, we report a novel zebrafish gli2 -like cDNA. Its structure, genetic location, and distinct expression pattern in the central nervous system suggested that this gene might represent a second gli2 of teleosts, and we named it gli2b. gli2b was expressed in the neural keel, excluding the forebrain,midbrain boundary, while gli2 expression complemented this pattern. After 24 hours postfertilization, several specific domains of gli2b expression were observed in the lateral and medial hindbrain and hypothalamus. In mutants affecting the Hedgehog and Notch signaling pathways, gli2b expression was either disrupted or extended in different regions. Developmental Dynamics 232:479,486, 2005. © 2005 Wiley-Liss, Inc. [source] Genome duplication, subfunction partitioning, and lineage divergence: Sox9 in stickleback and zebrafishDEVELOPMENTAL DYNAMICS, Issue 3 2003William A. Cresko Abstract Teleosts are the most species-rich group of vertebrates, and a genome duplication (tetraploidization) event in ray-fin fish appears to have preceded this remarkable explosion of biodiversity. What is the relationship of the ray-fin genome duplication to the teleost radiation? Genome duplication may have facilitated lineage divergence by partitioning different ancestral gene subfunctions among co-orthologs of tetrapod genes in different teleost lineages. To test this hypothesis, we investigated gene expression patterns for Sox9 gene duplicates in stickleback and zebrafish, teleosts whose lineages diverged early in Euteleost evolution. Most expression domains appear to have been partitioned between Sox9a and Sox9b before the divergence of stickleback and zebrafish lineages, but some ancestral expression domains were distributed differentially in each lineage. We conclude that some gene subfunctions, as represented by lineage-specific expression domains, may have assorted differently in separate lineages and that these may have contributed to lineage diversification during teleost evolution. Developmental Dynamics, 2003. © 2003 Wiley-Liss, Inc. [source] Evidence for neural stem cells in the medaka optic tectum proliferation zones,DEVELOPMENTAL NEUROBIOLOGY, Issue 10 2010Alessandro Alunni Abstract Few adult neural stem cells have been characterized in vertebrates. Although teleosts continually generate new neurons in many regions of the brain after embryogenesis, only two types of neural stem cells (NSCs) have been reported in zebrafish: glial cells in the forebrain resembling mammalian NSCs, and neuroepithelial cells in the cerebellum. Here, following our previous studies on dividing progenitors (Nguyen et al. [1999]: J Comp Neurol 413:385,404.), we further evidenced NSCs in the optic tectum (OT) of juvenile and adult in the medaka, Oryzias latipes. To detect very slowly cycling progenitors, we did not use the commonly used BrdU/PCNA protocol, in which PCNA may not be present during a transiently quiescent state. Instead, we report the optimizations of several protocols involving long subsequent incubations with two thymidine analogs (IdU and CldU) interspaced with long chase times between incubations. These protocols allowed us to discriminate and localize fast and slow cycling cells in OT of juvenile and adult in the medaka. Furthermore, we showed that adult OT progenitors are not glia, as they express neither brain lipid-binding protein (BLBP) nor glial fibrillary acidic protein (GFAP). We also showed that expression of pluripotency-associated markers (Sox2, Musashi1 and Bmi1) colocalized with OT progenitors. Finally, we described the spatio-temporally ordered population of NSCs and progenitors in the medaka OT. Hence, the medaka appears as an invaluable model for studying neural progenitors that will open the way to further exciting comparative studies of neural stem cells in vertebrates. © 2010 Wiley Periodicals, Inc. Develop Neurobiol 70: 693,713, 2010 [source] Ontogeny of energy homeostatic pathways via neuroendocrine signaling in Atlantic salmonDEVELOPMENTAL NEUROBIOLOGY, Issue 9 2010Anne-Grethe Gamst Moen Abstract Leptin and ghrelin are known to regulate energy homeostasis via hypothalamic neuropeptide signaling in mammals. Recent studies have discovered that these hormones exist in teleosts, however, very little is known concerning their role during teleost ontogeny. Here, we have examined the steady state levels of leptins, ghrelins, their target neuropetides and several growth factors during Atlantic salmon development. Initial experiments revealed differential expression of leptin genes and ghrelin isoforms during embryogenesis. In larvae, equal upregulation of ghrl1 and ghrl2 was observed just prior to exogenous feeding while a surge of lepa1 occurred one week after first-feeding. Subsequent dissection of the embryos and larvae showed that lepa1, cart, pomca1, and agrp are supplied as maternal transcripts. The earliest zygotic expression was observed for lepa1 and cart at 320 day degrees. By 400 day degrees, this expression was localized to the head and coincided with upregulation of ghrl2 and npy. Over the hatching period growth factor signaling predominated. The ghrelin surge prior to first-feeding was exclusively localized in the internal organs and coincided with upregulation of npy and agrp in the head and agrp in the trunk. One week after exogenous feeding was established major peaks were detected in the head for lepa1 and pomca1 with increasing levels of cart, while lepa1 was also significantly expressed in the trunk. By integrating theses data into an ontogenetic model, we suggest that the mediation of Atlantic salmon energy homeostatic pathways via endocrine and neuropeptide signaling retains putative features of the mammalian system. © 2010 Wiley Periodicals, Inc. Develop Neurobiol 70: 649,658, 2010 [source] Identifying patterns of diversity of the actinopterygian fulcraACTA ZOOLOGICA, Issue 2009Gloria Arratia Abstract Fin rays, scutes or ridge scales, and fulcra have been traditionally interpreted as modified scales, but their diversity has been almost ignored. Based on results presented here, revised definitions of these elements are provided. At least two patterns of basal fulcra are found in actinopterygians: in Pattern I all or most basal fulcra are paired elements, whereas in Pattern II, a series of unpaired basal fulcra that are bifurcated proximally, and whose forking gradually becomes larger caudad, are followed by a series of paired elements. Basal fulcra are commonly present on unpaired fins of lower actinopterygians, including basal neopterygians. Among living fish they are absent in polypteriforms, Amia and teleosts. Fringing fulcra are always paired. Three patterns of fringing fulcra series are described: the series of fringing fulcra in basal actinopterygians is formed by expanded terminal segments of marginal lepidotrichia (Pattern A). Another series is formed by a combination of slightly expanded or modified terminal segments of rays and independent spiny, small elements (Pattern B). The third series is formed of small, spiny ossified elements positioned along the leading marginal fin ray(s) (Pattern C). Other patterns of basal and fringing fulcra remain to be investigated, along with their phylogenetic implications. [source] Acute CO2 tolerance during the early developmental stages of four marine teleostsENVIRONMENTAL TOXICOLOGY, Issue 6 2003T. Kikkawa Abstract Ocean sequestration of CO2 is proposed as a possible measure to mitigate climate changes caused by increasing atmospheric concentrations of the gas, but its impact on the marine ecosystem is unknown. We investigated the acute lethal effect of CO2 during the early developmental stages of four marine teleosts: red sea bream (Pagrus major), Japanese whiting (Sillago japonica), Japanese flounder (Paralichthys olivaceus), and eastern little tuna (Euthynnus affinis). The percentages of larvae that hatched and survived were not affected by exposure to water with a PCO2 of 1.0 kPa (= 7.5 mmHg) within 24 h. Median lethal PCO2 values for a 360-min exposure were 1.4 kPa (cleavage), 5.1 kPa (embryo), 7.3 kPa (preflexion), 4.2 kPa (flexion), 4.6 kPa (postflexion), and 2.5 kPa (juvenile) for red sea bream; 2.4 kPa (cleavage), 4.9 kPa (embryo), 5.9 kPa (preflexion), 6.1 kPa (flexion), 4.1 kPa (postflexion), and 2.7 kPa (juvenile) for Japanese whiting; 2.8 kPa (cleavage) and > 7.0 kPa (young) for Japanese flounder; and 11.8 kPa (cleavage) for eastern little tuna. Red sea bream and Japanese whiting of all ontogenetic stages had similar susceptibilities to CO2: the most susceptible stages were cleavage and juvenile, whereas the most tolerant stages were preflexion and flexion. © 2003 Wiley Periodicals, Inc. Environ Toxicol 18: 375,382, 2003 [source] An evolutionary view on tooth development and replacement in wild Atlantic salmon (Salmo salar L.)EVOLUTION AND DEVELOPMENT, Issue 1 2008A. Huysseune SUMMARY To gain an insight into the evolution of tooth replacement mechanisms, we studied the development of first-generation and replacement teeth on the dentary of wild Atlantic salmon (Salmo salar L.), a protacanthopterygian teleost, using serially sectioned heads of early posthatching stages as well as adults. First-generation teeth develop within the oral epithelium. The anlage of the replacement tooth is first seen as a placode-like thickening of the outer dental epithelium of the predecessor, at its lingual and caudal side. Ongoing development of the replacement tooth germ is characterized by the elaboration of a population of epithelial cells, termed here the middle dental epithelium, apposed to the inner dental epithelium on the lingual side of the tooth germ. Before the formation of the new successor, a single-layered outer dental epithelium segregates from the middle dental epithelium. The dental organs of the predecessor and the successor remain broadly interconnected. The absence of a discrete successional dental lamina in salmon stands in sharp contrast to what is observed in other teleosts, even those that share with salmon the extraosseous formation of replacement teeth. The mode of tooth replacement in Atlantic salmon displays several characters similar to those observed in the shark Squalus acanthias. To interpret similarities in tooth replacement between Atlantic salmon and chondrichthyans as a case of convergence, or to see them as a result of a heterochronic shift, requires knowledge on the replacement process in more basal actinopterygian lineages. The possibility that the middle dental epithelium functionally substitutes for a successional lamina, and could be a source of stem cells, whose descendants subsequently contribute to the placode of the new replacement tooth, needs to be explored. [source] Identification and characterization of the transcription factors involved in T-cell development, t-bet, stat6 and foxp3, within the zebrafish, Danio rerioFEBS JOURNAL, Issue 1 2010Suman Mitra The discovery of cytokines expressed by T-helper 1 (Th1), Th2, Th17 and T-regulatory (Treg) cells has prompted speculation that these types of responses may exist in fish, arising early in vertebrate evolution. In this investigation, we cloned three zebrafish transcription factors, T-box expressed in T cells (t-bet), signal transducer and activator of transcription 6 (stat6) and fork-head box p3 (foxp3), in which two transcripts are present, that are important in the development of a number of these cell types. They were found within the zebrafish genome, using a synteny approach in the case of t-bet and foxp3. Multiple alignments of zebrafish t-bet, stat6 and foxp3 amino acids with known vertebrate homologues revealed regions of high conservation, subsequently identified to be protein domains important in the functioning of these transcription factors. The gene organizations of zebrafish t-bet and foxp3 were identical to those of the human genes, with the second foxp3 transcript lacking exons 5, 6, 7 and 8. Zebrafish stat6 (21 exons and 20 introns) was slightly different from the human gene, which contained 22 exons and 21 introns. Immunostimulation of zebrafish head kidney and spleen cells with phytohaemagglutinin, lipopolysaccharide or Poly I:C, showed a correlation between the expression of t-bet, stat6 and foxp3 with other genes involved in Th and Treg responses using quantitative PCR. These transcription factors, together with many of the cytokines that are expressed by different T-cell subtypes, will aid future investigations into the Th and Treg cell types that exist in teleosts. [source] The ancestral complement system in sea urchinsIMMUNOLOGICAL REVIEWS, Issue 1 2001L. Courtney Smith Summary: The origin of adaptive immunity in the vertebrates can be traced to the appearance of the ancestral RAG genes in the ancestral jawed vertebrate; however, the innate immune system is more ancient. A central subsystem within innate immunity is the complement system, which has been identified throughout and seems to be restricted to the deuterostomes. The evolutionary history of complement can be traced from the sea urchins (members of the echinoderm phylum), which have a simplified system homologous to the alternative pathway, through the agnathans (hagfish and lamprey) and the elasmobranchs (sharks and rays) to the teleosts (bony fish) and tetrapods, with increases in the numbers of complement components and duplications in complement pathways. Increasing complexity in the complement system parallels increasing complexity in the deuterostome animals. This review focuses on the simplest of the complement systems that is present in the sea urchin. Two components have been identified that show significant homology to vertebrate C3 and factor B (Bf), called SpC3 and SpBf, respectively. Sequence analysis from both molecules reveals their ancestral characteristics. Immune challenge of sea urchins indicates that SpC3 is inducible and is present in coelomic fluid (the body fluids) in relatively high concentrations, while SpBf expression is constitutive and is present in much lower concentrations. Opsonization of foreign cells and particles followed by augmented uptake by phagocytic coelomocytes appears to be a central function for this simpler complement system and important for host defense in the sea urchin. These activities are similar to some of the functions of the homologous proteins in the vertebrate complement system. The selective advantage for the ancestral deuterostome may have been the amplification feedback loop that is still of central importance in the alternative pathway of complement in higher vertebrates. Feedback loop functions would quickly coat pathogens with complement leading to phagocytosis and removal of foreign cells, a system that would be significantly more effective than an opsonin that binds upon contact as a result of simple diffusion. An understanding of the immune response of the sea urchin, an animal that is a good estimator of what the ancestral deuterostome immune system was like, will aid us in understanding how adaptive immunity might have been selected for during the early evolution of the vertebrates and how it might have been integrated into the pre-existing innate immune system that was already in place in those animals. The authors are grateful to Drs Sham Nair and Paul Gross for their critique of the manuscript and helpful suggestions. This work was supported by the National Science Foundation (MCB 9603086). [source] Phylogeny of nucleus medianus of the posterior tubercle in rayfinned fishesINTEGRATIVE ZOOLOGY (ELECTRONIC), Issue 1 2009R. Glenn NORTHCUTT Abstract The brains of ray-finned fishes form a morphocline of increasing complexity, from cladistians through teleosts. This is particularly apparent in the posterior tubercle of the diencephalon. In cladistians, the posterior tubercle consists of a periventricular nucleus and a migrated nucleus medianus that is fused across the midline. In more advanced ray-finned fishes, such as gars and bowfins, the posterior tubercle comprises numerous additional migrated nuclei, termed the preglomerular complex, in addition to a more well developed nucleus medianus. In teleosts, the most derived ray-finned fishes, there is an even more elaborate preglomerular complex, but there is no recognizable nucleus medianus. In an attempt to explain the variation in the posterior tubercle of the diencephalon in ray-finned fishes, the immunohistochemistry and connections of nucleus medianus were examined in cladistians, gars and bowfins. In each of these taxa, nucleus medianus exhibits large numbers of calretinin-positive neurons and has ascending projections that terminate in several divisions of the pallium. Although teleosts, such as goldfish, also exhibit numerous cell groups in the posterior tubercle that are rich in calretinin, none of these cell groups has connections that are comparable to those of nucleus medianus in non-teleost ray-finned fishes. It is possible, therefore, that nucleus medianus was lost with the origin of teleosts. [source] Morphological and biochemical analyses of otoliths of the ice-fish Chionodraco hamatus confirm a common origin with red-blooded speciesJOURNAL OF ANATOMY, Issue 1 2009Chiara Maria Motta Abstract The morphology and composition of the three otoliths of the Antarctic ice-fish Chionodraco hamatus were studied by scanning electron microscopy and X-ray diffraction. The composition of the sagitta, lapillus and asteriscus protein matrices was also analysed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis, western blots and confocal laser scanning microscopy to reveal the presence of and to localize the calcium-binding proteins calmodulin, calbindin and S-100. Morphological results indicated that the otoliths in this ice-fish were similar to those of Trematomus bernacchii, a red-blooded Antarctic species [B. Avallone et al. (2003) J. Submicrosc. Cytol. Pathol. 35, 69,76], but rather different from those of other teleosts. These two Antarctic species possessed a completely vateritic asteriscus, whereas their sagitta and lapillus were made mostly of aragonite. Parallel analysis of protein patterns in C. hamatus and T. bernacchii revealed that the sagitta significantly differed from the lapillus and asteriscus in both species. The sagitta did not contain the S-100 protein and showed calmodulin and calbindin located in discontinuous or incremental zones, respectively. These results demonstrate that the otoliths of C. hamatus and T. bernacchii share more resemblances than differences and support the idea of a common origin of these species. [source] Diet composition of Belone belone (Linnaeus, 1761) (Pisces: Belonidae) in the Aegean SeaJOURNAL OF APPLIED ICHTHYOLOGY, Issue 6 2009T. M. Sever Summary The objective of this study was to determine the monthly dietary pattern in migratory garfish and to improve our understanding in the seasonality of prey choice. Gut contents of 597 Belone belone specimens collected from the eastern Aegean Sea (Turkey) were analyzed: 79.2% contained food in their guts and 20.8% had empty guts. Crustaceans (36.7%) were the most important prey with a 36.7 index of relative importance (%IRI). Especially brachyurans (13.0%) and copepods played a major role (10.1%), followed by teleosts (26.1%) and other food categories (23.3%) (much of which was of terrestrial origin, including insects). Nannocalanus minor, Clausocalanus arcuicornis, Temora stylifera, Labidocera wollastoni and Oncea media were important copepods found in the guts of B. belone specimens. Analysis of variance of the monthly weight data indicated no significant seasonal differences, except for January and February. [source] Gonadogenesis in early developmental stages of Acipenser naccarii and influence of estrogen immersion on feminizationJOURNAL OF APPLIED ICHTHYOLOGY, Issue 1 2007G. Grandi Summary Gonad development processes and the effects of a single 8-hour immersion treatment with 17, -estradiol (E2, 400 ,g L,1) on sex differentation in the Adriatic sturgeon, Acipenser naccarii, were investigated. After migration of germ cells, gonadal ridges appeared in 16- to 18-day old larvae and undifferentiated gonads in 55- to 60-day old larvae. Putative ovaries with notches in the germinal epithelium and presumed testes with smooth germinal epithelium appeared in 180,185-day old juveniles. Ovaries with proliferating oogonia and early meiotic oocytes clusters were observed in 292-day old juveniles. Testes did not exhibit germ cell mitosis until 430 days of age. Developmental stages in E2 -treated animals closely followed those of controls up to 430 days. The treatment significantly increased the percentage of ovaries when administered to embryos about 1.5 day before hatching, while did not significantly altered the normal 1/1 sex ratio when administered to 1.5-day old pre-larvae and 10-day old larvae. It is likely that in A. naccarii exogenous E2 administration may act through a feedback mechanism of self-supporting steroid production and that steroids are the physiological inducers of sex differentiation, as in most teleosts. The E2 -immersion treatment, easier than time-consuming administration through food, could be a good approach to control sex differentiation and caviar production. [source] Structure and evolution of the horizontal septum in vertebratesJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 5 2003S. Gemballa Abstract Although the horizontal septum (HS) has been identified as playing a role in fish biomechanics and in path finding of cells during zebrafish development, its morphology is poorly known. However, it is generally regarded as an evolutionarily conserved structure. To test this idea, we applied a novel combination of techniques to analyse the HS of 35 species from all major gnathostome clades in which is visualized its collagen fibre architecture. Results show that the HS is a conserved trait only with respect to the presence of caudolateral [= epicentral] and craniolateral [= posterior oblique] collagen fibre tracts, but differs remarkably with respect to the specifications of these tracts. Our data revealed several evolutionary changes within vertebrates. In the gnathostome ancestor, the two tracts are represented by evenly distributed epicentral fibres (ECFs) and posterior oblique fibres (POFs). ECFs are condensed to distinct epicentral tendons (ECTs) in the actinopteran ancestor. POFs independently evolved to distinct posterior oblique tendons (POTs) at least two times within teleosts. Within basal teleostomes, POFs as well as ECFs or ECTs were lost two times independently. POTs were lost at least three times independently within teleosts. This view of a homoplastic HS remains stable regardless of the competing phylogenies used for analysis. Our data make problematic any generalization of biomechanical models on fish swimming that include the HS. They indicate that the pathfinding role of the HS in zebrafish may be extended to gnathostome fishes, but not to agnathans, sarcopterygian fishes and tetrapods. [source] A major fish stranding caused by a natural hypoxic event in a shallow bay of the eastern South Pacific OceanJOURNAL OF FISH BIOLOGY, Issue 7 2010E. Hernández-Miranda A massive beaching and mortality of fishes occurred in Coliumo Bay, a shallow bay located along the coast of the eastern South Pacific Ocean on 3 January 2008. This stranding was a consequence of an abrupt decrease in the dissolved oxygen concentration throughout the whole water column, due to the effect of intense upwelling along the coast off central-southern Chile. The main objectives of this study were: (1) to characterize taxonomically and biologically the fish species assemblage present in this beaching; (2) to evaluate several physiological indicators for the condition of the beached species at the time of their death; and (3) to assess the possible cause,effect mechanisms involved in the fishes death and the changes that took place in the fish community throughout the time. In this beaching, 26 fish species were identified: 23 teleosts, one myxiniform and two elasmobranchs. Most beached specimens were juveniles. Haematological and histological evidence indicate that severe hypoxia that lasted for at least 48 h was the most plausible cause of death. The main conclusion of this study is that the presence of oxygen-poor equatorial sub-surface water in the shallow coastal zone due to intense regional-scale upwelling caused the fish stranding. Although the effect of the hypoxic event was severe for the fish assemblage of Coliumo Bay, the rapid recuperation observed suggests that hypoxic events at the local spatial scale can be buffered by migration processes from the fish community inhabiting close by areas non-affected by low oxygen conditions. The effect that severe hypoxic events may have on larger spatial scales remains unknown. [source] Influence of selected factors on the dietary compositions of three targeted and co-occurring temperate species of reef fishes: implications for food partitioningJOURNAL OF FISH BIOLOGY, Issue 6 2010M. E. Platell The dietary compositions of three medium to large targeted fish species, which co-occur over reefs in temperate waters of south-western Australia, were determined. These data were then used to ascertain statistically the extent to which body size, season and habitat influence the diets of these species and the degree to which food resources were partitioned among and within those species, and thus reduced the potential of interspecific and intraspecific competition. On the west coast, Bodianus frenchii (Labridae) and Epinephelides armatus (Serranidae) spent their whole life over prominent limestone reefs, as did Glaucosoma hebraicum (Glaucosomatidae) in all but juvenile life, when it lived over low-relief, limestone substrata. The dietary composition of each species changed with increasing body size, which, in G. hebraicum, was particularly pronounced at c. 300 mm total length (LT) and therefore at the size when this species shifts habitat. When the three species co-occurred over the same reefs, their dietary compositions were significantly different, with that of B. frenchii being by far the most discrete, reflecting a far greater contribution by sedentary taxa. Thus, the diet of B. frenchii was distinguished from those of the other two species in containing substantial volumes of bivalve and gastropod molluscs and echinoid echinoderms and essentially no teleosts. Although the diets of G. hebraicum and particularly E. armatus were dominated by teleosts, and especially for larger individuals, the former species ingested greater volumes of cephalopods and small crustaceans. The pointed jaws of B. frenchii, with their forwardly directed and interlocking anterior incisors, are ideally adapted for biting and retaining their invertebrate prey, which are attached to or reside within reef crevices. In contrast, the mouths of G. hebraicum and E. armatus are broader and rounder and contain numerous small, slender and inward-pointing teeth. These teeth, in conjunction with prominent backward-curved canines in E. armatus, facilitate the capture and retention of fish prey. Observations in situ indicate that G. hebraicum is a suction feeder, while E. armatus is predominantly a ram feeder. Although reef environments on the west and south coasts differ, the diet of B. frenchii on these coasts differed only slightly. Interspecific differences in diet, combined with size-related changes in dietary compositions and the occupation of different habitats by juvenile and adult G. hebraicum, reduce the potential for competition for food resources among and within B. frenchii, G. hebraicum and E. armatus and thus helps facilitate the coexistence of these species which historically have been abundant over reefs in south-western Australia. [source] Early development of the digestive tract (pharynx and gut) in the embryos and pre-larvae of the European sea bass Dicentrarchus labraxJOURNAL OF FISH BIOLOGY, Issue 6 2009E. Sucré The European sea bass Dicentrarchus labrax is a marine teleost important in Mediterranean aquaculture. The development of the entire digestive tract of D. labrax, including the pharynx, was investigated from early embryonic development to day 5 post hatching (dph), when the mouth opens. The digestive tract is initialized at stage 12 somites independently from two distinct infoldings of the endodermal sheet. In the pharyngeal region, the anterior infolding forms the pharynx and the first gill slits at stage 25 somites. The other three gill arches and slits are formed between 1 and 5 dph. Posteriorly, in the gut tube region, a posterior infolding forms the foregut, midgut and hindgut. The anus opens before hatching, at stage 28 somites. Associated organs (liver, pancreas and gall bladder) are all discernable from 3 dph. Some aspects of the development of the two independent initial infoldings seem original compared with data in the literature. These results are discussed and compared with embryonic and post-embryonic development patterns in other teleosts. [source] Ecological speciation in marine v. freshwater fishesJOURNAL OF FISH BIOLOGY, Issue 5 2009O. Puebla Absolute barriers to dispersal are not common in marine systems, and the prevalence of planktonic larvae in marine taxa provides potential for gene flow across large geographic distances. These observations raise the fundamental question in marine evolutionary biology as to whether geographic and oceanographic barriers alone can account for the high levels of species diversity observed in marine environments such as coral reefs, or whether marine speciation also operates in the presence of gene flow between diverging populations. In this respect, the ecological hypothesis of speciation, in which reproductive isolation results from divergent or disruptive natural selection, is of particular interest because it may operate in the presence of gene flow. Although important insights into the process of ecological speciation in aquatic environments have been provided by the study of freshwater fishes, comparatively little is known about the possibility of ecological speciation in marine teleosts. In this study, the evidence consistent with different aspects of the ecological hypothesis of speciation is evaluated in marine fishes. Molecular approaches have played a critical role in the development of speciation hypotheses in marine fishes, with a role of ecology suggested by the occurrence of sister clades separated by ecological factors, rapid cladogenesis or the persistence of genetically and ecologically differentiated species in the presence of gene flow. Yet, ecological speciation research in marine fishes is still largely at an exploratory stage. Cases where the major ingredients of ecological speciation, namely a source of natural divergent or disruptive selection, a mechanism of reproductive isolation and a link between the two have been explicitly documented are few. Even in these cases, specific predictions of the ecological hypothesis of speciation remain largely untested. Recent developments in the study of freshwater fishes illustrate the potential for molecular approaches to address specific questions related to the ecological hypothesis of speciation such as the nature of the genes underlying key ecological traits, the magnitude of their effect on phenotype and the mechanisms underlying their differential expression in different ecological contexts. The potential provided by molecular studies is fully realized when they are complemented with alternative (e.g. ecological, theoretical) approaches. 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