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PubMed2004

Subfunction partitioning, the teleost radiation and the annotation of the human genome.

Half of all vertebrate species are teleost fish. What accounts for this explosion of biodiversity? Recent evidence and advances in evolutionary theory suggest that genomic features could have played a significant role in the teleost radiation. This review examines evidence for an ancient whole-genome duplication (tetraploidization) event that probably occurred just before the teleost radiation. The partitioning of ancestral subfunctions between gene copies arising from this duplication could have contributed to the genetic isolation of populations, to lineage-specific diversification of developmental programs, and ultimately to phenotypic variation among teleost fish. Beyond its importance for understanding mechanisms that generate biodiversity, the partitioning of subfunctions between teleost co-orthologs of human genes can facilitate the identification of tissue-specific conserved noncoding regions and can simplify the analysis of ancestral gene functions obscured by pleiotropy or haploinsufficiency. Applying these principles on a genomic scale can accelerate the functional annotation of the human genome and understanding of the roles of human genes in health and disease.

Animals↗
PubMed2003

Evaluating the radiation of the POMC gene in teleosts: characterization of American eel POMC.

A distinctive feature of the pituitary hormone precursor, proopiomelanocortin (POMC), is the presence of multiple melanocortin core sequences (HFRW), and one copy of the opioid, beta-endorphin. In the older lineages of ray-finned fish (i.e., orders Acipenseriformes and Semionotiformes), certain extant lobe-finned fish (Australian lungfish and African lungfish), and the tetrapods there are three melanocortin regions in POMC: ACTH/alphaMSH, beta-MSH, and gamma-MSH. However, among the teleosts, the most recent radiation of the ray-finned fishes, the gamma-MSH sequence is absent from the POMC genes of euteleosts like the carp, tilapia, chum salmon, sockeye salmon, and rainbow trout. The objective of this study was to determine whether the gamma-MSH sequence still may be present in the POMC gene of a more basal lineage of the teleosts such as a representative from subdivision Elopomorpha. To this end, a POMC cDNA was cloned and sequenced from the pituitary of the American eel, Anguilla rostrata (order Anguilliformes, family Anguillidae). The open reading frame of the eel POMC cDNA was 648 nucleotides in length and encoded 216 amino acids. As predicted, eel POMC contained the deduced amino acid sequences for beta-endorphin, ACTH/alpha-MSH, and beta-MSH. These end-products displayed primary sequence features that are common to ray-finned fish. Eel POMC lacks a gamma-MSH sequence and a large portion of the joining peptide region. In this regard, the eel POMC gene thus displays features very similar to the POMC genes that have been sequenced from euteleosts. Although it is conceivable that the gamma-MSH sequence may be present in representatives from the other basal extant lineages of teleosts (i.e., subdivisions Osteoglossomorpha or Clupeomorpha), it is also possible that the deletion that resulted in the loss of the gamma-MSH sequence occurred in the ancestral neopterygian that gave rise to the teleosts. In this case, the gamma-MSH sequence should be absent in all extant teleosts.

Amino Acid Sequence↗
PubMed2000

Bioaccumulation and distribution of silver in four marine teleosts and two marine elasmobranchs: influence of exposure duration, concentration, and salinity.

The bioaccumulation of waterborne silver (added as AgNO(3)) was compared amongst drinking (teleosts: rainbow trout, tidepool sculpin, plainfin midshipmen, and English sole) and non-drinking marine fish (elasmobranchs: Pacific spiny dogfish and long nose skate) exposed to 14.5 µg/l Ag for 21 days in 30-ppt seawater. In addition, 21-day exposures were performed on trout, midshipmen, and sculpin at 0 (control), 1.5, 14.5, and 50 µg/l Ag to evaluate the effect of silver concentration, and on sculpins acclimated to 18 and 30 ppt salinity and sampled periodically up to 21 days to evaluate the effects of salinity and exposure duration. A 48-h acute exposure (250 µg/l Ag) was also carried out on sculpins at 10, 18, 24, and 30 ppt. The 1.5-and 14.5-µg/l Ag levels are of regulatory importance, but are several orders of magnitude higher than normal environmental levels. Silver uptake occurred in all exposures, but internal accumulations were less than proportional to exposure concentration (1.5-50.0 µg/l Ag), and tended to saturate over time, suggesting that physiological regulation occurred. Control (non-exposed) fish exhibited measurable levels of silver in all tissues (10-200 µg Ag/kg wet weight), suggesting that they accumulate silver from the natural environment throughout their lifetimes. After 21-day exposure to 14.5 µg/l Ag, silver levels increased 2-20-fold in most tissues of all species, with the greatest concentrations occurring in the livers of teleosts (order: liver>gills>/=intestines>white muscle) and the gills of elasmobranchs (order: gills>liver>white muscle>intestines). Rainbow trout accumulated more silver than the other teleosts, and were the only species to suffer significant mortality, effects likely associated with added salinity stress. Accumulations were fairly uniform amongst the other teleosts. Similar concentrations in gills and intestines suggested that both branchial and intestinal uptake occurred, with the latter potentially dominant; indeed sole exhibited no silver build-up in the gills. The two elasmobranchs exhibited no silver build-up in intestines but much higher levels in gills, indicating that in the absence of drinking, only branchial uptake occurs. Nevertheless, based on whole liver content, the elasmobranchs accumulated silver 5-15-fold faster than the three teleosts. Over 21-day exposures (1.5-50.0 µg/l Ag) in sculpin, salinity markedly affected silver accumulation, with tissue-specific levels approximately 6-fold higher at 18, than at 30 ppt. However, there was negligible effect of salinity on silver accumulation during 48 h at 250 µg/l Ag. Silver bioaccumulation appears to be markedly affected by speciation. At lower salinities, or higher [Ag], a neutral charged AgCl(aq) complex exists in the water, allowing for increased bioaccumulation to occur. At higher salinity, only less bioavailable, negatively-charged AgCl(n)(1-n) complexes are present (AgCl(2)(-), AgCl(3)(2-), AgCl(4)(3-)).

Journal Article↗
PubMed2002

Stanniocalcin from an ancient teleost: a monomeric form of the hormone and a possible extracorpuscular distribution.

Stanniocalcin (STC) is a homodimeric glycoprotein hormone implicated in calcium and phosphate regulation in both teleost fish and mammals. In the present study, immunostaining with salmon STC antiserum demonstrated that STC cells were localized in both the corpuscles of Stannius (CS) and in specific cells of the distal renal tubules of the silver arawana, Osteoglossum bicirrhosum, an ancient ray-finned fish (actinoptergian) and basal teleost (Order Osteoglossiforme). The morphology of these STC-immunoreactive kidney cells was similar to renal 'chloride' (mitochondrial-rich) cells. The immunoreactive renal cells were present in two of three other osteoglossiformes and absent in the gar, a nonteleost actinopterygian and the eel, another basal teleost. The arawana STC cDNA encodes a prehormone of 249 amino acids (aa) with a signal peptide of 31 aa and a mature protein of 218 aa. The deduced aa sequence of arawana STC shows 54-66% identity with other teleost STCs and 51-52% identity with mammalian STC-1. The deduced aa sequence of arawana STC contains ten cysteines, compared with 11 in teleost STC and in mammalian STC-1. The cysteine substitution occurs at the site of inter-monomeric disulfide linkage. Western blot analysis revealed a single 21 kDa band under non-reducing conditions, and a single band of 25 kDa under reducing conditions. These data indicate that arawana STC exists as a monomeric peptide. Northern blot analysis detected a 3.3 kb STC mRNA confined to the CS, with no hybridization signal in either the remaining kidney or in gut, muscle, brain and heart. The significance of the STC signal in cells of the renal tubules of arawana and two other Osteoglossiforme species requires further investigation. This is the first report of a monomeric form of STC in any vertebrate and the first evidence of STC in renal tubules of adult fish.

Amino Acid Sequence↗
PubMed1998

Evidence for multiple protein kinase C isoforms in the leukocytes of a marine teleost, Sciaenops ocellatus.

The protein kinase C (PKC) family of isozymes mediates a diverse range of cellular functions, including activation of vertebrate lymphocytes through membrane-bound antigen receptors. The complex role of PKC in mammalian cells may be orchestrated in part by the presence of multiple isoforms, each of which displays a distinctive tissue distribution, substrate specificity and pattern of regulation. In the present study, PKC isoforms were identified in peripheral blood leukocytes of the marine teleost fish Sciaenops ocellatus by immunoprecipitation and Western blot using antibodies to mammalian isoforms. Functional activity was monitored by evaluating translocation of the teleost isoforms from membrane to cytosol in response to phorbol ester treatment. Teleost conventional isoforms PKC alpha and PKC beta (82 kDa) completely translocated out of the cytosol in response to phorbol ester. Phorbol ester did not induce translocation of teleost atypical isoform PKC zeta (67 kDa), as has been shown for its mammalian homologue. Although their identity as distinct isoforms is less clear, proposed teleost novel PKC delta (84, 86 kDa) and PKC eta (83, 85 kDa) also translocated out of the cytosol. The presence of multiple isoforms representing each of the three major classes of PKC in red drum leukocytes implies that the complexity of signal transduction pathways in vertebrates is highly conserved.

Animals↗
PubMed2002

Immunological detection of Na(+)/H(+) exchangers in the gills of a hagfish, Myxine glutinosa, an elasmobranch, Raja erinacea, and a teleost, Fundulus heteroclitus.

Na(+)/H(+) exchangers (NHE) are a family of ion exchangers with diverse functions that are well defined in mammals. NHE-1 is expressed in the plasma membrane of most mammalian cells where it regulates intracellular pH, and usually in the basolateral membrane of epithelial cells. It has also been detected in teleost gills where it may participate in systemic pH regulation. NHE-3 is usually expressed in the apical membrane of mammalian epithelial cells where it helps reabsorb Na(+) and HCO(3)(-); it has also been detected in teleost gills. We used Western blotting and heterologous antibodies to screen for expression of NHE-1 and NHE-3 in gills of an agnathan (Myxine glutinosa) and an elasmobranch (Raja erinacea), and NHE-3 in gills of a teleost (Fundulus heteroclitus). Positive NHE-1 bands were detected in gills from the agnathan and elasmobranch. Using the NHE-3 antibody, bands were detected in the gills of the elasmobranch and teleost. These data are some of the first direct evidence of NHEs in the gills of an agnathan and elasmobranch, and confirm the presence of NHEs in the gills of teleosts.

Animals↗
PubMed2002

Social modulation of androgen levels in male teleost fish.

Androgens are classically thought of as the sex steroids controlling male reproduction. However, in recent years evidence has accumulated showing that androgens can also be affected by the interactions between conspecifics, suggesting reciprocal interactions between androgens and behaviour. These results have been interpreted as an adaptation for individuals to adjust their agonistic motivation and to cope with changes in their social environment. Thus, male-male interactions would stimulate the production of androgens, and the levels of androgens would be a function of the stability of its social environment ['challenge hypothesis', Gen. Comp. Endocrinol. 56 (1984) 417]. Here the available data on social modulation of androgen levels in male teleosts are reviewed and some predictions of the challenge hypothesis are addressed using teleosts as a study model. We investigate the causal link between social status, territoriality and elevated androgen levels and the available evidence suggests that the social environment indeed modulates the endocrine axis of teleosts. The association between higher androgen levels and social rank emerges mainly in periods of social instability. As reported in the avian literature, in teleosts the trade-off between androgens and parental care is indicated by the fact that during the parental phase breeding males decreased their androgen levels. A comparison of androgen responsiveness between teleost species with different mating and parenting systems also reveals that parenting explains the variation observed in androgen responsiveness to a higher degree than the mating strategy. Finally, the adaptive value of social modulation of androgens and some of its evolutionary consequences are discussed.

Androgens↗
PubMed2000

Low mass-specific brain Na+/K+-ATPase activity in elasmobranch compared to teleost fishes: implications for the large brain size of elasmobranchs.

Elasmobranch fishes have long been noted for having unusually large brains for ectotherms, and therefore may be exceptions to the rule that vertebrates in general devote less than 8% of their resting metabolic rate to the central nervous system. The brain mass of sharks, skates and rays is often several times larger than that of teleost fishes of the same size. Still, the underlying reasons for this have remained unclear. Ion pumping by the Na+/K+-ATPase is the single most energy consuming process in the brain. In this study, Na+/K+-ATPase activity was measured in the brain of four species of elasmobranchs and 11 species of teleosts. While the average brain mass of the elasmobranchs examined was approximately three times that of the teleosts, the mean specific Na+/K+-ATPase activity was only about one-third of that of the teleosts. Thus, the total brain Na+/K+-ATPase activity was similar in elasmobranchs and teleosts. This suggests that the large brain size of elasmobranchs is at least partly related to a low mass-specific rate of brain energy use.

Animals↗
PubMedDate not supplied

Conservation and divergence of Bmp2a, Bmp2b, and Bmp4 expression patterns within and between dentitions of teleost fishes.

The diversity of tooth location in teleost fishes provides an excellent system for comparing genetic divergence between teeth in different species (phylogenetic homologs) with divergence between teeth within one species (iterative homologs). We have chosen to examine the expression of three members of the bone morphogenetic protein (Bmp) family because they are known to play multiple roles in tooth development and evolution in tetrapod vertebrates. We characterized expression of Bmp2a, Bmp2b, and Bmp4 during the development of oral and pharyngeal dentitions in three species of teleost fishes, the zebrafish (Danio rerio), Mexican tetra (Astyanax mexicanus), and Japanese medaka (Oryzias latipes). We found that expression in teleosts is generally highly conserved, with minor differences found among both iteratively homologous and phylogenetically homologous teeth. Expression of orthologous genes differs in several ways between the teeth of teleost fishes and those of the mouse, but between these vertebrate groups the summed expression pattern of Bmp genes is highly conserved. Significantly, the toothless oral region of the zebrafish lacks Bmp expression domains found in teleosts with oral teeth, implicating these genes in evolutionary tooth loss. We conclude that Bmp expression has been largely conserved in vertebrate tooth development over evolutionary time, and that loss of Bmp expression is correlated with region-specific loss of the dentition in a major group of fishes.

Animals↗
PubMed1998

Functional and molecular characterization of teleost leukocytes.

The coupling of immunologically relevant in vitro assay systems, cell separation techniques, and the development of distinct clonal leukocyte lines has established the existence of T, B, natural killer, and accessory cell equivalents in teleosts. B cells are directly defined by monoclonal antibodies to teleost immunoglobulin (Ig) and identification of Ig H and L chain genes. As in mammals, fish B cells show Ig H-chain gene rearrangements, allelic exclusion, produce both membrane-bound and secreted forms of Ig, and transduce intracellular proliferative signals upon anti-Ig cross-linking. It has also been found that some fish B cells express a unique chimeric Ig chain with sequence homology to mammalian Ig delta. Teleost T cells are still indirectly defined as sIg- lymphocytes due to a lack of definitive surface markers. These mIg- lymphocytes are the responding cells in mixed leukocyte cultures, proliferate specifically to autologously processed and presented antigen, provide helper function for in vitro antibody responses, and produce interleukin-like factors upon activation. Recent identification of teleost T-cell receptor alpha and beta genes has now permitted the unequivocal genetic demonstration that some of these mIg- cells are bona fide T cells. It is anticipated that such long-term clonal cell lines will be indispensable tools for dissecting the physiology, biochemistry and molecular biology of teleost immune responses.

Animals↗
PubMed2000

Proliferation zones in the adult brain of a sequential hermaphrodite teleost species (Sparus aurata).

Teleost sex change is an important model to understand general principles of sexual differentiation and plasticity in the adult brain. The present study is the first to examine the proliferation zones in the adult brain of males, females and sex-changing individuals of a protandrous teleost species (Sparus aurata), by means of 5-bromo-2-deoxyuridine immunocytochemistry. Postnatal neurogenesis in the marine teleost brain was found in ventricular and subventricular areas of the brain that in most cases coincided with the embryonic proliferation zones. The molecular layer of corpus and valvula cerebelli exhibited the highest mitotic activity in the adult brain. High mitotic activity was observed in the hypothalamic, thalamic and telencephalic ventricular areas, as well as the dorsal and ventral rim of the optic tectum. Most of the labeled cells were elongated, indicating the initiation of migratory activity. There were no qualitative differences in the distribution of proliferation zones between the sex phases studied with the exception of the ventricular region of the dorsal hypothalamic area. Volume fraction analysis of the area occupied by the labeled cells suggested that this region included higher densities of newborn cells in the female animals. The proliferation pattern in the adult gilthead sea bream brain is in agreement with the hypothesis of the continuous generation of new cells in the teleost brain. Moreover, our data propose that cell proliferation differences possibly existing in the ventricular region of the dorsal hypothalamus between sexual phases, might be involved in central mechanisms of sexual plasticity in protandrous hermaphrodite teleosts.

Animals↗
PubMed2007

Developmental origin of diencephalic sensory relay nuclei in teleosts.

We propose here a novel interpretation of the embryonic origin of cells of diencephalic sensory relay nuclei in teleosts based on our recent studies of gene expression patterns in the medaka (Oryzias latipes) embryonic brain and comparative hodological studies. It has been proposed that the diencephalic sensory relay system in teleosts is unique among vertebrates. Teleost relay nuclei, the preglomerular complex (PG), have been assumed to originate from the basal plate (the posterior tuberculum) of the diencephalon, whereas relay nuclei in mammals are derived from the alar plate (dorsal thalamus) of the diencephalon. Our results using in situ hybridization show, however, that many pax6- or dlx2-positive cells migrate laterally and ventrocaudally from the diencephalic alar plate to the basal plate during development. Massive clusters of the migrated alar cells become localized in the mantle layer lateral to the posterior tubercular neuroepithelium, from which main nuclei of the PG appear to differentiate. We therefore consider most if not all neurons in the PG to be of alar, not basal, origin. Thus, the teleost PG, at least in part, can be regarded as migrated alar nuclei. Developmental and hodological data strongly suggest that the teleost PG is homologous to a part of the mammalian dorsal thalamus. The organization and origin of the diencephalic sensory relay system might have been conserved across vertebrates.

Animals↗
PubMed2006

The complete mitochondrial genome of a basal teleost, the Asian arowana (Scleropages formosus, Osteoglossidae).

BACKGROUND: Mitochondrial DNA-derived sequences have become popular markers for evolutionary studies, as their comparison may yield significant insights into the evolution of both the organisms and their genomes. From the more than 24,000 teleost species, only 254 complete mtDNA sequences are available (GenBank status on 06 Sep 2006). In this paper, we report the complete mitochondrial genome sequence of Asian arowana, a basal bonytongue fish species, which belongs to the order of Osteoglossiformes. RESULTS: The complete mitochondrial genomic sequence (mtDNA) of Asian arowana (Scleropages formosus) was determined by using shotgun sequencing method. The length of Asian arowana mtDNA is ca. 16,650 bp (its variation is due to polymorphic repeats in the control region), containing 13 protein-coding genes, 22 tRNA and 2 rRNA genes. Twelve of the thirteen protein coding genes were found to be encoded by the heavy strand in the order typically observed for vertebrate mitochondrial genomes, whereas only nad6 was located on the light strand. An interesting feature of Asian arowana mitogenome is that two different repeat arrays were identified in the control region: a 37 bp tandem repeat at the 5' end and an AT-type dinucleotide microsatellite at the 3' end. Both repeats show polymorphism among the six individuals tested; moreover the former one is present in the mitochondrial genomes of several other teleost groups. The TACAT motif described earlier only from mammals and lungfish was found in the tandem repeat of several osteoglossid and eel species. Phylogenetic analysis of fish species representing Actinopterygii and Sarcopterygii taxa has shown that the Asian arowana is located near the baseline of the teleost tree, confirming its status among the ancestral teleost lineages. CONCLUSION: The mitogenome of Asian arowana is very similar to the typical vertebrate mitochondrial genome in terms of gene arrangements, codon usage and base composition. However its control region contains two different types of repeat units at both ends, an interesting feature that to our knowledge has never been reported before for other vertebrate mitochondrial control regions. Phylogenetic analysis using the complete mtDNA sequence of Asian arowana confirmed that it belongs to an ancestral teleost lineage.

Animals↗
PubMed2005

Dopaminergic inhibition of reproduction in teleost fishes: ecophysiological and evolutionary implications.

In many teleosts, dopamine (DA) exerts direct inhibitory control on gonadotropes, counteracting the stimulatory effect of gonadotropin-releasing hormone (GnRH) on gonadotropin release. This dual control by GnRH and DA has been demonstrated in various adult teleosts and has major implications for aquaculture. Because of its unique life cycle, the European eel has provided a powerful model for demonstrating the key role of DA in the control of puberty. Data from tetrapods suggest that the inhibitory role of DA on reproduction is not restricted to the teleosts. Thus, DA inhibitory control could represent an ancient evolutionary component in the neuroendocrine regulation of reproduction that may have been differentially maintained throughout vertebrate evolution. The intensity of DA inhibition, its main site of action, and its involvement in the control of puberty, seasonal reproduction, ovulation, spermiation, or even sex change may differ among classes of vertebrates, as well as within smaller phylogenetic units such as teleosts or mammals. An inhibitory role for DA has been reported also in some invertebrates, indicating that neuronal DA pathways may have been recruited in various groups of metazoa to participate in the control of reproduction. In addition to the incontestable GnRH neurons, the recruitment of DA neurons for the neuroendocrine control of reproduction provides an additional brain pathway for the integration of various species-specific, internal, and environmental cues. In teleosts, the plasticity of the DA neuroendocrine role may have contributed to their large diversity of biological cycles and to their successful adaptation to various environments.

Animals↗
PubMed2005

Effects of a teleost tetraploidization on neuropeptide Y receptor gene repertoire in ray-finned fishes.

The ancestral vertebrate repertoire for neuropeptide Y receptor genes of the Y1 subfamily probably included four subtypes: Y1, Y4, Y6, and Y8. There was probably a single gene in the Y5 category. Both Y1 and Y5 stimulate food intake in mammals. As the genome seems to have duplicated during the evolution of ray-finned fishes, we have investigated the gene repertoire in species that diverged prior to the appearance of teleosts, as well as a basal teleost and a shark. Our results show that the genes Y1, Y5, and Y6, which are missing in many teleosts, are present in basal actinopterygians. These dramatic alterations of the teleost receptor repertoire may be related to the tetraploidization in a teleost ancestor.

Animals↗
PubMed1997

MAP 0, a 400-kDa microtubule-associated protein unique to teleost fish.

Microtubules from neural tissues of the Atlantic cod, Gadus morhua, and of several species of Antarctic teleosts are composed of tubulin and several microtubule-associated proteins (MAPs), one of which has an apparent molecular weight of approximately 400-430 kDa. Because its apparent molecular weight exceeds those of the MAP 1 proteins, we designate this high molecular weight teleost protein MAP 0. Cod MAP 0 failed to cross-react with antibodies specific for MAPs 1A, 1B and 2 of mammalian brain, for MAP H1 of squid optic lobe, and for chicken erythrocyte syncolin, which suggests that it has a novel structure. Similarly, MAP 0 from the Antarctic fish was not recognized by an antibody specific for bovine MAP 2. Together, these observations suggest that MAP 0 is a novel MAP that may be unique to fish. To determine the tissue specificity and phylogenetic distribution of this protein, we generated a rabbit polyclonal antibody against cod MAP 0. Using this antibody, we found that MAP 0 was present in microtubule proteins isolated from cod brain tissues and spinal cord but was absent in microtubules from heart, liver, and spleen. At the subcellular level, MAP 0 was distributed in cod brain cells in a punctate pattern coincident with microtubules but was absent in skin cells. MAP 0 was also detected in cells of the peripheral nervous system. A survey of microtubule proteins from chordates and invertebrates showed that anti-MAP 0-reactive homologs were present in five teleost species but not in more primitive fish and invertebrates or in higher vertebrates. MAP 0 bound to cod microtubules by ionic interaction at a site recognized competitively by bovine MAP 2. Although its function is unknown, MAP 0 does not share the microtubule-binding properties of the motor proteins kinesin and dynein. We propose that MAP 0 is a unique, teleost-specific MAP.

Amphibians↗
PubMed1999

Bulbus arteriosus of the antarctic teleosts. I. The white-blooded Chionodraco hamatus.

The bulbus arteriosus of teleost fish is a thick-walled chamber that extends between the single ventricle and the ventral aorta. The functional importance of the bulbus resides in the fact that it maintains a steady blood flow into the gill system through heart contraction. Despite of this, a thorough study of the structure of the bulbus in teleost fish is still lacking. We have undertaken a morphologic study of the bulbus arteriosus in the stenothermal teleosts of the Antarctic sea. The structural organization of the bulbus arteriosus of the icefish Chionodraco hamatus has been studied here by conventional light, scanning, and transmission electron microscopy. The inner surface of the bulbus shows a festooned appearance due to the presence of longitudinal, unbranched ridges that extend between the ventricle and the arterial trunk. The wall of the bulbus is divided into endocardial, subendocardial, middle, and external layers. Endocardial cells show a large number of moderately-dense bodies. The endocardium invaginates into the subendocardium forming solid epithelial cords that contain numerous secretory vacuoles. Cells in the subendocardium group into small domains, have some of the morphological characteristics of smooth muscle cells, and appear enmeshed in a three-dimensional network of matrix filaments. Cells in the middle layer are typical smooth muscle cells. They appear arranged into layers and are surrounded by a filamentous meshwork that excludes collagen fibers. Orientation of this meshwork occurs in the vicinity of the smooth muscle cells. Elastin fibers are never observed. The external layer is formed by wavy collagen bundles and fibroblast-like cells. This layer lacks blood vessels and nerve fibers. The endocardium and the endocardium-derived cords are secretory epithelia that may be involved in the formation ofmucins or glycosaminoglycans. These mucins may have a protecting effect on the endocardium. The subendocardium and the middle layer appear to be formed by the same cell type, smooth muscle, with a gradient of differentiation from the secretory (subendocardium) to the contractile (middle layer) phenotype. Despite the absence of elastin fibers, the filamentous matrix could maintain the elastic properties of the bulbus wall. Smooth muscle cells appear to be actively involved in bulbus wall dynamics. The restriction of collagen to the external layer suggests that it may control wall dilatation and bulbus compliance. When comparison was possible, structural differences between C. hamatus and temperate teleosts seemed to be not species-related, but of phenotypic adaptative significance. This is remarkable since Antarctic fishes have lived isolated in freezing waters for the last two million years.

Animals↗
PubMed2006

Primary and secondary sensory trigeminal projections in a cyprinid teleost, carp (Cyprinus carpio).

Primary and secondary sensory trigeminal projections were studied by means of tract-tracing methods in a cyprinid teleost, the carp. Tracer injections into the trigeminal nerve root labeled terminals in the ipsilateral principal sensory trigeminal nucleus, descending trigeminal nucleus, medial funicular nucleus, facial lobe, and medial part of posterior lateral valvular nucleus. The principal sensory trigeminal nucleus is considered a major origin of the secondary sensory trigeminal projections in teleosts. To investigate the secondary sensory trigeminal projections, tracer injections were performed into the principal sensory trigeminal nucleus. The present study suggests that the principal sensory trigeminal nucleus projects to the bilateral ventromedial thalamic nucleus, periventricular pretectal nucleus, stratum album centrale of the optic tectum, caudomedial region of lateral preglomerular nucleus, ventrolateral nucleus of semicircular torus, medial part of rostral and posterior lateral valvular nucleus, oculomotor nucleus, trochlear nucleus, trigeminal motor nucleus, facial motor nucleus, superior and inferior reticular formation, descending trigeminal nucleus, medial funicular nucleus, inferior olive, and to the contralateral sensory trigeminal nucleus. These observations indicate that the primary and secondary trigeminal sensory projections of a cyprinid teleost, the carp, are similar to those in percomorph teleosts.

Animals↗