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PubMed1996

Genes encoding giant danio and golden shiner ependymin.

Ependymin (EPN) is a brain glycoprotein that functions as a neurotrophic factor in optic nerve regeneration and long-term memory consolidation in goldfish. To date, true epn genes have been characterized in one order of teleost fish, Cypriniformes. In the study presented here, polymerase chain reactions were used to analyze the complete epn genes, gd (1480 bp), and sh (2071 bp), from Cypriniformes giant danio and shiner, respectively. Southern hybridizations demonstrated the existence of one copy of each gene per corresponding haploid genome. Each gene was found to contain six exons and five introns. Gene gd encodes a predicted 218-amino acid (aa) protein GD 93 percent conserved to goldfish EPN, while sh encodes a predicted 214-aa protein SH 91 percent homologous to goldfish. Evidence is presented classifying proteins previously termed "EPNs" into two major categories: true EPNs and non-EPN cerebrospinal fluid glycoproteins. Proteins GD and SH contain all the hallmark, features of true EPNs.

Amino Acid Sequence↗
PubMed2004

Isolation and characterization of two distinct growth hormone cDNAs from the tetraploid smallmouth buffalofish (Ictiobus bubalus).

The growth hormone (GH) gene has been characterized for a number of fishes and used to establish phylogenetic relationships and population structures. Analysis of tetraploid fishes, such as salmon and some Asian cyprinids, has shown the presence of two GH genes. Fishes in the sucker family (Catostomidae, Cypriniformes) are also tetraploid, and the present study reports the isolation and characterization of two GH cDNAs from a representative species, the smallmouth buffalofish (Ictiobus bubalus). The GH cDNAs of smallmouth buffalofish are 1272 and 1273nt in length, and each codes for a polypeptide of 210 amino acids, predicted to be cleaved to a final product of 188 aa. The GH cDNAs of smallmouth buffalofish are 6% divergent in nt sequence in the coding region, and there are 16 differences in predicted aa sequence. Because the cDNAs have distinct sequences in coding regions and in UTRs, which differed by more than 10%, they were identified as GHI and GHII. The predicted GHI protein contains 4 Cys residues, homologous to other vertebrate GH sequences. On the other hand, GHII has 5 Cys residues, homologous to other ostariophysan sequences. GHI and GHII are most similar to other cypriniform fishes for both nt and protein sequences. Phylogenetically, the sequences of smallmouth buffalofish GH consistently grouped with Asian cyprinids, but not loaches, consistent with morphological evidence suggesting that suckers are most closely related to minnows.

Amino Acid Sequence↗
PubMed1989

A histoenzymological investigation of the caudal neurosecretory system in six species of freshwater teleosts: a comparative study.

Enzymecytochemical features of the caudal neurosecretory system of 6 species of freshwater teleosts, Gudusia chapra, Gonialosa manmina (Clupeidae, Clupeiformes), Oxygaster bacaila (Cyprinidae, Cypriniformes), Mystus bleekeri (Bagridae, Cypriniformes), Sciaena coiter (Scienidae, Perciformes), and Mastacembelus pancalus (Mastacembelidae, Mastacembeliformes) have been investigated with the help of several specific histochemical techniques. No sex-dependent variation have been observed in the enzymecytochemical characteristics of the caudal neurosecretory system of the present species. The Dahlgren cells show intense RNA activity. Caudal neurosecretion lacks carbohydrate but seems to possess small amount of lipid. Acid-phosphatase is located in the Dahlgren cells and axons. Alkaline-phosphatase has been observed in the Dahlgren cells, axons, and urophysial blood-capillaries. Acetylcholine esterase is present in the Dahlgren cells, axons, and urophysis of Mystus, Mastacembelus, and Gonialosa, but lacking in the other 3 species. It is concluded that the caudal neurosecretory system of Mystus, Mastacembelus, and Gopialosa is innervated by cholinergic neurons. Despite their different taxonomic positions, caudal neurosecretory system of all 6 species produce similar responses to various enzymecytochemical tests, except for acetylcholine esterase.

Animals↗
PubMed1980

Structural evidence for two different testicular types in teleost fishes.

Testicular structure in Salmoniformes, Perciformes, Cypriniformes, and Atheriniformes has been examined and reinterpreted on the basis of two different tubular types, distinguished from each other by the intratubular distribution of spermatogonia. In the salmoniform, perciform, and cypriniform teleosts studied, spermatogonia are distributed along the entire length of the testicular tubules. However, in the atheriniform teleosts spermatogonia are restricted to the distal end of the tubule. Sperm development in teleosts is cystic, cysts being comprised of Sertoli-cell processes. In both testicular types described, Sertoli cells phagocytize spermatid residual bodies. Together with the germ cells, they comprise the only intratubular cell types within the teleostean testis. Boundary cells are located immediately outside of the tubule basement membrane. They do not form a complete layer over the tubule surface; therefore, interstitial Leydig cells and blood vessels may border directly upon the tubular basement membrane.

Animals↗
PubMed1989

Motor innervation of respiratory muscles and an opercular display muscle in Siamese fighting fish Betta splendens.

Horseradish peroxidase was used to identify motor neurons projecting to the adductor mandibulae, levator hyomandibulae, levator operculi, adductor operculi, and dilator operculi muscles in Siamese fighting fish, Betta splendens. These muscles participate in the production of respiratory and feeding movements in teleost fishes. The dilator operculi is also the effector muscle for gill-cover erection behavior that is part of Betta's aggressive display. The motor innervation of these muscles in Betta was compared to that previously described for carp. Motor neurons of the adductor mandibulae, levator hyomandibulae, and dilator operculi are located in the trigeminal motor nucleus, and motor neurons of the adductor operculi and levator operculi are located in the facial motor nucleus in Betta and in carp. The trigeminal motor nucleus in both species is divided into rostral and caudal subnuclei. However, there are substantial differences in the organization of the subnuclei, and in the distribution of motor neurons within them. In Betta, the rostral trigeminal subnucleus consists of a single part but the caudal subnucleus is divided into two parts. Motor neurons for the dilator operculi and levator hyomandibulae muscles are located in the lateral part of the caudal subnucleus; the medial part of the caudal subnucleus contains only dilator operculi motor neurons. The single caudal subnucleus in carp is located laterally, and contains motor neurons of both the dilator operculi and levator hyomandibulae muscles. Differences in the organization of the trigeminal motor nucleus may relate to the use of the dilator operculi muscle for aggressive display behavior by perciform fishes such as Betta but not by cypriniform fishes such as carp. Five species of perciform fishes that perform gill-cover erection behavior had a Betta-like pattern of organization of the caudal trigeminal nucleus and a similar distribution of dilator operculi motor neurons. Goldfish, which like carp are cypriniform fish and do not display, had a carp-like trigeminal organization and dilator operculi motor neuron distribution.

Animals↗
PubMed1996

A molecular and morphological perspective on the phylogenetic relationships of the otophysan fishes.

We examined the phylogenetic relationships among the major lineages of otophysan fishes (Cypriniformes, Characiformes, Siluroidei, and Gymnotoidei) using a combined analysis of molecular and morphological characters. The molecular characters comprised 160 phylogenetically informative sites from nuclear-encoded ribosomal RNA and 208 phylogenetically informative sites from the mitochondrial genes encoding ribosomal RNA and the valine transfer RNA for nine otophysan taxa and a gonorynchiform outgroup. The morphological data comprised 85 characters that were obtained from an earlier cladistic study. Congruence among molecular and morphological characters is generally high. The combined analysis supports a sister group relationship between the Gymnotoidei and Siluroidei, which together form a sister group to the Characiformes. The separation of the Cypriniformes from all other otophysans represents the earliest phylogenetic split within the Otophysi. Despire the generally high congruence among molecular and morphological characters, the molecular data analyzed separately produce a topology that differs from the analysis of the combined data. Sources of the taxonomic incongruence between the molecular and morphological data are examined.

Animals↗
PubMed2003

Mitochondrial genomics of ostariophysan fishes: perspectives on phylogeny and biogeography.

Ostariophysi is the second largest superorder within Teleostei. It contains five orders: Gonorynchiformes, Cypriniformes, Characiformes, Siluriformes, and Gymnotiformes. Resolving the higher-level relationships among ostariophysan and related fishes will aid in resolving basal teleostean divergence and provide basis to historical biogeographic analysis of major freshwater fish groups. In this study, we report the complete mitochondrial (mt) DNA sequences for eleven ostariophysan fishes and the results of phylogenetic analyses including these species plus four other ostariophysan and nine non-ostariophysan teleostean fishes. Maximum likelihood and maximum parsimony analyses reconfirmed clupeiforms as the closest relatives of ostariophysans. However, gonorynchiforms were closer to clupeiforms than to otophysans (ostariophysan groups excluding gonorynchiforms), thus raising a question over the current definition of Ostariophysi. The lack of clarity in otocephalan (ostariophysans + clupeiforms) basal relationships implies that such divergence took place over a short period of time. The monophyly of cypriniforms, characiphysans (characiforms, siluriforms, and gymnotiforms), and orders or superorders outside the ostariophysans examined here were conceivably reconstructed. The phylogenetic hypothesis suggests a Pangean origin of otophysans. Within characiphysans, gymnotiforms and siluriforms have independent evolutionary origins and evolutionary histories comparable to or older than that of characiforms. This helps to explain the present geographic distribution of characiphysans.

Animals↗
PubMedDate not supplied

[3 types of sperm proteins in eukaryotes].

Basic spermal proteins of various species of hydrobionts attributed to Pisces and Cephalopoda are studied. It is established that chromatin of nine species referring to two Cypriniformes families includes the somatic histones. Histone H1 of Cypriniformes is attributed to the lysine-rich type histones and contains 35% mol. of lysine and 0.7% mol. of tyrosine. Chromatin of 14 species of fish referring to nine families of the percoid fish superorder includes protamines similar to salmin, a typical protamine of salmon. The amino acidic analysis of protamine from the sandre sperma has shown that it contains 59% mol. of arginine and no tyrosine. Chromatin of three species from squid superorder referring to Cephalopoda includes gametones -- proteins differing from histones and protamines both in the electrophoretic mobility and amino acidic composition (75% mol. of arginine, 3% mol. of tyrosine).

Amino Acids↗
PubMed2000

Gonadotropin-releasing hormones in the brain and pituitary of the teleost, the white sucker.

The present study investigated GnRH forms within the brain of a representative of the order Cypriniformes, the white sucker, Catostomus commersoni, using HPLC, RIA, and immunocytochemistry. Several immunoreactive (ir) GnRH forms were identified in the brain of the white sucker by chromatography and radioimmunoassay, including ir-salmon GnRH, ir-lamprey GnRH-I and -III, and ir-chicken GnRH-II. Results from immunocytochemical studies were consistent with multiple GnRH forms distributed in different patterns, particularly for fibers. Neuronal perikarya containing ir-salmon GnRH and ir-lamprey-like GnRH were found laterally within the preoptic area and rostral hypothalamus. Cells containing exclusively ir-salmon GnRH appeared slightly more rostrally, but in the same region. Fibers containing ir-salmon GnRH and ir-lamprey-like GnRH were seen throughout the caudal telencephalon and extended into the diencephalon, toward the pituitary. Fibers containing ir-chicken-II-like GnRH were also seen in the caudal telencephalon, but were concentrated more dorsally in the diencephalon. Within the pituitary, fibers containing ir-salmon GnRH and ir-lamprey-like GnRH entered the neurohypophysis, but differed in their destinations. Fibers containing ir-salmon GnRH remained within the neurohypophysis, while fibers containing ir-lamprey-like GnRH targeted adenohypophyseal tissue. These findings are consistent with the hypothesis that multiple GnRH forms with multiple functions exist within the brain and pituitary of teleosts and provide further evidence of a lamprey-like GnRH within an early evolved teleost species.

Amino Acid Sequence↗
PubMed2006

Mitochondrial molecular clocks and the origin of the major Otocephalan clades (Pisces: Teleostei): A new insight.

The Otocephala, a clade including ostariophysan and clupeomorph teleosts, represents about a quarter of total fish species diversity, with about 1000 genera and more than 7000 species. A series of recent papers have defended that the origin of this clade and of its major groups may be significantly older than the oldest fossils of each of these groups suggest. Some of these recent papers explicitly defend a Pangean origin for some otocephalan groups such as the Siluriformes or Cypriniformes. To know whether or not the otocephalans as a whole, and particularly the mainly freshwater, cosmopolitan otophysans could have originated before the splitting of the Pangean supercontinent is of extreme importance, since otophysan fishes are among the most useful animal groups for the determination of historical continental relationships. In the present work we examined divergence times for each major otocephalan group by an analysis of complete mtDNA sequences, in order to investigate if these divergence times support the hypotheses advanced in recent studies. The complete mtDNA sequences of nine representative non-otocephalan fish species and of twenty-one representative otocephalan species was compared. The present study is thus, among the studies dealing with molecular divergence times of teleosts, the one in which a greater number of otocephalan species are included. The divergence times obtained support that the major otocephalan groups had a much older origin than the oldest fossil records available for these groups suggest. The origin of the Otocephala is estimated as having occurred about 282 Mya, with the origin of the Otophysi being estimated at about 251 Mya.

Animals↗
PubMed2006

The fish endocrine pancreas: review, new data, and future research directions in ontogeny and phylogeny.

The literature on the ontogeny and phylogeny of the endocrine pancreas of ray-finned fishes is summarized since the latest review in fish [Youson, J.H., Al-Mahrouki, A.A., 1999. Review. Ontogenetic and phylogenetic development of the endocrine pancreas (islet organ) in fishes. Gen. Comp. Endocrinol. 116, 303-335]. A basic description and a demonstration of the diversity of the fish islet organ is provided through new immunohistochemical data on islet tissue from a basal teleost, an osteoglossomorph, and a more derived teleost, a perciforme. Unlike the previous review, the present report provides a review and discussion of the utility of sequence data of insulin, somatostatin, and NPY- and glucagon-family peptides in phylogenetic analyses of jawed and jawless fishes. The present study also provides the first comparative analysis of sequences of preprohormones of endocrine peptides from closely related basal teleost species. Some nucleotide and deduced amino acid sequence data for preprosomatostatins (PPSS-I and/or -II) are compared for four species of bonytongues, Osteoglossomorpha, and with PPSSs of the white sucker, Catostomus commersoni, representing Cypriniformes, a more generalized teleost order. Phylogenetic analysis of deduced amino acid sequences of the PPSSs of these species and others from databases indicates good support for the monophyly of Osteoglossomorpha and some support for the present taxonomic grouping of the osteoglossomorphs examined, and also the white sucker. However, PPSS may have limited phylogenetic utility due to the relative short sequence, particularly in resolving relationships among lineages that diverged over a short period of time. Since in the few fish species examined we have just touched the surface in describing the diversity of structure of the islet organ, and likely the nature of the products of its cells, this report promotes the continued study of this organ.

Amino Acid Sequence↗
PubMed2001

Identification and ultrastructural characterization of a novel virus from fish.

During routine investigations on fish, a virus (isolate DF 24/00) with novel morphological features and hitherto undescribed morphogenesis was isolated from a white bream (Blicca bjoerkna L.; Teleostei, order Cypriniformes). Cell-free virions consist of a rod-shaped nucleocapsid (120-150x19-22 nm) similar to that seen in baculoviruses. The virion has a bacilliform shape (170-200x75-88 nm) reminiscent of rhabdoviruses with an envelope containing coronavirus-like spikes (20-25 nm). DF 24/00 replicated well in various fish cell lines. Inhibitor studies with 5-iodo-2'-deoxyuridine indicated that the viral genome consists of RNA and chloroform sensitivity correlated with ultrastructural demonstration of enveloped virions. The buoyant density of the virus determined in sucrose was 1.17-1.19 g/ml. Preliminary biochemical characterization revealed the presence of six antigenic glycoproteins, three of which contain sugars with concanavalin-A specificity. Ultrastructurally, morphogenesis of virus progeny was detected only in the cytoplasm. Nucleocapsids were observed to bud through membranes of the endoplasmic reticulum and/or Golgi apparatus into dilated vesicles. Egress of mature virions occurs primarily by exocytosis and, only very rarely, by budding directly at the plasma membrane. Morphologically similar viruses had previously been isolated from grass carp (Ctenopharyngodon idella), blue crab (Callinectis sapidus), European shore crab (Carcinus maenas) and shrimp (Penaeus monodon). To date, none of them has been classified. In summary, the first characterization of a new virus that might represent a member of a novel virus family that has morphological features resembling those found in rhabdo-, corona- and baculoviruses is presented.

Animals↗
PubMed1989

Afferent connections of the valvula cerebelli in two teleosts, the common goldfish and the green sunfish.

The afferent connections of the valvula cerebelli were examined in one cypriniform teleost (Carassius auratus) and one perciform teleost (Lepomis cyanellus) with the use of horseradish peroxidase as a retrograde tracer. Both species have ipsilateral input to the valvula from the central pretectal and dorsal accessory optic nuclei, the dorsal and ventral tegmental nuclei, the lateral nucleus of the valvula, the perilemniscal nucleus, and nucleus isthmi and contralateral input from the inferior olivary nucleus. In addition, Carassius has ipsilateral valvulopetal projections from the eminentia granularis, the prae-eminential nucleus, and the isthmic primary sensory trigeminal nucleus, whereas Lepomis has bilateral (stronger ipsilaterally) valvulopetal projections from the nucleus of the locus coeruleus and the rostral corpus cerebelli. The topographical order of the cerebellopetal projections of the lateral nucleus of the valvula and inferior olive is also described, as are differential inputs to various subdivisions of the cerebellum in the two species. Information on valvulopetal projections in teleosts has thus far been limited to electroreceptive mormyrids. The present study shows that many valvular inputs related to electroreception in mormyrids have no homologue in Carassius and Lepomis. Finally, the present study indicates that the rostral part of the corpus cerebelli, but not the valvula cerebelli, in teleosts is the homologue of the anterior lobe of the corpus cerebelli in cartilaginous fishes. Thus, the valvula cerebelli is a shared derived feature (synapomorphy) of all ray-finned fishes.

Animals↗
PubMed1993

Cytoarchitecture, fiber connections, and ultrastructure of the nucleus pretectalis superficialis pars magnocellularis (PSm) in carp.

The cytoarchitecture, fiber connections, and ultrastructure of the nucleus pretectalis superficialis pars magnocellularis (PSm) were studied in cypriniform teleosts (Cyprinus carpio). The PSm is an oval nucleus in the pretectum. Medium-sized cells and synaptic glomeruli are the main components of the nucleus. A lesser number of small cells are also present. Most of the medium-sized cells form one or two cell layers on the periphery of the nucleus, and some cells are scattered among synaptic glomeruli in the nucleus. Cell bodies in the peripheral cell layer are pyriform and sprout a thick dendrite directed inward. The dendrite gives off fine dendritic branches, which are postsynaptic elements in synaptic glomeruli. The PSm projects to the ipsilateral corpus mamillare (CM) and sends collaterals to the ipsilateral nucleus lateralis valvulae (NLV). Axons of the PSm neurons have terminals with many varicosities in the CM, and collaterals in the NLV have cup-shaped terminals around the cell bodies of the NLV neurons. Following horseradish peroxidase (HRP) injections into the PSm, HRP-labeled cells are found ipsilaterally in the optic tectum, the nucleus tractus rotundus of Schnitzlein, and the nucleus ruber of Goldstein. The tecto-PSm projections are topographically organized. The rostral optic tectum projects mainly to the rostral portion of the PSm, and the caudal tectum projects to the caudal portion of the PSm. The ventral tectum sends fibers mainly to the ventral part of the PSm. The dorsomedial tectum projects to the medial part of the PSm, and the dorsolateral tectum projects to the lateral part of the PSm. Tectal projection neurons to the PSm are of only one type. The tectal cell body is pyriform and is situated in the superficial part of the ipsilateral stratum periventriculare (SPV). The tectal neurons have a long perpendicular dendrite, which branches out in the stratum opticum (SO). An axon emerges from the branching site in the SO. Judging from the dendritic branching pattern of the tectal projection neurons, we concluded that the PSm receives visual information from the optic tectum.

Animals↗
PubMed1994

Development of the retinofugal projections in the embryonic and larval zebrafish (Brachydanio rerio).

Studies of the projection from the vertebrate retina have contributed significantly to current concepts of neural development. The zebrafish has recently become a favored system for the study of development in general and neural development in particular. Although the development of both the optic nerve and the retinotectal projection of the zebrafish has been described, the retinofugal projection in its entirety has not. This paper describes it and also addresses the issue of projectional exuberance: i.e., transient projections to targets that are not innervated in the adult. The retinofugal projection of embryonic and larval zebrafish (32 hours to 7 days post-fertilization) was labeled by intraocular injection of DiI (1,1'-dioctadecyl-3,3,3',3',tetramethylindocarbocyanine perchlorate) and then studied in wholemounts and sections. The first optic axons crossed the chiasm at 32 hours post-fertilization and projected in a straight line to reach the tectum at about 44 hours. At 48 hours, a few optic axons deviated along either the tract of the posterior commissure or the tract of the postoptic commissure. By 72 hours (about the time of hatching) optic axons arborized in ten distinct regions, termed arborization fields. At 6-7 days post-fertilization, the same ten arborization fields (nine contralateral, one bilateral) were evident. Most of the arborization fields were located in the superficial neuropil and were not associated with morphologically identifiable clusters of somata. On the basis of various landmarks, the ten arborization fields are identified as precursors of retinorecipient nuclei previously described in other adult cypriniform fishes. The development was characterized by the nearly complete absence of any transient projections. Thus, the idea that axonal outgrowth is initially exuberant and trimmed back later is not supported by these results.

Afferent Pathways↗
PubMed2002

Distribution of GFAP immunoreactive structures in the rhombencephalon of the sterlet (Acipenser ruthenus) and its evolutionary implication.

Previous studies have revealed that although the brains of cypriniform teleosts (iberian barb, Barbus comiza; carp, Cyprinus carpio; goldfish, Carassius auratus) are rich in glial fibrillary acidic protein (GFAP), they have, however, areas devoid of GFAP immunoreactivity. The largest ones of these are in the rhombencephalon, e.g., the zones of the sensory and motor neurons in the vagal lobe. Our studies in amniotes suggested that the GFAP immunonegative areas could be characteristic of the more advanced brains (avian and mammalian), whereas no similar areas were found in reptiles. A similar tendency was found in the Chondrichthyes, i.e., GFAP immunonegative areas appeared as brain complexity progressed. The question arose whether the GFAP immunonegative brain areas in the Teleostei were also the result of such a tendency. Within the radiation of ray-finned fishes (Actinopterygii), Chondrostei represent a less advanced level as compared to the Teleostei. Therefore, the distribution of GFAP immunoreactivity was investigated in the rhombencephalon of the sterlet (Acipenser ruthenus) as a representative of Chondrostei, and in the carp. Serial vibratome sections were processed according to the avidin-biotinylated horseradish peroxidase method.Several comparable GFAP immunoreactive structures were found in the two species: the dense periventricular ependymoglial plexus, the midsagittal glial septum, the small glial septa separating the nerve fiber bundles, and the wide glial endfeet lining the meningeal surface. In the vagal lobe in the zones adjacent to the meningeal and ventricular surfaces, the glial structures also proved to be similar. In contrast to the carp, however, no areas were found devoid of GFAP immunoreactivity in the sterlet.The results suggest that this trend of glial evolution, i.e., GFAP immunonegative areas appearing as brain complexity progressed, is a common feature shared by Actinopterygii, Amniota, and Chondrichthyes, despite their separate evolutionary histories. J. Exp. Zool. 293:395-406, 2002.

Animals↗
PubMed1992

Evolutionary modification of regenerative capability in vertebrates: a comparative study on teleost pectoral fin regeneration.

The regenerative ability of the pectoral fins of 14 species from 6 euteleostean families was tested. Blastema formation and distal outgrowth was observed in all species, indicating the initiation of regeneration in all species tested. Interspecific variation exists with respect to the frequency of malformations and the patterns produced by heteromorphic regeneration. Taking into account published reports on pectoral fin regeneration, the systematic distribution of homo- and heteromorphic regeneration leads to the following conclusions: 1) regenerative ability of pectoral fins is a property inherited from the common ancestor of euteleosteans. Whether it is also the ancestral condition for the whole teleostean group cannot be determined, because reports on more primitive teleosteans like the herring and the osteoglossimorphs are missing. 2) A propensity to produce high frequencies of heteromorphic regenerates originated independently at least three times in Cypriniformes, Scorpaeniformes, and Perciformes. 3) Impaired regeneration is most commonly found in bottom fishes, although not all ground fish groups show heteromorphic regeneration. This suggests that impaired regeneration is not directly related to bottom dwelling, but most probably originated as a side effect of other adaptive changes. Hence, neither the presence nor the loss of faithful regeneration can be associated with particular adaptive scenarios in this group, since regeneration seems to be ancestral to all major euteleost groups and its loss has no clear adaptive significance. Whether there are adaptive reasons to maintain regenerative capability or whether there are cases of reestablishment of regeneration after it was lost cannot be decided on the basis of recent evidence. More observations on phylogenetically closely related species with variable regenerative capability are necessary to assess adaptive explanations of regeneration.

Animals↗
PubMed1998

Molecular phylogeny of Cyprinidae inferred from cytochrome b DNA sequences.

Phylogenetic relationships between European cyprinids (Teleostei:Cypriniformes:Cyprinidae) were investigated by comparing cytochrome b gene sequences from 29 species, among which 20 were newly sequenced. Results were in general agreement with previous morphologically-based studies, but new interesting relationships were found. The classical barbelled/lacking barbels split is dubious. Genus Leuciscus appears paraphyletic. The phylogenetic location of some American cyprinid species was recovered; at least two distinct invasions of the New World are likely. Finally, the problem of intergeneric cyprinid hybrids is addressed. The genus rank for these interbreeding entities is supported and hybrids are seen as the consequence of a high genetic flexibility. This is the first molecularly based study of cyprinid diversity. It sheds light on the evolution and taxonomy of this major freshwater fish family.

Animals↗