Home About us Contact
|
Home About us Contact | ||
|
|
||
Ray-finned Fishes (ray-finned + fish)
Selected AbstractsExpression of Hoxa-11 and Hoxa-13 in the pectoral fin of a basal ray-finned fish, Polyodon spathula: implications for the origin of tetrapod limbsEVOLUTION AND DEVELOPMENT, Issue 3 2005Brian D. Metscher Summary Paleontological and anatomical evidence suggests that the autopodium (hand or foot) is a novel feature that distinguishes limbs from fins, while the upper and lower limb (stylopod and zeugopod) are homologous to parts of the sarcopterygian paired fins. In tetrapod limb development Hoxa-11 plays a key role in differentiating the lower limb and Hoxa-13 plays a key role in differentiating the autopodium. It is thus important to determine the ancestral functions of these genes in order to understand the developmental genetic changes that led to the origin of the tetrapod autopodium. In particular it is important to understand which features of gene expression are derived in tetrapods and which are ancestral in bony fishes. To address these questions we cloned and sequenced the Hoxa-11 and Hoxa-13 genes from the North American paddlefish, Polyodon spathula, a basal ray-finned fish that has a pectoral fin morphology resembling that of primitive bony fishes ancestral to the tetrapod lineage. Sequence analysis of these genes shows that they are not orthologous to the duplicated zebrafish and fugu genes. This implies that the paddlefish has not duplicated its HoxA cluster, unlike zebrafish and fugu. The expression of Hoxa-11 and Hoxa-13 in the pectoral fins shows two main phases: an early phase in which Hoxa-11 is expressed proximally and Hoxa-13 is expressed distally, and a later phase in which Hoxa-11 and Hoxa-13 broadly overlap in the distal mesenchyme of the fin bud but are absent in the proximal fin bud. Hence the distal polarity of Hoxa-13 expression seen in tetrapods is likely to be an ancestral feature of paired appendage development. The main difference in HoxA gene expression between fin and limb development is that in tetrapods (with the exception of newts) Hoxa-11 expression is suppressed by Hoxa-13 in the distal limb bud mesenchyme. There is, however, a short period of limb bud development where Hoxa-11 and Hoxa-13 overlap similarly to the late expression seen in zebrafish and paddlefish. We conclude that the early expression pattern in tetrapods is similar to that seen in late fin development and that the local exclusion by Hoxa-13 of Hoxa-11 from the distal limb bud is a derived feature of limb developmental regulation. [source] The phylogenetic position of toadfishes (order Batrachoidiformes) in the higher ray-finned fish as inferred from partitioned Bayesian analysis of 102 whole mitochondrial genome sequencesBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2005MASAKI MIYA In a previous study based on 100 whole mitochondrial genome (mitogenome) sequences, we sought to provide a new perspective on the ordinal relationships of higher ray-finned fish (Actinopterygii). The study left unexplored the phylogenetic ,position, of, toadfishes, (order, Batrachoidiformes),, as, data, were, unavailable, owing, to, technical, difficulties. In the present study, we successfully determined mitogenomic sequences for two toadfish species (Batrachomoeus trispinosus and Porichthys myriaster) and found that the difficulties resulted from unusual gene arrangements and associated repetitive non-coding sequences. Unambiguously aligned, concatenated mitogenomic sequences (13 461 bp) from 102 higher actinopterygians (excluding the ND6 gene and control region) were divided into five partitions (1st, 2nd and 3rd codon positions of the protein-coding genes, tRNA genes and rRNA genes) and partitioned Bayesian analyses were conducted. The resultant phylogenies strongly suggest that the toadfishes are not members of relatively primitive higher actinopterygians (Paracanthopterygii), but belong to a crown group of actinopterygians (Percomorpha), as was demonstrated for ophidiiform eels (Ophidiiformes) and anglerfishes (Lophiiformes) in the previous study. We propose revised limits of major unranked categories for higher actinopterygians and a new name (Berycomorpha) for a clade comprising two reciprocally paraphyletic orders (Beryciformes and Stephanoberyciformes) based on the present mitogenomic phylogenies. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 85, 289,306. [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] Mating preferences, sexual selection and patterns of cladogenesis in ray-finned fishesJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 2 2007J. E. MANK Abstract Evolutionary theory predicts that sexual selection may increase taxonomic diversity when emergent mating preferences result in reproductive isolation and therefore speciation. This theory has been invoked to explain patterns of diversity in ray-finned fishes (most notably in the cichlids), but the theory has not been tested comparatively in fish. Additionally, several other unrelated factors have been identified as promoters of cladogenesis, so it is unclear how important sexual selection might be in diversification. Using sister-clade analysis, I tested the relationship between the presence of sexually selected traits and taxonomic diversification in actinopterygiian fishes, a large clade that shows substantial diversity in mating preferences and related sexually selected traits. In all identified sister-families that differed with regard to the proportion of species manifesting sexually selected traits, sexual selection was correlated with increased diversification, and this association was significant across all sister clades (P = 0.02). This suggests that sexual selection, when present, is a substantial driver of diversification in the ray-finned fishes, and lends further empirical support to the theoretical link between mating preferences and accelerated cladogenesis. [source] The evolution of reproductive and genomic diversity in ray-finned fishes: insights from phylogeny and comparative analysisJOURNAL OF FISH BIOLOGY, Issue 1 2006J. E. Mank Collectively, ray-finned fishes (Actinopterygii) display far more diversity in many reproductive and genomic features than any other major vertebrate group. Recent large-scale comparative phylogenetic analyses have begun to reveal the evolutionary patterns and putative causes for much of this diversity. Several such recent studies have offered clues to how different reproductive syndromes evolved in these fishes, as well as possible physiological and genomic triggers. In many cases, repeated independent origins of complex reproductive strategies have been uncovered, probably reflecting convergent selection operating on common suites of underlying genes and hormonal controls. For example, phylogenetic analyses have uncovered multiple origins and predominant transitional pathways in the evolution of alternative male reproductive tactics, modes of parental care and mechanisms of sex determination. They have also shown that sexual selection in these fishes is repeatedly associated with particular reproductive strategies. Collectively, studies on reproductive and genomic diversity across the Actinopterygii illustrate both the strengths and the limitations of comparative phylogenetic approaches on large taxonomic scales. [source] | ||||||||||