Recent Teleosts Research Articles

No evidence for the radiation time lag model after whole genome duplications in Teleostei.

The short and long term effects of polyploidization on the evolutionary fate of lineages is still unclear despite much interest. First recognized in land plants, it has become clear that polyploidization is widespread in eukaryotes, notably at the origin of vertebrates and teleost fishes. Many hypotheses have been proposed to link the species richness of lineages and whole genome duplications. For instance, the radiation time lag model suggests that paleopolyploidy would favour the apparition of new phenotypic traits, although the radiation of the lineage would not occur before a later dispersion event. Some results indicate that this model may be observed during land plant evolution. In this work, we test predictions of the radiation time lag model using both fossil data and molecular phylogenies in ancient and more recent teleost whole genome duplications. We fail to find any evidence of delayed increase of the species number after any of these events and conclude that paleopolyploidization still remains to be unambiguously linked to taxonomic diversity in teleosts.

Comparative physical maps derived from BAC end sequences of tilapia (Oreochromis niloticus)

BackgroundThe Nile tilapia is the second most important fish in aquaculture. It is an excellent laboratory model, and is closely related to the African lake cichlids famous for their rapid rates of speciation. A suite of genomic resources has been developed for this species, including genetic maps and ESTs. Here we analyze BAC end-sequences to develop comparative physical maps, and estimate the number of genome rearrangements, between tilapia and other model fish species.ResultsWe obtained sequence from one or both ends of 106,259 tilapia BACs. BLAST analysis against the genome assemblies of stickleback, medaka and pufferfish allowed identification of homologies for approximately 25,000 BACs for each species. We calculate that rearrangement breakpoints between tilapia and these species occur about every 3 Mb across the genome. Analysis of 35,000 clones previously assembled into contigs by restriction fingerprints allowed identification of longer-range syntenies.ConclusionsOur data suggest that chromosomal evolution in recent teleosts is dominated by alternate loss of gene duplicates, and by intra-chromosomal rearrangements (~one per million years). These physical maps are a useful resource for comparative positional cloning of traits in cichlid fishes. The paired BAC end sequences from these clones will be an important resource for scaffolding forthcoming shotgun sequence assemblies of the tilapia genome.

Kitb, a second zebrafish ortholog of mouse Kit

The large numbers of duplicated pairs of genes in zebrafish compared to their mammalian counterparts has lead to the notion that expression of zebrafish co-orthologous pairs in some cases can together describe the expression of their mammalian counterpart. Here, we explore this notion by identification and analysis of a second zebrafish ortholog of the mammalian Kit receptor tyrosine kinase (kitb). We show that in embryos, kitb is expressed in a non-overlapping pattern to that of kita, in the anterior ventral mesoderm, Rohon-beardRohon-Beard neurons, the otic vesicle, and trigeminal ganglia. The expression pattern of kita and kitb in zebrafish together approximates that of Kit in mouse, with the exception that neither zebrafish kit gene is expressed in primordial germ cells, a site of kit expression in the mouse embryo. In addition, zebrafish kita is expressed in a site of zebrafish primitive hematopoiesis but not required for blood development, and we fail to detect kitb expression in sites of zebrafish hematopoiesis. Thus, the expression and function of zebrafish kit genes cannot be described as a simple partition of the expression and function of mouse Kit. We discuss the possibility that these unaccounted for expression domains and functions are derived from more ancestral gene duplications and partitioning instead of the relatively recent teleost teleost-specific duplication.

Differential expression of neural and gonadal aromatase enzymatic activities in relation to gonadal development in Japanese eel,Anguilla japonica

The objectives of the present study were to investigate the enzymatic characteristics of brain aromatase in Japanese eel, Anguilla japonica, as well as the correlations between aromatase activities in various tissues (brain regions, pituitary, and gonads) and ovarian development. Eel brain aromatase exhibited a K(m) of 75 nM and a V(max) of 1.14 fmol/min mg protein (91.5 fmol/h mg protein), indicating an enzymatic activity much lower than in other teleosts but similar to that in mammals. This supports the hypothesis of the occurrence of a single aromatase gene in eels (representative of an ancient group of teleosts, Elopomorphs), as in mammals, but unlike what is observed in more recent teleosts. Aromatase inhibitors could significantly suppress brain and pituitary aromatase activity. There was no significant sex difference in aromatase activity in the forebrain, midbrain, hindbrain, or pituitary, but there was in the gonads, where aromatase could be detected in the ovaries but not in the testes, in accordance with the role of this enzyme in ovarian differentiation. Comparison with another teleost, black porgy (Percomorph), under the same experimental conditions, further confirmed the low activity of aromatase in the eel. We investigated variations in brain, pituitary, and gonad aromatase activity in relation to ovarian development in control female eels (gonadosomatic index, GSI, 0.1-1.6%) as well as in eels treated with pituitary extract (experimental ovarian maturation; GSI up to 25%). Differential expression of neural and gonadal aromatase was observed in relation to the course of gonadal development. Pituitary aromatase activity increased with GSI at all stages. Brain (specially forebrain) aromatase activity significantly increased in early vitellogenic control eels (GSI>0.8%) and in treated eels. The low activity of eel aromatase may be related to the characteristic life cycle of the eel, in which there is a long delay of the onset of puberty before oceanic reproductive migration.

Characterization of carbonic anhydrase and anion exchange in the erythrocytes of bowfin ( Amia calva), a primitive air-breathing fish

The purpose of this study was to investigate the characteristics of carbonic anhydrase (CA) and the Cl −/HCO 3 − exchanger (Band 3; AE1) in the erythrocytes of bowfin ( Amia calva), a primitive air-breathing fish, in order to further understand the strategies of blood CO 2 transport in lower vertebrates and gain insights into the evolution of the vertebrate erythrocyte proteins, CA and Band 3. A significant amount of CA activity was measured in the erythrocytes of bowfin (70 mmol CO 2 min −1 ml −1), although it appeared to be lower than that in the erythrocytes of teleost fish. The turnover number ( K cat) of bowfin erythrocyte CA was intermediate between that of the slow type I CA isozyme in agnathans and elasmobranchs and the fast type II CA in the erythrocytes of the more recent teleost fishes, but the inhibition properties of bowfin erythrocyte CA were similar to the fast mammalian CA isozyme, CA II. In contrast to previous findings, a plasma CA inhibitor was found to be present in the blood of bowfin. Bowfin erythrocytes were also found to possess a high rate of Cl −/HCO 3 − exchange (6 nmol HCO 3 − s −1 cm −2) that was sensitive to DIDS. Visualization of erythrocyte membrane proteins by SDS-PAGE revealed a major band in the 100 kDa range for the trout, which would be consistent with the anion exchanger. In contrast, the closest major band for the membranes of bowfin erythrocytes was around the 140 kDa range. Taken together, these results suggest that the strategy for blood CO 2 transport in bowfin is probably similar to that in most other vertebrates despite several unique characteristics of erythrocyte CA and Band 3 in these primitive fish.

Comments on Basal Teleosts and Teleostean Phylogeny, by Gloria Arratia

For more than 20 years, Gloria Arratia has been a prolific contributor on Mesozoic fossil fishes and on the skeletal ontogeny and morphology of Recent teleosts. Often writing with her husband, Hans-Peter Schultze, she has produced (among much else) a notable series of papers on the caudal skeleton of Recent lower teleosts and on the palatoquadrate and urohyal (e.g., Arratia, 1991; Arratia and Schultze, 1991, 1992). Her most recent monograph (Arratia, 1997) covers Jurassic fossils representing eight genera (one of which is the Recent Elops), two of them new, and also describes the firstJurassic leptocephali or transforming leptocephali. As usual with Arratia's work, the descriptions of fossils are as complete as the specimens allow, and the illustrations are excellent.

The corpuscles of Stannius in arawana ( Osteoglossum bicirrhosum), an ancient teleost

The corpuscles of Stannius of arawana ( Osteoglossum bicirrhosum), an ancient teleost, were examined by routine light and electron microscopy and following their immunoreactivity to salmon and trout stanniocalcin antisera. Periodic acid-Schiff positive cells of the corpuscles of Stannius had a follicular arrangement and demonstrated a strong immunohistochemical reaction with both stanniocalcin antisera. Fine structural analysis of the paired, posteriorly located, and perirenal ovoid glands revealed two morphologically distinct cell types the basal laminae of which were ramified by nerve terminals. Immunocytochemistry demonstrated that osmiophilic secretory granules in both cell types were immunoreactive to the stanniocalcin antisera. When extracts of arawana corpuscles of Stannius were subjected to sodium dodecyl sulphate electrophoresis and Western blot analysis a diffuse molecular weight band was evident (∼68 kDa) in the non-reduced condition. In all cases, immunoreactivity was abolished by preabsorption of the antisera with salmon stanniocalcin or with a crude extract of arawana corpuscles of Stannius. The corpuscles of Stannius of arawana are similar to those in more recent teleosts with respect to cell structure and their anatomical distribution but their stanniocalcin is more similar in molecular weight to that present in at least one other non-teleost actinopterygian (the gar) which has an ancient lineage.

Olfactory organ of acipenseriformes and comparison with other actinopterygians: Patterns of diversity.

The position and structure of the olfactory organ and its openings vary among actinopterygians. The anterior nasal opening is a simple perforation in the skin in many extant actinopterygians (e.g., acipenseriforms, lepisosteids, and primitive Recent teleosts) and represents the primitive condition. Polypterids and Amia each exhibit a derived condition, in which the anterior nasal opening extends into a tube. The olfactory organ is relatively far away from the anterior end of the elongate rostrum in acipenseriforms, whereas the olfactory organs are closer to the anterior end of the snout in extant actinopterygians (e.g., polypterids, lepisosteids, and amiids). In adults, olfactory organs are cuplike structures in most actinopterygians, but these organs are tubelike in polypterids. Among extant actinopterygians, a nasal diverticulum is present only in polypterids. Teleosts have accessory nasal sacs, but chondrosteans, polypterids, lepisosteids, and amiids lack them. The olfactory rosette is formed by primary folds or lamellae that may be placed anterior, lateral, posterior, and/or medial to the axis of the organ. Large acipenserids have 20-32 lamellae, polyodontids have 13-18 lamellae, lepisosteids have 8-10 lamellae, and Amia may have over 100. In teleosts, the number of lamellae varies from none or a few to over 200. Secondary lamellae are present in acipenseriforms, lepisosteids, and some advanced teleosts; secondary lamellae are interpreted as independently acquired in these lineages. Secondary lamellae are absent in Amia and primitive teleosts such as Elops and Hiodon. Tertiary lamellae are present in Acipenser oxyrhynchus. The arrangement of the primary lamellae in relation to the axis of the organ results in at least 11 patterns of the olfactory rosette in actinopterygians. Lamellae that are enclosed in a tubelike sac and that have an anteromedial diverticulum are specializations of polypterids. Primary lamellae anterior, lateral, and posterior to an elongate axis are characteristic of lepisosteids. The presence of primary lamellae lateral, medial, and posterior to an elongate olfactory axis is a synapomorphy of Halecomorpha (Amia plus teleosts). The absence of secondary lamellae is a synapomorphy of Halecomorpha. © 1994 Wiley-Liss, Inc.

Reevaluation of the caudal skeleton of some actinopterygian fishes: II. Hiodon, Elops, and Albula.

The vertebral centra of Hiodon, Elops, and Albula are direct perichordal ossifications (autocentra) which enclose the arcocentra as in Amia. An inner ring of ovoid cells forms in late ontogeny from the intervertebral space inside the autocentrum. The chordacentrum is reduced or completely absent in centra of adult Elops, whereas it forms an important portion of the centra in adult Hiodon. The posterior portion of the compound ural centrum 3+4+5 is partially (Hiodon) or fully formed by the chordacentrum (Elops, Albula). The haemal arches and hypurals are fused medially by cartilage or bone trabecles of the arcocentrum with the centra, even though they appear autogenous in lateral view in Elops and Albula. The composition of the caudal skeleton of fossil teleosts and the ontogeny of that of Hiodon, Elops, and Albula corroborate a one-to-one relationship of ural centra with these dorsal and ventral elements. The first epural (epural 1) of Elops relates to ural centrum 1, whereas the first epural (epural 2) of Hiodon and Albula relates to ural centrum 2. In Albula, the first ural centrum is formed by ural centrum 2 only. With 4 uroneurals Hiodon has the highest number within recent teleosts. Juvenile specimens of Hiodon have eight, the highest number of hypurals within recent teleosts; this is the primitive condition by comparison with other teleosts and pholidophorids. Reduction of elements in the caudal skeleton is an advanced feature as seen within elopomorphs from Elops to Albula. Such reductions and fusions occur in osteoglossomorphs also, but the lack of epurals and uroneurals separates most osteoglossomorphs (except Hiodon) from all other teleosts.

Semicircular canal size in fossil fishes and amphibians

Mean semicircular canal radius of curvature as a function of body mass was estimated for 18 fossil fish and 2 fossil labyrinthodont amphibians. The statistically significant regression for fossil fish is closely comparable to that of Recent teleosts, but both differ substantially from that of Recent mammals. Fossil labyrinthodont amphibian data points fall fairly close to those of Recent mammals, suggesting that all tetrapods are characterized by smaller semicircular canal dimensions than those of fish. No simple explanation of this dichotomy can be offered because several other important parameters which may affect semicircular canal sensitivity are presently poorly known, or cannot be measured in fossils.

A morphological study of luciocephalus pulcher, with notes on gular elements in other recent teleosts.

AbstractThe monotypic perciform suborder Luciocephaloidei possesses the following, previously unknown, salient morphological characters: a third joint, the nasopalatopterygoid, between neurocranium and suspensorium; a toothless and dorsally exposed prevomer; no pharyngeal processes on either parasphenoid or basioccipital; a tympanum‐covered foramen exoccipitale in the saccular bulla as a hearing organ; a gular ossification; a craniovertebral joint with small exoccipital condyles widely separated from the basioccipital condyle; and a large physoclystic swimbladder with a notable caudal extension. The seemingly functionless gular‐like mental ossification is considered a paleomorphic structure with a neogenetic development. Attenuation in longitudinal growth is evident in the derivatives and dermal additions of the mandibular arch and nasal capsule while other regions of the head have remained independent. The primary adaptive significance of the attenuation in the growth of the entire preorbital region is the accomodation of oral incubation. Secondarily the elongate jaws increase both the speed and grasping range of the bite in prey catching. The degree of jaw protrusion depends mainly on the length of the maxillary. The exaggerated length of the ascending processes of the premaxillaries may be the result of a positive differential growth rate within one growth field. The meaning of the preponderance of parallel‐fibered cranial muscles is discussed in respect to holding functions, greatest possible excursion of the insertion with minimum loss of force, and muscle fiber length. Based on the overall morphology, the monotypic suborder Luciocephaloidei is retained.

A preliminary report on the role of the pineal organ in the control of pigment cells and light reactions in recent teleost fishes.

A preliminary report on the role of the pineal organ in the control of pigment cells and light reactions in recent teleost fishes.

Scientific Serials

THE Quarterly Journal of Microscopical Science for February, 1896, contains:—On the early development of Amia, by Bashford Dean (Plates 30-32). Amia calva, possibly the sole survivor of the race of the Mesozoic Ganoids, claims our special interest as the nearest ancestral form of some, if not of all, of our recent Teleosts. In embryology the Ganoid and the Teleost still stand widely separate; there has even been a tendency to look upon these kindred forms as representing different phyla, early divergent from a primitive chordate ancestor. This, therefore, renders the details given by Dr. Dean of special interest. About the general habits of this fish, he thinks it unnecessary to write much, as Füileborn's notes, so recently published, are but confirmed; but we are glad that he has added some on the breeding habits, which are illustrated with sketches of the nest and of the cloud of young fry attended by the male. The author concludes that the early development must certainly be regarded as furnishing abundant evidence of intermediate characters; to the Ganoids, on the one hand, and to the Teleosts, on the other. These ontogenetic nearnesses become, accordingly, of the greatest interest, since they confirm the results of the structural study of recent and fossil forms upon the Amioid descent of Teleosts.—On Kynotus cingulatus; a new species of earthworm from Imerina in Madagascar, by W. Blaxland Benham (Plates 33 and 34). This interesting species is remarkable for the great number and small size of the segments composing the body; there were three anterior portions sent for examination, each about 225 mm. in length; each piece consisted of some three hundred or more segments; the whole worm being probably about 450 mm. to 500 mm. in length; it possesses a clitellum of relatively enormous dimensions, with most peculiar “claspers.”—Notes on the ciliation of the ectoderm of the amphibian embryo, by R. Assheton (Plate 35), describes the distribution of the cilia over the surface of the bodies of the tadpoles of Rana temporaria and Triton cristatus. As the author notes, the existence of a ciliated embryo among craniate vertebrates seems often to be overlooked.—On the ontogenetic differentiations of the ectoderm in Necturus (Study II).—On the development of the peripheral nervous system, by Julia B. Platt (Plates 36–38). Even if we assume Necturus to be a monotypic genus, it would have been advisable for the authoress to have cited a specific name for the Batrachian, whose peripheral nervous system she has so painstakingly elaborated. The summary, occupying two pages, is too long to be cited, and does not admit of being further condensed; we note that “although delicate protoplasmic prolongations connecting cell with cell initiate the specialised coordination of the nervous system, a common reticulum, such as Sedgwick describes, into which nuclei migrate, does not exist in Necturus”‘lateralis]. This number contains a title and index to Volume xxxviii.