Absorption of ascorbic acid and ascorbic sulfate and ascorbate metabolism in common carp (Cyprinus carpio L.)

Summary Ascorbate metabolism was analyzed in fasted common carp and carp offered diets lacking ascorbic acid or supplemented with ascorbic acid (AA) or ascorbic sulfate (AS). Ascorbic acid and ascorbic sulfate were analyzed in the contents collected from various parts of the digestive tract. The major site of the dietary ascorbate absorption was located in the first 20% of the anterior intestine region (58.7±10.2%), whereas absorption increased to 94.3±1.9% (in the whole gut). Considerable secretion of ascorbate into the initial part of the intestine was found (71 g AA · g^-1 dry food) in fish offered the diet lacking ascorbate, but this amount was completely reabsorbed in the following portions of the intestine. AS was concentrated in the contents of the digestive tract and the external marker method revealed no absorption of AS from the intestine. In fish fed the AA-supplemented diet, the concentration of ascorbate in plasma, hepatopancreas, kidney, intestine, spleen, and brain was significantly (P<0.01) higher than in similar tissues from the other groups, suggesting that ascorbic sulfate hydrolysis was ineffective. Small amounts of AS were found in the intestine and spleen of fish fed a diet supplemented with AS. Ascorbate analysis in the whole fish allowed the estimate of the catabolic rate of fasting and scorbutic-diet-fed fish, which amounted to 0.7% and 1.46% daily of the ascorbate body pool, respectively. There was no indication that ascorbic sulfate sulfohydrolase activity was induced in hepatic, kidney, or intestinal tissue of fish offered a diet with AS in comparison to other groups. It seems unlikely that cyprinid fish are able to utilize ascorbic sulfate as a vitamin C source, and thus resemble scurvy-prone mammals in this respect.Abbreviations AA ascorbic acid - AS ascorbic sulfate - TCA trichloroacetic acid - PCA perchloric acid - EDTA ethylenediaminetetraacetate dihydrate - DNPH dinitrophenyl hydrazine - ASS-ase ascorbic sulfate sulfohydrolase - AR-ase arylsulfatase - NCS p-nitrocatechol sulfate - DHA-rase dehydroascorbate reductase - DHA dehydroascorbic acid - GSH glutathione - G-6-Pase glucose-6-phosphate dehydrogenase - G-6-P glucose-6-phosphate     

Ultrastructure of the heart of the sturgeon Acipenser stellatus (Chondrostei)

Summary The ultrastructure of atrial and ventricular myocardial cells from Acipenser stellatus is described. The cells of the atrium are more loosely connected than those of the ventricle. Cell contact is by simple intercalated discs and by desmosomes. The cells are flattened, with peripheral myofibrils and a central region of mitochondria and the nucleus. The sarcoplasmic reticulum consists of subsarcolemmal tubules, that frequently extend towards the central mitochondria. Dyads are small and positioned at any sarcomeric level. No T-tubules are present. Specific granules are restricted to the atrial cell, and are sometimes present within the SR tubules.     

Cellular localization of somatolactin in the pars intermedia of some teleost fishes

Summary We report here on the cellular localization in the fish pituitary of somatolactin (SL), a putative new pituitary hormone related to growth hormone and prolactin, which has been recently identified in the piscine pituitary gland. Immunocytochemical staining, using anti-cod SL serum, revealed that in the cod pituitary gland, SL is produced by cells in the intermediate lobe, bordering the neural tissue. These cells, staining weakly with periodic-acid-Schiff (PAS), are distinct from the melanocyte stimulating hormone (MSH) cells which, as in all teleosts, are PAS-negative. SL-immunoreactivity was observed in the same location in all other teleost species examined: flounder, rainbow trout, killifish, molly, catfish and eel. In most fish the SL-immunoreactive cells are either strongly or weakly PAS-positive but in rainbow trout are chromophobic, indicating that the SL protein can probably exist in glycosylated and non-glycosylated forms. Thus, in demonstrating the cellular localization of SL, this study provides the first identification of the enigmatic, second cell-type of the fish pars intermedia.     

The histochemical localization of steroid binding sites in the pituitary gland of a teleost (the platyfish)

Summary Specific binding sites for estrogen, testosterone, and progesterone have been demonstrated in the pituitary gland of mature male and female platyfish (Xiphophorus maculatus). With a histochemical procedure, fluorescent-steroid-hormone conjugates were localized in the cytoplasm and nucleus of the gonadotrops of the caudal pars distalis (CPD) and in cells of the pars intermedia (PI) previously demonstrated to contain immunoreactive gonadotropin. The specificity of the response was confirmed by means of competitive binding analyses and by using fluoresceinated BSA not linked to steroids. The physiological significance of steroid binding in the PI, as well as in the CPD, is discussed in the light of other recent studies on the pituitary gland of the platyfish.     

Morphologic and genetic variability in the Barbus fishes (Teleostei,Cyprinidae) of Central Italy

Italian freshwaters are highly biodiverse, with species present including the native fishes Barbus plebejus and Barbus tyberinus that are threatened by habitat alteration, fish stocking and invasive fishes, especially European barbel Barbus barbus. In central Italy, native fluvio‐lacustrine barbels are mainly allopatric and so provide an excellent natural system to evaluate the permeability of the Apennine Mountains. Here, the morphologic and genetic distinctiveness was determined for 611 Barbus fishes collected along the Padany–Venetian (Adriatic basins; PV) and Tuscany–Latium (Tyrrhenian basins; TL) districts. Analyses of morphological traits and mitochondrial DNA sequence data explored the natural and anthropogenic factors that have shaped their distribution ranges. Over 100 alien B. barbus were recorded in the Tiber basin (TL district) and Metauro basin (PV district). Comparisons of genetic and morphometric data revealed that morphometric data could identify alien B. barbus from native Barbus, but could not differentiate between B. tyberinus and B. plebejus. Genetic analyses revealed ~50 D‐loop mtDNA haplotypes and identified a distinct Barbus lineage present only in the Vomano River at the southern boundary of PV district. Demographic expansion and molecular variance analyses revealed a lack of geographic structuring across the sampling regions. While the contemporary B. plebejus distribution has been driven primarily by anthropogenic fish translocations, the dispersal of B. tyberinus has been via natural dispersion, including their crossing of the Apennine Mountains via temporary river connectivity. The results also revealed that the Barbus fishes of the mid‐Adriatic region of Europe have a complex pattern of local endemism. To conserve these patterns of genetic uniqueness, especially in the mid‐Adriatic basins, Barbus fishes should be managed by treating them as unique evolutionary units and ceasing translocations of all Barbus fishes between river basins.     

Marine fishes (Elasmobranchii and Teleostei) from the Santana Archipelago,a Marine Protected Area in the southwestern Atlantic

The Santana Archipelago (22°23′S, 41°42′W) is located at the northern limit of the South Brazil Bight in Southeastern Brazil, a major topographic feature of the South American continental shelf relevant in terms of fisheries, biogeography and conservation. Herein, the first inventory of the ichthyofauna of the Santana Archipelago is presented, with information on the distribution and conservation status of 147 species of the Teleostei and Elasmobranchii. Sampling was performed during 15 field expeditions between March 2013 and November 2015. A total of 6931 specimens were collected using bottom trawl, beach seine, hand net and scuba diving. Records of 28 species were based on photographs, and five species were recorded through underwater sighting. The Elasmobranchii was represented by nine species in eight families and six orders, and the Teleostei by 138 species in 54 families and 26 orders. Previous records of fishes from the Archipelago consist of 18 species deposited in fish collections; therefore, 129 species are reported herein for the first time. Most (114, 77.5%) species have large geographic distributions (western Atlantic: 81 species, 55.1%; eastern and western Atlantic: 33 species, 22.4%), but seven recorded species (4.8%) are endemic to the Brazilian Province. At the Global (IUCN) level, 12 species (8.1%) are threatened with extinction. Thirteen (8.8%) species are also considered as threatened at the Regional (Brazilian) level. These results highlight the relevance of the Santana Archipelago in the Brazilian conservationist context. Possible threats to the ichtyofauna of the Archipelago are discussed, and effective measures of conservation are presented.     

Unusual gonad structure in the paedomorphic teleost Schindleria praematura(Teleostei: Gobioidei): a comparison with other gobioid fishes

The gonads of eight gobioid species were examined histologically, including Pandaka pygmaea and Schindleria praematura , in order to investigate the manifestations of miniaturization and paedomorphosis in the gonads. Rearrangements of reproductive structures were found only in S. praematura , and included only the gonad tissues, not the gametes. Both sexes of S. praematura maintain basic germinal components: the spermatocyst composed of Sertoli cells and spermatogonia in the testis and the follicle and oocyte complex in the ovary. The stromal ovarian tissue and testicular interstitial tissue, however, is reduced compared to other gobies, and the number and location of gonial cells is restricted. This sequestered pattern of gonial cells is known as a restricted spermatogonial type in the testis, and has been reported only in atherinomorphs. The restriction of gonial cells in the ovary is extremely rare among teleosts, known only from one other species. These restricted gonial patterns in S. praematura are probably related to the overall reduction of morphological complexity in this genus, due to its extreme paedomorphosis.     

Morphologic development of the adrenal cortex in squirrel monkeys (Saimiri sciureus)

This study describes the morphology of the squirrel monkey (Saimiri sciureus) adrenal gland in the perinatal period. Adrenals of fetal monkeys had a broad central zone of large eosinophilic cells (fetal zone) surrounded by a subcapsular band of small dark cells (definitive zone). Adrenals of stillborn and neonatal monkeys had a reduced fetal zone and an expanded definitive zone that was differentiated into distinct zona fasciculata and zona glomerulosa. By day 18 postpartum, no remnant of the fetal zone remained.     

Morphology of the male reproductive systems of two Indopacific blenniid fishes,Salarias fasciatus and Ecsenius bicolor (Blenniidae,Teleostei)1

The testes and associated accessory organs of two blenniid fishes are described. The testicular organs of Salarias fasciatus consist of a testicular gland adjacent to the testis, chambered seminal vesicles serving as a reservoir for spermatozoa and testicular blind ouches. Ecsenirts bicolor has no testicular gland, has elongated chambered seminal vesicles whii are not used as a reservoir for spermatozoa, and has testicular blind pouches.     

In vitro effects of crude extracts of Parkia biglobosa (Mimosaceae), Stereospermum kunthianum (Bignoniaceae) and Biophytum petersianum (Oxalidaceae) on corticosteroid secretion in rat

Previous studies conducted in guinea pig, rat and rabbit have revealed that crude extracts from Parkia biglobosa, Stereospermum kunthianum and Biophytum petersianum exert hypotensive and/or hypoglycemic activities. Since corticosteroids are involved in the control of arterial blood pressure and glycemia, we have investigated the possible effects of these plant extracts on rat adrenal tissue in vitro. Short-term administration of crude semi-ethanolic extracts of P. biglobosa and S. kunthianum to perifused rat adrenal tissue did not induce any significant changes in corticosteroid output. Conversely, the B. petersianum extract caused a dose-dependent increase in corticosterone and aldosterone secretion. Repeated infusions or prolonged administration of B. petersianum extract did not produce any apparent attenuation of the steroid response. Altogether, these data indicate that a semi-ethanolic extract of B. petersianum dose-dependently stimulates corticosterone and aldosterone secretion in rat without any desensitization phenomenon.     

The influence of diet and gastrointestinal fermentation on key enzymes of substrate utilization in marine teleost fishes

Three closely related marine teleosts with similar size, swimming mode, and habitat preference were compared to test the hypothesis that energy metabolism is linked to diet choice in the wild. Key substrate-utilization enzyme activities were assayed from white locomotory muscle and liver in a carnivore (Scorpis violaceus), an omnivore (Girella tricuspidata), and a herbivore (Kyphosus sydneyanus) collected from their natural reef habitat in northeastern New Zealand. The similar energy requirements of the study fishes were reflected in specific enzyme activities of white muscle and suggested high dependence on endogenous fuel that is independent of dietary carbohydrate intake. Clear differences were found in enzymes of hepatic carbohydrate, fat, and ketone body metabolism that appear linked to diet choice and levels of gastrointestinal fermentation. Hepatic metabolism of fat and ketone bodies was also examined in New Zealand samples of the omnivorous Girella cyanea and the herbivorous Kyphosus bigibbus, and the tropical herbivorous species Kyphosus vaigiensis and Kyphosus cinerascens collected from the Great Barrier Reef, Australia. Overall, the results suggest that, like ruminants, herbivorous fishes such as Kyphosus species that rely upon gastrointestinal fermentation preferentially use lipids as major metabolic substrates by an increased capacity for lipid metabolism, and a lower capacity for glycolysis.     

The caudal skeleton of ostariophysan fishes (Teleostei): Intraspecific variation in trichomycteridae (Siluriformes)

The different elements of the caudal skeleton of the South American catfish genera Nematogenys (Nematogenyinae) and Trichomycterus, Hatcheria, and Bullockia (Pygidiinae) (Siluriformes, Trichomycteridae) show Ontogenetic transformation of the second ural centrum in Trichomycteridae separates the subfamilies Nematogenyinae and Pygidiinae. In the former, the second ural centrum is aligned with the first ural centrum in early stages of ontogeny; it is not fused with the bases of hypurals 3 and 4 in any stage of development. In the Pygidiinae, in contrast, the second ural centrum is connected with the base of hypural 3 from an early stage of development on. One of the most noteworthy features of the Pygidiinae is the epural, a polymorphic element with three or four morphotypes that are species specific. The primitive catfish Nematogenys shows intraspecific variation in the ural centra, segmentation of procurrent caudal rays, and principal caudal ray formulae. Species of Trichomycterus, Hatcheria, and Bullockia are characterized by great intraspecific variability that involves ural centra, the epural, hypurapophyses, and the neural arches of the compound centrum. There is intraspecific variation in the fusion of the hypurals in some species of Trichomycterus. Intraspecific variation of the caudal skeleton of fishes of the family Trichomycteridae involves the presence and frequency of different morphotypes of the epural, neural arch of the compound centrum, fusion of hypurals, and principal caudal ray formulae. Ontogenetic changes of the first and second ural centra, hypurapophyses (with the exception of Nematogenys), and segmentation of procurrent caudal rays (in Nematogenys) are involved also.     

Phylogenetic analysis and taxonomy of the poecilioid fishes (Teleostei: Cyprinodontiformes)

Evidence from morphology is used to infer the phylogeny of the superfamily Poecilioidea using other cyprinodontoid fishes as outgroups. The three equally most parsimonious trees resulting from the phylogenetic analysis support the monophyly of the families Anablepidae and Poeciliidae with respect to each other, but the previous taxonomy within the Poeciliinae is not consistent with the resultant phylogenetic trees. The Poeciliidae is recognized with three subfamilies: the Aplocheilichthyinae containing solely Aplocheilichthys spilauchen , the Procatopodinae containing Fluviphylax (Fluviphylacini) and the African lamp-eyed killifishes (Procatopodini), and the Poeciliinae. The inferred hierarchical relationships of included suprageneric taxa are: ((Oxyzygonectinae, Anablepinae) (Aplocheilichthyinae ((Fluviphylacini, Procatopodini) (Alfarini (Priapellini (Gambusini (Heterandrini (Cnesterodontini (Girardini, Poeciliini))))))))). The tribe Alfarini is resurrected and a new tribe, the Priapellini, is described. Tomeurus gracilis is not the most basal poeciliine, and facultative viviparity in Tomeurus is not a plesiomorphic intermediate condition of viviparity retained from the common ancestor of poeciliines. Facultative viviparity in Tomeurus is the result of an evolutionary loss of obligate viviparity. Tomeurus gracilis is recognized as a member of the tribe Cnesterodontini. Lamprichthys tanganicus and Micropanchax pelagicus are not sister taxa, and the pelagic lacustrine habits of these two species are inferred to have evolved independently. Based on the principles of vicariance biogeography, the origin of the Poecilioidea is inferred to have occurred before the separation of Africa and South America.     

Tempo of hybrid inviability in centrarchid fishes (Teleostei: Centrarchidae)

Hybrid viability decreases with divergence time, a pattern consistent with a so-called speciation clock. However, the actual rate at which this clock ticks is poorly known. Most speciation-clock studies have used genetic divergence as a proxy for time, adopting a molecular clock and often far-distant calibration points to convert genetic distances into age. Because molecular clock assumptions are violated for most genetic datasets and distant calibrations are of questionable utility, the actual rate at which reproductive isolation evolves may be substantially different than current estimates suggest. We provide a robust measure of the tempo at which hybrid viability declines with divergence time in a clade of freshwater fishes (Centrarchidae). This incompatibility clock is distinct from a speciation clock because speciation events in centrarchids appear to be driven largely by prezygotic isolation. Our analyses used divergence times estimated with penalized likelihood applied to a phylogeny derived from seven gene regions and calibrated with six centrarchid fossils. We found that hybrid embryo viability declined at mean rate of 3.13% per million years, slower than in most other taxa investigated to date. Despite measurement error in both molecular estimated ages and hatching success of hybrid crosses, divergence time explained between 73% and 90% of the variation in hybrid viability among nodes. This high correlation is consistent with the gradual accumulation of many genetic incompatibilities of small effect. Hybrid viability declined with the square of time, consistent with an increasing rate of accumulation of incompatibilities between divergent genomes (the snowball effect). However, the quadratic slope is due to a lag phase resulting from heterosis among young species pairs, a phenomenon rarely considered in predictions of hybrid fitness. Finally, we found that reciprocal crosses often show asymmetrical hybrid viabilities. We discuss several alternative explanations for this result including possible deleterious cytonuclear interactions. Speciation-clock studies have been a small cottage industry recently, but there are still novel insights to be gained from analyses of more taxonomic groups. However, between-group comparisons require more careful molecular-clock calibration than has been the norm.     

Species delimitation in Neotropical fishes of the genus Characidium (Teleostei,Characiformes)

Neotropical darters of the genus Characidium have a complex systematic history with several examples of sympatry throughout their distribution range in Neotropical freshwaters. Although various species within the genus have been used as models to investigate chromosomal evolution and biogeography, species boundaries and relationships still remain uncertain. Here, we use mitochondrial DNA sequences to perform species delimitation analyses within Characidium and test previous hypotheses of species richness within the Characidium zebra complex and among sympatric morphotypes of C. alipioi. Results indicate high genetic distances within tested species complexes and revealed the presence of strongly supported lineages such as the large C. lauroi group from southeastern Brazil. This suggests that the evolutionary history of these groups may be correlated with biogeographic history. Analyses also reveal that three geographically isolated populations of C. zebra represent a single species, leading us to reject prior hypothesis of multiple species. Species delimitation using mitochondrial data strongly supports the presence of two sympatric species within C. alipioi in southeastern Brazil despite limited morphological variation and conserved chromosomal patterns. These results provide a framework to further the study of systematics and evolution within Characidium.     

Environmental determination of sex in Apistogrammai (Cichlidae) and two other freshwater fishes (Teleostei)

Environmental sex determination by temperature could be revealed significantly in 33 Apistogramma-species and in Poecilia melanogaster . In some, but not all, Apistogramma-species pH also influences the sex ratio, whereas neither temperature nor pH affect the sex ratio of Pseudocrenilabrus multicolor victoriae . The sex in offspring of A. trifasciata is determined within a sensitive period of about 30 to at least 40 days after spawning.     

Conus-like structure in the eye of the deep-sea teleost Radiicephalus elongatus (Pisces,Teleostei)

Summary A conus-like structure, the hyaloid conus, located on the optic nerve head of the mesopelagic deep-sea teleost Radiicephalus elongatus is described. The hyaloid conus consists of a tapering sheath of unpigmented, vascularized connective tissue enveloping the proximal part of the hyaloid artery which proceeds from the optic nerve head through the vitreous body to the ventrally located falciform process and lens muscles. The hyaloid artery passes through the hyaloid conus without giving off any branches. The conus vessels encircling the hyaloid artery receive arterial blood from the choroid via small arteries and are drained to the choroid by a single vein. The hyaloid conus is compared with the lacertilian conus papillaris. The function of the hyaloid conus is unknown. Because of its small dimensions relative to those of the eyeball and its few capillaries, it is unlikely that the hyaloid conus is a supplemental nutritive device for the retina.