bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact of γ‐hexachlorocyclohexane exposure on plasma gonadotropin levels and in vitro stimulation of gonadal steroid production by carp hypophyseal homogenate in Carassius auratus
Authors: Singh P. B. , Kime D. E. , Epler P. , Chyb J.
Published: April 2005

Male and female Carassius auratus were exposed to safe (SC; 0.01 ppm) and sublethal (SL; 0·1 ppm) concentrations of an organochlorine pesticide γ‐hexachlorocyclohexane (γ‐HCH) for 4 weeks during the pre‐spawning phase (June) of the annual reproductive cycle. Gonadosomatic index and gonadotropin levels were significantly lower after exposure to both γ‐HCH concentrations than in control fish. After 4 weeks exposure, gonadal tissue from control, SC and SL exposed fish was incubated with carp hypophyseal homogenate (chh). The chh stimulated production of testosterone, 17,20β‐dihydroxy‐4‐pregnen‐3‐one (17,20βP), 11‐deoxycortisol, and 11‐ketotesterone (11‐KT) was estimated in the unconjugated (free) and conjugated (glucuronide) fractions by radioimmunoassay. In both sexes, testosterone production was greatly decreased in γ‐HCH exposed fish compared to controls. 17,20βP production was low in all fish and was unaffected by γ‐HCH. Free 11‐deoxycortisol production by testicular fragments was higher in SL and SC compared with controls, while conjugated 11‐deoxycortisol was increased only higher in the SL. In ovarian fragments from exposed fish, free 11‐deoxycortisol decreased while glucuronide concentrations increased compared with controls. 11‐KT production was significantly decreased in testicular fragments of exposed fish. The results indicate that γ‐HCH inhibits gonadal recrudescence by decreasing both gonadotropin secretion and its potential for stimulation of steroidogenesis.
Population structure, reproduction and sex‐change in a tropical East Atlantic grouper
Authors: Siau Y.
Published: April 2005

Spawning time and sizes at first sexual maturity and at sex‐reversal are described in the tropical blue‐spotted grouper Cephalopholis taeniops. All juvenile fish possess non‐functional ovaries. At sexual maturity, most juvenile fish become functional females. Some of these later change sex to become males. The remaining juvenile females change immediately to males, without time as functional females. This is a new scheme for sexual differentiation of groupers.
A comparison of genetic diversity levels in marine, freshwater, and anadromous fishes
Authors: Ward R. D. , Woodwark M. , Skibinski D. O. F.
Published: April 2005

Electrophoretic data were analysed from 49 species of freshwater fish, 57 species of marine fish, and seven anadromous species. For each species, at least 15 individuals had been assayed for at least 15 loci in two or more subpopulations. The results showed that while average total heterozygosity (H̄T) was approximately equal in freshwater and marine species (0·062 and 0·064 respectively), subpopulation heterozygosity (H̄s) was significantly less in the former group (0·046 and 0·059 respectively). Consequently the average degree of genetic subpopulation differentiation (H̄ST) was significantly greater for freshwater species (0·222 v. 0·062). On average, it is likely that marine subpopulations exchange between 10 and 100 times more migrants per generation than freshwater subpopulations, presumably because of the relative absence of barriers to dispersal in the marine environment. The reduced values of Hs in freshwater species are likely to reflect reduced effective subpopulation sizes relative to marine species. The few andromous species that have been analysed show intermediate levels of GST.
Morphometry of some structural parameters affecting oxgyen diffusion in body trunk red muscle at different sizes of a tilapia, Oreochromis niloticus
Authors: Kisia S. M. , Hughes G. M.
Published: April 2005

Morphometric measurements were carried out on some of the structural parameters affecting oxygen diffusing capacity in red muscle of 15 specimens of O. niloticus body weight (b.w.) 0.65–812.3 g. Total capillary length and surface area and total morphometric oxygen diffusing capacity in body trunk red muscle had average values of 4792·7 (± 1740.7 s.e.) m, 415·4 (± 157·3 s.e.) cm2 and 0·0213 (± 0·0075 s.e.) ml−1 min−1 cm−2 mmHg respectively. When expressed as functions of b.w. these parameters had scaling values of 1·02, 1·07 and 0·993 respectively. These figures show a slight increase or almost no change in these structural parameters (which affect diffusion of oxygen to mitochondria in red muscle) per unit weight of fish. This should be important as the role of sustained swimming (by red muscle) becomes more important in larger tilapia. Oxygen diffusion distances were short [3·11 (±0·16 s.e.) μm] which facilitates diffusion of oxygen to mitochondria. The scaling value for oxygen diffusion distances of 0·067 (with respect to body weight) shows a slight increase in this parameter with development. This value is significantly different from zero.
Development of serotonergic neurons in the brain of the mackerel, Scomber scombrus. An immunohistochemical study
Authors: Bolliet V. , Perreault S. , Ali M. A.
Published: April 2005

The ontogenetic development of serotonin immunoreactivity (5‐HTir) neurons was investigated by immunocytochemistry in the brain of the mackerel, from fertilization to the complete resorption of the yolk sac (201 h). 5‐HTir appears first in cell bodies in the diencephalon, on both sides of the third ventricle. At hatching time 5‐HTir perikarya are also present in the mesencephalon and the inferior raphe but in small numbers. During larval stages, immunoreactivity appears consecutively in the area thalamo piaetectalis, the nuclei raphe pallidus and obscurus, the nuclei tegmenti dorsalis lateralis, recessus posterioris, lateralis hypothalami and paragigantocellularis lateralis. These results, together with previous findings, suggest a common pattern of distribution of the different 5‐HTir neuronal populations in the brain of a teleost during ontogeny but a different sequence of appearance of initial 5‐HTir in these populations between species.
Histological changes in starved turbot larvae (Scophthalmus maximus) quantified by digital image analysis
Authors: McFadzen I. R. B. , Lowe D. M. , Coombs S. H.
Published: April 2005

In turbot larvae, Scophthalmus maximus, deprived of food for 24 h there was a significant increase in the specific surface of the epithelium and the corresponding microvillous border of the foregut accompanied by slight cellular degeneration. Following 48 h starvation Sarvae showed severe tissue degeneration in the foregut mucosa, progressing to extensive mucosal desquamation and cellular sloughing. Intracellular vacuolation of the epithelium and loss of microvilli was also extensive and the ability of the gut to absorb food must be severely impaired, with further starvation probably resulting in larval death. There was no evidence of parasitic infection in any of the larvae sampled and all observed alterations are attributable to food deprivation.
The role of experience and chemical alarm signalling in predator recognition by fathead minnows, Pimephales promelas
Authors: Chivers D. P. , Smith R. J. F.
Published: April 2005

Young‐of‐the‐year, predator‐naive fathead minnows, Pimephales promelas, from a pikesympatric population did not respond to chemical stimuli from northern pike, Esox Indus, while wild‐caught fish of the same age and size did. These results suggest that chemical predator recognition is a result of previous experience and not genetic factors, Wild young‐of‐the‐year minnows responded to pike odour with a response intensity that was similar to that of older fish, demonstrating that the ability to recognize predators is learned within the first year. The intensity of response of wild minnows which had been maintained in a predator free environment for 1 year was similar to that of recently caught minnows of the same age, suggesting that reinforcement was not required for predator recognition to be retained. Naive minnows that were exposed simultaneously to chemical stimuli from pike (a neutral stimulus) and minnow alarm substance exhibited a fright response upon subsequent exposure to the pike stimulus alone. Predator‐naive minnows exposed simultaneously to chemical stimuli from pike and glass‐distilled water did not exhibit a fright response to the pike stimulus alone. These results demonstrate that fathead minnows can acquire predator recognition through releaserinduced recognition learning, thus confirming a known mechanism through which alarm substance may benefit the receivers of an alarm signal.
Homologous growth hormone (GH) binding in gilthead sea bream (Sparus aurata). Effect of fasting and refeeding on hepatic GH‐binding and plasma somatomedin‐like immunoreactivity
Authors: Pérez‐Sánchez J. , Martí‐Palanca H. , Le Bail P‐Y.
Published: April 2005

Specific binding of gilthead sea bream growth hormone (sbGH) to liver membrane preparations was a time and temperature dependent process, and was saturable by increasing amounts of membrane proteins. Scatchard analysis evidenced a single class of high‐affinity and lowcapacity binding sites. Ovine prolactin, recombinant tilapia prolactin, carp gonadotropin and chinook salmon gonadotropin did not compete for the125I‐sbGH binding sites, while recombinant trout GH, bovine GH and human GH displaced iodinated sbGH in a dose dependent‐manner. IGF‐I‐like immunoreactivity was detected after acidification of plasma and removal of IGF‐I binding activity. A parallel displacement to the rhIGF‐1 standard was observed with extracted plasma samples. Free and total hepatic GH‐binding decreased during long‐term starvation (3–9 weeks), returning to control values during the refeeding period. Plasma IGF‐I‐like immunoreactivity showed a similar trend. To our knowledge, this is the first report that indicates a coordinated regulation of GH‐binding and plasma somatomedin‐like activity in a typical marine fish.
A study of the mechanism of algal uptake in yolk‐sac larvae of Atlantic halibut (Hippoglossus hippoglossus)
Authors: Reitan K. I. , Bolla S. , Olsen Y.
Published: April 2005

The drinking rate of water, and the ingestion‐ and assimilation rates of algae in yolk‐sac larvae of Atlantic halibut were examined by use of3H‐dextran and14C‐labelled algae. The drinking rate throughout the yolk‐sac stage was in the range of 7–160 nl per larva h−1, with a slight increase towards the end of the period. The ingestion rate of algae (Tetraselmis sp.) was very low before day 30 and showed a peak between day 43 and 48 at 5° C. The assimilation efficiency of the algae was in the range of 1‐5%. The clearance rate of algae was 100–1000 times higher than the drinking rate, and was correlated to the distance between the gill arches. Bigger cells were more effectively retained than smaller ones. The results suggested that the larvae acted as filter feeders from day 30 up to the point when they are expected to start feeding on bigger prey.
Temperature‐induced changes of early development and yolk utilization in the African catfish Clarias gariepinus
Authors: Kamler E. , Szlamińska M. , Kuczyński M. , Hamáčková J. , Kouřil J. , Dabrowski R.
Published: April 2005

Artificially fertilized eggs and yolk‐sac larvae of a freshwater tropical/subtropical fish Clarias gariepinus receiving no external food were incubated at 22, 25 and 28° C until full yolk resorption. Developmental time, size and matter composition (CHNS‐O Analyzer and ashing) were assessed at egg fertilization, hatching and yolk resorption; respiration was measured every 4–5 h. The course of acceleration of C. gariepinus embryonic developmental rate with temperature (Q10dev) was compared over the temperature range to those of Cyprinus carpio and Oncorhynchus mykiss; they differed greatly, but were similar when compared on the basis of effective temperatures specific to each fish. Specific growth rates for energy (88, 150 and 183% per day at 22,25 and 28° C, respectively) as well as the conversion efficiencies of egg energy (64, 71 and 68%, respectively) and protein (71, 78 and 76%, respectively) in C. gariepinus larval tissues were higher than those known for the endogenous feeding period of coldwater and temperate fish species. In C. gariepinus at the end of yolk resorption, the carbon percentage and caloric values of dry weight, size (in terms of dry matter, minerals, protein and energy per larva) and transformation efficiencies were lowest at 22° C, highest at 25° C and had slightly decreased at 28° C. A tentative mechanism which leads to the positive or negative response of body size to temperature over the viable temperature range is defined.
Effect of ration size on growth and gross conversion efficiency of young lemon sharks, Negaprion brevirostris
Authors: Cortes E. , Gruber S. H.
Published: April 2005

Young lemon sharks, Negaprion brevirostris, were kept under controlled conditions in an aquarium and fed blue runner, Caranx crysos, at different ration levels. The relationship between feeding rate and growth rate was best described by a von Bertalanffy growth curve, which predicted a maximum growth rate of 140 kJ kg−1 day−1 (0·66% b.w. day−1), a maintenance ration of 199 kJ kg−1 day−1 (1·06% b.w. day−1), and losses due to starvation of ‐236kJ kg−1 day−1 (1·11% b.w. day−1). The relationship between gross conversion efficiency (K1) and feeding rate was also examined. K1 ranged from ‐ 64 to 25% and did not drop at high ration levels. Activity levels of both starved sharks and sharks fed at maintenance were not significantly different (0·2 body lengths s−1). K1 values generated from both laboratory and field data suggest that young lemon sharks can convert food to new tissue as efficiently as teleosts.
Reproductive investment of female brown trout, Salmo trutta L., in a stream and reservoir system in northern England
Authors: Crisp D. T.
Published: April 2005

Within the basin of Cow Green reservoir, upper Teesdale, the brown trout, Salmo trutta L., spend their first two seasons in running water. After this some females remain resident and others migrate to Cow Green reservoir. A cohort of 1000 females at age 2 that remains resident in tributary streams will, during the lifetime of the cohort, lay, on average, 3·0 times as many eggs as a cohort which resides in the reservoir. This conclusion is apparently not consistent with the observation that most females take up reservoir residence.

Reservoir females have a higher growth rate (Walford constant k=0·61, c.f. 0·86 for stream residents) and shorter life expectancy (M year−1= 1·19, c.f. 0·56) than the stream residents. However, they are of larger average size than the stream residents, lay larger eggs (mean 0·074 g, c.f. 0·066 g) and bury them more deeply (mean depth 11·0 cm, c.f. 8·5 cm).
Fish species found in the rocky sublittoral during winter months as revealed by the underwater application of the anaesthetic quinaldine
Authors: Sayer M. D. J. , Cameron K. S. , Wilkinson G.
Published: April 2005

Using the anaesthetic quinaldine applied underwater, fish species not normally observed in the Scottish rocky sublittoral during the winter months have been recorded, and are listed.
The karyotype of the dab (Limanda limanda L.)
Authors: Di Shaojie , Knowles J. F.
Published: April 2005

In the dab (Limanda limanda L.), the diploid number is 46 and the karyotype consists of 23 pairs of chromosomes, all of which are telocentric or subtelocentric, so that the total number of chromosome arms is 46 (AN‐46).
Egg size and larval development in Central Amazonian fish
Authors: Araujo‐Lima C. A. R. M.
Published: April 2005

The relationship between larval development and egg size was studied in 14 species of Central Amazonian fish (seven characiforms, five cichlids and two siluriforms). Egg size was measured as yolk dry weight at activation (egg minus chorion). Larval development was measured as larva] dry weight and age (h from activation) at the developmental stages. Egg size explained most of the variability of larval body weight and total larval weight at hatching, pectoral bud formation, eye pigmentation, jaw formation, swimbladder inflation, onset of swimming, first feeding and maximum weight attained with exclusively endogenous feeding. Larval ages at these developmental stages were poorly related to egg size. Other variables, such as the weight‐specific yolk caloric content of the eggs (cal mg−1), spawning site (river or lake) and phyletic relationships had no effect on the remaining variance. These results suggest that the developmental stages considered were conservative among the species examined and that a sequence of stages occurs in the larval development of Amazonian larval fish. The resistance of the larvae to starvation was not related to egg size.
Digestion of algae by Stegastes nigricans and Amphiprion akindynos (Pisces: Pomacentridae), with an evaluation of methods used in digestibility studies
Authors: Galetto M. J. , Bellwood D. R.
Published: April 2005

An investigation of the digestive physiology of two species of damselfish (family Pomacentridae) was undertaken, comparing a herbivore Stegastes nigricans with an omnivore/ planktivore Amphiprion akindynos. Apparent digestibility of Enteromorpha flexuosa (Chlorophyta) was calculated using both total collection and a range of ash‐marker methods. In addition, Van Soest's system of fibre analysis was used to determine the digestibility of algal cell walls. A comparison of total collection methods (comparing food intake v. faeces output) with ash‐marker methods showed that the calculated digestibility estimate will depend on the method used. Total dry matter digestibilities varied from 75 to 20% for S. nigricans and from 79 to 15% for A. akindynos. Comparable ranges were obtained for organic matter, cell wall, nitrogen and soluble carbohydrate. Digestibility estimates calculated using total collection methods were larger and less variable than estimates calculated using ash‐marker methods. Despite major methodological variation, there was no significant difference in the digestibility of algae between the two species.
Molecular cloning and characterization of complementary DNA encoding for the gonadotropin α‐subunit of yellowfin porgy (Acanthopagrus latus)
Authors: Tsai Huai‐Jen , Chen Yen‐Long
Published: April 2005

Recombinant phage clones containing the complementary DNA (cDNA) coding for the a‐subunit of gonadotropin (GTH) were isolated from a pituitary gland cDNA library of yellowfin porgy (Acanthopagrus latus) by using a degenerate oligonucleotide based on the conserved amino acids sequence of GTH from other species as a probe. This section of 735 base pairs (bp) cDNA contained a 351 bp open reading frame with 20 bp and 345 bp flanking regions at the 5′‐ and 3′‐ends, respectively. The deduced amino acid sequence revealed a 23 amino acid signal peptide and a 94 amino acid mature α‐subunit of GTH polypeptide. The latter polypeptide showed 66, 62 and 61% amino acid identity with chum salmon, pike eel and carp GTH peptide hormone α‐subunit, respectively.
Isozyme genetics and the phytogeny of Italian freshwater gobies (Teleostei: Gobioidei)
Authors: Miller P. J. , Serventi M. , Soregaroli D. , Torricelli P. , Gandolfi G.
Published: April 2005

Although predominantly a marine group in the Atlantic/Mediterranean fish fauna, three species of exclusively freshwater gobies (Teleostei: Gobiidae) occur in Italy. These are Padogobius marltmsii of north Italy and parts of Croatia, P. nigricans from the Tyrrhenian catchment area of Tuscany and Lazio, and Knipowitschia punctatissima from north‐eastern Italy. Using horizontal starch‐gel electrophoresis, isozyme polymorphism in 12 enzymes encoded at 18 loci was investigated in these species and related euryhaline forms. Genetic distance, and morphological cladistic analysis, indicates that the Italian freshwater gobies do not form a monophyletic group, with the Padogobius species well separated from other taxa, and K. punctalissima closest to its morphological congener, the lagoonal K. panizzae. No close correlation was found between genetic variation and environmental heterogeneity.
Relative ventricular weight of wild Atlantic salmon parr in relation to sex, gonad maturation and migratory activity
Authors: Armstrong J. D. , West C. L.
Published: April 2005

Relative ventricular weight (RVW, ventricular weight/body weight · 100) was measured for five groups of Atlantic salmon parr from the Girnock Burn in Scotland. The mean RVW was: mature males, 0.087; immature resident males, 0.054; immature resident females, 0.056; immature migrant males, 0.056; immature migrant females, 0.053. For a group of mature male parr from the R. Nith, Galloway, Scotland, the mean RVW was 0.108. There were no significant differences in the RVW between groups of immature fish. The RVW of each group of mature male parr was significantly greater than those of each, group of immature parr. Condition indices (weight/length3) were closely similar between all groups of parr. The functional significance of plasticity in ventricular weight is discussed in relation to life histories of Atlantic salmon.
Influence of ontogenetic changes in prey selection on the survival and growth of rohu, Labeo rohita and singhi, Heteropneustes fossilis larvae
Authors: Mookerji N. , Rao T. Ramakrishna
Published: April 2005

When offered a mixed diet of different zooplanktonic items covering a body size range of 75–2200 μm, (a) rohu, Labeo rohita and (b) singhi, Heteropneustes fossilis larvae ingested progressively larger prey as they grew, due to age‐related increase in gape. However, a nearly constant prey size/mouth size ratio was maintained for a period of 4wk after hatching. The dominance of rotifers in the diet during the first 2‐wk was followed by cladocerans, particularly Moina macrocopa. Significant differences observed in the growth rates of the larvae reared on different diet regimes were related to ontogenetic changes in prey selection. An exclusive copepod diet throughout resulted in the lowest weight gain in the larvae of both species. However, copepods had no apparent adverse effects when present with the preferred rotifers and cladocerans. Although constituting a suboptimal prey size for the older larvae, rotifers alone, when present in sufficient densities, produced growth rates comparable to those obtained on a cladoceran diet. However, a mixed diet regime contributed to the maximum growth. The implications of these findings to rearing larvae of the economically important rohu and singhi are discussed.
Histopathology, blood chemistry, and physiological status of normal and moribund striped bass (Morone saxatilis) involved in summer mortality (’die‐off‘) in the Sacramento‐San Joaquin Delta of California
Authors: Young G. , Brown C. L. , Nishioka R. S. , Folmar L. C. , Andrews M. , Cashman J. R. , Bern H. A.
Published: April 2005

Summer mortality (’die‐off‘) is common in striped bass, Morone saxatilis (Walbaum), in the San Francisco Bay‐Delta region. Tissue and blood samples of moribund and healthy striped bass collected during the summers of 1986–1988 were analysed. Sixteen moribund and 25 healthy reference fish from the Carquinez Strait area and eight fish caught in the Pacific Ocean were studied. Moribund fish plasma was invariably yellow‐orange; most of the moribund fish had discoloured livers with haemorrhagic regions, and approximately one‐third had haemorrhagic intestines. Piasma levels of aspartale aminotransferase, uric acid, alkaline phosphatase and cortisol were significantly higher than in reference fish from Carquinez Strait and the Pacific Ocean, whereas cholesterol, sodium, chloride, triiodothyronine and glucose levels were significantly lower. Hepatic heavy metal concentrations and bacterial content were similar in moribund and reference fish. Gill Na.+, K+ ‐ATPase activity was significantly lower in moribund fish. Liver, kidney, intestine, and thyroid follicles of moribund fish displayed various histopathological changes, and corticosteroidogenic (interrenal) tissue could not be identified positively in moribund fish. These findings are discussed in relation to recent work on the chemical burdens (industrial and agricultural hydrocarbons) found in livers from some of the fish examined in this study.
Allozyme differentiation within and between red drum (Sciaenops ocellatus) from the Gulf of Mexico and Atlantic Ocean
Authors: Gold J. R. , King T. L. , Richardson L. R. , Bohlmeyer D. A. , Matlock G. C.
Published: April 2005

Nine polymorphic nuclear‐gene (allozyme) loci were surveyed among 491 red drum (Sciaenops ocellatus) sampled in 1988 and 1989 from nearshore localities in the northern Gulf of Mexico (Gulf) and the Atlantic coast of the southeastern United States (Atlantic). Data were combined with those from a previous study to generate a data set of 762 individuals representing 11 sample localities in the Gulf and 175 individuals representing five sample localities in the Atlantic. The combined data set included individuals from the 1986 and 1987 year classes and permitted rigorous testing of both temporal and spatial genetic heterogeneity. Average heterozygosity‐per‐locus values (estimated using 33 assumed monomorphic loci) were 0·048 (Gulf red drum) and 0·046 (Atlantic red drum). Tests of heterogeneity in allele frequencies between year classes at individual localities and across regions (Gulf and Atlantic) were non‐significant. Tests of spatial (geographic) heterogeneity indicated that red drum are weakly subdivided: genetically‐differentiated subpopulations occur in the northern Gulf and along the south‐eastern Atlantic coast. Genetic data were consistent with the hypothesis that red drum within the Gulf and along the Atlantic coast comprise singie subpopulalions. Genetic differences between Gulf and Atlantic red drum seem likeiy to stem from historical or recent interactions between dispersal and impediments to gene flow.
Digestion of zooplankton in the alimentary tract of vendace (Coregonus albula) larvae
Authors: Sutela T. , Huusko A.
Published: April 2005

The degradation of zooplankton eaten by vendace larvae was investigated by cutting their tubiform alimentary tract into four quarters and analysing the contents separately. Soft‐bodied rotifers were found to degrade and become indistinguishable in the anterior part of the alimentary tract, while cladocerans and copepods could still be identified in the posterior part. Assessing the diet of a larva on the basis of its whole alimentary tract contents was found to give biased results. More reliable estimates of the proportions of zooplankton taxa in the diet could be achieved from the first quarter of the alimentary tract.
Comparative allometric growth of the gastrointestinal tract of two sympatric congeners, copper rockfish (Sebastes caurinus) and quillback rockfish (S. maliger)
Authors: Murie D. J.
Published: April 2005

Allometric growth of the stomach, intestine, and caeca was compared between two sympatric congeners, the copper rockfish (Sebastes caurinus) and the quillback rockfish (S. maliger), to examine the species‐specific differences in their gut tract in relation to their general feeding habits. The intestine of copper rockfish was shorter and its mass less than the intestine of quillback rockfish. Copper rockfish also had a greater stomach mass and, on average, a greater number of pyloric caeca than quillback rockfish. The differences in the gut allometry between the species were consistent with differences in their general food habits as copper rockfish consume proportionally more fish and larger crustaceans than quillback rockfish.
Comparative studies on the feeding selectivity of silver carpHypophthalmichthys molitrixand bighead carpAristichthys nobilis
Authors: Dong Shuanglin , Li Deshang
Published: April 2005

Silver carp and bighead carp exhibited size‐selection for food particles in aquarium experiments, but did not select their preferred species of plankton actively when they were distributed evenly in the water. They also possessed the capacity of selection for feeding area. The removal rates (% g−1fish weight) of silver carp for smaller plankton (phytoplankton) were higher than those of bighead carp. The removal rates by the latter for bigger plankton (zooplankton) were higher than those of silver carp, but for plankton about 70 μm dia. the rates by the two species were almost equal.
Genetic variation and population subdivision of the endangered Iberian cyprinid Chondrostoma lusitanicum
Authors: Alves M. J. , Coelho M. M.
Published: April 2005

Products of 24 presumptive enzyme loci were used to analyse the consequences on genetic structure and variation of the Chondrostoma lusitanicum population decline within the Tejo basin. This rare cyprinid is endemic to the Iberian Peninsula and has a very restricted distribution. Five samples from the Tejo catchment were compared with a sample from a small basin, the Samarra, that has not suffered obvious anthropogenic pressures and where the fish is still abundant. Heterozygosity and polymorphism were higher overall in the Samarra. Several lines of evidence indicate a high degree of population subdivision within the Tejo basin. In fact, about half of the total gene diversity detected in the Tejo population was due to differences among samples. This differentiation appeared to be caused by genetic drift and possibly differential local selection, coupled with reduced gene flow among localities. The accelerated process of habitat degradation occurring in the lowland streams of the Tejo basin will lead to the inevitable reduction of intraspecies genetic diversity.
The largemouth bass cytochrome b gene
Authors: Whitmore D. H. , Thai T. H. , Craft C. M.
Published: April 2005

The cytochrome b gene is one of the protein‐coding genes of the mitochondrial genome that has gained importance because of the ease with which molecular techniques can be applied to the analysis of its structure. The nucleotide sequence of the largemouth bass (Microplerus salmoides) cytochrome b gene was determined and the inferred amino acid structure is presented in the form of a structural model derived originally from rat cytochrome b. The inferred amino acid sequences from divergent animal species are aligned and compared in the context of this model. The data suggest that regions of the gene may be evolving at different rates due to different selection pressures associated with functional constraints. Conserved and variable regions of cytochrome b have been identified and can be targeted for species identification, the examination of intraspeciflc variation, and phylogenetic reconstructions in future research.
Trophic interrelations in a beach seine fishery from the northwestern coast of the Yucatan peninsula, Mexico
Authors: Vega‐Cendejas M. E. , Hernandez M. , Arreguin‐Sanchez F.
Published: April 2005

The main trophic interrelations were analysed in 12 species which represent 93% of the total catch from a beach seine fishery developed in Celestún, Yucatán. The diet was determined based on monthly samples over 4 yr. Five different trophic guilds were found on the basis of feeding preferences: microcrustacean and polychaete feeders, piscivores, omnivores and herbivores. For microcrustacean feeders Orthopristis chrysoptera, Eucinostomus gula, E. argenteus and Opisthonema oglinum the diet is narrow with a large overlap between. For polychaete feeders, Arius felis, A. melanopus and Haemulon plumieri diet is broad with the higher overlap between the catfishes. Among piscivores, Bardiella chrysura and Harengula jaguana have a high overlap between them, but a lower one with other species from the community. Among omnivores Lagodon rhomboides has the broadest diet and is considered to be a generalist while Acanthostraceon quadricornis is a specialist having a very narrow diet and a lower value of overlap with the other species. Finally, Archosargus rhomboidalis is a herbivore with the narrowest niche breadth and lowest overlap. In addition to a description of diets and trophic inter‐relations, the results emphasize the importance to the beach seine fishery of the benthic food resources.
Histological study on the oocyte filaments of the silverside Odonthestes bonariensis
Authors: Guandalini E. , Mantovani A. , Fazzi P. , Gelosi E. , Colombari P. T. , Mazzini M. , Fausto A. M.
Published: April 2005

Highly developed adhesive structures are characteristic of the eggs of Odonthestes bonariensis. At spawning each egg is connected to the other ones by four to six filaments. These are extroverted only in mature eggs, about 4–5 mm long and 10μm thick, starting from coneshaped bases at the egg's surface. Histologically, no filaments are detectable during the primary growth phase of the oocytes. At the lipidic vesicle stage, rounded eosinophilic filaments appear at the cell's surface. During the following stages they increase in volume and length, running along the whole oocyte, and lose their eosinophily. The filaments are beneath the follicular cells; according to preliminary TEM observations, they derive from the zona radiata. When the oocyte is mature, the theca externa disintegrates, freeing the filaments. These rather conspicuous and complex structures are markedly different from the adhesive egg fibrils observed in other teleosts.
Biochemical genetic evidence for a hybrid origin of spined loach, Cobitis taenia taenia, in Japan
Authors: Sezaki K. , Watabe S. , Ochiai Y. , Hashimoto K.
Published: April 2005

Starch gel electrophoresis and isoelectric focusing were performed on sarcoplasmic proteins from three taxa of cobitid fish in Japan, Cobitis biwae, C. taenia striata and C. l. taenia. These taxa are hardly distinguishable from each other by external appearance or morphological characters. Electrophoretic patterns of sarcoplasmic proteins from white muscle suggested fixed allelic differences between C. biwae and C. t. striata at two protein‐coding loci (parvalbumin and creatine kinase). The third taxon, C. t. taenia, showed composite banding patterns with respect to the above two proteins, suggesting C. t, taenia originated from hybridization between C. biwae and C, t. striata. Previously, C. t, taenia and C. t. striata were believed to have shared a common ancestor subsequent to their divergence from C. biwae.
The use of body water, sodium, potassium and calcium content to investigate the nutritional status of first year Atlantic salmon parr in two Scottish Highland streams
Authors: Shackley P. E. , Talbot C. , Cowan A. , Watt A.
Published: April 2005

Water content of Atlantic salmon parr fell from about 84% at emergence (late May) to just under 79% in September but rose again towards March. Na+ content consequently rose from 3·3 mg g−1 dry wt at the beginning of June to 6·2 mg g−1 in early July. It then fell to 4·4 mg g−1 in September, rising again towards March. K+ content rose to a maximum in July to stabilize at 16·6 mg g−1 dry wt in September. The resultant Na+/K+ ratio peaked at 0·43: 1 in mid‐June, falling to a minimum in mid‐August but rising again in March reflecting changes in the relative proportions of intra and extracellular water. The changes in whole‐body chemistry suggest a period of nutritional stress immediately after emergence and during the winter. In streams at higher altitude and of lower nutrient status, nutritional stress during the winter appears to be more severe.
A method for measuring oxygen consumption in isolated perfused gills
Authors: Lyndon A. R.
Published: April 2005

A method is described for measuring respiration in isolated perfused flounder gills experiencing pressures and flows similar to those seen in vivo. Mean oxygen consumption of 13 preparations bathed and perfused in identical saline was 5·00 ± 0·75 (s.e.) μ mol h−1 g wet−1, whilst that of five preparations perfused with saline but bathed in sea water (32 mg l−1) was 12·06±2·39 (s.e.) μmol h−1 g wet−1. The oxygen consumption of the seawater bathed gills was significantly higher (P<0·05) than that in saline bathed gills. These results provide direct evidence both of the high metabolic activity of the gill under normal perfusion conditions and of the increased energy expenditure of the giil in hyperosmotic, compared to isosmotic, environments.
Comparative ultrastructural morphology of lamellar epithelial, chloride and mucous cell glycocalyx of the rainbow trout (Oncorhynchus my kiss) gill
Authors: Powell M. D. , Speare D. J. , Wright G. M.
Published: April 2005

A thick, elaborate glycocalyx was associated with α and β chloride cells of rainbow trout gills, a less elaborate one with surface epithelial cells and a scanty and inconspicuous one with mucous cells. The dense glycocalyx of the chloride cells may have significant function in ion regulation and metabolism of the gill.
Effects of Schistocephalus solidus (Cestoda) on the food intake and diet of the three‐spined stickleback, Gasterosteus aculeatus
Authors: Tierney J. F.
Published: April 2005

Seasonal differences were detected between uninfected sticklebacks and those infected with Schistocephalus solidus in their stomach fullness and diet composition.
Tolerance of parr of Arctic charr, Salvelinus alpinus, to reduced dissolved oxygen concentrations
Authors: Baroudy E. , Elliott J. M.
Published: April 2005

One year old pan Item Windermere (north west England) tolerated lower incipient lethal levels of oxygen [18 20 mg 1 1: 15 17% air saturation value (ASV)] at lower (5, 10°C) than at higher (15, 20°C) an elimation temperatures (2·2 2·4 mg 1 1 22 25% ASV). Values were not significantly different for two races of charr in the lake and are amongst the lowest recorded for salmenid species.
Influence of light intensity and wavelength on phototactic behaviour of larval silver perch Bidyanus bidyanus and golden perch Macquana ambigua and the effectiveness of light traps
Authors: Gehrke PeterC.
Published: April 2005

Larval golden perch, Macquaria ambigua, and silver perch, Bidyanus bidyanus, were exposed to light gradients in wavebands centred on 400, 496, 601 and 695 nm at nominal quantum irradiance values of 0–1, 1–0 and 10 μmol m−2 s−l. Silver perch larvae displayed stronger phototactic behaviour than golden perch, and both species were most responsive to light in the 601 nm waveband. The intensity of phototactic responses in both species was greater at higher irradiance levels. Enhanced responsiveness to longer wavelengths reflects possible adaptations to life in turbid habitats where the underwater light field is dominated by yellow/orange wavebands.

At night, traps fitted with 12 h yellow lightsticks attracted more golden perch larvae than traps with blue, green, orange, red or no lightstick. The efficacy of yellow lightsticks may be due to yellow/orange wavebands not being attenuated under water as rapidly as blue or red wavebands. Yellow lightsticks also emit a greater intensity of light over a longer time than other colours tested, which may have increased the effectiveness of yellow traps. Light traps were ineffective during the day.
Lateral plate morph differentiation of freshwater and marine populations of the three‐spined stickleback,Gasterosteus aculeatus, in Poland
Authors: Bańbura J.
Published: April 2005

The distribution of three main lateral plate morphs of the three–spined stickleback,Gasterosteus aculeatus, in the Polish zone of the Baltic Sea and inland waters is surveyed. Most sites are characterized by predominance of the completely plated morph, although it is only in the Vistula River drainage basin where monomorphic complete populations prevail. Polymorphic populations with a high proportion of the non–complete morphs are found in Puck Bay (the Baltic) and in south–west Poland, Possible causes of this pattern are discussed.
Whole body elemental and proximate composition of Atlantic salmon (Salmo salar) during the life cycle
Authors: Shearer K. D. , ÅSgård T. , Andorsdöttir G. , Aas G. H.
Published: April 2005

Atlantic salmon (Salmo salar) raised under production conditions were sampled periodically during their life cycle, in fresh and salt water, to determine their proximate and elemental composition. The parameters changed in relation to life cycle stage and fish size, and were influenced by whether the fish were in salt or freshwater. Measurements presented can be used to assist in the formulation of feeds, and to determine the health and nutritional status of commercially reared Atlantic salmon.
Description of a commercially important pelagic species of the genusDiplotaxodon(Pisces: Cichlidae) from Lake Malawi, Africa
Authors: Turner G. F.
Published: April 2005

A new species of pelagic haplochromine cichlid of the genusDiplotaxodonis described from Lake Malawi, Africa. The species, which attains a size of 14cm s. L., feeds mainly on zooplankton, shows no sexual dimorphism in size or body proportions, breeds throughout the year and lives at depths of 20 to at least 120 m. Approximately 600 tonnes of the species were caught by trawlers in 1990–1991, in the south–eastern arm of the lake alone. It appears that this species is a major component of the pelagic community, and occupies an ecological role similar to that of the clupeidLimnothrissa miodonin Lake Tanganyika.
Comments on the Atlantic species of the genus Evermannella (Scopelomorpha, Aulopiformes, Evermannellidae) with a re–evaluation of the status of Evermannella melanoderma
Authors: Swinney G. N.
Published: April 2005

Examination of the alimentary canal of specimens of the genus Evermannella of the form previously referred to the circumglobal species E. indica Brauer, 1906 has revealed differences between specimens from the Atlantic Ocean and those caught in the Indian and Pacific Oceans. On the basis of gut morphology and skin pigmentation the Atlantic species E. melanoderma Parr, 1928 is distinguished from the Indo–Pacific E. indica. Some observations are presented on the size structure of the E. melanoderma population off Madeira.
Effect of an anionic detergent—sodium dodecyl sulphate exposure on club cells in the epidermis of Clarias batrachus
Authors: Mittal A. K. , Garg T. K.
Published: April 2005

When treated with detergent club cells showed degenerative changes and released their contents to plug the intercellular spaces. This mechanism could act as an efficient protective barrier substantiating the role of club cells in assisting fish to overcome adverse conditions. A general decrease in the dimensions of club cells was associated with discharge of their contents. The appearance of juvenile club cells reflected their differentiation in response to increased demands to meet the challenge. Increases in the number of club cells indicated the differentiation of these cells at a rate faster than their degeneration. Localization of glycogen in club cells at the start of detergent treatment and, in general, its absence later and, in both control and juvenile club cells, is discussed in relation to the metabolic status of the cells. No marked shift was observed in the mucopolysaccharide and protein moieties of club cells.
Heart rate as an indicator of metabolic rate and activity in adult Atlantic salmon, Salmo salar
Authors: Lucas M. C.
Published: April 2005

Telemetered heart rate (fH) was examined as an indicator of activity and oxygen consumption rate (VO2) in adult, cultivated, Atlantic salmon, Salmo salar L. Heart rate was measured during sustained swimming in a flume for six fish at 10° C [mean weight, 1114 g; mean fork length (f. l.), 50·6 cm] and seven fish at 15° C (mean weight, 1119 g; mean f. l., 50·7 cm) at speeds of up to 2·2 body lengths/s. Semi–logarithmic relationships between heart rate and swimming speed were obtained at both temperatures. Spontaneously swimming fish in still water exhibited characteristic heart rate increases associated with activity. Heart rate and Vo2 were monitored simultaneously in a 575–1 circular respirometer for six fish (three male, three female) at 4° C (mean weight, 1804 g; mean F. L., 62· cm) and six fish (three male, three female) at 10° C (mean weight, 2045 g; mean f. l., 63·2 cm) during spontaneous but unquantified activity. Linear regressions were obtained by transforming data for both fH and Vo2 to log values. At each temperature, slopes of the regressions between fH and Vo2 for individual fishes were not significantly different, but in some cases elevations were. All differences in elevation were between male and female fish. There were no significant differences in regression slope or elevation for fish of the same sex at the two temperatures and so regressions were calculated for the sexes, pooling data from 4 and 10° C. There was no significant difference in the mean ± S. D. Vo2 between the sexes at 4° C (male, 66·0 ± 59·6 mgO2 kg−1 h−1; female, 88·0 ± 60·1 mgO2 kg−1 h−1) or 10° C (male, 166·2 ± 115·4 mgO2 kg−1 h−1; female, 169·2 ± 111–1 mgO2 kg−1h−1). Resting Vo2 (x̄± s. d.) at 4°C was 36·7 ± 8.4 mgO2 kg−1 h−1, and 10° C was 72·8 ± 11·9 mgO2 kg−1 h−1. Maximum Vo2 (x̄± S. D.) at 4° C was 250·6 ± 40·2 mgO2 kg−1 h−1, and at 10° C was 423·6 ± 25·2 mgO2 kg−1 h−1. Heart rate appears to be a useful indicator of metabolic rate over the temperature range examined, for the cultivated fish studied, but it is possible that the relationship for wild fish may differ.
The distribution, age and growth of wrasse (Labridae) in inshore waters of west Scotland
Authors: Treasurer J. W.
Published: April 2005

Wrasse were widely distributed in inshore waters of west Scotland in rocky and algal habitats. Ctenolabrus rupestris and Centrolabrus exoletus dominated commercial and experimental catches using creels, traps and fyke nets, but Crenilabrus melops, Labrus bergylta and L. mixtus were infrequent. Maximum age of sampled fish was 16yr in C. rupestris, 9 yr in C. exolefus, 5 yr in C. melops, 15 yr in L. bergylta, and 11 yr in L. mixtus. Growth was more rapid prior to maturation in all species. The von Bertalanffy growth model fitted data for C. rupestris and C. exoletus. Male C. rupestris and C. exoletus were significantly longer than females in most age groups and growth of all species captured in mid–Scottish areas was more rapid than in northern localities. Mortality (Z) of C. rupestris was 0–1861 per year and 0·4185 in C exoletus.
Cellular responses in the skin of the trout (Oncorhynchus mykiss) exposed to temperature elevation
Authors: Iger Y. , Jenner H. A. , Bonga S. E. Wendelaar
Published: April 2005

The skin of rainbow trout was examined at the ultrastructural and cytochemical level after a 3–h exposure to an elevation of the water temperature, from 15 to 22° C. Within 3 h, the thickness of the epidermis had significantly (P<0·05) decreased when compared to control fish. After 24 h it was restored, and from day 4 onwards even increased above control levels. The thickening of the epidermis was associated with appearance of many mitotic cells, not observed in control fish. Within 24 h many apoptotic epidermal cells were found, indicating enhanced ageing of the cells. Filament cells from the outer epidermal layers synthesized vesicles with peroxidasc activity within 3 h after temperature elevation. This enzyme was found also in apoptotic as well as in necrotic filament cells. Mucous cells became elongated and their mucosomes displayed peroxidase activity. Occasionally electrondense, probably serous, mucosomes appeared. In the epidermis rodlet cells were found. Both epideimis and dermis, became invaded by many lymphocytes and macrophages. The latter contained vesicles with peroxidase activity. Pigment–containing cytoplasmic extensions of melanocytes penetrated the epidermis while iridocytes disappeared from the dermis. The synthetic activity of dermal fibroblasts was stimulated. These results show that a moderate temperature elevation has pronounced and prolonged effects on the skin of the exposed fish. The effects are to a high extent comparable with those of stressors such as heavy metals, acid water or wounding.