bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of European bitterling in the gills of freshwater mussels
Authors: Aldridge D. C.
Published: April 2005

The development of bitterling embryos within the unique environment of a freshwater mussel's gills requires a departure from typical cyprinid embryological development. Eggs are large (2·6×1·7 mm), illustrating the low risk of predation, and elliptical; a response to unionid gill morphology and a way of increasing the transfer rates of respiratory and excretory products to and from the tissues. The yolk sac develops elongated lateral processes during early ontogeny; these secure the embryo into the host's interlamellar space. Once the larva is capable of movement (8·2 mm) the lateral processes are lost and the larva becomes less dependent of the host's gills for the provision of oxygen. Hatching (3·3 mm) and pigmentation of the blood (6·4 mm) occur relatively early; this may increase the rate of oxygen supply to the tissues. Pigmentation of the eyes and appearance of the melanophores occurs relatively late (7·4 mm and 7·9 mm, respectively); embryos are not required to detect or avoid predators. Bitterling larvae generally emerge from the host once the yolk sac has been consumed (10·5 mm); this may mark a change in respiratory and nutritional requirements.
PCR‐based sex test for Xiphophorus maculatus
Authors: Coughlan T. , Schartl M. , Hornung U. , Hope I. , Stewart A.
Published: April 2005

A simple reliable PCR‐based sex test for the platyfish Xiphophorus maculatus is described using sex chromosome‐linked molecular markers. The test can distinguish sexes prior to dimorphic differentiation without killing the fish. The method also has potential in identification of male and female embryos prior to birth.
Fast‐flowing areas affect the feeding activity of migrating Altantic salmon smolts in tributaries of a subarctic river
Authors: Heinimaa S. , Erkinaro J.
Published: April 2005

Feeding activity of migrating wild Atlantic salmon smolts was investigated in different types of tributaries of the River Teno, northernmost Finland. General feeding activity and the amount of surface prey in the stomachs were correlated inversely with proportion of habitats with high water velocity in the tributaries.
Spatial association of genetically similar Atlantic salmon juveniles and sex bias in spatial patterns in a river
Authors: Mjølnerød I. B. , Refseth U. H. , Hindar K.
Published: April 2005

Atlantic salmon (Salmo salar) juveniles were electrofished along a 300‐m stretch of a river to test for possible associations between genetic similarity and geographical distance between individuals. Multilocus DNA fingerprinting showed that genetically similar juveniles (1–4 years old) were found closer together in the river than less related individuals. However, the association between genetic similarity and geographical distance, although significant, was not strong. This may indicate that factors other than genetic relatedness influence the positioning in the river. A sex bias in the relationship between genetic similarity and geographical distance was caused by a difference between sexually mature and immature males. The study shows that sampling of salmon juveniles should be spread over a wide stretch of the river in order to avoid sampling relatives. Moreover, by including several year classes, the overall degree of genetic similarity is effectively reduced compared with sampling individuals of similar age.
The effects of food‐web management on fish assemblage dynamics in a north temperate lake
Authors: Peltonen H. , Ruuhijärvi J. , Malinen T. , Horppila J. , Olin M. , Keto J.
Published: April 2005

There was an intensive trawl fishery in the Enonselkä basin in Lake Vesijärvi (southern Finland) in 1989–1993 and thereafter the fishing intensity declined. The fish assemblage dynamics were studied both during the years of intensive trawling and for 3 years afterwards. Roach Rutilus rutilus dominated the fish assemblage before the mass removal. The intensive trawling effectively diminished the roach stock and the present fishing intensity has been sufficient to prevent its recovery. There were significant decreasing trends in the gillnet cpue (catch per unit effort) of bream Abramis brama (L.) and bleak Alburnus alburnus (L.) while increasing trend was observed in cpue of ruffe Gymnocephalus cernuus (L.) and vendace Coregonus albula (L.). Perch Perca fluviatilis L. and pikeperch Stizostedion lucioperca (L.) showed variations in cpue but no trends existed. The proportion of cyprinids decreased while that of percids and coregonids increased in the catches. The changes in the fish assemblage were induced by the intensive fishing and by the concomitant decline in the ecosystem productivity.
Evidence for anadromy in a southern relict population of Arctic charr from North America
Authors: Doucett R. R. , Power M. , Power G. , Caron F. , Reist J. D.
Published: April 2005

Stable isotope analysis of Arctic charr from a southern relict population in Québec showed that some individuals adopted anadromy as a life‐history strategy, but the strategy did not predominate in the population. Differences in length‐at‐age, ages and sex ratios between identified freshwater residents and anadromous individuals were consistent with previous descriptions of partially migratory populations. This suggests that anadromy in relict populations in Québec is associated with niche shift and occurs as a conditional response to opportunities for maximizing the rewards (e.g. fitness) of habitat use.
The role of food availability in regulating reproductive development in female golden perch
Authors: Collins A. L. , Anderson T. A.
Published: April 2005

At a time of the year when female golden perch Macquaria ambigua are not normally reproductively active, they were either fed daily to satiety (Fed), starved for 150 days (S150), or starved for 150 days then fed to satiety for 30 or 60 days (S150/F30 or S150/F60). Fish showed rapid growth and increased food conversion efficiency upon re‐feeding relative to Fed animals. The hepatosomatic indices were not significantly different between Fed, S150/F30 and S150/F60 groups, but were significantly reduced in S150 animals. The gonadosomatic indices (IG) for both Fed and S150 animals were not significantly different. However, the IG values for S150/F30 and S150/F60 animals of 6·74±1·22 and 7·84±1·12 were significantly elevated relative to Fed animals and approach those described for wild mature M. ambigua. Oocyte development in Fed and S150 animals did not proceed past the cortical alveoli or perinucleolar stages, respectively, but oocytes in both S150/F30 and S150/F60 animals had undergone vitellogenesis and were close to being mature. The concentration of oestradiol and testosterone in the plasma of S150/F30 and S150/F60 animals increased in accordance with the proposed role of these hormones in teleost reproductive cycles. The reproductive response of M. ambigua to starvation and re‐feeding is well suited to reproductive success in temperate Australian rivers where food availability is unpredictable.
Accumulation of plerocercoids of Triaenophorus crassus in the second intermediate host Coregonus lavaretus and their effect on growth of the host
Authors: Pulkkinen K. , Valtonen E. T.
Published: April 2005

Patterns of accumulation of Triaenophorus crassus in its second intermediate host whitefish Coregonus lavaretus s.l. were studied between 1991 and 1996 from two host populations in two separate areas of Lake Saimaa, Finland. Whitefish were infected commonly with several T. crassus plerocercoids and the parasites were aggregated into the oldest hosts. In one host population the annual parasite accumulation was 0·9 parasites in all host age groups between 3 and 8 years. In the other host population the annual accumulation was 1·6 parasites in 3–5‐year‐old fish, but increased up to 3 to 4 parasites per year in fish over 5 years old. The increase did not coincide with the period of maturation or any increase in whitefish growth, both of which could alter the food intake of the fish. The sharp increase in the annual accumulation suggests a threshold intensity above which the probability of acquiring further parasites increases. In spite of a heavy aggregation of parasites there was no evidence of parasite‐induced host mortality. The annual increase in mean abundance was not correlated with the mean annual weight increase in 2–4‐year‐old fish within cohorts. However, evidence of a negative effect of parasites on whitefish growth was revealed by back‐calculation of lengths of uninfected and infected whitefish and correlations between length or weight of fish and intensity of infection with fish age. Both analyses suggested that larger young fish harboured more parasites than the smaller ones while in older fish the reverse was true, a pattern that has not been shown earlier for parasitized fish.
Population genetic analysis of the haemoglobins of the black‐chinned tilapia
Authors: Falk T. M. , Abban E. K. , Villwock W.
Published: April 2005

Three highly heterogeneous haemoglobin phenotypes, each composed of 22 different haemoglobin components, were identified among 17 West African populations of Sarotherodon melanotheron. Natural populations from (1) Senegal, (2) Ivory Coast/Ghana/Togo/Benin, and (3) Congo were distinguished. The heterogeneity and specificity of these respiratory pigments was based on genetic variations at the globin chain coding loci. In total, five different α‐chains and four different β‐chains were detected by acidic urea polyacrylamide gel electrophoresis (PAGE). Combinations of α‐chains were characteristic for populations in (1) Senegal, (2) Ivory Coast, (3) Ghana/Togo/Benin, and (4) Congo. Pronounced variations at the β‐globin chain cluster were found by acidic urea triton PAGE. Cladistic analyses of the globin chain characteristics confirmed the validity of the following taxonomic units previously ranked as sub‐species: (1) populations from Ivory Coast, Ghana, Togo and Benin belong to the sub‐species S. m. melanotheron; (2) populations from Senegal form genetically a separate cluster representing the sub‐species S. m. heudelotii; (3) the Congo population, morphologically considered to represent the sub‐species S. m. nigripinnis, forms another distinct unit; but there was no evidence of S. m. paludinosus within the samples from Senegal.
Interspecific differences in growth of somatic and reproductive tissues during the breeding season in Menidia menidia and M. beryllina
Authors: Huber M. , Bengtson D. A.
Published: April 2005

The annual atherinid fishes, Menidia menidia and M. beryllina, are extremely similar morphologically, but appear to differ in their energetics and life histories. They emerge from winter in relatively emaciated condition. Menidia menidia males and females showed little change in carcass weight but significant increases in gonad weight in March and April prior to spawning in May. Female liver weight increased in March and remained high. Thus, this species had reached its reproductive size in the autumn and allocated its energy to gonadal growth during the spring. Menidia beryllina showed no significant increases in weight until early May, when carcass, liver and gonad all increased simultaneously, a pattern very different from its congener. The later spawning of M. beryllina is probably due both to its need for carcass growth in spring prior to spawning and to its apparent requirement for warmer water for growth. Females of both species invested more into liver and gonad than did males. Maximum gonadosomatic index was about twice as large for M. menidia males as for M. beryllina males, but the index was similar for females of both species.
Using micropylar ultrastructure for species identification and phylogenetic inference among four species of Sparidae
Authors: Chen K. C. , Shao K. T. , Yang J. S.
Published: April 2005

Among Sparus sarba, Acanthopagrus latus, A. schlegeli and Pagrus major, P. major had the largest egg size, with the biggest micropyle funnel and the most numerous accessory openings. The reinforcement in the micropyle canals was species specific with eight spiral clockwise, five two‐spiral clockwise, seven two‐spiral clockwise, and 10 triangular ridges in S. sarba, A. latus, A. schlegeli, and P. major, respectively. A key to identify these four species based on micropyle characters is proposed for future applications. Cladistic analysis by using different parsimonious methods on the morphological character of the micropyle suggested that the generic interrelationship between Sparus and Acanthopagrus was closer than to the genus Pagrus. Furthermore, the congeneric species of A. latus and A. schlegeli were the most closely related, with S. sarba the second, and P. major the last. This result agreed with conclusions obtained from other character suites including morphological, biochemical and molecular data.
Age structure and growth of peacock cichlids from rivers and reservoirs of Venezuela
Authors: Jepsen D. B. , Winemiller K. O. , Taphorn D. C. , Olarte D. Rodriguez
Published: April 2005

Cichla temensis collected in Venezuela attained a mean standard length of 440 mm, and C. orinocensis and C. intermedia mean lengths of 309 and 321 mm, respectively. There was little evidence of size differences between sexes. Opaque zones on otoliths corresponded to the period of peak of reproductive activity and low fish body condition (K). When aggregated across sites, linear estimates for growth of fish >age I were 57·5, 27·6, and 19·6 mm year1 for C. temensis, C. orinocensis, and C. intermedia, respectively. Fish from the Cinaruco River appeared to spawn at age I, and prior to first maturation had grown 25, 21, and 23 mm month1, respectively, for C. temensis, C. orinocensis, and C. intermedia. There was little intersite variation in growth rates, and differences in sizes of conspecifics from different sizes were due to age differences. Cichla in captivity spawn several times per year. The present results indicate that the annual cycle or tropical wet/dry seasonality promotes reproductive seasonality in Cichla. The energetic cost of reproduction and brood defence probably constrains most individuals to one spawn per year. Conversely, populations living in relatively aseasonal reservoir environments may have several spawns per year, in which case growth zones on hard structures are difficult to interpret.
Gut morphology in growth hormone transgenic Atlantic salmon
Authors: Stevens E. D. , Wagner G. N. , Sutterlin A.
Published: April 2005

Growth hormone transgenic Atlantic salmon Salmo salar reared at 12–13°C were F2 generation derived, using eggs from a transgenic F1 female and fertilized with milt from a non‐transgenic male. At the time of tissue sampling the transgenic salmon were growing 1·6 times faster than control salmon. Transgenic salmon tended to have more intestinal folds that were longer than those of control salmon. Consequently, the transgenic salmon had a larger digestive surface area both in the anterior intestine (surface area 1·5 times control) and in the pyloric caeca (surface area 1·2 times control). Most morphological features of the intestine and of the pyloric caeca of transgenic salmon were larger than those of control salmon; in particular, the surface area of the anterior intestine was concordant with the growth rate difference.
Swimbladder volume and body density in an armoured benthic fish, the streaked gurnard
Authors: Davenport J.
Published: April 2005

Body density of streaked gurnards Trigloporus lastoviza is anomalously low (mean 1·043 g ml−1) for a benthic fish and overlaps with that of pelagic fish such as cod and lumpfish. It is clear that the heavy armour of gurnards is offset by buoyancy provided by the swimbladder. Swimbladder volume is a mean 3·88% of gurnard volume. Evidence is given to indicate that this is quite large for a marine teleost: data are also presented to show that the ‘5% of fish volume for marine fish, 7% for freshwater fish’ rule for swimbladder volumes is unreliable.
Diel feeding periodicity, daily ration and prey selectivity in juvenile brown trout in a subarctic river
Authors: Kreivi P. , Muotka T. , Huusko A. , Mäki‐Petäys A. , Huhta A. , Meissner K.
Published: April 2005

Feeding of age‐1 brown trout Salmo trutta in a third‐order river in northern Finland was usually highest in the twilight hours and lowest around midday. Diel periodicity in food intake was less distinct and rarely significant for age‐0 trout. Daily rations declined seasonally, being lowest in October, and highest in June (age‐1 trout) or early August (age‐0 trout). Prey selection did not differ between day and night, but differences between age classes and sampling dates were distinct. Age‐0 trout preferred Ephemerella nymphs in summer and Micrasema larvae later in the season. Age‐1 trout fed selectively on caddis larvae on all sample dates. Aerial insects and Baetis nymphs were avoided by both age classes on most occasions. These patterns of preference are probably explained by a trend towards epibenthic feeding, which may be a predominant foraging mode in some trout populations. Nevertheless, repuscular peaks in feeding periodicity suggest that trout were able to capitalize on the increased availability of drifting prey in the twilight, especially in the early summer months.
Spatial and temporal trends in unexploited yellow eel stocks in two shallow lakes and associated streams
Authors: Carss D. N. , Elston D. A. , Nelson K. C. , Kruuk H.
Published: April 2005

Mean yellow eel density and biomass in two adjacent shallow (mean depth c 1·5 m) lochs varied significantly between years. Temporal patterns of density, biomass and size were similar in both soft and rocky substrata in the lochs, although eels were consistently smaller in the latter habitat. In both substrata, average length and weight showed a non‐significant inverse relationship with density, supporting the hypothesis of density‐dependent regulation of the yellow eel population. Fyke net catches were size selective, catching no eels <30 cm long, and providing length‐frequency information for silver eels. Fyke net catch per unit effort (CPUE) declined consistently each autumn but specific annual trends were different. When eel density increased, fyke net CPUE declined substantially.
Prior residence, territory quality and life‐history strategies in juvenile Atlantic salmon (Salmo salar L.)
Authors: Cutts C. J. , Brembs B. , Metcalfe N. B. , Taylor A. C.
Published: April 2005

Three groups of juvenile salmon were introduced sequentially into an artificial stream to investigate the effects of prior residence on behaviour and territory choice. Almost half of the first group obtained and defended distinct territories, the other half being constrained to an area approximately the size of one large territory. All of the fish in the subsequent groups, bar one, were also constrained to the same site. Since the fish were of similar size, prior residence alone seemed to influence which individuals obtained territories. However, within the first group, the fish that obtained territories were larger and more aggressive. The territorial fish did not appear to choose the most profitable territories, although they had the greatest opportunity to do so. Since juvenile salmon emerge from their gravel nests fairly synchronously, a time constraint on site sampling is hypothesised: there may be a risk in taking time to sample sites, since these same sites may become occupied with conspecifics. However, fish with territories fed at faster rates than non‐territorial fish, possibly because of reduced competition for prey items. Consequently, fish from the first group (containing most of the territorial fish) grew faster than the other two groups. Moreover, most of the territory holders, but only one of the non‐territorial fish, reached the threshold size that increases their probability of smolting the following year. This suggests that ability to obtain a defensible territory, primarily through prior residence, influences the age at which juvenile salmon can migrate to sea.
Early development of the chondrocranium in Chrysichthys auratus
Authors: Vandewalle P. , Chikou A. , Lalèyé P. , Parmentier E. , Huriaux F. , Focant B.
Published: April 2005

The inception and development of the cartilaginous cephalis skeleton of Chrysichthys auratus is described from hatching to about 18 days post‐hatching. At hatching, no skeletal structure is present. Not until day 3 do clearly delimited cranial primordia become apparent. As in many siluriforms, the neurocranium is platybasic from the start, the suspensorium constitutes, with Meckel's cartilage and the hyoid bar, a single cartilaginous element, and the junction between the front and rear of the neurocranium is complete on day 4. By day 8 the quadratomandibular joint has formed and the tectum posterius has appeared. Cartilage reduction first affects the trabecular bars, then, markedly, the visceral arches. By day 18 the braincase floor has almost disappeared.
Temperature experienced during vitellogenesis influences ovarian maturation and the timing of ovulation in common wolffish
Authors: Tveiten H. , Johnsen H. K.
Published: April 2005

Temperature treatment of common wolffish Anarhichas lupus during vitellogenesis affected the time of final maturation; ovulation in fish held at 8 and 12° C from mid‐April to October was about four and five weeks delayed, compared with a 4° C group. Fish in the 8° C group had significantly larger eggs than those in the 4° C and the 12° C groups, and a significantly higher egg production than fish in the 12° C group. Temperature treatment did not affect either fertilization rate or relative fecundity, but absolute fecundity was significantly lower in the 12° C group than the other groups due to poor growth of the fish at high temperature. This did not affect the numbers of spawning individuals. There was a trend towards lower egg survival to the eyed stage in the 12° C group compared to the 4 and 8° C groups, although the effect was not statistically significant. The results indicate that both the timing of final maturation and investment in ovarian growth in common wolffish are affected by temperature experienced during vitellogenesis.
Reproductive priming in mature male Atlantic salmon parr exposed to the sound of redd cutting
Authors: Moore A. , Waring C. P.
Published: April 2005

The sounds of a wild female Atlantic salmon cutting a redd were associated with significant increases in the levels of plasma 17,20β‐dihydroxy‐4‐pregnen‐3‐one (17,20βP) and of expressible milt in mature male parr, comparable with levels of the steroid and milt produced in parr exposed to the priming pheromone, prostaglandin F2a. Hence auditory cues may have a significant role in synchronising reproductive physiology in Atlantic salmon.
Life history traits of Pomatoschistus minutus in the Rhône Delta, France
Authors: Pampoulie C. , Rosecchi E. , Bouchereau J. L. , Crivelli A. J.
Published: April 2005

Life history traits and migratory status of the Sand goby Pomatoschistus minutus were investigated in a brackish lagoon of the Rhône river Delta (Mediterranean Sea, south of France).
Ontogeny of the stomach in winter flounder: characterization and expression of the pepsinogen and proton pump genes and determination of pepsin activity
Authors: Douglas S. E. , Gawlicka A. , Mandla S. , Gallant J. W.
Published: April 2005

Clones for two forms of pepsinogen A differing in isoelectric point as well as both α and β subunits of the proton pump were isolated from the stomach of winter flounder Pleuronectes americanus. All clones gave positive hybridization signals with DNA from other flatfish species. Reverse transcription‐polymerase chain reaction (RT‐PCR) analysis revealed that the two forms of pepsinogen were sequentially expressed. Expression of pepsinogen IIa was first detected in 13 days post‐hatch (dph) larvae and increased towards the beginning of metamorphosis at 20 dph. Expression of pepsinogen IIb and proton pump genes was first detected at 20 dph and coincided with the appearance of gastric glands and the increase in pepsin activity. The levels of expression of pepsinogen IIb as well as of pepsin activity in 20‐dph larvae were similar to those recorded in metamorphosed larvae (27 dph) and juveniles (41 dph). High pepsin activity and levels of expression of the pepsinogen and proton pump genes observed in 20‐dph larvae indicate an advanced level of development and functionality of the winter flounder stomach at this stage of ontogeny. This advanced level of the stomach development at 1 week before the currently practised time of weaning suggests that feeding formulated feeds may be initiated earlier.
Sex ratios in offspring of sex‐reversed sea bass and the relationship between growth and phenotypic sex differentiation
Authors: Blázquez M. , Carrillo M. , Zanuy S. , Piferrer F.
Published: April 2005

Groups of sexually undifferentiated sea bass Dicentrarchus labrax were fed with the androgen 17α‐methyltestosterone (MT) during sex differentiation. MT treatment increased males from 79±3% in the controls (the usual 3:1 male:female sex ratio of cultured sea bass) to 100±0%, implying that in the treated groups one out of each five resulting males was a masculinized female (neomale). Thirteen males from the MT treated groups were taken as the parental generation and their sperm used to individually fertilize a pool of eggs from unrelated females. The probability of having at least one neomale was 95% and most probably two or three of the males used were neomales. The offspring from each family were reared separately under the same environmental conditions. Samples were taken at 11 and 15 months of age, during and after sex differentiation, respectively. Results showed that females predominated among the larger fish whereas males and undifferentiated fish predominated among the smaller ones. Intersexes exhibited an intermediate size. All fish with a body length smaller than 12 cm were undifferentiated. These results suggest that sex differentiation is more dependent on length than on age. At 15 months, sex ratios were male‐biased in all families, except one (females ranged from 5 to 50%) and only two families had sex ratios not significantly different from 1:1, suggesting that the mechanism of sex determination in the sea bass is not of a XX/XY or ZW/ZZ type since no family exhibited a female‐biased progeny, as would be expected from both types. Results support the hypothesis that factors other than genetic, i.e., environmental, may act epigenetically on the sex determination mechanisms of sea bass, as has been demonstrated in other fishes.
The skin pattern of young plaice and its rapid modification in response to graded changes in background tint and pattern
Authors: Healey E. G.
Published: April 2005

Young plaice, kept on a standard background and trained for 3–4 weeks, were photographed to record short‐term nervously controlled responses to plain grey and patterned backgrounds, graded and quantitatively defined with regard to reflectivity and dimensions. Systems of primary, secondary and lower‐order black and white spots and flecks became prominent or hidden in hierarchical order. Spots at any one level in a hierarchy were approximately evenly distributed. Black spots enlarged with increased size or number of black circles in the background but responded differently to unpatterned grey backgrounds. White spots had a centre and surrounding annulus both of which could be pale or independently variably occluded centrally, peripherally or overall. Peripheral occlusion of the annuli contributed to skin darkening and by extending inwards to include the centre it progressively diminished the white spots. The system of white spots was responsible for the smaller skin patterns, the finest being produced through disruption by the white flecks of the annuli, black spots and dark patches. There was great variation in response of individuals. Erratic and poor background responses were generally associated with abnormalities in the white spots.
Lack of gas bladder inflation by the larvae of zebrafish in the absence of an air‐water interface
Authors: Goolish E. M. , Okutake K.
Published: April 2005

Compared to a control gas bladder inflation rate of 95·1±1·9%, zebrafish Danio rerio larvae 72 h post‐fertilization maintained in closed chambers had an inflation rate of just 19·1±7·7%. Larval survivorship through 10 days in closed chambers (32%) was significantly less than that in open chambers (76%), and the extent of spinal curvature was significantly higher among larvae maintained in closed chambers. Larvae which failed to inflate their gas bladder showed very little change in body length, and had a final dry weight c. 14% of that for control larvae. The small number of larvae with inflated gas bladders found in closed chambers might be attributed to the inadvertent introduction of small bubbles into two replicates. These results indicate that access to an air‐water interface is critical for the normal development of zebrafish larvae, but also that a small, submerged, spherical gas volume may to a limited extent be used for initial gas bladder inflation.
Effects of social and visual contact on the oxygen consumption of juvenile sea bass measured by computerized intermittent respirometry
Authors: Herskin J.
Published: April 2005

The resting metabolic rate (RMR) of juvenile European sea bass Dicentrarchus labrax L. (47·5±1·5 g, 15–18 cm) was 126·2±2·5 mgO2 kg−1 h−1, and temporal patterns of oxygen consumption were not affcted by visual contact or social interaction with conspecifics. The results suggest that a group effect is not present in juvenile D. labrax, thus no selective advantage of shoaling is gained through lowered metabolism in this facultative schooling species.
Pattern of movements of adult Barbus haasi in a small Mediterranean stream
Authors: Aparicio E. , De Sostoa A.
Published: April 2005

Most adult Barbus haasi, at a 1950 m‐long site in Vallvidrera creek, were highly sedentary and resided within a home range <20 m (32 m2), while a small group were more mobile. On successive sampling occasions, between 52·3 and 64·9% of fish were recaptured in the same 10‐m‐long section in which they had previously been captured. Movements over long distances were infrequent, and only 5·6% of the fish moved >100 m. The movement pattern of the population was seasonally stable, although the mean distances were slightly greater in summer because of the medium‐range movements of a few individuals. Overall, upstream and downstream movements were equally common but a significant downstream movement occurred in spring. The size of the fish did not influence the movement rate. Fish inhabiting those sections of the stream with greater depth, slower current and more cover had a lower movement rate than fish occupying shallower, exposed sections. The restricted movement of B. haasi could increase the survival of fish by increasing the probability of staying in the remaining pools during summer dry‐out, and may therefore be of adaptive significance.
Ultrastructure of the collagen fibrils in the coelacanth
Authors: Jarial M. S. , Ganion L. R. , Verhoestra B. A.
Published: April 2005

The collagen fibrils in the rectal gland capsule of the coelacanth Latimeria chalumnae are c. 127 nm in diameter and resemble those fibrils that play an active mechanical role in trout skin. The fibrils having periodicity of about 54 nm and seven intrabands per period suggest that the collagen molecules in Latimeria are shorter, a feature they presumably share with lower tetrapods.
Enhancing the contrast and visibility of daily growth increments in fish otoliths etched by proteinase K buffer
Authors: Shiao J. C. , Tzeng C. S. , Leu C. L. , Chen F. C.
Published: April 2005

The otoliths of the amphidromous gobies Stiphodon elegans and Sicyopterus japonicus, a marine eel Strophidon sathete and a freshwater fish Varicorhinus barbatulus were digested by proteinase K buffer (PKb), which removed the proteins and retained the major calcified structure to reveal conspicuous daily increments. Compared with etching by ethylenediaminetetraacetate (EDTA), etching with PKb revealed more visible daily increments and enhanced the contrast. Moreover, by using PKb, both the daily increments and annuli could be observed simultaneously. The better performance of PKb as an etching agent can be attributed to digesting of predominantly only the organic matrix and leaving the calcified structure almost intact. PKb provides another effective means to reveal otolith microstructure so as to examine and count daily growth increments.
Papyrus swamps, hypoxia, and faunal diversification: variation among populations of Barbus neumayeri
Authors: Chapman L. J. , Chapman C. A. , Brazeau D. A. , McLaughlin B. , Jordan M.
Published: April 2005

To test whether patches of papyrus swamp contribute to diversification of populations of non‐air‐breathing fishes, the gill morphology of Barbus neumayeri was compared between a papyrus swamp and several tributaries which differed in oxygen regime. Total gill filament length differed among sites and was negatively related to dissolved oxygen availability, supporting strong selection pressure for low‐oxygen tolerance in the swamp interior. Among recaptures of marked B. neumayeri over a 4·5‐year period among the focal swamp and connected stream and river sites, 93% of fish were recovered at the site of capture. Some of the individuals that moved crossed physicochemical gradients and traversed long distances within the swamp/stream system. This movement rate would theoretically be sufficient to homogenize gene frequencies among populations. However, randomly amplified polymorphic DNA (RAPD) markers indicated significant genetic differentiation among sites and no relationship between genetic differences and geographical distances among sites suggesting habitat‐specific selection pressures on dispersers, rather than insufficient dispersal.
Differential utilization of energy during wintering and spawning migration in Norwegian spring‐spawning herring
Authors: Slotte A.
Published: April 2005

The energy utilization in non‐feeding Norwegian spring‐spawning herring Clupea harengus was examined during periods of wintering in a fjord system in northern Norway and southward spawning migration (800 km distance) to the main spawning area off western Norway. At the onset of wintering the gonadosomatic index (IG) was higher and the amount of mesenteric fat was lower in male than in female herring, whereas the subsequent increase in IG and decrease in mesenteric fat occurred at a higher rate in females than in males. However, no differences were recorded between sexes in fat content (%) of whole fish at any time of the year. The absolute energy loss increased, whereas the relative energy loss decreased, with fish length. Furthermore, the absolute and relative length specific energy losses were two to three and three to four times higher, respectively, during spawning migration than during wintering. The distinct energy loss was attributed mainly to fat metabolism, whereas the storage protein only was transferred from the soma to the gonads and remained relatively constant in whole herring throughout the wintering and spawning migration. © 1999 The Fisheries Society of the British Isles
Observations on reproduction of the Lake Tana barbs
Authors: Dgebuadze Yu. Yu. , Mina M. V. , Alekseyev S. S. , Golubtsov A. S.
Published: April 2005

During the rainy season (September–November 1994), in tributaries of Lake Tana (Ethiopia), the Gumara, Gelda and Negashu, barbs of diVerent morphotypes were ready to spawn, running and spent. The most numerous were barbs similar to Barbus intermedius common in many rivers of the Ethiopian Highlands. They were also found spawning in the Gumara and Gelda Rivers in the dry season (February 1996, 1997). There were no evident diVerences in time and place of spawning of barbs representing diVerent morphotypes. Only zurki, bigmouth mini‐eye and bighead were not found in the rivers. Spatial and temporal segregation may contribute to reproductive isolation of morphotypes spawning in rivers, but if reproductive isolation exists the main role must be played by diVerences in mating behaviour. Morphotypes of the Lake Tana barbs have diVerent migration patterns. Barbs similar to the riverine B. intermedius may spend their lives in rivers or in the lake, moving to and fro. Barbs of acute, bigmouth big‐eye and, perhaps, other morphotypes migrate downstream as alevins or fry, stay in the lake for several years and migrate back into rivers for spawning after reaching maturity.
Osteological development of the vertebral column and of the caudal complex in Dentex dentex
Authors: Koumoundouros G. , Divanach P. , Kentouri M.
Published: April 2005

Osteological development of the vertebral column and caudal complex in common dentex was described under extensive larval rearing conditions. Generally, the cartilaginous bones developed prior to the membranous bones. The development of the axial skeleton began with the formation of the hypural 1, the neural arches 2 and 3, as well as the haemal arches 1–8 at 4·8, 4·9 and 5·0 mm total length (LT, measured in vivo), respectively. By 7·5 mm LT, all the cartilaginous elements were formed, except for the ventral ribs, which formed between the range of 8·4–18·0 mm LT. The caudal lepidotrichia were the first membranous bones to appear (5·3 mm LT) and attain their full meristic count (7·4 mm LT), followed by the vertebral centra, which formed between 6·6 and 9·7 mm LT. By 25·0 mm LT, all the elements were fully ossified except for the ventral ribs. The developmental direction and order of all the elements were studied with respect to their formation and ossification. The results were discussed in the contexts of ichthyoplankton, ecology and aquaculture. Compared with other Sparidae species, common dentex followed a pattern of relatively rapid rate of osteological development.
Differences in growth rates among cohorts of Encrasicholina punctifer and Engraulis japonicus larvae in the coastal waters off Tanshui River Estuary, Taiwan, as indicated by otolith microstructure analysis
Authors: Wang Yu‐Tzu , Tzeng Wann‐Nian
Published: April 2005

The hatching dates of Encrasicholina punctifer and Engraulis japonicus larvae collected in the coastal waters off Tanshui River Estuary during the fishing seasons of 1992 and 1993 indicated that these two anchovies had protracted spawning seasons, which resulted in multiple recruitment cohorts. Encrasicholina punctifer larvae recruited to the estuary from October to March, while the majority of E. japonicus larvae came in March‐May and to a lesser extent in October and November. The E. punctifer larvae on arrival to the estuary were 17·4–35·6 mm in length, 167ndash;89 days old and had growth rates of 0·4–1·0 mm day−1, E. japonicus larvae were 12·1–32·7 mm in length, 19–62 days old and had growth rates of 0·7–0·9 mm day−1. Growth rates were significantly different among cohorts and positively correlated to water temperature.
Morphometric analysis of axial muscle in cyprinid fish provides support that intracellular lipid plays a role in slow fibre oxygen supply*
Authors: Sänger A. M.
Published: April 2005

In the present study, slow axial muscle of three species of cyprinid fish, Danube bleak, nase and chub, was examined for intracellular lipid. Data from fish held under constant conditions in the laboratory (with and without locomotory exercise training) were compared with data from fish living in the wild. The laboratory‐reared fish (trained and untrained) as well as the fish from the wild showed species‐dependent differences of intracellular lipid content in their slow muscle, with values being higher in Danube bleak than in nase and chub. This suggests that accumulation of intracellular lipid within slow muscle fibres is partly under the influence of factors other than environmental ones, for example, capillary density. To test whether intracellular lipid facilitates oxygen transport from capillaries to mitochondria within the muscle fibres in those fish with a relatively low capillary density but high lipid content, this work also quantified slow muscle capillary supply. Under each life regime, the capillary densities for chub and nase were higher than those for Danube bleak. The negative correlation of intracellular lipid and capillary density is in favour of this supposition.
Skeletal deformities in elasmobranchs from Australian waters
Authors: Heupel M. R. , Simpfendorfer C. A. , Bennett M. B.
Published: April 2005

Four shark species in Australian waters were found with skeletal deformities. Deformities were similar across three species with large scoliotic, lordotic and kyphotic bends of the vertebral columns. The cause of these deformities is currently unknown.
Myogenic regulatory factors and muscle differentiation during ontogeny in fish
Authors: Watabe S.
Published: April 2005

cDNA clones encoding the myogenic regulatory factors, myogenin, MyoD and myf‐5 were cloned by reverse‐transcription polymerase chain reaction from larvae and embryos of the common carp. MEF2 cDNAs were also identified from an adult carp cDNA library. During the period of somite formation for carp, myf‐5 was the first factor to be expressed followed by MEF2C and MyoD, then myogenin and MEF2A, and finally skeletal myosin heavy chain and α‐actin. This study also examined, by Northern blot analysis, the accumulated mRNA levels of myosin heavy chain (MyHC) isoforms in carp fast skeletal muscle during water temperature acclimation from 20 to 30°C in relation to those of MyoD family and MEF2 family members. There was a dramatic decrease in the transcripts of the MyHC isoform predominantly expressed in cold‐acclimated carp and a significant increase in the transcripts of the MyHC isoform predominantly expressed in warm‐acclimated carp. Over the same acclimation period, the transcription levels of myogenin, MEF2A and MEF2C changed significantly, whereas MyoD transcripts were rather constant. The possible roles of MRFs and related transcription factors in muscle differentiation of fish are discussed.
Muscle growth in yolk‐sac larvae of the Atlantic halibut as influenced by temperature in the egg and yolk‐sac stage
Authors: Galloway T. F. , Kjørsvik E. , Kryvi H.
Published: April 2005

Atlantic halibut eggs and yolk‐sac larvae were incubated at 1, 5 and 8° C. Eggs incubated at 8° C gave slightly shorter larvae at hatching with a significantly smaller total cross‐sectional area of white muscle fibres than eggs incubated at 5° C. Transport of eggs 2 days prior to hatching gave significantly longer larvae at hatching with a significantly larger red fibre cross‐sectional area than when eggs were transported shortly after the blastopore closure. A higher survival until 230 degree days after hatching was also observed in the former group. All eggs incubated at 1° C died before hatching and all larvae incubated at 1° C died before 45 degree days after hatching. From hatching until 230 degree days the total white cross‐sectional area increased threefold in all temperature groups. The increase in white cross‐sectional area was entirely due to hypertrophy between hatching and 150 degree days (10 mm LS). Recruitment of new white fibres increased in germinal zones at the dorsal, ventral and lateral borders of the myotome from 150 degree days onwards, but at 230 degree days (12–13 mm LS) the recruitment fibre zone constituted <10% of the total white cross‐sectional area. Larval incubation at 8° C gave slightly longer larvae with a significantly larger cross‐sectional area of recruitment fibres at 230 degree days than incubation at 5° C. The larval group incubated at 8° C also had a significantly lower survival until 230 degree days than did the 5° C group. Incubation temperature regimes did not affect the volume density of myofibrils in the axial muscle fibres at 230 degree days. Thus hypertrophy is the predominant mechanism of axial white muscle growth in Atlantic halibut yolk‐sac larvae and an increased rearing temperature during the yolk‐sac stage increases white muscle fibre hyperplasia.
Control of the somatic growth in turbot
Authors: Boeuf G. , Boujard D. , Ruyet J. Person‐Le
Published: April 2005

The development of a recombinant turbot somatotropin (rtuGH) in Escherichia coli and an homologous antibody in rabbit has produced a sensitive and specific RIA allowing the measurement of blood levels and pituitary contents of tuGH and their responses to environmental change. Turbot IGF‐1 (insulin growth factors) and IGF type 1 receptor (R) cDNA have also been cloned and sequenced. The deduced IGF‐1 R primary sequence contains all the topological features characteristics of mammalian IGF‐1 R and the turbot R appears highly conserved, compared to its mammalian counterpart, particularly within the catalytic domain. IGF‐1 R mRNA polyadenylation status varies during development with polyadenylation occuring in oocytes and early stage larvae. It disappears in later stages and in adult somatic tissues, indicating that IGF‐1 R mRNA undergoes complex post‐transcriptional regulation. Thyroid hormones (TH, both T3 and T4), are also involved in growth control, but are less affected by environmental changes than GH, except in very extreme conditions. The thyroid stimulating hormone (TSH) β‐subunit cDNA fragment has also been cloned and sequenced. mRNA expression levels have been quantified under conditions where blood circulating TH were modified by dietary treatments or hormone supplementation. Specific growth rate in turbot is related to food intake and is doubled with a temperature increase from 8 to 20° C. Lipid storage by contrast was higher at low temperatures. Over a long time course, growth rate in turbot can be improved in brackish water (8–20 psu) but it cannot adapt to very low salinities. Photoperiod appears to have little influence on growth when feeding is unrestricted. Under intensive farming conditions, ammonia, the major nitrogen waste product in teleosts, may increase to levels that can reduce growth. Safe ambient levels for growth are <2–3 mg l−1 TAN above which a 10–20% decrease in growth was recorded within 3 months. Over 20 mg l−1, feeding stops and no growth occurs. Turbot juveniles can cope efficiently with relatively large fluctuations in ambient oxygen, but major disruptions to physiological functions occur below 20% of air saturation. Under moderate hypoxia growth is reduced by 20% within 1.5 months. The primary response to hypoxia or ammonia accumulation is always a decrease of food intake.
Energy metabolism in eggs and larvae of the Senegal sole
Authors: Parra G. , Rønnestad I. , Yúfera M.
Published: April 2005

Oxygen consumption in Solea senegalensis increased during the egg stage reaching values close to 4 nmol O2 ind−1 at hatching. After hatching, larval oxygen consumption continued to increase, reaching a maximum rate of 9.97−1±87 nmol O2 ind−1 h−1 2 days after the opening of the mouth. Body nitrogen content decreased mainly after exhaustion of yolk reserves. Carbon content decreased during the whole endogenous feeding phase, although it decreased twice as quickly after yolk‐sac absorption. The free amino acid (FAA) depletion rate was higher during egg development and the yolk‐sac period. Complete yolk absorption coincided with the consumption of the 90% of initial FAA content in the eggs and the remaining FAA were consumed at a lower rate. Based on stoichiometrical calculations, FAA appears to be the most important energy substrate during the egg stage (86%) in the Senegal sole. During the period from hatching to the mouth opening, contributions of FAA and lipids as metabolic fuels were similar (41 and 47%, respectively). The decrease in larval protein content during starvation indicates that amino acids from body protein are used as energy substrates under food deprivation.