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  • 1
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    Limitations on visual food-location in the planktivorous antarctic fishPagothenia borchgrevinki (1989)
    Springer
    Details
    Publication Date: 1989-04-01
    Print ISSN: 0014-4754
    Topics: Biology , Medicine
    Published by Springer
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  • 2
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    Reproductive periodicity and steroid hormone profiles in the sex-changing coral-reef fish, Plectropomus leopardus (2007)
    Springer
    Details
    Publication Date: 2007-02-06
    Print ISSN: 0722-4028
    Electronic ISSN: 1432-0975
    Topics: Biology , Geosciences
    Published by Springer
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  • 3
    Electronic Resource
    Electronic Resource
    Patterns of oocyte growth, vitellogenin and gonadal steroid concentrations in greenback flounder (2004)
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    Journal of fish biology 64 (2004), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The pattern of oocyte development in association with changes of plasma concentrations of vitellogenin (Vtg), 17β-oestradiol (E2) and testosterone (T) was investigated in maturing female greenback flounder Rhombosolea tapirina over the first part of a reproductive season (February to June). Examination of oocyte size-frequency distributions showed that the oocyte developmental pattern in R. tapirina is multiple group synchrony, and that reproductively mature fish were present at all sampling times. There were no significant temporal variations in the gonado-somatic index (IG), hepato-somatic index (IH), or plasma concentrations of Vtg, E2 and T during the sampling period, which indicates that reproductive development is not synchronized within the population. Significant increases in IG, IH and plasma concentrations of Vtg, E2 and T, however, were observed in vitellogenic fish, and in fish undergoing final maturation. A positive relationship was also found between the growth of oocytes and plasma concentrations of Vtg, E2 and T, although the patterns of increase were different for each variable. Plasma concentrations of Vtg and E2 rose steadily across oocyte sizes from 100 to 450 μm, but the rate of increase of plasma E2 was slower than that of Vtg, and both reached a saturated concentration at oocyte sizes of c. 450 μm. In contrast, plasma concentrations of T showed no marked increase until oocytes grew beyond 400 μm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.0022-1112.2004.00406.x
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Steroid hormone levels and bi-directional sex change in Gobiodon histrio (2003)
    Oxford, UK : Blackwell Science Ltd
    Journal of fish biology 62 (2003), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Sex change in the coral-dwelling goby Gobiodon histrio was induced by placing two adult fish of the same sex on a coral colony. The sex change of individual fish was confirmed using histology, and whole-body concentrations of the gonadal steroids testosterone (T), 11-ketotestosterone (11-KT), and 17β-oestradiol (E2) were examined. The results show that T, 11-KT and E2 occurred in both female and male G. histrio. E2 concentration in females was twice that in males, while concentrations of T did not differ between the sexes. Contrary to predictions, concentrations of T and E2 did not differ between fish that changed sex and those that did not. Most samples had 11-KT concentrations below minimum levels of detection ( i.e. 〈0·15 ng ml−1) and were therefore not analysed statistically. The results suggest that: (i) specific activation or de-activation of the T–E2 (aromatase) pathway is a probable candidate for mediating serial adult sex change in G. histrio, and (ii) low levels of 11-KT may be important in allowing serial adult sex change in G. histrio.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1095-8649.2003.00017.x
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  • 5
    Electronic Resource
    Electronic Resource
    Physiological stress responses to confinement in diploid and triploid Atlantic salmon (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 56 (2000), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Confinement of juvenile Atlantic salmon Salmo salar from four different populations (all–female diploids, all–female triploids, mixed sex diploids and mixed sex triploids) either before (FW parr) or after (SW smolts) transfer to sea elevated plasma cortisol and plasma lactate from control levels irrespective of ploidy status. Both before and after confinement, plasma cortisol levels in SW smolts (6–174 ng ml–1) were higher than those in FW parr (4–58 ng ml–1), which possibly reflected the physiological challenge of acclimation to SW. Mixed sex populations of SW smolts had higher cortisol levels than all–female populations. The duration of confinement (1, 3 or 6 h) affected the magnitude of the plasma cortisol and lactate responses in SW smolts. Plasma cortisol levels in diploid and triploid SW smolts subjected to 2 h of confinement decreased to pre–stress levels within 6 h post–confinement. Plasma lactate levels were not significantly different from pre–stress levels 48 h after confinement. As no difference exists in primary and secondary stress responses of Atlantic salmon of differing ploidy status, it is unlikely that differences in mortality rates between diploid and triploid populations under commercial conditions can be attributed to differences in their physiological responses to periods of stress lasting up to 6 h.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.2000.tb00751.x
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  • 6
    Electronic Resource
    Electronic Resource
    Capture and handling stress affects the endocrine and ovulatory response to exogenous hormone treatment in snapper, Pagrus auratus (Bloch & Schneider) (2002)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 33 (2002), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Sexually mature female hatchery-reared snapper, Pagrus auratus (Bloch & Schneider) were captured from sea cages by handline and injected at first capture (control) or 24 h after capture, transport and subsequent confinement (delayed injection) with either saline, luteinizing hormone releasing hormone analogue, human chorionic gonadotropin, or 17α-hydroxyprogesterone. Blood was sampled before hormone treatment and again after 168 h, and fish were checked daily for ovulation. Plasma levels of 17β-estradiol (E2), testosterone (T), 17α, 20β dihydroxy-4-pregnen-3-one (17, 20βP) and cortisol were determined by radioimmunoassay. The ovulatory response was assessed from the proportion of fish ovulating, ovulation volume, egg quality and fertility. A delay in injection resulted in significantly lower plasma E2 and T levels in response to hormone treatment, smaller ovulation volumes, and poorer egg quality than in control fish. The results are consistent with the generally inhibitory effects of stress on reproduction in fish, and confirm the requirement to treat fish with hormones designed to induce ovulation, as soon as possible after capture and disturbance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.2002.00718.x
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  • 7
    Electronic Resource
    Electronic Resource
    Histological changes in the gonad, skin, intestine and olfactory epithelium of artificially-matured male American eels, Anguilla rostrata (LeSueur) (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 32 (1988), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Migratory (silver) male American eels were injected weekly for 5 weeks with human chorionic gonadotropin (hCG), salmon pituitary extract, hydrocortisone 21-hemisuccinate (cortisol), or saline to determine the effects of induced maturation on the histology of their gonads, skin, intestines and olfactory epithelia. Treatment with hCG induced full sexual maturity, salmon pituitary evoked only limited spermatogenesis, and neither hydrocortisone nor saline had any effect on the gonad. Eels injected with hCG and salmon pituitary experienced no changes in skin morphology, but the epidermal thickness of saline- and hydrocortisone-treated fish decreased. Intestinal morphology did not change in any of the treatment groups. Both the presumed sensory and non-sensory portions of the olfactory epithelium of hCG- and pituitary-treated males exhibited a decrease in thickness, structural degeneration, and non-significant reductions in mucous cell density. Some of these changes in maturing male eels are similar to those previously observed in maturing females but others are different; it appears likely that maturing Anguilla are sexually dimorphic and that these changes are adaptive and not artifacts of the hormone treatments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1988.tb05363.x
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  • 8
    Electronic Resource
    Electronic Resource
    Structure and colour of the integument of the European eel Anguilla anguilla (L.) (1982)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 21 (1982), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The structure of the integument of 26 wild and nine artificially matured female Anguilla anguilla, and 30 sexually immature eels maintained in controlled lighting, was investigated. Melanophore densities varied in a way unrelated to maturity while xanthophores were progressively lost from lower levels in the skin. Reflecting layers made up of the purines, guanine and hypoxanthine were associated with chromatophore layers. Purine concentrations (as a percentage of total skin dry weight) decreased with maturity but a reorganization of the reflecting elements occurred. Colour changes associated with maturation were due to the redistribution of purines. Spectral and angular reflectance measurements indicate that the integument has camouflage value and colour changes can be related to the change in habitat occurring with migration. The usefulness of colour as an index of sexual maturity is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1982.tb02833.x
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  • 9
    Electronic Resource
    Electronic Resource
    Stress-induced changes in concentrations of plasma sex steroids in black bream (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 55 (1999), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Cortisol levels of black bream Acanthopagrus butcheri at capture did not change with time of day, gonadal stage or season and were 1·9±0·2 and 2·8±0·4 ng ml−1 for male and female fish, respectively. Confinement resulted in significantly elevated cortisol levels at all time periods; however, levels after 24 h of confinement were significantly lower than peak cortisol levels (15 min for males and 1 h for females). Confinement stress resulted in reduced levels of 17β-oestradiol (E2) and testosterone (T) within 1 h in sexually mature females. In mature males, suppression of T and 11-ketotestosterone (11KT) occurred after 30 min and 6 h of confinement, respectively. The relationship between confinement stress and levels of 17,20β-dihydroxy-4-pregnen-3-one (17,20β P) was more complex, with levels in males being elevated after 15 min and 24 h and suppressed after 6 h of confinement. In contrast, 17, 20β P levels in females were elevated after 1 h of confinement. In regressed females, plasma E2 and T concentrations were low at capture and were not affected by confinement stress whereas plasma 17, 20β P was elevated within 1 h. This study indicates that stress exerts a rapid inhibitory effect on gonadal steroidogenesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1999.tb02077.x
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  • 10
    Electronic Resource
    Electronic Resource
    The effects of capture, handling, confinement and ectoparasite load on plasma levels of cortisol, glucose and lactate in the coral reef fish Hemigymnus melapterus (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 57 (2000), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Tropical labrids Hemigymnus melapterus sampled underwater had low plasma levels of cortisol, glucose, and lactate. Plasma cortisol levels were elevated by capture stress within 5–6 min, while glucose and lactate levels were not. Plasmalevels of cortisol and glucose increased after 2–4 h of handling and transport to the laboratory. Levels of cortisol and glucose fell with laboratory acclimation back to values similar to those found in wild fish. Parasitism by gnathiid isopods across an order of magnitude of isopod numbers had no effect on plasma levels of cortisol or glucose. Thus, H. melapterus has a stress response similar to that shown by temperate species, and relatively high parasite loads are not apparently stressful to fish in the wild. This may be related to the counterproductive effects of physiological stress responses on the immune system or behaviour-modulated processes that counter parasitic invasion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.2000.tb02179.x
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