ISSN:0002-8487    

DOI:10.1577/1548-8659(1984)113<411:RIF>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Plasma-corticosteroid concentrations in resting channel catfish Ictalurus punctatus held at 21 C varied only slightly during a 24-hour period; further, increases in hormone concentrations induced by confinement stress were independent of time of day and photoperiod. Temperature strongly affected both resting corticosteroid concentrations and the dynamics of hormone secretion when fish were stressed. Resting concentrations were greatest in fish acclimated to 5 and 10 C (25–29 ng/ml), sharply lower in fish held at 15, 20, or 21 C (5–9 ng/ml), and intermediate in fish maintained at 25, 30, or 35 C (12–13 ng/ml). Hormone concentrations increased when fish were stressed by confinement. Corticosteroid concentrations hardly changed in fish held at 5 or 10 C, but increased markedly in fish at higher temperatures; in addition the response was more delayed at the lower temperatures.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1984)113<414:BAAIOC>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The gulf killifish Fundulus grandis undergoes an annual cycle of reproductive, metabolic, and behavioral changes. The seasonal changes are determined primarily by water temperature and by endogenous seasonal alterations in the interpretation of water temperature. The evidence suggests that both exogenous and endogenous determinants involve an interaction of two circadian neuroendocrine oscillations. One neuroendocrine oscillation, and its circadian expressions, is entrained by the daily light-dark cycle. The other oscillation, and its circadian expressions, is coupled to the first oscillation in various phase relations as a function of season and ambient temperature. A temporal synergism of these oscillations and their circadian expressions produces appropriate complexes of physiological and behavioral conditions. The circadian rhythms of plasma cortisol and prolactin concentrations appear to be circadian expressions of the two oscillations, and timed daily injections of cortisol and prolactin can produce different reproductive, metabolic, and behavioral conditions as functions of the time relations between the hormone injections. Similarly, daily injections of drugs that influence serotonergic (5-hydroxytryptophan, 5-HTP) and dopaminergic (dihydroxyphenylalanine, DOPA) activities can induce conditions appropriate to either summer or winter and can determine the manner in which a fish reacts reproductively and metabolically to water temperature. Thus, it is proposed that cortisol and 5-HTP injections entrain one of the neuroendocrine oscillations and that prolactin and DOPA entrain the other.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1984)113<422:TSOCNO>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

A variety of opioid peptides have been described within the vertebrate central nervous system and implicated in the regulation of many rhythmic behavioral and physiological functions. Recent comparative studies point to an early evolutionary development and phylogenetic continuity in the involvement of these opioid peptides in the mediation of basic homeostatic functions. Fish schooling, which can be considered as an early form of vertebrate social behavior, is affected by manipulations of endogenous opioid activity. Furthermore, the extent of opioid involvement in the determination of schooling behaviors undergoes significant day-night variations. The pineal gland, a region of the brain that has been implicated in the determination of circadian rhythmicity in teleost fish, is involved in the modulation of these opioid effects on schooling. It is suggested that interactions between the pineal gland and opioid peptides may be involved in the regulation of rhythmic behaviors and that fish can serve as a useful system to investigate this.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1984)113<432:OPTPGA>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Previous evidence has demonstrated a relationship between the pineal organ and carbohydrate metabolism in goldfish Carassius auratus. Pinealectomy in this species causes a decrease in liver-glycogen stores, disappearance of the diurnal variation in liver-glycogen concentrations, and an increase in plasma glucose. These effects occur independently of photoperiod acclimation and are seasonal in nature. Results presented in this paper suggest that the pineal organ may regulate carbohydrate metabolism by altering insulin responsiveness in these animals. Goldfish that are pinealectomized during the spring resist insulin-induced hypoglycemia more than sham-operated animals. This insulin resistance is not induced by pineal-organ removal during late summer. Glucose-tolerance tests of pinealectomized animals during midwinter and late summer indicate that pineal-organ removal had little or no effect on insulin activity during these months. The seasonality of these responses coincides with the seasonality of the known relationship between pineal organ and carbohydrate metabolism. The insulin resistance induced by pinealectomy during the spring may account for the metabolic effects of pineal-organ removal.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1984)113<439:PAOTPO>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Long-term (annual and seasonal) variations in plasma concentration of reproductive hormones (maturational gonadotropin GTH and sex steroids) have been studied in relation to the gonad cycle in some teleosts. Plasma GTH concentrations are low and increase only gradually during the major part of gonad development (vitellogenesis, spermatogenesis) but increase sharply towards the end of gametogenesis–that is, around the time of oocyte maturation and ovulation and before the start of spermiation. In females, plasma concentrations of 17β-estradiol and estrone rise continuously during vitellogenesis. In salmonids, after a decrease in 17β-estradiol concentration starting at the end of the vitellogenesis, there is a small peak in testosterone concentration followed by a strong transient rise in 17α-hydroxy-20β-dihydroprogesterone, which induces oocyte maturation. The concentrations of testosterone and 11-ketotestosterone rise during spermatogenesis. Maximal concentrations of 11-ketotestosterone were recorded in rainbow trout Salmo gairdneri just prior to the start of spermiation. Plasma concentrations of both androgens in this species dropped during spermiation, whereas that of 17α-hydroxy-20β-dihydroprogesterone showed an important rise. Short-term (circadian and ultradian) variations in concentrations of reproductive hormones in teleosts have been less studied. Daily fluctuations in plasma GTH and in sex steroid concentrations, the pattern of which depends on the development stage of the gonads, have been demonstrated in a few fish species. Pulsed gonadotropin secretion occurs in some phases of gametogenesis in rainbow trout and common carp Cyprinus carpio.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1984)113<444:AADCIP>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Mummichogs Fundulus heteroclitus exhibit changes in the timing of their annual reproductive activity when exposed to experimental photoperiods and temperatures. Although long days and warm temperatures did not maintain gonad maturity past the normal end of the spawning season, premature recrudescence was induced in winter when fish were exposed to 13- or 15-hour light periods (long days) each 24 hours. Interruption of nonstimulatory short days with a brief light pulse during the dark phase was equally effective. This demonstrates that a circadian rhythm of photosensitivity could be responsible for photoperiodic responses. Pretreatment of sexually regressed fish with short days or low temperatures allowed the ovaries to respond to subsequent stimulation by long days and warm temperatures. The combination of short days and low temperatures produced the most rapid gonad response to warm long days. In the spring, fish were capable of spontaneous gonad recrudescence when held in constant darkness at 20 C. Also in the spring, low temperatures appeared to slow or prevent final maturation in the ovary while allowing for significant ovarian growth. Thus, low temperatures may facilitate gonad recrudescence by allowing the preliminary stages of ovarian development to occur while retarding the final maturation of the oocytes.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1984)113<452:PATIIT>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Serum gonadotropin hormone (GTH) concentrations were determined by radioimmunoassay in goldfish Carassius auratus subjected to short photophase and cold or warm temperature, or long photophase and warm temperature for various lengths of time in winter and spring. The effects of an outdoor pond regime, phase-shifting of the photoperiod and feeding times, warm temperature pulses, pinealectomy, blinding, and melatonin treatment on the daily cycles in serum GTH concentrations were investigated. Ovarian condition was assessed by histology to allow correlation with GTH. The GTH cycles detected in the laboratory were similar to the cycles found in fish kept in an outdoor pond under similar environmental regimes. In addition to photoperiod and temperature, the length of the acclimation period had an effect on the patterns of the daily cycles in serum GTH concentrations. Timing of daily peaks in serum GTH concentrations was shifted by shifting of the photoperiod and feeding times. Photoperiod and feeding entrained the daily cycle in serum GTH when the onset of light and first feeding were 4 hours apart but not when they were 10 hours apart. A pulse of warm temperature promoted fluctuations in GTH when the warmth was imposed during the day, but not when imposed during the night. Pinealectomy and blinding suppressed fluctuations in serum GTH concentrations under long photophase and warm temperature, but pinealectomy promoted fluctuations under short photophase and warm temperature. Melatonin, a pineal indoleamine, lowered the GTH peak when administered in the morning; however, no effect was detected from the afternoon injections. In most experiments, abolition of the daily fluctuations in serum GTH concentrations was correlated with smaller ovaries or ovarian atresia. The daily cycle in serum GTH promoted ovarian growth more than steady low or high serum GTH concentrations.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1984)113<458:DCOSGH>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The vertical distribution and swimming direction of 2-year-old smolted Baltic salmon Salmo salar, kept in circular tanks containing either fresh or brackish water, was monitored for a year. Fish in both groups were distributed in the upper part of a water column and moved with the current during the first part of the experiment, May to August. Salmon kept in brackish water continued this behaviour throughout the year whereas fish maintained in fresh water changed their behaviour drastically. From September, freshwater fish were distributed close to the bottom and tended to swim against the current. The following spring (April-May), fresh water kept fish again started to swim high in the water column, indicating a repetition of smolt behaviour. The results correspond well to the known behaviour of salmon in nature. Apparently, there is an interaction between alternative circannual programs in Baltic salmon; the selection of a specific program is suggested to be based in part on the environmental information the fish perceive.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1984)113<467:AIACOS>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The reproductive periodicity of the Atlantic silverside Menidia menidia was studied at two locations on the North Edisto River estuary in South Carolina during March-July 1976–1978. Spawning runs occurred in the upper intertidal zone and coincided precisely with daytime high tides. Time-series analysis of daily changes in the intensity of spawning runs revealed a fortnightly reproductive periodicity and indicated that the observed reproductive rhythmicity in Atlantic silversides may be mediated by a high-tide-sunrise cue that also occurs at fortnightly intervals. During the 1976 and 1977 reproductive seasons, there were highly significant correlations (P < 0.01) among the male gonadal index, the female gonadal index, and the occurrence of intermediate, maturing, and hydrated-egg stages of sexual development in females. The percentage of females with hydrated eggs was greatest on days when a high tide occurred within 1 hour after sunrise.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1984)113<472:RROTAS>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor