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1.
In this study we examined the endocrine mediation between environmental factors (temperature and photoperiod) and the brain–pituitary–gonadal
axis in females of pejerrey Odontesthes bonariensis. Changes in the expression of brain gonadotropin-releasing hormones (GnRHs) and gonadotropin (GtH) subunit [follicle stimulating-β
(FSH-β), luteinizing hormone-β (LH-β), glycoprotein hormone-α (GPH-α)] genes, plasma gonadal steroids [estradiol (E2) and testosterone (T)], gonadal histology, and gonadosomatic index (GSI) in adult females exposed to combinations of short-day
(8 h) or long-day (16 h) photoperiods and low (12°C) or high (20°C) temperatures after winter conditions (8 h light, 12°C)
were analyzed. Pejerrey females kept under the short photoperiod had low GSIs, and their ovaries contained only previtellogenic
oocytes regardless of the experimental temperature. In contrast, females exposed to the long photoperiod had high GSIs and
ovaries with vitellogenic oocytes at both temperatures. These fish also showed a significantly higher expression of sGnRH,
pjGnRH, cGnRH-II (the three different GnRH variants found to date in the pejerrey brain), FSH-β, LH-β and GPH-α genes and
plasma E2 levels than those at the shorter photoperiod. No significant changes were observed in plasma T levels. Based on these results,
we concluded that the increase in day length but not that of temperature triggers the maturation of pejerrey females after
the winter period of gonadal rest and that this occurs by an integrated stimulation of the various components of the brain–pituitary–gonad
axis. 相似文献
2.
Dorts J Grenouillet G Douxfils J Mandiki SN Milla S Silvestre F Kestemont P 《Fish physiology and biochemistry》2012,38(2):389-399
Climate change is predicted to increase the average water temperature and alter the ecology and physiology of several organisms
including fish species. To examine the effects of increased water temperature on freshwater fish reproduction, adult European
bullhead Cottus gobio of both genders were maintained under three temperature regimes (T1: 6–10, T2: 10–14 and T3: 14–18°C) and assessed for gonad
development (gonadosomatic index—GSI and gonad histology), sex steroids (testosterone—T, 17β-estradiol—E2 and 11-ketotestosterone—11-KT)
and vitellogenin (alkali-labile phosphoprotein phosphorus—ALP) dynamics in December, January, February and March. The results
indicate that a 8°C rise in water temperature (T3) deeply disrupted the gonadal maturation in both genders. This observation
was associated with the absence of GSI peak from January to March, and low levels of plasma sex steroids compared with T1-exposed
fish. Nevertheless, exposure to an increasing temperature of 4°C (T2) appeared to accelerate oogenesis with an early peak
value in GSI and level of plasma T recorded in January relative to T1-exposed females. In males, the low GSI, reduced level
of plasma 11-KT and the absence of GSI increase from January to March support the deleterious effects of increasing water
temperature on spermatogenesis. The findings of the present study suggest that exposure to elevated temperatures within the
context of climate warming might affect the reproductive success of C. gobio. Specifically, a 4°C rise in water temperature affects gametogenesis by advancing the spawning, and a complete reproductive
failure is observed at an elevated temperature of 8°C. 相似文献
3.
Chi‐Hoon Lee Sang‐Woo Hur Byeong‐Hoon Kim Kiyoshi Soyano Young‐Don Lee 《Aquaculture Research》2020,51(5):2084-2090
As a preliminary investigation into the effects of environmental factors on gonadal development using adaptive physiological characteristics, we examined the involvement of photoperiod and water temperature in the ovarian development of the red‐spotted grouper, Epinephelus akaara. During October 2014 (non‐breeding season), the photoperiod and water temperature were adjusted to 12L:12D and 18°C respectively. Every 3 weeks, daylight was increased as follows a 13L:11D and 14L:10D in the photo‐thermal treatment group, and the control group was maintained under natural conditions. After 9 weeks, water temperature was increased to 23°C in the photo‐thermal treatment group. In photo‐thermal treatment group, GSI increased significantly after 9 weeks (1.36 ± 0.19) and 12 weeks (3.31 ± 0.20) compared with the control group. At 12 weeks after photo‐thermal treatment, all fishes matured into ovaries containing late vitellogenic oocytes. The expression of FSHβ and LHβ mRNAs also increased significantly. However, in the control group, the ovarian development was maintained at an immature stage. Based on these results, we demonstrate that exposure to long photoperiod and high water temperature can induce the sexual maturation of immature red‐spotted grouper during the non‐breeding season. 相似文献
4.
A series of sixteen environmental experiments, conducted under controlled laboratory conditions during the refractory period in the reproductive cycle of the grey mullet, determined the effect of photoperiod and temperature on the vitellogenesis of intraovarian oocytes. Fish subjected to the natural light cycle and ambient water temperatures (24–26°C) served as controls. A classification of stages of vitellogenesis (I–V) is used to determine the percentage composition of oocytes for each fish at intervals throughout the experiment following sampling in vivo.Onset of vitellogenesis is timed by the environmental conditions. A retarded photoperiod, irrespective of preconditioning photoperiod, plays a dominant role in stimulating oocyte growth. Temperature regulates vitellogenesis towards functional maturity. The combination of retarded photoperiod (6L/18D) and constant temperature of 21°C is the most effective for the completion of vitellogenesis of oocytes to functional maturity.Regular injections of pregnant mare's serum gonadotropin (PMSG) at 1 IU/g body weight are effective in initiating vitellogenesis. 相似文献
5.
Ariel E. Valenzuela Victor M. Silva Alfredo E. Klempau 《Fish physiology and biochemistry》2006,32(2):113-120
The effects of artificial photoperiod regimes on reproductive patterns have been studied in several species, as have haematological parameters. However, information on how artificial photoperiods may affect blood components is scarce, especially under field conditions. We have assessed the effects of constant light [long day (LD) photoperiod: 24 h (light):0 h (dark)] on haematological parameters of cultured rainbow trout in Chile (Southern Hemisphere). In the initial stage (March up to June), two groups of fish were maintained under similar conditions and under the ambient (natural) photoperiod (NP). One group was then placed under the LD photoperiod regime for 2 months (June/July), following which it was returned to␣the NP (August–January); the control group remained under the NP throughout the experiment (March–January). All fish were assessed for haematological parameters and growth performance at various times during the experiment. During the initial stage, no differences were found between groups. However, at the end of the LD 24:0 period, the LD fish had increased haematocrit values and erythrocyte numbers and diminished mean corpuscular haemoglobin. After the LD fish had been returned to the NP, they developed secondary sexual characteristics and had a 40–44% decrease in the number of leukocytes. 相似文献
6.
Photoperiod plays a role in the regulation of reproduction in many fish. We examined the effectiveness of the long-afterglow
phosphorescent pigment LumiNova on the reproductive performance of the sapphire devil Chrysiptera cyanea, a tropical damselfish that reproduces under long-day conditions. During the breeding season, the experimental fish, but
not the control fish, were reared in aquaria covered with LumiNova sheets for 75 days under natural photoperiod and temperature.
At days 60 and 75 after onset of the experiment, the gonadosomatic index of experimental fish was higher than that of control
fish. Histological observations at 60 and 75 days revealed that the ovaries of experimental fish contained large oocytes laden
with yolk, whereas the control fish had few yolky oocytes at 60 days and mostly immature oocytes at 75 days. Spawning occurred
repeatedly in experimental fish, but not in control fish, throughout the study period. Because LumiNova sheets continue to
emit green light for some time after sunset, the extended light conditions probably contributed to active reproduction in
experimental fish. In conclusion, long-afterglow phosphorescent pigment can be used for energy-efficient aquaculture to regulate
the reproduction of fish, although its effect needs to be evaluated in different species. 相似文献
7.
The effect of extended photoperiods on growth and age at first maturity was investigated in 166 (79 females and 87 males)
individually tagged Atlantic halibut Hippoglossus hippoglossus and in 114 (50 females and 64 males) individually tagged turbot Scophthalmus maximus. The halibut were reared at 11 °C on four different light regimes from 10 February to 6 July 1996: simulated natural photoperiod,
(LDN), continuous light (LD24:0), constant 8 h light and 16 h darkness (LD8:16) and LD8:16 switched to continuous light 4
May 1996 (LD8:16–24:0). From 6 July 1996 to 9 February 1998 the LD24:0 and LD8:16–24:0 were reared together under continuous
light and the LDN and LD8:16 together under natural photoperiod. The turbot were reared at 16 °C on three different light
regimes: constant light (LD24:0), 16 h light:8 h darkness (LD16:8), or simulated natural photoperiod (LDN). After 6 months
on the different photoperiods, the turbot was reared together on LDN for approximately 12 months until first maturation. Juveniles
subjected to continuous light (halibut) or extended photoperiods (halibut and turbot) exhibited faster growth than those experiencing
a natural photoperiod or a constant short day. Moreover, when the photoperiod increased naturally with day-length or when
fish were abruptly switched from being reared on short-day conditions to continuous light, a subsequent increase in growth
rate was observed. This growth enhancing effect of extended photoperiods was more apparent on a short time scale in Atlantic
halibut than in turbot, but both species show significant long-term effects of extended photoperiods in the form of enhanced
growth. In both species lower maturation of males was seen in groups exposed to extended or continuous light compared to LDN
and this could be used to reduce precocious maturation in males leading to overall increase in somatic growth.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
8.
采用组织学方法系统研究了人工养殖条件下半滑舌鳎亲鱼卵巢的组织发育周年变化特征.结果表明,卵母细胞发育可分为6个时相,卵巢发育分为6期.卵巢不同发育时期都由不同类型的卵母细胞组成,半滑舌鳎为非同步分批多次产卵类型.周年发育过程中,6月龄前的鱼卵巢发育处于第Ⅰ期;9～12月龄卵巢可发育至第Ⅱ期;12月龄半滑舌鳎性腺可发育达到Ⅲ期,并一直保持至24月龄.3龄雌鱼达到性成熟,卵巢可发育至第Ⅳ期;随着水温和光周期的调控,卵巢发育进入成熟期(Ⅴ期),发生水合现象是卵母细胞成熟并准备排卵的信号;产卵结束后卵巢退化至第Ⅵ期,排出的卵母细胞退化吸收,以Ⅲ期卵巢越冬后,卵巢退化至Ⅱ期并持续至下一个繁殖周期.人工养殖条件下,卵巢内存在卵母细胞闭锁现象.性腺周年发育过程中,性腺指数(GSI)在性腺达到成熟期时达到峰值,产卵结束后性腺快速退化,GSI值各月份差异显著(P<0.05),亲鱼性腺重量在卵巢发育成熟过程中一直处于生长状态.亲鱼肝脏指数(HSI)在产卵前7～8月份(性腺达到成熟期前30 d左右)达到最大,表明7～8月份是性腺进行卵子发育、卵黄能量储备的重要时期,亲鱼在产卵前通过积极摄食储备体内能量,肝脏在卵母细胞卵黄积累方面具有重要的生理作用.肥满度(CF)值在繁殖盛期10～11月份达到最大,表现出与GSI类似的变化趋势. 相似文献
9.
Haematological parameters are often used as health status and stress indicators in fish. However, information on the effects
of artificial photoperiods on these parameters is scarce and ambiguous. The consequences of three different artificial photoperiod
regimes [light/day 12 h:12 h (LD 12:12) for 150 days as controls; LD 14:10 and LD 24:0, both for an initial 60 days, and then
LD 12:12 for the remaining 90 days] were evaluated in trout. In all fish the haemogram and the erythrocyte production index
(EPI) were assessed at days 7, 14, 30 and 60 (phase 1) and at days 90, 120 and 150 (phase 2). At the end of phase 1, photoperiods
LD 14:10 and 24:0 induced higher production of immature (late basophilic) erythrocytes (0.06–0.08 × 1012 cells/l, P < 0.05) and elevated EPI (young erythrocytes = 1.6 in LD 14:10, 2.25 in LD 24:0; late basophilic erythrocytes = 4.1–4.9 in
LD 14:10, 3.3 in LD 24:0) than in controls (late basophilic erythrocytes = 0.02–0.04 × 1012 cells/l; EPI young erythrocytes = 0.2–1.0; EPI late basophilic erythrocytes = 1.4–2.7). During phase 2, only reduced numbers
of lymphocytes and thrombocytes were observed at day 150 in the LD 14:00 group. An increase in the EPI (1.9) of control young
erythrocytes was found at day 150. 相似文献
10.
Peter Thomas Paul A. Copeland John A. Prentice 《Journal of the World Aquaculture Society》1994,25(2):214-224
Seasonal changes In oocyte growth and plasma estradiol, testosterone, thyroid hormones and vitellogenin levels were monitored in three captive adult female orangemouth corvina Cynoscion xanthulus subjected to a condensed (8 mo) seasonal cycle of photoperiod and water temperature. Plasma concentrations of estradiol and testosterone began to rise when temperature increased to 28 C and photoperiod to 15 h light (midsummer conditions). This was accompanied by elevated circulating levels of vitellogenin and the appearance of vitellogenic oocytes (diameter > 100 μm). Estradiol concentrations and mean oocyte size increased concurrently during late summer conditions and were maximum during fall conditions, approximately 8 wk after the beginning of ovarian recrudescence. In contrast, plasma levels of thyroid hormones did not show any distinct seasonal changes. Gonadally recrudesced females contained several size classes of vitellogenic oocytes. Injection of these fish with a luteinizing hormone-releasing hormone analog (LHRHa) caused maturation and spawning of the largest oocytes (mean diameter of follicles × 2500 μm). Another group of vitellogenic oocytes had been recruited into this size class by 2 wk after the end of spawning, which suggests that this species is capable of repeated spawning during the reproductive season. Injection of LHRHa resulted in increased plasma levels of gonadotropin and repeated spawning over several days. LHRHa-induced final oocyte maturation, ovulation and spawning were preceded by increases in plasma levels of two teleostean maturation-inducing steroids, 17α,20β, 21-trihydroxy-4-pregnen-3-one (20β-S) and 17α,20β-dihydroxy-4-pregnen-3-one (17α,20β-P4). The results provide preliminary evidence that oocyte growth is stimulated in orangemouth corvina subjected to an abbreviated seasonal cycle in captivity under midsummer photoperiod and temperature conditions and is associated with seasonal increases in plasma estradiol concentrations and vitellogenin production. However, the relative importance of 20β-S versus 17α, 20β-P4 in the control of final oocyte maturation in this species could not be determined from the results of the present study. 相似文献
11.
Photosynthetic activities of seedlings of Zostera marina were successively measured using a gas volumeter for 6 days at seven light (0–400 μmol photons/m2 per s) and 11 water temperature conditions (5–35°C). The seedlings were collected from mature plants (Ise Bay, central Japan),
and stored and cultured in incubators accurately controlled at each test temperature. The maximum gross photosynthesis (P
maxg) was recorded at an optimal water temperature of 29°C after 0 days. After 6 days, P
maxg appeared at 25°C and most plants cultured at 29–30°C bleached and withered after the drastic increase of light compensation
point (I
c). On the contrary, at 5–28°C, the photosynthetic activities either changed little (5–25°C) or recovered after a temporal
reduction (26–28°C); seedlings survived and looked healthy after being cultured for 6 days. The recovery was thought to be
an acclimation to tolerate higher water temperature. As a result, the critical upper water temperature for Z. marina seedlings was proposed as 28°C. The temperature was consistent with the previously reported maximum water temperature in
habitats around the southern boundary of Z. marina in the northern hemisphere. 相似文献
12.
The effects of different photoperiod regimes, and total darkness on day-night variations in hypothalamic serotonin (5-HT)
content and turnover index (TI), and monoamine oxidase (MAO) activity that occur exclusively during the gonadal preparatory
phase (February–March) were investigated in female Heteropneustes fossilis. Exposure of the fish to long photoperiods (16L:8D; light between 06.00–22.00h, for 40 days elevated both the midphotophase
and midscotophase values of 5-HT content and MAO, and abolished their day-night differences. The daily variations of 5-HT-TI
was further intensified by the treatment. Under short photoperiods (4L:20D; light between 18.00–22.00h for 40 days), there
was a significant decrease in both 5-HT content and TI, a reversal of the day-night variations of 5-HT content and MAO activity,
and loss of the 5-HT-TI pattern. In fish maintained in total darkness the day-night variations were not found and there was
a significant inhibition of 5-HT. Exposure of the fish to continuous light abolished the day-night variations of these correlates
and elevated their values at both intervals. When the LD cycle was reversed, there was a corresponding shift in the day-night
patterns. The gonadosomatic index (GSI) was significantly elevated in the long photoperiod and continuous illumination groups,
significantly decreased in the short photoperiod and total darkness groups, and unchanged in the reversed LD cycle regime.
The results indicate that the day-night variations of 5-HT and MAO are photoperiod-dependent and are controlled by the prevailing
LD cycle during the gonadal preparatory phase of the annual reproductive cycle. The photoperiod effects on the gonadal activity
may be mediated through the hypothalamic serotonergic system. 相似文献
13.
Yoshinori Sotoyama Saichiro Yokoyama Manabu Ishikawa Shunsuke Koshio Hiroshi Hashimoto Hiromi Oku Tadashi Ando 《Fisheries Science》2018,84(6):1063-1071
This study aimed to investigate the effects of a superoptimal temperature on growth, body composition, body size heterogeneity, and relationships among these factors in juvenile yellowtail. Fish (mean body weight?=?24 g) were tagged individually and reared for 70 days under two different water temperature regimes [optimal (25 °C) and superoptimal (30 °C)]. After rearing, fish reared at 30 °C showed lower survival, less food, feed and protein utilization, significantly lower growth performance, and a lower hepatosomatic index than fish raised at 25 °C. Variations in body indices among individuals were larger for fish reared at 30 °C than for fish reared at 25 °C. Mean whole body protein content was significantly lower in fish reared at 30 °C than fish reared at 25 °C. In addition, several glucogenic and/or aromatic amino acids were lower in fish reared at 30 °C than in fish reared at 25 °C. Whole body lipid levels tended to be lower in fish with lower body weight reared at 30 °C. These results suggest that fish raised at 30 °C will have lower growth performance, and lower concentrations of specific amino acids. Moreover, heterogeneity in body size and body lipid content is expanded by a superoptimal temperature. 相似文献
14.
To investigate the effect of water temperature on gamete maturation and gamete quality, European grayling (Thymalus thymallus) were held under different temperature regimes prior to spawning. Maturation of males and females and their gamete quality
depended strongly on temperature regime. The highest percentages of maturing fish and highest gamete quality were obtained
under a creek water temperature regime with natural seasonal fluctuations. In warmed creek water (3–4°C), at a constant temperature
of 8–9°C, and under an abruptly increasing temperature, regime maturation rates and gamete quality were reduced. The effect
was more pronounced in females than in males. The spawning dates of different wild Austrian grayling populations were also
correlated with water temperature data collected during the last 10–15 years. The mean spawning date expressed as the number
of days from 21 December until spawning ranged from 98 to 111 days for lower elevation populations, while it was considerably
delayed for an alpine population. All populations spawned at water temperatures of 5.5–7.2°C. Regression analysis indicated
that spawning date correlated with (1) the overall mean water temperature from 21 December until spawning, (2) the mean water
temperature during both the last 10 days and 15 days before spawning, and (3) the difference between mean January temperature
and that of the last 15 days before spawning. The regression functions indicate that an increase in water temperature from
21 December to spawning of 1°C advances spawning by 5? days, and an increase of 1°C in the last 10–15 days advances spawning
by 3? days. 相似文献
15.
Zhongming Zheng Chunhua Jin Mingyun Li Peifeng Bai Shuanglin Dong 《Aquaculture International》2008,16(6):581-589
The metabolic responses of the juvenile Miichthys miiuy in terms of oxygen consumption and ammonia excretion to changes in temperature (6–25°C) and salinity (16–31 ppt) were investigated.
At a constant salinity of 26 ppt, the oxygen consumption rate (OCR) of the fish increased with an increase in temperature
and ranged between 133.38 and 594.96 μg O2 h−1 g−1 DW. The effect of temperature on OCR was significant (P < 0.01). Q10 coefficients were 6.80, 1.41, 1.29 and 2.36 at temperatures of 6–10, 10–15, 15–20 and 20–25°C, respectively, suggesting that
the juveniles of M. miiuy will be well adapted to the field temperature in the summer, but not in the winter. The ammonium excretion rates (AER) of
the fish were also affected significantly by temperature (P < 0.01). The O:N ratio at temperatures of 6, 10, 15 and 20°C ranged from 13.12 to 20.91, which was indicative of a protein-dominated
metabolism, whereas the O:N at a temperature of 25°C was 51.37, suggesting that protein-lipids were used as an energy substrate.
At a constant temperature of 15°C, the OCRs of the fish ranged between 334.14 (at 31 ppt) and 409.68 (at 16 ppt) μg O2 h−1 g−1 DW. No significant differences were observed in the OCR and AER of the juveniles between salinities of 26 and 31 ppt (P > 0.05). The OCR and AER at 16 ppt were, however, significantly higher than those at 26 and 31 ppt (P < 0.05), indicating salinity lower than 16 ppt is presumably stressful to M. miiuy juveniles. 相似文献
16.
Patrick Hainfellner Rafael Yutaka Kuradomi Thiago Gonalves de Souza Rafael Tomoda Sato Daniel Guimares Figueiredo‐Ariki Guilherme Antnio de Freitas Luciano Queiroz Wagner C. Valenti Patricia Moraes Valenti Wei Ge Sergio Ricardo Batlouni 《Aquaculture Research》2019,50(11):3382-3391
We evaluated the annual process of oocyte and ovarian development of the planktivorous Amazonian catfish, the mapará (Hypophthalmus marginatus), aiming to support captive reproduction for domestication. A total of 149 females were captured from the Tocantins River at the Tucuruí Dam (3°49'55"S, 49°39'9"W) in 13 sampling events. For each individual, we evaluated ovary histology and plasma steroid concentrations. Two annual reproductive cycles, with similar characteristics, including a long period of rest, a short vitellogenic stage and a well‐defined spawning season from November to March, were described. A 17β‐estradiol (E2) rise and a 17α,20β‐dihydroxy‐4‐pregnen‐3‐one (DHP) peak were associated with vitellogenesis and spawning season, respectively, in the first cycle but not in the second reproductive cycle. In conclusion, the studied species presents a reproductive cycle similar to that of other migratory total spawners; however, unusually for this group of fish, there were three (but not two) batches of vitellogenic oocytes in “in maturation” and “mature” stage ovaries, pointing to the possibility of more than one spawn during the spawning season. 相似文献
17.
To investigate the interactive effects of temperature and photoperiod on the growth performance, feeding parameters and muscle growth dynamics in juvenile Atlantic halibut (Hippoglossus hippoglossus L.), a total of 1212 juvenile halibut, including 383 tagged fish (mean initial weight of tagged individuals: 17.6 ± 0.3 g SE), were reared under a simulated natural light regime for Bergen (60°25′N) or continuous light at 9, 12 and 15 °C from 3 December 2007 until 11 March 2008. The mean weight and growth rate were significantly higher at 12 and 15 °C than at 9 °C. In addition, significantly higher mean weight and growth rate were observed in halibut reared under continuous light at a low temperature, indicating an interactive effect of temperature and photoperiod on growth performance. No effect of temperature or photoperiod was found with respect to feed conversion efficiency, whereas a higher feed consumption at increasing temperature and a higher overall daily feeding rate at continuous light at a low temperature were observed. Indications of continuous light having a stronger effect at low temperatures on muscle growth dynamics were found. A difference in the size class distribution of fibre diameter was found between photoperiod treatments at 9 °C, suggesting that continuous light resulted in elevated hypertrophic growth at low temperature. This may suggest that the increased growth rate found at continuous light at 9 °C may be a result of hypertrophic growth in juvenile halibut. 相似文献
18.
The present paper describes the growth properties of juvenile Atlantic cod (Gadus morhua) reared at 7, 10, 13 and 16 °C, and a group reared under “temperature steps” i.e. with temperature reduced successively from
16 to 13 and 10 °C. Growth rate and feed conversion efficiency of juvenile Atlantic cod were significantly influenced by the
interaction of temperature and fish size. Overall growth was highest in the 13 °C and the T-step groups but for different
reasons, as the fish at 13 °C had 10% higher overall feeding intake compared to the T-step group, whereas the T-step had 8%
higher feeding efficiency. After termination of the laboratory study the fish were reared in sea pens at ambient conditions
for 17 months. The groups performed differently when reared at ambient conditions in the sea as the T-step group was 11.6,
11.5, 5.3 and 7.5% larger than 7, 10, 13 and 16 °C, respectively in June 2005. Optimal temperature for growth and feed conversion
efficiency decreased with size, indicating an ontogenetic reduction in optimum temperature for growth with increasing size.
The results suggest an optimum temperature for growth of juvenile Atlantic cod in the size range 5–50 g dropping from 14.7 °C
for 5–10 g juvenile to 12.4 °C for 40–50 g juvenile. Moreover, a broader parabolic regression curve between growth, feed conversion
efficiency and temperature as size increases, indicate increased temperature tolerance with size. The study confirms that
juvenile cod exhibits ontogenetic variation in temperature optimum, which might partly explain different spatial distribution
of juvenile and adult cod in ocean waters. Our study also indicates a physiological mechanism that might be linked to cod
migrations as cod may maximize their feeding efficiency by active thermoregulation. 相似文献
19.
北太平洋长鳍金枪鱼卵巢的发育特征 总被引：1，自引：0，他引：1
根据2013年10月–2014年2月在北太平洋海域(29°08′~41°08′N,163°50′~144°19′W)采集的364尾长鳍金枪鱼的卵巢样本,利用组织学分析,详细描述了长鳍金枪鱼卵巢、卵细胞的发育阶段。结果显示,北太平洋长鳍金枪鱼卵巢内同时存在不同时相的卵细胞,为分批产卵类型;组织学上,长鳍金枪鱼的卵细胞发育过程分为6个时相,卵巢发育过程分为6个时期;卵巢成熟指数在成熟期为Ⅰ~Ⅴ期时逐渐增大,在Ⅵ期时减小;北太平洋长鳍金枪鱼产卵高峰为12月中旬和1月初,其卵巢成熟指数随纬度的升高呈递减趋势,随经度变化规律不明显。研究表明,通过对北太平洋长鳍金枪鱼卵巢的发育特征的分析与探讨,可为北太平洋长鳍金枪鱼的资源状况评估及渔业可持续发展提供生物学信息。 相似文献
20.
The combined effect of temperature and photoperiod on the growth of juvenile Atlantic halibut Hippoglossus hippoglossus (initial weight 11.6 g) was investigated under different temperature (6 °C and 12 °C) and photoperiod (continuous light and simulated natural photoperiod) combinations by studying the effects on fish weight, specific growth rate (SGR), feed consumption (F%), feed conversion (FCE) and oxygen consumption and ammonia excretion under routine and fasting conditions. SGR was greater at the higher temperature, and growth was faster under continuous light than under natural photoperiod, irrespective of temperature, SGRs being 0.83% and 0.98%, and 1.61% and 1.71% at 6 °C and 12 °C respectively. The weight data revealed a significant interaction between temperature and light, and provided evidence of a stronger growth‐enhancing effect of continuous light at the lower temperature. F% increased with temperature but was independent of photoperiod, whereas FCE was higher among fish exposed to continuous light, irrespective of temperature. Independently of photoperiod, oxygen consumption and ammonia excretion increased with temperature, but the differences in these rates in relation to photoperiod became more pronounced at the lower temperature, where continuous light gave the highest rates. Higher oxygen consumption during darkness suggested that light may suppress activity in halibut. It was proposed that reduced activity and anabolic effects of photoperiod contribute to explain the increased growth and growth efficiency in fish subjected to continuous light. 相似文献