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Effect Of Photoperiod On Plasma Thyroxine Hormone Level Of Mirror Carp (Cyprinus Carpio) Raised At A Low Water Temperature In A Controlled Environment


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The objective of this study was to examine the effects of various lighting regimes on the plasma thyroxin hormone (T4) level of mirror carp (Cyprinus carpio). The carp were kept at the low temperature of 9°C to eliminate any influence of water temperature on feed intake, growth, and the hormone level. Treatments were 8 h light:16 h dark, 12 h light:12 h dark, and 16 h light:8 h dark. Plasma thyroxin levels were measured every four weeks for 12 weeks. The levels were significantly higher (p<0.05) in the groups exposed to 8 or 12 h light than in the group exposed to 16 h. The T4 levels significantly dropped with time in all photoperiods.
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Zvi Yaron Dept. of Zoology
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The Israeli Journal of Aquaculture – Bamidgeh 57(1), 2005, 19-24. 19
Sükriye Aras Hisar1, Birsen Kirim1, Serdar Bektas1, Konca Altinkaynak2, Olcay Hisar1*
and Telat Yanik1
1Atatürk University, Agriculture Faculty, Department of Aquaculture, Erzurum, Turkey
2Atatürk University, Medical Faculty, Department of Biochemistry, Erzurum, Turkey
(Received 7.5.04, Accepted 18.10.04)
Key words: mirror carp, photoperiod, thyroxin hormone, weight gain
The objective of this study was to examine the effects of various lighting regimes on the plasma
thyroxin hormone (T4) level of mirror carp (Cyprinus carpio). The carp were kept at the low tem-
perature of 9°C to eliminate any influence of water temperature on feed intake, growth, and the
hormone level. Treatments were 8 h light:16 h dark, 12 h light:12 h dark, and 16 h light:8 h dark.
Plasma thyroxin levels were measured every four weeks for 12 weeks. The levels were signifi-
cantly higher (p<0.05) in the groups exposed to 8 or 12 h light than in the group exposed to 16
h. The T4levels significantly dropped with time in all photoperiods.
Thyroid hormones play important roles in the
physiology of teleost fishes, i.e., in the regula-
tion of metabolism (Gupta and Thapliyal,
1991; MacKenzie et al., 1998), growth and
development (Power et al., 2001; Gavlik et al.,
2002), energy utilization (Leatherland, 1994),
sexual maturation (Monteverdi and Di Giulio,
2000; Mercure et al., 2001), breeding cycle
(Volkoff et al., 1999), migration (Matty, 1985),
and electrolyte and water metabolism (Peter
et al., 2000).
Physiological and morphological charac-
teristics of fish continually adjust to the ever-
changing aquatic environment. The circannu-
* Corresponding author.
Tel: +90-442-2313482; fax: +90-442-2360948; e-mail:
al rhythms of hormones seem to be closely
associated with circannual variations in ambi-
ent temperature, day length, and gonadal
steroids (Pavlidis et al., 2000).
Developmental and maturational events
are dominated and coordinated by seasonal
changes in photoperiod, temperature, food
supplies, rainfall, etc. (Porter et al., 1998;
Sánchez–Vázquez et al., 2000). Photoperiod
and temperature are generally considered the
most important factors. Recent data suggest
that genotype, hormones, and physiological
conditions are equally important endogenous
regulators of growth (Dutta, 1994).
Fish growth and food conversion are
improved by increasing the photoperiod
(Gross et al., 1965). Water temperature is
also correlated to food intake, being high in
the spring and summer and relatively lower
during the winter (Larsen et al., 2001).
Changes in temperature and food consump-
tion cause dynamic changes in the seasonal
profiles of many physiological parameters,
including growth rate and plasma thyroxin (T4;
Tiitu and Vornanen, 2003).
In Atlantic salmon, thyroid hormone pro-
duction reaches a maximum in summer when
the long period of light stimulates growth and
plasma T4levels without affecting T3
(McCormick et al., 1987). Low levels of thyroid
hormones are found in fish during winter when
the light period is short (Samejima et al.,
2000). On the other hand, Brown (1988)
reported that a short day length or complete
darkness stimulated the thyroid gland in fresh-
water and euryhaline species.
Most of the above studies were concerned
with seasonal fluctuations in growth or thyroid
hormones while some dealt with the optimum
temperature for growth or thyroid hormones.
We investigated whether different photoperi-
ods affect the plasma T4level of mirror carp at
a constant low temperature (9°C).
Materials and Methods
Animals. The study was conducted in the
Central Laboratory at the Aquarium Fish
Rearing Facility of the Fisheries Department
of the Agricultural Faculty at Atatürk
University with mirror carp obtained from the
Research and Extension Center of the
Fisheries Department.
Photoperiod experiments. The carp were
randomly sorted into three 70-l circular fiber-
glass tanks (45 x 45 cm) with a constant water
flow of 1.5 l/min of aerated dechlorinated tap
water at a density of 10 fish per tank. Three
photoperiods were tested in triplicate for a
total of nine tanks, i.e., 30 fish in each regime.
Mean weights were 63.06±3.83 g, 62.40±3.54
g, and 61.96±3.49 g, respectively for the three
Fish were acclimated for one week at 12 h
light:12 h dark. Then the photoperiods were
switched to short (8 h light:16 h dark, lights on
at 09:00), medium (12 h light:12 h dark, lights
on at 06:00), or long (16 h light:8 h dark, lights
on at 04:00) for 12 weeks at a constant water
temperature of 9°C.
The fish were fed a daily ration at 1% of
their live body weight. Feeding times were
centered in the middle of the light period.
Growth was expressed as mean weight over
the duration of the study and as mean weight
gain (% of the initial weight).
Blood sampling. Every four weeks, the fish
were captured, anesthetized in MS-222 (200
mg/l) during the scotophase, and individually
weighed. At the same time, blood samples
were obtained from the caudal vasculature of
each carp with a heparinized syringe. The
blood samples were kept on ice for up to 30
min until the plasma was separated by cen-
trifugation. Plasma samples were stored at
–80°C until analysis. Plasma T4 concentra-
tions were determined according to the
method of Dickhoff et al. (1982).
Statistics. All data were subjected to a
one-way analysis of variance followed by
Duncan’s multiple-range test to determine sig-
nificant differences among the regimes at the
0.05 level. Results are presented as means ±
standard deviation.
There were no significant differences in weight
gain among treatments (Fig. 1). Plasma T
levels were significantly higher in the groups
exposed to 8 or 12 hours of light than in the
group exposed to 16 (Fig. 2). Plasma T
Hisar et al.
21Effect of photoperiod on plasma thyroxine hormone level of mirror carp
significantly dropped with time in all three pho-
toperiods. At 12 weeks, weight gain dropped
4.78±5.11%, 7.57±1.51%, and 8.72±1.37%
while plasma T
dropped 12.1%, 15.8%, and
66.9% in the 8:16, 12:12, and 16:8 photoperi-
ods, respectively.
Despite the fact that the fish were fed at a ratio
of 1% of their body weight daily, they did not
grow at the low temperature of 9°C. Reduced
growth at this temperature is expected, due to
bioenergetic considerations (Hepher, 1988).
Fig. 2. Plasma thyroxin hormone (T4) of mirror carp kept at 8 h light:16 h dark, 12 h light:12 h dark, or
16 h light:8 h dark for twelve weeks at a low water temperature (9°C).
Fig. 1. Growth of mirror carp kept at 8 h light:16 h dark, 12 h light:12 h dark, or 16 h light:8 h dark for
twelve weeks at a low water temperature (9°C).
50 4812
8:16 LD 12:12 LD 16:8 LD
0.3 4812
8:16 LD 12:12 LD 16:8 LD
Body wt (g)
Thyroxin (ng/dl)
Similar to our findings, reduction in growth was
reported in trout kept at a low water tempera-
ture of 2.5°C (Larsen et al., 2001).
Although no significant differences were
observed in the present study with respect to
weight gain, it has been reported that photope-
riod and temperature affect growth in some
species. Boehlert (1981) showed that 16 h
light:8 h dark enhanced growth in Sebastes
diploproa compared to 12:12, and is probably
related to a lower metabolic rate. Gilthead
seabream raised in longer light periods (in an
experiment testing 8:16, 12:12, 16:8, 24:0, and
) grew better (Silva-
Garcia, 1996). Boeuf and Le Bail (1999) report-
ed that water temperature ranges from less
than 10°C (December-February) to as high as
20°C (June-August); thus, the fluctuation in
temperature also affects the growth rate.
Multiple mechanisms undoubtedly are involved
in promoting tolerance to low temperatures. In
goldfish, for example, acclimation to tempera-
tures below 10°C evokes a highly regulated
reduction in the metabolic rate, membrane
phospholipid reorganization, and alterations in
enzyme-substrate affinity relative to warm-
acclimated individuals (Ganim et al., 1998).
In fish, the secretion of thyroid hormones
is influenced by photoperiod, temperature,
and food intake (Cyr et al., 1998; Tiitu and
Vornanen, 2003). Food intake depends on
temperature and is high in spring and summer
when light effects better food conversion effi-
ciency and, thus, better growth (Boeuf and Le
Bail, 1999). Contrary to the effects on growth,
it is difficult to distinguish how photoperiod
affects the thyroid hormone level. We raised
the carp in a low water temperature to assure
that any fluctuation in thyroid level could not
be attributed to an increased feed intake
resulting from a warmer environment.
Differences in T4 level could result only from
differences in the photoperiod. Indeed, we
found that T4levels were significantly reduced
by a longer period of light throughout the
study period.
Similarly, Larsen et al. (2001) reported
that during the winter, when day lengths are
short and temperature is low, T4levels are rel-
atively unaffected by manipulations in feeding
and temperature compared with insulin or
insulin-like growth factor-I (IGF-I) and sug-
gested that photoperiod has a more signifi-
cant effect on the plasma profile of T4than
temperature or ration. However, the 8:16 and
12:12 treatments significantly differed from
the 16:8 treatment, showing that low water
temperature had a lesser impact on T4in a
short photoperiod than in a long photoperiod.
In other words if the water temperature had
been optimum, fish exposed to longer periods
of light would have grown better (Silva-Garcia,
1996; Boehlert, 1981) and thyroxin secretion
would have increased. Similarly, Brown and
Stetson (1985) showed that 14 h light
increased and 8 h light decreased the nega-
tive feedback sensitivity of the hypothala-
mus–pituitary axis to TH in killifish Fundulus
heteroclitus. They proposed that such a pho-
toperiod-induced change could aid in the
year-round maintenance of thyroxin levels
necessary for seasonal adaptation and sur-
vival. Eales and Fletcher (1982) also
observed seasonal changes in plasma TH
levels in laboratory and wild fish while Osborn
and Simpson (1978) obtained seasonal varia-
tions in plasma circulating T3and T4, with
maxima reached in winter and summer.
Obviously, these changes, even if related to
light as in the present study, can also be
linked to temperature changes as mentioned
in the above studies.
There were no significant differences in
growth while the T4value was much lower at
16:8. These results suggest that future aqua-
culture studies, especially off-season studies,
should not be based on a photoperiod of 16
light:8 dark. Further studies should be con-
ducted at optimum and high temperatures to
test various photoperiods in other fish
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Hisar et al.
... Similar morphological pigmentation differences were reported by Mashood et al. [20], when they observed that fish cultured in total darkness 00L: 24D had darker skin colouration than those in 12D:12L. This could be due to physiological response of the fish in the dark in increasing the simulation and production of melatonin [21]. Fish species that are reared under continuous darkness or light usually become adapted to the prevailing environmental conditions especially photoperiods; thus, they live with them. ...
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Environmental factors are known to influence growth and survival of aquatic organisms. Varying intensities of light can be of great advantage to catfishes. This research investigated the effects of photoperiod regimes on growth performance of Heterobranchus bidorsalis fingerings under controlled environment. A total of ninety (90) samples of the fish were acclimated for a period of 14 days during which they were fed to satiation twice daily. The experimental set-up consists of three treatments 3 replicates in each case. Treatment 1 is the control; 12 hours light and 12 hours dark, treatments 2 and 3 were subjected to 6 hours light and 24 hours total darkness, respectively with each tank stocked with 9 fish samples. The aquarium tanks were routinely placed in a simulated dark room and subsequently natural light in accordance to the duration of exposure desired for a period of 12 weeks. The physico-chemical parameters of the test media were taken according to standard methods. The growth parameters (lengths and weight) of the fish were taken on a weekly basis and the varying morphological pigments were noted at the end of the experiment. The weight gain and specific growth rate were also calculated. The resulting data were subjected to one way analysis of variance. From the results: The highest growth performance of the fish was recorded in T3, followed by T1 while lowest growth performance was recorded in T2. Better feeding efficiency was also influenced by photoperiods as highest feeding rate was recorded in T3. Changes in body pigmentation was more prominent in T3 as H.bidorsalis fingerlings exposed to this regime became black and darker in appearance in comparison to T1 samples which were lighter in complexion. Consequently, it is believed that subjecting H.bidorsalis fingerlings to 00L: 24D photoperiod regime by fish farmers can lead to improved farm yield and profits to the farmers.
... gariepinus) that were reared under total darkness (0L:24D), corroborating the present study. They predicted that the dark skin coloration could be due to the physiological response of the fish under completely dark condition which might increase the stimulation and production of melatonin (Hisar et al., 2005;Leclercq et al., 2010). In red porgy (Pagrus pagrus), fish kept in brighter light showed maximal pallor because of concentration of pigment cells in their skin (Rotllant et al., 2003). ...
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Light and shelter are very important ecological factors that can affect many traits of fish. Therefore, a study was conducted to explore the effect of light and shelter on some phenotypic traits of stinging catfish (Heteropneustes fossilis Bloch, 1794). During experiment, equal‐sized juveniles (mean ± SE: 9.04 ± 0.09 cm) were collected and reared in aquariums dividing into four treatment groups, such as T1 (0L:24D without pipe), T2 (0L:24D with pipe), T3 (12L:12D without pipe) and T4 (12L:12D with pipe). Each treatment had 36 fish, which were randomly distributed into three replications. The fish were kept up to 120 days, and then, the growth performance and skin colour were analysed. The results showed that both lighting and shelter conditions as well as their interactions had significant effects on some traits expression. The analyses revealed that lighting condition significantly influenced body area, head width and skin coloration, while shelter condition significantly affected total and standard length, body area, and their interaction showed significant effects on body area, head width and anal fin length. Thus, this study indicates that stinging catfish show better growth performance and colour patterns especially in dark and sheltered conditions which could be recommended for the successive production of this highly priced fish species.
... The improved growth performance of Tor putitora fry kept in longer periods of light might be due to the functioning of the pineal gland. The pineal gland is the major endogenous time-keeping system in teleosts and its secretion (melatonin) is reduced during periods of illumination (Hisar et al., 2005). When the photoperiod rapidly increases, plasma growth hormones levels also increase (McCormick et al., 1995). ...
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The effect of photoperiod on the growth, feed conversion efficiency, and survival of mahseer (Tor putitora) fry and fingerlings was investigated in two simultaneous experiments. In the first experiment, triplicate groups of 30 fry (0.27±0.01 g) were stocked in 100-l plastic tubs. A flow-through system with aerators was used to maintain the optimum dissolved O2 level. The fish were exposed to one of four photoperiods (18 h light:6 h dark, 12 h light:12 h dark, 6 h light:18 h dark, and the natural photoperiod of 10 h light:14 h dark). The fry were fed a 45% protein diet at the satiation rate of 5% of body weight for 90 days in laboratory conditions. The best weight gain, specific growth rate, feed conversion efficiency, and survival were achieved in 18L:6D treatment. Fry performance was significantly retarded in the 6L:18D treatment. In the second experiment, triplicate groups of eight fingerlings (6.08±0.03 g) were stocked in 100-l tubs and exposed to the same photoperiods as in the first experiment. The fingerlings were fed a 38% protein diet at the rate of 5% body weight for 90 days. The growth performance of the fingerlings was not significantly affected by photoperiod. Results show that Tor putitora fry, but not fingerlings, reared in lab conditions are significantly affected by photoperiod regime.
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Sixty juveniles of the African catfish, Clarias gariepinus (Burchell), were reared in triplicate under three different photoperiods: 24 h total darkness (24D:0L); 24 h total light (24L:0D); 12 h darkness and 12 h light (12D:12L). The latter served as the control in order to investigate the effects of light duration on the growth, body coloration, and feed conversion efficiency of the juveniles. Water quality in the tanks was also measured. Significant (P < 0.05) increases in body weight, specific growth rate, and food conversion efficiency were recorded among the fish cultured under 24D:0L, followed by 24L:0D, while those under 12D:12L showed the least growth increase. The high growth increase recorded in the 24D:0L was attributed to better food conversion efficiency and the suppression of swimming activity, aggression, and stress in the dark. All these enabled more energy to be converted to body weight. The body coloration of these fishes was also darker than in the other photoperiods. This was due to the physiological response of the fish in the dark to increase the stimulation and production of melatonin. The simple, low-cost technique of a 24D:0L photoperiod should be applied to ponds in order to achieve faster growth of this fish in less time.
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Atlantic salmon (Salmo salar) were subjected to artificial photoperiods to determine the manner and extent of photoperiod control of the parr–smolt transformation. Exposure to continuous light (L24) at first feeding and maintained throughout the rearing period inhibited increases in salinity tolerance and gill Na+,K+-ATPase activity that occurred in spring in fish raised under simulated natural photoperiod (SNP). Fish reared under continuous light and returned to SNP in October (L24OCT) underwent normal increases in salinity tolerance and gill Na+,K+-ATPase activity, whereas those returned in December (L24DEC) underwent delayed and intermediate increases. Plasma thyroxine peaks occurred simultaneously in all groups but were diminished in the L24 and L24DEC groups. Plasma 3,5,3′-triiodo-L-thyronine levels were not affected by any photoperiod treatment. Inhibition of the parr–smolt transformation decreased the potential for growth in seawater. In spite of changes in the timing of the transformation induced by photoperiod treatment, salinity tolerance and gill Na+,K+-ATPase activity were strongly correlated; correlation between changes in salinity tolerance and plasma thyroid hormones were, by comparison, weak. The results demonstrate that continuous light applied early in ontogeny and maintained throughout the rearing period inhibits osmoregulatory changes associated with parr–smolt transformation, whereas increasing day length during winter–spring stimulates transformation.
The effect of photoperiod on the growth of juvenile gilthead seabream (Sparus aurata) was analyzed. Fish (24.8±2.5 g initial weight) were reared under five photoperiod regimes (Light/Dark): 24L/0D, 16L/8D, 12L/12D, 8L/16D and natural (control). A direct relationship was found between the specific growth rate (SGR) and the number of light hours. Analysis of weight-time curves showed three types of growth: 24L/0D and 16L/8D (SGR=0.01), 12L/12D and natural (SGR=0.009) and 8L/16D (SGR=0.008). After 220 days, fish kept under 24L/0D and 16L/8D were 26% heavier than the control. Under 12L/12D, fish had the same final weight as the control. Under 8L/16D, they were 17% lower than the control. Fish were fed ad libitum twice a day. Under the long photoperiod (16L/8D) the daily feeding rate and food conversion index were 14% and 21% lower than in the control, and gross efficiency was 24% higher. Photoperiod manipulation could be a simple means for increasing the gilthead seabream growth rate and reducing food conversion rates.
Hormones play a central role in the regulation of growth and nutrient utilization in fish. Consequently, fish endocrine systems are sensitive to alterations in nutrient intake. Procedures routinely employed in the development of diets and feeding protocols for cultured fish have pronounced effects on endocrine systems. We review the evidence that alterations in ration level (including food restriction and food deprivation), diet composition, photoperiod, and feeding time influence the most intensively-studied fish metabolic hormones: thyroid hormones, pancreatic hormones, and hormones of the growth hormone–insulin-like growth factor axis. Whereas effects of these dietary manipulations on total circulating hormone levels are commonly examined, nutrient intake may also influence hormone transport in blood, activation in peripheral tissues, receptor binding, and neuroendocrine pathways regulating hormone secretion. Information on the cellular and molecular mechanisms through which nutrients influence endocrine systems is still needed. Significant new information about the regulation of endocrine function can be derived from nutritional studies currently employed in aquaculture for the development of diets. Additional information on the influence of nutrients on endocrine function is essential for the design and interpretation of hormone supplementation studies, and should eventually allow development of feeding strategies which promote anabolic hormone production.
Both yearling and underyearling (zero-age) coho salmon in fresh water showed spring- and/or summer increases in plasma thyroid hormone concentrations. The peak in plasma thyroxine (T4) was larger and occurred earlier during the spring in yearling fish compared to zero-age fish. Both groups had similarly elevated plasma triiodothyronine (T3) during the summer months. Groups of yearling and zero-age fish transferred serially to seawater net-pens showed differential rates of survival in seawater. In the zero-age fish, the greatest survival seemed coincident with the progression of the elevation of plasma T3 in fish in fresh water. Success in seawater of yearling fish correlated with the progression of the plasma peak of T4 in fish in fresh water.Peaks of thyroid hormones were also observed in chinook salmon and steelhead trout in fresh water. Although the survival of the chinook salmon in seawater net-pens was comparable to that of coho salmon, steelhead trout showed unexpectedly poor survival in seawater.These data suggest that analysis of changes in plasma thyroid hormones provides useful information regarding the optimal time to transfer coho salmon from fresh water to seawater. Whether this information can be applied in a similar manner to other species of salmonids requires further investigation.
Seasonal changes in plasma concentrations of L-thyroxine (T4) and 3,5,3′-triiodo-L-thyronine (T3) were measured by radioimmunoassay for flounder bled shortly after capture (field fish) or after 7 days retention in the laboratory at seasonal temperatures and photoperiods (laboratory fish).In field fish plasma T4 was highest from April to June and lowest from November to February, whereas plasma T3 was highest from September to January and lowest in May to June. T4/T3 molar ratios increased markedly from March to June and fell to very low values during July to early February.Laboratory fish showed generally similar seasonal patterns, except that for most of the year their T4 levels were consistently higher and T3 levels consistently lower than their field counterparts, resulting in much higher T4/T3 ratios in plasma of laboratory fish.The above seasonal trends are discussed in relation to environmental and physiological parameters and stress.
Four 6-week experiments were conducted to evaluate the effect of photoperiod on growth (total length and weight), food consumption, and food conversion efficiency by green sunfish. Fish were held at constant temperatures in light-tight aquaria under four photoperiods (8-hr constant; 16-hr constant; variable, increasing from 8 to 16 hr; and variable, decreasing from 16 to 8 hr).Growth, food consumption, and food conversion efficiency were all influenced by photoperiod. Food consumption varied directly with the amount of light to which fish were exposed. Fish growth and food conversion efficiency were closely correlated and were generally highest in the increasing, lowest in the decreasing, and intermediate in the two constant photoperiods, but higher in the longer daylength. The results suggest that photoperiod influences growth through increasing conversion efficiency and also possibly through stimulating food consumption.Varying daylength exerts a greater influence on fish growth than a constant daylength. Increasing photoperiod stimulates growth and decreasing photoperiod inhibits growth. This result suggests that the lack of growth of warmwater fish in fall when water temperatures and average daylength correspond to those of spring is largely due to the influence of decreasing daylength.