© 2002 Adhartho
Utiah Posted 2 December,
2002
Individual Paper
Science Philosophy (PPs 702)
Graduate Program
Institut Pertanian Bogor
November 2002
Instructors:
Prof. Dr.Ir. Rudy C. Tarumingkeng (Principal)
Prof Dr Ir
Zahrial Coto
Dr Bambang Purwantara
GONADAL
MATURATION OF ASIAN CATFISH IN CAPTIVITY WITH STAGNANT WATER POND SYSTEM
By :
C 061020051/AIR
(e-mail : utiah_fish@yahoo.com)
Since the Asian catfish (Pangasius hypophthalmus) has a high economic value both for consumption and ornamental fish, studies to promote and develop its culture in captivity become highly important 3).
In nature, Asian catfish can reach for more than 24 kg weight, and more than one meter in length. In addition, this fish have high resistance to disease and very tolerant to changes in chemical and physical water conditions so that make it easier to care.8)
Fingerlings of the fish usually available in a limited period since Asian catfish spawns once a year in rainy season from October to March.2) Artificial spawning of this fish with hormonal manipulation has been conducted. Hormones that are often used include combination of HCG (Human Corionic Gonadotropin) and Carp Pituitary Extract (CPE). Other hormone used are GnRH, and a combination of PMSG and HCG.1) But artificial spawning technique with hormonal manipulation always face obstacles because the physiological condition of fish was neglected.
Naturally, fish gonad development is influenced by gonadotropic hormone produced by pituitary as a response of hypothalamus to environmental cues such as water temperature, fluctuation of water level, rainfall. Generally, Asian catfish was mature in the rainy season from October-April. While in the Asian catfish,5) annual cycle of gonad development could be divided in three periods. Spawning period (May-August), pituitary gonadotropin was to reach maximum levels. Resting period (September-February), gonadal steroidogenesis is much reduced, gametogenesis remain absent, pituitary gonadotropin decreases to low value. And prespawning period is characterized by an increase in pituitary gonadotropin content. In such condition, it was clear that African catfish have discontinuous reproduction cycle; meanwhile similar research for Asian catfish has not been conducted.
The aim of this research was to study reproduction physiology status of Asian catfish in captivity with stagnant water pond system.
The experiment was carried out
for twelve months from June 1999 to May 2000. The place of research is faculty
of fisheries and marine science IPB pond. Analysis of blood plasma was
conducted in Physiology Lab., IPB. Measurement of egg diameter was done in Genetics
Lab., Faculty of Fisheries and Marine Science IPB, Bogor. Water quality measurement
was conducted in Environmental Science Lab. IPB.
Twelve immature females Asian catfish (Pangasius hypophthalmus) (All three years old catfish) of 1.5-3 kg in body weight were reared pond with the size of 7 x 10 x 1 m. Each fish were tagged with colored nylon string at the dorsal fin. Broodstock were fed with commercially available pellets SINTA with daily ration of 3% of body weight. Sampling was conducted monthly.
Blood samples 3 ml was taken from the caudal peduncle with a heparinized syringe. Then put in 1.5 ml a polyethylene tube and centrifuged for 5 minutes of 3000 rpm and 50C. Then, plasma blood was put in polyethylene tube and stored in 200C. Steroid hormone content was measured as Testosterone and Estradiol-17b by RIA method.
Sampling of oocytes was conducted using canulation method. Oocytes sample about 200 eggs per female were drawn and fixed in 70% ethanol solution, Oocytes diameter were measured by light microscope completed with ocular micrometer at 40x and 100x magnification.
Water quality measurement consists of DO, ammonia, pH, temperature, alkalinity and total hardness. Rainfall data were obtained from Meteorology Station, Sindang Barang, Bogor, Indonesia.
Oocytes diameter, hormonal profile, were analyzed and presented in figures.
Means Testosterone (T) and
Estradiol-17b (E2) (Figure
1). Means T levels increased from June
(0.4 ± 0.23 ng/ml) and reached high level in September (6.2 ± 0.98 ng/ml) and then decreased in October 3.1 ng/ml,
but in November increased 4.2 ng/ml. The decrease occurred in December to
January. After that T levels increased again but lower than that in June. T
levels increase after January remaining at the value in April (2.2 ± 0.70 ng/ml) and decreased at the end of experiment.
Mean Estradiol-17b (E2) levels were the same with T levels,
increased from June (0.6 ± 0.47 ng/ml) and peaked in September (1.8 ± 0.23 ng/ml). And than, the level gradually decreased
in December (0.3 ± 0.1 ng/ml). After that E2 levels fluctuated to low levels
and increase in April.
Means oocytes diameter (Figure 2) in June were 668.6 ± 6.68
mm
with females weight 2.3 ± 0.19 kg. But in July
oocytes diameter slightly decrease to 602.2 ± 43.03 mm.
and than gradually increased and reached the highest size in December with
means oocytes diameter 1085 ± 26.68 mm, with females weight 3.2 ± 0.27 kg. In this
research, spontaneous spawning did not occur and oocytes started to show
atretic indication in January with the appearance of distinctive white color.
Oocytes atretic became severe in April.
Pond temperature
(Figure 3) was fluctuating with small range, maximum temperature was between 31
320C and minimum temperature 25 280C. Highest
rainfall was in October to February and lowest in March and May.
Discussion
Plasma T is a
biosynthetic precursor for E2. Changes in T levels normally occurred
at the same moment with changes E2 concentration, although monthly
increases of E2 were not as high at vitellogenesis stage. At vitellogenetic
stage, most of T was converted into E2 caused by high activity of
aromatase enzymes. In contrast to vitellogenic stage, postvitellogenic activity
of aromatase enzymes decreased. T levels higher than E2 until
postvitellogenetic stage occurred in ovarian of African catfish.9)
Generally in
teleostei, maturation of oocytes will change hormonal status, environmental
cues caused surge in T levels, for example in rainbouw trout. High surge of T
occurred prior to ovulation and dropped to lowest levels after ovulation.7)
In this research, there were surge of T in mature fish because the desire
environmental cues did not exist in culture condition.
Estradiol-17b (E2)
was mainly ovarian estrogen in most teleostei. E2 were increase
gradually at vitellogenic stage, where in this stage oocytes size increase in
diameter. It has been accepted that E2 stimulated liver to produce
vitellogenin that absorbed by oocytes.6) In this research, means of
E2 increased at the beginning of experiment in June to September,
and then decreased to lowest levels in January. It can be predicted that
vitellogenesis process continues to September and than stopped at
postvitellogenetic stage from September to December.
Mature oocytes can
obtain in October to February. In March to May oocytes quality decreased in all
female that were observed. Oocytes exhibited atretic indication in January with
the appearance of white color. In April, most of oocytes underwent atretic
process in all females. Atretic process occurred when environment cues that
trigger final maturation and spawning do not exist. When mature oocytes do not meet environment cues that triggered
maturation, then oocytes will be degraded and reabsorbed by ovarian follicle.4)
Environmental cues
that perceive in this research are rainfall influence; postvitellogenic stage
was occurred at high rainfall (October-February). T levels that dropped in
October presumably influenced by seasonal changes; where in September (dry
season) were signed with lowest rainfall and than increased in October with the
appearance highest rainfall during reproduction cycle. These changes gave a
direct influence to oxygen content so that oxygen was very low in October (0.96
ppm) causing stress in fish which in turn decreasing of oocytes diameter in October.
Water quality like oxygen, ammonia,
alkalinity and hardness, pH was in normal condition for supporting of Asian
catfish.
Conclusion
T and E2 increase at the same
time with oocytes development to vitelogenetic stage in July to September.
Spawning season goes on September to April with seasonal peak in October to
December.
References
1.
Basuki, F. 1990.
Pengaruh Kombinasi Hormon, PMSG
dan HCG Terhadap Ovulasi Clarias gariepinus (Burchell). Program Pascasarjana IPB. Bogor.
2.
Hardjamulia, A., R. Djajadiredja., S. Atmawinata dan Idris. 1981.
Pembenihan Ikan Jambal Siam (Pangasius sutchi) dengan Suntikan
Ekstrak Kelenjar Hipofisa Ikan Mas (Cyprinus carpio L.). Bull. Pen.
Perikanan I: 183-190.
3. Hardjamulia, A.,
T.H. Prihadi dan Subagya. 1986.
Pengaruh Salinitas Terhadap Pertumbuhan dan Kelangsungan Hidup Benih
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Health Control and Aquaculture Potential of The African Catfish, Clarias gariepinus. Elsevier Science. Publishers B.V., Amsterdam. P: 1 10.
6.
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Hoar, D.J. Randall, and E.M. Donaldson (eds), Fish Physiology, vol. IX,
Academic Press, Inc.
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Matty, A.J., 1985.
Fish Endrocrinology. Timber Press.
Portland. 267p.
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artikel ikan Pangasius. Taman
Akuarium Air Tawar. TMII. Jakarta. Vol I(14): 7-10.
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Richter, C.J.J., E.H. Eding.,
H.J. Th.,R. De Leeuw., A.P. Scott, and P.G.W.J. Van Oordt. 1987. Effec of Pimoside- LHRHa and 17a-hydroxyprogestron on Plasma Steroid Level
and Ovulation in African Catfish Clarias gariepinus. Aquaculture, 63,
157-168.
Figure 1. Changes in Plasma Testosteron and Estradiol 17bLevel in Female during
experiment
Figure 2. Changes in Oocyte Diameter During Experiment
Fig 3. Changes Minimum and
Maksimum Temperature of Pond Water During Experiment.