Hormonal changes accompanying sexual maturation in milkfish Chanos chanos Forsskal
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In spite of the economic importance of milkfish to the Southeast Asia, relatively little information is available on its reproductive biology and physiology. Milkfish has a prolonged juvenile phase undergoes first sexual maturation at five years. Steroid hormone profiles during this juvenile phase and the change accompanying sexual maturation is described. There were no significant differences in levels of serum estradiol 17-B (E2), testoterone (T) and progestrone (P) of male and female immature fish. In immature fish, E2 ranfed from 0.145 to 0.600 ng/ml, T varied from 2.04 to 3.75 ng/ml, and P ranged from 0.472 to 1.16 ng/ml. Serum T, however, was significantly high in 4 years old immature fish fish while E2 was significantly high in 2 years old fish. Mean E2 level rose from 0.54 ± 0.11 ng/ml (E2) in immature female (Stage 1) to 4.53 ± 1.16 ng/ml in vitellogenic females (Stage 5) while T increased from 2.06± 0.28 ng/ml to 38.4± 9.26 ng/ml. E2 and T levels were positively correlated to egg diameter. Progesterone level, however, remained low through vitellogenesis. 17-a-OH-progesterone and 17-a, 20-B-progesterone were not detectable even in fully vitellogenic females. Gonade development in males was sccompanied by increase serum T levels only. T levels increase from 2.5± 0.40 ng/ml in immature males to 27.73± 5.02 ng/ml in spermeating males. Significantly higher T level was found in males with thick but abundant milt (spermiation index, SPI, 2+ ) compared to males with scanty milt (SPI, 1+) or mals with copious, fluid milt (SPI, 3+). Ther was no significant seasonal variation in levels of E2 and T of immuture 3-5 years old female sampled from july 1981 through February 19083. Serum E2 varied from 0.125 ng/ml to 1.45 ng/ml while T was uniformly low and ranged from 1.16 ng/ml tp 2.07 ng/ml. The levels of E2 and T significantly rose during the breeding season (April-June, 1983)and accompanied the increase in gonadosomatic index (GSI) aat this time (E2, 3.43± 0.49 ng/ml; T, 40.04± 16.20 ng/ml ). The levels of both steroids dropped to below 1 ng/ml in spent females sampled in the succeeding months. In immature males, mean serum E2 was beolw 1 ng/ml through except for a significan high level (2.36 ng/ml ) found in 3 years old male sampled in October to December, 1981 while T levels ranged from 1.11 ng/ml to 2.78 ng/ml. As in females, T levels significantly rose to 21.52± 8.38 ng/ml during the breding season when GSI peaked (April-June ,1983). E2 remained low throughout. T level dropped to arround 10 ng/ml in the succeeding months when spent or regressed fish were samlped
In: Ohnishi, E., Nagahama, Y., Ishizaki, H., (eds.). Proceedings of the First Congress of the Asia and Oceania Society for Comparative Endocrinology (AOSCE), 4-7 November 1987, Nagoya, Japan. Nagoya, Japan: Nagoya University Corporation. pp. 183-184
PublisherNagoya University Corporation
- Conference Proceedings 
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Conference paperLV Benitez - In RD Fortes, LC Darvin & DL de Guzman (Eds.), Fish and crustacean feeds and nutrition : Proceedings of the seminar-workshop on fish and crustacean feeds and nutrition held on 25-26 February 1985 at UPV, Iloilo City, 1989 - Philippine Council for Aquatic and Marine Research and DevelopmentThis paper reviews recent work on milkfish nutrition. Substantial progress had been made towards understanding the digestive physiology of milkfish. Major enzaymes envolved in the digestions of carbohydrates, protein and lipids had been detected in the pyloric caece, intestines and pancreas of milkfish. The most active carbohydrates were involved in the hydrolysis of α - glocosidic bonds. Intestinal amylase activity consistently reached the peak at about noon when milkfish gut was full. This confirms that milkfish is s daytime feeder. No cellulase activity was detected in any region orf the digertive treat although the fish relies heavily algae and other plant source for food. Trypsin, chymotrypsin and general proteases were also detected in milkfish digestive tract. A powerful milkfish trypsin inhabitor was detected in the filementous algae, Chaetomorpha brachygona which is predominant species in lumot. Lipass in the pancreas and intestines had two pH optima, suggesting a physiologic versatility for lipid digestion in milkfish. There is a limit information on the nutrient requirement of milkfish. Most studies showed that milkfish fry has a dietary requirement of 40% protein, and 7-10 lipid. Studies on the protein-energy requirement of fingerlings suggested that 30-40% protein, 10% fat and 25% carbohydrates are required. Subsequent studies showed an optimum protein energy to total metabolizable energy ratio of 44.4%. Amino acid test diets for milkfish had been formulated to contain white fish meal, gelatin and approprate amino acid mix.
Lactate dehydrogenase isozyme patterns during the development of milkfish, (Chanos chanos (Forskal)) PD Requintina, LM Engle & LV Benitez -
Kalikasan, The Philippine Journal of Biology, 1981 - University of the Philippines at Los BañosPolyacrylamide disc gel electrophoresis was done to determine the lactate dehydrogenase (LDH) isozyme patterns for fry (5-3 mg), fingerling (6-12 g), pond-size (150-250 g) and adult (6-9 kg) milkfish. The patterns were tissue specific; the different tissues examined, viz., eye, liver, heart, and skeletal muscle had different expressions of LDH isozymes. The resolved patterns appeared to be products of LDH gene loci A, B, and C. Subunits A and B were present in all tissues. A4 and B4 were predominant in skeletal and heart muscle, respectively; the two associated non-randomly in vivo and formed only the heteropolymers A3B and AB3. A liver band, L4, was most conspicuous in the fingerling, pond-size, and adult; it was assumed to be coded by locus C. A negatively charged band, X4, was detected in fully developed ovary and in fry homogenized as whole individuals, but it could not be resolved in tissues of fingerling. Six-mo old stunts and 3-mo old fingerlings had similar LDH patterns for all tissues examined. The patterns for 11-mo old stunts and fingerlings also were similar but the one for the eye of the former was the same pattern resolved for the eye of adults. There was no change in the LDH isozyme patterns of milk fish stunted for 6 mo under different salinity levels (0-5, 15-20, 32-35 ppt).
BookWorldFish Center - 2007 - WorldFish CenterMilkfish Bibliography covers 700 references on milkfish biology; broodstock management and fry, fingerling and egg collection and production; milkfish culture systems; health and nutrition; post harvest technology; socioeconomic and related studies; and environment and ecology. Included references range from published/unpublished documents, theses, journal articles, to project reports and conference papers.