Seminal plasma composition, sperm motility, and milt dilution in the Asian catfish Clarias macrocephalus (Gunther)
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Ionic composition of the seminal plasma and factors that initiate sperm motility in the freshwater Asian catfish Clarias macrocephalus, were examined to develop an artificial seminal plasma (ASP) that can be used to dilute milt. The optimum ratio of milt:ASP that can reversibly activate the sperm and milt–ASP:ovulated eggs that will result in high fertilization rates were further determined to minimize the number of males to be sacrificed during artificial insemination. Seminal plasma of C. macrocephalus contained 17.8±0.1 mM/l potassium, 164.4±0.6 mM/l sodium, 8.4±0.0 mM/l calcium and 1.6±0.0 mM/l magnesium, and had an osmolality of 269.0±6.4 mOsm/kg, and pH of 7.8±0.2. Sperm motility was highest and longest in all electrolyte (NaCl, CaCl2, KCl) and non-electrolyte (mannitol) solutions of 200 mOsm/kg. Catfish sperm were motile in all isotonic NaCl–KCl solutions, and were reversibly activated in the ASP (143 mM NaCl, 30 mM KCl, 8 mM CaCl2, 2 mM MgCl2, 10 mM HEPES) solutions of pH 6.4–9.4. Altogether, these results suggest that sperm motility in C. macrocephalus was mainly initiated by a decrease in osmotic pressure, rather than ions and pH. High fertilization rates (89–94%) were observed when 10 μl milt, diluted with 1000 μl ASP, was activated with 5 ml of 0.6% NaCl (198.24 mOsm/kg) to fertilize 5 or 10 g of ovulated eggs. Results obtained from the present study provide information on sperm physiology that will lead to more efficient gamete management, and hopefully, an increase in the yield of catfish fry in the hatchery.
CitationTan-Fermin, J. D., Miura, T., Adachi, S., & Yamauchi, K. (1999). Seminal plasma composition, sperm motility, and milt dilution in the Asian catfish Clarias macrocephalus (Gunther).
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Conference paperMN Duray - In F Lacanilao, RM Coloso & GF Quinitio (Eds.), Seminar-Workshop on Aquaculture Development in Southeast Asia and Prospects for Seafarming and Searanching; 19-23 August 1991; Iloilo City, Philippines., 1994 - Aquaculture Department, Southeast Asian Fisheries Development CenterStudies on sea bass (Lates calcarifer) broodstock were directed at techniques to maximize egg production. Now known are the: optimum luteinizing hormone releasing hormone analogue (LHRHa) dose range to induce spawning, optimum egg size responsive to LHRHa induction, appropriate time for induction, proper storage conditions for LHRHa, and induction of spermiation in males. Gonadal maturation and spawning are successfully induced by LHRHa and/or 17 alphamethyltestosterone. An experiment on photoperiodic induction of sexual maturation is being conducted to produce seed year round. Increased information on larval morphology and physiology of sea bass led to improvements in feeding strategies and transport techniques. Studies on nutrient requirements and practical diets are currently being undertaken for different stages/sizes of sea bass. An economic assessment found an integrated sea bass production system viable. Studies on groupers (Epinephelus spp.) have been geared towards broodstock development including induction of sex inversion by hormonal control, intraspecific interaction, and sex control using synthetic anabolic steroids. Spontaneous maturation and successive spawnings of captive Epinephelus suillus were achieved in 1990. Larval rearing techniques used for other marine fish species were tried but with limited success. Culture techniques in ponds and floating cages using SEAFDEC-formulated diets or commercial pellets are being developed. Studies on snappers (Lutjanus spp.) have been started with the identification of species common in Panay Island.
Conference paperIC Liao & YS Chang - In Proceedings of the International Milkfish Workshop Conference, May 19-22, 1976, Tigbauan, Iloilo, Philippines, 1976 - Aquaculture Department, Southeast Asian Fisheries Development CenterMilkfish is one of the most important food fishes in Taiwan. There are more than 16,000 ha of culture area and over 160 millions of fry are needed for milkfish farming industry every year. The fry are collected from the sea and also imported from other countries. However, due to several environmental factors, there is unpredictable fluctuations in the occurrence of these wild fry. In recent years, the demand for milkfish fry has gone up considerably owing mainly to the fast-growing populations, the natural resources being so limited that there is insufficient supply of stocking materials of this important foodfish. To solve the problem of shortage of milkfish fry, Tungkang Marine Laboratory started the preliminary work on artificial propagation of milkfish in 1970. In addition to capturing wild spawners, the Laboratory has also been raising the adult milkfish in tanks for this objective. After being reared for six years, one male and one female were dissected on 11 April 1976. The male had ripe sperms; the testes weighing 4.63 g with the GSI of 0.12. The gonad of the female weighed 21.20 g with the GSI of 0.66 and part of the ovarian oocytes was found to be at the oil droplet (yolk vesicle) stage. Judging from the condition of maturity of the above female, the feasibility of raising tank-reared spawners was ensured. It is believed that this is the first attempt on the world and is the prelude to successful artificial propagation by using tank-reared milkfish as spawner.
Conference paperGV Hilomen-Garcia, RB Baldevarona & FJ Lacanilao - In CL Marte, GF Quinitio & AC Emata (Eds.), Proceedings of the Seminar-Workshop on Breeding and Seed Production of Cultured Finfishes in the Philippines, Tigbauan, Iloilo, Philippines, 4-5 May 1993, 1996 - Aquaculture Department, Southeast Asian Fisheries Development CenterMilt volume, sperm density, and number of spermatozoa were determined to quantify milt production of mature sea bass after a single injection of LHRHa [(D-Ala6,Pro9-N-ethylamiide)LHRH] in saline solution and 17α-methyltestosterone in corn oil (MT). Two measures of sperm density, sperm count and spermatocrit, were highly correlated (r=0.85). Compared with control, milt volume and the number of spermatozoa collected increased but sperm count decreased (24% at 24 h) after a LHRHa (20 µg/kg body weight treatment, suggesting a stimulation of spermatozoa production and not merely milt dilution. Further milt dilution (44%) was induced by 80 µg/kg LHRHa (LHRHa80) at 12 h post-treatment but not by 200 µg/kg MT (MT200) alone. A milt dilution of only 27% at 12 h after simultaneous injections of LHRHa80 and MT200 may indicate some inhibitory effect of MT on the efficiency of LHRHa. These results demonstrate that the stimulation of milt production by LHRHa involves testicular hydration resulting in milt dilution.