Now showing items 1-4 of 4

    • Conference paper

      Control of gonad growth, maturation and spawning in teleost fish: A review 

      AD Munro & TJ Lam - 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 Center
      Despite their great variety of reproductive strategies, a general characteristic of most teleosts is that (where known) natural reproduction shows a long-term periodicity, even in tropical habitats (e.g. see contributions in Munro et al. 1990a). Typically, gonad development from puberty leads to fully-grown gonads by the advent of the spawning season; if conditions are appropriate, then final gonad maturation leads to the production of viable gametes during one or more breeding bouts. Subsequently, in those larger species which spawn over more than one season, the gonads regress and the individual returns to a phase where any growth is somatic. However, there is wide interspecific variability in the pattern of gonad development (Wallace and Selman 1981, de Vlaming 1983, Billard 1986, Selman and Wallace 1989).
    • Conference paper

      Influence of LHRHa and methyltestosterone on milt production of sea bass Lates calcarifer (Bloch) 

      GV 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 Center
      Milt 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.
    • Conference paper

      Maturation of Oreochromis niloticus gonads 

      AA Casauay & VS Carino - 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 Center
      At hatching when fry were 5 to 6 mm, primordial germ cells (PGCs) were found to concentrate along the dorsomedian region of the peritoneal wall at the root of the developing mesentery and in places far from the appearance of testocoel and ovocoel. At 56 days posthatching, oogenic cells in the ovary had enlarged approximately 2 to 3 times their former size. The testis remained quiescent although the stromal tissues with developing efferent ducts increased distinctly in amount. Spermatogenesis occurred at three months posthatching.
    • Conference paper

      A review of SEAFDEC/AQD finfish breeding research 

      LMB Garcia - 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 Center
      Recent progress undertaken by SEAFDEC/AQD in the development of broodstock of a variety of cultured fish in the Philippines is reviewed. Spontaneous maturation and spawning has been achieved among captive breeders of grouper, milkfish, sea bass, rabbitfish, and tilapia. Hormonal intervention methods have been developed mainly to accelerated final gonadal maturation to synchronize release of mature gametes, and to control sex inversion among hermaphroditic fish such as grouper. These methods entailed the development of gonadal biopsy procedures and hormone administration protocols such as mode on introducing a variety of exogenous hormones to fish, administration intervals, and lately response times.Enhancement of reproduction by improving the diet fed to Nile tilapia, rabbitfish, and milkfish breeders has also been achieved in recent years. Protein or lipid enrichment of the diet may enhance growth of broodstock to subsequently increase reproductive performance and fry survival.Limited success has been achieved with photoperiod manipulation to effect year-round sexual maturation and spawning of milkfish and sea bass broodstock.