Now showing items 1-6 of 6

    • 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).
    • Article

      Effect of thyroxine on growth and development in post-yolk-sac larvae of milkfish, Chanos chanos 

      TJ Lam, JV Juario & JE Banno - Aquaculture, 1985 - Elsevier
      Post-yolk-sac larvae of milkfish, Chanos chanos (commonly referred to as “fry”) were collected along the shore in the Philippines. Treatment of these long, slender and transparent larvae with L-thyroxine-sodium (Eltroxin, Glaxo) by immersion in 0.5 ppm solution (changed daily) markedly accelerated their growth and development. By day 15 of the treatment, the treated larvae had become silvery, opaque and adult-like in form, whereas the control larvae were still slender and transparent (or at best translucent) with incomplete silvering of the body. 0.1 ppm thyroxine was less effective. Discontinuation of the treatment after 8 days was also less effective as judged by the appearance and weight of the larvae on day 15.
    • Conference paper

      Endocrine changes associated with overripening of ovulated eggs in goldfish, Carassius auratus L. 

      MJ Formacion & 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
      Changes in steroid hormone levels in the serum and ovarian fluid were studied during overripening in goldfish. Ovulated eggs retained in the ovarian cavity become overripe at around 12 h after ovulation and completely overripe 24 h after. Blood and ovarian fluid were taken at 0, 3, 6, 12, 18, and 24 h after ovulation. Estradiol-17ß (E 2) , testosterone (T), progesterone (P) and 17α,20ß-dihydroxy-4-pregnen-3-one (17α,20ß-P) in the serum were extracted directly with a solvent while those in the ovarian fluid were separated by HPLC before radioimmunoassay. Both serum and ovarian fluid P showed a highly significant decline at 18 h with a further decline at 24 h; P levels were higher in the ovarian fluid. Serum 17α,20ß-P showed a progressive and more rapid decline, decreasing significantly at 12 h with further decreases at 18 h and 24 h; the level was five-fold lower at 24 h compared to the 0 h level. Serum T increased significantly at 3 h which was maintained until 18 h, when it declined to 0 h level. No significant changes in E2 were observed in the serum, except for a significant difference between 6 and 24 h. There were no significant changes in E2, T and 17α,20ß-P in the ovarian fluid. Of the four steroids measured, only 17α,20ß-P and P showed changes which bear some correlation with the time course of overripening. The declines in the mean ratios of 17α,20ß-P/E2 in the serum and P/E2 in the ovarian fluid also appeared to have a good correlation with the time course of overripening. The postovulatory follicles (POFs) showed degenerative features which likewise correspond to the decline in P and 17α,20ß-P.
    • Conference paper

      Problems associated with hormonal induction of gonad development in milkfish (Chanos chanos) 

      F Lacanilao, CL Marte & TJ Lam - In Lofts B. & WN Holmes (Eds.), Current Trends in Comparative Endocrinology. Proceedings of the 9th International Symposium in Comparative Endocrinology, 7-11 December 1981, Hongkong, 1985 - Hong Kong University Press
      Recent developments in milkfish breeeding include succesful induced spawning of wild1,2 and captive3-5 fish and spontaneous spawning of broodstock.6 Gravid spawners, however, are available only during the wild or are reared in captivity. The seasonal and uncertain supply of wild fry is a major constraint in efforts to increase production of this important food fish in the Philippines, Indonesia, and Taiwan. Gonad devepolment can be induced in some fish by hormone administration. This has been recently reviewed by Lamp7 and other workers.8,9 Induced gonad development using purified salmon gonadotropin have been reported in Salmo gairdneri,10 Oncorhynchus gorbuscha,11,12 and Mugil cephalus.13,14 Hormones are usually administered by injection at frequent intervals in these studies. To reduce stress from frequent handling, a slowrelease hormone cholesterol pellet was with success in Salmo auratus and Ophicephalus striatus.16

      Recent literature suggests that vitellogenesis in fish (at least yolk granule or gobule formation) is under control of estrogen and a pituitary factors. Estrogen stimulates the liver to produce vitellogenin, while the incoporation of vitellogenin into oocytes requires a pituitary factor which may not be the glycoprotein (Con A II) gonadotropin.7 In the light of this information and in anticipation of a synergistic role of thyroid hormone ,17 a combination of fish pituitary extract, estrogen and thyroxin was used in some of our experiments.

      Our attempts to induce gonad development in sexually immature milkfish and rematuration of regressed fish have not been sucessful to date.

      This paper presents the experiments done and discusses factors possibly contributing to the negative resp[onse in this fish.
    • Conference paper

      The role of cyclic amp in oocyte maturation of goldfish, Carassius auratus 

      EB Seraspe, CH Tan & 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
      The role of cyclic AMP in oocyte maturation was investigated using denuded goldfish oocytes cultured in vitro. The oocytes were stimulated with a maturation-inducing steroid (MIS), 17α, 20ß dihydroxy-4-pregnen-3-one (17, 20 P) with or without forskolin or forskolin only. Changes in cAMP concentrations and percent maturation of the oocytes were determined. Results showed that elevated levels of cAMP maintain the oocytes in meiotic arrest while a decrease would trigger the resumption of meiotic maturation.
    • Article

      Thyroxine injection of female rabbitfish (Siganus guttatus) broodstock: changes in thyroid hormone levels in plasma, eggs, and yolk-sac larvae, and its effect on larval growth and survival 

      FG Ayson & TJ Lam - Aquaculture, 1993 - Elsevier
      The thyroid hormone levels in female rabbitfish, Siganus guttatus, plasma, eggs, and yolk-sac larvae were measured before and after thyroxine (T4) injection in female spawners at doses of 1, 10, and 100 μg T4/g body weight (BW) fish. T4 and triiodothyronine (T3) levels in maternal plasma, eggs, and yolk-sac larvae were elevated following T4 administration. Apparently, there is conversion of T4 into T3 in the broodfish which suggests the presence of the enzyme, 5′-monodeiodinase, in rabbitfish. T4 and T3 in maternal circulation were easily transferred into the oocytes and subsequently into the larvae. Larvae from spawners treated with 10 and 100 μg T4/g BW tended to be longer and showed sornewhat better survival compared to the control and those injected with 1 μg T4/g BW 7 days after hatching. These findings suggest that thyroid hormones may play an important role during early larval development of rabbitfish.