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

      Correlations of oocyte diameter with some morphometric characters in the nile tilapia, Oreochromis niloticus L. 

      MAR Garcia-Abiado, HJS Paras & GC Mair - 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
      A study was conducted to determine the correlation of oocyte diameter with some morphometric characters in a Philippine strain of Oreochromis niloticus L. One hundred and thirty-five 7- to 9-month old sexually mature female broodstock (body weight: 71±35 g; standard length: 13.1±2.1 cm) were randomly sampled from a pool of broodstock maintained in 4 m2 net enclosures suspended in an earthen pond. The following morphometric characters were determined for each fish: body weight, standard length, genital pore dimension, and genital papilla dimension. Intra-ovarian oocyte samples were obtained by inserting a soft silicon rubber tubing into the ovipore of the fish and aspirating the oocytes by mouth. There were no significant correlations between the average oocyte diameter and any of the morphological characters studied. Results justify the adoption of an ovarian biopsy technique for assessing the stage of gonadal maturity in sexually mature tilapia.
    • Conference paper

      Impact of nickel poisoning on the histology of the ovaries of Oreochromis mossambicus 

      C Sioson & A Herrera - 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
      Ovaries of Oreochromis mossambicus exposed to sublethal concentrations of nickel sulphate (0.5 mg/1 and 1.0 mg/1) were histologically analyzed. Changes following exposure to 0.5 mg/1 nickel sulphate include irregularities in the shape of egg follicles, subcellular oocyte damage, lifting off of the theca layer and proliferation of connective tissues. In the ovaries exposed to 1.0 mg/1 nickel sulphate, degenerative changes are worse. Invasion by connective tissues is extensive, oocytes have bizarre shapes, yolk granules are scattered in the interfollicular spaces, abnormal growths are evident and previttelogenic oocytes abound.

      Nickel is a toxicant in Oreochromis mossambicus ovaries.
    • Conference paper

      Nickel-induced pathohistologic alterations in Oreochromis mossambicus 

      G Gicaro & A Herrera - 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
      A pathohistologic study was conducted to determine the effects of nickel on the testes of maturing Mozambique tilapia, Oreochromis mossambicus. The fish were treated with 0.5 mg/L and 1.0 mg/L sublethal dose of nickel sulphate for four weeks. A week reduction in spermatogenic activity together with the disintegration of seminiferous tubules and spermatocytes are commonly observed in the 0.5 mg/L-treated fish. This results in the scattering of germ cells and the occurrence of spaces within the spermatocysts. Pyknotic nuclei are also seen in some specimens. Connective tissues and blood cells invade the damaged regions of the organ. Enlargement of Sertoli cells and interstitial cells are also observed. These effects are more pronounced in the 1.0 mg/L-treated testes.

      Relatively low levels of nickel in aquatic ecosystems impose a great danger to the reproduction and survival of Mozambique tilapia.