Now showing items 1-8 of 8

    • Article

      Effect of growth hormone and γ-aminobutyric acid on Brachionus plicatilis (Rotifera) reproduction at low food or high ammonia levels 

      WG Gallardo, A Hagiwara, Y Tomita & TW Snell - Journal of Experimental Marine Biology and Ecology, 1999 - Elsevier
      Growth hormone (GH, 0.0025 and 0.025 I.U. ml−1) and γ-aminobutyric acid (GABA, 50 μg ml−1) enhance rotifer population growth in batch cultures. In order to further understand the mechanism of their actions, we conducted experiments culturing isolated females at low food and high free ammonia levels. At an optimum food level of 7×106Nannochloropsis oculata cells ml−1 or at low free ammonia level of 2.4 μg ml−1, the F1 offspring of rotifers treated with GH at 0.0025 I.U. ml−1 had significantly higher population growth rate (r) and net reproduction rate (Ro), and shorter generation time than untreated rotifers. At a lower food level of 7×105 cells ml−1 or at high free ammonia level of 3.1 μg ml−1, rotifers treated with GABA at 50 μg ml−1 had significantly higher r and Ro, and shorter generation time. These results indicate that GABA is effective in enhancing rotifer reproduction when rotifers are cultured under stress whereas GH enhances rotifer reproduction when culture conditions are optimal. Significant effects were also observed in F1 and F2 generations which were not treated with hormones. These data may be useful for treating rotifer mass cultures to mitigate the effects of stress caused by high population densities.
    • Article

      Effect of juvenile hormone and serotonin (5-HT) on mixis induction of the rotifer Brachionus plicatilis Muller 

      WG Gallardo, A Hagiwara & TW Snell - Journal of Experimental Marine Biology and Ecology, 2000 - Elsevier
      Juvenile hormone (JH) and serotonin (5-HT) were previously shown to enhance mictic (sexual) female production of the rotifer Brachionus plicatilis in batch cultures. To explore the basis of these effects, experiments were conducted on isolated individuals. JH treatment of maternal rotifers with 5 and 50 µg ml-1 (18.8 and 187.7 µM) resulted in significantly higher (P < 0.05) mictic female production in the second (F2) and third (F3) generations. JH treatment was effective even at a lower food concentration of 7 × 105 cells ml, but it was not effective when free ammonia was added at 2.4 and 3.1 µg ml-1. Mictic female production was not increased with exposure to 5-HT up to 50 µg ml-1 (129.1 µM) concentrations. When food level was reduced to 7 × 105 cells ml-1, however, 5-HT-treated rotifers produced significantly (P < 0.05) more mictic females than the control, particularly in F3 generation. Mictic female production of 5-HT-treated rotifers did not differ from that of the control with or without free ammonia, but the intrinsic rate of natural increase (r) of 5-HT-treated rotifers at 3.1 µg ml-1 free ammonia was significantly higher than the control. These results show that juvenile hormone increases mictic female production under optimum and sub-optimum food levels, whereas 5-HT increases both mictic female production at low food level and population growth rate at high free ammonia concentrations. These compounds could be used to manage rotifer cultures and probe the mechanisms controlling the rotifer life cycle as it switches to mictic reproduction.
    • Article

      Effect of some vertebrate and invertebrate hormones on the population growth, mictic female production, and body size of the marine rotifer Brachionus plicatilis Müller 

      WG Gallardo, A Hagiwara, Y Tomita, K Soyano & TW Snell - Hydrobiologia, 1997 - Springer Verlag
      Eight vertebrate and invertebrate hormones were screened for their effect on population growth, mictic female production, and body size of the marine rotifer Brachionus plicatilis. Growth hormone (GH) or human chorionic gonadotropin (HCG) at 0.0025-25 I.U. ml-1 and estradio1-17β (E2), triiodothyronine (T3), 20-hydroxyecdysone (20-HE), 5-hydroxytryptamine(5-HT), gamma-aminobutyric acid (GABA) or juvenile hormone (JH) at 0.05-50 mg l-1 were added to 5-ml of Nannochloropsis oculata suspension (7 x 106 cells ml-1). From an initial density of 1 individual ml-1, rotifers were cultured with hormones for 48 hours in 22 ppt seawater at 25 °C, in darkness. Rotifers were counted and classified into female types and transferred to a new algal food suspension without hormone every other day until day 8 when body size was measured. Population growth was significantly higher in treatments exposed to GABA (50 mg l-1), GH (0.0025 and 0.025 I.U. ml-1), HCG (0.25 and 2.5 I.U. ml-1), and 5-HT (5 mg l-1). E2 caused a decrease in population growth, whereas JH, 20HE, and T3 had no effect. Mictic female production was significantly higher at 0.05 and 0.5 mg l-1 JH and 0.05 and 5 mg l- 5HT. GH (0.0025 and 0.025 I.U. ml-1), E2 (50 mg l-1 ), GABA (0.5, 5 and 50 mg l-1), and 20-HE (0.05 mg l-1) treatments had significantly higher mictic female production only on day 8, 6, 4, and 6, respectively. T3 and hCG had no effect on mictic female production. Lorica length increased by 9.6% and 4.4% in rotifers treated with JH (0.05 mg l-1) and GABA (5 mg l-1), respectively. Correspondingly, lorica width increased by 8.9% and 2.6% in these treatments. In comparison, 20-HE-, T3-, and HCG-treated rotifers were smaller (3.9-8.2%) and GH, 5-HT and E2 had no effect on rotifer body size.
    • Article

      Evaluation of mucus, Navicula, and mixed diatoms as larval settlement inducers for the tropical abalone Haliotis asinina 

      WG Gallardo & SMA Buen - Aquaculture, 2003 - Elsevier
      Different biological films reportedly effective in larval settlement of other abalone species were tested on the tropical abalone Haliotis asinina to determine the most effective settlement inducers for the species. Larval attachment was significantly higher on mucus, Navicula, Navicula+mucus, and mixed diatoms+mucus than on mixed diatoms and the blank control. Metamorphosis was significantly higher on Navicula, Navicula+mucus. These results indicate the important contribution of mucus in larval settlement and the effectiveness of Navicula as a single species over mixed diatoms in larval settlement of the tropical abalone H. asinina.
    • Article

      GABA, 5-HT and amino acids in the rotifers Brachionus plicatilis and Brachionus rotundiformis 

      WG Gallardo, A Hagiwara, K Hara, K Soyano & TW Snell - Comparative Biochemistry and Physiology - Part A: Molecular and Integrative Physiology, 2000 - Elsevier
      γ-Aminobutyric acid (GABA) and 5-hydroxytryptamine (5-HT) have been shown to increase the reproduction of the Brachionus plicatilis (NH3L strain). In the present study, the endogenous presence of GABA and 5-HT in the rotifers B. plicatilis (NH3L and Kamiura strains) and Brachionus rotundiformis (Langkawi strain) were confirmed by dot blot immunoassay and high-performance liquid chromatography (HPLC). HPLC showed that GABA and 5-HT concentrations in the three rotifer strains range from 71 to 188 pmol/mg and from 12 to 64 pmol/mg, respectively. A total of 33 amino acids were also detected in B. plicatilis and B. rotundiformis, with glutamic acid, serine, glycine, taurine, threonine, alanine, arginine, proline, valine and isoleucine in high concentrations relative to other amino acids.
    • Article

      Gonad development of Placuna placenta Linnaeus fed Isochrysis galbana Parke, Tetraselmis tetrahele (G.S. West) Butch, or their combination 

      WG Gallardo, MTR de Castro, RT Buensuceso, CC Espegadera & CC Baylon - Aquaculture, 1992 - Elsevier
      A study was conducted to determine a suitable algal diet for the window-pane oyster, Placuna placenta Linnaeus, during gonad development. Sexually immature P. placenta (70 mm shell height) were fed Isochrysis galbana Parke, Tetraselmis tetrahele (G.S. West) Butch, or their 1:1 combination, at 100 000 cells per ml divided into two rations per day. Temperature and salinity ranged from 27 to 29 °C and 28 to 32 ppt, respectively. Monthly gonad histological examination showed a rapid gonad development in P. placenta fed the combination of I. galbana and T. tetrahele, attaining sexual maturity in the third month of rearing, a month ahead of those fed single algal species.
    • Article

      Market survey of snappers (Genus Lutjanus) from Panay and Palawan waters 

      RMT Cheong, WG Gallardo & JD Toledo - Philippine Journal of Science, 1992 - Science and Technology Information Institute
      Thirteen species of snappers (genus Lutjanus) were identified and sourced for location of capture from surveys conducted at the Iloilo Fishing Port and Central Market. They were Lutjanus argentimaculatus,Lutjanus boutton, Lutjanus carponotatus, Lutjanus decussatus, Lutjanus fulviflamma, Lutjanus malabaricus, Lutjanus monostigma, Lutjanus quinquelineatus, Lutjanus rivulatus and Lutjanus vitta. Incidence of lutjanids was year round with a peak in May. Most abundant and commonly observed were Lutjanus vitta, Lutjanus gibbue and Lutjanus argentimaculatus.
    • Article

      Shell marking by artificial feeding of the tropical abalone Haliotis asinina Linne juveniles for sea ranching and stock enhancement 

      WG Gallardo, MN Bautista-Teruel, AC Fermin & CL Marte - Aquaculture Research, 2003 - Blackwell Publishing
      A method of marking abalone (Haliotis asinina Linne) for sea ranching and stock enhancement purposes was developed. Three-month-old abalone juveniles (11.8-mm shell length, 0.28 g) were fed artificial diets for 1, 2, or 3 weeks. The width of the bluish-green shell band produced by abalone juveniles was 1.7, 2.6, and 4.2 mm after 1, 2, or 3 weeks of feeding respectively. The growth and survival of juveniles fed artificial diets did not differ from that of juveniles fed the seaweed Gracilariopsis bailinae (control). Feeding the diet-fed juveniles with the seaweed thereafter produced the natural brownish shell, thus forming a sandwiched bluish-green band. An experimental release in outdoor tanks with natural growth of seaweeds and diatoms, and in a marine reserve showed that the shell band remained clear and distinct, indicating the usefulness of this shell marking method in sea ranching and stock enhancement of abalone.