Browsing by Author "Caballero, Rose Marie"
Light color and ovarian maturation in unablated and ablated giant tiger prawn Penaeus monodon (Fabricius) The effect of light color (green, blue and white fluorescent lights, with natural light as a control) on maturation in intact and eyestalk-ablated Penaeus monodon was tested in 12-m3 broodstock tanks. Size and quality of sequential spawns from ablated females were also compared. In Experiment 1, unablated females under green light produced the highest number of spawns (5), total number of eggs (4.26 × 106), total number of nauplii (2.69 × 106) and mean egg counts (6537 eggs g−1 female), the latter significantly higher than in the other treatments. Mean nauplii counts were higher under green (3979 g−1 female) and natural (3303 g−1 female) light compared to the other treatments. Mean hatch rate was highest in control (87.3%) but this was not significantly different from green light (61.8%). In Experiment 3, ablated females under natural light gave the highest total number of eggs (13.04 × 106) and nauplii (9.74 × 106). Mean egg and nauplii counts were significantly higher in the natural (4436 eggs and 3308 nauplii g−1 female) and green (4016 eggs and 2906 nauplii g−1 female) light treatments compared to white. Hatchability was similar for all treatments. In Experiment 2 (using green light), ablation increased the total number of spawns, eggs and nauplii 14 to 17 times. Rematuration data showed no significant differences in spawn size (egg counts); hatchability and nauplii counts of sequential spawns were similar in Experiment 2 but tended to decrease in Experiment 3.
ArticleHatchery-reared Penaeus monodon postlarvae were cultured in ponds until they attained adult size. Thereafter, the shrimps were transferred to concrete broodstock tanks for maturation. During the culture period, the morphological changes of the ovary in relation to the development of the external genitalia and other quantitative parameters were examined. Based on histology, primordial germ cell and chromatin nucleolus in the early stages of ovarian development were reported in addition to the stages that have been described earlier on adult specimens, thus completing the description of ovarian development on P. monodon. Females with ovaries at the perinucleolus stage can be impregnated as long as the thelycum is structurally developed to receive the spermatophores. Females with cortical rod stage ovaries either spawned or resorbed their eggs before molting, indicating that the molting cycle overrides reproductive activity in first-maturing females.