Induced Maturation of Prawn Penaeus indicus

Abstract

Viable spawns have been obtained in the laboratory from untreated prawn Penaeus indicus and from others which had one eyestalk ablated. Fecundity was shown to be dependent on spawning technique, female size and whether the spawner was wild or domestic. Using low aeration during spawning, domestic unablated female fecundity was significantly lower than it was for wild females, due to a concomitantly smaller ovary volume. During late premoult, mature ovaries are resorbed to ovarian Stage 1-2 and after ecdysis they redevelop. 52.1 O/O of spawnings occurred during early premoult, 44.4 O/o during intermoult, 3.5 O/O at premoult, while no spawns occurred during late premoult or early postmoult. Average egg numbers and hatch successes were higher for unablated females when compared with ablated females. Average spawns per moult cycle were 1.98 and 2.24, respectively. It was conservatively estimated that wild females spawn at least 7-9 times in a lifetime. There were twice the number of spawns with a black tank background as there were with a white one and the former yielded higher average egg numbers and hatch successes. General pigmentation, ovary, egg and nauplius colour was dependent on background colour. Moult-cycle duration was temperature dependent but generally shorter for ablated females. As female condition decreased, moult-cycle duration decreased accordingly for any given temperature. Spawning activity declined when the condition factor was less than 0.8. Both ablated and unablated spawning females > 39 g tended to decrease in mass and condition while females < 39 g continued to grow. Nutrition is probably the main contributory factor to this anomalous growth. Large females possibly have nutritional requirements different from females of less than 39 g. A viable F, generation of P. indicus has been reared.

Avaliação do efeito da serotonina (5-HT) e da monoablação do pedúnculo ocular na indução da maturação ovariana de Penaeus penicillatus (Alcock, 1905)

“…Estudos posteriores têm evidenciado o papel indutor da monoablação do pedún-culo ocular para acelerar a maturação, a produção de ovos e a freqüência de desovas entre as mudas, além de induzir o encurtamento do ciclo de muda (Emmerson, 1980;Browdy & Samocha, 1985;Browdy et al, 1986).…”

“…Emmerson (1980), estudando a maturação induzida em P. indicus, aborda a reabsorção de ovócitos em decorrência do ciclo de muda. É possível que essas variações sejam decorrentes de características fisiológicas intrín-secas de cada animal, principalmente por tratar de uma população alóctone (criada exclusivamente em cativeiro).…”

“…Embora a literatura indique alguns estudos alternativos na indução da maturação ovariana em cativeiro, a técnica ainda utilizada é a monoablação do pedúnculo ocular que, apesar do registro de dados conflitantes, como aqueles registrados por Chamberlain & Lawrence (1981apud Browdy, 1992; Emmerson (1980); Browdy & Samocha (1985), foi amplamente assimilada pelas fazendas de camarão. Por outro lado, os estudos alternativos utilizando a manipulação hormonal, bem como o uso de neurotransmissores, necessitam de maior aprofundamento.…”

An hypothesis on the light requirements for spawning penaeid shrimp, with emphasis on Penaeus setiferus

“…Emmerson (1983) noted that unablated P. monodon would not spawn in tanks 2 m X 1.5 m X 0.5 m deep, even under reduced light intensity. In an earlier study, the same author (Emmerson, 1980) found that P. indicus held in tanks with black interiors spawned twice as frequently as those maintained in tanks with white interiors. The difference would appear to relate to the absorbance of light in black tanks as compared with reflectance in white tanks.…”

“…Spectral influences on spawning were also examined by Caillouet (1972) and Primavera (1980). Emmerson (1980Emmerson ( , 1983 P. monodon 39-68 Beard and Wickins (1980) P. indicus 45-50 Emmerson et al (1983) P. plebejus 3-17 Kelemec and Smith (1980) Another apparently light-related phenomenon involves the lack of spawning in small tanks. Many researchers feel that only relatively large tanks can be used to spawn shrimp.…”