Morphological development of the swimming and feeding apparatus in larval rabbitfish, Siganus guttatus.
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The development of body parts for swimming and feeding in Siganus guttatus larvae was studied in samples reared in the laboratory at temperatures of 27.3-30 degree C. From the observations, the larval stage of S. guttatus may be divided into three phases: (1) inactive swimming and feeding by swallowing (to about 4-5 mm TL); (2) the transitional phase (to about 7-8 mm TL); and active swimming and feeding (8 mm TL and beyond). A change in feeding habits may be expected in S. guttatus larvae at sizes 7-8 mm TL as shown by this study.
ALSO IN: Compilation of JICA Expert Activities at SEAFDEC, Aquaculture Department (1986-1990) and additional (since 1974) by S. Fukumoto, vol.2, Japan International Cooperation Agency (JICA) 1990, pp44-50.
In: Maclean, J.L., Dizon, L.B., Hosillos, L.V. (eds.). The First Asian Fisheries Forum. Proceedings of the First Asian Fisheries Forum, 26-31 May 1986, Manila, Philippines. Manila, Philippines: Asian Fisheries Society. pp. 173-178
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Differential expression of insulin-like growth factor I and II mRNAs during embryogenesis and early larval development in rabbitfish, Siganus guttatus FG Ayson, EGT de Jesus, S Moriyama, S Hyodo, B Funkenstein, A Gertler & H Kawauchi -
General and Comparative Endocrinology, 2002 - Academic PressIn rodents, the expression of insulin-like growth factor II (IGF-II) is higher than that of insulin-like growth factor I (IGF-I) during fetal life while the reverse is true after birth. We wanted to examine whether this is also true in fish and whether IGF-I and IGF-II are differentially regulated during different stages of embryogenesis and early larval development in rabbitfish. We first cloned the cDNAs of rabbitfish IGF-I and IGF-II from the liver. Rabbitfish IGF-I has an open reading frame of 558 bp that codes for a signal peptide of 44 amino acids (aa), a mature protein of 68 aa, and a single form of E domain of 74 aa. Rabbitfish IGF-II, on the other hand, has an open reading frame of 645 bp that codes for a signal peptide of 47 aa, a mature protein of 70 aa, and an E domain of 98 aa. On the amino acid level, rabbitfish IGF-I shares 68% similarity with IGF-II. We then examined the relative expression of the two IGFs in unfertilized eggs, during different stages of embryogenesis, and in early larval stages of rabbitfish by a semiquantitative reverse transcription-polymerase chain reaction. Primers that amplify the mature peptide region of both IGFs were used and PCR for both peptides was done simultaneously, with identical PCR conditions for both. The identity of the PCR products was confirmed by direct sequencing. Contrary to published reports for seabream and rainbow trout, IGF-I mRNA was not detected in rabbitfish unfertilized eggs; it was first expressed in larvae soon after hatching. IGF-II mRNA, however, was expressed in unfertilized eggs, albeit weakly, and was already strongly expressed during the cleavage stage. mRNAs for both peptides were strongly expressed in the larvae, although IGF-II mRNA expression was higher than IGF-I expression.
ArticleH Kohno, S Hara, M Duray & A Gallego -
Nippon Suisan Gakkaishi, 1988 - Japanese Society of Fisheries ScienceThe early larval development of Siganus guttatus was studied with emphasis on the transition from endogenous to exogenous feeding. Three rearing trials were conducted as follows: 1) rearing in a 5 ton concrete tank at 27.9-29.3oC (T-85 trial); 2) rearing in a 0.5 ton fiberglass tank at 22.2-26.5oC (T-86A trial); 3) rearing in the same manner as in T-86A but without food (T-86B trial). On the basis of the developmental events and energy flow in T-86A trial, the early life history of the species could be divided into the following seven phases: 1) rapid larval growth due to rapid yolk resorption (from hatching to about 15 h after hatching (time after hatching: TAH)); 2) slow growth and organogenesis based mainly on yolk energy (to about 50 h TAH); 3) slow growth based on energy of yolk, oil globule and exogenous food (to about 50 h TAH); 4) slow growth based on two sources of energy, oil globule and exogenous food (to about 90 h TAH); 5) the same mode of development and energy flow as in the preceding phase, but with a certain level of feeding amount (to about 120 h TAH); 6) accelerated larval growth and effective feeding and swimming based only on exogenous food (to about 150 h TAH); and 7) the same mode as in the preceding phase with accelerated increase of feeding amount (beyond 150 h TAH). Differences in developmental mode were observed in T-85 and T-86A trials, but it could not be ascertained in this particular study which of the environment factors played the greatest influence. The results of T-86A and B showed that the larvae, in order to survive, have to get over two obstacles on feeding, that is, to start feeding and to change from endogenous to exogenous feeding suitably.
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 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.