Larval development of silver sea bream (Sparus sarba): ontogeny of RNA-DNA ratio, GH, IGF-I, and Na(+)-K(+)-ATPase.
To ascertain some of the important biochemical and molecular events that take place during early larval development of silver sea bream (Sparus sarba), we undertook a study of changes in the morphology as well as the ontogeny of the RNA-DNA ratio, growth hormone (GH), insulin-like growth factor I (IGF-I) messenger RNA abundance, Na(+)-K(+)-ATPase subunit mRNA abundance, and Na(+)-K(+)-ATPase enzyme activity. Larvae samples were collected at 1 to 46 days posthatch (dph). At 7 dph the yolk sac was fully absorbed, and from 28 dph onward larvae underwent rapid developmental changes to the juvenile stage. The RNA-DNA ratio was highest at 1 dph, decreased to low levels between 7 and 21 dph, then increased by 28 dph, and then again by 46 dph. The ontogenetic profiles of GH, IGF-I, and Na(+)-K(+)-ATPase alpha1 and beta1 subunits were studied using reverse transcriptase polymerase chain reaction, coupled with radioisotope hybridization of immobilized DNA. Growth hormone abundance reached a constant and high level from 35 dph onward, whereas the IGF-I level reached a peak at 35 dph and then significantly decreased. Both Na(+)-K(+)-ATPase alpha1 and beta1 subunit mRNAs increased up to 35 dph, however, at 46 dph the alpha1 subunit remained high whereas the beta1 subunit decreased. Na(+)-K(+)-ATPase activity was low in 1-dph larvae but increased rapidly as development progressed. The importance of these findings is discussed within the context of larval development.
Deane
E E
EE
Department of Biology, Chinese University of Hong Kong, Shatin, NT Hong Kong SAR, China.
Kelly
S P
SP
Collins
P M
PM
Woo
N Y S
NY
D000375:Aging / Q000502:physiology; D000818:Animals; D004247:DNA / Q000032:analysis; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D013006:Growth Hormone / Q000502:physiology*; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000502:physiology*; D007814:Larva / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D008297:Male; D009024:Morphogenesis / Q000235:genetics / Q000502:physiology; D012333:RNA, Messenger / Q000032:analysis; D021541:Sea Bream / Q000235:genetics / Q000254:growth & development*; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics / Q000502:physiology*
D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D004247:DNA; D000254:Sodium-Potassium-Exchanging ATPase