, Volume 5, Issue 1, pp 79-91

Larval Development of Silver Sea Bream (Sparus sarba): Ontogeny of RNA-DNA Ratio, GH, IGF-I, and Na+-K+-ATPase

Rent the article at a discount

Rent now

* Final gross prices may vary according to local VAT.

Get Access


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 α1 and β1 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 α1 and β1 subunit mRNAs increased up to 35 dph, however, at 46 dph the α1 subunit remained high whereas the β1 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.