Studies On Growth And Feeding Characteristics,Digestive And Endocrine Physiology Of Sebastes Schlegelii In 'Specific Developmental Periods'

Knowing the change law of the growth and feeding characteristics,and the change kinetics of the activity of several major enzymes and the levels of hormone in the early stage of S.schlegelii,it can be effective to guide the management of water environment and feed fry in the‘specific developmental stages' thus to promote the growth,feeding and survival rate of fry in the process of artificial seedling.Under tank-rearing condition,the growth and feeding characteristics of larvae,juvenile and young Sebastes schlegelii in the‘specific developmental periods' were studied.The experiments were carried out in the 8 ‘specific developmental periods',namely primiparous larvae(stage A),4 ‘critical periods'(stage B,E,L,N),2 ‘growth transition periods '(stage G and O)and juvenile stage(stage P)in the early developmental period of Sebastes schlegelii.Morphology,growth and feeding indexes of larvae in the 8 development periods were investigated.And the activity of acid protease,alkaline protease,lipase,amylase,acid phosphatase,alkaline phosphatase and levels of triiodothyronine(T3),thyroxin(T4),somatropin(GH),insulin-like growth factor-I(IGF-?)in larvae were tested.The studies were as follows:1 Growth Characteristics of Sebastes schlegelii in‘Specific Developmental Periods'The variation of the growth indexes could be fitted in 2-3 straight lines.The total length,body weight,body length,and preanal length increased following a three-step linear growth curve with 2 inflection points(stage G and O)as the boundary;body height increased following a three-step linear growth curve with 2 inflection points(stage E and O)as the boundary;eye diameter increased following a two-step linear growth curve with one inflection point(stage G)as the boundary;and snout length increased following a two-step linear growth curve with one inflection point(stage E)as the boundary.All the growth rates of the 8 indexes followed a rising trend.2 Feeding Characteristics of Sebastes schlegelii in ‘ Specific Developmental Periods'The feeding incidence and satiation rate were at a low level in stage A,began to rise rapidly from stage B,and maximized in stage N.The degree of digestive tract fullness was all of level 3-4 after stage N,satiation in stages A though P was of rising trend and increased greatly after stage G.The daily ration in stages B through P showed an upward trend as a whole,increased faster from stage G,and reached significant value(P<0.05)at stage G,L,N and O.Feeding rhythm of fry was daytime feeding type with two peaks of twilight,feeding was active in the daytime than at night,and the two feeding peaks appeared at 6:00 and between 15:00 and 21:00.Digestion time had the overall trend of rising to falling and to rising again along with the growth and development of the fry,while satiation feeding time kept declining as a whole.3 Digestion physiology of Sebastes schlegelii in ‘Specific Developmental Periods'Acid protease,alkaline protease,lipase,amylase,acid phosphatase,alkaline phosphatase could be all detected in stage A.The acid phosphatase,alkaline phosphatase,lipase and amylase exhibited a high activity in the stage A,however,a downward trend was detected during the stage A-P and a peak appeared in stage L.The activity of lipase decreased slowly,while a rapid decline(P < 0.05)during the stage A-G was detected for acid phosphatase,alkaline phosphatase and amylase.The activity of acid protease and alkaline protease exhibited a low level in the stage A since which the activity of acid protease was stable until the stage N and increased signifcantly during the stage N-P.While,the activity of alkaline protease increased signifcantly until the stage G and remained almost the same during the stage G-P.4 Endocrine physiology of Sebastes schlegelii in ‘Specific Developmental Periods'The levels of GH and IGF-?showed the same trend of first increase followed with a decline and another increase.The content of IGF-?was higher than that for GH.A peak in the stage G(P < 0.05)and a trough in the stage L(P < 0.05)were detected for both GH and IGF-?.The content change of T3 and T4 showed an upward trend similarly.Nevertheless,T4 exhibited constantly a higher level than T3 whose content changed following T4.T4 showed a content peak in the stage G(P <0.05),while the content peak of T3 appeared in the stage L(P < 0.05).