CHANGES IN OTOLITH STRONTIUM - CALCIUM RATIOS IN METAMORPHOSING CONGER MYRIASTER LEPTOCEPHALI

Content ratios of strontium (Sr) to calcium (Ca) in the otolith of Con ger myriaster metamorphosing leptocephali and elvers increased with in creasing increment number from the core to the 110th increment and sub sequently decreased. The otolith region from the 110th increment to th e edge corresponded to the metamorphic stage. The Sr:Ca ratios in otol ith edges of metamorphosing leptocephali were inversely related to met amorphic stage, suggesting that the changes in otolith Sr:Ca ratios we re influenced by some physiological factor(s) rather than by environme ntal factors. Sr concentration in leptocephalus somatic tissues was hi gh and decreased as metamorphosis progressed until the late metamorphi c stage when the preanal myomere to total myomere ratio was 0.4. Ca co ncentration was constant throughout ontogenesis. Body Sr:Ca ratios mar kedly decreased as metamorphosis progressed. Decrease in somatic Sr co ncentration and the consequent decrease in body Sr:Ca ratios seemed to be associated with the breakdown of glycosaminoglycan (GAG) in gelati nous matrix, which is the major constituent of soft tissue in leptocep hali. Catabolism of GAG may also cause a decrease in otolith Sr:Ca rat ios during metamorphosis. In leptocephalus otoliths, Sr:Ca ratios may change in association with the synthesis and breakdown of GAGs during ontogeny.