ASCORBATE CONCENTRATION IN FISH ONTOGENY

The ontogenetic trend of ascorbate has been quantified in three freshwater fishes: roach (Rutilus rutilus), whitefish (Coregonus lavaretus) and Arctic charr (Salvelinus alpinus). Total ascorbate (reduced and oxidized) declined from 150 to μg g−1 as newly hatched larvae grew to become several‐months‐old juveniles. Declining total ascorbate with increasing size of metamorphosing fish could not be reversed by feeding on brine shrimp, Artemia salina nauplii, zooplanktonic food containing > 74μg g−1 total ascorbate. The proportion of reduced ascorbate in total ascorbate increases with fish size/age. The physiological mechanism of the changes in transferable ascorbate forms remains unknown, but high dehydroascorbate concentrations suggest high vulnerability of larval fish to oxidation stress. This is the first report on quantity of vitamin C retained in actively‐feeding larval and juvenile fish. The efficiency of ascorbate transfer from zooplankters to larval fish amounted to 5–20%. The ecological significance of larval fish feeding on various zooplankters and/or phytoplankton may reflect a trend toward maximum transfer of this vitamin in freshwater food webs. Copyright © 1992, Wiley Blackwell. All rights reserved