Ascorbic acid in the gonads of North Sea dab (Limanda limanda) during the reproductive cycle

Abstract

Total ascorbic acid was measured in the gonads of North Sea dab (Limanda limanda) throughout one reproductive cycle. In the ovaries, the concentration of ascorbate began to increase during the resting period in summer and reached maximum values of 400 µg⋅g fresh weight (fw) -1 at the onset of ovary maturation in fall. Concentrations declined rapidly towards the spawning period in spring and reached the lowest values of 80-100 µg⋅g fw -1 . The maximum deposition of ascorbate in the ovaries amounted to 2.5 mg⋅organ -1 and occurred in late winter, corresponding to the beginning of the spawning period. In the testes, ascorbate concentrations were lower than in the ovaries, reaching a maximum of 170 µg⋅g fw -1 in early fall. The lowest values of 20-60 µg⋅g fw -1 appeared in winter and spring. In the testes the highest deposition of ascorbate amounted to 110 µg⋅organ -1 and appeared at the beginning of maturation. The sexual differences and seasonal variations are discussed in relation to the reproductive biology of dab.Résumé : L'acide ascorbique total a été mesuré dans les gonades des poissons Limande (Limanda limanda) de la mer du nord durant un cycle reproductif complet. Dans les ovaires les concentrations de l'acide ascorbique total commencent à augmenter durant la période de repos (été), et atteignent des valeurs maximales de 400 µg⋅g poids frais (pf) -1 durant l'automne; c'est à dire au début de la croissance des ovaires. Au printemps, les concentrations ont chuté rapidement avant la période de fraye, et ont atteint des concentrations minimales de 80 à 100 µg⋅g pf -1 . Vers la fin de l'hiver, la déposition maximale de l′acide ascorbique était de 2.5 mg⋅organe -1, correspondant au début de la période de fraye. Au début de l′automne, dans les testicules, les concentrations de l'acide ascorbique total étaient moins que dans les ovaires atteignant une valeur maximale de 170 µg⋅g pf -1 . En hiver et au printemps, des concentrations minimales de 20 à 60 µg⋅g pf -1 ont été atteintes. Au début de la maturation, la déposition d′acide ascorbique dans les testicules était de 110 µg⋅organe -1 . La différence sexuelle et les cycles saisonièrs sont mis en relation avec la biologie de reproduction du limande.

Ascorbic acid and reproduction in fish: endocrine regulation and gamete quality

“…an increase in cyprinid fish (Seymour 1981) and a decrease in many other species including yellow perch ( Perca flavescens ) (Dabrowski & Ciereszko 1996a), cod ( Gadus morhua ) (Sandnes & Braekkan 1981) or North Sea dab ( Limanda limanda ) (Saborowski, Koprivnjak, Sisak, Sahling, Buchholz, Lum & Schneider 1997). Dietary level affects ascorbate concentration in the gonads of cod (Mangor‐Jensen & Holm 1994), rainbow trout ( Oncorhynchus mykiss ) (Blom & Dabrowski 1995) and other species. There are differences between male and female gonad concentrations (Saborowski et al . 1997) and in the annual (reproductive cycle) dynamics of ascorbate deposition. Active transfer of ascorbate occurs from yolk reserves into larval fish body (Fig.…”

“…Variation in ascorbic acid concentration is related to gametogenesis, although trends towards maturation are not consistent, i.e. an increase in cyprinid fish (Seymour 1981) and a decrease in many other species including yellow perch ( Perca flavescens ) (Dabrowski & Ciereszko 1996a), cod ( Gadus morhua ) (Sandnes & Braekkan 1981) or North Sea dab ( Limanda limanda ) (Saborowski, Koprivnjak, Sisak, Sahling, Buchholz, Lum & Schneider 1997).…”

“…There are differences between male and female gonad concentrations (Saborowski et al . 1997) and in the annual (reproductive cycle) dynamics of ascorbate deposition.…”