The reproductive cycle of the endangered cyprinid Alburnus albidus: Morphological changes of the gonads and plasma sex steroid fluctuations

Abstract

Alburnus albidus is an endangered and little known cyprinid fish species endemic in southern Italy. Histological characteristics of testes of A. albidus from River Alento, Campania Region, were analysed every month between January‐July 1996. Depending on the relative abundance of spermatogonia, spermatocytes, sper‐matides and spermatozoa in the testes, we devided the gonadal cycle into four stages: 1. quiescence, when mainly spermatogonia were present (January‐February); 2. recrudescence, when spermatocytes were abundant, although spermatids were also detectable (March‐April); 3. spawning, when cysts contained all stages of germ cells (May‐June); 4. Postspawning, when testes contained spermatogonia only (July). The concentration of sex steroids (an‐drogens, 17 α‐hydroxyprogesterone and 17 β‐estradiol) fluctuated throughout the year. Androgen levels were high during the quiescence and the spawning periods. 17 α‐hydroxyprogesterone concentration showed a sharp increase just before the spawning period. 17 β‐estradiol levels were quite low, with the exception of a slight increase during the recrudescence and the spawning periods.

Key words:

• Cypirinidae
• Italy
• Alburnus albidus
• Gonads
• Sex steroids
• Reproductive cycle