PLASMA-LEVELS OF SEX STEROIDS IN 3 SPECIES OF PIPEFISH (SYNGNATHIDAE)

The pipefishes (Syngnathidae) are marine teleosts in which the males b rood the young. In some species sex-role reversal occurs when, contrar y to the usual pattern, females compete more intensely than males for access to mates. This paper reports an investigation of the sex hormon es of males and females to see whether they deviate from the ''normal' ' teleost pattern. To that end, plasma levels of the androgens testost erone (T), 11-ketotestosterone (OT), 11beta-hydroxytestosterone, 11-ke toandrostenedione, and 11beta-hydroxyandrostenedione (OHA), together w ith 17alpha-hydroxy-20beta-dihydroprogesterone (17,20-P) and 17beta-es tradiol (E2), were measured by means of radioimmunoassay in three spec ies of pipefish: Nerophis ophidion, Syngnathus typhle, and Syngnathus acus. Plasma levels of OT, the dominant circulating androgen in breedi ng males of most teleost species, was found to be highest in breeding males and low or non-detectable later in the brooding males. This obse rved decline in male OT levels from the prespawning to the postspawnin g (=brooding) period is in general agreement with what has been found in other teleosts. In both breeding and brooding S. acus males, T was quantitatively the dominant androgen, whereas OHA was the major androg en in S. acus females, as well as in the females and breeding or brood ing males of both S. typhle and N. ophidion. In breeding S. acus and S . typhle males the levels of T, OHT, and OT were higher than in corres ponding brooding males and females. The 17,20-P level was below detect ion limit. E2 was also usually non-detectable, but was most consistent ly found in breeding Syngnathus males.