Integrative and Comparative Biology

Pregnant male pipefish have hormone swings

The first study to track a form of testosterone through male pregnancy in fish has found an unusual roller coaster of swoops and spikes.

Among pipefishes, seahorses and sea dragons, females produce eggs but males get pregnant, carrying the embryos. Even though pregnant male Gulf pipefish (Syngnathus scovelli) reverse common sex roles, tests show males still have more of the main fish form of testosterone (called ketotestosterone) than females do, Sunny K. Scobell of Texas A&M University in College Station reported on January 6. What’s different in role-reversed pipefish is that male ketotestosterone levels vary, much as hormones do in females of other species.