Integrative and Comparative Biology
Notes from the Society for Integrative and Comparative Biology annual meeting, San Francisco, January 3-7
By Susan Milius
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.
For most of a male pipefish’s 14-day pregnancy, ketotestosterone concentrations stay low, closer to female ketotestosterone levels. This dip allows for normal embryo development. About day 10 or 11, male ketotestosterone concentrations shoot up tenfold, presumably letting males ready sperm for the next mating, within a day or so of giving birth, Scobell said.