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.

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.

Wings have damage control for insect-sized smash-ups

Flying insects have their fender-benders, too, and so have evolved at least two alternatives to bumpers.

Yellow jacket wings have a dot of rubbery material called resilin toward the wing tip along the leading edge. The wing doesn’t flex in flight but bends there during collisions, Andrew Mountcastle of Harvard University reported January 5.

In a lab test, wings with a natural resilin patch lost only 18 percent of the tip area when a yellow jacket was spun in a rotating cradle that bumped the wing tip area against a fixed surface for an hour. When researchers immobilized the rubbery spot (by gluing on a dot of polyester glitter), spinning yellow jackets lost about 80 percent of their wing tip area.

A common bumblebee’s wings don’t have rubbery spots, but spinning them in the collider didn’t cause damage as severe as in yellow jacket wings with a glitter-stiffened joint. Resilin might not help much in bumblebees because it would have to be six times stiffer to prevent flexing during their deep, fast wingbeats, Mountcastle calculated. Instead, he hypothesizes that bumblebees get crash flexibility from reduced wing veins toward the tip.