Evidence that male sea lamprey increase pheromone release after perceiving a competitor: raw data, R-code, R analyses

Sexual signals evolve via selective pressures arising from male-male
competition and female choice, including those originating from unintended
receivers that detect the signal. For example, males can acquire
information from other males signaling to females and alter their own
signal. Relative to visual and acoustic signals, less is known about how
such communication networks influence chemical signaling among animals. In
sea lamprey (Petromyzon marinus), chemical communication system is
essential for reproduction, offering a useful system to study a pheromone
communication network that includes signalers and both intended and
unintended receivers. Male sea lamprey aggregate on spawning grounds where
individuals build nests and signal to females using sex pheromones. We
examined how exposure to a major component of the male pheromone,
3keto-petromyzonol sulfate (3kPZS), influenced male pheromone signaling,
and whether females had a preference for males that altered their signal.
Exposure to 3kPZS, at a concentration of 5x10-10 M, simulated the presence
of other male(s) and led to increased 3kPZS release rates within 10 min,
followed by a return to baseline levels within 30 min. Exposure also led
to increases in hepatic synthesis and circulatory transport of pheromone
components. In behavioral assays, females preferred the odor of males that
had been exposed to 3kPZS; therefore, males likely benefit from
upregulating 3kPZS release after detecting competition for mates. Here, we
define how a specific pheromone component influences chemical signaling
during intrasexual competition, and show a rare example of how changes in
chemical signaling strategies resulting from male competition may
influence mate choice.