Birds do it, bees do it, but this Amazon basin fish do it with ‘lectricity! The nocturnal (and toothless) gymnotiform fish attract the opposite sex and intimidate rivals by amping up their electric field:
One weakly electric fish is the nocturnal gymnotiform fish (Brachyhypopomus pinnicaudatus), a toothless fish native to the Amazon basin. At night, males of the species give off big, long electric hums, almost like serenades. […]
Salazar discovered the male fish invested as much as 11 percent to 22 percent of their body’s energy in their nocturnal electric displays. Females hardly exerted themselves electrically, just expending 3 percent of their energy.
“If these displays are expensive to generate, one can presume that individuals paying attention to these signals can infer a better quality male is generating them,” Salazar told LiveScience.
When Salazar looked at how fit the males were, she found the fattest and healthiest males often broadcast the biggest electric signals. As such, they were essentially advertising their bodies.