Female Croaking gouramis emit a purring sound during mating which differs from the sounds emitted during courtship, says a new study.
Croaking gouramis, Trichopsis vittata, have special pectoral fin muscles and tendons which allow them to generate sounds when they beat their fins.
Acoustic studies of the species have just shown that the sounds produced by females during sex are different to those of pre-courtship, suggesting that they might convey different information to males.
"The Croaking gourami is the only fish species in which females are known to initiate spawning acoustically," said Friedrich Ladich of the University of Vienna, who has just published his findings in the journal Animal Behaviour.
"During mating, a female approaches a male's nest at the water surface and emits purring sounds in a vertical head-up position. This behaviour is followed by spawning bouts.
"Agonistic sounds of both sexes lasted longer than the females' prespawning sounds, consisting of four or five bursts compared to 2.4 bursts in purring sounds, and included a smaller percentage of short bursts."
Purring females a turn-onLadich says that both sexes produced long, high-intensity croaking sounds during disputes, which he believes probably help the fish to assess the fighting ability of their partner.
Only the females were found to emit a low, purring noise, and he thinks it's this noise that initiates and coordinates spawning behaviour in Croaking gouramis.
Ladich says that the low sound and short duration of prespawning sound indicates that they function as short distance mating displays directed specifically at their partner, which reduces the likelihood of attracting competiting males or predators.
For more information see the paper: Ladich F (2007) - Females whisper briefly during sex: context- and sex-specific differences in sounds made by croaking gouramis. Animal Behaviour, 2007, 73, 379-387.