Interspecific mate recognition among Lake Malawi cichlids of the Pseudotropheus zebra species complex is not mediated by sight alone, but also by sound, according to a study published by scientists from Portugal and the UK in the most recent issue of the Journal of Fish Biology.
Maria Amorim, Jose Simes, Paulo Fonseca and George Turner compared the male courtship acoustic signals of five species of the Pseudotropheus zebra species complex (P. zebra, P. callainos, P. emmiltos, P. fainzilberi and the undescribed species known as P. ~zebra gold from Nkhata Bay).
The authors recorded and analysed the sounds produced by the fishes during courtship in experimental tanks, and found the females to be silent during courtship, while males courting females by repeated sequences of darting and quivering frequently produced low frequency pulsed sounds during quivering.
The sounds of the five species were found to be significantly different from each other in the number and rate of pulse production.
The authors found differences in sound production to be particularly marked among sympatric species that have a very similar colour pattern in males (e.g. P. emmiltos and P. fainzilberi), suggesting that both visual and aural cues are important in allowing the females to distinguish among males of different species.
This observation is supported by the fact that previous studies had shown that P. fainzilberi and P. emmiltos failed to mate assortatively in laboratory mating trials when females had access only to visual signals from males.
The authors conclude that different features of the courtship calls may contain information about species identity and intraspecific differences in traits, such as size, relevant to mate choice.
In particular, the number of pulses and pulse period of courtship sounds are species-specific and these acoustic cues, in conjunction with visual and chemical information, may promote reproductive isolation.
It should be noted that the taxonomy of the studied species quoted in this article follow those as stated by the authors, although other studies currently place all the species studied in the genus Maylandia.
For more information, see the paper: Amorim, MCP, JM Simes, PJ Fonseca and GF Turner (2008) Species differences in courtship acoustic signals among five Lake Malawi cichlid species (Pseudotropheus spp.). Journal of Fish Biology 72, pp. 1355"1368.