Protandry is much less common than protogyny, and has been most often studied in the Anemonefish (genus Amphiprion). Consequently, the Amphiprion spp. serve as the model for studies in protandry.
The anemonefish are symbiotic with sea anemones, and consequently aneomone-limited due to high predation pressure and lack of anemones (Fricke and Fricke, 1977). As a monogamous single male Amphiprion with a single female with low density, protandry increases the males genetic fitness if the female ides (Ochi, 1989).
Fricke and Fricke (1977) found that Amphiprion akallaopisos and A. bicinctus will forcefully maintain a monogamous relationship (isntead of polgynous or polyandrous) simply due to the lack of available space. Upon forcing two males to inhabit an empty sea anemone, it was the dominant male which changed to female.
Ochi (1989) observed that males would sometimes repair with females instead of changing sex. As the sex-change process can take up to two months, a male that changes sex to female will miss the rest of the spawning season, thus lowering genetic fitness. However, should the male become separated from a female outside of the breeding season, it would be advantageous for the male to change sex.
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