Simultaneous hermaphroditism; cost and benefit

• Published in: Journal of theoretical biology Vol. 64; no. 2; pp. 363 - 373
• Main Author: Heath, D.J.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 21.01.1977
• Subjects: Animals; Disorders of Sex Development; Energy Metabolism; Female; Fertilization; Male; Oogenesis; Population Density; Reproduction; Spermatogenesis
• ISSN: 0022-5193; 1095-8541
• DOI: 10.1016/0022-5193(77)90363-0

Current theories explain simultaneous hermaphroditism by the advantage it gives to organisms which are widely dispersed or sluggish, resulting in a low frequency of reproductive contacts. It is difficult to see why hermaphroditism is not more widespread unless there is some counterbalancing disadvantage. It is suggested that hermaphrodites suffer an energetic cost because they maintain two reproductive systems and a cost due to the reduced number or viability of offspring which may result from accidental self-fertilization. These costs will result in a disadvantage to hermaphroditism (compared to gonochorism) when reproductive contacts are frequent. However, even in widely dispersed or sluggish organisms behavioural mechanisms may exist which increase the frequency of reproductive contacts, favouring gonochorism instead of hermaphroditism. It is argued that externally fertilizing species should as a rule be gonochoric and that species which brood their young may often be hermaphroditic. Hermaphroditism in species which form permanent male/female pairs in the breeding season could result in more zygotes being produced. However, where parental care of the young is important, it is suggested that gonochorism and sexual dimorphism may result in more progeny being reared.