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Genetics

Title:		Why are there males in the hermaphroditic species Caenorhabditis elegans?
Author(s):		Chasnov JR; Chow KL;
Address:		"Department of Mathematics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong"
Journal Title:		Genetics
Year:		2002
Volume:		160
Issue:		3
Page Number:		983 - 994
DOI:		10.1093/genetics/160.3.983
ISSN/ISBN:		0016-6731 (Print) 0016-6731 (Linking)
Abstract:		"The free-living nematode worm Caenorhabditis elegans reproduces primarily as a self-fertilizing hermaphrodite, yet males are maintained in wild-type populations at low frequency. To determine the role of males in C. elegans, we develop a mathematical model for the genetic system of hermaphrodites that can either self-fertilize or be fertilized by males and we perform laboratory observations and experiments on both C. elegans and a related dioecious species C. remanei. We show that the mating efficiency of C. elegans is poor compared to a dioecious species and that C. elegans males are more attracted to C. remanei females than they are to their conspecific hermaphrodites. We postulate that a genetic mutation occurred during the evolution of C. elegans hermaphrodites, resulting in the loss of an attracting sex pheromone present in the ancestor of both C. elegans and C. remanei. Our findings suggest that males are maintained in C. elegans because of the particular genetic system inherited from its dioecious ancestor and because of nonadaptive spontaneous nondisjunction of sex chromosomes, which occurs during meiosis in the hermaphrodite. A theoretical argument shows that the low frequency of male mating observed in C. elegans can support male-specific genes against mutational degeneration. This results in the continuing presence of functional males in a 99.9% hermaphroditic species in which outcrossing is disadvantageous to hermaphrodites"
Keywords:		"Animals Caenorhabditis elegans/*genetics Disorders of Sex Development/*genetics Female Male Models, Genetic Mutation *Sex Determination Processes Sexual Behavior, Animal;"
Notes:		"MedlineChasnov, J R Chow, King L eng Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, P.H.S. 2002/03/20 Genetics. 2002 Mar; 160(3):983-94. doi: 10.1093/genetics/160.3.983"