Genetics. Published Articles Ahead of Print: November 10, 2008, Copyright © 2008
doi:10.1534/genetics.108.094623


A more recent version of this article appeared on December 1, 2008.
Originally published as Genetics Published Articles Ahead of Print on October 14, 2008.

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Genetics of Mating and Sex Determination in the Parasitic Nematode Haemonchus contortus

Elizabeth Redman 1, Victoria Grillo 2, Erica Packard 1, Gary Saunders 1, Frank Jackson 3, Matt Berriman 4 and John Gilleard 5*

1 University of Glasgow
2 Charles Sturt University
3 Moredun Research Institute
4 Sanger Genome Institute
5 University of Calgary

* To whom correspondence should be addressed. E-mail: jsgillea{at}ucalgary.ca.

Submitted on July 31, 2008
Revised on September 9, 2008
Accepted on 10 October 2008


Abstract

Genetic analysis of parasitic nematodes has been a neglected area of research and the basic genetics of this important group of pathogens is poorly understood. Haemonchus contortus is one of the most economically significant livestock parasites worldwide and is a key experimental model for the strongylid nematode group which includes many important human and animal pathogens. We have undertaken a study of the genetics and the mode of mating of this parasite using microsatellite markers. Inheritance studies with autosomal markers demonstrated obligate dioecious sexual reproduction and polyandrous mating which is reported here for the first time in a parasitic helminth and provides the parasite with a mechanism of increasing genetic diversity. The karyotype of the H. contortus, MHco3(ISE) isolate was determined as 2n = 11 or 12. We have developed a panel of microsatellite markers that are tightly linked on the X-chromosome and have used them to determine the sex chromosomal karyotype as XO male and XX female. Haplotype analysis using the X-chromosomal markers also demonstrated polyandry, independent of the autosomal marker analysis, and enabled a more direct estimate of the number of male parental genotypes contributing to each brood. This work provides a basis for future forward genetic analysis on H. contortus and related parasitic nematodes.

Key Words: microsatellites, null alleles, parasitic nematodes, polyandry, strongylid