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Sex chromosome evolution in the clam shrimp,Eulimnadia texana

Weeks, SC, Benvenuto, C, Sanderson, TF and Duff, RJ 2010, 'Sex chromosome evolution in the clam shrimp,Eulimnadia texana' , Journal Of Evolutionary Biology, 23 (5) , pp. 1100-1106.

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Chromosomes that determine sex are predicted to evolve differently than autosomes: a lack of recombination on one of the two sex chromosomes is predicted to allow an accumulation of deleterious alleles that eventually leads to reduced functionality and potential physical degradation of the nonrecombining chromosome. Because these changes should occur at an elevated evolutionary rate, it is difficult to find appropriate species in which to test these evolutionary predictions. The unique genetic sex-determining mechanism of the crustacean Eulimnadia texana prevents major chromosome degeneration because of expression of both ‘proto-sex’ (i.e. early stage of development) chromosomes in homozygous form (ZZ and WW). Herein, we exploit this unique genetic system to examine the predicted accumulation of deleterious alleles by comparing both homogametic sexual types to their heterogametic counterpart. We report differences in crossing over in a sexlinked region in the ZW hermaphrodites (3%) relative to the ZZ males (21%), indicative of cross-over suppression in the ZW hermaphrodites. Additionally, we report that both ZZ and WW genotypes have reduced fitness relative to ZW hermaphrodites, which is consistent with the prediction of harboured recessive mutations embedded on both the Z and the W chromosomes. These results suggest that the proto-sex chromosomes in E. texana accumulate recessive deleterious alleles. We hypothesize that recessive deleterious alleles of large effect cannot accumulate because of expression in both ZZ and WW individuals, keeping both chromosomes from losing significant function.

Item Type: Article
Schools: Schools > School of Environment and Life Sciences
Journal or Publication Title: Journal Of Evolutionary Biology
Publisher: Blackwell Publishing
Refereed: Yes
ISSN: 1010-061X
Funders: Funder not known
Depositing User: H Kenna
Date Deposited: 29 Sep 2014 11:09
Last Modified: 05 Apr 2016 18:16

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