Sex chromosome evolution in the clam shrimp, Eulimnadia texana

Weeks, SC; Benvenuto, C; Sanderson, TF; Duff, RJ

Abstract

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.

Citation

Weeks, S., Benvenuto, C., Sanderson, T., & Duff, R. (2010). Sex chromosome evolution in the clam shrimp, Eulimnadia texana. Journal of Evolutionary Biology, 23(5), 1100-1106. https://doi.org/10.1111/j.1420-9101.2010.01963.x

• Journal Article Type: Article
• Publication Date: Jan 1, 2010
• Deposit Date: Sep 29, 2014
• Journal: Journal Of Evolutionary Biology
• Print ISSN: 1010-061X
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• Volume: 23
• Issue: 5
• Pages: 1100-1106
• DOI: https://doi.org/10.1111/j.1420-9101.2010.01963.x
• Publisher URL: http://dx.doi.org/10.1111/j.1420-9101.2010.01963.x
• Additional Information: Funders : Funder not known