Comparative Reproductive Biology in Nematodes

Moreira-Pinto, Beatriz; Pires-daSilva, André

doi:10.1016/b978-0-12-809633-8.20599-2

Cited by 1 publication

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“…Hermaphroditism and parthenogenesis have evolved many times independently in Nematoda, in most cases most probably from ancestral gonochoristic ancestors [5,6]. Mixed breeding strategies, including trioecy and heterogony (alternating generations of distinct mating strategies) are also present [7,8]The best-known nematodes with mixed breeding strategies are parasites. For example, Strongyloides species (Tylenchina, Clade IV [9]) have a facultative freeliving generation with gonochoristic females and males, and a parthenogenetic female generation that lives inside the mammalian host [10,11].…”

Section: Introductionmentioning

confidence: 99%

Chromosome-wide evolution and sex determination in a nematode with three sexes

Tandonnet

Koutsovoulos

Adams

et al. 2018

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The free-living nematode Auanema rhodensis is a rare example of a species with three sexes, in which males, females and hermaphrodites coexist. A. rhodensis males have only one X chromosome (XO), whereas females and hermaphrodites have two (XX). The A. rhodensis X chromosome is unusual: it does not recombine in hermaphrodites and is transmitted from father to son. The mechanism that controls the production of females versus hermaphrodites is unknown but is dependent on maternal and larval environmental factors. Here we report the genome sequence and genetic map of A. rhodensis, placing over 95% of the sequence in seven linkage groups. Comparison of the seven A. rhodensis chromosomes to chromosomal assemblies of Caenorhabditis elegans and three other rhabditine nematodes identified deeply conserved linkage groups we call Nigon units, some of which have been maintained in all species analysed. Others have undergone breakage and fusion, and the A. rhodensis karyotype is the product of a unique set of rearrangements involving three Nigon units. The A. rhodensis X chromosome is much smaller than the autosomes, is less gene dense and is 3 to 4 times more polymorphic, reflecting its unique transmission history. Differential expression analyses comparing females and hermaphrodites, identified several candidate genes, including orthologues of C. elegans gld-1, tra-1 and dmd-10/11, that are potentially involved in the femalehermaphrodite sexual decision.

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