Great Lakes Fishery Commission

Genetic control strategies for other pests include attempts to bias the reproductive sex ratio towards males so that a population decreases in size or is eliminated altogether due to a lack of females. Because these sex-ratio distortion systems pests are most effective once other control measures have reduced abundance, genetic manipulation of sex ratios could be an effective complement to existing sea lamprey control. However, a genetic basis for sex determination in lampreys remains elusive. Environmental sex determination (ESD) in lampreys has been suggested, but the evidence is equivocal, and no fish species with only ESD is known. Using a two-pronged genomics and transcriptomics approach, we found evidence that the germline-specific region (GSR) of the genome, the part jettisoned from somatic cells during embryonic development, holds the key to lamprey sex determination. 1) Using whole genome sequences from fin clips of >200 sea lamprey, we found no sex-specific differences in the somatic genome. 2) However, analysing RNA-sequence data from gonads sampled across developmental stages, we identified 638 germline-specific genes that are highly expressed only in males, and it appears that these genes have known functions in sex determination and differentiation in other vertebrates. Therefore, we conclude that the GSR plays an important role in testicular differentiation, and we propose a mechanism for how environmental and genetic factors work together to control lamprey sex.

Project Datasets

Other Project Products