Abstract
Sex determination is an important area of research, which has always had an intriguing aspect in evolutionary and developmental biology. Quantitative trait locus (QTL) mapping for sex will be helpful in clarifying the sex determination system. In this study, the sex QTL mapping of the swimming crab (Portunus trituberculatus) was performed based on a high-density linkage map, and a highly significant QTL specifically mapped on a single linkage group (LG) was firstly identified (LG24, LOD > 14). Twenty markers in the QTL region showed significant associations with sex by association analysis, of which heterogametic genotypes in males supported the XY sex determination mechanism. Two sex-specific markers at the family level were identified via segregation distortion analysis, which were known to be the most closely linked to the sex of P. trituberculatus. Based on sex marker sequences (Marker3840, Marker20320, and Marker10494), three potential sex-related genes were identified, and the quantitative real-time PCR results suggested that these genes were important in spermatogenesis or sex characteristics in males. Our results will contribute to the fine-mapping of sex-determining genes and clarify the sex determination mechanism of P. trituberculatus.
Highlights
The swimming crab (Portunus trituberculatus) is distributed widely along the coastal waters of China, Korea, Japan, and other East Asian countries (Lv et al, 2013), and has become one of the most important economic species with an annual production of 605,632 tons (Ren and Pan, 2014; Food and Agriculture Organization [FAO], 2016; Meng et al, 2018)
Apart from Marker46734, 19 markers segregated in the male, suggested that the sex determination of the crab may belong to the male heterogametic XY system
As far as we know, this is the first time that sex Quantitative trait locus (QTL) has been located on a single chromosome in the crab, which suggested that LG24 may be a potential sex chromosome
Summary
The swimming crab (Portunus trituberculatus) is distributed widely along the coastal waters of China, Korea, Japan, and other East Asian countries (Lv et al, 2013), and has become one of the most important economic species with an annual production of 605,632 tons (Ren and Pan, 2014; Food and Agriculture Organization [FAO], 2016; Meng et al, 2018). The mechanisms of sex determination are remarkably diverse and are controlled by genetic and/or environmental factor (Ford, 2008). The sex determination system of some crustaceans can be identified by karyotype analysis (Abu-Almaaty, 2017; Blackmon et al, 2017). Four species (Eriocheir japonica, Hemigrapsus sanguineus, Hemigrapsus penicillatus, and Plagusia dentipes) were believed to have an XY sex determination system via karyotype analysis (Niiyama, 1937, 1938, 1959; Lecher and Noel, 1995). A recent study questioned the reliability of karyotype analysis for inferring sex determination, as the centromeres could not be identified in some of the chromosomes (Lee et al, 2004)
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