Mendelian trait/disorder: yes

Mode of inheritance: Autosomal

Considered a defect: no

Key variant known: no

Inheritance: From the results of strategic crosses, Ky et al. (2016) concluded that the segregation of shell colour is consistent with a single-locus "three-allele model for shell trait, whereby the black wild-type allele is dominant to the red coloration, which is dominant to the white shell".