Genetic and phenotypic variations in egg shell colour of two ectotypes of Giant African Land Snail (Archachatina marginata var. saturalis)

Abstract

Data from the snail farm of the University of Calabar, Nigeria were collected and utilized to investigate the distribution and gene frequencies of egg shell colour of two ectotypes of Giant African Land Snails (Archachatina marginata var. saturalis), black skinned (BS) × black skinned mating group, and white skinned (WS) × white skinned mating group. The eggs collected were scored for the presence of yellow (Y p), light yellow (L p) and milky white (M p) egg shell colour. The egg shell colour distributions between the two ectotypes (BS × BS and WS × WS) were 46.50 vs. 3.77%, 42.68 vs. 48.11% and 10.83 vs. 48.11% for yellow, light yellow and milky white, respectively. In both ectotypes, the dominant gene for yellow, light yellow and milky white egg shell colour segregated at low frequencies (0.26 vs. 0.02, 0.24 vs. 0.31 and 0.06 vs. 0.31). The lowest value being yellow shell of the white skinned × white skinned mating group with frequency of 0.02, followed by milky white shell of the black skinned × black skinned mating group with frequency of 0.06. These values were much lower than the Mendelian value of 0.75. This is an indication that snails have not been purified through artificial breeding. Estimate of genetic distance between the two ectotypes were 0.060, 0.005 and 0.063 at yellow, light yellow and milky white loci, respectively. This shows that the ectotypes are closely related at the egg shell colour loci.

Variations in reproductive and egg traits correlation estimates of two strains of Archachatina marginata snails (var. ovum and var. saturalis) and crosses

“…This could imply that eggs laid by the heterozygous model were hybrids and contained the genes responsible for the egg shell colours of the homozygous crosses. The colours of egg shells were at variance with the yellow egg shell colour reported by Otu (2016) and the light yellow and milk white egg shell colours reported by Ibom et al (2017) for the black skinned and white skinned ectotypes of A. marginata var. saturalis snails.…”