Correlation, regression estimates and heterosis of <i>Archachatina marginata</i> snails in Calabar, Nigeria

Abstract

Eighty sexually mature Archachatina marginata snails, forty each of the black skinned and white skinned ectotypes were used in a study to estimate  heterosis, correlation and regression. Data collected on the snails and their eggs included body weight (BWT), shell length (SLH), shell width (SWH), “mouth” length (MLH) and “mouth” width (MWH); and egg weight (EWT), egg length (ELH) and egg width (EWH), respectively. These data were used to estimate correlations between pairs of traits, heterosis and to predict weight from other morphometric traits among three mating groups [black skinned x black skinned (BAM X BAM), white skinned x white skinned (WAM X WAM) and their cross BAM X WAM)]. Results obtained from the study showed that evaluated traits expressed strong, positive and highly significant (P<0.01) correlation values that ranged from r_p = 0.86 to r_p = 0.99  among  the snails mating groups. The correlation values of traits evaluated on eggs laid by these snails ranged from mild (rp = 0.49) through moderate (r_p = 0.59, r_p = 0.70) to strong/close (r_p = 0.89). Regression estimates values obtained ranged from mild (1.30) to high (6.25), and shell width best predicted hatchlings body weight in the black skinned x black skinned (BAM X BAM) mating group, while “mouth” length best predicted  hatchlings body weight in the white skinned x white skinned (WAM X WAM) mating group. Traits evaluated for percent heterosis expressed positive and significant (P<0.05) values between the mating groups, with the crossbred (BAM X WAM) mating group having advantage over the purebred  (BAM X BAM and WAM X WAM) mating groups. It could therefore be concluded that in the face of appropriate selection programme, heterosis can be exploited to improve snails reproductive and growth traits. It can thus be recommended that having information regarding the association of weight with other contributing traits/parameters is crucial before starting any breeding programme.

Keywords: Correlation, Estimates, Heterosis, Regression, Snails