B. truncatus is a hermaphrodite – it produces both male and female gametes – and is capable of self-fertilization

It is also a tetraploid - has four times the haploid number of chromosomes in its cell nuclei.

The species exists in two sexual polymorphic forms - euphallic and aphallic

Aphallic individuals lack the male copulatory organ. They are capable of self-fertilization and are only able to outcross as females.

Research using microsatellite genetic markers suggest that B. truncatus snails preferentially self-fertilize rather than outcross. 

Preferential selection for 'selfing' over 'outcrossing' is not unique within the genus as experimental microsatellite data has shown that B. forskalii also favours reproduction through self-fertilization.