P. sulcatus is an ovoviviparous species that rears its embryos in large brood pouches found on the body female individuals (Houbrick 1987). The brood pouch formed by an epithelial invagination, is a feature defining members belonging to the family Planaxidae (Houbrick 1987). There are three different types of brood pouches found in the Planaxids (Houbrick 1987). The most complex type is the one found on the Planaxis which is consists of a large, primary chamber subdivided into many secondary, lamellar chambers that fill both sides of the head-foot (Houbrick 1987).

In P. sulcatus, embryos are found throughout the entire brood pouch and may comprise several juvenile cohorts of different growth stages (Houbrick 1987). The more advance embryos are located in the dorsal portion of the chamber (Houbrick 1987). Each embryo is contained in a thin egg capsule from which it breaks out prior to expulsion from the brood pore in the right side of the neck region (Houbrick 1987).

P. sulcatus is an example of a species of prosobranch gastropod capable of utilising several reproductive modes in response to environment or geographical difference (Houbrick 1987). The stage at which embryos hatch from the brood pore and the kind of development that follows is known to differ among populations found in different geographical regions (Houbrick 1987). Embryos may hatch at the veliger stage to become planktontrophic larvae, at a late veliger state as lecithotrophic larvae or be brooded through all embryonic stages to hatch as well developed juvenile snails (Houbrick 1987; Ohgaki 1997). Planktotrophic larvae needs to feed on plankton with varying amount of time in the pelagic column (Lau 2004). Non-planktontrophic larvae, such as the lecithotrophic larvae, are unable to feed on plankton and thus have to depend entirely on other reserves such as the egg yolk for energy (Lau 2004). Alternatively, the larvae can develop in the female’s brood pouch and hatch as fully developed crawling juveniles (Lau 2004).

It is believed that there may be two cryptic species of P. sulcatus: an Indian Ocean species observed in Pakistan and in the Persian Gulf with ovoviviparous (direct development into crawling young) development and an Indo-Pacific species observed in Australia, Japan and Hong Kong with indirect development, including partial brooding followed by a planktonic phase (Houbrick 1987; Ohgaki 1997).