Tasmanian Live-bearing Seastar (Parvulastra vivipara) - Requested by Anonymous
The Tasmanian Live-bearing Seastar is a tiny, uniformly orange-yellow seastar, up to 15 mm across. It is endemic to south-east Tasmania. Parvulastra broods juvenile starfish in a brood chamber (aka “live birth” aka viviparity). That, is the adult “carries” either internally or externally several tiny juvenile starfish with it until they are ready to move off on their own as full adults.
But what motivates the exit? Those juvenile starfish are cannibals! So, as soon as the brooded juveniles develop a mouth they begin feeding on their siblings in the body cavity! Byrne speculated on one reason that juveniles may vacate in order to avoid being fed upon by their larger siblings. Thanks to the intragonadal cannibalism however, sometimes you get a really big one which continues to grow inside the parent. Ultimately reaching a size at which it cannot physically escape on its own.