Mammary gland gestation, serum progesterone remains at a stably high concentration so signaling through its receptor is continuously activated. As one of the transcribed genes, Wnts secreted from mammary epithelial cells act paracrinely to induce more neighboring cells' branching. When the lactiferous duct tree is almost ready, "leaves" alveoli are differentiated from luminal epithelial cells and added at the end of each branch. In late pregnancy and for the first few days after giving birth, colostrum is secreted. Milk secretion (lactation) begins a few days later due to reduction in circulating progesterone and the presence of another important hormone prolactin, which mediates
Milk shark known parasite of this species is the copepod "Pseudopandarus australis". There is some evidence that male and female milk sharks segregate from each other. Like other requiem sharks, the milk shark is viviparous; females usually have a single functional ovary (on the left) and two functional uteruses divided into separate compartments for each embryo. The details of its life history vary across different parts of its range. Females generally produce young every year, though some give birth every other year or even every third year. Mating and parturition take place in spring or early summer (April to July) off western