Regulates osmosis during embryonic development. Required for larval development and in particular is involved in larval molting. Co-localizes with ajm-1, an adherens junction marker in hypodermal cells and vulval toroids. In males, expressed in the precursor and mature sensory rays, the cloaca, and pre-anal ganglia and cephalic neurons. Also expressed in five cells in the valve region between the seminal vesicle and vas deferens of the somatic gonad. Expressed in the hypodermis of embryos prior to hatching and expression is enhanced in the hypodermis before each molt. Expressed during larval development in the excretory duct at the L1 stage, and during morphogenesis of the somatic gonad and vulva during the L3 and L4 stages with prominent expression in the uterine seam cell and toroidal vulE and vulD cells. Embryonic lethal with embryos displaying a fluid-filled appearance and dying at hatching. RNAi-mediated knockdown results in high levels of embryonic and larval lethality. Dead and dying mutants do not respond to touch, display extensive vacuolation, molting defects which include unshed cuticles and in particular male specific molting defects that prevent unfurling of the mature tail rays. Surviving mutants are shorter in length and display defective egg-laying and abnormal vulval morphogenesis. Belongs to the patched family.