Practice question

Veliger represents characteristic free-swimming planktotrophic larva of marine molluscs, directly derived from trochophore via development of expanded ciliated velum. It possesses two large ciliated lobes forming velum for swimming and particle capture, together with developing foot, mantle secreting protoconch, shell gland and visceral anlage. Commonly found in Gastropoda, Bivalvia and Scaphopoda, while Cephalopoda and many freshwater gastropods lost it through direct development with yolky eggs. Trochophore precedes veliger, connecting annelid-mollusc shared ancestry within Spiralia, indicating indirect marine development and dispersal before metamorphosis into benthic juvenile stage with shell.