Histological section of Gill arch in (A) Carassius auratus and (B) Astronotus ocellatus show (1) gill raker (2) submucosa, (3) adipose tissue, (4) efferent branchial arterioles, (5) afferent branchial artery, (6) primary lamellae, and (7) secondary lamellae (H & E, 40X).