Dictionary of Ichthyology  

rectum = the terminal portion of the intestine.

Guts of Protopterus from Kingsley's "Textbook of Vertebrate Zoology, 1906. C = caecum, G = gall bladder, HV = hepatic vein, L = liver, O = oesophagus, OD = oviduct, PV = pyloric valve, R = rectum, RD = renal (mesonephric) duct, S = stomach, SP = spleen, SV = spiral valve, V = vent. Photograph by Brian W. Coad.

Canadian Museum of Nature
www.briancoad.com