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Dictionary of Ichthyology |
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spiral valve = a spiral or helical fold in the midgut of Petromyzontiformes, Elasmobranchii, Holocephali and some primitive Teleostomi. Functions to increase the surface area for processing food without lengthening 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. |
