MORPHOLOGICAL SPECIALIZATIONS OF THE DIGESTIVE-TRACT OF ZACRYPTOCERUS-ROHWERI (HYMENOPTERA, FORMICIDAE)

Light, scanning, and transmission electron microscopy are used to exam ine the morphology and ultrastructure of the peculiar digestive tract of the turtle ant, Zacryptocerus rohweri. The proventriculus is heavil y sclerotized and covered with clusters of small spines. Narrow spine- lined channels converging at the opening to the midgut act as a fine f ilter of food; particles >12.5 mu m are unable to pass through the pro ventriculus. In the midgut, ultrastructural study reveals bacteria amo ng the microvilli of midgut epithelial cells. The hindgut of Z. rohwer i consists of an enlarged, dark-colored pouch filled with masses of ba cteria of three major morphotypes. A thick layer of circular muscle an d deep infoldings of the epithelium greatly increase surface area for absorption. Newly emerged individuals appear to acquire these microorg anisms by soliciting material from the abdomen tip of other older work ers in the colony. Whether or not the hindgut bacteria are true symbio nts is unknown; their acquisition and presence suggest that they may s upplement the ants' limited, liquid diet by supplying essential amino acids and other nutrients. (C) 1997 Wiley-Liss, Inc.