Unusual Cilia in the Microfilaria of Dirofilaria immitis

Abstract

Studies of the ultrastructure of the Dirofilaria immitis microfilaria revealed paired cuticularized channels in the cephalic space and in the region posterior to the anal vesicle. Each of the cephalic channels contains 8 to 91 cilia, but only one cilium is present in the shorter, caudal channels. The cilia, in all channels, lack basal bodies and have various microtubular patterns ranging from 1+11+4 to 9+2. These cilia may be sensory structures, possibly being the precursors of the amphids and the phasmids. The ciliary channels probably correspond to the "Mundgebilde" and the "Schwanzgebilde" which were described by previous investigators. True cilia, with a microtubular pattern differing from 9+2, were first reported in a sense organ of a free-living marine nematode, Thoracostoma californicum, by Hope (1965). Similar structures were described by Roggen, Raski, and Jones (1966) in the sense organs of the free-living soil nematode Xiphinema index. Ross (1967) described cilia as dendritic modifications in the labial, cephalic, and cervical papillae, and in the amphids of the third and fourth stage juveniles of Haemonchus contortus. Ultrastructural studies of Dirofilaria immitis microfilariae have revealed that aberrant cilia are also present in the anterior and