SEM observations on nematode cuticle penetration by Bacillus penetrans.

Because of tile small size of the endoparasite, Bacillus #enetrans (Thorne, 1940) Mankau, 1975 (2), it has been difficult to stttdy, and disagreement about the method of its penetrat ing nematode cuticle has appeared in the literature (3). Concepts previously presented (3) are herein substantiated by en [ace scanning electron micrographs (SEM) of several infected specimens of Dolichodorus from Mozambique. Specimens routinely prepared for taxonomic studies (4) had B. penetrans sporangia (spores) attached to the lip region (Fig. 1, 3, 4). Sporangia are most frequently attached to the anterior or neck region of nematodes [Fig. 2 (Merlinius tesseUatus)] but they may occm" anywhere on tile body. T h e large, disc-like lip region of Dolichodorus sp. apparently provides sufficient surface area for sporangial a t tachment in that location. T h e sporangium attached to the lip region of the nematode in Fig. 1 has blocked tile buccal opening and surrounding pits within which labial papillae apparently occur. If such sporangia became attached with sufficient force that the nematode could not dislodge them with its substantial stylet, the nematode would probably starve because of the parasitism. T h e attached sporangium in Fig. 1 is about 3.2 /zm diam and consists of a central, raised