A FREEZE-FRACTURE STUDY OF THE CUTICLE OF ADULT NIPPOSTRONGYLUS-BRASILIENSIS (NEMATODA)

The surface of the cuticle of adult Nippostrongylus brasiliensis has b een studied by means of the freeze-fracture technique and by transmiss ion electron microscopy. Some of the surface coat appears to have been shed from the surface of the cuticle of adults fixed in situ in the i ntestine of its host and from the surface of individuals removed from the intestine and freeze-fractured. Freeze-fracturing the cuticle of i ndividuals removed from the host has shown that this surface coat vari es in thickness from 30 to 90 nm. The epicuticle is about 20 nm thick and cleaves readily to expose E- and P-faces. The P-face of the epicut icle possesses a small number of particles, similar to intra-membranou s particles, whilst the E-face possesses a few, widely scattered depre ssions. Despite the presence of these particles the epicuticle is not considered to be a true membrane. Freeze-fracturing the remainder of t he cuticle has confirmed its structure as described by conventional tr ansmission electron microscopy. Clusters of particles on the P-face of the outer epidermal (hypodermal) membrane and corresponding depressio ns on the E-face of the membrane are thought to be associated with poi nts of attachment of the cuticle to the epidermis (hypodermis). No dif ferences in appearance of the cuticle and its surface layers were obse rved in individuals taken from 7-, 10-, 13- and 15-day infections.