The infrastructure of the orthochromatic mucous cells of some British lumbricids (Annelida)

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Abstract
The infrastructure of the orthochromatic mucous cells of 11 British lumbricids is described. The prominent secretory globules show species variation with standard fixation.In four genera the core material exhibits consistent and characteristic electron dense ultrastructural patterning, the four types being described, and species within these genera show specific differences. Such patterned globules are termed heterogeneous, in contrast to the homogeneous globules of the other two genera. The generic and specific ultrastructural patterns line up well with, and support, the modern, revised lumbricid taxonomy.The electron dense heterogeneity is first visualized at the mature Golgi face and the patterning is eliminated after proteolytic enzyme treatment, suggesting that the dense areas within the globule reflect the protein sites within the mucus, the final elaboration of which takes place within the polarized Golgi.No mucus extrusion mechanisms were observed and it is suggested, from the positioning of the supporting cell tonofilaments and the body wall musculature, that extrusion accompanies locomotory activities.A suggestion as to the possible function of a type of mucus with clear specific differences, as evidenced by the ultrastructure, is advanced.