Morphogenesis of the proboscis hooks of an archiacanthocephalan, Moniliformis moniliformis (Bremser 1811) Travassos 1915.

Proboscis hooks of Moniliformis moniliformis were noted first as small protrusions on developing proboscides of 20- to 28-day-old acanthellae from hemocoels of experimentally infected cockroaches (Periplaneta americana). On the basis of proximity, residual connecting strands of tissue, and ultrastructural similarity, origin of the hooks has been determined to be from primordial muscle tissue. During development, primordial proboscis hooks extended into hypodermal tissue, but remained separated by the basement membrane and a characteristic space. Within this space, under the curvature of the hook, fibrous material began to accumulate at about 38 days during development. The fibrous material appeared to be produced at the distal end of the primordial hook as evidenced by the appearance of organelles in that area, and the compact, parallel nature of fibrous material immediately adjacent. Upon completion of development, the proboscis hook of the 46- to 54-day-old acanthella was observed to consist of a central core of parallel fibrous material, an outer layer of crisscrossed fibers, and a thin covering of hypodermis and cuticle.