Summary
The intercordal hypodermis of the pig whipworm, Trichuris suis possesses a cellular organization. Although the hypodermal cells are metabolically active they are not equipped to carry out extensive protein synthesis in the adult parasite. They are intimately associated with the overlying cuticle being separated from the latter only by a triple-layered membrane. A stable mechanical relationship appears to be maintained between cuticle and hypodermis by the presence of short hypodermal projections which are anchored in the basal layer of the cuticle. Fibres which traverse the hypodermis from the musculature to the cuticle may also contribute to this stability as well as allowing the muscles to pull on the cuticle. The inclusion of glycogen and lipid in the hypodermal cells indicates that they may also serve as storage centres.
The nerve axons are evident as a number of closed membrane-bound profiles amongst the cytoplasmic branches of the median hypodermal cord. They are unmyelinated and contain microtubules, two types of vesicles and tiny mitochondria. The possible role of these axonal inclusions in nervous transmission is discussed.
Two distinct types of myofilaments (myosin and actin) characterise the contractile, myofibrillar region of the somatic muscle cells. These are arranged longitudinally but do not show any cross-striations so that the muscle does not fit either the smooth or striated category. This morphological pattern is compared with that resolved in other nematodes.
The amyofibrillar region of the muscle takes the form of a sarcoplasmic bulb and harbours the nucleus and an abundant supply of glycogen. While it appears to play no part in muscle contraction it serves as an important depot of metabolic reserves which may be utilised during muscular activity.
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Jenkins, T. Electron microscope observations of the body wall of Trichuris suis, Schrank, 1788 (Nematoda: Trichuroidea). Z. Parasitenk. 38, 233–249 (1972). https://doi.org/10.1007/BF00329600
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DOI: https://doi.org/10.1007/BF00329600