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Nature and function of the ecsoma in Tubulovesicula lindbergi (hemiuridae: platyhelminthes) D’Silva, Joseph


Some hemiurid parasites have a body proper, the soma, and a tail-appendage, the ecsoma, which is protractable out of, and retractable into, the soma. The nature and functions of the ecsoma. have not been investigated to date, and the hemiurid Tubulovesicula lindbergi was used to determine these. Since the parasite lives in the stomach of fish, pH and salinity may affect the protraction and retraction of the ecsoma. It was assumed that the soma and the ecsoma are not similar structures, and the tegument covering the two segments would be different. It was presumed that amino acid could be transported across the tegument of the ecsoma, and thus the ecsoma could function as an organ of absorption. Histological and histochemical methods -were employed to determine the differences between soma and ecsoma. Ecsomas were ligated, and whole worms were incubated in a medium containing radioactive glycine to determine if glycine could be transported across the tegument. Tests were conducted to detect the secretion of proteolytic enzymes by the ecsoma. The results showed pH and salinity had no effect on the protraction of the ecsoma. The somal tegument was a bi-layer and the ecsomal tegument a tri-layer. Acid phosphatase activity was found on the ecsomal tegument only. The arrangement of the muscle layers beneath the ecsomal tegument was the reverse of that in the soma. Three types of cells were found in the parenchyma in the soma and ecsoma. Parenchymal tissues occupied the hulk of the space in the ecsoma. The tegument of the ecsoma accumulated glycine against a concentration gradient. It secreted proteolytic enzymes. The results above indicated that the tegument on the soma and the ecsoma was, indeed, different. The tegument of the ecsoma was metabolically active, capable of absorbing glycine and secreting proteolytic enzymes. Therefore, the possibility of the ecsoma functioning in the absorption of amino acids from the surrounding media is discussed.

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