Studies on the ultrastructure and histochemistry of the lymph system in three species of amphistome (Trematoda: Digenea) Gigantocotyle explanatum, Gastrothylax crumenifer and Srivastavaia indica from the Indian Water Buffalo Bubalus bubalis

Abstract

The lymph system of three amphistome parasites from buffaloes, Gigantocotyle explanatum, Gastrothylax crumenifer and Srivastavaia indica was studied using light microscope histochemistry and electron microscopy. In each case the system comprised a single pair of main longitudinal vessels which gave rise to numerous sub-dividing lateral branches. Although the finer lymph channels associated with most internal systems, they did not penetrate the basement membrane of any organ. The lymph vessels were delimited by a unit membrane and separated from adjacent cells by interstitial material. The lymph fluid consisted of an amorphous proteinaceous, lipid-rich matrix, containing naked nuclei and granules of various sizes. Complexes of endoplasmic reticulum were frequently associated with the nuclei. No distinct Golgi bodies or mitochondria were evident. The granules noted throughout the lymph morphologically resembled autophagosomes and lysosomes. Autophagy within the lymph system presumably mobilizes amino acids for subsequent transport to tissues undergoing active protein synthesis. The lymph channels displayed an intimate relationship with the general parenchyma. In particular, numerous protrusions of lymph occurred into the cytoplasm of certain specialized parenchymal cells surrounding the pharynx. Within these ‘juxtapharyńigeal’ cells autophagic degradation of sequestered lymph cytoplasm apparently occurred. In the three species of amphistome studied, the lymph system appears to function in storage and mobilization of amino acids and possibly lipids. It may also serve to distribute other small molecules throughout the body. The detection of haemoglobin in the lymph system of G. crumenifer and S. indica, but not in Gigantocotyle explanatum, suggests a further role in oxygen storage and transport.

The tegument in Hemiuridae (Digenea: Hemiuroidea): structure and function in the adult

“…A similar function has been proposed for the lateral excretory canals of the cestode Moniezia expansa by HOWELLS (1969), the strigeid reserve bladder system by ERASMUS (1972), and for the amphistome lymphatic system. Studies by DUNN et al (1985) showed the latter to be concerned with the storage and mobilization of amino acids and possibly lipids, and the distribution of other small molecules around the body.…”

Characterization of the glutamate dehydrogenase activity of Gigantocotyle explanatum and Gastrothylax crumenifer (Trematoda: Digenea)

“…According to Dunn et al (1985), the lymph system of amphistomes appears to function in storage and mobilization of amino acids for subsequent transport to tissues undergoing active protein synthesis. Vitellaria are an active site of protein metabolism and also provide precursor for yolk and egg shell; therefore, intense localization of GLDH in these organs of amphistomes is not surprising.…”

The ecsoma in Hemiuridae (Digenea: Hemiuroidea): tegumental structure and function in the mesocercaria and the metacercaria of Lecithochirium furcolabiatum (Jones, 1933) Dawes, 1947

“…In contrast, there was no evidence to support the presence of a macromolecular uptake mechanism in the ecsoma of either the metacercaria, or the adult (MATTHEWS & MATTHEWS, 1988). The significance of autophagy in digenean metabolism has been discussed by THREADGOLD & ARME (1974) and DUNN et al (1985), who associated it with glycogenolysis in the parenchyma of Fasciola hepatica and with the mobilization of amino acids for protein synthesis within the amphistome lymphatic matrix respectively.…”