Fasciola hepatica: A light and electron microscope study of sustentacular tissue and heterophagy in the testis

R. E. B. Hanna*, D. Moffett, G. P. Brennan, I. Fairweather

*Corresponding author for this work

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

In order to investigate cytolytic activity in the testis of Fasciola hepatica, flukes belonging to several different triclabendazole (TCBZ)-sensitive and TCBZ-resistant isolates, and wildtype flukes from field infections, were studied by light and electron microscopy with a view to identifying sites of heterophagy and macromolecular hydrolysis. At the periphery of the testis tubules in all the flukes examined, large euchromatic nuclei, each bearing a prominent nucleolus, were seen. These were invested with a thin cytoplasmic layer, extensions of which partially enveloped and probably supported the neighbouring spermatogonia. No lateral cell boundaries were identified in this tissue, possibly indicating syncytial organisation. The tissue, considered to be analogous to Sertoli cells in vertebrate testis, was identified as sustentacular tissue. It displayed cytoplasmic features consistent with protein/glycoprotein synthesis (through a granular endoplasmic reticulum-Golgi mediated mechanism) and intracellular digestion/heterophagy (through a lysosomal system). The intracytoplasmic hydrolytic activity of the sustentacular tissue probably serves to scavenge effete cells and cytoplasmic debris, to recycle useful molecules, to promote spermatozoon maturation and possibly to aid osmoregulation within the tubules. Certain protein-containing macromolecules synthesised in the sustentacular tissue may contribute to the seminiferous fluid, or have pheromonal activity. The presence of numerous mitochondria and abundant smooth endoplasmic reticulum is consistent with facilitation of inward and outward movement of micromolecular nutrients, metabolites including excretory products and water. In the sustentacular tissue of certain flukes with dysfunctional spermiogenesis, there was increased heterophagic and cytolytic scavenging activity. The cytoplasmic residual vacuoles remaining after the release of spermatids were also identified as possible sites for lysosome-mediated intracellular digestion and osmoregulation in the testis tubules of F. hepatica. (C) 2012 Elsevier B.V. All rights reserved.

Original languageEnglish
Pages (from-to)168-182
Number of pages15
JournalVeterinary Parasitology
Volume187
Issue number1-2
DOIs
Publication statusPublished - 08 Jun 2012

Keywords

  • INTERRELATIONSHIP
  • Testis
  • FINE-STRUCTURAL OBSERVATIONS
  • Fasciola hepatica
  • LIVER FLUKE
  • Sustentacular tissue
  • TREMATODA
  • CELLS
  • isolates
  • Light and electron microscopy
  • SPERMATOGENESIS
  • Triclabendazole-sensitive and -resistant
  • Heterophagy and apoptosis

ASJC Scopus subject areas

  • Parasitology
  • veterinary(all)

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