| Cysts of Myxobolus pendula from the gill arch of Semotilus atromaculatus were examined using light and electron microscopy. The host connective tissue underwent remodelling and vascularisation in response to the infection. Inflammatory cells lay beneath this connective tissue and surrounded a parasite-derived extracellular matrix (ECM), composed of collagen fibres suspended in an amorphous material. This ECM, produced by an underlying layer of specialized myxozoan cells was resistant to invasion by leukocytes. Secretion of a complex ECM by M. pendula as a protective barrier is a novel observation among cyst-forming Myxosporea.; Digestion of whole cysts of M. pendula in cyanogen bromide generated an insoluble residue. Total amino acid analysis shows that the amino acid composition of this residue has a higher proportion of ASX, GLX and LYS, and a lower proportion of GLY and other hydrophobic residues than a similarly isolated protein from fish, suggesting that the major component is parasite-derived. |
