Myxidium mackiei (Myxosporea) in Indo-Gangetic flap-shelled turtles Lissemys punctata andersonii: parasite–host interaction and ultrastructure

Diseases of Aquatic Organisms

K. L. Helke¹  S. L. Poynton¹ 

关键词: Myxosporea;    Turtle;    Kidney;    Ultrastructure;   

DOI  :  10.3354/dao063215

学科分类：生物科学（综合）

来源: Inter-Research

【 摘 要 】

ABSTRACT: Myxosporeans are common parasites of fish, and uncommon parasites of amphibians, reptiles and invertebrates, that can cause significant morbidity and mortality. The common genus Myxidium infects the excretory system of turtles, yetknowledge of its pathogenicity in these hosts is limited. We offer new knowledge of morphological and ultrastructural aspects of host–parasite interactions in Myxidium infections from our recent diagnostic investigations on captive freshwaterturtles listed in CITES (Appendix II). We investigated the cause of death of 2 adult Indo-Gangetic flap-shelled turtles Lissemys punctata andersonii from a zoo collection. After post-mortem examination, tissues were processed for histopathology,and special stains were used to demonstrate morphology of myxosporean spores. Additional kidney tissue, immersion-fixed in formalin, was processed for transmission electron microscopy. Both turtles were infected with a myxosporidian, Myxidiummackiei, in the kidney, which occluded 5 to 10% of the renal proximal convoluted tubules. The polysporic plasmodia contained pairs of developing and mature spores. Each mature, spindle-shaped spore had 2 asymmetric valves (1 overlapping, 1overlapped), with 10 to 13 and 10 to 14 longitudinal ridges per valve, and 2 polar capsules each containing a polar filament with 4 to 5 turns. A pair of spores, each surrounded by a membrane-bound electron-lucent matrix, lay in an enclosing cell withinthe plasmodium. Regions of the parasite–host interface consisted of undulations of the parasite surface, with intense pinocytotic activity beneath, intermingled with the hosts’ microvilli, and endocytotic channels at the apex of renal epithelialcells. The microvilli of the renal epithelial cells of infected tubules were frequently sheared or compressed, or occasionally missing; we did not detect other pathology induced by the parasite. Our report of M. mackiei in L. punctata is anew host record. Both individuals also had disseminated pale yellow nodules (bacterial granulomas) present in lung, heart, kidney, and skeletal muscle, and both were infected with coccidia (tentatively identified as Eimeria sp.) in multiple organs.The cause of death for one turtle was septicemia, but remained unknown for the other individual.

【 授权许可】

Unknown