Three myxosporeans found in the cranial and branchial tissues of rainbow trout in california

Ronald Hedrick, A. Wlshkovsky, J. C. Modin, R. J. Toth

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Three myxosporeans were encountered in the cranial tissues of a California population of rainbow trout Oncorhynchus mykiss examined for the presence of Myxobolus cerebralis, the causative agent of whirling disease. Typical spores of M. cerebralis and a previously undescribed species of Myxobolus were found in the cranial tissues prepared by the pepsin HCl-trypsin digestion method. Henneguya zschokkei was also detected in digest preparations of cranial tissues, but was more numerous when branchial cartilage was included in the preparations. Microscopic examinations of tissues of individual rainbow trout showed occasional infections with both myxobolid species. Myxobolus cerebralis trophozoites and spores were found in the cranial and gill cartilage, and Myxobolus sp. was found in the brain and spinal cord. Henneguya zschokkei was also found within granulomas in the connective tissues below the gill arch. Both M. cerebralis and H. zschokkei were associated with a chronic inflammatory response in their respective tissues. In contrast, the Myxobolus sp. spores were found in pockets within the nervous tissues with no detectable host response. The spore measurements, calculated from fresh digests of infected tissues for the three myxosporeans (N = 20), for length x width x thickness in micrometers (SD) were 11.7 (0.6) without tails and 42.6 (5.2) with tails x 7.7 (0.8) x 7.0 (0.1) for H. zschokkei, 9.9 (0.4) x 8.4 (0.1) x 6.5 (0.3) for M. cerebralis. and 12.7 (0.7) x 10.5 (1.0) x 9.5 (0.8) for Myxobolus sp. Examined under scanning electron microscopy, the latter two species were morphologically similar although distinctive in size.

Original languageEnglish (US)
Pages (from-to)55-62
Number of pages8
JournalJournal of Aquatic Animal Health
Issue number1
StatePublished - Jan 1 1991

ASJC Scopus subject areas

  • Aquatic Science


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