Abstract
H. B. Ward and J. Mueller 1 reported exophthalmia in the troutfry. Their examination showed the presence of larvae of an unidentified trematode in the muscles of the eyes, at the base of the fins and in some cases in the optic nerves of the protruding eyes. Exophthalmia is prevalent amongst the fish at the State Fish Hatchery at Madison, Wisconsin. Those affected are found to be free from parasites and only those that have been injured are infected with fungus. The condition does not appear until the yolk sac has been absorbed and the fry begin to eat. Large numbers die at this stage of development, and a high percentage of those that die show exophthalmia. The number that die, and the number showing exophthalmia as well, decreases as they grow and summer approaches, only to increase again the following winter and spring when they are a year old. Histological and experimental study show the exophthalmia to be the same in the adult trout and in the fry.
Numerous papers have appeared in the literature describing thyroid diseases of the trout and other fishes, both wild and domesticated. Bonnet 2 first described a tumor of the region of the gill junction, and Scott 3 first described such a tumor as a carcinoma of the thyroid. M. Plehn, 4 L. Pick, 5 Jaboulay, 6 Gaylord and Marsh, 7 Marine and Lenhart, 8 Müller 9 and Johnstone 10 have described similar conditions. In all cases reported, hyperplasia of the thyroid has been indicated externally by a tumor or by areas of hyperaernia. The fry examined by the writers showed no external indication of enlargement of the thyroid.
Get full access to this article
View all access options for this article.