Head Organs and Cephalic Glands of Cleidodiscus mirabilis

Abstract

Detailed information on the genus Cleidodiscus Mueller, 1934, has been confined heretofore to taxonomy and general morphology (Mueller, 1934, 1937; Mizelle, 1938; Mizelle and Cronin, 1943). Head organs and cephalic glands were selected presently for detailed study because of a paucity of information concerning them, their conspicuous nature in life and confinement to a small area. Specimens were collected from the gills of the yellow cat (Pilodictis olivaris Rafinesque) and the blue cat Ictalurus furcatus Cuvier and Valenciennes) which were recovered from Fort Loudoun Lake, and the Tennessee River at Knoxville, and Lenoir City, Tennessee. Live specimens were obtained from the majority of the hosts which were examined within thirty minutes after removal from the lake. Additional live material was provided for four to six hours by aeration. The aerator consisted of a one-liter suction flask two-thirds full of water and fitted with a rubber stopper containing a single hole through which air was drawn by suction via a glass tube extending to the bottom of the flask. Dead specimens, removed from hosts dead for several hours, were fixed in Carnoy's solution. Some of these were stained with Delafield's hematoxylin and mounted in Piccolyte;3 others were mounted unstained in glycerine-chromate gel (Yetwin, 1944). Living specimens were fixed in Carnoy's, Zenker-formol, and Flemming's solutions. Zenker-formol fixed specimens proved the most satisfactory since there was less shrinkage and more cellular detail was visible. Specimens for histological study were imbedded in paraffin and sectioned transversely, frontally, or sagittally, stained with Heidenham's iron hemotoxylin, and mounted in piccolyte. Specimens for examination alive were mounted in water on slides, under cover slips ringed with vaseline, and for the most part remained alive for two to three hours. Examination was made with the phase-contrast microscope. Best examinatiot results were obtained with the Spencer dark contrast-medium 4 mm. objective and with the dark contrast-medium 1.8 mm. oil immersion objective. Photomicrographs were made of the head region of living whole mounts and compared with similar photomicrographs of fixed whole mounts (Figs. 1 and 2). The pictures were made with the phase-contrast microscope