Specificity of caryophyllaeid cestodes for their intermediate hosts.

The species of a caryophyllaeid cestode genus exhibit considerable variation in specificity for their oligochaete annelid intermediate hosts. Larvae of Monobothrium ulmeri, Monobothrium hunteri, and Biacetabulum biloculoides were specific for one annelid species. Glaridacris catostomi procercoids developed in members of 6 annelid species of 2 families. Monobothrium ingens developed in 3 genera of Tubificidae and Biacetabulum infrequens occurred in members of 4 tubificid genera. Glaridacris confusa developed in 3 species of 2 annelid families. The major factor affecting specificity involved hatching of the cestode eggs. Other contributing factors were host cellular and chemical responses and physical size of the annelid species. Caryophyllaeid cestodes are unsegmented helminths which commonly parasitize catostomid and cyprinid fishes in North America. Experimental studies on life cycles and larval development of American caryophyllaeids have been made by McCrae (1961), Calentine and Frederickson (1965), and Calentine (1967). Other experimental studies include Kennedy (1965) and Kulakowskaja (1962). Egg development occurs in water and the annelid intermediate hosts acquire infections by eating embryonated eggs. Procercoid larvae develop in the oligochaete's body cavity or seminal vesicles and are characterized by a scolex, primordia of gonads, and a cercomer. Fishes become infected by eating annelids containing procercoids. The present study was conducted in order to elucidate the nature of intermediate host specificity for seven North American caryophyllaeid species. MATERIALS AND METHODS Cestodes and fish hosts were: Biacetabulum infrequens Hunter, 1927, and Monobothrium ulmeri Calentine and Mackiewicz, 1966, from Moxostoma anisurum (Raf.), 1820, St. Croix River, Lakeland, Minnesota; Glaridacris confusa Hunter, 1929, and Monobothrium ingens Hunter, 1927, from Ictiobus bubalus Raf. , 1818, St. Croix River, Lakeland, Minnesota; and Biacetabulum biloculoides Mackiewicz and McCrae, 1965, Glaridacris catostomi Cooper, 1920, and Monobothrium hunteri Mackiewicz, 1963, from Catostomus commersoni (Lacepede), 1803, Willow River, Lake Mallilieu impoundment, Hudson, Wisconsin. Cestode eggs were collected from gravid worms refrigerated in tap water, or by dissection. Following embryonation at room temperature, eggs Received for publication 18 November 1969. * Supported by Public Health Service grant R01 AI06605. were stored in tap water at 5 C. All feeding experiments were conducted at room temperature. Annelids were exposed to cestode eggs in a mud medium, usually for 24 hr. Hosts were then removed and cultured in mud under aeration at room temperature. Infected annelids were fixed in hot 70% alcohol or in Bouin's fluid; procercoids were fixed in AFA. All whole mounts were stained with Mayer's paracarmine. Annelids used were: Aulodrilus pigueti Kowalewski, 1914; Branchiura sowerbyi Beddard, 1892; Ilyodrilus (Tubifex) templetoni (Southern), 1909; Limnodrilus hoffmeisteri Claparede, 1862; Peloscolex multisetosus (Smith), 1900; and Tubifex tubifex (Muller), 1774; of the Tubificidae, and Dero digitata (Muller), 1773; Nais communis Piguet, 1906; Ophidonais serpentina (Muiiller), 1773; Stylaria lacustris (L.), 1767; and Uncinais uncinata (0rsted), 1842, of the Naididae.