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The Size Attained by Hymenolepis diminuta in Different Host Species

1954; American Society of Parasitologists; Volume: 40; Issue: 1 Linguagem: Inglês

10.2307/3274261

1937-2345

Clark P. Read, Marietta Voge,

Parasite Biology and Host Interactions

It might be surmised that the size attained by a tapeworm in a particular vertebrate host will be related to the size and species of the host animals. However, little quantitative data to support this view are actually available. Larsh (1946) showed that Hymenolepis nana attained a greater length in the hamster than in the mouse; in these experiments absolute comparisons are still open to the criticism that the two groups of hosts harbored quite different numbers of worms. Beck (1951) has demonstrated the usefulness of singly-established worms in the study of the biological relationships of Hymenolepis diminuta. In the present experiments individual hosts of several species were infected with single cysticercoids of H. diminuta, and an evaluation was made of the size attained in these various hosts. Volume of tapeworm tissue was used as the unit of measure of size attained. MATERIALS AND METHODS The tapeworm eggs for all experiments were obtained from the droppings of one rat infected with H. diminuta of the Rice Institute strain. Cysticercoids were obtained by feeding eggs to laboratory-reared Tenebrio molitor. In each series of host animals of the same species the cysticercoids used for infection were obtained from one beetle. Each host was lightly anesthetized with ether and a single cysticercoid was administered per ora with a pipette. All hosts were autopsied twenty days after infection. (The senior author has found the pre-patent period of H. diminuta to be 19 to 21 days in the hosts used in the present work.) The worms were washed in several changes of Tyrode's solution and blotted carefully on filter paper. Volume of worm tissue was determined by adding each worm to a 5.00 ml. burette, graduated to 0.01 ml., partially filled with Tyrode's solution. The difference in readings before and after addition of each worm was recorded as tissue volume. Tyrode's solution was used because it has been previously shown that the wet weight of H. diminuta does not change in this medium (Chandler, Read, and Nicholas, 1950). Duplicate determinations with the individual worms of one series of ten worms yielded a maximum error of 0.04 ml. No other measurements of worm size were made. EXPERIMENTS In a preliminary experiment twelve gray mice, Mus musculus, were given single cysticercoids. At autopsy twenty days later only one host was found to be harboring a worm. In a second experiment thirty-six albino mice, 60 to 73 days old, were used. Half of this group were males and half females. Six males and six females were given cysticercoids. The remaining twenty-four mice were given 0.05 ml. of 10% tincture of opium intraperitoneally; thirty minutes later each of these mice was given a cysticercoid. At autopsy the mice not treated with opium were free of worms while every individual in the treated group harbored a single