Abstract
Janicki and Rosen 1 showed that certain copepod crustaceans belonging to the genera Cyclops and Diaptomus were the first intermediate hosts of Diphyllobothrium latum. Okumura 2 found that Cyclops leukarti was the necessary first intermediate host of a species of Diphyllobothrium which he designated as “Sparganum mansoni”. Since considerable doubt has been indicated as to whether the spargana found in man and other vertebrates in the Orient belong to one of several species, the present writers have undertaken to study the life cycle of forms found in North China.
In one series of cases eggs from naturally infected dogs and cats have been utilized as the starting point of the experiment; in another, spargana commonly found in the somatic musculature of the hedgehog, Erinaceus dealbatus, have been fed to uninfected dogs and cats, resulting in the development of these larvae into adult worms, from which, eggs were readily obtained. Morphological study of the mature worms in these cases has shown that the former type belongs to the species Diphyllobothrium decipiens (Diesing), while the latter is D. erinacei (Rudolphi). The eggs were washed and incubated at temperatures from 15° to 35° C. Both species developed equally well. At the lower temperatures 21 to 30 days were required, while at 35° C. only 9 days for complete development and hatching.
Eight species of Cyclops were obtained in considerable number from the ponds, rice-fields and streams in the environs of Peking. None of these were ever found naturally infected with tapeworm larvae. The Cyclops were introduced one at a time into watch-glass cultures containing numbers of free-swimming coracidia and usually began immediately to ingest the coracidia, which showed no avoiding reaction. In 15 minutes such a Cyclops might swallow 20 to 60 larvae, which packed the whole digestive tract.
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