The effect of low temperatures on the motility of diphyllobothrium latum plerocercoids.

The effect of low temperature exposure on the motility of Diphyl-lobothrium latum plerocercoids was studied, with the particular aim of finding the exposure that immobilizes all the larvae in fish freezing. Both isolated larvae immersed in normal horse serum and larvae enclosed in pieces of muscle tissue of the size of 1 cm3 were tested. The pieces of tissue containing a larva were placed in the middle of a plastic beaker filled with densely packed minced fish flesh. In the central part of this phantom, where the plerocercoids were situated, the temperature decline was considered to take place in the same way as in the interior of a whole fish. A total of 200 isolated larvae were tested, and a temperature of −14° G was found to have a fully immobilizing effect on them. The number of plerocercoids frozen enclosed in muscular tissue was 453, and −10° G was found to immobilize them. The observed difference seems to be mainly due to the cryoprotective properties of serum.