21. The development of Diclybothrium Leuckart 



The genus Diclybothrium is characterized by the presence of 

 the attaching disc with 3 pairs of clamps or suckers, in each of which lies 

 one large chitinous hook. On the posterior end of the disc there is a 



strongly developed, narrowed part 

 which bears 3 pairs of large hooks 

 (of which two are almost the same 

 size as the hooks of the attaching 

 clamps), one pair of very small 

 hooks and one rudimentary pair of 

 suckers. The typical representative 

 of the genus, D. armatum Leuckart, 

 (Fig. 51), parasitizes the sturgeon 

 family. The study of the develop- 

 ment of this species was conducted 

 by us together with A. V. Gussew 

 (Bychowsky and Gussew, 1950). 

 We cite a section of this work 

 relative to the development of D. 

 armatum below. 

 Fig. 219. Sphyranura oligorchis. 



stages of development of middle 

 hooks. A- -On 26th day of develop- 

 ment; B--Of the larva which has 

 just emerged from the egg; C-- 

 Of an adult worm. Magnified 130 

 times. (According to Alvey, 1936). 



"Attempts to obtain free- 

 swimming larvae of D. armatum 

 were made by us in 1931-1932 but 

 were unsuccessful in the fresh-water 

 region (Delta of the Volga) as in the 

 sea (Island of Sara, Caspian Sea). 

 Only in 1947, during our studies at 

 the VNIRO fish production station in Saratov did we succeed in obtaining 

 two free -swimming larvae from a considerable number of eggs which p. 193 



were isolated for development and which, in the main,perished in the early 

 stages of development. A rather large number of the developed larvae 

 could not emerge from the eggs because a rich vegito-bacterial fauna 

 developed on the surface of the latter which prevented the larvae from 

 opening the operculum of the egg. The embryology of the larvae took 

 place in large salt-shakers (stender dishes or embryo dishes? nobis) which 

 were located in a shady place. Temper- 

 atures fluctuated strongly during the entire period of development and 

 within a 24-hour period. The tennperature during the entire period of the 

 development of the larvae fluctuated from +20, to +30. 0° centigrade and 

 within the limits of 24 hours the difference was up to 6°. In spite of these 

 clearly unnatural temperature conditions, development took place rather 

 quickly, in comparison with that of other large monogenetic trematodes. 

 On the 6th day lively larvae were already formed in the eggs, and on the 

 8th day they emerged. Taking into consideration the abnormal conditions 

 of the experiment one must suppose that in nature the development of D. 



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