The paradoxical spain [1] ( lat. Diplozoon paradoxum ) is a species of flatworms from the family Diplozoidae of the monogena class (Monogenea), the only one of the genus Diplozoon [2] . Parasitizes on the gills of carp fish . The size is 6-10 mm. Hermaphrodite . Known for the fact that when mating, two individuals forever fuse together, forming a characteristic cross-shaped figure. [3]
| Paradoxical |
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| Scientific classification |
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| No rank : | Bilateral symmetrical |
| Subclass : | Polyopisthocotylea |
| Gender: | Diplozoon von Nordmann, 1832 |
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| International scientific name |
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Diplozoon paradoxum von Nordmann , 1832 |
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Egg laying occurs in the spring. After 10 days, larvae hatch from them - oncomiracidia , which are covered with cilia , and also have two suction cups and two hooks between them. They settle on the gills of young fish of the cyprinid family, after which they lose cilia and turn into so-called juvenile worms. They form a dorsal tubercle and an abdominal sucker. With the help of these organs, two juvenile worms attach to each other when they meet, after which they grow together. Worms feed on the host’s blood and grow. Then the gonads develop, while the genitals of each partner grow into the body of the other, and cross- fertilization occurs. The next spring, the worms lay their eggs, and the cycle repeats. [3]
Until 1959, it was believed that the Diplozoon paradoxum was the only representative of the genus in Europe. In 1959, B. E. Bykhovsky and L. F. Nagibina showed that the species D. paradoxum is a prefabricated species, and three new species were isolated from it; over the next 15 years, about 50 new species of this genus were described. However, some authors ignored all these results, which led to confusion [4] .
An inspection of the genus was carried out by I.A. Khotenovsky in 1985. All described species were grouped into 5 genera: Diplozoon Nordmann, 1832, Paradiplozoon Achmerov, 1974, Inustiatus Khotenovsky, 1978, Sindiplozoon Khotenovsky, 1981, and Eudiplozoon Khotenovsky, 1985. At the same time, two species remained in the genus Diplozoon : D. paradoxum and D. scardini (Khotenovsky, 1985). It should be noted that some authors did not recognize this revision and continued to attribute all these species to the genus Diplozoon . [five]
In 2001, using DNA analysis , it was shown that D. scardinii is identical with the Paradiplozoon homoion , thus the only representative of D. paradoxum remained in the genus Diplozoon [5] [6] .