REVISION DE LOS GENEROS DIPLODISCUS DIESING, 1836 y MEGALODISCUS CHANDLER, 1923 (TREMATODA: PARAMPHISTOMOIDEA). II.

Resumen

The present paper is a systematic revision of the genera Diplodiscus Diesing, 1936 and Megalodiscus Chandler, 1923. 
In the first part, published in No. I of this some volume, the morphological terminology in which the different authors were not in accord, was unified. The American genus Megalodiscus Chandler was separated from the European genus Diplodiscus Diesing, because the first has always two testicles, while the latter has only one. This character could be proven, by the observation of very young forms taken from the initial portions of the digestive tract of frogs. By staining such specimens that yet had the aspect of metacercariae because of their two ocular spots, the presence of the masses corresponding to the two testicles could be clearly seen.
The species Diplodiscus subclavatus (Goeze, 1782); D. megalochrus Johnston, 1912; D. doyeri Ortlepp, 1926; D. amphichrus Tubangui, 1933; D. japonicus (Yamaguti, 1936) y D. mehrai Pande, 1937, are redescribed.
Diplodiscus microchrus Johnston, 1912 is reduced to a synonym of D. megalochrus Johnston, because the two most important differential characters given by the author (size of the body and diameler of the acetabulum) should not be taken into consideration as specific characters, because the variation in size depends on the age of the specimen and its conditions of life, while the diameter of the acetabulum may change with the more or less pronounced state of contraction of its walls.

Diplodiscus sinicus Li, 1937 is given as a synonym of D. amphichrus Tubangui, 1933, because in the comparative study of these species there was a perfect accord in the majority of their fundamental characters; such as position of the sexual pore, diameter of the acetabulum, location of the vitellaria, size and position of the testicle and the ovary, and the small development of the oral diverticles.

In relation to the species Diplodiscus japonicus Yamaguti 1936, we accept, with Li, 1937 and Pande, 1937, to consider it as a species and not as a variety of the species of Tubangui 1933.
Diplodiscus unguiculatum Diesing, 1936, is not included in this paper, because in the original description the sexual pore is given as located at the posterior and in the middle of the acetabulum, and the species considered as viviparous, characters which have never been observad in any of the species of these two genera.
D. cornu (Diesing, 1840) Daday, 1904, is also left out because the original description does not mention the existence of oral diverticles, that of the acetabulor papilla, nor that of the cirrus pouch as in the other species, all these being characters of the genus Diplodiscus.
The second part deals with the revision of the genus Megalodiscus Chandler, 1923; including the species M. temperatus (Stafford, 1905); M. americanus Chandler, 1923; M. intermedius (Hunter, 1930); M. microphagus Ingles, 1936; and M. rankini n. sp. Travassos, in its revision of the superfamily Paramphistomoidea, 1934, considers Megalodiscus temperatus, studied by Sokoloff & Caballero in 1933 (Anales del Instituto de Biología, vol. IV, pág. 15), as a different species under the name of M. montezumae. A later study of the preparations used by Sokoloff & Caballero in the determination of M. temperalus. revealed that there were not differences important enough to account for the making of a new species. Therefore in this paper, in accord with Manter, Megalodiscus montezumae is given as a synonym of Megalodiscus temperatus.
Rankin in its oecologycal revision of the parasites of the salamanders of North Carolina (1937), makes reference to M. temperatus and M. intermedius. A revision of the specimens of M. temperatus, kindly loaned to us by Dr. Rankin, showed that none of the specific characters of the species were present (length of the caeca and the oral diverticles, and location of the sexual pore); we therefore, have established a new one: Megalodiscus rankini.