Abstract:

Objective To investigate the infection of Sinopotamon pinghense with Euparagonimus metacercariae in Liudou Mountain Natural Reserve in Nanjing County and the morphology of S. pinghense. Methods Samples of S. pinghense crabs were collected from the streams outside (X1) and inside(X2) the Liudou Mountain Natural Reserve from November 2016 to May 2017, the place of collection and environmental factors of the habitats were recorded by GPS. The E. cenocopiosus metacercariae in the heart of the crabs were morphologically observed with the direct compression method. The metacercariae infection rates were compared between crabs from X1 and X2 streams, and among large, medium-sized, and small crabs. Data were analyzed with SPSS 22.0 software. The S. pinghense crabs were morphologically observed and photos were taken. Results The infection rates of E. cenocopiosus in S. pinghense from X1 and X2 streams were 17.7%（3/16) and 86.3%（63/73）, respectively, with a significant difference（χ² = 29.817, P < 0.05). The average intensity of infection was 1.7 metacercariae per crab in X1 and 11.6 in X2, with the latter being 6.9 folds of the former. A total of 742 metacercariae were collected from X2, with the maximum number of 79 metacercariae in one crab. The intensity of infection in large crabs was 2.6 and 5.8 times of those in medium-sized and small crabs, respectively. The infection rates in large, medium-sized, and small crabs in X2 were 100% (31/31), 82.6% (19/23) and 68.4% (13/19), respectively (χ² = 31.620, P < 0.05). The first male pleopod of S. pinghense reached beyond sutures of chest 5/6. Its irregularly-shaped terminal segment pointed towards the outer front direction, had a round base, and became narrower rostrally. The terminal segment was divided into 2 lobes by a longitudinal fissure, which was clearly seen from the backside. The inner margin of the subterminal segment displayed as a square angle while the outer edge was oblique. Conclusion The Liudou Mountain Natural Reserve in Nanjing County is a new natural spot with E. cenocopiosus infection. The new morphological findings of S. pinghense provides basis for identifying similar species of Sinopotamidae.

Key words: Sinopotamon Pinghense, Morphology, Ecotope, Euparagonimus cenocopiosus, Metacercariae, infection