Morphological study of the rare nematode Paradollfusnema amphisbaenia (Baker, 1981) (Cosmocercidae) and its first report in an amphibian host

The present study aimed to perform a morphological analysis of Paradollfusnema amphisbaenia, a parasite of Leptodactylus podicipinus (Leptodactylidae) in the Caatinga of Pernambuco, Brazil, using light and scanning electron microscopy (SEM), and to report for the first time the genus infecting an amphibian. Paradollfusnema species differs from other Cosmocercidae by having interlabia in the cephalic end. Main morphological characters that distinguish species in this genus are the number and distribution of caudal papillae, size of spicules and gubernaculum, and size of eggs. Nematodes analysed had lateral alae in both males and females, arrangement of caudal papillae: 14 pairs, distributed in 8 pairs + 1 unpaired precloacal, 1 adclocal, and 5 postcloacal, non-alate spicules with 100-170 µm long, and eggs 87-125 long x 68-110 µm wide. SEM analyses revealed the arrangement of labial papillae with greater accuracy, diverging from what was described in a previous study. This also enabled a more detailed analysis of the distribution of the caudal papillae and the presence of interlabia. There are no records of this genus parasitizing amphibians worldwide. This is the first morphological study of P. amphisbaenia using SEM, and the first report of this species infecting an anuran host.