Species-specific morphological characteristics of adult and embryonic Capillariа obsignata roundworms (Nematoda, Capillariidae)

Abstract

The abundance of Capillaria obsignata Madsen, 1945, the causative agent of chicken capillariasis, was studied in the central region of Ukraine. Differential morphometric characters are determined for adult males and females of C. obsignata. The species-specific variability of its morphological parameters is characterized. New data is received on the meristic characters of C. obsignata eggs extracted from different substrates. The stages of embryonic development are determined in laboratory cultures of these nematodes, taking into account their meristic and morphological changes. Capillaria obsignata parasites are very common at the poultry farms of Poltava and Kyiv regions of Ukraine. Their abundance index is 3.4, and the intensity of infection varies from 3 to 317 specimens. Differential morphometric species-specific characters of adult C. obsignata males are the shape and size of the pseudobursa, spicule, spicule sheath. Adult females of the species can be identified by the shape and size of the vulva, the distance from the esophagus end to the vulva, and the length of the vagina. The meristic characters of nematode eggs, though typical for the species, may change depending on the sampled substrate. The parasite’s embryonic development involves five morphologically and meristically different stages. The invasive larvae of this species developed in the eggs before the 12th day of culturing in laboratory conditions at 25 °С. The invasive larvae’s viability was 90.3 ± 1.5%.

Differential species characters of Baruscapillaria anseris and B. obsignata nematodes obtained from the domestic goose

“…We also note that the size of cuticular lip in the vulva area cannot be used as a differential character because of its variability. Our data is in line with findings of other authors (Yevstafyeva et al, 2017). The majority of studies indicate the important value of metric parameters as additional identification characters of various capillariid species (Kajerová & Baruš, 2005;Dar et al, 2013).…”

“…In long-term studies, the following morphological characters have been suggested for species identification of Capillariidae: the structure of male tail end, the ornamentation of spicule sheath, the numbers and shape of stichocytes, the shape and size of eggs, egg surface specifics, and the vulval area structure, location and biological features (Zd'árská & Nebesárová, 2000;Frantová, 2001;Traversa et al, 2011). The metric characteristics of helminths also matter in enhancing the effectiveness of their species identification (Kajerová & Baruš, 2005;D'ávila et al, 2012;Yevstafyeva et al, 2017).…”