Redescription and molecular characterisation of nematode <i>Aprocta turgida</i> Stossich, 1902 (Chromadorea: Aproctoidea: Aproctidae), parasite of larid birds

Adult females and males of aproctid nematode <i>Aprocta turgida</i> were collected from the nasal cavity of <i>Larus cachinnans</i> Pallas, 1811 obtained in Dagestan, Russia. Parasites were examined using light and scanning electron microscopy, and genetically characterised based on partial sequences of <i>18S rRNA</i> and <i>cox1</i> genes. This study of <i>A. turgida</i> enabled us to detect phasmids in females and describe the absence of the anus in specimens of this sex, and confirmed the presence of one pair of caudal papillae in males. In the phylogenetic analysis based on the <i>18S rRNA</i> gene dataset, <i>A. turgida</i> formed a strongly supported clade with other representatives of <i>Aprocta</i>. In turn, the <i>Aprocta</i> spp. clade was closer to desmidocercid and diplotrienid nematodes than to another aproctid, <i>Lissonema sicki</i> (Strachan, 1957). Thus, the Aproctidae appeared to be a polyphyletic assemblage. The analysis based on the <i>cox1</i> gene dataset supported <i>Aprocta</i> as a sister to the clade of desmidocercids and diplotrienids.