LAUSR

Abstract Morphological characteristics were studied in adult and embryonic Amidostomum anseris (Zeder, 1800) obtained from domestic goose Anser anser domesticus Linnaeus, 1758. The studied characters included species-specific morphometric indices of male and female specimens and differential characters of sex-related dimorphism in that species. Stages and periods of embryonic development, and viability of the nematodes were studied at laboratory conditions. Size dimorphism in A. anseris was considerable, females were significantly larger (by 10.09–27.98 %) than males by 11 parameters. Additional metric characters were proposed to enhance effectiveness of differentiation of female and male A. anseris specimens. Under laboratory conditions, embryonic development of A. anseris occurs in four stages: blastomere cleavage; larval formation; formation of non-infective larvae I and II; formation of infective larva III which hatches from the egg. Infective larvae develop at 23 °С in six days, and their viability was up to 78.33 ± 2.08 %.