Further studies on the morphology of Baylisascaris transfuga (Rudolphi, 1819) (Nematoda: Ascaridomorpha: Ascarididae) from the polar bear Ursus maritimus Phipps (Carnivora: Ursidae).

Baylisascaris transfuga (Rudolphi, 1819) is a common parasitic nematode in the digestive tract of various species of bears worldwide, with great veterinary significance. However, our present knowledge on the morphology of B. transfuga remains insufficient. In the present study, the detailed morphology of B. transfuga was studied using light and scanning electron microscopy (SEM), based on specimens collected from the polar bear Ursus maritimus Phipps (Carnivora: Ursidae) in the Shijiazhuang Zoo, China. The results revealed some morphological and morphometric variation between the present specimens and some of those from previous studies, including oesophageal length of female, number and morphology of postcloacal papillae and morphology of tail of males. Present SEM observations clearly showed the detailed morphology of lips, cervical alae, cloacal ornamentation, precloacal medioventral papilla, phasmids and tail tip. These supplementary morphological and morphometric data enable us to identify this ascaridid nematode more accurately.