Scanning electron microscopy observations of the hedgehog stomach worm, Physaloptera clausa (Spirurida: Physalopteridae).

Background: Physaloptera clausa (Spirurida: Physalopteridae) nematodes parasitize the stomach of the European hedgehog (Erinaceus europaeus) and cause weight loss, anorexia and gastric lesions. The present study provides the first morphological description of adult P. clausa from the stomachs of infected hedgehogs, using scanning electron microscopy (SEM). Methods. From June to October 2011, 10 P. clausa from European hedgehogs were fixed, dried, coated and subjected to SEM examination. Results: Males and females (22-30 mm and 28-47 mm, respectively) were stout, with the cuticle reflecting over the lips to form a large cephalic collarette and showing fine transverse striations in both sexes. The mouth was characterized by two large, simple triangular lateral pseudolabia, each armed with external and internal teeth. Inside the buccal cavity, a circle of internal small teeth can be observed. Around the mouth, four sub-median cephalic papillae and two large amphids were also observed. The anterior end of both male and female bore an excretory pore on the ventral side and a pair of lateral ciliated cervical papillae. In the female worm, the vulva was located in the middle and the eggs were characterized by smooth surfaces. The posterior end of the female worm was stumpy with two large phasmids in proximity to its extremity. The posterior end of the male had large lateral alae, joined together anteriorly across the ventral surface, with subequal and dissimilar spicules, as well as four pairs of stalked pre-cloacal papillae, three pairs of post-cloacal papillae, and two phasmids. Three sessile papillae occured anteriorly and four posteriorly to the cloaca. Conclusions: The present SEM study provides the first in-depth morphological characterization of adult P. clausa, and highlights similarities and differences with P. bispiculata P. herthameyerae, Heliconema longissimum and Turgida turgida.