Characterization of a coelomic gregarine parasite from Thitarodes pui (Lepidoptera: Hepialidae) in the Tibetan Plateau

Thitarodes pui, one of the host species of entomopathogenic fungus Ophiocordyceps sinensis, has great economic importance in the Tibetan Plateau. We report here, for the first time, a gregarine parasite found in the coelom of 7th instar and adults of T. pui. Gregarine gamonts (ovoid, ～15×8μm) underwent syzygy to produce reproductive gametocysts in T. pui larval hemolymph. All infected T. pui carried 2-17 mature gametocysts filled with numerous oocysts (lemon-shaped, 17.17±0.73×6.49±0.4μm). Transmission electron microscopy showed that these oocysts contained vacuoles of various sizes and amylopectin granules in the cytoplasm; scanning electron microscopy revealed a number of small bumps all over the surface of these oocysts. Small subunit ribosomal DNA sequence analysis showed a close relationship between the gregarine and the species of Ascogregarina (Eugregarinorida: Lecudinidae). Internal transcribed spacers and 5.8S ribosomal DNA from this gregarine exhibited 76% highest sequence identity with that from Ascogregarina culicis Ross.