Two new species of Tetranchyroderma (Gastrotricha, Macrodasyida) from a sandy beach in southeastern Australia

Two new species of Tetranchyroderma are described from a sandy beach in southeastern Australia. Both species belong to the subgroup of the genus in which the dorsal surface of the body is covered with pentancres and in which head sensorial organs (tentacles and/or pestle organs) are absent. Tetranchyroderma pentaspersus sp. nov. is small, 178–244μm long, and distinguished by possessing exceptionally large pentancres, c. 30 rows, with the central tine c. 15μm long on the trunk, though shorter on the head; lateral tines c. 60% as long. The adhesive apparatus consists of four pairs of anterior adhesive tubules (TbA), nine pairs of ventro-lateral tubules (TbL), and eight posterior tubules (TbP), with two of the latter at the end of each caudal pedicle and four very small in between the caudal pedicles; dorsal and ventral tubules and “cirrata” are absent. Tetranchyroderma australiense sp. nov. is larger, 330–390μm long, possesses c. 70 rows of smaller pentancres, with all five tines of equal length. The adhesive apparatus consists of four pairs of TbA, eleven pairs of TbL, one pair of dorsal adhesive tubules (TbD), and four TbP, the latter equally distributed at the end of two caudal pedicles; ventral tubules and cirrata are absent. Possible synonymy between the new species and Tetranchyroderma sp. 7 of Valbonesi & Luporini (1988) from Somalia is discussed.