A revision of the genus Minibiotus (Tardigrada: Macrobiotidae) with descriptions of eleven new species from Australia

Abstract

The genus Minibiotus is redefined and the type species, Minibiotus intermedius (Plate, 1889) is redescribed. Eleven new species of Minibiotus are diagnosed and described, and three are transferred from the genus Macrobiotus using a range of qualitative and quantitative characters of adults and eggs. Keys are provided to the adults of the 22 reported species in the genus and to the eggs of the 20 species for which eggs have been described. Characters useful in discriminating species with very similar morphology are noted. The difficulties inherent in taxonomic studies of small animals such as many of those in the genus Minibiotus are discussed as are the problems of recognition of species in groups where both the adult form and sometimes also the egg are very similar. The examination and description of the eggs is important in tardigrade taxonomy. CLAXTON, SANDRA K., 1998. A revision of the genus Minibiotus (Tardigrada: Macrobiotidae) with descriptions of eleven new species from Australia. Records of the Australian Museum 50(2): 125-160. Minibiotus Schuster et al., 1980 is a genus of terrestrial tardigrades found commonly in mosses and lichens. The type species Minibiotus intermedius (Plate, 1889) remained the only species in the genus until M. maculartus was described by Pilato & Claxton in 1988. The adults of this species closely resembled M. intermedius but the eggs were quite dissimilar, having processes that lacked an enclosing membrane-a character suggested as definitive for the genus by its authors. Further species have since been described. Minibiotus Jallax was described by Pilato et al. in 1989. This species had few adult characters similar to those of M. intermedius apart from the presence around the mouth of papulae (Fig. la) rather than the lamellae present in the closely related genus Macrobiotus. Miller et aI., (1994) transferred Macrobiotus weinerorum Dastych, 1984 to the genus Minibiotus while Dastych & Drummond (1996) attributed Macrobiotus stuckenbergi Dastych et al., 1990 to the genus Minibiotus. Binda & Pilato (1992) described two new species and transferred Macrobiotus Jurcatus to the genus Minibiotus. They suggested that the Minibiotus bucco-pharyngeal apparatus has a characteristic appearance which includes double curvature of the buccal tube, stylet supports inserted a considerable distance from the pharyngeal bulb and first macroplacoid situated very close to the apophysis. The genus Minibiotus, however, has not been uniformly accepted (Ramazzotti & Maucci, 1983) perhaps because of its unsatisfactory definition (Pilato, 1982). One of the aims of this paper is to provide a more precise definition of the genus.