Zoologica zyxwvutsrqpo Scripta, Vol. 22, No. 2, pp. 127-152, 1993 Printed in Great Britain 0300-3256193 $6.00 zy + .OO Pergamon Press Ltd zy 0 1993 The Norwegian Academy of Science and Letters zy A revision of the zyxw Macrobiotus hufelandi group (Tardigrada, Macrobiotidae), with some observations on the taxonomic characters of eutardigrades ROBERTO BERTOLANI and LORENA REBECCHI Accepted 16 zyxwvutsrqpon July 1992 Bertolani, R. & Rebecchi, L. 1993. A revision of the Macrobiotus hufelandi group (Tardigrada, Macrobiotidae), with some observations on the taxonomic characters of eutardigrades.-Zool. Scr. 22: 127-152. This study considers specimens of Macrobiotus hufelandi C. A. S. Schultze, 1834 collected from Italy and Germany, including the type locality. In addition to a qualitative analysis of the animals and eggs, statisticswere performed on the measurcments of the sclerified parts of the animals. The data illustrate low intra-species variability in the morphology of both the animals and the eggs. Differences in egg shell morphology, previously attributed to the variability of M. hufelandi, were found to fall into distinct types, rclated to different animal morphotypes. The data also indicatc that M. hufelandi contains several new species: M. macrocalix sp.n., M. sandrae sp.n. and M. terminalis sp.n.; M. hufelandi is redescribed, and a neotype is assigned. Roberto Bertoiani & Lorena Rebecchi, Dipartimento di Biologia Animale deN’Universita di Modena, Via Universita 4, 41100 Modena, Italy. Introduction The first observations on the Tardigrada were made two centuries ago, but 60 years were to pass before the first species was described in the literature. C. A. S. Schultze (1834~) erected the species Mucrobiotus Hufelundii for specimens collected near Freiburg in Germany. This species is still valid today (as Mucrobiotus hufelundi Schultze, 1834 according to the International Code of Zoological Nomenclature), although inadequately de- scribed in Schultze (1834u, b). Only the presence of eye spots and symmetricalclaws were specified, and eggs with ornamented shell were included in the illustrations. Doyere (1840) described the eggs of M. hufelandi in greater detail; he specified that the eggs were spherical structures bearing tubercles with enlarged ends that pro- truded from the shells and that the related animals were remarkably similar to the type specimens. Marcus (1929, 1936) emphasized the variability of nu- merous morphological characters in his species descrip- tion and remarked on the rather large size of the animals; brownish opaque pigment of the older specimens, vari- able presence of eye spots, smooth cuticle occasionally containing small birefractive granules, buccal aperture lined by lamellae, moderately long buccal tube, curved stylets, pharynx with apophyses, two macroplacoids and a microplacoid (in the adult forms, the first macroplacoid longer than the second, usually notched or strongly con- stricted, sometimes straight); strong claws with secondary branches inserted halfway along the main branch (with accessory points); and slightly serrated lunulae in the adults. The eggs were reported to be spherical (72-90pm diameter, excluding the processes) or rarely oval, with processes in the form of inverted goblets, 3-10 pm tall, with flared ends forming a distal dish, generally with a smooth border but sometimes crown-like. A ring of about 13 round to oval ‘pearls’ generally encircled the base of the processes, but were sometimes absent. CuCnot (1932) believed that the eye spots and ‘dots’on the cuticle were a constant feature, and reported the presence of smaller ‘dots’ on the eggs lying between the egg shell processes, as well as a ‘dotted’ ring at the base of the processes. Again the reference confirms a large intra- species variability, emphasizing the differences in egg morphology and hypothesizing the existence of at least two races. Several years later, Ramazzotti (1962) confirmed the previous descriptions of M. hufelundi, though stressing the presence of remarkable intra-species variability. The suspicion that more than one species had been included under the title of ‘M. hufelundi’ was emphasized by scanning electron microscopy (SEM) studies on the egg shell (Grigarick et al. 1973; Toftner et ul. 1975). These papers precisely defined the structural details. However, the lack of parallel studies on the animals prevented the formulation of new proposals for the identification and classification of these potentially new species. Karyological and morphological investigations (Berto- lani 1973, 1975, 1982; Bertolani & h4ambrini 1977) demonstrated the presence of different diploid and poly- ploid cytotypes and different types of eggs for different animals attributed to M. hufelundi. Bertolani (1982) con- cluded that a given egg shell morphology corresponded to more than one cytotype, and he confirmed the existence of three distinct morphospecies, all attributable to ‘M. hufelundi’. However, these were not named, pending a more detailed study. Recently, descriptions have appeared of some new 127 Zoologica Scripta 22