New taxonomic position of several Macrobiotus species (Eutardigrada: Macrobiotidae)

Abstract

The main character distinguishing Minibiotus from Macrobiotus is the presence of peribuccal papulae instead of lamellae. However, most Minibiotus species also share a set of characters of the bucco-pharyngeal apparatus. This set is defined by ten morphological features (the first seven common to all species, the last three to most of them): antero-ventral mouth (1), teeth in oral cavity absent or strongly reduced (2), a rigid and narrow buccal tube (3), buccal tube wall thickened below the point of insertion of stylet supports (4), stylet supports inserted at considerable distance from the posterior end of the buccal tube (5), short ventral lamina (6), short macroplacoid row length (7), a double curvature of the buccal tube (8), first macroplacoid situated very close to the pharyngeal apophysis (9) and three almost rounded macroplacoids (10). We examined the original descriptions and/or the type material of several species belonging to the genus Macrobiotus that seemed to present this set of characters. It was concluded that several species should be transferred from Macrobiotus to Minibiotus. The following new combinations are proposed: Minibiotus subintermedius (Ramazzotti, 1962) comb. n., Minibiotus pustulatus (Ramazzotti, 1959) comb. n., Minibiotus julietae (de Barros, 1942) comb. n., Minibiotus marcusi (de Barros, 1942) comb. n., Minibiotus granatai (Pardi, 1941) comb. n., Minibiotus allani (Murray, 1913) comb. n., Minibiotus crassidens (Murray, 1907) comb. n. and Minibiotus acontistus (de Barros, 1942) comb. n.. As a result of these new combinations, the genera Minibiotus and Macrobiotus appear to be more homogeneous, but their monophyly has not yet been demonstrated. Further data are necessary to better analyze the systematic position of Macrobiotus lazzaroi Maucci, 1986, Macrobiotus spertii Ramazzotti, 1957 and Macrobiotus striatus Mihelčič, 1949.