Philodina scabra Milne, 1916

Song, Min Ok & Lee, Chang-Ho, 2017, A new and five rare bdelloids from Korea, Zootaxa 4242 (3), pp. 529-547 : 538-540

Philodina scabra Milne, 1916

Figure 4

Material. One specimen found in leaf litter, mosses and soil at Mongsanpo, Nam-myun, Taean-gun, Chungcheongnam-do.

This small and rare species has never been found again after the original description from South Africa by Milne (1916) until the present study. Milne (1916) was not sure about the number of toes and mentioned that it might need to be transferred to Macrotrachela if the number of its toes was confirmed to be three instead of four. The general morphology of this species is much more like that of a Macrotrachela species than a Philodina one mainly because of the very short foot. The Korean specimen clearly has four toes, which ensures that it is a Philodina species.

This species is easily recognized by two pairs of spurs, highly granulated trunk covered with debris, short foot, and adjoining trochal discs. The most prominent diagnostic characteristic of this species is two pairs of spurs on the third foot pseudosegment. Of interest, there is a discrepancy in the arrangement of these spur pairs between the original description and the Korean specimen. Milne (1916) described that the upper pair of spurs were broad and tapering to sharp point, while the other pair, located just below the upper pair, were about the same length and much thinner than the upper ones. In the Korean specimen, the position of these spur pairs are reversed, that is, the broad spur pair is underneath the thinner pair ( Fig. 4 d). It might be possible that Milne mistook the positions of the spur pairs during his observations. Detailed observation using scanning electron microscopy might be required when more Korean specimens get available. The total length of the species as reported by Milne (1913) was 141 µm, while that of the Korean specimen is 186 µm.

Measurements. Total length in creeping 186 µm. Rostrum width 10.7 µm. Corona width 24 µm. Collar width 27 µm. Greatest trunk width in creeping 37 µm. Spur length 8 µm.

Figures

FIGURE 4. Philodina scabra Milne, 1916. (a) creeping, dorsal view; (b) feeding head, dorsal view; (c) foot, spurs and toes, ventral view; (d) light microscopy photograph of spurs and toes, ventral view (scale bars: a = 50 µm; b = 20 µm; c = 10 µm).