Philodina childi Milne, 1916

Song, Min Ok & Lee, Chang-Ho, 2017, A new and five rare bdelloids from Korea, Zootaxa 4242 (3), pp. 529-547 : 537-538

Philodina childi Milne, 1916

Figure 3

Material. One specimen found in mosses, lichens and soil in Jang-neung, Yeongwol-gun, Gangwon-do.

This species is easily diagnosed by a pair of obtuse dorsal projection on the first foot pseudosegment, which are similar to those on the identical position in Macrotrachela quadricornifera Milne 1886 . These two dorsal projections on foot distinguish this Philodina species from any other congeners. It was rediscovered in Korea almost 100 years after the original description from South Africa by Milne (1916). The general morphology of the Korean specimen agrees well with that of the original description of the species, except some parts in feeding head. Firstly, Milne (1916) did not describe the upper lip in detail and just mentioned it as “rather complicated”. Even the illustration of the feeding head in Milne (1916) is not clear as well; however, the upper lip in the original description seems similar to that of the Korean specimen. In the Korean specimen, upper lip is arched and bilobed medially. Each lobe is rather triangular and with a depression between them. The median depression is slightly narrower than the width of each lobe in the Korean specimen, while it is much wider in the original description. Secondly, the original figure ( Milne, 1916, Pl. 3, fig. 4a) does not show disc retractor clearly, either. Milne (1916) mentioned the disc retractor as “a thin ridge or membrane with a V-shaped gap seen ventrally between the pedicels”. The disc retractor of the Korean specimen appears to be similar to that in the original description except it has a small triangular projection medially. The Korean specimen was much smaller than what was reported by Milne (1916). The total length in feeding of the Korean specimen was 187 µm, while the total length in creeping in the original description was about 635 µm. Milne (1916) did not mention the total length of P. childi in feeding.

Since the total length in feeding is smaller than that in creeping, the latter can be estimated to be a bit longer than 200 µm in the Korean specimen, which is about a third of the size in the original description.

Measurements. Corona width 61 µm. Collar width 48 µm. Greatest trunk width in feeding 67 µm. Spur length 8.6 µm.

Figures

FIGURE 3. Philodina childi Milne, 1916. (a) feeding, dorsal view; (b) foot, spurs and toes, lateral view; (c) foot, spurs and toes, ventral view (scale bars: a = 50 µm; b = 20 µm; c = 10 µm).