Philodina undulata, Song & Lee, 2024

Song, Min Ok & Lee, Chang-Ho, 2024, Descriptions of three new species of Philodinida (Rotifera, Bdelloidea) from Korea, Zootaxa 5493 (1), pp. 36-54 : 44-46

Philodina undulata n. sp.

Figures 5 and 6

urn:lsid:zoobank.org:act:A148F5FB-5587-4328-B7E9-5D03EA3240FA

Holotype and paratypes. On permanent slides, deposited in the collection of the Nakdonggang National Institute of Biological Resources, Sangju-si, Gyeongsangbuk-do, Korea (holotype: NNIBRIV59170; two paratypes: NNIBRIV59171 and NNIBRIV59172) .

Type locality. Mokgye-ri , Wangsan-myeon , Gangneung-si, Gangwon-do, Korea. GPS coordinates based on WGS84 datum 37°38'40.7"N / 128°52'12.8"E .

Material. Five specimens sorted out from mosses, collected by Min Ok Song and Chang-Ho Lee on 23 May, 2020.

Differential diagnosis. This new species appears to be similar to Habrotrocha lata lens Donner, 1965 under low magnification (× 100–200) because they share some characteristics such as the plump trunk with wavy lateral margins, rump much narrower than trunk, long rostrum, rather cylindrical neck in creeping and long spurs. However, these two species have the different numbers of toes, four in the new species and three in H. lata lens , which is one of the most important diagnostic characteristics that assigns each species to the different genus, Philodina and Habrotrocha , respectively. In addition, there are significant differences in the morphology of the feeding head between these two species.

This new species is easily distinguished from its congeners by the first trunk pseudosegment expanded anteriorly in feeding as well as the plump trunk that has wavy lateral margins and abruptly tapers to rump in feeding. Philodina megalotrocha Ehrenberg, 1832 also has very round trunk and narrow rump in feeding. However, P. megalotrocha has two eyespots and short feeding head, which are otherwise in this new species. Philodina nitida nitida Milne, 1916 is the most similar congener of this new species in the general morphology as well as the partial CO1 sequence (Supplementary Figure 3 ). However, this new species can be distinguished from P. n. nitida by the following characteristics: (1) P. undulata n. sp. doesn’t have eyespots, while P. n. nitida has two small eyespots, (2) the ratio of corona width to cingulum width is about 1.05: 1–1.1: 1 in P. undulata n. sp., while it is 1.23: 1–1.26: 1 in P. n. nitida , (3) teeth is 3/ 3 in P. undulata n. sp., while it is 3+1/1+ 3 in P. n. nitida , (4) interspace between spurs is about twice as wide as spur base width in P. undulata n. sp., while it is slightly wider than spur base width in P. n. nitida , (5) the ratio of head width to rostrum width is 1.7: 1–2.0: 1 in P. undulata n. sp., while it is about 2.3: 1 in P. n. nitida , and (6) the lateral margins of trunk of P. n. nitida are not as wavy as those of P. undulata n. sp. ( Donner 1965; Milne 1916; Song & Lee 2023).

Description. No eyespots. Trunk lightly granulated. Rostrum fingertip-shaped and slightly longer than its width; rostrum narrower than head width in creeping; the ratio of head width to rostrum width in creeping 1.7: 1–2.0: 1. Rostral lamella bilobed and with narrow interspace; each lobe round and small; interspace narrower than each lobe width; with radial cilia. Corona very slightly wider than cingulum; the ratio of corona width to cingulum width 1.05: 1–1.1: 1. Trochal discs slightly inclined inwardly; base of sensory hair hemispherical and rather big. Pedicel short; big hump on inner half of pedicel dorsally. Sulcus much narrower than pedicel width; the ratio of pedicel width to sulcus width about 1.5: 1. Disc retractor V-shaped and with round base ( Fig. 6d ). Upper lip arched, rather truncated medially and without median notch; anterior margin rather flat or slightly concave depending on the degree of contraction and relaxation of feeding head; anterolateral margins round; higher or slightly lower than disc retractor base depending on the degree of contraction and relaxation of feeding head; much lower than trochal discs. Each end of cingulum rather convex. Cingulum pad very slightly narrower than cingulum; lateral margins round medially. Antenna long and with two pseudosegments; slightly shorter than height of pseudosegment bearing antenna in creeping. Pharyngeal tube shorter than trophi length both in creeping and in feeding. Teeth 3/3. First trunk pseudosegment expanded anteriorly and abruptly tapering to posterior part in feeding; first trunk pseudosegment flat bowl-shaped in frontal view anteriorly; trunk rather cylindrical in creeping and spindle-shaped in feeding; lateral margins wavy; granulated longitudinal ridges wavy except middle ones; trunk abruptly tapering to rump posteriorly. Rump much narrower than greatest trunk width especially in feeding; slightly constricted anteriorly and then gradually tapering to foot in creeping; plump medially in feeding. Foot narrower than rump and tapering gradually to pseudosegment bearing toes; with four pseudosegments; foot short and about 1/6 of total body length in creeping. Four toes thin. Spurs finger-shaped, thin and long; lateral margins of spurs gradually tapering to blunt ends; interspace width much wider than spur base width; the ratio of interspace width to spur base width about 2: 1.

Measurements. Total length in creeping 174–209 μm. Total length in feeding 187–200 μm. Rostrum length 15–16 μm. Rostrum width 14–15 μm. Corona width 42–43 μm. Cingulum width 39–41 μm. Cingulum pad width 39–40 μm. Greatest head width in creeping 24–31 μm. Trophi length 13–16 μm. Greatest neck width in creeping 29–37 μm. Greatest trunk width in creeping 30–46 μm. Greatest trunk width in feeding 70–73 μm. Greatest rump width in feeding 26–27 μm. Foot length in creeping 28–36 μm. Spur length 6–8 μm.

Distribution. This new species is known only from its type locality.

Etymology. The specific name undulata is an adjective, referring to the wavy lateral margins of trunk of the new species.

Figures

FIGURE 3. Habrotrocha microcornis n. sp. (a) creeping, dorsal view; (b) feeding head and neck, dorsal view; (c) foot, spurs and toes, ventral view; (d) light microscopy photograph of feeding head, dorsolateral view (an arrow pointing at a projection on sulcus base); (e) light microscopy photograph of feeding head, dorsal view (an arrow pointing at upper lip) (scale bars: a = 25 μm; b, d, e = 20 μm; c = 10 μm).

FIGURE 5. Philodina undulata n. sp. (a) creeping, dorsal view; (b) feeding, dorsal view; (c) foot, spurs and toes, ventral view (scale bars: a–b = 50 μm; c = 10 μm).

FIGURE 6. Light microscopy photographs of Philodina undulata n. sp. (a) creeping, dorsal view; (b) feeding, dorsal view; (c) feeding head, neck and antenna, dorsolateral view; (d) feeding head and neck, dorsal view; (e) foot and spurs, ventral view; (f) foot and spurs, lateral view (scale bars: a–b = 50 μm; c, e–f = 10 μm; d = 20 μm).