Philodinavus koreanus, Song & Lee, 2022

Song, Min Ok & Lee, Chang-Ho, 2022, Descriptions of Philodinavus koreanus n. sp. and two new species of Philodina (Rotifera, Bdelloidea) from Korea, Zootaxa 5129 (3), pp. 399-411 : 402-404

Philodinavus koreanus n. sp.

Figures 1 and 2

urn:lsid:zoobank.org:act:879843FE-64E2-4D10-B643-DB7C0B738553

Holotype and paratypes. On permanent slides, deposited in the collection of the National Institute of Biological Resources, Incheon, Korea (holotype: NIBRIV0000862817; two paratypes: NIBRIV0000862818 and NIBRIV0000862819) .

Type locality. A stream in Bangnae-ri , Nae-myeon , Hongcheon-gun, Gangwon-do, Korea. GPS coordinates based on WGS84 datum 37°48’24.5”N / 128°15’42.4”E .

Material. Six specimens sorted out from wet leaf litter in a stream, collected by Min Ok Song and Chang-Ho Lee on 6 May, 2019.

Differential diagnosis. Philodinavus koreanus n. sp. seems to be more similar to P. paradoxus than to P. aussiensis because of the absence of eyespots. In addition, Philodinavus koreanus n. sp. has the detailed morphology of trophi in common with P. paradoxus . While the ramus of both P. koreanus n. sp. and P. paradoxus has short caudal tip and is without a medial projection, that of P. aussiensis has a long caudal tip and is with a medial projection. However, in spite of the resemblances as above, Philodinavus koreanus n. sp. can be clearly distinguished from P. paradoxus by the following characteristics: (1) Philodinavus koreanus n. sp. has two ciliated buccal fields separated by a septum (upper and lower buccal fields, Figs. 1e and 2b ), while P. paradoxus has only one, and (2) Philodinavus koreanus n. sp. has a pair of thick and large as well as three pairs of small processes on the cheeks of lower buccal field ( Figs. 1a, b ), while P. paradoxus has only one pair of processes on cheeks bordering single buccal field ( Murray 1905).

In addition to the absence of eyespots and the difference in the trophi morphology as mentioned above, Philodinavus koreanus n. sp. is further distinguished from P. aussiensis by the following characteristics: (1) the spurs of Philodinavus koreanus n. sp. have wide interspace, while those of P. aussiensis are without interspace, and (2) the uncus of Philodinavus koreanus n. sp. has 19–20 minor teeth, while that of P. aussiensis has 17–20. Since Ricci et al. (2003) didn’t describe the morphology of ciliated buccal field of P. aussiensis , the comparison of the buccal field between P. koreanus n. sp. and P. aussiensis will be put on hold until further studies ( Ricci et al. 2003).

Description. Without eyespots. Rostrum much narrower than head; ratio of rostrum width to greatest head width about 1: 2.4. Rostral lamella bilobed and short; slightly wider than rostrum end width. Two, upper and lower, ciliated buccal field separated by thin and wavy septum; upper buccal field (ubf) enclosed by thick and wavy margin; lower buccal field with tree pairs of short projections anterolaterlly and a pair of paddle-shaped big projections posterolaterally ( Fig. 1 ); lower lip, posterior margin of lower buccal field, curly bracket-shaped ( Fig. 1b ). Trophi symmetrical ( Fig. 2g –h ) and protrusible; uncus with three major teeth anteriorly and about 19–20 minor teeth including short teeth between major teeth; ramus without medial projection and with short caudal tip; manubrium arched, thin, wide anteriorly and tapering towards last minor teeth. Dorsal antenna short. Trunk stout and rather cylindrical. Foot short and with three pseudosegments; foot length about 1/6 of total body length. Spurs big, wide and horn-shaped; spur length about 1.5–1.7 times as long as spur base width; interspace slightly narrower than spur base width. Four toes short and with plump bases; ventral toes longer and bigger than dorsal ones; ventral toes about 1.47 times as long as dorsal ones.

Measurements. Total length in creeping 139–200 μm. Greatest trunk width in creeping 23–44 μm. Trophi length 14–15 μm. Major teeth length 7.4–8.2 μm. Greatest major teeth width 0.86–0.93 μm. Minor teeth length 4.8–8.6 μm. Greatest minor teeth width 0.2–0.61 μm. Antenna length 6–9 μm. Spur length 10–14 μm. Ventral toe length 9 μm. Dorsal toe length 6 μm.

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

Etymology. The specific name koreanus is derived from the Republic of Korea, where the type locality is located.

Figures

FIGURE 1. Philodinavus koreanus n. sp. (a) head, upper buccal field somewhat closed, ventral view; (b) head, upper buccal field almost closed, ventral view; (c) head, trophi about to protrude from the lower buccal field, ventral view; (d) spurs and toes, dorsolateral view; (e) creeping, ventral view (scale bars: a–c = 20 μm; d = 10 μm; e = 25 μm). lbf, lower buccal field; s, septum; tr, trophi; ubf, upper buccal field.

FIGURE 2. Light microscopy photographs of Philodinavus koreanus n. sp. (a–b) creeping, ventral view; (c) head, trophi about to protrude from the lower buccal field, ventral view; (d) head, upper buccal field almost closed, ventral view; (e) head, upper buccal field somewhat closed; (f) scanning electron microscopy photograph of trophi, caudal view (× 6500); (g–h) trophi, cephalic view (scale bars: a–b = 50 μm; c–e = 25 μm; f = 2 μm; g–h = 10 μm). lbf, lower buccal field; m, manubrium; ma, major teeth; mi, minor teeth; r, ramus; ra, ramus apophysis; ro, rostrum; s, septum; tr, trophi; ubf, upper buccal field.