Nassula exigua Kahl, 1931

Jung, Jae-Ho & Yeo, Jeong Hyeon, 2020, New record of five ciliate species from temporary ponds on a grass lawn, Journal of Species Research 9 (1), pp. 68-76 : 71-72

2. Nassula exigua Kahl, 1931

Diagnosis. Body size 32-39 × 14-25 μm, on average

35.3 × 17.5 μm, after protargol impregnation; body shape ellipsoidal to oval. Nuclear apparatus composed of a single spherical to ellipsoidal macronucleus (7.9-9.5 × 7.3- 8.1 μm) and one micronucleus (2.2 × 2.1 μm, n = 1) at variable positions, from anterior to posterior body end. Extrusomes lacking. 14 pharyngeal rods; 4 nassulid organelles, leftmost one on lateral side. 14 somatic kineties.

Distribution. Europe, USA, Venezuela, and Korea.

Remarks. Nassula exigua highly resembles N. parva Kahl, 1928 , but can be distinguished by the body size (in vivo 27-45 vs. 40-70), the number of micronuclei (two or three vs. one), pharyngeal rods (8-12 vs. 12-18), and nassulid organelles (three or four vs. four or five) ( Foissner et al., 2002). However, the Korean population interestingly shows an intermediate morphology between the two species. In the present study, we found only a few protargol-impregnated specimens and, as mentioned by Foissner et al. (2002), further study, especially concerning the number of micronuclei, is necessary to determine whether N. exigua and N. parva are distinct species. In addition, they stated that this species might be assigned to Naxella Fryd-Versavel et al., 1980 ; however, for the generic assignment, further study on the pharyngeal basket is necessary.

Voucher slides. Two slides of protargol impregnated specimens were deposited at National Institute of Biological Resources, Korea (NIBRPR0000110177, NIBRPR 0000110178).