Opisthonecta minima Foissner, 1975

Jung, Atef Omar and Jae-Ho, 2021, New record of 21 ciliate species (Protozoa, Ciliophora) from South Korea, Journal of Species Research 10 (3), pp. 301-320 : 316-317

21. Opisthonecta minima Foissner, 1975 ( Fig. 20 )

Material examined. Freshwater sample collected from a temporary puddle, after rainfall, on a footpath behind Gangneung-Wonju National University, Gangneung, Korea (37°46 ʹ 30 ʺ N, 128°51 ʹ 46.8 ʺ E) on 25 June 2020 .

Diagnosis. Size in vivo about 90 × 43 μm (n = 3); body ellipsoid to broadly ellipsoid; macronucleus C-shaped located transversely in mid-body; a single contractile vacuole at anterior body portion; circular silverlines up to 60 striations between peristomial lip and trochal band and 30 striations between trochal band and scopula; infundibular polykineties 1-3 each consists of 3 rows, polykinety 3 with shorter inner row and longer and diverged outer 2 rows.

Distribution. Australia, Europe, North America, South America, and Korea.

Remarks. The Korean population of O. minima is similar to the type population in the body size and the presence of a single contractile vacuole but differs only in the number of silverline striations (total 90 vs. 60). Opisthonecta minima is also similar to O. henneguyi Fauré-Fremiet, 1906 in the appearance but is smaller (90 vs. 155 μm) and has less number of silverline striations (90 vs. 108 in total) and contractile vacuoles (1 vs. 2 or 3) ( Foissner, 1975; 1978).

Voucher slides. One slide with protargol-impregnated specimens was deposited at the Nakdonggang National Institute of Biological Resources (NNIBRPR20138).

D E

Figures

Fig. 20. Photomicrographs of Opisthonecta minima from life (A, B), after silver nitrate (C), and after protargol impregnation (D, E). A, B. Lateral views showing the body shape, the aboral wreath, the single contractile vacuole, and the food vacuoles. C. Lateral view showing the ciliature and silverline pattern. D, E. Lateral views of the same specimen showing the myoneme strands, the macronucleus, and the oral polykinetids. AW, aboral ciliary wreath; CP, cortical pores; CV, contractile vacuole; EM, epistomial membrane; MA, macronucleus; MY, myonenes; P1-3, oral polykinetids; S, scopula; V, vestibulum. Scale bars=30 μm.