Cyrtohymena australis Foissner, 1995

Kim, Yeon Uk, Lee, Jung Mi, Kwon, Choon Bong & Shin, Mann Kyoon, 2012, Morphological redescriptions of three Cyrtohymena ciliates (Ciliophora: Sporadotrichida: Oxytrichidae) new to Korea, Journal of Species Research 1 (1), pp. 78-86 : 79

1. Cyrtohymena australis Foissner, 1995

ĀỸḦỢḄRệ(Ḫḏ) ( Fig. 1 , Table 1) Cyrtohymena australis Foissner, 1995, p. 70 , figs. 110-

119; Berger, 1999, p. 296, fig. 97.

General morphology and behavior: Body size in live specimens 250-288 × 85-115 µm, usually 275 × 100 µm, length: width ratio about 3: 1 on average. Body shape generally elongated elliptical to slightly oval, anterior end broadly rounded, posterior end narrowly rounded, ventral side flatted, dorsal side convex in mid-region ( Fig. 1A ). Body very flexible and slightly contractile ( Fig. 1E ). Contractile vacuole located in mid-region near left margin of cell, approximately 13-16 µm in diameter during diastole, with inconspicuous collecting canals ( Fig. 1D ). Cytoplasm colorless, with ellipsoidal fat globules 2-3 µm long. Cell yellowish green at low magnification due to yellow cortical granules, 0.5-1 µm in across, mainly in groups of two to five in anterior and posterior ends and grouped around bases of cirri and dorsal bristles ( Fig. 1F ). Locomotion by gliding or crawling on substratum, or freely swimming.

Buccal field and oral infraciliature: Adoral zone of membranelles shaped like a question mark, about 42% of cell length with 55-60 adoral membranelles. Buccal area large and deep. Undulating membranes in typical Cyrtohymena -pattern; paroral bent in a broad arc along anteri- or margin of oral cavity; endoral sharply bent to left in mid-region; membranes optically intersect near mid-region of paroral. Pharyngeal fiber about 35 µm long ( Fig. 1G ).

Somatic infraciliature: Three enlarged frontal cirri. Buccal cirrus located to right of paroral. Four frontoventral cirri arranged in a V-shape. Three, rarely two postoral ventral cirri just below buccal vertex. Two pre-transverse cirri. Five prominent transverse cirri at about level of posteriormost right marginal cirri. Right marginal row with 18-31 cirri, left marginal row with 31-40 cirri and extends around posterior end of cell onto right side; posterior ends of marginal rows distinctly separated. Eight dorsal kineties, dorsal bristles short ( Fig. 1B, G ). Three caudal cirri located slightly right of centre ( Fig. 1C ).

Nuclear apparatus: Two ellipsoidal macronuclear nodules, 38-40 × 23-25 µm in protargol-impregnated specimens, nodules slightly left of cell median, anterior nodule located just below buccal vertex, posterior nodule slightly below equatorial region. Six spherical micronuclei, 2-5 µm, closely associated with macronuclear nodules ( Fig. 1B, G ).

Microhabitats. Freshwater of farmland in Korea, soil from the Amazon rain forest in Peru, soil from a dry forest in Costa Rica, and saline soil in Venezuela.

Distribution. South and Central America (Csta Rica, Peru and Venezuela) and Asia ( Korea).

Remarks. The Korean population of Cyrtohymena australis Foissner, 1995 is characterized by 2 or more micronuclei, yellowish cortical granules, freshwater habitat and large body size about 275 × 130 µm. The Korean population resembles those from Peru and Costa Rica, however it differs slightly from both populations in having: a slightly larger body size (150 µm vs. 97 µm in Peru, 68 µm in Costa Rica), fewer right marginal cirri (28 vs. 36 in Peru and 33 in Costa Rica populations); more dorsal kineties (5-9 vs. 5-7 in both populations); no fan-shap- ed fibers attached at anterior portion of the paroral membrane (vs. fan-shaped fibers present in both populations) ( Foissner, 1995, 1997).

This species is similar to Cyrtohymena citrina ( Berger and Foissner, 1987) and C. primicirrata ( Berger and Foissner, 1987) in having yellowish cortical granules. C. australis , however, has a larger body size in live specimens (250-288 µm vs. 75-112 µm in C. citrina , vs. 74-102 µm in C. primicirrata ).

Figures

Fig. 1. Cyrtohymena australis Foissner, 1995 from live (A, D, E, F) and protargol-impregnated specimens (B, C, G). A, D. Ventral view of a typical individual. B, G. Ventral view of general infraciliature and nuclear apparatus. C. Showing dorsal kineties and caudal cirri. E. Flexible body. F. Cortical granules on dorsal side. Scale bar=100 µm.