Homalogastra setosa Kahl, 1926

2. Homalogastra setosa Kahl, 1926 View in CoL

Material examined. Marine water (salinity 35‰) collect-

ed from Udo-myeon , Jeju-si, Jeju-do, Korea (33°30 ʹ 51 ʺ N, 126°56 ʹ 50 ʺ E) on May 29, 2024 GoogleMaps .

Diagnosis. Body size 12.6-15.3 × 7.4-8.3 μm after protargol impregnation (n = 11) ( Fig. 2A, B View Fig ). Body spindleshaped, both ends pointed, posterior end slightly asymmetrical ( Fig. 2A, B View Fig ). One globular macronucleus size 4.0-6.1 × 3.7-5.1 μm after protargol impregnation, located slightly above the body center ( Fig. 2F View Fig ). 13-15 bipolar somatic kineties ( Fig. 2A, B View Fig ); anterior apical plate conical and distinctly baren ( Fig. 2B, D View Fig ); one caudal cilium ( Fig. 2E View Fig ). Oral apparatus occupies about 74% of body length after protargol impregnation, composed of three adoral membranelles and paroral membrane; membranelle 1 with one basal bodies row ( Fig. 2C View Fig ); paroral membrane on average 5 μm long after protargol impregnation ( Fig. 2A View Fig ).

Distribution. Africa ( Buitkamp, 1977), Australia ( Pomp and Wilbert, 1988), Austria ( Foissner et al., 1982), Azerbaijan ( Alekperov, 2005), China ( Liu et al., 2020), Germany ( Kahl, 1926), and Korea (present study).

Remarks. The Korean population resembles the type population described by Foissner et al. (1982), but differs slightly in its smaller body length after protargol impregnation (12.6-15.3 μm vs. 20-25 μm), a higher number of somatic kineties (13-15 vs. 12), and a pointed anterior end (vs. truncated).

Homalogastra setosa and H. parasetosa Liu et al., 2020 closely resemble each other but can be distinguished by the number of ciliary rows in membranelle 1 (1 vs. 2). When Liu et al. (2020) established H. parasetosa , they considered populations of H. setosa with a double-row membranelle 1 as junior synonyms of H. parasetosa .

Voucher slides. One slide with protargol-impregnated specimens (MABIK PR00045076) were deposited at the National Marine Biodiversity Institute of Korea.