Thigmokeronopsis magna, Wilbert & Song, 2005

Wilbert, Norbert & Song, Weibo, 2005, New contributions to the marine benthic ciliates from the Antarctic area, including description of seven new species (Protozoa, Ciliophora), Journal of Natural History 39 (13), pp. 935-973 : 956-958

publication ID 10.1080/00222930400001509

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Thigmokeronopsis magna

sp. nov.

Thigmokeronopsis magna nov. spec.

( Figures 9 View Figure 9 , 15J–M, O View Figure 15 ; Table VII)


Large flexible marine Thigmokeronopsis about 150–300650–80 M m in vivo; ca 65 adoral membranelles extending to about one-third of cell length; 12–16 left postoral cirral rows forming thigmotactic field; 60 left and 70 right marginal cirri, about 43 and 15 pairs of cirri in midventral and frontal rows, respectively; one buccal, ten transverse and two frontoterminal cirri; three dorsal kineties; no caudal cirri; more than 150 macronuclear nodules; one contractile vacuole positioned in about mid-body.


Size mostly about 200660 M m, body very flexible and variable in shape but generally slender and elongate, with anterior part distinctly narrower than posterior; anteriorly narrowly rounded, posteriorly tapered; buccal field wide, about 30% of cell length ( Figure 9A View Figure 9 ). Pellicle thin, no cortical granules observed although cytoplasm usually brownish to dark brown in colour (due to food?) as observed under low magnifications. Cytoplasm with many tiny lipid droplets and food vacuoles containing mainly small and large pennate diatoms or small protozoans. Contractile vacuole on left of body and near equatorial level ( Figure 9A, H View Figure 9 ). More than 150 macronuclear nodules scattered throughout the cell ( Figure 9F View Figure 9 ), spherical to ellipsoid, usually with one to several large nucleoli ( Figure 9G View Figure 9 ).

Movement slow, usually three different modes observed: (1) crawling on bottom of Petri dish or debris, making small circular movement ( Figure 9I View Figure 9 ); (2) attached by thigmotactic field to the bottom while the raised anterior part of body makes (slow) left–right movements ( Figure 9J View Figure 9 ); or (3) when disturbed, relatively faster, crawling around irregularly. When swimming in water, moves slowly with no special features ( Figure 9B View Figure 9 ).

Buccal field large and deep. Adoral zone of membranelles extending far on to right side. Paroral and endoral membranes about equal in length, slightly bent in posterior portion, optically appearing to intersect ( Figure 9K View Figure 9 ). One buccal cirrus at about mid-level of undulating membranes.

About 15 frontal cirri forming bicorona, which are not clearly distinguished from the midventral cirri posteriorly although the anterior-most (usually three) cirri are conspicuously enlarged ( Figure 9K View Figure 9 ). Two midventral rows distinctly separated (so that the cirri are not arranged in typical zig-zag pattern), terminating near posterior rightmost transverse cirri ( Figure 9E, K View Figure 9 ). Left postoral cirral field (5thigmotactic field) consisting of about 13 (in maximum width) densely packed longitudinal rows, in each of which the cirri are basically loosely arranged ( Figure 15K View Figure 15 ). Bases of cirri in this thigmotactic field mostly smaller than other ‘‘normal’’ ones and more or less ovoid in shape ( Figures 9K View Figure 9 , 15K View Figure 15 ). Transverse cirri slightly enlarged and arranged in J-shape, joining thigmotactic field ( Figures 9D, E View Figure 9 , 15L View Figure 15 ). Marginal rows not confluent posteriorly. Dorsal kineties constantly three in number, densely ciliated (ca 3 M m long, Figure 15J View Figure 15 ); without caudal cirri.


Till now, four species within the genus Thigmokeronopsis have been described: T. jahodai , T. antarctica , T. rubra , and T. crystallis ( Wicklow 1981; Petz; Hu et al. 2004). Thigmokeronopsis antarctica is separated from the new species by having several buccal cirri, shortened midventral rows, only one thigmotactic cirral row and no transverse cirri. Thigmokeronopsis magna differs from T. crystallis in possessing many more cirral rows in the thigmotactic field (12–16 versus 4–7) ( Wicklow 1981; Petz 1995).

The new species is distinguished from the type species, Thigmokeronopsis jahodai Wicklow, 1981 , in that it has: (1) three dorsal kineties (versus four in T. jahodai ); (2) one buccal cirus (versus two in T. jahodai ); (3) more cirri in the midventral rows (ca 100 versus 50) ( Wicklow 1981).

Thigmokeronopsis rubra Hu et al., 2004 is a colourful (brick-red) species with two kinds of distinct cortical granules and thus can be clearly separated from T. magna . In addition, the former possesses fewer adoral membranelles (33–43 versus ca 65) and fewer thigmotactic cirral rows (7–11 versus 12–16) ( Hu et al. 2004).














Thigmokeronopsis magna

Wilbert, Norbert & Song, Weibo 2005

T. magna

Wilbert & Song 2005

Thigmokeronopsis rubra

Hu 2004
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