Hemigastrostyla szaboi, 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 : 966-969

publication ID

https://doi.org/ 10.1080/00222930400001509

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scientific name

Hemigastrostyla szaboi

sp. nov.

Hemigastrostyla szaboi nov. spec.

( Figure 11A–D View Figure 11 , 16G–L View Figure 16 ; Table VIII)

Diagnosis Medium-sized marine Hemigastrostyla in vivo about 100–150630–50 M m with elongated

body shape; ca 27 adoral membranelles, eight (including one buccal) frontal, five ventral, five transverse and three caudal cirri; left and right marginal row each with 23 cirri on average, three dorsal kineties; two macro- and two to six micronuclei.


We dedicate this species to the Hungarian protozoologist, Dr Andras Szabo, in recognition of his contributions to the study of ciliates.


Cells generally inflexible; body shape distinctly slender with both ends only slightly narrowed, ratio of cell length to width about 3:1 ( Figure 11A View Figure 11 ); buccal field narrow, about one-third to two-fifths of body length; dorsoventrally flattened 1:2. Cell margins generally parallel but in anterior portion often slightly swelling outward. Ventral side conspicuously grooved because of the presence of marginal rows ( Figure 11A View Figure 11 , arrow).

Pellicle thin; no cortical granules recognizable (not carefully observed). Cytoplasm often containing numerous light-reflecting globules (3 M m across), which render the cell completely dark, especially in posterior portion of body. Food vacuoles basically not detectable. No contractile vacuole detected. Two macronuclei, elongate and often conspicuously separated from each other ( Figures 11D View Figure 11 , 16K View Figure 16 ); two to five oval micronuclei near macronuclei ( Figure 16G View Figure 16 , arrows).

Movement relatively slow, crawling without pause on debris.

Buccal field narrow, adoral zone of membranelles (AZM) extending to about one-third of body length, bases of membranelles up to 8 M m long, cilia ca 15 M m long in vivo. Distal end of adoral zone of membranelles bending considerably posteriad at right margin. Paroral and endoral membranes about equally long, parallel to each other. Pharyngeal fibres short and conspicuous after protargol impregnation ( Figure 11C View Figure 11 ).

Frontal area constantly eight cirri, anterior two to three of which are distinctly enlarged, while others are smaller ( Figure 11C View Figure 11 ). Single buccal cirrus (counted among frontal cirri in Table VIII), situated beside mid-point of undulating membranes. Three postoral ventral cirri anteriorly located, immediately beneath the cytostome level ( Figure 11C View Figure 11 ), while two pretransverse ventral cirri close to five terminally positioned thick transverse cirri. Right marginal row terminating subcaudally anterior to rightmost transverse cirrus, which often gives an appearance of confluence of right marginal cirri and TC ( Figure 16L View Figure 16 , arrow). Cirri in both marginal rows rather large and densely spaced; anterior portions of right marginal row often extending on to dorsal side. At posterior end, the two marginal rows widely separated. All cirri associated with strongly impregnated fibre system ( Figures 11B View Figure 11 , 16I, L View Figure 16 ).

Dorsal kineties constantly three, cilia about 3 M m long, positioned in small pit as recognized after impregnation. Three caudal cirri located caudally on cell margin ( Figure 11D View Figure 11 , arrowheads).


The genus Hemigastrostyla previously contained only two species ( Borror 1963; Song and Wilbert). This new organism can be separated from the closely related H. enigmatica (Dragesco and Dragesco-Kernéis 1986) Song and Wilbert by having fewer frontal and buccal cirri (eight versus consistently more than eight in the latter), no ‘‘extra’’ ventral cirri (versus present), fewer dorsal kineties (three versus five) and the body shape (non-cephalized versus cephalized) (Dragesco and Dragesco-Kernéis 1986; Song and Wilbert 1997). Differences from H. stenocephala ( Borror 1963) Song and Wilbert 1997 , are that the new species has conspicuously shorter dorsal cilia (ca 3 versus 16 M m in length in H. stenocephala ), fewer frontal and ventral cirri (13 versus 17), less slender body shape and no extra ventral cirri (versus two in H. stenocephala ) ( Borror 1963).

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