Aporthotrochilia pulex, (DEROUX, 1976), 2012

Pan, Hongbo, Lin, Xiaofeng, Gong, Jun, Al-Rashied, Khaled A. S. & Song, Weibo, 2012, Taxonomy of five species of cyrtophorids (Protozoa: Ciliophora) including consideration of the phylogeny of two new genera, Zoological Journal of the Linnean Society 164 (1), pp. 1-17 : 6-7

APORTHOTROCHILIA PULEX (DEROUX, 1976) COMB. NOV. ( FIG. 3 ; TABLE 3)

Basionym: Trichopodiella pulex Deroux, 1976 .

New diagnosis: Body oval in outline, size in vivo 25–40 ¥ 15–20 Mm; a small podite subterminally positioned; two contractile vacuoles situated on right side; one frontoventral kinety and three to five posterior fragments; nine to ten ventral kineties in postoral field; four to five terminal fragments; marine habitat.

Slide deposition: One voucher slide with protargol specimens is deposited in the Natural History Museum, London, UK with registration number 2010:11:7:3. Another two slides are deposited in the Laboratory of Protozoology, Ocean University of China (no. PHB 09121509).

All measurements in Mm. CV, coefficient of variation (%); FvK, frontoventral kineties; Ma, macronucleus; Max., maximum; Mean, arithmetic mean; Min., minimum; N, number of specimens; PF, posterior fragments; SD, standard deviation; SK, somatic kineties; TF, terminal fragments.

Redescription: Body size about 25–40 ¥ 15–20 Mm in vivo; cells oval shaped with left margin sometimes slightly sigmoidal, both end bluntly rounded. Dorsoventrally flattened, ventral side flat and dorsal side slightly vaulted ( Fig. 3A–E, I, N ). Cytostome relatively small, subanteriorly positioned, nematodesmal rods hard to detect. Cytoplasm colourless or greyish, with several tiny, greasily shining granules (1–2 Mm across) and few food vacuoles (4–5 Mm across). Two contractile vacuoles (c. 3 Mm in diameter) positioned in anterior and posterior one-third near right margin ( Fig. 3F , arrows). Podite inconspicuous, 4 Mm long, subterminally positioned ( Fig. 3H , arrow). Macronucleus ellipsoid, positioned in body centre, heteromerous. Micronucleus not detected. Cilia about 6 Mm long. Movement by slowly gliding on substrate.

Infraciliature as shown in Figure 3G, J, K, L, M, P–T . The short three to five right-most of the ventral kineties, which are anteriorly shortened progressively from left to right and posteriorly positioned, forming posterior fragments (PFs); the longest PF only extending forward to anterior one-third of body length ( Fig. 3M, P, R ). One frontoventral kinety (FvK) positioned next to PF extending apically. Both FvK and PF terminating posteriorly at the same level, and basal bodies densely arranged at their posterior ends ( Fig. 3R , arrowheads). Nine to ten ventral kineties postorally positioned, strongly shortened from right to left. Terminal fragments consisting of four to five fragments ( Fig. 3G, Q ). Equatorial fragment not detected. Perioral kineties positioned anterior to cytostome, consisting of two fragments, both distinctly separated and composed of dikinetids.

Morphogenesis: Only two specimens in middle and late stages of the morphogenetic process have been observed ( Fig. 3K, L, S, T ). These showed that (1) perioral kineties of opisthe were developed from the oral primordium in midbody, which is generated from sections of postoral kineties; (2) the posterior fragments of both proter and opisthe stem from the parental posterior fragments.

Remarks: Deroux (1976c) described a species under the name of Trichopodiella pulex with its infraciliature ( Fig. 3O ) in detail: one frontoventral kinety, 11 postoral kineties and three or four posterior fragments; the postoral kineties strongly shortened. However, he did not note whether the podite is present. Our isolate corresponds very well to the original report in terms of infraciliature, except for the only difference in the number of postoral kineties (ten vs. 11), which is, however, considered minor. Therefore, our isolate should represent a population of Trichopodiella pulex .

However, during our study, we found this organism was quite different from other Trichopodiella spp. by: the presence of podite (vs. absence), four to five terminal fragments (vs. single), three to five distinct posterior fragments (vs. none) and two perioral kineties (vs. single) ( Fauré-Fremiet, 1957; Deroux & Dragesco, 1968; Deroux, 1976c; Gong et al., 2008). Therefore, we concluded that this small species should represent a distinct genus, and assigned it to the new genus Aporthotrochilia as Aporthotrochilia pulex (Deroux, 1976) gen. et comb. nov.

Figures

Figure 3. Morphology and infraciliature of Aporthotrochilia pulex gen. et comb. nov. from life (A–F, H, I, N) and after protargol impregnation (G, J–M, O–T). A, ventral view of a typical individual. B-E, H, I, showing shape variants of different individuals, arrow in (H) points to podite. F, ventral view, arrows mark contractile vacuoles. G, dorsal view, arrowhead points to terminal fragments. J, ventral view. K. ventral view, to show the infraciliature of an individual in middle stage of morphogenesis. L, ventral view of an individual in late stage of morphogenesis. M, posterior portion, arrowheads indicate posterior fragments. N, ventral view of a typical individual. O, ventral view, from Deroux (1976c). P, ventral view. Q, anterior portion of dorsal side. R, posterior of ventral side, arrowheads point to densely arranged basal bodies in caudal. S, ventral view, to show the infraciliature of an individual in middle stage of morphogenesis. T, ventral view of an individual in late stage of morphogenesis. Abbreviations: FvK, frontoventral kineties; Ma, macronucleus; Pe, perioral kineties; PF, posterior fragments; TF, terminal fragments. Scale bars = 20 Mm.