Eschaneustyla lugeri Foissner, Agatha and Berger, 2002

Deng, Yufan, Lu, Xiaoteng, Li, Jingbao, Ba, Sang & Da Silva Paiva, Thiago, 2018, Morphology of Two Eschaneustyla Species (Ciliophora, Urostylida), with Notes on Morphogenesis of Eschaneustyla lugeri, Acta Protozoologica 57 (2), pp. 69-78 : 73-76

Morphology of Chinese population of Eschaneustyla lugeri Foissner, Agatha and Berger, 2002 ( Figs 1C–E , 2A–C ; Table 1 )

Body outline elongate elliptical and often slightly sigmoidal with anterior end broadly rounded and posterior end narrowly rounded, very flexible but not contractile, size in vivo about 200 × 60 μm. Contractile vacuole at left body margin slightly ahead of mid-body ( Figs 2A, B ). Cortical granules were failed to observe during living observation, but globular extrusomes were found after protargol impregnation. Extrusomes arranged around cirri and dorsal bristles, and irregularly scattered ( Fig. 2C ). Cytoplasm colorless, without conspicuous inclusions ( Figs 2A, B ). Nuclear apparatus occupying whole cell body, composed of 97–149 macronuclear nodules and three to 11 micronuclei ( Fig. 1E ). Cirral pattern and number of cirri of highly variability. AZM with 47–74 membranelles of ordinary composition, occupies 20%–37%, on average 28% of body length (DE-value on average 0.42). 25–43 frontal cirri form distinct short rows composed of 4 or 5 cirri each, except the leftmost one that composed of only two cirri. Paroral and endoral intersect optically after protargol impregnation. Usually three or four buccal cirri right of mid-portion of paroral ( Fig. 1D ). The majority of the specimens observed have one long, slightly oblique midventral row (as shown in Fig. 1D ). However, a small number of specimens (about 4 in 60 specimens observed) have a cirral pattern composed of two long midventral rows: the left one (midventral row 1 = MV1) and the right one (midventral row 2 = MV2) ( Fig. 1C ). The length of MV2 could be as similar to that of MV1, or rather short. MV2 could commence at the same level as frontoterminal row, or slightly behind anterior end of frontoterminal row, or at around onethird of body length ( Fig. 1C ). Specimen on the lower right in Fig. 1C shows a rather special cirral pattern that MV2 terminates near rear body end as frontoterminal row in other specimens, whereas frontoterminal row terminates quite ahead. One left and one right marginal row, left row distinctly curved rightwards anteriorly; transverse cirri absent ( Fig. 1D ). Usually four rows of dorsal kineties, each with one to three, thus totally seven to 11 caudal cirri ( Fig. 1E ). Length of dorsal bristles is about 5 μm.

Morphogenesis in Eschaneustyla lugeri ( Figs 1F–L , 2F–M )

Stomatogenesis. In the proter, the oral primordium commences in deep of the cortex independently, at around the proximal portion of AZM. Undulating membranes anlage that develops on the surface found to the right of oral primordium at the same time ( Figs 1F, G ; 2G ). Specimen in Fig. 2G somewhat twisted at anterior portion, thus the undulating membranes anlage presented to the left of the oral primordium. Parental undulating membranes not observed in this stage, we speculate that it disorganized into undulating membranes anlage. Parental buccal cirri might be absorbed in earlier stage due to their absence in this stage. Stomatogenesis of the opisthe commences with the proliferation of basal bodies around and on the left of midventral row 1, in which posterior cirri gradually absorbed (parental cirri become smaller without any sign of disaggregation, thus absorption is supposed) ( Figs 1F , 2F ).

The proter’s oral primordium subsequently moves to the proximal end of AZM and develops in the shape of a round concavity. The central part still remains in the depth of the cortex while the surrounding portion gradually migrates to the surface ( Fig. 1H ). Basal bodies then move along the left margin of AZM and engage in the renewal of membranelles with dissolving of parental membranelles ( Fig. 1I ). Undulating membranes anlage elongates anteriorly and connects with the oral primordium at the posterior end ( Figs 1H, I ; 2H ).

Membranelles begin to differentiate at the right anterior part of opisthe’s oral primordium ( Figs 1F, H ). Meanwhile, undulating membranes anlage for the opisthe appears, with differentiation commencing at the anterior end to form the leftmost frontal cirri ( Fig. 1H ).

In the mid-to-late stage, renewal of posterior portion of parental AZM continues on, which will eventually result in a partly renewed AZM of the proter. It should be noted that except for the few most proximal membranelles replaced by the new structure, others only slightly renewed at left sides. Specimen observed reveals that residual oral primordium of the proter has all migrated to the surface by this stage. As for the opisthe, membranelles continue to differentiate posteriad. Note that two leftmost frontal cirri of the opisthe have already formed from frontoventral cirral anlage I ( Fig. 1K ).

Development of frontoventral cirri. In early dividers, posterior portion of the parental frontal cirri dissolve into basal bodies, which begin to form the frontoventral cirral anlagen of the proter ( Figs 1F, H ; 2H ). A few frontoterminal cirri near proximal end of AZM disaggregate to develop the penultimate frontoventral cirral anlage. A small field of basal bodies, regarded as the frontoventral cirral anlage n, develop on the right side of frontoterminal row de novo. Opisthe’s frontoventral cirral anlagen appear on the right side of frontoventral cirral anlage I. Due to the hypochromatism after protargol impregnation, a small field around frontoterminal row in mid-body region was difficult to see (dashed circle in Fig. 1H ). Only a few cluttered basal bodies develop around this field. It is not known whether these basal bodies completely come from dissolving frontoterminal cirri ( Fig. 1H ). In the next stage, frontoventral cirral anlagen develop into distinct streaks and elongate posteriad in both daughter cells. About 9–11 frontoventral cirral anlagen, including the last and the penultimate anlagen, eventually formed ( Figs 1I , 2L ). In some filial products, several small anlagen formed on the left of penultimate frontoventral cirral anlage, and these anlagen will possibly be absorbed subsequently ( Fig. 2L ). In the mid-to-late stage, frontoventral cirral anlagen segment and cirri gradually formed. The rightmost and the penultimate frontoventral cirral anlage eventually develops into the new frontoterminal row and MV1 respectively, while the rest of frontoventral cirral anlagen each splits to form about 4–6 cirri ( Figs 1K , 2K, M ). Although late dividers not found, we could believe that formation and migration of new cirri, and absorption of old ones are the main events during the rest of the morphogenetic process.

Marginal and dorsal anlagen. Two separate marginal anlagen develop intrakinetally within both left and right marginal rows. Cirri adjacent to anterior end of each marginal row and cirri slightly behind mid-body differentiate to form these two anlagen, respectively ( Figs 1I, K ; 2K ). These anlagen then increase in size and develop into new cirri that eventually replace the old ones.

During the formation of dorsal kineties, two anlagen develop intrakinetally in each parental row. These anlagen then elongate and develop into new structures, along with the incorporation or absorption of parental structures ( Figs 1J , 2I ).

Division of the nuclear apparatus. Macronuclear nodules fuse into many masses during early stage ( Fig. 1J ) and eventually fuse into a single mass that divides subsequently during mid-to-late stage ( Figs 1L , 2J ). Micronuclei divide mitotically during cell division ( Fig. 1J ).

Figures

Fig. 1. Eschaneustyla terricola (A, B) and E. lugeri (C–E) during interphase, and E. lugeri during morphogenesis (F–L), after protargol impregnation. (A, B) Ventral and dorsal view of same specimen, showing ciliature. Cirri formed from same anlage were connected by solid line. Asterisk denotes the distal end of AZM. (C) Schematic representations of midventral-complex of four E. lugeri specimens with two long midventral rows.Arrows and arrowheads denote midventral rows 1 and 2, respectively. (D, E) Ventral and dorsal view of same specimen, showing typical infraciliature. Cirri formed from same anlage were connected by solid line. Two leftmost cirri develop from anterior part of undulating membranes anlage (dotted line). (F) Ventral view of an early divider that twisted a little at the anterior end, to show the oral primordia of proter (arrow) and opisthe (arrowhead). (G) Enlarged image of proter’s oral primordium (arrow) and undulating membranes anlage (arrowhead) of the individual shown F. Note that the former develops in deep of the cortex while the latter develops in the surface. (H) Ventral view of an early divider to show the frontoventral cirral anlagen (arrows).Arrowhead denotes the penultimate frontoventral cirral anlage which forms midventral row 1. Double-arrowhead denotes the frontoventral cirral anlage n that develops into frontoterminal row. Dashed circle represents the flurry area due to the hyperchromatism after protargol impregnation. (I, J) Ventral and dorsal view of an early divider to show the frontoventral cirral anlagen. Arrows and arrowheads in I mark the penultimate and the last frontoventral cirral anlagen, respectively. Note that marginal anlagen and dorsal kineties anlagen (arrows in J) develop intrakinetally. Macronuclear nodules are fusing (arrowheads in J). (K) Ventral view of a middle divider. Arrow marks the partly renewed adoral zone of membranelles of proter. Asterisk denotes two leftmost frontal cirri developed from the undulating membranes anlage. L. Nuclear apparatus of the same specimen as shown in K. Note that macronuclear nodules are fusing into a single mass. AZM, adoral zone of membranelles; CC, caudal cirri; E, endoral; FT, frontoterminal row; LMA, left marginal anlage; LMR, left marginal row; Ma, macronuclear nodules; Mi, micronuclei; MV, midventral row; MV 1, midventral row 1; 1–4, dorsal kineties 1–4; P, paroral; RMA, right marginal anlage; RMR, right marginal row. Scale bars: 100 μm (A, B, D, E); 70 μm (F–L).

Fig. 2. Photomicrographs of Eschaneustyla lugeri (A, B) and E. terricola (D, E) in life and E. lugeri after protargol impregnation (C, F–M). (A, B) Representative individuals. Arrow in A denotes the contractile vacuole. (C) Dorsal side to show the arrangement of extrusomes (arrows). (D) Arrangement of cortical granules. (E) Ventral view. Arrow marks the contractile vacuole. It should be noted that the specimen in E is slightly damaged, thus it doesn’t present a narrowly rounded posterior end. (F–H) Ventral views of early dividers, to show the oral primordia of opisthe (F) and proter (arrow in G), the undulating membranes anlage (arrowhead in H) and the frontoventral cirral anlagen (arrow in H). (I) Dorsal view of an early divider to show the intrakinetal development of dorsal kineties anlagen (arrows). (J) Fusion of macronuclear nodules. (K–M) Ventral views of middle dividers. Note that right marginal anlage develops intrakinetally (arrow in K).Arrow in L denotes the formation of the leftmost frontal cirri from frontoventral cirral anlage I. In M, arrow marks the frontoventral cirral anlage n that becomes the frontoterminal row and arrowhead depicts the penultimate frontoventral cirral anlage that forms midventral row 1, respectively. Ma, macronuclear nodules. Scale bars: 100 μm (A, B, E); 40 μm (C, F, G, I); 15 μm (D, J); 25 μm (H, K–M).

Tables

Table 1. Morphometric data on Eschaneustyla terricola (te) and Eschaneustyla lugeri (lu), after protagol impregnation.

Characteristica	Species	Min	Max	Mean	M	SD	SE	CV (%)	n
Body, length	te	130.0	222.0	187.6	195.0	28.3	8.5	15.1	11
	lu	164.0	348.0	261.8	261.5	54.0	10.2	20.6	28
Body, width	te	50.0	90.0	69.3	70.0	11.9	3.6	17.2	11
	lu	38.0	141.0	91.4	95.0	29.1	5.5	31.9	28
Body length:width, ratio	te	1.9	3.3	2.7	2.8	0.4	0.1	13.2	11
	lu	2.0	5.5	3.0	2.8	0.8	0.1	26.1	28
Macronuclear nodules, number	te	59	106	75.4	68.0	15.3	4.6	20.3	11
	lu	97	149	119.6	119.0	13.6	3.3	11.4	17
Micronuclei, number	te	1	5	3.1	3.0	1.2	0.4	38.6	10
	lu	3	11	5.9	5.0	2.1	0.5	35.5	21
Anteriormost macronuclear nodule, length	te	5.5	16.0	9.5	9.5	3.3	1.0	34.1	11
	lu	5.0	21.0	11.0	10.0	4.6	1.1	41.7	19
Anteriormost macronuclear nodule, width	te	2.5	7.0	4.5	5.0	1.4	0.4	32.2	11
	lu	3.0	10.0	5.3	5.0	2.0	0.4	36.7	19
Anteriormost micronucleus, length	te	3.0	5.0	3.8	4.0	0.6	0.2	14.7	11
	lu	3.0	10.0	6.1	6.5	2.0	0.5	33.3	19
Anteriormost micronucleus, width	te	3.0	4.0	3.5	3.5	0.5	0.1	13.7	11
	lu	3.0	8.0	5.3	5.0	1.6	0.4	30.1	19
AE to first macronuclear nodule, distance	te	9.0	22.5	15.8	16.0	3.8	1.1	24.0	11
	lu	16.0	35.0	23.8	26.0	5.8	1.3	24.5	19
PE to rearmost macronuclear nodule, distance	te	8.0	27.5	17.2	18.0	6.2	1.9	36.0	11
	lu	14.0	60.0	30.7	27.0	12.6	3.1	41.2	17
Posteriormost macronuclear nodule, length	te	3.0	11.0	7.4	7.0	2.7	0.8	37.1	11
	lu	5.0	14.0	8.7	8.0	2.5	0.6	29.0	17
Posteriormost macronuclear nodule, width	te	3.0	6.5	4.5	4.0	1.2	0.4	26.2	11
	lu	2.0	10.0	4.3	3.5	2.3	0.6	55.0	17
Adoral membranelles, number	te	35	47	41.5	41.0	3.4	1.0	8.3	11
	lu	47	74	61.2	62.0	5.7	1.1	9.3	25
Frontal cirri, number	te	3	3	3.0	3.0	0.0	0.0	0.0	11
	lu	25	43	35.5	35.5	4.5	0.9	12.7	24
Buccal cirri, number	te	1	1	1.0	1.0	0.0	0.0	0.0	11
	lu	3	4	3.3	3.0	0.5	0.1	14.3	25
AE to proximal end of AZM, distance	lu	38.0	99.0	77.3	78.0	15.7	3.1	20.3	25
AE to distal end of AZM, distance	lu	12.0	58.0	33.4	33.0	10.1	2.0	30.4	25
DE value	lu	0.3	0.59	0.42	0.42	0.1	0.0	16.7	25
AE to paroral, distance	lu	23.0	50.0	38.3	40.0	6.3	1.3	16.4	22
Paroral, length	lu	21.0	43.0	33.4	33.0	5.3	1.1	15.8	22
AE to first buccal cirrus, distance	lu	30.0	64.0	49.0	51.0	7.5	1.6	15.3	21
AE to last buccal cirrus, distance	lu	36.0	75.0	59.2	62.0	8.7	1.9	14.7	21
Frontoterminal row, number of cirri	te	20	28	25.1	25.5	3.0	0.9	11.9	10
	lu	30	60	49.5	50.0	6.9	1.4	13.9	23
RMR, number of cirri	te	39	57	45.6	45.5	5.2	1.6	11.4	10
	lu	41	78	58.4	59.0	7.9	1.8	13.6	20