Arcuospathidium bromelicola, Foissner & Wolf & Kumar & Quintela-Alonso, 2014

Foissner, Wilhelm, Wolf, Klaus W., Kumar, Santosh & Quintela-Alonso, Kuidong Xu and Pablo, 2014, Five New Spathidiids (Ciliophora: Bromeliads Haptoria) from Caribbean Tank, Acta Protozoologica 53, pp. 159-194 : 160-165

Arcuospathidium bromelicola nov. spec. ( Figs 1a–n ,

2a–m , 3a–k ; Table 1)

Diagnosis: Size about 85 × 30 µm in vivo; spatulate to narrowly spatulate. Macronuclear strand in middle body third, tortuous to horseshoe-shaped; micronucleus broadly ellipsoidal. Contractile vacuole in rear body end. Extrusomes rod-shaped with rounded ends, about 4–5 × 0.3 µm in vivo. On average 14 ciliary rows. Dorsal brush distinctly heterostichad, rows 1 and 2 of similar length, composed of an average of 10 and 13 dikinetids, respectively; row 3 shorter than longest row 2 by about 55%, composed of an average of 7 dikinetids. Oral bulge oblique, moderately convex, cuneate, on average 25 µm long in vivo, in 70% of specimens slightly to distinctly bent in proximal third. Resting cyst surface studded with 2–3 µm high pillars distally frayed.

Type locality: In tank bromeliads from the “Upper Cedar Valley”, southern slope of the Blue Mountains, Jamaica, 18°2′N 76°34′W .

Type material: 1 holotype and 3 paratype slides with protargol-impregnated specimens have been deposited in the Biologiezentrum of the Oberösterreichische Landesmuseum in Linz ( LI), Austria. Relevant specimens have been marked by black ink circles on the coverslip .

Etymology: Composite of Bromeliaceae , the plants in whose leaf-tanks it occurs, and cola from the Latin verb colere (to dwell), referring to its habitat.

Description: Size 60–115 × 15–40 µm in vivo, usually about 85 × 30 µm, as calculated from live measurements and the morphometric data in Table 1, adding 15% for preparation shrinkage. Body length: width ratio in vivo 2.5:1, after protargol impregnation 3.3:1. Shape narrowly spatulate (theronts) to spatulate (trophonts), dorsal outline slightly sigmoidal, ventral convex with rather distinct concavity at proximal end of oral bulge, anterior end oblique, posterior rounded; laterally flattened up to 2:1 ( Figs 1a, e, f, i, m, n , 2a, b , 3a, b ). Macronucleus in middle third of body, a tortuous strand in about 71% of specimens (out of 21 cells), horseshoe-shaped in about 24%, and C-shaped in one specimen, contains many small and some large nucleoli; some post-conjugants with two macronuclear nodules ( Fig. 3j ). Micronucleus attached to macronucleus at various positions, ellipsoidal, in three specimens with a minute, hemispherical cap; often difficult to identify because of similarly sized and impregnated cytoplasmic inclusions ( Figs 1a, e, m, n , 3a, b, f, i ; Table 1). Contractile vacuole in rear body end, on average 3 excretory pores ( Figs 1a, m, n , 2a ; Table 1). Extrusomes packed in oral bulge and scattered in cytoplasm, rod-shaped with rounded ends, in vivo about 4–5 × 0.3 µm in size; cytoplasmic extrusomes sometimes impregnate with the protargol method used ( Figs 1a, d, j , 2c , 3i ; Table 1). Cortex very flexible, contains ordinarily spaced rows of granules between each two kineties; granules colourless and hyaline, ≤ 0.2 µm in size ( Fig. 1b ). Cytoplasm colourless, oral area hyaline, trunk usually opaque due to food vacuoles up to 30 µm across and few to many globular or slightly irregular lipid droplets up to 6 µm in size. Feeds on middle-sized ciliates, such as Colpoda sp. recognizable in two specimens, Glaucomides bromelicola , flagellates, and possibly starch grains from the wheat kernels added to the culture ( Fig. 3k ). Swims moderately fast or glides rapidly, most cells gather at margin of organic accumulations composed of bacteria, flagellates and Glaucomides .

Cilia in vivo 9 µm long, arranged in an average of 14 meridional, ordinarily (theronts) to widely (trophonts) spaced rows abutting on circumoral kinety and composed of densely spaced cilia not condensed anteriorly; right side rows anteriorly curved dorsally, left side rows straight. Dorsal brush heterostichad and isomorphic, rows 1 and 2 composed of 7–15 and 11–17 dikinetids, respectively, both of almost same length with longest row 2 occupying only 14% of body length on average; bristles slightly inflated, anterior bristles about 2.5 µm long, posterior about 2 µm. Row 3 shorter than row 2 by 55%, composed of 4–10 dikinetids, followed by a short posterior tail composed of 3–5 monokinetidal bristles 2 µm long; all rows with a short anterior tail of ciliated monokinetids ( Figs 1a, e, f , 3a, b, d, e, j, k ; Table 1).

Oral bulge studded with extrusomes, about as long as widest trunk region, inclined to main body axis by about 40–60°, surface strongly convex in 24% of specimens (out of 21), moderately convex in 62%, and flat in 14%, cuneate in ventral view, in protargol preparations 23 × 6 × 3 µm in size; in 70% of specimens slightly to distinctly bent mainly in proximal third ( Figs 1a, c, d, g–i , 2a , 3a–c, e, g–i ; Table 1). Circumoral kinety of the same shape as oral bulge, composed of narrowly spaced dikinetids. Oral basket not impregnated with the protargol method used.

Resting cysts in vivo on average 26 µm across ( Table 1); covered by a thin mucus layer containing bacteria and flagellates. Cyst wall light brown to honey-brown, about 2 µm thick, composed of a thin external and a thick internal layer both structureless in the light microscope. Cyst surface studded with 1–3 µm high, honey-brown pillars (lepidosomes?) distally frayed; pillars rarely spinous, can be overturned in squashed cysts, indicating that they are lepidosomes. Cyst contents close to wall, dominated by lipid droplets 1–3 µm across. Macronuclear strand shorter than in vegetative specimens ( Figs 1k, l , 2d–m ).

Occurrence and ecology: As yet found only at type locality; became moderately abundant in raw cultures.

Remarks: Arcuospathidium bromelicola is very similar to A. muscorum muscorum (for a review, see Foissner and Xu 2007), from which it differs by the structure of the cyst (wall with conspicuous pillars vs. smooth) and the shape of the oral bulge (proximal third often rather strongly curved vs. straight or slightly curved).

Figures

Figs 1a–n. Arcuospathidium bromelicola from life (a–d, j–l) and after protargol impregnation (e–i, m, n). a – left side view of a representative specimen, length 85 µm; b – surface view, showing the minute (≤ 1 µm) cortical granules arranged in oblique rows; c – the oral bulge is distinctly curved in 70% of specimens; d – frontal view of a straight oral bulge studded with extrusomes; e, f – ciliary pattern of left and right side and macronucleus of holotype specimen, length 85 µm; note the Arcuospathidium ciliary pattern on the left side (e), i.e., the ciliary rows do not curve ventrally anteriorly; g–i – shape variability of oral bulge, respectively, circumoral kinety; j – mature extrusomes are rodshaped and about 4 µm long; k, l – overview and detail of resting cyst in optical section. Note the conspicuous, pillar-shaped lepidosomes most frayed anteriorly; m, n – length comparison of trophont and theront. BU – oral bulge, B(1–3) – dorsal brush (rows), CK – circumoral kinety, CV – contractile vacuole, E – extrusomes, EL – external layer, EP – excretory pore, FV – food vacuoles, G – cortical granulation, IL – internal layer, L – lipid droplet, MA – macronucleus, MI – micronucleus, SL – slime layer, T – anterior tail of dorsal brush rows. Scale bars: 2.5 µm (l), 15 µm (h, k), 20 µm (g, i), and 40 µm (a, e, f, m, n).

Figs 2a–m. Arcuospathidium bromelicola from life. a, b – left side and ventral view, showing body outline of a specimen with strongly convex oral bulge (arrowheads); c – oral bulge extrusomes (some marked by arrowheads) are rod shaped and about 4 × 0.3 µm in size; d – a pillar of a squashed cyst; e – bright field micrograph of a resting cyst in optical section, showing the thin external layer (arrow) and thick internal layer (opposed arrowheads); f–h – optical section of cyst pillars, showing the variability of the distal end; i, j – optical section and surface view, showing the narrowly spaced pillars; k – arrowheads mark overturned pillars in a squashed cyst; l, m – optical sections, showing the cysts filled with lipid droplets and surrounded by a narrow slime layer. CV – contractile vacuole, L – lipid droplets, MA – mac- ronucleus, SL – slime layer. Scale bars: 2.5 µm (f–h), 10 µm (c), 15 µm (e, i, j, l, m), and 40 µm (a, b).

Figs 3a–k. Arcuospathidium bromelicola after protargol impregnation. a, b – left and right side view of a representative specimen; c, d – ventral and dorsal view of anterior body region, showing the cuneate, slightly curved circumoral kinety and the dorsal brush; e – left side view, showing the heterostichad dorsal brush with end of row 3 marked by an arrowhead; f – a horseshoe-shaped macronucleus accompanied by an ellipsoidal micronucleus with a minute, hemispherical cap; g–i – specimens with distinctly curved oral bulge, respectively, circumoral kinety;j – post-conjugant with two macronuclear nodules; k – a trophont with two large food vacuoles which contain ciliates and dislocate the macronucleus. BU – oral bulge, B(1–3) – dorsal brush (rows), CK – circumoral kinety, E – extrusomes, MA – macronucleus, MI – micronucleus. Scale bars: 10 µm (e, f), 15 µm (c, d, g, h), 30 µm (k), and 40 µm (a, b, i, j).