Chaenea paucistriata, Fan & Xu & Gu & Li & Al-Farraj & Al-Rasheid & Hu, 2015

Fan, Xinpeng, Xu, Yuan, Gu, Fukang, Li, Jiqiu, Al-Farraj, Saleh A., Al-Rasheid, Khaled A. S. & Hu, Xiaozhong, 2015, Morphology of Two Novel Species of Chaenea (Ciliophora, Litostomatea): Chaenea paucistriata spec. nov. and C. sinica spec. nov., Acta Protozoologica 54 (2), pp. 97-106 : 98-102

Chaenea paucistriata spec. nov. ( Figs 1 , 2 ; Table 1)

Diagnosis: Extended cell size in vivo usually about 220 × 18 µm. Eight somatic kineties. Dorsal brush rows 1–4 consisting of three, five, seven and two dikinetids, respectively. About 63–94 macronuclei. Cortical granules minute and colourless.

Type locality: Coastal water of Daya Bay (22°42′N, 114°32′E), China .

Type material: A protargol slide containing the holotype specimen marked with an ink circle is deposited in the Laboratory of Protozoology , Ocean University of China (Registry no. FXP2007122006) .

Etymology: The species group name is a composite of the Latin prefix pauci (“few”), and the Latin adjective striatus, -a, -um [m, f, n] (“striated”), which reflects the fact that this species possesses fewer somatic kineties than its congeners.

Gene sequence data: The small subunit rRNA gene sequence of Chaenea paucistriata spec. nov. was deposited in GenBank with accession number FJ876970 ( Zhang et al. 2012).

Description: Extended cells measuring about 180– 250 × 15–25 µm in vivo, with a length: width ratio of about 12–14:1; narrowly flask-shaped; cell very flexible and contractile; when contracted, cell measuring about 100–180 × 20–30 µm, with ratio of length to width about 4–7:1 ( Figs 1A, D , 2A–C, H, I ). Anterior portion of body distinctly narrowed, with an inconspicuous head; posterior part tapering to rounded ( Figs 1A, D , 2A–C, H, I ). Oral bulge, ca. 2 × 6 µm, on top of anterior body end, forming a short snout and usually bent ( Figs 1A, B, D , 2A, D, H, I ). 63–94 ellipsoid macronuclei, with size about 2–5 × 1–2 µm, scattered in the whole cell except for the anterior and posterior portion ( Figs 1G , 2O ). Single contractile vacuole located at the posterior end ( Figs 1A, D , 2A–C, H, I ). Extrusomes rod-like, about 8 µm long, usually in batches attached to oral bulge and scattered in cell ( Figs 1A, B, G , 2E, F, K ). Cortex flexible, and furrowed by somatic kineties ( Fig. 2G ). Cell colour brownish in middle of body due to packed food vacuoles and cytoplasmic granules, while anterior portion and posterior end transparent ( Figs 2A–C ). Fine cortical granules colourless, with diameter less than 0.5 µm, distributed between somatic kineties ( Fig. 2J ). Cytoplasmic granules ellipsoid or round, with diameter about 2–5 µm ( Figs 2E, F, K ). Movement by slowly crawling on bottom of Petri dish. Typically, whole of somatic kineties consist of monokinetids ( Figs 1E, F , 2L–N, P ). Cilia about 7–8 µm long and arranged in longitudinal rows, although these become spiral in form in contracted specimens ( Figs 1E, F , 2P ). Consistently, eight somatic kineties, each of which consists of six or seven narrowly spaced oralized somatic monokinetids and 60–89 ordinarily spaced somatic monokinetids ( Figs 1E, F , 2L, P ). Four dorsal brush rows consistently comprising three, five, seven and two dikinetids respectively (number of specimens = 15) ( Figs 1C, F , 2M, N ). Cilia of dorsal brush about 3–4 µm long.

Oral bulge inconspicuous after protargol staining ( Fig. 2L, M, P ). Circumoral kinety inconspicuous and composed of dikinetids which are at the anterior end of each somatic kinety ( Figs 1C, E, F , 2L, M, P ).

Comparison: Considering the general morphology in terms of body length and the number of macronuclei, five species should be compared with Chaenea paucistriata spec. nov., namely C. teres , C. vorax , C. simulans , C. stricta and an unidentified Chaenea species from Petz et al. (1995) ( Figs 3A–E, G–M ; Table 2).

Chaenea teres is similar to the new species in terms of body size, length of the extrusome and the presence of fine cortical granules; it can be distinguished, how- ever, in having more somatic kineties (12–14 vs. 8), and more dikinetids in dorsal brush row 3 (14–17 vs. 7) and 4 (5–7 vs. 2) ( Figs 3A–D ; Table 2; Petz et al. 1995).

Chaenea vorax differs from C. paucistriata in having a smaller body length (100–180 µm vs. 180–250 µm), more somatic kineties (11 or 12 vs. constantly 8) and shorter extrusomes (5–6 µm vs. 8 µm) ( Figs 3L, M ; Table 2; Song and Packroff 1997).

Chaenea simulans can be separated from the new species by having a longer body length (250–350 µm vs. 180–250 µm), more somatic kineties (12–14 vs. constantly 8) and a different habitat (brackish water with salinity 1‰ vs. marine water with salinity about 30‰) ( Fig. 3E ; Table 2; Kahl 1930).

Chaenea stricta (Dujardin, 1841) Foissner et al., 1995 can be distinguished from the new organism through its smaller body length (90–130 µm vs. 180– 250 µm), greater number of somatic kineties (11 or 12 vs. constantly 8), and different habitat (freshwater vs. marine water) ( Figs 3I–K ; Table 2; Foissner et al. 1995).

Although in vivo characteristics of Chaenea sp. sensu Petz et al., 1995 are not available, it differs from the new species in having more somatic kineties (16–20 vs. constantly 8), and longer extrusomes (12–15 µm vs. ca. 8 µm) ( Figs 3G, H ; Table 2; Petz et al. 1995).

Figures

Figs 1A–G. Chaenea paucistriata spec. nov. in vivo (A, B, D) and after staining with protargol (C, E–G). A – a naturally extended individual, noting rod-shaped extrusomes scattered in cell; B – anterior body end to show oral bulge and the extrusomes attached to it; C – ciliary pattern of anterior end marking circumoral kinety and dorsal brush rows 1–4; D – a contracted individual, noting oral bulge, food vacuole and contractile vacuole; E, F – ciliary pattern of ventral (E) and dorsal (F) side of holotype specimen, indicating the circumoral kinety, dorsal brush rows 1–4, and somatic kineties; G – distribution of macronuclei and extrusomes. B1–4 – dorsal brush rows 1–4, CK – circumoral kinety, CV – contractile vacuole, E – extrusomes, FV – food vacuole, Ma – macronuclei, OB – oral bulge, SK – somatic kinety. Scale bars: 50 µm.

Figs 2A–P. Chaenea paucistriata spec. nov. in vivo (A–K) and after protargol impregnation (L–P). A–C – different body shapes; D – anterior body end to show the oral bulge; E, F – fine structure of anterior end to show rod-shaped extrusomes, arrowhead indicating cilia of the dorsal brush; G – dividing cell, showing cortical furrows along somatic kineties; H, I – typical individual, indicating contractile vacuole; J – cortical granules between somatic kineties (arrowheads); K – fine structure of the mid-body to show cytoplasmic granules and rodshaped extrusomes (arrowheads); L–N – ciliary pattern of anterior body end, showing circumoral kinety narrowly spaces oralized somatic monokinetids (arrowheads), and dorsal brush rows 1–4; O – ciliary pattern in mid-body and many scattered macronuclei; P – overview showing circumoral kinety and somatic kineties. B1–4 – dorsal brush rows 1–4, CK – circumoral kinety, CV – contractile vacuole, E – extrusomes, Ma – macronuclei, OB – oral bulge, SK – somatic kinety. Scale bars: 90 µm (A–C, H, I), 70 µm (P).

Figs 3A–M. Morphology of some closely-related congeners of Chaenea paucistriata spec. nov. and Chaenea sinica spec. nov. A–D – C. teres (from Petz et al., 1995), general view of living cell (A), overview of ciliary pattern (B), detail of ciliary pattern in anterior body end (C), surface view showing cortical granulation (D); E – C. simulans (from Kahl, 1930); F – C. robusta (from Kahl, 1930) G, H – Chaenea sp. (from Petz et al., 1995), detail of ciliary pattern in anterior body (G), overview of ciliary pattern (H); I–K – C. stricta (from Foissner, 1984), detail of ciliary pattern in anterior body (I), general view (J), overview of ciliary pattern (K); L, M – C. vorax (from Song and Packroff, 1997), general view (L), overview of ciliary pattern (M). B – dorsal brush, B1–4 – dorsal brush rows 1–4, CG – cortical granules, CK – circumoral kinety, CV – contractile vacuole, E – extrusomes, Ma – macronuclei, OB – oral bulge, SK – somatic kinety. Scale bars: 100 µm (A, H, L), 50 µm (B, J, K, M), 150 µm (E, F).