Parametacystis pulchra, Jiang & Wang & Liao & Al-Farraj & Warren & Hu, 2024

Jiang, Limin, Wang, Congcong, Liao, Lijian, Al-Farraj, Saleh A., Warren, Alan & Hu, Xiaozhong, 2024, Re-evaluation of the systematic position of the order Prostomatida (Protista: Ciliophora), with the establishment of two new genera and two new species, Zoological Journal of the Linnean Society 200 (4), pp. 849-864 : 854-855

Parametacystis pulchra gen. nov., sp. nov.

( Fig. 4 ; Table 1 )

Zoobank registration: urn:lsid:zoobank.org:act:1F7796F3-5ABA-4955-AD9A-B3A9BF7D4030

Diagnosis: Cell cylindrical, 40–75 μm × 15–25 μm in vivo; without lorica or caudal cilium; ‘head’ region present; single globular to ellipsoidal macronucleus and single ellipsoidal micronucleus; cortical granules spherical and colourless; circumoral kinety composed of 7–10 dikinetids, forming a semi-circle; perioral kineties forming six transverse monokinetidal rings; 24–32 monokinetidal longitudinal somatic kineties, kinetids of which form 20–36 transverse rings.

Type locality: Intertidal zone of Yellow Sea coast near Zhanqiao Pier, Qingdao (36°04ʹ03″N, 120°19ʹ35″E), Shandong Province, China. The salinity was 31‰ and the water temperature 10°C .

Type specimens: A protargol slide containing the holotype specimen (registration number: JLM2021112901-1; Fig. 4B, C ) was deposited in the Laboratory of Protozoology , Ocean University of China. A second protargol slide (registration number: JLM2021112901-2) containing paratype specimens was deposited in the Marine Biological Museum , Chinese Academy of Sciences, Qingdao .

Etymology: The species-group name pulchra (Latin feminine of pulcher = beautiful) refers to its beautiful shape.

Description: Cell size in vivo ~40–75 μm × ~15–25 μm, on average 60 μm × 20 μm, with a length-to-width ratio of 2–4:1 ( Fig. 4A, F, G ). Body flexible and slightly contractile, almost cylindrical but progressively narrowed from middle to both ends ( Fig. 4A, F, G ). Oral bulge rather conspicuous and distinctly projecting from body; without oral basket or nematodesmata; cytostome central and apical, inconspicuous ( Fig. 4A, F, G ). Posterior end of body truncated owing to presence of a large, non-contractile caudal vacuole, ~5–9 μm in diameter ( Fig. 4A, F, G ). Ectoplasm with distinct transverse furrows ( Fig. 4A, F, G ). Network of furrows extends over entire body surface, consisting of regular rectangles (one between adjacent kineties), which is likely to be the silverline system ( Fig. 4D, H ). Cortical granules spherical, colourless, ~0.5–0.6 μm in diameter, arranged regularly along somatic kineties ( Fig. 4D, H ). Cytoplasm colourless, usually containing several ellipsoidal or globular granules ( Fig. 4A, F–H ). One macronucleus, globular or slightly ellipsoidal in shape, ~6–8 μm × 5–8 μm after protargol staining, located slightly above mid-region of cell; one micronucleus, ellipsoidal, ~3 × 2 μm after protargol staining, located in a small groove adjacent to macronucleus ( Fig. 4A, J ). No contractile vacuole observed. Locomotion by swimming moderately fast in upper layer of water, with anterior end swinging from side to side.

Most somatic cilia ~6–7 μm long; perioral cilia well developed and ~9–10 μm long ( Fig. 4A, F, G ). Somatic ciliature composed of 24–32 longitudinal monokinetidal kineties regularly disposed around the body; kinetids form 26–42 uniformly spaced transverse rings ( Fig. 4B, C, I ). Perioral kineties more closely spaced than other somatic kineties, located between circumoral kinety and other somatic kineties, consisting of six transverse monokinetidal rings ( Fig. 4B, C, E, K, L ). Other somatic kinetids form 20–36 transverse rings. Circumoral kinety incomplete, composed of 7–10 dikinetids that form a semi-circle ( Fig. 4B, C, E, K, L ).

Figures

Figure 4. Drawing (A–E) and photomicrographs (F–L) of Parametacystis pulchra gen. nov., sp. nov.from life (A, D, F–H) and after protargol staining (B, C, E, I–L). A, lateral view of a representative individual, showing general appearance of body and protruding caudal vacuole (arrow). B, C, side view of the holotype specimen, showing ciliary pattern of the cell and circumoral kinety (arrowheads).D, showing the pattern of the silverline system and cortical granules. E, ciliary pattern of the anterior portion of the cell, showing the circumoral kinety (CK) and the perioral kineties (PK). F, showing the protruding caudal vacuole (arrow). G, lateral view of a slightly contracted individual, showing the furrows in ectoplasm (arrowheads). H, compressed individual, showing the pattern of the silverline system and cortical granules (arrows). I, lateral view of holotype specimen, showing ciliary pattern and macronucleus (Ma). J, showing the macronucleus and micronucleus (arrow). K, L, showing the circumoral kinety (arrowheads) and perioral kineties (arrows). Scale bars: 20 μm.