Chlamydonella wangi, Wang & Jiang & Pan & Warren & Hu, 2025

Chlamydonella wangi sp. nov.

( Figs 4, 5; Table 2)

ZooBank registration number of new species: urn:lsid:zoobank.org:act:

Diagnosis: Marine Chlamydonella 40–65 µm × 25–45 μm in vivo; body reniform, with a protrusive structure in anterior lef region; ~15 small finger-like tentacles on ventral side; four or five contractile vacuoles; 17–19 somatic kineties, including four frontoventral kineties; equatorial fragments present at both lef and right margins; single terminal fragment consisting of ~15 basal bodies; 20–27 nematodesmal rods; single ellipsoidal macronucleus.

Type locality: Sandy beach at Wanpingkou Scenic Spot, Rizhao, northern China ( 35°24′30″N, 119°33′59″E) GoogleMaps .

Type deposition: A protargol slide (registration number: WCC2021112401-1), with the holotype specimen circled with black ink, is deposited in the Marine Biological Museum, Chinese Academy of Sciences , Qingdao. A second protargol slide (registration number: WCC2021112401-2) with paratype specimens is deposited in the Laboratory of Systematic Taxonomy , Ocean University of China, Qingdao .

Dedication: Te species name is dedicated to the Chinese protozoologist Professor Dr Jiaji Wang, in recognition of his significant contributions to the taxonomy of ciliates.

Morphological description: Cell 55–65 µm × 30–45 μm in vivo ( N = 4), ~50 µm × 30 μm afer protargol staining, ratio of length to width ~1.6:1 ( Table 2). Body reniform, with a distinct rostriform projection on anterior lef when viewed from ventral aspect ( Figs 4A, B, 5A). Right margin distinctly convex; lef margin straight or slightly concave. Both ends rounded. Ventral side flatened; dorsal side conspicuously vaulted ( Figs 4A–C, 5A, J). Fine stripes densely arranged on dorsal surface ( Fig. 5J). About 15 small finger-like tentacles, 3–4 μm long, distributed on ventral side in two rows ( Figs 4A, 5C).

Cytoplasm colourless and hyaline, central portion slightly greyish with numerous different-sized granules ( Figs 4A, 5A, B). Food vacuoles ofen filled with yellow–green algae ( Fig. 5E). Numerous dark grey cortical particles (~.5 μm across) regularly distributed on dorsal surface ( Fig. 5D). Cytostome prominent, 6–10 μm wide, sub-apically located; cytopharynx extending backwards to middle of body, including 20–27 toothed nematodesmal rods, ~15 μm in length ( Fig. 5A, B, F, H). Four or five contractile vacuoles located at anterior 25% and posterior 20% of cell length, respectively, 4 μm in diameter, each with a contraction interval of ~15 s ( Figs 4A, B, 5B). Macronucleus ellipsoidal, heteromerous, centrally positioned, ~17 µm × 12 μm in vivo and afer protargol staining ( Figs 4E, 5B, I). Micronucleus not detected. Locomotion by slowly gliding or by swimming while rotating about ventral longitudinal axis.

Cilia ~8 μm long in vivo, mainly arranged on ventral surface. Between 17 and 19 somatic kineties, rightmost four extending apically to form frontoventral kineties, with anterior portion curved to left, inner two rows bisected by perioral kineties ( Figs 4D, E, 5G, K). All other kineties terminating anteriorly at about cytostome level. Basal bodies densely spaced in posterior end of some somatic kineties ( Figs 4E, 5G). Left equatorial fragment composed of 2–20 basal bodies; right equatorial fragment consisting of 1–13 basal bodies ( Figs 4E, 5G). One terminal fragment consisting of ~15 basal bodies, positioned on dorsal margin of cell ( Figs 4C, 5J).

Oral structure typical of genus, namely perioral kineties Y-shaped. In addition to these ‘normal’ kineties, there are two fragments of five to eight basal bodies near perioral kineties ( Figs 4D, E, 5G, K). A row of kinetosome-like structures encircles cyrtos ( Fig. 5K).

Gene sequences and phylogenetic analyses

A total of 22 new lynchellid sequences, including those of the two new species investigated in the present study, have been deposited in the GenBank database. Teir GenBank accession numbers are shown in Table 3.

Paracoeloperix composita has the highest SSU rDNA sequence identity with Coeloperix sinica ( FJ998034 View Materials ), i.e. 87.1% (170 mismatches and 34 gaps). Chlamydonella wangi is most similar to Chlamydonellopsis calkinsi ( KC753487 View Materials ) in terms of SSU rDNA sequence (97.4% similarity, 37 mismatches and four gaps) (Supporting Information, Table S2).

We performed phylogenetic analyses based on the SSU rDNA, LSU rDNA, and ITS1– 5.8S rDNA–ITS2 sequence alignments. Te topologies of the BI and ML trees are almost identical, hence only the ML trees are presented here, with support values from both algorithms indicated on branches. Te results show that all the newly sequenced species cluster within the family Lynchellidae .

In the SSU rDNA tree, Lynchellidae are recovered as monophyletic with medium support and cluster with the family Pithitidae to form the basal clade of Cyrtophoria. Species within Lynchellidae are divided into two moderately supported clades. Clade I comprises the genera Chlamydonella , Chlamydonellopsis , and Atopochilodon , with Atopochilodon distichum occupying the basal position. With the addition of Chlamydonella wangi , neither Chlamydonella nor Chlamydonellopsis is monophyletic, although the approximately unbiased (AU) test did not reject their monophyly ( Table 4). Species of the genera Coeloperix , Paracoeloperix , and Lynchella form clade II, and Paracoeloperix occupies the basal position with moderate support.

Although the number of LSU rDNA sequences is relatively small, the topology of the LSU rDNA tree is basically the same as that of the SSU rDNA tree, e.g. Lynchellidae are monophyletic, and Paracoeloperix clusters with Lynchella and Coeloperix . In contrast, the topology of the ITS1– 5.8S rDNA–ITS2 tree differs significantly from that of the other two gene trees; for example, Atopochilodon distichum does not nest within the Lynchellidae assemblage. Furthermore, most clades in the ITS1– 5.8S rDNA– ITS2 tree have low support values, indicating that this topology is unstable (Supporting Information, Fig. S1).

Neighbour-joining network analyses

Te networks of three nuclear markers were constructed for 12 populations of lynchellids.All species could be separated clearly by SSU rDNA, ITS1– 5.8S rDNA–ITS2, and LSU rDNA sequences, and no two species share identical sequences. Similar to the ML and BI trees, species or genera with the same characteristics tend to group closer together and are separated by fewer steps. Te length of the SSU rDNA ranges from 1571 bp in Coeloperix sleighi to 1588 bp in Atopochilodon distichum and Chlamydonellopsis calkinsi , and lynchellids diverged from each other by as many as 25–238 steps ( Fig. 6A). Te amplified LSU rDNA sequences are much more variable in length than the SSU rDNA sequences, and the between-species divergence ranges from 92 to 365 steps ( Fig. 6C). Te amplified region of the ITS1– 5.8S rDNA–ITS2 ranges from 396 bp in Chlamydonellopsis calkinsi to 501 bp in Lynchella nordica , which is shorter than the SSU rDNA and LSU rDNA but equally highly variable ( Fig. 6B). Paracoeloperix composita is widely separated from the other species, sharing ≥172 steps with its closest species in the SSU rDNA-based network. Chlamydonella wangi is always close to its congeners and Chlamydonellopsis calkinsi . Similar findings were revealed in the LSU rDNA and ITS1– 5.8S rDNA–ITS2 networks.