Ancyromonas micra ( Cavalier-Smith, 2008 )

Park, Dong Hyuk Jeong and Jong Soo, 2021, Characterizations of five heterotrophic nanoflagellates newly recorded in Korea, Journal of Species Research 10 (4), pp. 356-363 : 361-362

5. Ancyromonas micra ( Cavalier-Smith, 2008)

Heiss et al., 2010 ( Fig. 4A, B )

Synonym: Planomonas micra Cavalier-Smith, 2008 .

Isolation. Dong Hyuk Jeong and Jong Soo Park conducted specimen collection on 16 March 2021, from the Ilgwang Beach (35°19′12.06″N, 129°15′57.08″E), Busan, Korea. Temperature : 17.7℃, Salinity : 34.0 PSU, pH: 8.3. Morphological description. The live strain IG005 was oval and flatten-shaped ( Fig. 4A, B ). Also, the average length and width of the cell body were 4.9±1.2 μm (mean± STD) and 3.5±0.6 μm, respectively (n = 20). Cells had a shallow groove in the body’s anterior and a reflected rostrum between the flagellum ( Fig. 4A ) Cells displayed gliding movement, and the two flagella showed acronematic form. The average length of the anterior and posterior flagellum was 3.6±0.6 μm and 8.6±1.6 μm, respectively (n = 20). The anterior flagellum swayed from side to side, while the posterior flagellum trailed posteriorly .

Molecular phylogeny. The partial 18S rDNA sequence of the strain IG005 was 1,689 bp long (G + C content: 42%). The 18S rDNA sequence of strain IG005 was 99.88% (1688/1690 bp), which was identical to that of Ancyromonas micra (formerly Planomonas micra ATCC 50267, accession number; EF455780, 1,753 bp long, G + C content: 43%), suggesting identical species. The ML tree revealed that the strain IG005, two A. micra strains Millport and ATCC50267, Planomonas elongata (JQ340 332), and P. bulbosa (JQ340333), formed a clade with a moderate bootstrap value (ML: 72%) and a posterior probability of 0.78 ( Fig. 4C ).

Remarks. The strain IG005 resembled the original cells, which were a flat disc-shaped ( Cavalier-Smith et al., 2008). The cell body of the original cells was about 4 μm in length, which is slightly shorter than our isolate. Also, the ventral surface behind the flagellar pocket of the original cells showed a concave depression. A broad and curved snout projected between the flagellum. Those features are also examined in the strain IG005. Contractile vacuole and cysts of the original cells were also absent. Like the strain IG005, the original cells displayed a slowly gliding motility. The anterior flagellum beats stiffly, while the posterior flagellum displayed a gliding motion on the substrata. Furthermore, the anterior flagellum was usually shorter than the cell body. The flagellar length and motion, and moving behavior of the cells are consistent with the original cells. It is likely that 18S rDNA sequence of the strain IG005 formed a clade with Ancyromonas micra strains Millport and ATCC50267, Planomonas elongata , and Planomonas bulbosa , although the statistical supports were moderate. Moreover, the 18S rDNA sequence of the strain IG005 was closest to A. micra strains ATCC50267 and Millport (99.88%), rather than P. elongata (99.70%) and P. bulbosa (99.53%). In fact, A. micra , P. elongata , and P. bulbosa were morphologically similar to each other ( Glücksman et al., 2013). However, the length of the posterior flagellum of P. elongata (11-13 μm) was longer than A. micra including our isolate. P. bulbosa had more bulbous rostrum than A. micra strains. Thus, we did not exclude the possibility that our isolate is identical to previous A. micra . However, further sequencing of various genes is needed to assess the monophyletic relationship of A. micra , P. elongata , and P. bulbosa .

Habitat. Surface water/sediment interface of coastal areas. Specimen deposition. National Institute of Biological Resources, Korea (KPZXPR0000000027-KPZXPR0000 000031).

Identifiers. Dong Hyuk Jeong and Jong Soo Park.

Figures

Fig. 4. (A, B) General light micrographs and sketch of Ancyromonas micra strain IG005. AF: anterior flagellum, PF: posterior flagellum, scale bar=5 μm. Arrowhead and double arrowhead represent a shallow groove and rostrum, respectively. All micrographs are differential interference contrast (DIC) images. (C) Maximum likelihood phylogenetic tree inferred from the 18S rDNA sequences of Ancyromonadida (order) species including Ancyromonas micra strain IG005 and outgroup (Diacronema vlkiauum strain AC67 and Prymnesium patelliferum). Bootstrap support values (>70%) are shown at the nodes. Solid circles indicate a Bayesian posterior probability of 1(posterior probability <0.75 not shown).