Tintinnopsis uruguayensis Balech, 1948

Jung, Ji Hye Moon and Jae-Ho, 2025, Morphology and molecular phylogeny of controversial tintinnids Tintinnopsis fimbriata and T. uruguayensis (Protozoa: Ciliophora) collected from coastal waters of South Korea, Journal of Species Research 14 (1), pp. 86-95 : 91-94

Tintinnopsis uruguayensis Balech, 1948

( Table 1, Figs. 3-5 ) ǭêḝẖŀflệ (ṵḡ)

Tintinnopsis uruguayensis Balech, 1948: 14 , pl. 5, figs. 64-68; Bai et al., 2020: 10-12, figs. 5, 6.

Material examined. Marine water, collected from near Janghang Port , Janghang-eup, Seocheon-gun, Chungcheongnam-do, Republic of Korea (36°0 ʹ 26.6 ʺ N, 126°41 ʹ 51.9 ʺ E) on 17 Aug 2021 .

Description (n = 15). Lorica 52-61 × 23-29 μm (on average 56.4 × 26.5 μm) in size, agglutinated, composed of obconical collar and ellipsoidal bowl with cylindrical posterior process ( Figs. 3A- G , 4A- G ). Collar 8.5-12.0 μm (on average 10.0 μm) high, crown-shaped, with irregular rim; inner constriction diameter 18-21 μm (on average 19.4 μm). Ratio of lorica length to opening of collar diameter 1.9-2.7: 1 (on average 2.2: 1). Bowl occupies about 62.3% of lorica length, 23-25 μm (on average 23.8 μm) in diameter; end of bowl 47-86° (on average 69.7°) angle ( Figs. 3A , 4A- C ). Posterior process 9-15 × 5.5-8.5 μm (on average 11.5× 6.7 μm) in size, with usually obliquely truncate open end ( Figs. 3A, B , 4A- C, F ). Closing apparatus present, agglutinated with small particles ( Figs. 3B , 4B- D, E, G ).

Habitat. Marine.

Distribution. Atlántida in Uruguay ( Balech, 1948), Fort Pierce and Long Island Sound in the United States of America ( Strüder-Kypke and Lynn, 2008; Santoferrara et al., 2013), coastal waters of Qingdao in China ( Bai et al., 2020), and Janghang Port in Korea (present study).

Phylogenetic analyses. The SSU rDNA- ITS1- 5.8S rDNA- ITS2-partial LSU rDNA sequence of Tintinnopsis uruguayensis is 2,318 base pairs long with a GC content of 46.8% (GenBank accession no: PQ650934). The SSU rDNA sequence of T. uruguayensis shows an identity of 99.86% (two nucleotide differences) to the two American populations ( EU399542 , JN831838 ) and the Chinese population ( MT435075 ) of T. uruguayensis , and the Korean population of T. fimbriata ( Fig. 5 ). Besides, the ITS1- 5.8S rDNA- ITS2 sequence of the Korean T. uruguayensis shows an identity of 99.29% (three nucleotide differences) to the Chinese population ( MT435062 ).

Remarks. The Korean population of Tintinnopsis uruguayensis very closely resembles the type population as for lorica morphology (lorica size: 52-61 × 23-29 μm vs. 54-63 × 22-27 μm; inner constriction diameter: 18-21 μm vs. 19-21 μm; bowl width: 23-25 μm vs. 23-26 μm) ( Balech, 1948). In contrast, the Korean population differs from the American and Chinese populations of T. uruguayensis in terms of lorica morphology and molecular phylogeny ( Table 1; Fig. 5 ): larger loricae in American populations (70-80 × 40-50 μm and 64 × 34 μm vs. 52-61 × 23- 29 μm) ( Strüder-Kypke and Lynn, 2008; Santoferrara et al., 2013); broader loricae in Chinese population (lorica length:collar opening diameter, 1.6-2.3 vs. 1.9-2.7) ( Bai et al., 2020). As mentioned above, the American and Chinese populations share the same SSU rDNA sequences and differ by two nucleotides from the Korean population. Considering that the ITS1- 5.8S rDNA- ITS2 sequence of the Chinese population differs by three nucleotides from that of the Korean population, it could represent a distinct species ( Jung et al., 2018).

Among congeners, Tintinnopsis amoyensis exhibits a shape similar to that of T. uruguayensis due to an obconical collar and a cylindrical posterior process. However, they differ in lorica length (45-50 μm vs. 52-61 μm) ( Nie, 1934). Tintinnopsis cylindrica and T. tocantinensis have a posterior process, but they lack an obconical collar and their loricae are longer than that of T. uruguayensis ( Daday, 1887; Kofoid and Campbell, 1929).

Voucher specimens. The three slides were deposited at the National Marine Biodiversity Institute of Korea ( MABIK PR00045097- MABIK PR00045099).

Figures

Fig. 3. Tintinnopsis uruguayensis from a Bouin’s fluid-fixed sample. A, C-G, Lateral views of the loricae; B, Optical section of the middle of the cell inside the lorica, arrow showing the closure of the closing apparatus. The same scale is applied for comparison of size variation (A, B; C-E; F, G). Scale bars:A, C, F=30 μm.

Fig. 4. Tintinnopsis uruguayensis, isolated from a Bouin’s fluid-fixed sample, under a scanning electron microscope.A-C, Lateral views of the loricae; D, E, Anterior ends of the loricae, arrowhead indicating the closure of the closing apparatus, arrow showing the possibility of the presence of an agglutinated lorica sac; F, Posterior end of the posterior process; G, Smooth inner surface of the closing appartus. The same scale is applied for comparison of size variation(A-C). Scale bars: A=30μm, D=20μm, E=5 μm, F=2 μm, G =1 μm.

Fig. 5. Bayesian inference(BI) tree based on SSU rDNA sequences, showing the phylogenetic position of Tintinnopsis fimbriata and T. uruguayensis. Newly obtained sequences are in bold. GenBank accession numbers follow species names. Numbers at the nodes represent the Bayesian inference (BI) posterior probabilities and the maximum likelihood (ML) bootstrap values (solid circles=full supporting values). Dashes indicate posterior probabilities<0.5, bootstrap values<50%, or different topologies in BI and ML phylogenies. The scale bar represents three nucleotide substitutions per 100 nucleotides.