Cothurnia, Ehrenberg, 1832

Neuhaus, Birger, Lu, Borong, Yamasaki, Hiroshi & González-Casarrubios, Alberto, 2023, Epibiontic life on intertidal Setaphyes kielensis and S. dentatus (Kinorhyncha, Pycnophyidae) from Sylt, North Sea, Germany, with a description of a new species of Trematosoma (Ciliophora, Acinetidae) and a redescription of Cothurnia buetschlii (Ciliophora, Vaginicolidae), Zootaxa 5343 (5), pp. 439-470 : 465-466

Cothurnia

Diagnostic characters of Cothurnia buetschlii . Zelinka (1914, p. 680–682) described Cothurnia buetschlii inadvertently as a new species by mentioning several morphological characters and providing measurements for the lorica (53 µm x 21 µm) and stalk (length 10 µm). In his monograph, Zelinka (1928, pp. 194, 195, text figs 37a, b, figs 9, 10 in pl. 7, fig. 8 in pl. 14) provided much more detailed information about the epibiont: He found up to 10 or more specimens of C. buetschlii on adult but also on juvenile specimens of Pycnophyes communis and other, unnamed species of Kinorhyncha, mainly on the ventral side of the trunk or on the lateral terminal spines. The lorica (53.1 µm x 21 µm, 19.2 µm at aperture) appeared recessed on two opposing sites. The stalk (8.5–12.6 µm x 5.3 µm) showed an internal longitudinal striation and a striated endostyle ( Zelinka 1928, text fig. 37a; the very weak striation is only recognisable in the original book but not necessarily in xerocopies). The contracted zooid reached a length of 27.7 µm. The macronucleus was C-shaped and extended in longitudinal direction ( Zelinka 1928, text figs 37a) but was mentioned by Zelinka (1928, p. 197) as “quergestellt” (= transversely oriented). Measurement data of the inadvertent original description ( Zelinka 1928) differed slightly from those of his intended species description ( Zelinka 1928), the latter being more precise, and also from those given by Warren and Paynter (1991, pp. 21, 22, 29, figs 47, 48: lorica 53.2 µm x 27 µm, stalk 10 µm x 4 µm). Their descriptive text disagreed from their identification key in that the mesostyle was stated to be absent and an endostyle to be present, whereas the identification key stated the opposite. The latter was erroneous, because it did not agree with Zelinka’s (1928) description and with our observations.

All observations of Zelinka (1914, 1928) were based on living specimens of C. buetschlii , but the zooids never raised above the lorica, so not all characters became available for study. Our preserved specimens of C. buetschlii agreed with Zelinka’s (1914, 1928) descriptions in the sizes of the lorica, stalk, and length of the zooid ( Table 6 ), the shape of the lorica with two opposite recessed anterior sides ( Figs 7 , 8 ), the existence of an endostyle, the longitudinal striae in both the stalk and endostyle ( Figs 6 , 9D–F ), and the longitudinal, C-shaped macronucleus ( Figs 6 , 9E–G ). Our observations of a weak surface annulation of the zooid ( Figs 6 , 9C ) was not reported by Zelinka (1914, 1928) but may have been overlooked by him.

Referrence to C. buetschlii in the literature was rare. Besides the review of species of Cothurnia by Warren and Paynter (1991), Kahl (1933, p. 138) mentioned C. buetschlii briefly and erroneously cited the species as C. buetschlii Zelinka, 1885 . It remains a bit mysterious why Kahl claimed that one of the broader sides of a specimen would be longer than the opposite side and would cover elastically the opening ( Kahl 1935, p. 780, fig. 143.35–35a). This was not reported by Zelinka (1914, 1928) at all and could not be confirmed by us as well. To our knowledge C. buetschlii has not been mentioned otherwise and was not redescribed, yet.

Species of Cothurnia at Sylt, North Sea. Küsters (1974) reported 11 species of Vaginicolidae collected at Königshafen in the northern part of Sylt in 1969 and 1970 from experimentally exposed artificial substrates, viz, Cyclodonta bipartita ( Stokes, 1885) Matthes, 1958 , Cothurnia angusta Kahl, 1933 , C. ceramicola Kahl, 1933 , C. coarctata Kahl, 1933 , C. curvula (Entz, 1876) Entz, 1884 , C. cypridicola Kahl, 1933 , C. innata O.F. Müller, 1786 , C. inflata Stokes, 1893 , C. maritima Ehrenberg, 1838 , C. nodosa Claparède & Lachmann, 1858 , and C. pedunculata Dons, 1918 . We did not find any of these species of Cothurnia on our kinorhynch specimens of Setaphyes kielensis collected at Königshafen in 1998 or on S. dentatus and S. kielensis collected at Kampen in 1988 and 2016 but a different species, viz, C. buetschlii ( Tables 3 , 4 ).

Distribution of Cothurnia buetschlii on Kinorhyncha in European waters. Zelinka (1928) reported C. buetschlii from Pycnophyes communis and also from similar species of Kinorhyncha without providing their species names. The distribution areas of the basibiont P. communis and of the here reported Setaphyes dentatus and S. kielensis overlap widely ( Fig. 1 ). Whereas P. communis was reported from the Skagerrak, Baltic Sea, North Sea, Irish Sea, Mediterranean Sea, and Black Sea, S. dentatus was mentioned from the Baltic Sea, North Sea, Irish Sea, Mediterranean Sea, and Black Sea, and S. kielensis showed records from the White Sea, Baltic Sea, North Sea, British Channel, and Black Sea ( Fig. 1 ; González-Casarrubios et al. 2023; Neuhaus 2023a –c). With this overlap of distribution areas it is highly likely that an exchange of epibionts between P. communis , S. dentatus , and S. kielensis would be possible.

Species of Cothurnia on different basibionts of Kinorhyncha. The literature revealed four reports of species of Cothurnia on Kinorhyncha in addition to C. buetschlii . Adrianov and Higgins (1996, fig. 23) labelled two “ectocommensal suctorians” attached ventrally to segment 1 of Pycnophyes parasanjuanensis , but these epibionts can be identifyed as a species of Cothurnia . Ostmann et al. (2012, pp. 87, 90 fig. 6) documented a species of Cothurnia from Echinoderes applicitus . The specimens in the collection of the Museum für Naturkunde Berlin revealed not too many details because of the insufficient conservation in the mounting medium Fluoromount G, but they were clearly different from C. buetschlii . Neuhaus (2013, p. 331) mentioned “sessile ciliates, possibly a species of Cothurnia , […] on Pycnophyes sp. from Florida ( Fig. 5.8.1 A, B )”. These were based on life observations and photographs. Last not least, Cepeda et al. (2022c, fig. 4H, I) provided SEM images of Leiocanthus quinquenudus with epibionts similar to C. buetschlii with respect to the general shape of the lorica but with an asymmetrical opening. The limited amount of observations does currently not allow to draw any further-reaching conclusions about infestation of Kinorhyncha by species of Cothurnia .

Figures

FIGURE 1. Map showing the locations of Pycnophyes communis, Setaphyes dentatus, and S. kielensis in European waters and the sampling site of S. dentatus and S. kielensis in the North Sea, island of Sylt (asterisks in inset A).

FIGURE 5. Setaphyes kielensis (A, ZMB 12489; B, ZMB 12500; C, ZMB 12499; D, ZMB 12487; J, ZMB 12486; L, ZMB 12397; M, ZMB 12369) and S. dentatus (E–G, K, ZMB 12503; F, H, I, ZMB 12494) with specimens of Trematosoma husselae sp. nov. (A–G, J–M), Cothurnia buetschlii (J), and a case of fungus or developmental artefact (H, I, ZMB 12494), DIC. A. Segments 1–4, lateral and dorso-ventral view on the calyciform, dorso-ventrally compressed lorica with the zooid, ventrolateral view on basibiont. B. Epibiont with swarmer, stalk, and lorica in optical section. C. Epibiont with two macronuclei not fusing at any focal level. D, E. Young, small, spherical epibionts with few tentacles, not all tentacles in focus. F. Young specimen on cuticle of basibiont with striation pattern on surface (arrows). G. Epibiont with tentacles in empty shell of suctorian epibiont. H, I. Segment 10, dorsally (H) and optical section (I), subcuticular fungus or internal sclerotisation artefact of the cuticle (arrows). J. Assemblage of epibionts on segment 10 of basibiont with C. buetschlii (contracted specimen left, extended specimen right), T. husselae sp. nov., and two kinds of filamentous bacteria. Arrows mark endostyle. K. Suctorian on segment 7 of S. dentatus. L, M. Specimens collected 1998, showing cellular substructures (L) and withdrawn zooid with minimum amount of cellular substructures (M). Extended focus images of six (D), eight (H, L), and three (K) images. Arrowheads mark stalks in B, D, E, G, and J. Abbreviations: ba, bacteria; ca, basal cavity in lorica; co, C. buetschlii; en, endostyle; lo, lorica; ma, macronucleus; s, segment, followed by segment number; sc, spherical cavity; sp, sperm; st, stalk; su, suctorian epibiont; sw, swarmer; te, tentacle; tu, tube on segment 2. Scale bar in A 50 µm, in B 20 µm, valid for B, G–J and M, in C 20 µm, valid for C, K, and L, and in D–F 10 µm.

FIGURE 6. A, B. Drawing of Cothurnia buetschlii (specimen 2) ventrally on segment 10 of Setaphyes kielensis (ZMB 12486) as longitudinal optical section (A) and lorica in cross-section (B). Abbreviations: an, annulation on surface of zooid; en, endostyle with striae; inf, withdrawn infundibulum with cilia; lo, lorica; ma, macronucleus; mi, micronucleus; po, pore in cementing mass; sc, spherical cavity; st, stalk with internal striae; zo, zooid. Scale bar 30 µm.

FIGURE 7. Setaphyes kielensis (ZMB 12468) with epibionts, SEM. A. Segments 1–11, ventral-right. B. Segments 4–8, ventral view. Arrows mark laterally recessed anterior margin of lorica of Cothurnia buetschlii. Abbreviations: co, Cothurnia buetschlii; fp, filamentous prokaryotes; lts, lateral terminal spine; s, segment, followed by segment number; se, seta; su, suctorian epibiont; tu, tube. Scale bar in A 100 µm and in B 20 µm.

FIGURE 8. Setaphyes kielensis (A, ZMB 12468; B, ZMB 12474) with epibionts, SEM. A. Segment 6, left side. Arrow marks laterally recessed anterior margin of lorica of Cothurnia buetschlii. B. Segments 8–10, dorsal view.Abbreviations: co, Cothurnia buetschlii; fp, filamentous prokaryotes; s, segment, followed by segment number; su, suctorian epibiont; te, tentacles. Scale bar in A 10 µm and in B 20 µm.

FIGURE 9. Setaphyes kielensis (ZMB 12486), segment 10 with Cothurnia buetschlii (specimens 1–4), ventral view. A. Overview of position of epibionts. Numbers indicate specimens of C. buetschlii (comp. also Table 6). B–G. Specimens 3 (B) and 4 (C–G), images 8 (C), 15 (D), 19 (E), 24 (F) and 28 (G) showing surface annulation of zooid (C, D), internal longitudinal striae of stalk and endostyle (D–F), and attachment site of stalk to the cuticle of the basibiont (G, arrowheads). Note elongate macronucleus and numerous micronuclei (E–G). White arrows (D, E) mark basal outer margin of lorica, black arrows (D, E) point to bottom margin of lorica. Abbreviations: an, annulation on surface of zooid; ci, ciliae; en, endostyle; in, withdrawn infundibulum; lo, lorica; lts, lateral terminal spine; ma, macronucleus; mi, micronucleus; ps, penile spine; sc, spherical cavity; st, stalk; su, suctorian epibiont; zo, zooid. Scale bar in A 50 µm and in D 20 µm, valid for B–G.