Trematosoma husselae, Neuhaus & Lu & Yamasaki & González-Casarrubios, 2023

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 : 445-448

publication ID	https://doi.org/ 10.11646/zootaxa.5343.5.2
publication LSID	lsid:zoobank.org:pub:2E48E826-9DB3-45C3-B231-CBB84B725119
DOI	https://doi.org/10.5281/zenodo.8345499
persistent identifier	https://treatment.plazi.org/id/F6548788-9905-FF9A-FF33-FB797164F891
treatment provided by	Plazi
scientific name	Trematosoma husselae
status	sp. nov.

Treatment

Trematosoma husselae sp. nov.

( Figs 2–5 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 , 7 View FIGURE 7 , 8 View FIGURE 8 ; Tables 1–5 View TABLE 1 View TABLE 2 View TABLE 3 View TABLE 4 View TABLE 5 , 7 View TABLE 7 )

Synonymy

Neuhaus 2013, p. 331, fig. 5.8.1D, E: Suctoria, possibly Acineta sp.

Diagnosis

Material examined

Altogether, 705 specimens of Trematosoma husselae sp. nov. were studied on its basibionts Setaphyes kielensis and S. dentatus (Kinorhyncha) , of these 308 specimens by light microscopy and 397 specimens by SEM. The basibionts were deposited at the Museum für Naturkunde Berlin in the collection "Vermes" under the catalogue numbers ZMB 12294–12313, 12359–12418, and 12454–12514. The holotype represents the specimen with a swarmer ventrally on segment 1 of the basibiont ZMB 12499. All light microscopical epibionts on the basibiont S. kielensis ZMB 12479–12505 represent paratypes. For collecting details see Table 1 View TABLE 1 .

Type locality

Intertidal mud at Kampen, east coast of the island of Sylt, German Bight, North Sea, 54°57’15”N, 008°21’34”E, precision 50 m.

Type basibiont

Setaphyes kielensis ( Zelinka, 1928), Kinorhyncha, Pycnophyidae

Additional basibiont

Setaphyes dentatus ( Reinhard, 1881) , Kinorhyncha, Pycnophyidae

Etymology

The species is named after Birgit Hussel, previously technician at the Litoralstation Sylt, in recognition of her help to B.N. and H.Y. with collecting the specimens and her engagement over many years in sending meiofauna samples from Sylt to the first author for his public outreach activities in Germany and Sweden during the 2000s.

Diagnosis

Acinetid with calyciform, dorso-ventrally compressed lorica of about 35 µm x 30 µm size, short stalk with internal longitudinal striae, one left and one right row of tentacles ca. 5 µm long, tentacles separated by small gap, epibiontic on pycnophyid Kinorhyncha.

Description

Specimens of Trematosoma husselae sp. nov. sat on a short stalk and revealed a calyciform, dorso-ventrally compressed lorica (lorica holotype: 37 µm length x 31µm width; range 30–47 µm x 26–34 µm, thickness 9–16 µm) with the zooid ( Figs 2 View FIGURE 2 , 3 View FIGURE 3 , 4B–F View FIGURE 4 , 5A–C View FIGURE 5 , 7 View FIGURE 7 , 8 View FIGURE 8 , 10C View FIGURE 10 ). The zooid usually filled the lorica except for a small basal cavity ( Figs 2 View FIGURE 2 , 4D, F View FIGURE 4 , 5B, L View FIGURE 5 ). The stalk (length 5–7 µm, width 3–4 µm) contained few longitudinal striations recognisable only in favourable light microscopical specimens ( Figs 4F View FIGURE 4 , 5G View FIGURE 5 ). The apical edge appeared more pronounced in SEM mounts and sometimes more rounded in light microscopical preparations depending on the degree of flattening on the slide (comp. Figs 3 View FIGURE 3 , 7 View FIGURE 7 and 8 View FIGURE 8 with Figs 2A View FIGURE 2 , 4B–F View FIGURE 4 and 5A View FIGURE 5 ). The surface of the lorica showed slightly elevated circular rings at irregular intervals around the body in SEM ( Figs 3D View FIGURE 3 , 8A View FIGURE 8 ). In optical section, the lorica wall appeared much thicker (about 4 µm) in its basal two thirds than apically ( Figs 2 View FIGURE 2 , 4C–F View FIGURE 4 ). The tentacles (length 4–6 µm) could be withdrawn, and the terminal end of the lorica revealed a cleft ( Figs 2B View FIGURE 2 , 3G View FIGURE 3 , 4A View FIGURE 4 ). The tentacles occurred in one left and one right row separated by a small gap on one of the broader sides of the zooid ( Figs 2 View FIGURE 2 , 4C View FIGURE 4 ), but seemed sometimes to form a single row of tentacles ( Figs 3 View FIGURE 3 , 4E View FIGURE 4 , 7B View FIGURE 7 , 8 View FIGURE 8 ). An epibiont exhibited 8–16 tentacles in each row ( Figs 2 View FIGURE 2 , 3C–F View FIGURE 3 , 4C, E, F View FIGURE 4 , 8A View FIGURE 8 ). Each capitate tentacle terminated in a small blunt knob with a minute central depression ( Figs 2 View FIGURE 2 , 3D–F View FIGURE 3 , 4C View FIGURE 4 ). Occasionally, empty shells of T. husselae sp. nov. were found (ZMB 12462, 12488; Fig. 4A View FIGURE 4 ).

Specimens of Trematosoma husselae sp. nov. possessed usually one central spherical macronucleus and occasionally a more ovoid macronucleus or two spherical macronuclei, which did not fuse at a different focal level (ZMB 12499; Fig. 5C View FIGURE 5 ). In many cases, no micronuclei could be observed, but often 2–7 spherical micronuclei of the same yellowish colour as the macronucleus were found (e. g., ZMB 12479, 12480, 12500; Figs 2 View FIGURE 2 , 4C, D View FIGURE 4 ). A contractile vacuole? may appear apically in an epibiont, but could only be traced in few specimens, possibly because of insufficient conservation.

Eleven epibionts harboured a single, inner, ovoid structure covered by two membranes, with a nucleus (ZMB 12365, 12397, 12489, 12492, 12498, 12499, 12500; Figs 4D View FIGURE 4 , 5B View FIGURE 5 ; 13–15 µm x 8–10 µm). This ovoid structure was interpreted as a developing swarmer. Trematosoma husselae sp. nov. seemed to develop from a significantly smaller spherical stage ( Fig. 5D, E View FIGURE 5 ; 12 µm x 10 µm) with a minimum of about four tentacles and a short stalk (3 µm x 2 µm) via small calyciform and laterally compressed stages to much larger calyciform and laterally compressed specimens with up to 25 tentales (comp. Fig. 4C–F View FIGURE 4 with Fig. 5D, E View FIGURE 5 ). One young attached specimen (16 µm x 13 µm) seems to possess parallel rows of surface structures ( Fig. 5F View FIGURE 5 ).

A small spherical structure with one macronucleus and two micronuclei seemed to be held by the tentacles of a specimen of T. husselae sp. nov. (ZMB 12492; Fig. 4E View FIGURE 4 ). This was interpreted as a swarmer recently born from its trophont.

On one specimen on S. dentatus , a small spherical Trematosoma husselae sp. nov. with few tentacles appeared inside the empty shell of a larger empty lorica (ZMB 12503; Fig. 5G View FIGURE 5 ). This specimen was probably re-arranged during mounting of the slide and is regarded as an artefact.

In specimens collected 1998, the cytoplasm was often found withdrawn from the base to the apical part of the lorica and revealed almost no substructures except the macronucleus and micronuclei; tentacles could usually not be traced ( Fig. 5M View FIGURE 5 ). This situation is interpreted as a fixation artefact. Few specimens were preserved more satisfyingly similar to the ones collected 2016, e. g., specimens on ZMB 12397 and 12399 ( Fig. 5L View FIGURE 5 ).