Trichophrya salparum Entz, 1884

Flood, Per R., Spriet, Endy, Erichsen, Egil S. & Dovgal, Igor V., 2015, First record of a ciliate suctorian (Ciliophora, Suctorea) epibiont on the jellyfish Pelagia noctiluca (Scyphozoa, Semaeostomaeida), Ecologica Montenegrina 2 (4), pp. 302-306 : 303-305

Trichophrya salparum Entz, 1884

( Fig. 1-5 ).

Diagnosis. Unloricate, unstalked suctorian ciliate. The body is somewhat hemispheric or saddle-shaped, with a large, flat base. There are two (rarely one) bundles of capitate tentacles. There are from four to 32 tentacles in each fascicle. Their diameter varied between 0.7 and 1.2 µm dependent on their degree of contraction. Tentacles are capitate with globular knobs covered by several smaller haptocyst dots. The cytoplasm is uncolored, but may contain some bright granules. The macronucleus is granular, and spherical or elongated. There are from one to three contractile vacuoles. Reproduction by multiple internal budding ( Fig. 1c ).

Measurements (in µm) based on 15 specimens: Body length (parallel to an axis passing through both tentacle fascicles) 20-42 (mean 27.8). Body width 12-32.9 µm (19.6). Length of tentacles from four (contracted) to 42 (extended). After literary data ( Sand, 1901) body height 20-50, width 30-90.

Remarks. Entz (1886) originally described the species from the Mediterranean Sea near Napoli (type locality) on salp Thalia democratica Forskål, 1775 (type host).

However, the first find of suctorian ciliate on tunicates probably belongs to Lachmann (1859) who mentions the species Trichophrya ascidiarum found on sea squirts of the genus Polyclinum Savigny, 1816 in the North Sea. Unfortunately, this species was not described by the author, thus the specific name Trichophrya ascidiarum Lachmann, 1859 is a nomen dubium.

Tregouboff (1916) described a subspecies of T. salparum named T. salparum pyrosomae Tregouboff, 1916 ( Fig. 1d ). However, T. salparum is an extremely variable species thus we believed there is no reason to divide the species into subspecies. Thus, T. salparum pyrosomae Tregouboff, 1916 syn. n. is a younger synonym of T. salparum .

Among the 12 species that belong to the genus Trichophrya only three, including T. salparum , have from one to two tentacle fascicles: The other two are T. angulata Dangeard, 1890 , and T. brevis (Goodrich & Jahn, 1943) .

However, according to Dangeard’s (1890) observations T. angulata has exogenous budding thus affiliating the species to the Trichophrya is uncertain.

As for T. brevis , this species is likely to be a specific commensal of freshwater turtles. In addition, the curved or U-shaped (not rounded) macronucleus is characteristic for the latter species ( Dovgal 1996, 2013).

The T. salparum was specified by Jankowski (1967) as a type species of genus Actinobranchium Jankowski, 1967 . The lack of tentacle knobs were mentioned as a main characteristic of the genus ( Jankowski 1981). However, as was shown of Dovgal (2002) there is a tentacle knob in the type species, and the generic name Actinobranchium was therefore synonymized with Trichophrya .

Distribution and host prevalence. After the first discovery of T. salparum, Calkins (1902) reported its presence on the branchial bars of the ascidian Molgula manhattensis De Kay, 1843 from the western Atlantic Ocean near Falmouth (Woods Hole) ( Fig. 1a ). Collin (1912) in the Mediterranean Sea near Sette ( France) found later this species on Thalia democratica Forskål 1775 and Salpa fusiformis Cuvier, 1804 ( Fig. 1b, c ). Finally, Tregouboff (1916) observed the species on Pyrosoma elegans Lesueur, 1813 ( Fig. 1d ) from Villefranche-sur-Mer ( France).

Thus, earlier the species has been found exclusively on tunicates. The lack of finds of T. salparum on scyphozoan jellyfishes is probably due to the difficulties in discovering a small epibiont ciliate on such thick and voluminous bodies.

We found 23 specimens of T. salparum attached directly to the exumbrellar epithelium of Pelagia noctiluca on a single SEM preparation. This covered some 7.5 mm 2 of the jellyfish dome and consisted of smooth parts separated by several nematocyst warts ( Fig. 2 ), characteristic for this species. The suctorians were exclusively found on the smooth parts where the epithelial surface was covered by densely packed irregular microridges and occasional cilia ( Figs. 3 & 4 ). Tiny microvilli also projected from the attachment surface of the suctorian body towards the jellyfish tissue ( Fig. 5 ).

Figures

Figure 1. Trichophrya salparum Entz, 1884 in agreement with different authors: a – trophont stage from Molgula manhattensis (after Colkins 1902); b - trophont (after Collin 1912); c – multiple internal budding (after Collin 1912); d – individual from Pyrosoma elegans named T. salparum pyrosomae (after Tregouboff 1916).

Figures 2-5. 2 Scanning electron micrograph of exumbrellar epithelium of Pelagia noctiluca with two nematocyst warts (W). Seven suctorians are indicated by asterisks. 3 Scanning electron micrograph of a T. salparum attached to the exumbrellar epithelium of P. noctiluca. The knobs are prominent at the ends of the contracted tentacles. Several jellyfish cilia [c] reach above the epibiont. 4 Scanning electron micrograph of T. salparum with extended tentacles. 5 Scanning electron micrographic detail of the rim of the suctorian attachment surface towards the jellyfish exumbrellar epithelium (between arrowheads).