Brachyosoma sp.

Chatterjee, Tapas, Sautya, Sabyasachi, Dovgal, Igor, Gaikwad, Santosh, Khokher, Sanofar H. & Choudhury, Amita, 2022, Report of deep-sea epibiont ciliates (Ciliophora) from more than 1000 m depth of the Arabian Sea, Indian Ocean, Zootaxa 5120 (3), pp. 423-434 : 431-432

Brachyosoma sp.

( Fig. 4 B–D )

Material examined: Five individuals found as epibiont on unidentified Ostracoda host collected from stn MUC-13, at 0–2 cm sediment depth, 3918 m water depth ( Fig. 4 A ) from Arabian Sea, Indian Ocean.

Diagnosis: Small unloricate suctorian ciliate with guttate cell body, lacking of stalk, with a single apical fascicle of capitate tentacles.Attached to the host body surface by very short posterior body projection.Actinophores absent. Macronucleus spherical, centrally located. Reproduction not described.

Measurements (based on two individuals, in μm): Body length 26–32, body width 12–16, macronucleus diameter 6–7, length of the tentacles 5–17.

Remark: In the such characters as unflattened, unloricate cell body, lacking of stalk, the found species is correspond to diagnosis of genus Brachyosoma ( Batisse 1975; Curds 1985b; Dovgal 2002). The generic name Brachyosoma was proposed as substituting for Hallezia Sand, 1899 in connection with homonymy of the latter ( Batisse 1975). The genus was proposed for endogemmic suctorian ciliates that lack both stalk and lorica and attach to the substrate by a basal cell protuberance. Batisse (1975) and Curds (1985b) assigned the genus to the family Tokophryidae Jankowski in Small & Lynn, 1985 (order Acinetida ). However, Dovgal (2002) has transferred the Brachyosoma into the family Trichophryidae (order Trichophryida ) based on the lack of the stalk in the representatives of the genus. Lynn (2008) also placed genus Brachyosoma into the family Trichophryidae .

There are four species of the genus ( Curds 1985b; Dovgal 2002), most of them were found in freshwater habitats. In size and body outlooks the found species is similar to freshwater B. oviformis ( Sand, 1899) (named as Hallezia oviformis ) found attached to algae in the river near Brussels, Belgium ( Sand 1899). However, it is Jankowski’s (2007) opinion, that the species Hallezia oviformis is poor defined and indefinable.

It is believed ( Curds 1985b) that the endogenous budding is characteristic for representatives of genus Brachyosoma . At the same time, the presence of vermiform suctorian swarmers at the same host near individuals of Brachyosoma sp. ( Fig. 4 C , 2 ) attracts attention. However, the process of reproduction was not observed, hence the identity of these migratory stages to any suctorian taxon was impossible.

Figures

FIGURE 2. A–B. Thecacineta calix (Schroder, 1907) on nematode body; C–D. Actinocyathula homari (Sand, 1899) on nematode body; E–F. Loricophrya bosporica Sergeeva & Dovgal, 2016 on nematode body.

FIGURE 4. A. Trematosoma rotunda (Allgén, 1952) on nematode host; B–D. Brachyosoma sp. on ostracod host; 1—trophont of Brachyosoma sp., 2—vermiform suctorian swarmer.