Thecacineta calix ( Schroder, 1907 )

Dovgal, Igor, Chatterjee, Tapas & Ingole, Baban, 2008, An overview of Suctorian ciliates (Ciliophora, Suctorea) as epibionts of halacarid mites (Acari, Halacaridae), Zootaxa 1810, pp. 60-68 : 63-64

Thecacineta calix ( Schroder, 1907)

( Fig. 6, 12)

= Acineta calix Schroder, 1907

= Thecacineta desmodorae Schulz = Thecacineta subantarctica Allgen

= Thecacineta donsi Allgen

= Thecacineta paradesmodorae Allgen = Thecacineta laophontis Jankowski, 1981 , syn. n. = Paracineta moebiusi Kahl, 1934 , syn. n.

Diagnosis: Type species of the genus. Marine loricate, suctorian. Cell body entirely fills the lorica and attached to their bottom. Lorica totally ribbed transversely. Apical part of body protrudes beyond lorica aperture. Up to 30 clavate tentacles with length about 90 µm arise from upper body surface. Macronucleus large, oviform, located at the bottom of the cell body. With large contractile vacuole placed in basal body part usually near macronucleus. Body dimensions: lorica high 73–113 µm (75–105 µm after Matthes 1956), width 25–28 µm (39–53 µm after Matthes 1956), body length 73–140 µm, body width 16–21 µm, diameter of lorica aperture (after Matthes 1956) 18–30 µm, macronucleus dimensions 7–16 x 6–7 µm, stalk length 9–39 µm (10–33 µm after Matthes 1956), stalk diameter 1.6–2 µm. Reproduction by vermigemmy with formation of single larval stage (swarmer), devoid of ciliature and crawling over the substrate.

Remarks on the systematics and nomenclature: Thecacineta calix , a marine, loricate, suctorian ciliate with a single apical fascicle of tentacles, was described from marine nematodes ( Schroder 1907). Subsequently, Collin (1909) combined all known species that had a similar morphology into the genus, Thecacineta Collin, 1909 . In 1912, in a monograph on suctorian ciliates, Collin redescribed the genus and named T. calix as a type species. T. calix was investigated in detail by Matthes (1956), in his revision of thecacinetid suctorians. Several species found on the interstitial marine nematodes and harpacticoid copepods were synonymyzed with T. calix : T. desmodorae Schulz , T. subantarctica Allgen , T. donsi Allgen and T. paradesmodorae Allgen.

Jankowski (1981) proposed a new specific name, T. laophontis , for T. calix found by Matthes (1956) on copepod crustaceans. The basis for his conclusion was the presence of some morphological differences between forms from crustaceans and nematodes. However, Jankowski (1981) did not present any arguments to support his conclusions. We believe that the name proposed by Jankowski (1981) is a junior synonym of T. calix .

A species of Paracineta was identified by Moebius (1888), cited after Kahl, (1934) from the Kiel Bay of the North Sea from “ Holocarus sp.” under the name Acineta crenata ( Fraipont 1878) . According to Kahl’s (1934) opinion, the identification of Par. crenata by Moebius (1888) was erroneous, and Kahl (1934) described it as a new species, Par. moebiusi .

Both Kahl (1934) and Curds (1987) have indicated the host name for Kahl’s (1934) species as Holocarus sp. Kahl (1934) did not mention the systematic position of the host, whereas Curds (1987) noted that it was a crustacean. However, it is likely that this was a mistake, and that the host was a species of the mite genus Halacarus , family Halacaridae . We feel that Par. moebiusi is similar enough to T. calix to warrant making it a junior synonym of T. calix .

Distribution and host prevalence: T. calix was observed on halacarid mites by Gelmboldt & Dovgal (2005). It has been found on the idiosoma and legs of Halacarellus sp. in Odessa gulf of the Black Sea near biological station of the Odessa National University in the interstitial at a depth of 5–20 cm.

Among the suctorians observed by Bartsch (1989, 1998) and Abé (1997), we identified T. calix from the Black Sea near Sevastopol on the idiosoma of Halacarellus micropectinatus Bartsch ; the North Sea on Cop. fabricii (Lohmann) ( Bartsch 1989, Fig. 19; Bartsch 1998, Fig. 90); and from the northwest Pacific Ocean off Hokkaido, Japan, on the posterodorsal plate of Actacarus octosetus Abé ( Abé 1997, figs. 5G, F). As previously mentioned, T. calix has also been described from nematodes and copepods. Its presence on marine mites testifies to its wider distribution and host spectrum.