Acineta sulcata Dons, 1927

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 : 65-66

Acineta sulcata Dons, 1927 , charact. emend

( Fig. 7 –8)

= Acineta benesaepta Schulz = Donsia sulcata (Dons)

= Plicophrya sulcata (Dons)

Diagnosis: Marine, commensal, suctorian ciliate, with stalk and lorica. Both lorica and cell body laterally compressed. Lorica heavily ridged transversely. With a wide flattened lorica base that is characteristic for the species. Apical aperture of the lorica dumb-bell shaped. Short, straight, stalk. Cell body shape varying from triangular to rectangular, attached to the aperture border of the lorica. Macronucleus ovoid, centrally located. Clavate tentacles arranged in two fascicles and placed at the two actinophores. Body dimensions: lorica length 16 µm (35.2 µm after Schulz 1933), lorica width 13 µm (26.4 µm after Schulz 1933), body length 13 µm (33– 55 µm after Curds 1985), body width 11 µm, stalk length 14 µm (22 µm after Schulz 1933). Macronucleus dimensions 8 x5 µm. Reproduction by endogenous monogemmic budding. The original measurements of Aci. sulcata were made using material collected in river Unava.

Acineta sulcata differs from Aci. tuberosa Ehrenberg, and other relatives, in that the lorica attaches to the apical aperture rather than at the bottom of the lorica, and by the wide flattened base of the lorica. However, the most characteristic difference is the presence of the pattern of transverse ridges (not folds as in some acinetids) on the lorica ( Jankowski 2007).

Remarks on the systematics and nomenclature: The synonymy of Aci. benesaepta Schulz, 1933 with Aci. sulcata was established by Kahl (1934). In Curds’ (1985) review, the genus, Plicophrya Jankowski was also synonymized with Acineta Ehrenberg. Mention of Aci. benesaepta as a valid name in Dovgal’s (2002) work was an error.

Distribution and host prevalence: Aci. sulcata was found on halacarids from the northern Norwegian coast. Suctorian ciliates were later observed by Schulz (1933) on halacarid mites from Kiel Bay and named Aci. benesaepta . Precht (1935) later found Aci. benesaepta in Kiel Bay on a species of Copidognathus . Kahl (1934) also reported Aci. sulcata from seed shrimps. Jankowski (1981, 2007) noted numerous finds of this species on halacarid mites from the coast of Barents Sea.

Bartsch and Panesar (2000) recorded Acineta sp. on the idiosoma and legs of Cas. hyrcanus Viets from the Danube River near Vienna, Austria, and commented that this suctorian probably was Aci. tuberosa Ehrenberg. After observing the figures of that species ( Bartsch & Panesar 2000 Fig. 1), we believe that it probably is Aci. sulcata . The same species (Fig. 8) was also found by Dovgal on the legs of an unidentified freshwater halacarid mite from the Unava River (Fastov region, Kiev Province, Ukraine) ( Dovgal & Pesic 2007). In that paper, the mite host was indicated erroneously as an oribatid.

General remarks: Bartsch (2003) surveyed the interactions between halacarid mites and their symbionts, and pointed out that the first report of these ciliates from a halacarid mite, Thalassarachna hasten (Johnston) , was mentioned in Gosse’s (1855) paper. Subsequently, suctorians were regularly observed on psammobiont halacarids, often in high numbers (>60 ciliates per host).

Bartsch (2003) also stated that suctorians lived predominantly on halacarid adults and deutonymphs, and rarely on protonymphs and larvae because of short life span in protonymph and larva stages. Analysis of the literature and our own data have shown that only four suctorian species observed to date on halacarids, that can be identified with certainty are Lim. ceter, Pra. halacari , Thecacineta calix and Aci. sulcata . Two of these species, Pra. halacari and Aci. sulcata , are most likely specific on their halacarid hosts. The other two species, Lim. ceter and T. calix , can be found on different benthic invertebrate animals. All of the above mentioned ciliate species are found on marine or brackish water hosts. Acineta sulcata can also inhabit freshwater i f t h e i r h o s t s a r e e u r y h a l i n e.

Suctorian species from halacarids generally attach in the idiosomatic region, but are not restricted there. They also may occur on the gnathosoma and legs. Under conditions of high infestation levels, suctorians may occupy sites anywhere on the body of the host.

Figures

FIGURE 7. Acineta sulcata Dons, 1927 from Barents Sea halacarid mites (after Jankowski 1981). FIGURE 8. Acineta sulcata Dons, 1927 from freshwater halacarid mite found in Unava river (orig.). Scale bar 10 µm.