Periacineta hydrochi ( Matthes, 1954 )

Dovgal, Igor & Pešić, Vladimir, 2014, First records of ciliate suctorian epibionts onHydraena (Coleoptera) from South Korea, Ecologica Montenegrina 1 (1), pp. 1-5 : 2-4

Periacineta hydrochi ( Matthes, 1954)

( Fig. 2A )

Diagnosis. Loricate, stalked suctorian ciliate. Lorica, much wider than long, flattened but slightly widens in its apical part. The stalk of various lengths, with a grows lines and slightly developed longitudinal striations in its basal part.

The cytoplasm is usually yellowish-brown. Four to six contractile vacuoles are located parallel to the front edge of the cell body. Macronucleus is horseshoe-shaped. Reproduction by inversogemmic budding.

Measurements (in µm): body length 26-61 (72-118 after Matthes 1954), width 37-69 (91-126 after Matthes 1954); length of stalk 12-71, diameter 10-14.

Remarks. The species was originally described by Matthes (1954) as Discophrya hydrochi Matthes, 1954 . Later on, this species was transferred to the genus Periacineta ( Dovgal, 2002, Mariño-Pérez et al. 2010). Our specimens from South Korea fits well the description of typical form of Discophrya hydrochi .

However, it is worth to mention that Matthes (1954) described aberrant form of this species, called by him in German as articular form (”Gelenkform”). According to Matthes (1954) and Matthes et al. (1988) this form is characterized by the following features: the length of lorica is greater than width; the individual as a rule is attached to the host body in such a manner that its body axis is perpendicular to the longitudinal axis of the beetle leg; the lorica mouth of ciliate is deeply curved thus its lateral ends omitted almost to level of junction between stalk and lorica; the stalk is enough wide and clearly separated from the lorica. Further, the cell body of “articular” individuals is dirty as a rule and correspondingly the macronucleus and the contractile vacuoles are poorly visible and the number of contractile vacuoles increased up to 9. Matthes (1954) gave the measurements: body length 113-143, width 85-122 µm.

Later on the “articular” form of Discophrya hydrochi was described by Jankowski (1981) as separate species, Arcodiscophrya heraldica Jankowski, 1981 . Recently, this species was transferred to the genus Periacineta under name P. heraldica ( Jankowski, 1981) (see: Dovgal 2002, Mariño-Pérez et al. 2010).

Distribution and host prevalence. The species was described by Matthes (1954) from Germany, and no further record of this species was published after its original description. Periacineta hydrochi is epibiont on hydrophilid beetles ( Matthes et al. 1988), attaching to the head and legs (often in articulation between femur and tibia) of their hosts. The known hosts includes following beetle species: Hydrochus elongatus (Schaller, 1783) , H. carinatus Germar, 1824 and Hydraena sp. (new host). The specimens examined from South Korea were found attached on the head and legs of the latter species.

Figures

Figure 2.A photograph ofPeriacineta hydrochi (Matthes, 1954), fromHydraena sp. B-EUrnula turpissima Kormos, 1958 (C-E after Kormos 1958): B photograph of specimen attached onPeriacineta hydrochi, from South Korea; C trophont, lateral view;D trophont, top view;E swarmer (after Kormos, 1958). Scale bar = 20µm (A-B).