FIRST RECORDS OF CILIATE SUCTORIAN EPIBIONTS ON HYDRAENA (COLEOPTERA) FROM SOUTH KOREA

In the course of a recent survey of South Korea, a two species of suctorian ciliates, i.e., Urnula turpissima Kormos, 1958 and Periacineta hydrochi (Matthes, 1954), attached on water beetles of the genus Hydraena (Hydraenidae, Coleoptera), were collected and reported for the first time for South Korea. Periacineta hydrochi is reported for the first time after its original description.


Introduction
Suctorians (class Suctorea) is a peculiar group of carnivorous or parasitic ciliates (Dovgal 2002) which is poorly known in respect of distribution and species composition of species living as epibionts on of aquatic beetles inhabits lotic ecosystems (Dovgal and Pešić 2012).
In the course of a recent survey of the water mite fauna of South Korea (see Pešić et al. 2012), junior author collected a two species of suctorian ciliates, i.e., Periacineta hydrochi (Matthes, 1954) and Urnula turpissima Kormos, 1958, attached on the water beetles of the genus Hydraena (Hydraenidae, Coleoptera). This paper aims to present the highly interesting results of the investigations. This is possible first report of freshwater suctorian ciliates from Korea, and first records of these species for Korea.
Moreover as the both species rarely were collected, we give an detailed description of these species based on the new findings from South Korea.

Material and methods
Suctorian specimens used in the present study were found attached on aquatic beetles of the genus Hydraena (Coleoptera) collected from a river (36º57.182' N, 129º17.670' E, 24.v.2013) at the road to Sobaeksan NP, South Korea; a permanent sandy/bouldary river was remarkably exposed to sunlight, without riparian vegetation (Fig. 1B).
Hydraenid beetles were collected by hand netting, sorted on the spot from other living material and preserved in 75% alcoxol. For the preparation of slides the material was placed on the microscope slide in 20% glycerol-4% formalin mixture (in the proportion 1 part of glycerol to 4 parts of formalin), coat by cover

Research Article
glass accompanied by the edging of polystyrene (Jankowski 1975). Permanent slides of infested animals were deposited in the collections of the Department of Fauna and Systematics of invertebrate animals of Schmalhausen Institute of Zoology, National Academy of Sciences, Ukraine.
The measurements were performed using a computer program ScopePhoto 2.0.

Results
Subclass Evaginogenia Jankowski, 1975 Order Discophryida Jankowski, 1975 Family Periacinetidae Jankowski, 1978 Genus Periacineta Collin, 1909 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 ( 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.
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.
Subclass Exogenia Collin, 1912Order Metacinetida Jankowski, 1978 Family Metacinetidae Bütschli, 1889 Genus Urnula Claparede et Lachmann, 1859 Urnula turpissima Kormos, 1958 (Figs. 2B-E) Diagnosis. Suctorian ciliate with stylotheca-type lorica. The trophont cell body is spherical or ellipsoidal, clamped to the mouth of stylotheca. Macronucleus central, large, spherical. The tentacle is single, long, flexible and agile. Stylotheca is spherical or slightly elongated. The upper part of the lorica has four processes, which adjoins each other along the entire length except the central part forming a chinked mouth, resulting that the apical edge of the lorica is plicate from the lateral view. Reproduction by semicircumvaginative budding. The swarmer is ellipsoid with slightly concave ventral surface and with 8 transversal ciliary rows (Fig. 2E).