INTRODUCTION

Red algal parasites are common on other red algae and have been described from at least eight orders within the Florideophyceae (Ng et al. 2014; Preuss and Zuccarello 2014). These parasites have little or no photosynthetic pigmentation, and use only other red algae as hosts. They are generally small and morphologically simple, composed of branching filaments of cells penetrating between cells of the pseudoparenchymatous host and a tissue mass that protrudes from the host thallus and bears reproductive structures (Ng et al. 2014). Moreover, they are highly host-specific and can be found on hosts that are morphologically considerably like the parasites (Goff et al. 1997). Until now, more than hundreds of taxa of parasitic red algae are known from all the world’s oceans (Blouin and Lane 2012).

In Korea, only four parasitic red algal genera have been reported (Nam and Kang 2012, 2013; Kim et al. 2013). These include Janczewskia Solms-Laubach, on Laurencia sp., Benzaitenia Yendo on Chondria sp., Kintokiocolax T Tanaka & Y Nozawa on Grateloupia sp. and Symphyocolax MS Kim on Symphyocladia sp. Among them, three red algal parasitic genus, except for Kintokiocolax, belonging to the Rhodomelaceae have been reported from flora of Korea (Kim et al. 2013). During the survey of indigenous species in Korea, delesseriacean parasitic red algal species belonging to Asterocolax Feldmann & G Feldmann was collected from Jindo. Based on morphological data, this species was identified as Asterocolax denticulatus (Tokida) Feldmann & G Feldmann recorded newly in Korea.

MATERIALS AND METHODS

Specimens for this study were collected from Jindo (34°15′ N, 126°00′ E). Morphological and anatomical data were obtained from liquid-preserved specimens. Liquid-preserved materials were stored in a 5-10% formalin-seawater solution. Sections were made by hand using razor blades and pith stick, and transferred to a slide glass with distilled water. For permanent slides, 10-30% corn syrup was used as a mounting medium. Measurements are given as length and diameter. Photographs were taken with a CCD cam- era (MicroPublisher 5.0, Qimaging, Canada) and a digital camera (TG-4, Olympus, Japan) attached to a microscope (DMLB, Leica, Germany). All specimens examined in this study are now deposited in the herbarium of the Department of Marine Biotechnology, Kunsan National University, Gunsan, Korea.

RESULTS AND DISCUSSION

Asterocolax denticulatus (Tokida) Feldmann & G Feldmann 1951: 1138

Basionym:Polycoryne denticulataTokida (1934)

Type locality: Robben Island, Saghalien Islands, Russia

Korean name: Top-ni-bo-ra-ip-deo-bu-sal-i nom. nov. (신칭:톱니보라잎더부살이).

Specimens examined: KSNU000010059-KSNU000010060 (♀), KSNU000010061 (♂), KSNU000010062-KSNU 000010063 (⊕), KSNU000010064-KSNU000010066 (Vegetative plants) (Jindo, Jeonnam: 13.viii.2012).

Habitat: Parasite on Pseudopolyneura japonica.

Morphology: Thalli parasitic on Pseudopolyneura japonica (Fig. 1A), pale pink to pink, forming a pulvinate mass 3-5 mm in diameter (Fig. 1B, C); dozens of needlelike or clavate blades in a dense cluster (Fig. 1C); individual axes up to 3 mm long. Blades flattened, with a smooth surface while young, more or less denticulate when matured (Fig. 1D). Spermatangia (Fig. 1E) and tetrasporangia (Fig. 1F) entirely covering male and tetrasporic blades respectively; tetrasporangia tetrahedrally divided, 25-35 μm in diameter. Female branches bearing one cystocarp to subapical in position (Fig. 1C); cystocarps globose, to 500 μm in diameter; carpospores catenate.

Four genera of parasitic Delesseriaceae are now recognized (Wynne 1970): Gonimophyllum Batters, Gonimocolax Kylin, Polycoryne Stottsberg, and Asterocolax Feldmann & G Feldmann. Among them, Asterocolax was characterized by Feldmann and Feldmann (1951) as growing by means of one apical cell undergoing transverse divisions. In genus Asterocolax, four species are now recognized (Guiry and Guiry 2017). These species occurred as a parasite on several delesseriacean hosts (Table 1). Type species of this genus, A. erythroglossi Feldmann & G Feldmann, was illustrated (Feldmann 1958, fig. 23) with a stellate clump of a few short, terete blades. This species occurred as a parasite on Erythroglossum laciniatum (Lightfoot) Maggs & Hommersand (Table 1). Asterocolax gardneri (Setchell) Feldmann & G Feldmann has been described with needle-like blades (Smith 1944) and a cluster of small club-like blades (Wagner 1954) 2-3 mm in diameter (Abbott and Hollenberg 1976). A. gardneri occurred as a parasite on several delesseriacean hosts (Phycodrys, Nienburgia and Polyneura) (Table 1). Although Setchell (1923) described the cystocarps of A. gardneri as being situated in basal parts of blades, Wynne’s material reveals them to be median to subapical in position, between the narrow stalk and pointed apex (Wynne 1970). Also, Wagner (1954) illustrated cystocarp located closer to the apex. A. hypophyllophila Wynne differ from the other species by its larger size (6 mm in diameter) (Table 1) and the greater number of blades in a cluster, and forming flat blades (Wynne 1970). This species occurred as a parasite on Mikamiella ruprechtiana (Zinova) Wynne. A. denticulatus was initially described as Polycoryne denticulata a parasite on Phycodrys fimbriata (Dela Pyli) Kylin by Tokida (1934). Later this species was transferred to genus Asterocolax by Feldmann and Feldmann (1951). Its distribution in Japan and Russia was known in previous reports (Tokida 1934; Yoshida et al. 1990; Perestenko 1994; Yoshida 1998; Guiry and Guiry 2017). Our specimens are characterized by more or less denticulate branches when matured (Fig. 1). According to Tokida (1934), A. denticulatus (as Polycoryne denticulata) differs from either of the other Asterocolax species in that it has denticulate or ramulose branches. This trait of our specimens fits well with Tokida’s previous description. So, these Korean specimens are identified as A. denticulatus based on those features, although flattened rather than cylindrical blades were observed. This is the first record of the delesseriacean parasitic red alga A. denticulatus in Korea.