INTRODUCTION
The filamentous brown algal genus, Acinetospora, was described by Bornet in 1892. It is characterized by having sparsely branched uniseriate filaments forming entangled tufts, scattered meristematic zones, crampons, plurilocular sporangia (acinetosporangia), and monosporangia (Bornet 1892;Sauvageau 1899). Currently, four Acinetospora species are recognized from worldwide: A. crinita (Carmichael in Harvey) Sauvageau from Scotland (Womersley 1987), A. nicholsoniae Hollenberg from California, U.S.A. (Hollenberg 1971), A. filamentosa (Noda) Yaegashi from Japan (Noda 1970;Yaegashi et al. 2015), and A. asiatica Yaegashi, Yamagishi et Kogame from Japan (Yaegashi et al. 2015). Of them, A. crinita and A. asiatica have been reported in Korea (Kim 2010;Oteng’o et al. 2018).
The genus Microspongium was described by Reinke in 1888. It is characterized by pulvinate thalli with spongy-gelatinous structure, monostromatic base of apparently scattered filaments, branched and densely intricate erect filaments, 1-3 discoid phaeoplasts per cell, and plurilocular sporangia on terminal or lateral part of the erect filaments (Rienke 1888;Fletcher 1987;Peters 2003). Currently, six Microspongium species are recognized from worldwide: M. alariae (P. M. Pedersen) A. F. Peters from Greenland (Pedersen 1981;Peters 2003), M. globosum J. Rienke from Germany (Rienke 1888), M. immersum (Levring) P. M. Pedersen from Norway (Levring 1937; Athanasiadis 1996), M. kuckuckianum V. Schiffner from Adriatic Sea (Schiffner 1916), M. radians (M. Howe) A. F. Peters from Peru (Dawson et al. 1964) and M. stilophorae (P. L. Crouan & H. M. Crouan) Cormaci et G. Furnari from Adriatic Sea (Crouan and Crouan 1867;Hauck 1884). None of these has been reported in Korea.
We collected two unidentified filamentous brown algae from coast of Korea. We observed their detailed morphology and analysed molecular data based on rbcL and cox1 genes for their phylogenetic relationships. In this study, we add Acinetospora filamentosa and Microspongium stilophorae to the Korean marine algal inventory.
MATERIALS AND METHODS
1. Morphology
Samples of Acinetospora filamentosa were collected from west and south coasts of Korea. They were sorted into voucher herbarium specimens, silica gel samples, and formalin samples. Formalin samples were preserved in 4-5% formalin/ seawater. A sample of Microspongium stilophorae was collected from east coast of Korea. It was isolated from Dictyopteris pacifica and cultured in provasoli enriched seawater (PES) medium in order to get enough material for morpho- anatomical and molecular analysis. Photomicrographs taken using an Olympus BX51TRF microscope (Olympus, Tokyo, Japan) and an Olympus DP71 camera. Permanent slides were mounted in 70% karo syrup. Representative specimens examined in this study were deposited in the herbarium of Chosun University (CUK) and National Institute of Biological Resources (NIBR), Korea.
2. Molecular study
Genomic DNA was manually extracted from silica-gel samples using extracted using a NucleoSpin Plant II Kit (Macherey-Nagel, Düren, Germany). The extracted DNA was stored at -20°C and used to amplify rbcL and cox1. The rbcL gene was amplified using the primer combinations NDrbcL2-DRL1R and DRL2F-R3A (Kogame et al. 1999;Hwang et al. 2005) with HelixAmp Ready-2x-Go Series (NanoHelix Co., Ltd., Daejeon, Korea). The GazF2- GazR2 combination of primers used for cox1 (Saunders 2005;Lane et al. 2007). All PCR amplication were carried out with a Veriti 96-well Termal cycler (Applied Biosystem, ThermoFisher Scientific, USA). PCR products were purified using a PCRquick-spinTM PCR product purification kit (iNtRON Biotechnology, Inc, Seongnam, Korea). All rbcL and cox1 sequence data were compiled by the present study and obtained from GenBank and aligned with ClustalW (Thompson et al. 1994). New rbcL sequences obtained from Acinetospora filamentosa have been deposited in EMBL/GenBank under the accession numbers MN 052856 (CUK12425), MN052857 (CUK13048), MN 052858 (CUK12847) and MN052859 (CUK18942). Asterocladon rhodochortonoides and A. interjectum were selected as outgroup. Microspongium stilophorae sequence data are deposited in EMBL/GenBank under accession number MN052860 (CUK19276) for cox1. Laminaria yezoensis and Saccharina groenlandica were selected as outgroups.
Phylogenetic analyses were conducted using MEGA version 6.06 (Tamura et al. 2013). Maximum likelihood analyses were conducted using the GTR+G+I model, with 1,000 bootstrap replicates. Bayesian inference was performed using MrBayes 3.2.6 (Huelsenbeck and Ronguist 2001;Ronguist and Huelsenbeck 2003). Markov chain Monte Carlo runs were conducted for 2 million generations, each with one cold chain and three heated chains using the GTR+Γ+I evolutionary model and sampling and printing every 1,000 generations. Summary trees were generated using a burn-in value of 800.
RESULTS AND DISCUSSION
Acinetospora filamentosa (Noda) Yaegashi, Uwai et Kogame, 2015 실솜말 (신칭) (Figs. 1, 2)
Basionym:Ectocarpus filamentosusNoda 1970. Sci. Rep. Niigata Univ. Ser. D. 7: 27.
Heterotypic Synonym:Ectocarpus ugoensis Konno in Konno et Noda 1974. Sci. Rep. Niigata Univ. Ser. D. 11: 80.
Material examined: NIBROR0000001612 & CUK12425 (= MBRB0099TC12425) Chuja-hang, Chuja-myeon, Jeju-si, Jeju Special Self-govering Province, Korea (33° 57ʹ44.69″N, 126°17ʹ47.12″E), June 27, 2014, T. O. Cho, S. Y. Jeong, D. B. Mostajo, J. G. Lee and S. Y. Park, at 1 m depth by hand; CUK12847 (= MBRB0099TC12847), Daejin- hang, Daejin-dong, Donghae-si, Gangwon-do, Korea (37°34ʹ 47.64″N, 129°6ʹ51.13″E), August 01, 2014, T. O. Cho, S. Y. Jeong, D. B. Mostajo, J. G. Lee and S. Y. Park, at 1 m depth by hand; CUK13048 (= MBRB0099TC13048), Biyang-do, Hanrim-eup, Jeju-si, Jeju Special Self-govering Province, Korea (33°24ʹ 21.9″N, 126°13ʹ46.40″E), May 30, 2014, T. O. Cho, S. Y. Jeong, D. B. Mostajo and J. G. Lee, at 1 m depth by hand; CUK18942 (= MBRB0099TC18942), Mo-hang, Byeonsan-myeon, Buan-gu, Jeollabuk-do, Korea (35°34ʹ 58.49″N, 126°30ʹ18.41″E), May 12, 2018, T. O. Cho and B. Y. Won, at 1 depth by hand.
Habitat: Epiphytic and saxicolous at the tide pool in intertidal zone.
Morphological observation: Plants are uniseriate, forming entangled tufts (Fig. 1A) to 10 cm or more in length attached to rocks and other seaweeds (e.g. Sargassum spp.). Erect filaments are irregularly and sparsely branched at wide to right angles (Fig. 1B) and form straight to curved “crampons” composed of 2-5 cells (Fig. 1C). Meristematic zones (Fig. 1D) are scattered, consisting of short cells. Cells of erect filaments are 20-80 μm in length and 18-28 μm in width, containing many discoid chloroplasts (Fig. 1E) with pyrenoids. Phaeophycean hairs (Fig. 1F) are found later-ally or terminally on erect filaments. Unilocular sporangia are spherical to oval, 25-55 μm in length and 25-55 μm in width, sessile or on a pedicel, and are formed on erect filaments.
World distribution: Asia: Japan and Korea; Europe: Greece (Guiry and Guiry 2019).
Identifier: Tae Oh Cho and Antony Otinga Oteng’o.
Phylogenetic analyses: The 1326-nucleotide portion of rbcL was aligned for Acinetosproa filamentosa. Phylogenetic analyses revealed that our Acinetospora samples from Korea were placed within a clade of Acinetospora filamentosa in rbcL (Fig. 2). There was only 0-0.008% gene sequence divergence between Genbank and our collection of Acinetospora filamentosa. In addition, it revealed that Acinetospora filamentosa differs from A. asiatica by 4.4-4.7% and from A. crinita by 3.0% gene sequence divergence respectively.
Remarks:Acinetospora filamentosa was a new combination with Ectocarpus filamentosus as the basionym (Yaegashi et al. 2015). Our samples collected from Korea had vegetative morphology similar to that of A. filamentosa. Our molecular analyses based on rbcL gene show that our samples are nested in the clade of A. filamentosa. In this study, we report A. filamentosa as a new record from Korea and add this species in the list of Korean macroalgal flora.
MicrospongiumReinke, 1888, 점말속 (신칭)
Microspongium stilophorae (P. L. et H. M. Crouan) Cormaci et G. Furnari, 2012 바늘점말 (신칭) (Figs. 3, 4)
Basionym:Ectocarpus stilophorae P. L. et H. M. Crouan, Florule du Finistére…., 1867: 161, Paris and Brest. x+262 pp., 31 [+1] pls, frontispiece.
Homotypic synonym (s):Streblonema stilophorae (P. L. Crouan & H. M. Crouan) De Toni 1895;Streblonema stilophorae (P. L. Crouan & H. M. Crouan) Kylin 1908 (comb. illeg.).
Heterotypic synonym (s):Ectocarpus stilophorae f. caespitosusRosenvinge 1893;Ectocarpus stilophorae v. caespitosus (Rosenvinge) L. Newton 1931;Microspongium tenuissimum (Hauck) A. F. Peters 2003;Streblonema stilophorae v. caespitosum (Rosenvinge) De Toni 1895;Streblonema tenuissimumHauck 1884.
Material examined: NIBROR0000001610 & CUK19276 (= MBRB0097TC19276) Yangjeong-hang, Uljin-eup, Uljin-gun, Gyeongsangbuk-do, Korea (37°00ʹ59.15″N, 129°24ʹ48.17″E), May 01, 2018, T. O. Cho and B. Y. Won, at 1 m depth by hand.
Habitat: Epiphytic on other seaweeds (e.g. on Stilophora sp., Nemalion sp. and Dictyopteris pacifica) at the tide pool in intertidal zone.
Morphological observation in culture: Cultured thallus isolated from Dictyopteris pacifica forms a spongy ball-like spherical tissue (Fig. 3A) formed by prostrate filaments of irregular cells in shape and size (Fig. 3B, arrows) and short erect filaments with short ramuli (Fig. 3B, arrowheads). Erect filaments are formed by cells 1-5 times longer than wide and 3-8 μm in diameter. The phaeoplasts (Fig. 3C, arrows) are one or two per cell. Phaeophycean hairs not frequent. Plurilocular sporangia lateral or mostly terminal, in uniseriate lodges, 3-8 μm wide (Fig. 3D, arrows).
World distribution: Arctic: Canada; Asia: Korea; Atlantic Islands: Iceland; Europe: Black Sea, Britain, Channel Islands, Faroe Islands, France, Ireland, Romania, Scandinavia and Spain (Guiry and Guiry 2019).
Identifier: Tae Oh Cho and Antony Otinga Oteng’o.
Phylogenetic analyses: The 613-nucleotide portion of cox1 was aligned for Microspongium stilophorae. Phylogenetic analyses revealed that our Microspongium sample from Korea was nested in a clade of Microspongium stilophorae based on cox1 (Fig. 4). In addition, it revealed that the gene sequence divergence between M. stilophorae (= “M. tenuissimum”) and M. alariae is 2.9-3.6%. However, there was only 0.16-0.49% gene sequence divergence between Genbank and our collection of M. stilophorae.
Remarks: Morphologically, our Microspongium sample is matched into the description of Microsporangium stilophorae. Microspongium tenuissimum and M. radians were conspecific based on cox1 gene (Murúa et al. 2018). Microspongium tenuissimum is currently a synonym of M. stilophorae (Cormaci et al. 2012;Guiry and Guiry 2019). Our molecular data based on cox1 gene revealed that our Korean sample is nested in the same clade of M. stilophorae. In this study, we report Microsporangium stilophorae as a new record from Korea and add this species to the list of Korean macroalgal flora.