First Description of Petalonia zosterifolia and Scytosiphon ... - Algae

138 Algae Vol. 17(3), 2002Figs 1-5. Petalonia zosterifolia.1. Thallus collected on 12 January 2002 from the upper intertidal zone of Onyangri, Jukbyun on the East coast. scale bar = 2 cm.2. Rhizoidal filaments at the basal part of thallus. scale bar = 100 µm. 3. Small cortical cells on the surface of thallus. 4. Cross sectionof the middle axis showing medulla and cortex. 5. Cross section of the middle axis showing plurilocular sporangia andmedullary cells. scale bars 3- 5 = 50 µm.

Cho et al.: Petalonia zosterifolia and Scytosiphon gracilis 139characterized by broad thalli (up to 3.5 cm in width) andthe presence of rhizoidal cells in medulla (Kogame 1997).P. binghamiae is circumscribed by a small holdfast of rhizoidand numerous rhizoidal cells in medulla (Rhew andBoo 1991).P. zosterifolia appears to occur in winter, as does inJapan (Kogame and Kawai 1993). From our survey,Guryongpo appears the southern distribution of thatspecies in Korea. This is the first report on the occurrenceof P. zosterifolia in Korea, recognized by both morphologyand ITS region sequence data as discussed below.Scytosiphon gracilis Kogame (1998): 39Figs 6-10Type: SAP 059720 (collected in 1 February 1990).Type locality: Ohma, Aomori, JapanDistribution: Japan and KoreaKorean name: GaneunmiyeoksilRepresentative specimens examined: Hado, Jeju (Boo,CNUK 007399 - 007405, 4.ii.2000; CNUK 007406 - 007498,10.ii.2002).Morphology: Thalli were erect, flattened, unbranched,hollow, twisted in the upper part, 14-(25) cm long andup to 0.4 cm in width (Fig. 5). Rhizoids were developedfrom the outer cortical cells near the base of the thalliand were multiseriate filaments (Fig. 6).The thalli were hollow in mature and 70-115 µm inthickness. The tissues were parenchymatous and consistedof an outer cortex and medulla. In the middle part,medulla was composed of 1-3 layers of cells withoutplastids. Medullary cells were round to oval and c. 46 x36 µm in transverse section. The cortex consisted of 1-3layers of small, angular to rectangular cells. Each corticalcell had a plastid with a prominent pyrenoid.Plurilocular sporangia were developed from the surfaceof the upper parts of thalli and matured basipetally.Plurilocular sporangia were closely packed.Phaeophycean hairs were solitary or grouped on the surface.Ascocysts between unilocular sporangia wereabsent.Scytosiphon gracilis was epilithic on concrete block androck, growing in the middle to the lower intertidal zonein relatively sheltered areas. Erect thalli occurred inFebruary in Hado on the east side of Jeju. Prostratesporophytes of S. gracilis (Kogame 1998) were not found.Taxonomic remarks: Our collections of S. gracilis fromJeju correspond to the original descriptions of Kogame(1998) and specimens from Aomori and HyogoPrefecture in Japan collected by Kazuhiro Kogame, theauthor of the original paper, and deposited in CNUK.Scytosiphon lomentaria is similar to S. gracilis, but is distinguishedby constricted thalli and Microspongium-likesporophyte (Kogame 1998). S. tenellus Kogame, which isreported only in Hokkaido of Japan, differs from ourspecies in having ascocysts between plurilocular sporangiaof erect thalli and Stragularia-like, crust sporophyte(Kogame 1998). The last species of Scytosiphon in Japan isS. canaliculatus (Setchell and Gardner) Kogame, which ischaracterized by Hapterophycus-like sporophyte (Kogame1998).Although S. gracilis was included in our RuBisCospacer region phylogeny (Cho et al. 2001), this is the firstmorphological description of the species in Korea. S. gracilismay be a winter species in Korea, as in Japan(Kogame 1998). Considering its occurrence from thenorthern Hokkaido to the southern Fukuoka in Japan(Kogame 1998), detailed collections in the field mayprobably extend the distributional areas in Korea.Analysis of ITS region sequencesThe entire ITS region (ITS 1, 5.8S, and ITS 2) in 22 samplesof five species ranged from 1069 bp in Scytosiphongracilis to 823 bp in Petalonia binghamiae. The ITS 1 regionranged from 638 bp in S. gracilis to 385 bp in P. binghamiae.The ITS 2 region was much shorter than the ITS 1region and ranged from 276 bp in P. binghamiae to 251 bpin P. zosterifolia. The 5.8S subunit sequence was almostconserved and was 162 bp long in all species determinedhere. A comparison of the ITS region in the Ectocarpalesis shown in Table 2.The pairwise divergences of the ITS region sequencesaveraged 0.12% among seven samples of P. zosterifolia, inKorea, and zero in between two samples of S. gracilisfrom different years. The pairwise divergence averaged0.33% among five samples of P. binghamiae from thenorth Pacific, and 2.35% among seven samples of P. fasciafrom the north Pacific and the north Atlantic. Thepairwise divergence (22.83-22.43%) between P. zosterifoliaand other Petalonia species was much higher than that(13.62%) between P. zosterifolia and S. gracilis. In addition,S. gracilis differed from S. lomentaria by 31.78% inpairwise divergence.The NJ tree (Fig. 11) showed that seven samples ofPetalonia zosterifolia from different locations and twosamples of Scytosiphon gracilis from different years produceda single clade, respectively. These two specieswere again grouped into a monophyletic clade with amaximum support (Bootstrap value = 100%), which

140 Algae Vol. 17(3), 2002Figs 6-10. Scytosiphon gracilis.6. Thallus collected on 4 February 2000 from the intertidal zone of Hado, Jeju. scale bar = 1 cm. 7. Rhizoidal filaments at the basalpart of thallus. scale bar = 100 µm. 8. Rectangular cortical cells on the surface of thallus. 9. Cross section of the middle axis showingphaeophycean hairs, cortical cells, and medullary cells. 10. Cross section of the middle axis showing a large cavity in medulla.scale bars 8-10 = 50 µm.

Cho et al.: Petalonia zosterifolia and Scytosiphon gracilis 141Fig. 11. Neighbor-joining tree for Petalonia zosterifolia andScytosiphon gracilis rooted with S. lomentaria. Bootstrap values(> 50%) are given above branches.showed sister relationships to the clade of Petalonia binghamiaeand P. fascia. The tree topology of the MP analysisshowed a similar pattern to that of the NJ tree. The strictconsensus of four most parsimonious trees when gapswere treated as missing data is shown in Figure 12.Despite the big difference in the length (Table 2), the ITS1 tree was similar to that of the ITS 2 tree in topologyand bootstrap support (trees not shown). When gapswere treated as a fifth base, the MP analyses producedfour equally parsimonious trees (Fig. 12), having a minimallength of 1054 steps, a CI of 0.891, and a RI of 0.968(Table 3).DISCUSSIONPetalonia zosterifolia is very similar to S. gracilis in habitand anatomy of the erect gametophytic thallus, andprostrate sporophytic crust (Kogame and Kawai 1993;Kogame 1998). The differences are structure of thallusFig. 12. Strict consensus of four maximum parsimonious treesfor Petalonia zosterifolia and Scytosiphon gracilis rooted withS. lomentaria, with gaps treated as missing data. The treelength was 648 steps, the consistency index was 0.9, andthe retention index was 0.966. Bootstrap values (> 50%) aregiven above branches.and the presence/absence of paraphysis. The thallus ofP. zosterifolia is solid but, when mature, sometimes hassmall cavities in medulla. In contrast, the thallus of S.gracilis is hollow. However, Kogame et al. (1999) reportedthat whether erect thalli are hollow or solid does notappear to be useful for distinguishing Petalonia andScytosiphon. Paraphyses are absent in P. zosterifolia(Rosenvinge and Lund 1947; Kogame and Kawai 1993),while unicellular paraphyses are present betweenunilocular sporangia in S. gracilis (Kogame 1998). Sinceparaphyses are consistently present in S. gracilis, theparaphysis may be an important criterion to recognize S.gracilis from P. zosterifolia (Kogame 1998). In this study,distribution ranges of P. zosterifolia, previously known inChina (Tseng 1983), Japan (Kogame and Kawai 1993),USA (Setchell and Gardner 1925), and the Atlantic(Fletcher 1987), and S. gracilis, previously reported only

Cho et al.: Petalonia zosterifolia and Scytosiphon gracilis 143between the species of Petalonia. The interspecific divergencesin the Scytosiphonaceae appear to be lower thanthose (18-34%) in the genus Elachista Duby of theChordariaceae (Uwai et al. 2001).Phylogenetic trees from all our data sets, e.g. ITS 1, ITS2, ITS region with gaps as missing data, and ITS regionwith gaps as a fifth character, consistently indicate theclose relationship (BP = 100) between P. zosterifolia and S.gracilis, that is congruent with results of analyses of rbcL,partial rbcS and partial 18S of nuclear ribosomal DNAsequences (Kogame et al. 1999), and the RuBisCo spacerregion sequences (unpublished data). The presence ofprostrate Compsonema-like thallus in both P. zosterifoliaand S. gracilis is considered as a synapomorphic character(Kogame et al. 1999). Our molecular data togetherwith morphological evidence suggest that P. zosterifoliaand S. gracilis might have shared a common ancestor.Our ITS trees also show that Petalonia zosterifolia is clearlyseparated from other species of Petalonia. On the otherhand, P. binghamiae and P. fascia are closely related toeach other, sharing Strangularia-like sporophytic thalli(Kogame et al. 1999). In addition, S. gracilis is distantlyrelated to S. lomentaria, having a Microspongium-likesporophyte. Kogame et al. (1999) suggested that prostratesporophytes appear to be phylogenetically important.If this is true in the classification of theScytosiphonaceae, the family needs a big change atgenus level (Kogame et al. 1999; Cho et al. 2001) and thetaxonomic revision of P. zosterifolia and S. gracilis shouldbe followed.The present study shows that two morphologicallysimilar species of brown algae can be easily classified bythe nrDNA ITS region sequences. 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