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Keywords:

  • Dasya enomotoi;
  • Dasyaceae;
  • molecular phylogeny;
  • morphology;
  • rbcL;
  • Rhodophyta;
  • taxonomy

Summary

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. References
  9. Supporting Information

A new red alga, Dasya enomotoi, is described from Japan. This species is characterized by having a large thallus consisting of an elongated axis and many, radially arranged, polysiphonous branches both of which are heavily corticated and densely covered with numerous, soft monosiphonous filaments. It is distinguished from several similar species by the combination of the following: (i) indistinct pericentral cells in transverse sections except near the apices, (ii) the presence of enlarged, inner cortical cells, (iii) radially arranged adventitious monosiphonous filaments, (iv) three-celled carpogonial branches, (v) six (sometimes five) tetrasporangia in each fertile segment of the stichidia, and (vi) three tetrasporangial cover cells that are not elongated longitudinally and usually not divided transversely. This species may have been identified as D. villosa Harvey by previous investigators in Japan.


Introduction

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. References
  9. Supporting Information

In Japan seven species and one variety of the red algal genus Dasya (Dasyaceae, Ceramiales) are known (Yendo 1916; Noda & Kitami 1971; Kajimura 1998; Yoshida 1998; Masuda et al. 2006, 2007; Yoshida & Yoshinaga 2010), including D. villosa Harvey. The species diversity of Dasya, however, is still insufficiently known. Two medium- to large-statured species identified as D. scoparia and D. villosa in Japan are poorly understood, because morphological features important in present-day taxonomy of the genus are entirely unknown (Yoshida 1998). Further critical studies are needed to clarify the status of these algae in Japan.

In this paper we describe a new species of Dasya that is large-statured and might have been included in the concept of D. villosa by previous investigators in Japan. In addition to morphological observations, the plastid-encoded large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (rbcL) gene sequences of our materials are reported in order to allow future comparisons with other species of Dasya.

Materials and Methods

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. References
  9. Supporting Information

Morphological observations

Specimens were collected at Yaeko-jima (34°20′36″N, 133°11′01″E), Innoshima Ohama (in Innoshima Island), Onomichi City, Hiroshima Prefecture, Japan, by Y. Yamagishi. Some specimens were dried as herbarium specimens, and portions (several branches) of these specimens and other specimens were fixed in 10% formalin in seawater for examinations (some of the latter specimens were later dried as herbarium specimens). The voucher specimens are deposited in the Herbarium of the Faculty of Science, Hokkaido University, Sapporo (SAP): (i) 21 July 2005, cystocarpic (SAP 106448), tetrasporangial (SAP 106449); (ii) 19 August 2005, cystocarpic (SAP 102124), tetrasporangial (SAP 102125); (iii) 31 July 2007, spermatangial (SAP 106450), cystocarpic (SAP 106451, 106452), tetrasporangial (SAP 106453); (iv) 4 July 2008, spermatangial (SAP 106454), cystocarpic (SAP 106455), tetrasporangial (SAP 106456); (v) 1 August 2008, spermatangial (SAP 106457), cystocarpic (SAP 106458–106463), tetrasporangial (SAP 106466–106470); and (vi) 1 September 2008, cystocarpic (SAP 106471), tetrasporangial (SAP 106472, 106473).

Small portions of axes or branches excised from formalin-preserved specimens were sectioned by hand are stained with 0.5% (w/v) cotton blue in a lactic acid/phenol/glycerol/water (1 : 1 : 1 : 1 [v/v]) solution and mounted in 30% Karo syrup.

We re-examined herbarium specimens of Dasya species, which were collected from Japan and adjacent waters and deposited in SAP. The following four specimens from three localities were identified as the alga in question and used to compile the algal distribution (the localities shown from north to south): (i) Izumozaki, Niigata Prefecture, 20 August 1910, leg. R. Kobayashi (herb. K. Yendo, as Dasya villosa); (ii) Shibagaki, Hakui-gun, Ishikawa Prefecture, August 1924, leg. Y. Yamada (SAP 021476, as Dasya sp.), August 1938, leg. M. Kumazawa (SAP 021335, as Dasya villosa); and (iii) Takamatsu, Kagawa Prefecture, 27 July 1939, leg. Y. Ujike (SAP 062255, as Dasya villosa). Specimens in Yendo's herbarium housed in SAP (herb. K. Yendo) are on permanent loan from the University Museum, University of Tokyo (TI).

rbcL analyses

Total DNA was extracted from seven samples (dried in silica gel or frozen and stored at −20°C) of Dasya enomotoi (Supporting Information Table S1) using a cetyl trimethylammonium bromide procedure (Apt et al. 1995).

Polymerase chain reaction (PCR) amplifications were carried out using Takara Ex Taq (Takara Bio, Shiga, Japan). We used three pairs of primers FH1-RH5, rbcL-Rh1-rbcS1, and FH1D-DarR4 for the PCR amplification, and these six primers with three internal primers (DarR3, FH440, FH911) for the sequencing reactions (Yamagishi & Masuda 2000; Hanyuda et al. 2004). The profile of PCR conditions were as follows: 30 cycles of denaturation at 95°C for 1 min, annealing at 54°C for 1 min, extension at 72°C for 2 min; and a final extension at 72°C for 10 min. PCR products were sequenced using a BigDye Terminator v1.1 Cycle Sequencing Kit (Applied Biosystems, Foster City, CA, USA) and an Applied Biosystems 3130 Genetic Analyzer (Applied Biosystems). The rbcL sequences were aligned manually and no insertion–deletion mutations were detected. Sequences of 14 species of the Dasyaceae were downloaded from GenBank and included in the alignment (Supporting Information Table S2). Ceramium brevizonatum var. caraibicum (Ceramiaceae) and Acrosorium polyneurum (Delesseriaceae) were used as outgroups. The alignment is available from the first author upon request.

Phylogenetic trees were inferred using the maximum likelihood (ML), maximum parsimony (MP) and Bayesian inference (BI). The ML analysis was implemented in PAUP* 4.0 b10 (Swofford 2002). The ML parameters were estimated using the program MODELTEST version 3.7 (Posada & Crandall 1998) using a hierarchical likelihood ratio test (α = 0.01). When the best sequence evolution model was determined, the ML tree search was performed using the estimated parameters with the following options: starting tree option = obtained by neighbor joining, and the tree-bisection-reconnection branch swapping algorithm (TBR). Bootstrap analysis based on 100 re-samplings of the dataset was calculated (TBR, full heuristic search option). The MP analysis was also performed with PAUP*. All sites were treated as unordered and equally weighted. Heuristic search option with random addition of sequences (100 replicates) and the TBR was used for tree searching. Bootstrap analysis (Felsenstein 1985) based on 2000 re-samplings of the dataset was calculated (10 random additions, TBR, full heuristic search). BI analysis using MrBayes v.3.2.1 (Huelsenbeck & Ronquist 2001) was run for 5 000 000 generations with a sample frequency of 100. Four Markov chain Monte Carlo chains were used. The first 1 250 000 generations were discarded as burn-in, and the remaining trees were used to calculate posterior probabilities at nodes.

Results

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. References
  9. Supporting Information

Our morphological and molecular analyses elucidated a new species, which we here propose:

Dasya enomotoi Yamagishi, Masuda et Abe, sp. nov

Thallus yellowish to brownish red, with a single terete, erect axis; reproductive axes 8–60 cm high, 1.5–3.0 mm in diameter at the lower and middle portion, with many, long, polysiphonous branches, heavily corticated except near the apices; pericentral cells five in each segment of the axis and branches, indistinct except near the apices by enlarged and protruded inner cortical cells between the pericentral cells; axis and branches densely covered with numerous monosiphonous filaments (pseudolateral filaments and adventitious monosiphonous filaments), but denuded below with age; monosiphonous filaments radially arranged, soft, mucilagenous, 2–4 mm long, subdichotomously branched two to five times in the proximal portion, 20–30 μm in diameter in the proximal segments, retaining the diameters towards distal segments, then gradually tapering to obtuse terminal segments 5–15 μm in diameter; ultimate ramuli of the monosiphonous filaments 1200–3400 μm long, with 14–31 segments. Frequently one sometimes two (rarely three) spermatangial branches formed on each fertile monosiphonous filament, with a monosiphonous pedicel of one to three (rarely four) segments, sometimes sessile; the fertile regions usually simple (rarely divided once or twice), narrowly conical, 200–700 μm (rarely 800–950 μm) long and 65–80 μm in diameter, consisting of 10–35 (rarely 40–45) segments. Carpogonial branches three-celled, spirally formed in three to six successive segments of young adventitious polysiphonous branches; cystocarps broadly urceolate, 900–1650 μm high (including a neck 100–350 μm high) and 950–1400 μm in diameter, each with an ostiole 150–350 μm in diameter. Frequently one, occasionally two tetrasporangial stichidia formed on each fertile monosiphonous filament, with a monosiphonous pedicel of one to three segments, sometimes sessile; the fertile regions of stichidia conical, 250–800 μm long and 125–150 μm in diameter, consisting of 8–27 segments, with six (sometimes five) sporangia in each segment, each with irregularly arranged, three postsporangial cover cells; mature sporangia 40–50 μm in diameter.

Holotype: Cystocarpic specimen deposited in the Herbarium of the Faculty of Science, Hokkaido University, Sapporo (SAP 106458, Fig. 1), Yaeko-jima, Innoshima Ohama, Onomichi City, Hiroshima Prefecture, in the Inland Sea of Japan, 1 August 2008, by Y. Yamagishi.

figure

Figure 1. Holotype specimen of Dasya enomotoi (cystocarpic plant, SAP 106458) collected at Yaeko-jima, Innoshima Ohama, Onomichi City, Hiroshima Prefecture on 1 August 2008: The thallus has an axis (arrow) and two branches (arrowheads) issuing near the holdfast.

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Etymology: The specific epithet honors Professor Emeritous of Kobe University, Dr Sachito Enomoto, in recognition of his contributions to the knowledge of marine benthic algae in the Inland Sea of Japan.

Japanese name: Setouchi-dajia (new name).

Habitat and vegetative structures

Thalli of D. enomotoi examined grow on a small island (Yaeko-jima) in the Inland Sea of Japan. The locality is relatively sheltered. Macroscopic thalli are present during the summer months. Individual thalli grow solitarily or gregariously on stones, rocks, bedrock, or stems of Sargassum sp. in the lower intertidal to upper subtidal zone.

Individual thalli are yellowish to brownish red in color and consist of a single terete erect axis that arises from a discoid holdfast 2.5–3.5 mm in diameter. Reproductive axes (Fig. 1) are 8–60 cm in height and 1–2 mm in diameter just above the holdfast, becoming gradually thicker upwards and reaching 1.5–3.0 mm at the lower to middle portions and gradually taper to the apices. Erect axes bear many, indeterminate, radially arranged, polysiphonous branches 3–40 cm long that produce branches of three or four orders.

The growth of the axes is sympodial. The subapical cell cuts off a lateral cell becoming a new apical cell, and the old apical cell subsequently develops into a pseudolateral. Pseudolaterals are one per axial cell (Fig. 7) and are arranged regularly in a two-fifths spiral manner.

figure

Figure 2–8. Dasya enomotoi. Material from the type locality. 2. Transverse section (TS) about 0.5 mm behind the apex of an axis: an axial cell, five pericentral cells and single- or two-layered (arrowheads) cortical cells are evident. 3. TS about 1 mm behind the apex: due to enlargement of inner cortical cells and their protrusion between the pericentral cells, this segment appears to have seven pericentral cells. 4. TS of the lower axis heavily corticated with slender (arrows) and enlarged cortical cells: note the pericentral cells are unclear. 5. Surface view near the apex of an axis: note that rhizoidal filaments (r) are cut off from pericentral cells. 6. Middle portion of a second order branch, bearing numerous monosiphonous filaments consisting of both pseudolaterals and adventitious monosiphonous filaments. 7. Two pseudolaterals (pl) near the apex originating from axial cells (a). 8. Young adventitious monosiphonous filament originating from a cortical cell.

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Except near the apices (Figs 2,3), the axes are heavily corticated by profusely developed rhizoidal filaments (Fig. 4). Initials of these rhizoidal filaments are cut off from the pericentral cells (Fig. 5) and the basal and suprabasal cells of pseudolaterals, develop basipetally. Inner cortical cells enlarge, and their sizes become the same size as or larger than the pericentral cells (Fig. 3). Some of the inner cortical cells protrude between the pericentral cells, and then such segments appear to have more than five pericentral cells (Fig. 3). Such enlargement and protrusion are found even 1–2 mm behind the apices of axes. In the lower axes slender cortical filaments develop between the central cell and the pericentral cells (Fig. 4). Thus, conspicuous development of cortical cells obscures the pericentral cells that are obvious in transverse sections only near the apices (about 500 μm behind the apex) (Fig. 2).

Each axis and its polysiphonous branches are densely covered with numerous, soft, mucilagenous, monosiphonous filaments (Fig. 6) that consist of pseudolateral filaments and adventitious monosiphonous filaments; however, the lower portions become denuded with age. Adventitious monosiphonous filaments develop from either pericentral cells or cortical cells (Fig. 8). Except in the uppermost portions of the axis and branches pseudolateral filaments cannot be distinguished from adventitious monosiphonous filaments that are formed early, because a thick cortical-cell layer hides their area of origin. However, adventitious monosiphonous filaments that are formed in later stages are obvious by their parental cortical cell (Fig. 8).

The following description is based on monosiphonous filaments on the middle mature portions of the thallus. Monosiphonous filaments are 2–4 mm long and are subdichotomously divided two to five times at intervals of two or three (sometimes to six) segments in the proximal portion; there is no branching in the middle to upper portions. The monosiphonous filaments are 20–30 μm in diameter in the proximal segments and of nearly uniform diameters and then tapering to obtuse terminal segments 5–15 μm in diameter. Mature monosiphonous filaments have 4–12, simple, ultimate-order ramuli, which are 1200–3400 μm in length and consist of 14–31 segments. Length : diameter ratios of these segments are 4–10 (sometimes to 14). Intercalary cell divisions are not found in monosiphonous filaments.

Reproductive structures

Spermatangial branches develop on monosiphonous filaments, usually one sometimes two (rarely three) per monosiphonous filament. The fertile portions are generally simple, narrowly conical (Fig. 9), 200–700 μm (rarely 800–950 μm) in length by 65–80 μm in diameter and consist of 10–35 (rarely 40–45) segments. Spermatangial branches are rarely with one or two sterile monosiphonous filaments in lateral position (Fig. 9) or rarely branched (Fig. 10). Each spermatangial branch is usually provided with a monosiphonous pedicel and a sterile tip. The pedicel consists of one to three (rarely four) cells. The sterile tip is usually simple, consisting of 3–10 (sometimes 12–26) segments, rarely with laterals (Fig. 11).

figure

Figure 9–14. Dasya enomotoi. Material from the type locality. 9. Two spermatangial branches formed on a fertile monosiphonous filament; with a sterile lateral branch (arrow). 10. Divided spermatangial branch. 11. Branched tip of a spermatangial branch. 12. Three-celled carpogonial branch (arrowheads) formed near the apex of a polysiphonous branch. 13. Young cystocarp beginning to form a pericarp. 14. An immature cystocarp (left) laterally arranged on the parental short polysiphonous branch and a mature cystocarp (right) appearing to be stalked on the parental branch.

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Carpogonial branches are formed on young polysiphonous branches of 200–300 μm in length, in three to six successive segments in a spiral manner. Each carpogonial branch is laterally cut off from a fertile pericentral cell and composed of three cells (Fig. 12), provided with two groups of sterile cells. After presumed fertilization, a pericarp begins to develop around a developing gonimoblast (Fig. 13). Developing cystocarps are clearly lateral and sessile on the parental polysiphonous branch (Fig. 14). Segments of the parental polysiphonous branch become lengthened by the elongation of the central and pericentral cells and thickened by the production of cortical cells as the cystocarp develops, so that the cystocarp is located in the terminal position (Fig. 14). Mature cystocarps are broadly urceolate, 900–1650 μm high (including a neck 100–350 μm high) and 950–1400 μm in diameter, having an ostiole 150–350 μm in diameter (Fig. 14).

Tetrasporangial stichidia develop on fertile monosiphonous filaments. Tetrasporangial stichidia are usually provided with a monosiphonous pedicel and a monosiphonous sterile tip (Figs 15,16). The pedicel consists of one to three segments. The sterile tip is usually simple (rarely forming one or two laterals) and consists of usually 3–12 (sometimes 18–24) segments. Each of the polysiphonous segments produces six (sometimes five) tetrasporangia (Fig. 17), although one or two pericentral cells of the proximal segment sometimes remain vegetative. The fertile portions consist of 8–27 polysiphonous segments that are conical, 250–800 μm long and 125–150 μm in diameter. A fertile segment of a few stichidia bears either a fertile (Fig. 16) or sterile lateral. Each tetrasporangium has three cover cells that are ovate, elliptic or sometimes rectangular and 18–28 μm long by 8–14 μm wide in surface view (Fig. 18), rarely divided once transversely. The cover cells can envelop less than one fourth of the mature sporangium or do not envelop it at all (Fig. 18). Mature tetrasporangia have tetrahedrally arranged spores (40–50 μm in diameter).

figure

Figure 15–18. Dasya enomotoi. Material from the type locality. 15. Tetrasporangial stichidium formed on a fertile monosiphonous filament. 16. Branched tetrasporangial stichidium. 17. Transverse section of a younger portion of the stichidium showing young six tetrasporangia in a fertile segment. 18. Close-up of a tetrasporangial stichidium: c, cover cell; s, stalk cell; t, tetrasporangium: note that the cover cells do not envelop the tetrasporangium.

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rbcL analysis

Seven samples including male, female and tetrasporangial plants of D. enomotoi (Supporting Information Table S1) were sequenced for the rbcL genes. The phylogenetic tree obtained from the ML analysis (-ln L = 6435.48630) is presented in Fig. 19. The identical sequences of D. enomotoi were excluded from the analysis. For the ML method, likelihood settings from the best-fit model (GTR + I + G) were selected (nucleotide frequencies A = 0.3178, C = 0.1393, G = 0.2102, T = 0.3327; substitution-rate; AC = 2.5727, AG = 5.0210, AT = 5.9816, CG = 3.7584, CT = 24.9235, GT = 1; proportion of invariable sites = 0.4634; gamma distribution with shape parameter = 1.0262).

figure

Figure 19. Phylogenetic tree of Dasya species inferred from maximum likelihood (ML) analysis of partial rbcL gene sequences. Ceramium brevizonatum var. caraibicum and Acrosorium polyneurum were used as outgroups. Numbers on the branches indicate ML bootstrap/ maximum parsimony (MP) bootstrap/Bayesian posterior probabilities, respectively. Values >50% bootstrap and >0.7 posterior probabilities are shown.

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In the MP analysis, one most-parsimonious tree (959 steps) was obtained (not shown). The topologies of the ML, MP and BI trees were almost congruent, except for the clades that were supported with low bootstrap values and posterior probabilities. Dasya enomotoi formed a strongly supported clade in all analyses.

Observations of herbarium specimens

Yendo's voucher specimens deposited in his herbarium housed in SAP were examined: (i) Takayama, Miyagi Prefecture (as Rikuzen Prov.) (leg. Miss Wainwright (No. 4); and (ii) Izumozaki, Niigata Prefecture (as Echigo Prov.), 20 August 1910, leg. R. Kobayashi (No. 11). The critical features of D. enomotoi were difficult to detect in these old herbarium specimens. The Izumozaki specimen was denuded below, which fitted D. enomotoi. The Takayama specimen seemed to belong to a different alga judging from the presence of monosiphonous filaments throughout the thallus. Similarly, specimens deposited in the general herbarium in SAP were examined, and three specimens from two localities were referable to D. enomotoi: (i) Shibagaki, Hakui-gun, Ishikawa Prefecture, August 1924, leg. Y. Yamada (SAP 021476, as Dasya sp.), August 1938, leg. M. Kumazawa (SAP 021335, as Dasya villosa); and (ii) Takamatsu, Kagawa Prefecture, 27 July 1939, leg. Y. Ujike (SAP 062255, as Dasya villosa).

Discussion

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. References
  9. Supporting Information

New observations of a Japanese Dasya, which may have been misidentified as D. villosa, reveal that this is not identical with any described species, thus this is newly described as D. enomotoi. Dasya enomotoi is characterized by having the significant features in common with D. atropurpurea Vroom, D. baillouviana (S. Gmelin) Montagne, D. extensa Sonder ex Kützing, D. trichophora Millar and D. villosa as follows: the thallus consisting of an elongated axis and many, radially arranged, polysiphonous branches both of which are heavily corticated and densely covered with numerous, soft, monosiphonous pseudolateral and adventitious filaments (Millar 1990; Schneider & Searles 1991; Parsons & Womersley 1998) (Table 1). However, D. baillouviana differs substantially from D. enomotoi in the distinct pericentral cells and four-celled carpogonial branches (Rosenberg 1933; Coppejans 1983; Littler & Littler 2000). D. extensa is distinguished from D. enomotoi by the absence of enlarged, inner cortical cells, the presence of intercalary cell divisions in monosiphonous filaments, and the production of five tetrasporangia in each fertile segment of stichidia (Parsons & Womersley 1998). Intercalary cell divisions are known to take place in monosiphonous filaments of a few species including D. extensa (Parsons & Womersley 1998; Masuda et al. 2003). D. trichophora differs from D. enomotoi in its unique, distichous arrangement of adventitious monosiphonous filaments and its longitudinally elongated tetrasporangial cover cells (Millar 1990). D. villosa differs from D. enomotoi in the distinct pericentral cells, slender spermatangial branches, and longitudinally elongated tetrasporangial cover cells (Parsons & Womersley 1998).

Table 1. A morphological comparison of six species of Dasya with an elongated axis and radially arranged branches that are heavily corticated and densely covered with numerous, soft monosiphonous filaments1
 Dasya enomotoiDasya atropurpureaDasya baillouviana4Dasya extensaDasya trichophoraDasya villosa
  1. Information from: (1) Vroom 2005; (2) Børgesen 1919 as D. pedicellata C. Agardh; (3) Rosenberg 1933 as D. elegans (Martens) C. Agardh); (4) Coppejans 1983; (5) Millar 1990; (6) Schneider & Searles 1991, (7) Parsons & Womersley 1998; (8) Littler & Littler 2000; (9) this study. 1The term ‘monosiphonous filaments’ used here includes both monosiphonous pseudolateral filaments and adventitious monosiphonous filaments. 2One or two pericentral cells of the proximal segments sometimes remain vegetative. 3, 5The shapes of the tetrasporangial cover cells are judged from the figures (Vroom 2005, fig. 24; Millar 1990, fig. 60D). 4As the conspecificity of Atlantic and other populations of this species are not elucidated, information cited here is taken from the literature based on the Atlantic specimens including the Mediterranean Sea (type locality).

Height of axes8–60 cm13–41 cm20–90 cm10–130 cmUp to 19 cm10–40 cm
Diameter of axes1–3 mm1.5–3.5 (–5.5) mm2–3 (–6) mm2–6 mm1 mm1–3 mm
Distinctiveness of pericentral cells in transverse sectionIndistinct except near apicesUnknownDistinctIndistinct except for the younger portionIndistinct except for the younger portionDistinct
Enlarged, inner cortical cellsPresentUnknownPresentAbsentUnknownPresent
Length of monosiphonous filaments12–4 mm2–4 mm2–8 (–14) mm1–6 mmUp to 2 mm1–8 mm
Diameter of monosiphonous filaments120–30 μm proximally and 5–15 μm distally9–25 μm proximally and 2–10 μm distally10–40 μm proximally and 5–12 μm distally30–45 μm proximally and 10–35 μm distallyUp to 37 μm30–60 μm proximally and 12–25 μm distally
Intercalary cell divisions in monosiphonous filaments1AbsentOccasionalUnknownPresentUnknownAbsent
Disposition of adventitious monosiphonous filamentsRadialRadialRadialRadialDistichousRadial
Denuded lower portionPresentPresentPresentAbsentAbsentPresent
Diameter of spermatangial branches65–80 μm35–50 μm60–75 μm75–90 μmUnknown40–55 μm
Carpogonial branchThree-celledThree-celledFour-celledFour-celledUnknownThree-celled
Diameter of cystocarps950–1650 μm1100–1500 μmUp to 1100 μm700–1600 μmUp to 1200 μm630–880 μm
Diameter of tetrasporangial stichidia125–150 μmUp to 165 μm80–160 μm90–130 μmUp to 200 μm100–190 μm
Number of tetrasporangia per fertile segmentSix (sometimes five)2Four or fiveFiveFiveSixSix
Number of tetrasporangial cover cells per tetrasporangiumThreeThreeTwo or threeTwo or threeThreeThree (rarely four)
Shape of tetrasporangial cover cellsNot elongatedLongitudinally elongated3Not elongatedNot elongatedLongitudinally elongated5Longitudinally elongated
Transverse division of tetrasporangial cover cellsRarely presentUnknownOften presentOften presentAbsentAbsent
Geographical distributionJapanHawaiiAtlantic coastsAustraliaAustraliaAustralia
Reference812, 3, 4, 6, 8757

The distinctiveness of pericentral cells in transverse sections of axes and branches is considered to be one of the critical features among the species of Dasya (Parsons & Womersley 1998; Masuda et al. 2007). This character is often correlated to the degree of cortication (Masuda et al. 2007). Pericentral cells may be obscured by the following two patterns: (i) slender cortical filaments develop between the pericentral cells as in the case of D. boninensis (Masuda et al. 2007); and (ii) inner cortical cells enlarge (becoming the same as or larger than pericentral cells), some of which protrude between pericentral cells as in the case of D. wilsonis (Parsons & Womersley 1998). Furthermore, a mixed pattern of these two may be present in D. enomotoi. Thus, the presence/absence of enlarged, inner cortical cells may have taxonomic significance.

The production of the four-celled carpogonial branches was thought to be constant in Dasya as well as the Dasyaceae (Parsons 1975) before the discovery of the three-celled carpogonial branches in D. villosa (Parsons & Womersley 1998). Recently, Vroom (2005) reported three-celled carpogonial branches for D. atropurpurea, which was newly described from the Hawaiian Islands. This Hawaiian species also has large axes (13–45 cm long and 1.5–5.5 mm thick), but differs from D. enomotoi in the occasional production of adventitious monosiphonous filaments, four or five tetrasporangia per fertile segment of the stichidium and longitudinally elongated tetrasporangial cover cells (Vroom 2005).

Each species of Dasya produces a definite number of tetrasporangia per fertile stichidial segment, ranging from four to eight, which is generally used as a diagnostic feature (Weber-van Bosse 1913; Parsons 1975; Parsons & Womersley 1998; Ballantine 2000; López-Piñero & Ballantine 2001; Masuda et al. 2003, 2007; Ballantine & Aponte 2004). The longitudinally elongated tetrasporangial cover cells characterizes some species such as D. corymbifera J. Agardh (Abbott 1999) and D. murrayana Abbott et Millar (Masuda et al. 2007), in addition to two species shown in Table 1. Børgesen (1945) reduced D. villosa to the synonymy of D. baillouviana (as D. pedicellata C. Agardh) because he could not find clear differences between them. However, these two species can be distinguished by the number of cells in the carpogonial branches and the number of tetrasporangia per fertile stichidial segment, in addition to the shape of tetrasporangial cover cells (Table 1).

The rbcL tree (Fig. 19) shows that D. enomotoi is sister to D. iridescens collected from Tanzania (FM993098). However, D. iridescens is distinguished from D. enomotoi by having small thalli (up to 7 cm long), a distinct iridescence and longitudinally elongated tetrasporangial cover cells (Schlech 1990; Abbott 1999).

Yendo (1916) first reported D. villosa from Japan based on specimens collected at two localities, Rikuzen Prov. and Echigo Prov. Although the voucher specimens deposited in Yendo's herbarium and specimens in SAP were examined, characters of pericentral cells and the arrangement of tetrasporangial cover cells were difficult to detect. But, any specimen obviously identical to D. villosa was not found. Instead four specimens referable to D. enomotoi were found in specimens previously identified as D. villosa or Dasya sp. Thus, we consider that previous records of D. villosa from Japan are doubtful and that D. enomotoi might have been included in the concept of D. villosa in Japan.

Acknowledgments

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. References
  9. Supporting Information

We are very grateful to Dr Kazuhiro Kogame for his reading of a draft of the manuscript and to Mr Wataru Okabe and Mr Yoshiaki Hirai for their help in samplings and molecular experiments. We also thank Dr Yasuhiko Miwa for his technical assistance and helpful discussion.

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  2. Summary
  3. Introduction
  4. Materials and Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. References
  9. Supporting Information
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Supporting Information

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. References
  9. Supporting Information
FilenameFormatSizeDescription
pre12038-sup-0001-tables1.doc40K

Table S1. List of specimens of Dasya enomotoi examined.

pre12038-sup-0002-tables2.doc43K

Table S2. List of species for the rbcL analysis.

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