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Electronic Flora of South Australia Genus Fact Sheet

Genus DASYA C. Agardh 1824: 211, nom. cons.

Phylum Rhodophyta – Order Ceramiales – Family Dasyaceae

Thallus erect, radially (occasionally more or less bilaterally) branched, sympodially developed; most species mucilaginous. Sympodial axes terete, with 5 (rarely 4) pericentral cells cut off in a circular sequence and with each or every second segment bearing a pseudolateral. Axes ecorticate or corticate by rhizoidal filaments. Pseudolaterals monosiphonous, rhodoplastic, persistent, usually becoming branched subdichotomously and sometimes becoming polysiphonous at their base. Adventitious monosiphonous filaments may arise from the pericentral cells and/or the cortical cells in some species.

Lateral sympodial axes develop from basal cells of the pseudolaterals or adventitious monosiphonous filaments.

Reproduction: Gametophytes usually dioecious. Procarps occur spirally on successive segments of the sympodial axes or on 1–3 basal cells of pseudolaterals. The fertile segment bears five pericentral cells formed in a circular sequence, the third pericentral cell producing the procarp which consists of a 4 (rarely 3)-celled carpogonial branch and two groups of sterile cells originating from the supporting cell. No pericarp initials are present at fertilization. The fertilized carpogonium cuts off 1 or 2 connecting cells, one fusing with the auxiliary cell cut off from the supporting cell. A fusion cell is formed by the auxiliary cell fusing with the central cell of the fertile segment, and the supporting cell, adjacent pericentral cells and basal gonimoblast cells may also fuse with this fusion cell. Gonimoblasts monopodial, branched, with carposporangia maturing in chains or terminally. Cystocarps stalked or sessile, often with a prominent neck. Spermatangial branches formed from a branch of the monosiphonous portions of pseudolaterals or adventitious filaments, with four pericentral cells cut off in an alternating sequence, dividing several times to give spermatangial initials and outer spermatangia.

Tetrasporangia formed in stichidia on monosiphonous, rarely polysiphonous, parts of pseudolaterals or adventitious filaments, with 4–7 pericentral cells cut off in an alternating sequence, first dividing to give a tetrasporangium and a stalk cell. The stalk cell cuts off 2–4 post-sporangial cover cells which may divide again but never completely cover the tetrasporangium. Tetrasporangia tetrahedrally divided, 4–7 each segment.

Type species: D. elegans (Martens) C. Agardh. [= D. baillouviana (Gmelin) Montagne. See Dixon & Irvine 1970, p. 480].

Taxonomic notes: A genus of more than 80 species, widely distributed in temperate and tropical seas, and particularly well represented on the coasts of southern Australia. Dasya differs from Heterosiphonia in having usually 5 (rarely 4) pericentral cells per vegetative segment and radial branching at the apices.

The generic key in de Jong et al. (1997, pp. 422, 423) covers several genera which are compared in their Table 1. While some groups of southern Australian Dasya species are relatively distinctive, it seems best to keep them all under Dasya in view of the variation in these characters. The groups involved are:

D. villosa - D. extensa complex, with abundant adventitious filaments arising from cortical cells. This group includes also the closely related D. kraftii and D. haldockii, and the less closely related D. haffiae and D. wilsonis which have a rather different habit to the first 4 species, more similar to some species not bearing adventitious filaments.

D. tenuis, D. capillaris and D. hookeri, which have pseudolaterals (and lesser branches) borne mostly on every second segment rather than on each segment; however this is not consistent, and branching from every and from each third segment does occasionally occur. Branching 2 or more segments apart is a characteristic of Heterosiphonia, but the above Dasya species are radially rather than distichously branched.

3. D. haffiae, which is usually complanately and bilaterally branched, but this is a secondary development of a spirally branched apex where usually the first and second pseudolaterals become polysiphonous lateral branches and 3, 4 and 5 remain as monosiphonous pseudolaterals; occasionally all become polysiphonous and the thallus branching is irregular.

Several other species of Dasya than those described below occur on southern Australian coasts, but material is inadequate for their determination; specimens have been segregated in the AD herbarium.

Two other species (D. elongata and D. frutescens) occur on the west coast of Western Australia, extending north from Safety Bay; at present there is no satisfactory evidence that they occur in the southern Australian region, and any references to them in this region probably apply to other species (e.g. Reinbold 1899, p. 49).

Dasya elongata Sonder 1845: 53; 1848: 179; 1881: 36. J. Agardh 1863: 1225; 1890a: 98. De Toni 1903: 1196; 1924: 442. Harvey 1847: 63, pl. 23; 1855a: 524; 1863, synop.: xxiii. Huisman & Walker 1990: 427. Kützing 1849: 797; 1864: 24, p1. 66a-c. Lucas 1912: 158. Lucas & Perrin 1947: 313. Parsons 1975: 591. Silva et al. 1996: 435.

Dasya frutescens Harvey 1855a: 542; 1863, synop.: xxiii. J. Agardh 1863: 1225; 1890a: 97. De Toni 1903: 1194. Huisman & Walker [990: 427. Kützing 1864: 24, pl. 67d-g. Lucas 1912: 158. Silva et al. 1996: 436. Sonder 1881: 36.

These 2 species are closely related but appear to differ in habit, in terminal filaments of pseudolaterals (usually longer and slenderer in D. frutescens) and in stichidia of D. elongata having 5 tetrasporangia per whorl but D. frutescens only 4.

New, liquid preserved, collections of these species are needed to clarify their features.

SPECIES CREDITED TO DASYA, NOW REFERRED TO OTHER GENERA

The following names are not otherwise referred to in this account of the Dasyaceae.

Dasya adunca J. Agardh (1890a, p. 112) from King George Sound, W. Aust., lectotype LD, 44372, isolectotypes LD, 44369, 44370, L, 940. 347...248, MEL, 1006689, is Thaumatella disticha (Falkenberg) Kylin (1956, p. 511), now Thaumatella adunca (J. Agardh) Parsons & Womersley, comb. nov.

Dasya archeri Harvey (1859b, p. 304) from Tasmania (W. Archer), lectotype in Herb. Harvey, TCD, also referred to as Heterosiphonia archeri (Harvey) De Toni (1903, p. 1219) belongs to the Dasyclonium incisum complex.

Dasya bolbochaete Harvey (1844, p. 434) from Georgetown, Tas., holotype Gunn 1264 in Herb. Hooker, BM, is Doxodasya bolbochaete (Harvey) Falkenberg (1901, p. 538).

Dasya dictyuroides J. Agardh (1890a, p. 111, pl. 3 fig. 5), holotype from Western Port, Vic. (Wilson 66, 7.i.1885; LD, 44358) is Wilsonaea dictyuroides (J. Agardh) Schmitz (1893, p. 231). It is characterised by transversely divided pericentral cells, by lower adherent walls at the subdichotomies of the monosiphonous rhodoplastic filaments, stichidia with whorls of 4 tetrasporangia, but doubtfully by sympodial apices. Detailed study of its relationships is needed.

Dasya feredayae Harvey (1859b, p. 303), lectotype Harvey, Alg. Aust. Exsicc. 220J from Georgetown, Tas., in Herb. Hooker, BM, is Micropeuce feredayae (Harvey) Kylin (1956, p. 511).

Dasya harveyi Kützing (1864, p. 26, pl. 71 e,f), based on Harvey, Alg. Aust. Exsicc. 216A as D. lallemandii Harvey, holotype in Herb. Sonder, MEL, 608855, is a later homonym of D. harveyi Ashmead ex Harvey (1858, p. 127, pl. 50A), which when used by Schmitz (1893, p. 223) as Lophocladia harveyi is regarded as a new name.

Dasya lallemandii var. gracilis J. Agardh (1863, p. 1231), based on Harvey, Alg. Aust., Exsicc. 216a, holotype in LD, 42138, is Lophocladia harveyi.

Dasya lenormandiana J. Agardh (1863, p. 1238), based on a specimen from Glenelg R., Vic. (Herb. Lenormand), in LD, 42095, is Doxodasya lenormandiana (J. Agardh) Schmitz (1893, p. 220).

Dasya Proxima Harvey (1855a, p. 542), from King George Sound, W. Aust., holotype in Herb. Harvey, TCD (Tray. Set 336) is probably a species of Micropeuce.

Dasya sarcocaulon Harvey (1863, pl. 278), from Freemantle, W. Aust., lectotype Clifton 82 in Herb. Harvey, TCD, is Micropeuce sarcocaulon (Harvey) Kylin (1956, p. 511).

Dasya spyridioides Falkenberg (1901, p. 626) is based on a specimen of Wilson called Spyridia biannulata; the type has not been located. Falkenberg's description refers to one tetrasporangium per segment and the species is likely to be one of the Lophothalieae, probably a Micropeuce.

Dasya tenera Harvey (1855a, p. 543), from Freemantle, W. Aust., lectotype in Herb. Harvey, TCD, is Sarcotrichia tenera (Harvey) Womersley & Shepley (1959, p. 209).

Dasya urceolata Harvey ex J. Agardh (1863, p. 1207), from Port Fairy, Vic, lectotype Harvey, Alg. Aust. Exsicc. 217D, in Herb. Harvey, TCD, is Haplodasya urceolata (Harvey ex J. Agardh) Parsons (1975, p. 672, figs 34, 35, 47A).

Dasya verticillata Harvey (1844, p. 434), from Georgetown, Tas., holotype Gunn 1306 in Herb, Harvey, TCD, is Lophothalia verticillata (Harvey) Kützing (1849, p. 797).

References:

AGARDH, C.A. (1824). Systema Algarum. (Berling: Lund.)

AGARDH, J.G. (1863). Species Genera et Ordines Algarum. Vol. 2, Part 3, pp. 787–1291. (Gleerup: Lund.)

AGARDH, J.G. (1890a). Till algernes systematik. Acta Univ. lund. 26(3), 1–125, Plates 1–3.

DE JONG, Y.S.D.M., PRUD'HOMME VAN REINE, W.F. & LOKHORST, G.M. (1997). Studies on Dasyaceae II. A revision of the genera Eupogodon and Dipterocladia gen. nov. (Ceramiales, Rhodophyta). Bot. Mar 40, 421–450.

DE TONI, G.B. (1903). Sylloge Algarum omnium hucusque Cognitarum. Vol. 4. Florideae. Sect. 3, pp. 775–1521 + 1523–1525. (Padua.)

DIXON, P.S. & IRVINE, L.M. (1970). Miscellaneous notes on algal taxonomy & nomenclature. III. Bot. Notiser 123, 474–487.

FALKENBERG, P. (1901). Die Rhodomelaceen des Golfes von Neapel und der angrenzenden Meeres-abschnitte. Fauna und Flora des Golfes von Neapel. Monogr. 26. (Friedlander: Berlin.)

HARVEY, W.H. (1844). Algae of Tasmania. Lond. J. Bot. 3, 428–454.

HARVEY, W.H. (1847). Nereis Australis, pp. 1–64, Plates 1–25. (Reeve: London.)

HARVEY, W.H. (1855a). Some account of the marine botany of the colony of Western Australia. Trans. R. Jr. Acad. 22, 525–566.

HARVEY, W.H. (1858). Phycologia Australica. Vol. 1, Plates 1–60. (Reeve: London.)

HARVEY, W.H. (1859b). Algae. In Hooker, J.D., The Botany of the Antarctic Voyage. III. Flora Tasmaniae. Vol. II, pp. 282–343, Plates 185–196. (Reeve: London.)

HARVEY, W.H. (1863). Phycologia Australica. Vol. 5, Plates 241–300, synop., pp. i-lxxiii. (Reeve: London.)

HUISMAN, J.M. & WALKER, D.I. (1990). A catalogue of the marine plants of Rottnest Island, Western Australia, with notes on their distribution and biogeography. Kingia 1, 349–459.

KÜTZING, F.T. (1849). Species Algarum. (Leipzig.)

KÜTZING, F.T. (1864). Tabulae Phycologicae. Vol. 14. (Nordhausen.)

KYLIN, H. (1956). Die Gattungen der Rhodophyceen. (Gleerups: Lund.)

LUCAS, A.H.S. & PERRIN, F. (1947). The Seaweeds of South Australia. Part 2. The Red Seaweeds. (Govt Printer: Adelaide.)

LUCAS, A.H.S. (1912). Supplementary list of the marine algae of Australia. Proc. Linn. Soc. N.S.W. 37, 157–171.

PARSONS, M.J. (1975). Morphology and taxonomy of the Dasyaceae and Lophothalieae (Rhodomelaceae) of the Rhodophyta. Aust. J. Bot. 23(4), 549–713.

REINBOLD, T. (1899). Meeresalgen von Investigator Street (Slid Australien), gesammelt von Miss Nellie Davey (Waltham, Honiton). Hedwigia 38, 39–51.

SCHMITZ, F. (1893). Die gattung. Lophothalia, J. Ag. Ber deutsch. Bot. Ges. 11, 212–232.

SILVA, P.C., BASSON, P.W. & MOE, R.L. (1996). Catalogue of the Benthic Marine Algae of the Indian Ocean. (University of California Press: Berkeley, Los Angeles & London.)

SONDER, O.G. (1845). Nova Algarum genera et species, quas in itinere ad oras occidentales Novae Hollandiae, collegit L. Preiss, Ph.Dr. Bot. Zeit. 3, 49–57.

SONDER, O.W. (1881). In Mueller, F., Fragmenta Phytographiae Australiae. Supplementum ad volumen undecinum: Algae Australianae hactenus cognitae, pp. 1–42, 105–107. (Melbourne.)

WOMERSLEY, H.B.S. & SHEPLEY, E.A. (1959). Studies on the Sarcomenia group of the Rhodophyta. Aust. J. Bot. 7, 168–223.

The Marine Benthic Flora of Southern Australia Part IIIC complete list of references.

Author: M.J. Parsons and H.B.S. Womersley

Publication: Womersley, H.B.S. (24 December, 1998)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIC. Ceramiales – Ceramiaceae, Dasyaceae
©State Herbarium of South Australia, Government of South Australia

KEY TO SPECIES OF DASYA

1. Adventitious monosiphonous filaments plentiful between the pseudolaterals

2

1. Adventitious monosiphonous filaments absent (or rare) between the pseudolaterals

7

2. Pseudolaterals and adventitious monosiphonous filaments soft, branching only basally and at narrow angles, always ending in a lax filament

3

2. Pseudolaterals and adventitious monosiphonous filaments rigid, branches patent, usually ending with an acute apex (rarely with a lax filament)

6

3. Pseudolaterals and adventitious monosiphonous filaments gradually and evenly attenuate from their basal cells*; diameter of the basal cells usually less than twice that of the cell after the last subdichotomy

4

3. Pseudolaterals and adventitious monosiphonous filaments distinctly attenuate from their basal cells; diameter of the basal cells usually more than twice that of the cell after the last subdichotomy

5

4. Pseudolaterals and adventitious filaments usually with lower subdichotomies (1–) 2–3 (–5) cells apart, with no cell pairs (due to intercalary cell divisions) in the mature filaments; pericentral cells usually prominent in transverse sections of corticated axes with no or few internal rhizoids between them; cover cells in stichidia irregularly rectangular, palisade-like, sometimes subdividing

D. villosa

4. Pseudolaterals and adventitious filaments with no or few lower subdichotomies, (1–) 4–9 (–18) cells apart, with cell pairs (due to the intercalary cell divisions) occasional in the filaments; pericentral cells not conspicuous in transverse sections of corticated axes, or if apparent then usually with extensive rhizoid development between them; cover cells in stichidia irregular in shape, usually isodiametric

D. extensa

5. Basal cells of monosiphonous filaments 45–65 µm in diameter; pairs of shorter cells occasionally present in ultimate branches of mature filaments, indicating recent intercalary cell divisions; spermatangial branches ovoid-ellipsoid with a terminal unbranched filament; (4–) 5 pericentral cells and tetrasporangia per segment in stichidia

D. kraftii

5. Basal cell of monosiphonous filaments (40–) 50–80 µm in diameter; no (or very rare) pairing of cells in mature filaments; spermatangial branches elongate-cylindrical; (5–) 6–7 pericentral cells and tetrasporangia per segment in stichidia

D. baldockii

6. Frond more or less complanately branched, with percurrent axes and regular, subdistichous, branching of several orders; monosiphonous filaments radially arranged, subdichotomous, divaricate, curved, basal and lower cells 20–35 (–45) .tm in diameter

D. haffiae

6. Frond with terete, irregular and distant branches, not complanate, without a percurrent axis and without short laterals; monosiphonous filaments simple to (usually) 2–3 times subdichotomous, mostly 50–60 µm in diameter, ends subulate

D. wilsonis

7. Pseudolateral filaments coarse, simple or basally branched once or twice, curved, rigid, usually tapering to a point, (80–) 100–250 µm in diameter with cells L/D 1–3, longer in younger filaments

8

7. Pseudolateral filaments slender to moderately robust, basally branched several times, rigid to lax, 20–100 µm in diameter with cells L/D (0.75–) 2–8

9

8. Axes slender to moderate, lightly corticated near the apices with pericentral cells visible in side view for many segments from the apices, and with pseudolateral filaments along the branches; stichidia borne on monosiphonous pedicels

D. ceramioides

8. Axes robust, heavily corticated, with pericentral cells visible in side view only close to the apices, and with dense clusters of pseudolateral filaments at ends of short laterals on otherwise bare branches; stichidia borne on polysiphonous pedicels

D. scopulifera

9. Axes and lateral branches heavily to moderately corticated, with the pericentral cells visible in side view in young laterals only near the apices

10

9. Axes and lateral branches only lightly corticated, with the pericentral cells visible in side view in young and medium branches for very many (usually over 30) segments from the apices

17

10. Pseudolaterals divaricate, somewhat rigid, with many branches divergent at 45° or greater, branched throughout every 1–2 cells and without long, unbranched, tapering ends; pericentral cells usually remaining clearly visible in transverse section of older axes, with no or limited rhizoid development

11

10. Pseudolaterals usually lax, not divaricate, with branching mostly at distinctly less than 45° divergence and confined to the lower part of the pseudolateral which terminates in long, unbranched filaments, usually gently to distinctly tapering (except D. clavigera); pericentral cells remaining distinct or usually becoming separated and indistinguishable in size in transverse sections of older axes due to extensive rhizoid development

12

11. Lateral branches occurring mostly two segments apart and tending to be subdistichously arranged; pseudolaterals moderately rigid, forming tufts at ends of branches, without an acute apex, filaments 40–50 (–60) µm in diameter near base of pseudolateral with cells L/D 3–5

D. cliftona

11. Lateral branches irregularly radial and often distantly arranged; pseudolaterals on each segment, clothing branches except in older parts, rigid, with (2–) 3–5 (–8) cells after last subdichotomy tapering to an acute apex, filaments (40–) 50–70 (–75) µm in diameter with cells L/D (1–) 2–2.5

D. divergens

12. Branched regions of mature pseudolateral filaments less than 45 µm in diameter

13

12. Branched regions of mature pseudolateral filaments more than (45–) 55 µm in diameter

15

13. Pseudolateral filaments very slender, 12–20 µm in diameter with cells L/D (2–) 3–4, becoming corticated at base of the pseudolateral; thallus much branched, dark brown

D. comata

13. Pseudolateral filaments (17–) 20–40 µm in diameter with cells L/D 2.5–8, not corticated at base of the pseudolateral; thallus with long branches bearing lateral tufts of pseudolaterals, medium to dark red

14

14. Thallus with mainly long branches from near the subdichotomous base, fringed with short pseudolateral tufts; pseudolateral filaments 30–40 µm in diameter with cells L/D (2–) 2.5–3 where branched, L/D (2–) 3–4 near ends

D. crinita

14. Thallus with long branches bearing numerous laterals with lax pseudolateral tufts near their ends; pseudolateral filaments (17–) 20–30 µm in diameter with cells L/D 2–4 where branched, L/D 6–8 near ends

D. hapalathrix

15. Thallus robust, usually with short lateral branches on strongly developed axes; pseudolateral filaments usually slightly greater in diameter several cells above the base, then ending or tapering but not into a long, slender, hair; stichidia with 6 pericentral cells and sporangia per segment

D. clavigera

15. Thallus robust to moderately slender, usually with well developed lateral branches; pseudolateral filaments tapering from basal cells either gently or rapidly into long, slender, hair-like ends; stichidia with 4 or 5 pericentral cells and sporangia per segment

16

16. Thallus moderately slender, much and irregularly spirally branched with long laterals; pericentral cells remaining distinct in transverse section; mature pseudolaterals with basal cells 35–65 µm in diameter; stichidia with four pericentral cells and tetrasporangia per segment

D. quadrispora

16. Thallus robust with heavily corticated axes bearing laterals giving a narrowly to broadly conical outline; mature pseudolaterals with basal cells (50–) 95–130 µm in diameter; stichidia with five pericentral cells and sporangia per segment

D. naccarioides

17. Pseudolaterals mostly on every segment of branches; stichidia with 5 pericentral cells and sporangia per segment

18

17. Pseudolaterals mostly on every second segment of branches; stichidia with 4 or 6 pericentral cells and sporangia per segment

19

18. Pseudolateral filaments 45–65 µm in diameter near their base with cells L/D 3–4 throughout, tapering gently to a rounded terminal cell; stichidia often with terminal monosiphonous, simple or branched, prolongations; cystocarps with a corticated pericarp and subspherical carposporangia in chains

D. atactica

18. Pseudolateral filaments 20–30 (–40) µm in diameter near their base with cells L/D (3–) 4–10 (–14), gently tapering to slender, lax ends; stichidia without terminal, monosiphonous prolongations; cystocarps with a pericarp of lengthwise-elongate pericentral cells and only slight (or no) cortication and clavate to lacrimiform, terminal carposporangia

D. crescens

19. Branches ecorticate apart from cortical filaments lying between the pericentral cells near the thallus base; pseudolateral filaments with lower cells 20–40 µm in diameter; carposporangia terminal, clavate; stichidia with 6 pericentral cells and sporangia per segment

D. tenuis

19. Branches with moderate cortication, becoming complete on mid parts; pseudolateral filaments 15–40 or 50–80 µm in diameter in lower cells; carposporophyte with small, subspherical to ovoid carposporangia in chains; pericarp corticated by small, irregular cells; stichidia with 4 pericentral cells and sporangia per segment

20

20. Pseudolateral lower cells (15–) 25–35 (–40) µm in diameter

D. capillaris

20. Pseudolateral lower cells 35–90 (–110) µm in diameter

D. hookeri


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