Phaeophyta

1. PHAEO PHYTA ( Brown Algae ) DICHOTOMOUS KEY OF Prepared by: NOE P. MENDEZ CENTRAL MINDANAO UNIVERSITY (CMU) [email protected]

2. DICHOTOMOUS KEY

3. Dos and Don’ts

4. The Phaeophyta are almost entirely marine, frequently dominating rocky shores in cold and temperate waters throughout the world. The colors of brown algae (predominantly due to the brown accessory pigment fucoxanthin ) cover a spectrum from pale beige to yellow-brown to almost black. In tropical seas, they range in size from microscopic filaments to several meters in length.

5. Kingdom: Protista

6. Key to Genera of the Phaeophyta 1. Tinted algae, less than 1 mm wide, whose shape can only be discerned using a microscope. They often cover surfaces. 2 *1. Algae larger than the above, distinguished by the shape of their thallus without magnifying equipment. 3 2. The thallus is made of a single row of cells. The spore-ridden sporangium are found at the edge of the thallus . Ectocarpus *2. With the aid of a microscope, one may see several rows of cells along the width of the thallus . The triangular or star-shaped sporangium has three or four horns. Sphacelaria 3. Hollow, globular algae, mostly irregular. 4 *3. Flattened or branched algae. Algae otherwise. 5 4. Numerous holes (spaces) in the algal thallus resemble a net or fishing net. The holes are irregular in size . Hydroclathrus *4. The algal thallus is continuous (no holes) and often covered with a smooth mucous layer. The algae’s interior contains gasses. Colpomenia 5. Algae are rigid, resembling higher plants. Relatively large algae, reaching up to 20 cm and more. 6 *5. Algae otherwise. 7 6. The thallus resembles a ‘stalk’ and ‘leaves’. The reproductive organs are located on separate branches. Round flotation blades are held by prickles along the ‘stem’. Sargassum *6. The ‘stem‘ is mostly flat, often winged, sometimes cylindrical. Elongated floatation cysts that form a part of the stalk are sometimes missing. Cystoseira 7(5). Flattened algae, that if hollow, are much longer than they are wide. 8 *7. Algae incorporating a central axis with numerous side branches. The arms generally resemble a feather. Each side branch is smaller than 1 mm. Stypocaulon 8 . Cylindrical, hollow and unbranched algae, 1-5 mm wide and up to 20 mm length . They grow in the upper regions of the intertidal zone and are sometimes exposed to air. Scytosiphon *8. Algae that aren’t hollow. Algae otherwise. 9 9. The algae body resembles a central axis with membranous wings on either side . Dictyopteris *9. Membranously wingless algae. Algae otherwise. 10 Flat algae with regular, dichotomous branching. Growth is generated from a single apical cell or two (microscope required). 11 *10. Fan-like algae, strand-like algae, algae otherwise. 12 11. The upper part of the thallus is rounded and often widens (spatula-like ). Through a microscope, three layers of cells can be discerned . Dilophus

7. Ectocarpus Sphacelaria

8. Colpomenia Hydroclathrus

9. Sargassum Cystoseira

10. Stypocaulon Scytosiphon

11. Dictyopteris Dilophus

12. *11. The edges of the branches do not widen or round off. A two-layered medulla of cells can be discerned through a microscope. Dictyota 12. Fan-like algae where, sometimes, especially in mature individuals, the fan splits into several lobes. 13 *12. Algae otherwise. 15 13. Concentric lines appear along the thallus ’ breadth. 14 *13. The thallus resembles flattened lobes, loosely attached to rocks. The algae is coloured shades of brown–yellow and characteristically grows in shady areas of the subtidal zone. Lobophora 14. Extremely common algae. The thallus contains calcium, and its edges curl backwards. Padina *14. The alga does not calcify. Plants immersed in water have a phosphorous shade of azure. Growth generates from a row of apical cells (a microscope is required. Stypopodium 15(2). Soft, strand-like algae, unbranched and narrow at the bottom. Plants are commonly found in the upper region of the intertidal zone . Petalonia *15. The thallus splits into irregular, lineal strands. 16 16. Fan-like algae that split into (usually) dichotomous strands. The further they are from the algal base, the narrower the strands become. The algae is bright brown and seems to have dark lines along its breadth . Taonia *16. The algal surface is rough. It is dark-brown, but when exposed to air, the thallus changes colour to dark green. Branching is dichotomous . Spatoglossum

13. Dictyota Lobophora

14. Padina Stypopodium

15. Taonia Spatoglossum

16. Key to the Species of Phaeophyta

17. Key to species of Sargassum

18. 1 Fronds very similar to Dictyota species, but nearly wholly prostrate and with midrib; branching irregularly dichotomous D. repens 1 Fronds not similar to Dictyota (wider, taller, coarser), not prostrate; with numerous apical cells 2 2 With veinlets visible to naked eye, forming acute angles to the midrib; sporangia or gametangia in linear patches parallel to midrib; blade mostly distromatic from margin to midrib D. plagiogramma 2 Veinlets microscopic and faint; sporangia or gametangia in rows starting at midrib and arching downward to lateral margins; blade monostromatic for up to 15 cells from margin, then di- polystromatic to midrib D. australis Key to the species of Dictyopteris

19. Key to the species of Dictyopteris

20. 1 Plants dark chocolate brown, fronds tightly to loosely spiralled (twisted) axes up to 3 mm in diam., terminal dichotomous division about 1 mm in diam D. acutiloba 1 Plants medium brown to yellowish, often iridescent when fresh, blades not twisted 2 2 Fronds rarely more than 4 cm long, less than 2 mm at widest, then narrowing abruptly toward apices; on same plant, some portions may be 2 to 3 mm wider than other places D. ceylanica 2 Fronds free of turf up to 5 cm long, shorter if in turf; characteristically nearly same width throughout, with truncate apices; branch dichotomies short 3 3 Fronds golden with bluish iridescence until removed from water, often in turf on sides of tide pools; in surface view some superficial cells having L-shaped lenticular thickenings D. friabilis 3 Fronds yellowish-green, iridescent, occasionally whole plant with 1-2 twirls, but fronds not twisted; no lenticular thickenings; lateral margins with many proliferations of various lengths and sizes D. sandwicensis Key to the species of Dictyota

21. Key to the species of Dictyota

22. 1 Fronds heavily calcified on ventral "inner" surface, nearly obscuring hair and sporangial lines 2 1 Fronds lightly calcified, mostly as a very thin sheet of gray, hair and sporangial lines clearly observable 3 2 Calcification very chalky and continuous on ventral "inner" surface; bright golden-yellow to orange on dorsal "outer" surface P. melemele 2 Calcification thick but discontinuous, tan on upper part of ventral surface, and throughout dorsal surface P. japonica 3 Blades distromatic throughout 4 Key to species of Padina

23. 3 Blades distromatic except at base, or blades polystromatic 5 4 Fronds split through nearly to base; base thick, with rust-colored rhizoids forming a hump P. australis 4 Plants not split, but blades laterally adhering to each other, frequently to the base and difficult to separate without tearing; almost always in large clumps P. thivyae 5 Blades distromatic in upper parts, tristromatic below; sporangia grouped above every hair line on inner surface, hairs lacking on opposite surface P. tenuis Key to species of Padina

24. 5 Blades three or more layers thick 6 6 Blades 4 cells thick in upper frond, up to 9 cells thick below; sporangia grouped above every hair line on inner surface, hairs lacking on opposite side P. Crassa 6 Blades mostly 3-celled (rarely 2-celled) throughout, sporangia grouped above every hair line on inner surface, but both groups alternating with a hair line on opposite surface P.   boergesenii Key to species of Padina

25. Key to species of Padina

26. 1 Fronds erect from a discrete base, silky colorless hairs common along mid an upper parts of plants; growing high in the intertidal region, usually on vertical or sloping igneous rocks C. minima 1 Fronds decumbent to prostrate, bases spreading; axes terete , without colorless hairs; usually growing on horizontal calcareous surfaces below low tide on reef flats C. implexa Key to the species of Chnoospora

27. 1 Fronds soft, erect but lax; branching dichotomous, axes less than 2 mm in diameter, apices hair-like R. orientalis 1 Fronds forming matted cushions composed of many tightly adhering branches, irregularly dichotomously divided R. intricata Key to the species of Rosenvingea

28. Key to species of Sphacelaria 1 Arms of modified lateral branches ( propagula ) cylindrical, like a broad V S. rigidula 1 Arms of propagula not cylindrical, approximately triangular or club-like in outline 2 2 Propagula club-like, top rounded or thickened S. novaehollandiae 2 Propagula triangular, like a top; plant tufts dense and nearly black S. tribuloides

29. 1 Plants with extensive matted rhizoidal systems endophytic among utricles of Codium species; spindle -shaped plurilocular structures near basal portion of plants F. elachistaeformis 1 Plants with a small number of rhizoids; endo /epiphytic on a wide variety of hosts; plurilocular structures cylindrical, distributed throughout plants below meristematic regions F. indica Key to species of Feldmannia

30. 1 Intertidal, in rope-like strands, cells of filaments isodiametric to twice as long as broad, hook-like or short lateral branches present; plurilocular organs about as long as broad H. breviarticulata 1 Subtidal , not rope-like, cells becoming larger than twice their diameter, without hooklike lateral branches; plurilocular organs cylindrical more than twice as long as broad attached alternately or adaxially H. mitchelliae Key to species of Hincksia

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