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Key to Cyanophyta

Key to Cyanophyta


by C.S. Lobban & A.D.R. N'Yeurt

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by C.S. Lobban & A.D.R. N'Yeurt

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Complete genera list.

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Disclaimer          Chlorophyta key          Heterokont key         Rhodophyta key

1. Unicellular symbionts inside tunicates; chlorophylls a+b, no water-soluble pigments: Prochloron
1. Unicellular, colonial or multicellular, free-living; chlorophyll a plus water-soluble phycobilins: 2

2. Unicellular or forming non-linear clusters (colonies), cells separated by mucilage: 3 [coccoid comparison charts]
2. Cells with common crosswalls united into trichomes (filaments):

Unicellular genera

3. Colonies spherical, square, or irregularly shaped: 4
3. Colonies with
polarized growth (distinct origin or basal end versus apical end, or extending as pseudofilaments): 9

4. Cells elongate, isopolar (oval) or heteropolar: 5
4. Cells spherical or hemispherical: 6

5. Cells isopolar, irregularly arranged in colony: Aphanothece
5. Cells heteropolar, radially arranged in colony: Gomphosphaeria

6. Daughter cells within concentric layers of mucilage: 7
6. All cells in common mucilage: 8

7. Multiple fission giving isolated packets of cells within layered sheath: Chroococcus
7. Binary fission giving irregular colonies of cells surrounded by concentrically layered mucilage sheath: Gloeocapsa

8. Cells irregularly arranged in mucilaginous colonies: Microcystis
8. Cells arranged in perpendicular rows in flat ± square colonies: Merismopedia

9 (3). Cells in adjacent serial rows: Entophysalis
9. Cells in single row (pseudofilamentous): 10

10 (9). Prostrate colonies forming short ± branched chains, reproduction by nanocytes (endospores): Pleurocapsa
10. Erect unbranched pseudofilaments, no nanocytes: Johannesbaptistia

Filamentous genera

11. Heterocytes (heterocysts), akinetes or true branching all absent (false branching may be present): 12 (Oscillatoriales)
Heterocytes, akinetes, or true branching present: 26

Without heterocytes

12. Trichomes spirally twisted, lacking a sheath, often motile: 13
12. Trichomes straight, with or without sheath, motile or nonmotile: 14

13. Trichomes with visible cross walls: Arthrospira
13. Trichomes with invisible cross walls, appearing to be single long, spiral cells: Spirulina

14. Cells distinctly wider than long; fragmentation via necridia; motile or not; [cells beginning new division before reaching size of parent (appears as multiple ingrowths of cross wall in growing regions near apex)]: 15
14. Cells approx. isodiametric (nearly square in profile) or longer than wide; trichomes motile; with or without necridia [dead cells]; [divided cells grow to size of parent before dividing again]: 19

cells wider than long

[The characters used to define genera in this section are disputed and hard to determine.]

15. Filaments made of multiple trichomes in common, often thick sheath that is conically closed at the apex; growth diffuse; trichomes nonmotile: Schizothrix
15. Single trichome in sheath, or if several then apex of sheath open; growth in meristematic zones (usually near apex); trichomes often motile: 16 (Oscillatoriaceae)

16. Sheath absent: 17
16. Sheath present: 18

17. Free-living trichomes, often exhibiting movement: Oscillatoria
17. Short, non-motile trichomes, symbiont in sponges: Hormoscilla

18. One trichome per sheath: Lyngbya
18. Several trichomes per sheath, sheath is open at the end: Blennothrix

cells longer than wide

19. Without sheaths, or with a fine, thin sheath; trichomes breaking into fragments without necridia: 20 (Pseudanabaenaceae)
19. Firm sheaths usually present [Microcoleus sheath fine and diffluent; Phormidium can lack sheath]; trichomes breaking into fragments via necridia: 21 (Phormidiaceae)

20. Filaments epiphytic, 1-11 µm wide, attached to the substratum along their length, but having both ends free: Leibleinia
20. Very narrow trichomes (0.5-3 µm wide), sometimes with fine but distinct sheath:

20A. Filaments with constrictions at crosswalls; our species ~ 2 µm wide, wrapped around other algal filaments: Pseudanabaena
20A. Filaments without constrictions at crosswalls; forming mats: Leptolyngbya

21. Sheath (if present) containing only one trichome: 22
21. Sheath present with more than one trichome: 24

22. Sheath lamellated, often colored: Porphyrosiphon
22. Sheath not lamellated: 23

23. Thallus organized as erect bundles of trichomes:
23. Trichomes separate (not bundled); facultative sheaths: Phormidium

24. Sheath lamellated: Hydrocoleum
24. Sheath not lamellated: 25

25. Sheath fine and diffluent (with an indistinct margin): Microcoleus
25. Sheath firm and limited: Sirocoleum

With heterocytes

26 (11). Trichomes unbranched, heterocytes intercalary: Hormothamnium
26. Trichomes with true or false branching; or if apparently unbranched, the heterocytes basal: 27

27. Trichomes with false branches, or appearing unbranched: 28 (Nostocales)
27. Trichomes with true branching: 33 (Stigonematales)

28. False branching arising from a heterocyte (thus always a heterocyte at the base of a branch): 29
28. False branching arising from necridic cell, usually a pair of branches, without a heterocyte at the junction; trichomes often also forming loops: 32 (Scytonemataceae)

29. Branching common, intercalary heterocytes also common, filaments isopolar: Tolypothrix
29. Branching uncommon or not apparent; filaments heteropolar, the base with a heterocyte, the apex tapering to a long hyaline hair: 30 (Rivulariaceae)

30. Solitary trichomes or groups, one trichome in a sheath: Calothrix
30. Filaments organized into colonies: 31

31. Branches within same sheath; colonies hemispherical, a common mucilage surrounding the sheathed trichomes: Rivularia
31. Branches in separate sheath; colonies fasciculate (branches not in a common mucilage):

32. Filaments endolithic: Kyrtuthrix
32. Filaments free:
Scytonema (link is to freshwater specimen)

33. Heterocytes terminal or lateral, thallus boring into rock and shells: Mastigocoleus
33. Heterocytes intercalary, thallus free: 34

34. Main axes, often multiseriate, distinct from branches; branches arising at right angles to main axes (“T” branching): Fischerella
34. Main axes indistinguishable from branches, all uniseriate; “Y” branching:

نویسنده : رضا رمضان نژاد قادی ; ساعت ٤:۱۱ ‎ب.ظ روز سه‌شنبه ٢٧ امرداد ۱۳۸۸