Electronic Flora of South Australia Genus Fact Sheet

Genus CAULERPA Lamouroux 1809: 332

Phylum Chlorophyta – Order Caulerpales – Family Caulerpaceae

Thallus with a horizontal stolon attached by rhizoidal outgrowths and bearing erect photosynthetic fronds which are branched in various ways; coenocytic throughout but generally with firm walls and slender cylindrical wall ingrowths (trabeculae) crossing the lumen; chloroplasts with or without pyrenoids; amyloplasts present.

Reproduction: Reproduction (known in a few species only) by clumping of the cytoplasm and chloroplasts, and differentiation of anisogametes which are discharged through papillae on the surface of the ramuli (Price 1972); meiosis occuring at gametogenesis.

Lectotype species: C. prolifera (Forskal) Lamouroux.

Taxonomic notes: A large and common genus of about 70 species, frequent in tropical-subtropical seas but particularly rich and distinctive on southern Australian coasts. Weber van Bosse (1898) monographed the genus and recognised 12 subgenera. These were supported by Calvert, Dawes & Borowitzka (1976) on the basis of chloroplast ultrastructure, and these authors suggested southern Australia may be the geographical origin of Caulerpa.

The branching of the erect fronds distinguishes the species. In all southern Australian species they are branched to two or three orders, but in a few species the erect frond is essentially unbranched (e.g. C. filiformis on N.S.W. coasts).

The axes of the erect fronds comprise the first-order branches; they are occasionally branched in some species (e.g. C. simpliciuscula) but are of similar diameter throughout. They may bear only ramuli as second-order branches or may have distinct and regular second-order laterals which bear the ramuli as third-order branches. The ramuli may be vesiculate or terete to flattened, and the terete type may be unbranched, furcate or with a few subdichotomous or lateral branches which, when branched, are of similar diameter throughout.

References:

CALVERT, H.E., DAWES, C.J. & BOROWITZKA, M.A. (1976). Phylogenetic relationships of Caulerpa (Chlorophyta) based on comparative chloroplast ultrastructure. J. Phycol. 12, 149–162.

LAMOUROUX, J.V.F. (1809). Mémoire sur trois nouveaux genres de la famille des Algues marines. J. de Bot. 2, 129–135.

PRICE, I.R. (1972). Zygote development in Caulerpa (Chlorophyta, Caulerpales). Phycologia 11, 217–218.

WEBER van BOSSE, A. (1898). Monographie des Caulerpes. Ann. Jardin Bot. Buitenzorg 15, 243–401, Plates 20–34.

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

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (31 May, 1984)
The Marine Benthic Flora of Southern Australia
Part I
©Board of the Botanic Gardens and State Herbarium, Government of South Australia

KEY TO THE SPECIES OF CAULERPA

1. Ramuli compressed or terete (simple or branched), not vesiculate

2

1. Ramuli vesiculate, unbranched

14

2. Erect axes bearing (directly) distichous, simple, terete or compressed ramuli

3

2. Erect axes and/or second-order laterals bearing ramuli usually in more than two rows or on all sides; ramuli terete, usually filiform, simple or branched

7

3. Ramuli terete, linear, (1–) 1.5–2.5 (–3) mm long, and less than 0.5 mm in diameter, alternately arranged

C. alternans

3. Ramuli slightly to distinctly compressed, tapering from base to apex or broadest near their middle, either alternate or irregular, more than 3 mm long and 0.5 mm in diameter, or opposite, 1–3 mm long and 0.2–0.5 mm in diameter

4

4. Ramuli scattered, separated by at least their basal width, (2–) 4–6 (–10) mm long, 0.5–1 (–1.5) mm broad

C. remotifolia

4. Ramuli regular and adjacent, separated by less than or about their basal width

5

5. Axes of erect fronds slightly compressed, 0.5–I mm broad, ramuli opposite and only slightly compressed, 1–2 (–3) mm long

C. distichophylla

5. Axes of erect fronds compressed, 2–8(- 10) mm broad, ramuli alternate, compressed, 3–10 mm long

6

6. Ramuli convex on lower side, straighter on upper side, usually broadest (1.5–4 mm) at base, 3–10 mm long

C. scalpellifortnis

6. Ramuli convex on upper side, straighter on lower side, basally constricted, 4–8 mm long, 0.7–1.5 mm broad

C. ellistoniae

7. Erect axes without second-order laterals but bearing simple or 1–4 times branched ramuli in rows or on all sides

8

7. Erect axes bearing numerous distichously or radially arranged second-order laterals, each of which bears numerous simple or furcate ramuli

12

8. Ramuli unbranched

9

8. Ramuli once or more branched

11

9. Ramuli in distinct longitudinal rows, relatively straight

10

9. Ramuli usually not in distinct longitudinal rows, soft and incurved, 0.5–1.5 cm long

C. longifolia f. crispata

10. Ramuli in 3 rows (2 when juvenile), 3–5 (–9) mm long

C. trifaria

10. Ramuli usually in 5(4–6) rows, 0.5–1.5 cm long

C. longifolia

11. Ramuli once, or more usually twice, furcate near their base, rigid, straight to slightly curved, 1.5–4 mm long; stolon bearing simple ramuli 0.5–2.5 mm long

C. brownii

11. Ramuli 1–5 times laterally branched in their lower half, 1–3 cm long; stolon naked

C. cliftonii

12. Second-order laterals irregularly radially arranged around erect axes, 1–3 (–4) cm long, bearing usually simple ramuli 2–7 (–10) mm long, subdistichously to irregularly arranged; stolon covered with spinous ramuli

C. obscura

12. Second-order laterals distichously arranged on erect axes; ramuli one to several times furcate, less than 3 mm long; stolon covered with minute, branched ramuli

13

13. Ramuli once furcate usually near their base, 1–3 mm long, with a single or twinned spinous apex

C. flexilis

13. Ramuli minute (0.2–0.5 mm long), much-branched and spinous, covering the thallus

C. hedleyi

14. Ramuli distichously arranged on axes

15

14. Ramuli on all sides of axes

17

15. Ramuli ovoid to elongate-ovoid, 3–7 mm long, usually L/B less than 2

C. geminata

15. Ramuli elongate, clavate, usually over 6 mm long, L/B usually greater than 2

16

16. Ramuli (5–) 6–9 mm long, 1.5–2.5 mm broad

C. annulata

16. Ramuli 1–3 cm long, 3–8(40) mm broad

C. cactoides

17. Ramuli elongate clavate, (1.5–) 2–5 (–7) mm long, (0.5–) 1–1.5 (–2) mm broad near apex

C. racemosa var. laetevirens f. cylindracea

17. Ramuli sub-spherical to ovoid, elongate-ovoid or pyriform, usually less than 4 mm long, in some species constricted below the spherical-ovoid terminal part

18

18. Ramuli with a slight to prominent swollen base protruding from the axes, then constricted with a sub-spherical or ovoid terminal part

19

18. Ramuli with the constriction adjacent to the axis, ovoid to clavate or ovoid-pyriform

20

19. Ramuli with a prominent papillate base, subspherical above the constriction and 150–550 (–600) µm in diameter, with more than 14 around the axes

C. papillosa

19. Ramuli with a slight, convex papilla from the axis, ovoid above the constriction and 1–2 mm long, 0.5–1.5 mm in diameter, fewer than 10 around the axes

C. vesiculifera

20. Ramuli densely arranged on the axes, touching, (6–) 8–14 around the axes, 0.7–1.5 mm long and 300–700(450) µm in diameter

C. simpliciuscula [less dense, 6–10 around the axes, in var. laxa].

20. Ramuli usually loosely and irregularly arranged, 2–6 around the axes (subdistichous to radial), ovoid, L/B 1.5–2, (1.5–) 2–4 (–7) mm long, 1–3 mm broad

C. geminata


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