Electronic Flora of South Australia Genus Fact Sheet

Genus SPHACELARIA Lyngbye in Hornemann 1818, pl. 1600

Phylum Phaeophyta – Order Sphacelariales – Family Sphacelariaceae

Thallus 1 mm to 2 (–4) cm long, forming dense tufts or mats, epilithic or epiphytic (usually just penetrating the host), attached by basal discs or by rhizoids. Erect filaments sparsely to much branched, hypacroblastic and hemiblastic, irregularly radial or distichous and opposite. Main axes with a large apical cell, laterals often determinate and with a small, conical, apical cell, not or only slightly increasing in diameter below, ecorticate apart from descending rhizoids especially near the base. Growth apical, with the subapical cell usually dividing transversely, then longitudinal septation of either radial or periclinal types, and in some species with secondary transverse walls; phaeophycean hairs present or absent. Cells with few to many small discoid phaeoplasts and small physodes.

Reproduction: Reproduction by plurilocular gametangia, neutral plurilocular sporangia and unilocular meiosporangia; propagula present in subgenus Propagulifera.

Type species: S. reticulata Lyngbye (Prud'homme van Reine 1982, p. 49).

Taxonomic notes: Sphacelaria is a distinctive genus of some 40 species world-wide. The species are relatively easily recognised, especially those with propagula [which are present mainly in summer whereas sexual reproduction is usually found in winter, as shown by Colijn & van den Hoek (1971) for S. furcigera S. rigidula)]. The detailed life history of this species has been studied by van den Hoek & Flinterman (1968) and probably exemplifies the life history of other species where both plurilocular and unilocular reproductive organs occur.

References:

HORNEMANN, J.W. (1818). (Ed.). Flora Danica 9, 1–11, Plates 1561–1620.

PRUD'HOMME VAN REINE, W.F. (1982). A taxonomic revision of the European Sphacelariaceae (Sphacelariales, Phaeophyceae). Leiden Botanical Series, Vol. 6. (Brill: Leiden.)

VAN DEN HOEK, C. & FLINTERMAN, A. (1968). The life history of Sphacelaria furcigera Kuetz. (Phaeophyceae). Blumea 16, 193–242.

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

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (14 December, 1987)
The Marine Benthic Flora of Southern Australia
Part II
©Board of the Botanic Gardens and State Herbarium, Government of South Australia

KEY TO SPECIES OF SPHACELARIA

1. Secondary transverse walls present and usually abundant in segments; usually epiphytic on Fucales

2

1. Secondary transverse walls absent (or rare) in segments; on rock or epiphytic on Fucales, other algae or seagrasses

5

2. Branching with distichous and opposite laterals; pericysts absent

S. spuria

2. Branching irregularly radial or subdichotomous; pericysts present

3

3. Axes 15–25 in diameter; secondary transverse divisions occasional to frequent

S. multiplex

3. Axes 35–55 µm in diameter; secondary transverse divisions usually abundant

4

4. Branching subdichotomous to alternate, producing plurilocular sporangia on profuse, subdistichous, 3–6 celled laterals at right angles to the main branches

S. implicata

4. Branching irregularly radial with main axes bearing shorter laterals; unilocular sporangia in adaxial rows of 2–5 on short laterals; plurilocular sporangia on occasional, irregularly placed, laterals

S. reinkei

5. Thallus 1–4 (–7) mm high, epiphytic on Fucales; filaments less than 25 in diameter; propagula not present

6

5. Thallus commonly 4–12 mm high, on rock or epiphytic; axes or lower filaments over 25 µm in diameter; propagula usually present (at least in summer)

8

6. Epiphytic on Carpoglossum confluens in discrete tufts with a compact mass of filaments penetrating into the host cortex

S. carpoglossi

6. Epiphytic on Cystophora spp., with basal filaments discrete and penetrating the host meristoderm but scarcely further

7

7. Filaments with segments L/B mostly 1–1.5; only plurilocular sporangia known

S. bracteata

7. Filaments with segments L/B mostly 2–3; plurilocular and unilocular sporangia known

S. chorizocarpa

8. Propagula tribuliform or ellipsoid, with short arms

9

8. Propagula with long, slender, cylindrical or basally constricted arms

12

9. Older filaments (40–) 50–70 (–85) µm in diameter, segments L/B 0.6–1 with (2–) 3–5 (–6) longitudinal walls in side view

10

9. Older filaments 30–45 (–50) in diameter, segments L/B 1–1.5 (–2) with 1–2 (–3) longitudinal walls in side view

11

10. Branching frequent; propagula sub-tribuliform with the end walls of the arms cut off by either straight or angled walls

S. novae-hollandiae

10. Branching sparse; propagula transversely ellipsoid to spindle-shaped, with large terminal cells to the blunt arms cut off by a straight cross wall

S. brachygonia

11. Thallus epilithic or on sea grasses; branching sparse; propagula sub-triangular with tapering arms, terminal cells cut off by a straight cross wall

S. tribuloides

11. Thallus epiphytic on Myriodesma harveyanum; propagula sub-triangular, with terminal cells of arms each cut off by an angled cross wall

S. novae-caledoniae

12. Axes bearing more or less determinate laterals, usually at fairly broad angles; propagula with basally constricted arms and the apical cell normally developing into a terminal hair between the arms

13

12. Axes bearing indeterminate (or largely so) laterals, usually of similar form to the axes and at fairly narrow angles; propagula with cylindrical arms, not basally constricted, and with the apical cell not developing into a hair

14

13. Propagula with 2 arms; axes bearing irregularly placed and developed laterals, usually not evenly tapering

S. biradiata

13. Propagula usually with 3 arms; axes well developed, bearing numerous, usually radially arranged, determinate and evenly tapering laterals

S. cirrosa

14. Lower erect filaments (25–) 30–45 (–52) µm in diameter, of similar diameter throughout, segments showing 1–3 (–5) longitudinal walls, lateral branches usually at narrow angles and of similar height; propagula mostly with two arms

S. rigidula

14. Lower axes (45–) 60–80 (–90) µm in diameter and showing 3–5 longitudinal walls, with slenderer laterals which are largely indeterminate and reach varying heights; propagula mostly with three arms, occasionally two or four

S. fusca


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