Electronic Flora of South Australia Genus Fact Sheet

Genus ENTEROMORPHA Link 1820: 5, nom. cons.

Phylum Chlorophyta – Order Ulvales – Family Ulvaceae

Thallus of simple to much branched, tubular (sometimes compressed) fronds, arising from a holdfast formed of internal rhizoidal extensions from cells near the base, occasionally loose-lying; zooids germinating first to a uniseriate filament which soon becomes tubular with a wall one cell thick, surrounding a narrow to broad cavity. Cells usually over 10 µ across or long, arranged in rows or un-ordered; chloroplast laminate or parietal, sometimes lobed, occupying part or most of the outer part of the cell, with one to several pyrenoids.

Reproduction: Reproduction: generations isomorphic, or with sporophyte or gametophyte only, by biflagellate anisogametes (sometimes apogamous) and quadriflagellate (or biflagellate) zoospores.

Lectotype species: E. intestinalis (Linnaeus) Link.

Taxonomic notes: A genus of numerous species, many of which are widely distributed in temperate and tropical oceans and often variable in form. The southern Australian species described below are based largely on the work of Bliding (1963) and on specimens (in ADU) of Bliding from the west coast of Sweden of several of the common species. Bliding clarified the European species, relegating many old names to synonymy, and he also described a number of new species, as has Dangeard (1958). These new species are usually based in part on cross-fertilisation experiments and morphological differences do not always clearly separate them. Some authors (e.g. Chapman 1956 for New Zealand) have described large numbers of species of Enteromorpha, with numerous sub-specific categories, but it is often impossible to satisfactorily relate such taxa to Bliding's concepts. Accordingly the account below refers the southern Australian taxa to the older, widely distributed, species as recognised by Bliding and should be regarded as provisional only. Detailed studies on their life-history, reproduction and interfertility, similar to those of Bliding, and also ecological studies, are needed to clarify their relationships. Notes are appended on a few species previously recorded from southern Australia but which probably do not occur here.

Enteromorpha as a genus is easily recognised by its tubular fronds and moderately large cells, and is most closely related to Blidingia (see under the latter for comparisons). Study of well preserved or (preferably) living material for morphological features is highly desirable, and features of taxonomic importance are:-the form of the thallus; whether the cells lie in distinct rows (of many cells) or whether they become un-ordered as seen in surface view; the size of the mature cells (not just after division) and their shape; the form of the chloroplast; and the number and relative size of the pyrenoids, usually as seen in surface view of the cells.

The distinctiveness of cell rows is often variable and needs careful assessment since most species can have short rows where active division has occurred. In some cases this is in lower parts of the thallus, in others (e.g. E. compressa) it may be in upper, broader parts. Further, species with normally a single pyrenoid per cell will have two just prior to cell division, and if material was collected at an active division stage, the proportion of cells with two pyrenoids will be greater; also, in cells elongate transversely to the thallus, pyrenoids in the inner part of the cell may be hidden from surface view.

Branching in some species is very variable and must be used with caution. It has not proved possible to separate the southern Australian species on branching features as has Kapraun (1970, p. 211) for species on the coast of Texas.

NOTES ON OTHER SPECIES (recorded in Womersley 1956, pp. 351–353).

E. acanthophora Kützing. As noted previously Australian specimens referred to this species are now placed under E. clathrata.

E. ahlneriana Bliding. This species was recorded since Bliding considered it "probably represented amongst specimens from American River inlet, Kangaroo Island." It is closely related to E. prolifera, differing in reproducing only by asexual zoospores. E. ahlneriana awaits confirmation as a southern Australian species.

E. bulbosa (Suhr) Montagne. The southern Australian specimens are now referred to E. clathrata.

References:

BLIDING, C. (1963). A critical survey of European taxa in Ulvales. Part I. Capsosiphon, Percursaria, Blidingia, Enteromorpha. Opera Bot. 8(3), 1–160.

CHAPMAN, V.J. (1956). The marine algae of New Zealand. Part I. Myxophyceae and Chlorophyceae. J. Linn. Soc. Bot. 55 (360), 333–501, Plates 24–50.

DANGEARD, P. (1958). Observations sur quelques Ulvacées du Maroc. Le Botaniste 42, 5–63.

KAPRAUN, D.F. (1970). Field and cultural studies of Ulva and Enteromorpha in the vicinity of Port Aransas, Texas. Contrib. Mar. Sci. 15, 205–285.

LINK, H.F. (1820). Epistola de Algis aquaticis in genera disponendis. In C. G. D. Nees von Esenbeck, Horae physicae berolinenses, pp. 1–8, Plate 1. (Bonn.)

WOMERSLEY, H.B.S. (1956). A critical survey of the marine algae of southern Australia. I. Chlorophyta. Aust. J. mar. freshw. Res. 7, 343–383.

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 SPECIES OF ENTEROMORPHA

1. Thallus loose-lying, normally unbranched and without proliferations, of similiar diameter throughout; central cavity narrow; cells in distinct longitudinal rows, with 2–5 pyrenoids per cell 1

E. ralfsii

1. Thallus usually attached, sometimes becoming loose-lying, simple or usually branched or with proliferations, expanding from below upwards (or tapering near apices); central cavity usually broad, sometimes narrow or thallus compressed with only the margins saccate; cells in rows or un-ordered, with 1 to several pyrenoids per cell

2

2. Thallus very slender and much branched, with frequent uniseriate branchlets; cells in longitudinal rows and often transversely associated, becoming 25–30 µm long below and each with numerous (4–14) small pyrenoids 2

E. paradoxa

2. Thallus moderately slender to robust, simple or branched, without (or with few) uniseriate branches; cells in rows or un-ordered, usually under 25 µm long below, each with one to a few pyrenoids

3

3. Thallus simple, with a tubular stipe but soon becoming strongly compressed with the two layers adherent and separated by mucilage, only the margins remaining saccate; cells angular, in longitudinal and often transverse rows; one prominent pyrenoid per cell

E. linza

3. Thallus simple (cells un-ordered) or usually branched, terete or compressed (but not with layers adherent); cells in rows or un-ordered, each with one to a few pyrenoids

4

4. Thallus usually branched, often proliferous; cells small to mid-sized (mostly 10–16 µm long), usually square to rectangular in surface view and in distinct longitudinal rows (less so in transverse rows); chloroplast parietal, with one large pyrenoid (20–60% of the cell width)

E. prolifera

4. Thallus simple or branched; cells mid-sized to large (often over 14 µm long in lower parts), angular to rounded, in rows (then with 2–5 pyrenoids) or largely un-ordered (with a single pyrenoid); chloroplast parietal or lateral, with one to several small to medium sized pyrenoids (10–30% of the cell width)

5

5. Thallus usually branched; cells mid-sized to large, usually arranged in distinct longitudinal and often in transverse rows throughout the thallus; chloroplast parietal or lateral, usually with 2–5 pyrenoids

6

5. Thallus simple or branched (usually near the base); cells mid-sized, un-ordered throughout or with some rows in the upper thallus; chloroplast parietal, with a single pyrenoid

7

6. Thallus branched, often proliferous; cells in distinct longitudinal and transverse rows throughout the thallus, usually square to rectangular; chloroplast parietal, often marginally denticulate, usually with 2–3 pyrenoids

E. flexuosa

6. Thallus usually much branched; cells large, in longitudinal rows and often in transverse rows in younger parts, angular to rounded; chloroplast often lateral and lobed or dentate, leaving much of each cell clear, with (2–) 3–5 pyrenoids

E. clathrata

7. Thallus branched from close to the base or above, either remaining terete or becoming compressed, then often with ruffled margins; cells un-ordered in lower thallus and stipe, often in rows (in patches) in upper thallus 7

E. compressa

7. Thallus unbranched, cells un-ordered throughout

E. intestinalis


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