Electronic Flora of South Australia Family Fact Sheet

FAMILY CHORDARIACEAE Greville

Phylum Phaeophyta – Order Chordariales

Thallus (sporophyte) usually 2–50 cm high, erect, cylindrical, usually mucoid, simple to much branched in an irregular manner, with a holdfast of compacted filaments, epilithic or epiphytic. Erect branches composed of a medulla of a single central filament, with surrounding non-pigmented cells, or of numerous longitudinal filaments of elongate cells which may remain as a core or be replaced by irregularly orientated slender (hyphal) filaments. This medulla produces and is surrounded by radiating, simple or branched, determinate filaments 2 to many cells long, forming an assimilatory cortex, in some genera with longer indeterminate cortical filaments also, and in many genera with a subcortex of non-pigmented cells between the medulla and assimilatory cortex. Cells of cortical filaments usually short, with several phaeoplasts per cell and usually with pyrenoids. Phaeophycean hairs present or absent. Growth always subapical, monopodial in uniaxial and some multiaxial genera, or sympodial and trichothallic in other multiaxial genera largely by cell divisions at the base of cortical filaments near the branch apices; intercalary divisions common in developing cortical filaments. Plethysmothalli common; gametophytes microscopic, filamentous or myrionemoid.

Reproduction: Reproduction by meio-zoospores from unilocular sporangia or mitospores from plurilocular sporangia, and by plurilocular gametangia producing isogametes.

A family of about 20 genera world wide, common in the lower intertidal and upper sublittoral, and usually seasonal (in summer) in the occurrence of the macrosporophytes.

Several of the genera are not well-defined and more detailed studies on type species are needed. The degree of development of the subcortex distinguishes several genera. The sub-cortex (Parke 1933, p.8) is here considered to be the zone of radial filaments, of one to several elongate cells, at right angles to the medullary cells and giving rise at their outer ends to the assimilatory cortical filaments which are usually borne in groups. In most genera with loose and relatively long cortical filaments (except Suringariella) these filaments (i.e. with assimilatory cells and beyond the position of unilocular sporangia) are unbranched, and in young parts of Cladosiphon cortical filaments arise directly from the peripheral medullary cells, with later branching from the outer end of the basal cell of such cortical filaments which then comprise the short subcortex. Chordaria has short (2–3 celled) and compact cortical filaments, in marked contrast to the other genera.

Members of the Chordariaceae are most effectively studied in longitudinal view, by softening material (if necessary in dilute acid) and tearing longitudinal strips with fine needles; the relationships of medulla, subcortex and cortex can then be clearly seen. Living or liquid preserved material should always be studied in preference to herbarium sheets.

Life history diplohaplontic and heteromorphic where established (see Wynne & Loiseaux 1976, p.440).

References:

PARKE, M. (1933). A contribution to knowledge of the Mesogloiaceae and associated families. PubL Hartley Bot. Lab. No. 9, 1–43, Plates 1–11.

WYNNE, M.J. & LOISEAUX, S. (1976). Recent advances in life history studies of the Phaeophyta. Phycologia 15, 435–452.

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 GENERA OF CHORDARIACEAE

1. Phaeophycean hairs absent; cortical filaments of two lengths: shorter determinate filaments and longer indeterminate filaments meristematic near their base

2

1. Phaeophycean hairs present; cortical filaments all of similar length and determinate

3

2. Medullary filaments producing abundant, irregularly orientated, hyphae which separate and in old parts obscure the longitudinal filaments; sub-cortex well developed

MYRIOGLOEA

2. Medullary filaments producing relatively few hyphae, with the longitudinal filaments remaining as a compact core throughout the thallus; subcortex slight to absent

PAPENFUSSIELLA

3. Cortical filaments 1–3 (–5) times furcate; medulla largely of irregularly entwined, slender filaments

SURINGARIELLA

3. Cortical filaments mostly simple; medulla of more or less parallel longitudinal filaments or of widely branched and separate filaments irregularly placed, with some longitudinal filaments or hyphae

4

4. Medulla of irregular, widely branched and separated filaments

MESOGLOIOPSIS

4. Medulla of more or less parallel, closely adjacent, longitudinal filaments

5

5. Medulla surrounded by a well-defined subcortex of radiating branched filaments often equal in extent to the diameter of the medulla, and as great or greater than the width of the cortex of determinate filaments

TINOCLADIA

5. Subcortex less in extent than the cortex, often not well defined, sometimes almost absent

6

6. Cortical filaments (1–) 2–3 cells long, clavate or compacted into a pseudo-parenchymatous cortex; unilocular sporangia lying in the surface layer of the cortex

CHORDARIA

6. Cortical filaments 6 or more cells long; unilocular sporangia borne laterally at the base of the cortical filaments, lying well below the surface

7

7. Cortical filaments 12–30 (–45) cells long, usually curved in their upper part, with terminal cells of similar size to subterminal cells; plurilocular sporangia formed as lateral clusters from upper cells of cortical filaments

CLADOSIPHON

7. Cortical filaments 6–10 cells long, straight or only slightly curved, with the terminal cell markedly larger than the subterminal cells; plurilocular sporangia lanceolate, simple or branched, terminal or lateral on several-celled pedicels

POLYCEREA


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