Electronic Flora of South Australia Genus Fact Sheet

Genus HYPNEA Lamouroux 1813: 131

Phylum Rhodophyta – Class Florideophyceae – Order Gigartinales – Family Hypneaceae

Thallus erect, often from an entangled base, much branched usually with numerous, short, lateral branchlets, branches terete to compressed; attachment by discoid haptera or hamate branch ends. Structure uniaxial, apical cell protruding, axial filament distinct throughout, medulla large-celled usually with numerous secondary pit-connections, cells multinucleate, cortex 1–3 cells broad, outer layer usually continuous and without rosettes.

Reproduction: Sexual thalli dioecious; procarpic and monocarpogonial. Carpogonial branches 3-celled, borne laterally to outwardly on inner cortical cells. Auxiliary cells intercalary, next outwardly to the supporting cells. Gonimoblast initial single, inwardly directed and often developing adjacent nutritive tissue, forming outwardly filaments of elongate cells which form a reticulum and pit-connect to inner cells of the pericarp; smaller or lateral cells of the reticulum form clusters of small cells which produce single, subspherical to ovoid, carposporangia. Cystocarps protuberant, subspherical to conical, sessile, with a pericarp of anticlinal chains of cells, ostiolate or not. Spermatangia cut off, often in short chains, from initials derived from outer cortical cells of short lateral branchlets.

Tetrasporangia formed in swollen nemathecia partly or completely surrounding the base of short lateral branchlets, zonately divided.

Life history triphasic with isomorphic gametophytes and tetrasporophytes.

Lectotype species: H. musciformis (Wulfen) Lamouroux 1813:131.

Taxonomic notes: A genus of numerous species with many uncertain names, much in need of a detailed monographic revision. The lectotype species has been described in detail by Kylin (1930, p. 50, figs 35–39).

This account of southern Australian species of Hypnea is provisional. While most specimens fall into one of the four species below, other species probably occur.

References:

KYLIN, H. (1930). über die entwicklungsgeschichte der Florideen. Lunds Univ. Årsskr. N.F. Avd. 2, 26 (6), 1–104.

LAMOUROUX, J.V.F. (1813). Essai sur les genres de la famille des thalassiophytes non articulées. Ann. Mus. Hist. Nat., Paris 20, 21–47, 115–139, 267–293, Plates 7–13 (1–7).

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

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (14 January, 1994)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIA, Bangiophyceae and Florideophyceae (to Gigartinales)
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIIA 1994, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.

KEY TO SPECIES OF HYPNEA

1. Thallus without numerous, short, spinous branchlets covering the axes or branches; tetrasporangia in swollen areas of lateral branches

H. filiformis

1. Thallus with numerous, short, spinous branchlets covering the axes and branches; tetrasporangia in swollen nemathecia over the base of the branchlets

2

2. Thallus dark red, relatively robust, with numerous hamate branches from both the lower and upper parts of the thallus

H. ramentacea

2. Thallus red-brown to light red, relatively slender, without hamate branches

3

3. Thallus light to medium red to red-brown, without percurrent branches, with all branches bearing numerous short spinous branchlets, more or less at right-angles

3.11. charoides

3. Thallus medium to dark red-brown, main branches percurrent, with relatively few spinous branchlets on main branches and these, as well as lesser branches, directed upwards rather than at right-angles

H. valentiae


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