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Electronic Flora of South Australia Genus Fact Sheet
Phylum Phaeophyta – Order Chordariales – Family Leathesiaceae
Thallus minute [less than 2 (–2.5) mm high], gelatinous, basally partly to slightly endophytic with a pulvinate to tufted medulla and cortex. Medulla of erect, subdichotomous, filaments 3–25 cells long, developed from basal rhizoidal filaments. Determinate cortical filaments mostly free (not forming a dense stratum), arising from upper medullary cells or directly from basal filaments, 10–40 (–80) cells long, cylindrical or with their greater diameter part way along, with phaeophycean hairs. Phaeoplasts several to numerous per cell, each usually with a pyrenoid.
Reproduction: Plurilocular sporangia borne on uppermost medullary cells forming a stratum above the medulla and at the base of the cortical filaments, clustered, mostly uniseriate. Unilocular sporangia borne on uppermost medullary cells, ovoid.
Type species: M. pulvinata (Kützing) Kuntze [=M. rivulariae (Suhr) J. Feldmann].
A genus of about 15 species (Feldmann 1943) in temperate and colder waters.
Taxonomic notes: Myriactula is morphologically similar to Elachista but differs in possessing phaeophycean hairs. It forms better defined tufts than Strepsithalia, with a distinct medulla and numerous determinate cortical filaments, but these are much less developed and less compact than in the globular thalli of Corynophlaea, and the latter genus has a basal layer on the surface of the host only, whereas the base of Myriactula is partly endophytic. The cortical filaments of
Myriactula are essentially separate and free from each other in contrast to Corynophlaea where they form a dense stratum enveloped in mucilage. Some of the following species, as for most species of Myriactula, are not well-defined and further study of species on the southern Australian coast is needed.
References:
FELDMANN, J. (1943). Une nouvelle espèce de Myriactula parasite du Gracilaria armata J. Ag. Bull. Soc. Hist. Nat. Afr. Nord 34, 222–229.
KUNTZE, O. (1898): Revisio generum plantarum vascularium. Vol. 3. (Würtzburg.)
The Marine Benthic Flora of Southern Australia Part II complete list of references.
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 MYRIACTULA
1. Determinate cortical filaments | M. arabica |
1. Determinate cortical filaments | 2 |
2. Determinate cortical filaments | M. haydenii |
2. Determinate cortical filaments over 500 µm and 30 cells long; medulla well developed, over 100 1.1m high in mature plants | 3 |
3. Determinate cortical filaments | 3 M. caespitosa |
3. Determinate cortical filaments | 4 M. filiformis |
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