Mucilage sheaths of spores of red algae

Abstract

Spores of fourteen species of red algae were examined in sea water/Indian ink suspensions and the volumes of the spores and their mucilage sheaths measured. The mucilage sheaths occupied 52-8-87-7% of the combined spore + mucilage volumes, depending on the species. Spores of different size of the same species had mucilage sheaths occupying similar proportions of the combined volumes, but spores of similar sizes from different species had mucilage volumes typical of all spores of the same species. Experiments with water jets show that the mucilage sheaths are tenacious, and may play some part in the planktonic phase of the spore's existence. I N T R O D U C T I O NIf newly released spores of red algae are placed in a suspension of Indian ink in sea water, a clear halo of mucilaginous material will be seen. A similar mucilage cover is also a well-known feature with certain phytoplankton organisms, in which cells of spiny appearance (e.g. freshwater desmids) assume a spherical form in Indian ink when the mucilage cover is also observed (Lund, 1959). The attachment of red algal spores is a process in which mucilage clearly plays some part (Suto. There appears to be little information on the sizes of the spore mucilage sheaths, and on their likely significance in the planktonic phase of the spore's existence immediately after release. The present work gives the results of an investigation of the spore mucilage of fourteen species of red algae. MATERIALS AND METHODSThe fourteen species of red algae used in the present work are listed in Table 1, together with the localities in the Plymouth neighbourhood where they were collected in July and August 1972. All material was used directly after return to the laboratory, and spores were obtained by overnight settlements from fruiting plants placed in filtered sea water in Pyrex glass dishes at room temperature. Spore samples were picked out with a pipette using a dissecting microscope and placed in the sea water/Indian ink suspension. Spore measurements were made with preparations in which cover glasses were supported on 'layers' of cover-glass fragments, so as to prevent any spore or mucilage layer distortion. These measurements were checked against those made on spore samples immersed in Indian ink suspension and lacking cover-glasses to ensure that no distortion had taken place. Samples of 100 spores were measured in all cases. 512 A. D. BONEY Species Callithamnion tetricum (Dillw.) S. F. Gray. Ceramiutn ciliatum (Ellis) Ducluz. Ceramium rubrum (Huds.) J. Ag. Ceramium shuttleworthianum (Kiitz.) Silva Chondrus crispus Stackh. Chylodadia venicillata (Lightf.) Bliding Cryptopleura ramosa (Huds.) Kylin ex Newton Lomentaria articulata (Huds.) Lyngb. Nitophyllum punctatum (Stackh.) Grev. Polysiphonia lanosa (L). Tandy Polysiphonia urceolata (Lightf. ex Dillw.) Grev. Polysiphonia brodiaei (Dillw.) Spreng. Rhodymenia pseudopalmata (Lamour.) Silva Stenogramme interrupta (C.Ag.) Mont.

The settlement, attachment and establishment of marine algal spores

“…In many cases the release of the spores involves an active discharge mechanism, usually as a result of increased turgor pressure of the mucilage surrounding the spore within each sporangium (e.g. egg release in Tilopteris, Kuhlenkamp & Miiller, 1985; spore release in Laminariales, Toth, 1976b;Maier & Miiller, 1982; spore release in various red algae, Boney, 1975Boney, , 1981. In some algae, however, the reproductive spores are distributed whilst still attached to the parental plant body.…”

“…Certainly it is a common and very tenacious component of red algal spores (Boney, 1975(Boney, , 1981Ngan & Price, 1979) and can be clearly seen under the light microscope using indian ink preparations. The trailing character of this mucilage during spore movement and its adhesive sticky nature enhances entrapment and provides an early attachment mechanism.…”

Dispersal by macroalgae

“…Little is known of the density of algal propagules and the measurements of Coon, Neushul & Charters (1972) and Okuda & Neushul (1981), are probably significant overestimates, for they made no allowance for the large mucilage envelopes that surround most red algal spores. These envelopes may constitute 80% of the spore's volume (Boney, 1975;Ngan & Price, 1979). It is unlikely that the mucilage usually slows the sinking rate of such spores, as is often claimed (e.g.…”

“…Santileces, 1990), since the increase in diameter is so great that sinking velocity will almost certainly be increased. Boney (1975), for example, observed that newly-released spores sank up to twice as fast as those held overnight during which time the diameter of the mucilage sheath had significantly diminished.…”

Propagules of marine macroalgae: Structure and development

“…In many species of algae the mucilage disperses rapidly, but in others the spores, and sometimes the eggs or zygotes, possess a more or less persistant mucilage layer or sheath. Boney (1975) observed that the mucilage sheath could be voluminous and constitute up to 92% of the spore volume in some red algae, and he argued that the presence of Fl6s 7-12. Macroalgal propagule structure.…”