Chondria: Turf of the Surf

Of the major groups of multicellular algae (or 'seaweeds' in the common parlance) found in the world today, the red algae are unquestionably the most speciose. In this post, I'm looking at a widespread genus of red algae going by the name of Chondria.

Chondria coerulescens, copyright Alan Thurbon.

Chondria is a genus of fifty or more known species of marine algae belong to the Rhodomelaceae, one of the most diverse families of red algae, found in tropical and temperate regions of the world. Species vary in size and are found in a range of habitats from intertidal to subtidal. They may live attached to rock or growing over other seaweeds. Turfs of Chondria may form a significant part of local habitats, but like many smaller red algae they tend not to receive a great deal of attention from humans (I did come across webpages referring to it as a weed in marine aquaria). In the majority of Chondria species, the thallus is erect; more rarely, it grows prostrately against its substrate or free-floating. The thallus is attached to the substrate by a discoid holdfast or by haptera growing from stolons. The greater part of the thallus is filamentous and more or less irregularly branched. The branches may be cylindrical and compressed; the younger branches are often constricted at their bases. The tips of the branches may end in a depression or in a tapering filament. Structure-wise, filaments are solid in cross-section without internal hollows. A central axial cell is surrounded by a ring of five pericentral cells, with the outside of the filament composed of smaller cortical cells.

Like other red algae, Chondria species have a complicated triphasic life cycle. The haploid gametophytes are dioecious: that is, there are separate male and female individuals. Males produce flat, disc-shaped or slightly lobed spermatangia that release male gametes. Female gamete-producing structures grow from the base of lateral filaments on the thallus; fertilised female gametes grow into a diploid, more or less ovoid cystocarp that remains attached to the parent gametophyte. Diploid spores released by the cystocarp grow into independent tetrasporophytes. These produce haploid spores by meiosis that will be released and grow into new gametophytes, and the cycle begins again.

REFERENCE

Womersley, H. B. S. 2003. The Marine Benthic Flora of Southern Australia. Rhodophyta—Part IIID. Ceramiales—Delesseriaceae, Sarcomeniaceae, Rhodomelaceae. Australian Biological Resources Study: Canberra, and State Herbarium of South Australia: Adelaide.