Sometimes, working with algae can be frustrating. Collections come in to the State Herbarium of South Australia from various sources – SA Water, Natural Resource Management groups and Marine Biosecurity, for example. Collecting algae for identification can be a bit of a lottery, however. If essential reproductive stages are missing, and these often can’t be seen by the unaided eye, algal workers at the Herbarium can only provisionally suggest names which is disappointing for both collectors and those attempting the identification. But then, if we are lucky, we can also get samples that are bountifully fruitful, literally smothered in remarkable, although often microscopic, reproductive organs.
One such case came from 5 m deep at Cable Hut Bay, near Cape Spencer, southern Yorke Peninsula, collected by James Brook. The alga was dotted with products of sexual reproduction (cystocarps) looking like the fruits of terrestrial plants.
The alga was Heterosiphonia muelleri (Sonder) De Toni in the Dasyaceae, a family named from “dasya” (Greek) meaning “shaggy”, an appropriate description looking in detail at the fluffy branches of this species (see also the Algae Revealed key to common red algae of South Australia, part V, 2.3mb PDF).
More remarkable than the mass of thin threads covering the plant were the bright orange to red-brown cystocarps. These were stalked, semi-transparent “flasks”, with elegant conical necks through which the spores (carpospores), clustered within, are released to germinate into the next stage of the algal life cycle, an asexual spore plant. Under the microscope they looked “good enough to eat”, but, unfortunately, would not have proved a sumptuous meal, even though numerous.
With such beautifully reproductive material, identification was practically ensured. A look through the microscope showed ranks of large cell alternating with small ones along main branches, characteristic of the family Dasyaceae.
All that remained was to section and stain blue one of the main branches (axes). A central large cell with a ring of 10 small ones, wrapped (corticated) with even smaller ones was present and clinched the identification.
It’s always a pleasure to work with such material, and satisfying when we can be sure of an identification, and I hope this gives you insight into some of the tasks involved in working with algae at the Herbarium.
Contributed by State Herbarium Hon. Associate Bob Baldock.