Patches of Vaucheria frigida at the margin of the Botanic Gardens pond

State Herbarium staff member Carolyn Ricci and Hon. Research Associate Bob Baldock from the Algae Unit report on algae found in the new Botanic Gardens stormwater recycling ponds: this time on a species of Vaucheria…

Vaucheria frigida mat (AD-A96476)

A dark green, velvety patch about 1.5 m across has appeared on the banks of the northernmost wetland storage pond. It stands out in texture and colour from the extensive band of grass-green mosses now growing there. Under the microscope, snake-like, twisted threads full of disc-shaped chloroplasts reveal it is a remarkable alga — Vaucheria frigida — and not a moss. This is the first time that this species has been recorded for the Southern Lofty (SL) region.

Vaucheria belongs to the yellow-green algae group, the Xanthophyceae. This is not a green alga or common “pond slime”. Its microscopic threads are generally not partitioned into separate cells. With no cross walls, the whole mass we see at the pond could theoretically be a single plant originating from a single spore.

This group of alga stores oil rather than starch and reproduction is even more remarkable. Male and female structures share the same stalk in this species: the female (oogonium) is a thick-walled globe of chloroplasts and oil droplets, the male (antheridium) a twisted or coiled little cylinder developing numerous sperms each with two whiplashes, enabling them to swim, then gain entrance through an opening in a small beak of the female structure. Vaucheria can spread also by releasing swollen blobs of cell contents that have a surface of numerous paired whiplashes, propelling the blob (zoospore) through water.

Twisted threads without cross walls

This algae can inhabit fresh or slightly saline water, or live on moist soil, as has happened in the Botanic Gardens pond population. Five species of Vaucheria associated with marine situations (but not this one) are recorded in the late Prof. Womersley’s Marine benthic flora of south-eastern Australia.

We hope you agree that the blooming of the small and unusual in and around the ponds deserves a closer look—perhaps a student might one day take up the challenge?

Globe-shaped female and twisted male structure (the latter empty of contents)

Herbarium wing, RBG Kew (photo C.J. Brodie)

State Herbarium Weeds Botanist Chris Brodie recently visited the African grass specialist Tom Cope at the Herbarium of the Royal Botanic Gardens, Kew, London, while on holiday in England. Chris had previously sent some lovegrass (Eragrostis) specimens from Adelaide to Kew that could not be reliably identified to species level using the Australian literature. Specimens sent were plants first noticed by Natural Resources (NRM) staff from Adelaide & Mount Lofty Ranges, the South East & Eyre Peninsula regions as well as plants from SA Murray-Darling Basin region.

The unknown plants turned out to be a part of the Eragrostis curvula (Schrad.) Nees complex, also commonly known as African lovegrass, a declared plant under the Natural Resources Management Act 2004.

African grass specialist Tom Cope said that this species is very variable in habit and he was certain that “this can be nothing else other than E. curvula“.

Chris said “the time spent in Kew and knowledge gained there has greatly improved our understanding of the variability that exists within this taxon in South Australia. To identify this grass, we know now to only look for the hard rigid base with many dense long hairs and at flower characters. All other features of the plant, such as stem thickness, branching, height, general habit and colour, can vary so much that superficially different races of this grass can even look like different species when side by side”.

Eragrostis curvula (photo C.J. Brodie)

Tom Cope also confirmed the identity of Eragrostis trichophora Coss. & Durieu, within the species complex he is calling Eragrostis cylindriflora Hochst. These plants were collected just north of Adelaide and to the west of Eyre Peninsula. The first Herbarium record for Eragrostis trichophora in South Australia dates from mid-2012 from the Eyre Peninsula.

Chris is currently working on a fact sheet for identifying Eragrostis curvula and a paper on the weedy Eragrostis taxa and their variability in South Australia. Until then, as usual, please contact Chris regarding weedy plant identification.

State Herbarium botanist Peter Lang reports that two recently described species of bladderwort  (Utricularia) have been added to the Census of South Australian plants, algae & fungi. Bladderworts are carnivorous plants that have leaves modified to form small bladder-like traps.

Utricularia fenshamii is remarkable in being almost entirely confined to mound springs of the Lake Eyre Basin, and in South Australia is only found on such springs just beyond the northern edge of the Flinders Ranges.

Utricularia barkeri was named after Bill Barker, Honorary Associate and former Chief Botanist at the State Herbarium, who had made annotations on herbarium sheets in the mid 1980s to indicate differences from the more common U. dichotoma, with which it often grows.  In South Australia it is found in the South-Eastern and Kangaroo Island regions.

The photos show flowers of Utricularia fenshamii (top image) compared to the more common U. dichotoma (bottom), in which it was previously included.

Utricularia fenshamii (Photo by SA Seed Conservation Centre)

Utricularia dichotoma (Photo by P.J. Lang)