Freshwater algae and a bryophilous fungus: rarely recorded species

Source: Matcham, Howard. “Freshwater algae and a bryophilous fungus: rarely recorded species.” Sussex Botanical Recording Society Newsletter, no. 83 (January 2017). http://www.sussexflora.org.uk/wp-content/uploads/2017/05/Newsletter_jan_2017.pdf.

 

SEED. A botanical acronym I have coined for achievement. Serendipity, experience, expertise, diligence. Over time those of us who achieve SEED in one or more botanical disciplines will find exciting additions to the county, country or even a continent, as has happened to me. It applies the instant you leave the house or your place of residence and step out into the natural world.

On a pouring wet day in March 2016 I opened the back door and, on damp concrete where for the past 35 years my wife Louise has had various pots and troughs filled with bedding plants that are frequently watered, is a carpet of moss and liverwort. I like mosses and liverworts so they have never been scrubbed away as an unwanted annoyance; pouring with rain, too wet to venture far, so I removed a small segment of moss and looked within, what will I find? I found four species of desmid, unicellular microscopic ‘mirror image’ algae covering the common moss Amblystegium serpens (Creeping feather-moss): this in itself was a ‘first discovery’ as desmids had not been seen as an abundant associate of moss previously. Looking further I found a fungus on the tips of the rhizoids, which I eventually identified as haustoria caused by appressoria of the bryophilous ascomycete Octospora wrightii, a species only known to grow host specific to A. serpens. This was the first occasion that these rhizoidal swellings associated with O. wrightii have been seen in Britain; previously known from Austrian material (Döbbler 1979). Images of these structures have been taken by Dr Silvia Pressel at The Natural History Museum and will be published in Field Bryology, a British Bryological Society publication, entitled ‘Backdoor Botany’ I will not go into this extraordinary collection further.  However, it does whet the appetite.

Leaving the house and crossing the road into an arable field, turning sharp right and heading west to the only above ground drainage in the village, a winterbourne ditch that is filled with groundwater and rain run-off from a nearby road; as with many ancient ditches it separates two individually owned farms, one in the village of Strettington, the other in the village of Maudlin. On 1st May 2016, with water still flowing in the ditch, I waded into six inches of water to a deeper and expanded depression where in the distant past cattle would have entered the ditch to drink. Now surrounded by willows, it affords a light shade with a stand of Mentha aquatica (Water Mint) the only vascular plant growing in the water. Entwined around the mint were wefts of filamentous algae; using a x10 hand lens I thought I could see fertile oogonia spaced along the filaments and later on looking at the sample under the microscope I was able to confirm my initial observation and that I had collected the genus Oedogonia. Puzzled that I could see dwarf male filaments attached above and below the oogonia with intermixed monoicous filaments, I suddenly began to realise that I had collected three species. The species within the genus Oedogonia can only be identified with certainty if fertile and, as this is seldom so, it is reflected by the sparse knowledge of the species’ distribution in Britain.

The three species collected were O. vaucheri, monoicous and macrandrous (male and female filament of approximately the same diameter) which I had first collected in West Sussex near Fishbourne in May 2014, and prior to that collection last seen in England in 1900; O. cardiacum monoicous and macrandrous, last seen in England in 1933 and, most extraordinary, O. idioandrosporum: the second British record, the first collected in Cambridgeshire in 1899. As the name suggests this is an idioandrosporus species, i.e. species in which the spores giving rise to dwarf males (androspores) are on different filaments from those bearing oogonia. The species is also nannandrous, i.e. referring to the condition where the male filament, which is a much reduced structure, is attached to the significantly larger female filament.

Perhaps the most extraordinary fact is that within a distance of approximately 1000 metres were four species in the genus, including O. pachydermum which I collected in April 2014: this species was new to Europe, and all four species were found in temporary water bodies, floodwater and a winterbourne ditch.  What else awaits discovery? Hence SEED!

 

Reference

Döbbler, P. (1979). Nova Hedwigia Band XXXI, 4, Braunschweig. Untersuchungen an moosparasitischen Pezizales aus der Verwandtschaft von Octospora. pp. 844-46. Pl. 8: ill. 1-4, p. 845.

 

Glossary

Appressorium: a specialized cell typical of many fungal plant pathogens that is used to infect host plants.

Haustorium: a slender projection from the hyphae of a parasitic fungus, enabling the parasite to penetrate the tissues of its host and absorb nutrients from it.

Oogonium: a female gametangium producing an egg or egg cells