Calomyxa metallica (Berk.) Nieuwl.

Nieuwland 1916: Amer. Midl. Nat. 4: 335
Basionym: Physarum metallicum Berk. 1837: Mag. Zool. Bot. 1: 49
Type loc.: England, Nottinghamshire, Clifton.
Mycobank #100143

The genus Calomyxa is monotypic with the only species C. metallica (Berk.) Nieuwl.

Sporocarps globose or slightly depressed globose, sessile on a narrow base, solitary or in small groups of up to 5 sporocarps, medium grey with slight orange tint, with metallic lustre and often shining brightly, 0.5-1 mm Ø

Hypothallus inconspicuous, at most a narrow somewhat brownish rim around base of sporocarp

Peridium thin, membraneous, pale greyish yellow to bright golden yellow by TL, dehiscing irregularly, shining yellowish flakes often remaining fixed to sporocarp.

Capillitium of long, thin entangled solid threads, 1-2 µm broad, regularly roughened of short, blunt spines, ocassionally only on one side of thread, pale greyish yellow to golden yellow by TL.

Spores globose to slightly ellipsoid, light greyish with slight rosy tint by RL when fresh, fading to dull grey with orange tint, very pale yellowish grey to almost hyaline by TL, with regularly distributed, medium sized, short spines, 10.5-11.3-12.5 µm Ø (excl. spines, n=25)

On bark and cones of coniferous trees, generally Picea, but also on wood of various deciduous species.

Danish collections have exclusively been made during mild winter months, november through march.

Distribution in Denmark
Rarely collected, only about 10 finds from central Jylland and north Sjælland, but probably widespread througout the country.

Global distribution
Reported from many countries in Europe and several states in USA, Russia and China. Except for finds from new Zealand and Nouvelle-Calédonie the species seems confined to the northern hemisphere.

The apparent scarcity in Denmark is probably du to the fact, that C. metallica fructifies during the winter months, a period with little myxomycete collecting activity.
Some of the Danish finds are from piles of Picea branches left on the ground when the trees are cut or thinned. Such a substrate is found in practically all Picea plantations and would most likely reveal several new finds, if searched.
In the field, the combination of ± globose sporocarps with metallic lustre and the time of year makes this species fairly easy to identify. The only obvious source of confusion is Prototrichia metallica, which occurs in small to fairly large groups and is far more seldom.

Description and discussion based on 4 Danish collections: hfg 1798, hfg 1841, hfg 2219 and hfg 2451, the last mentioned collection is unusual rich with more than 20 sporocaps scattered on the undeside of a Picea cone on the ground.


Abbreviations: TL : transmitted light; RL : reflected light; Ø : diameter; TBU : Danish Botanical Topographical District.

Colour-codes refer to: Kornerup, A. & J. H. Wanscher 1974: Farver i farver. 5th reprint. Politikens Forlag, Copenhagen.

When not otherwise indicated spore measurements are given as: min-mean-max or (extreme-)min-mean-max(-extreme). Spore measurements are exclusive of ornamentation.

Line drawings are free hand sketches.

Distribution maps: Maps of Danish distributions are based on material seen by the author. World distributions are based on reports extracted from literature.

Calomyxa metallica:
Calomyxa metallica (Berk.) Nieuwl. - Sporocarps (hfg2451)
Sporocarps (hfg2451)
Calomyxa metallica (Berk.) Nieuwl. - Spores (hfg2451)
Spores (hfg2451)
Calomyxa metallica (Berk.) Nieuwl. - Capillitium and spores (hfg2451)
Capillitium and spores (hfg2451)