Welcome to the Protostelid WWW Server

from the University of Arkansas

in the Department of Biological Sciences

Keys to the genera of protostelids based on:

Sporocarp Morphology or Trophic Cell Morphology

Diagrams of Simple or Complex life cycle of a protostelid

Keys to the genera of protostelids based on Sporocarp Morphology

or Trophic Cell Morphology

1. Sporocarps multiple, supported on white to brightly colored spore horns; spore horns produced by plasmodium prior to development of prespore cells, always found on rotting wood; common......Ceratiomyxa

1'. Sporocarps single, resting directly on substrate; produced by single prespore cells; found on aerial dead plant parts, bark of living trees, bark of dead trees, litter, rotting wood, dung, or soil......goto 2

2. Sporocarps with 2-8 spores......goto 3

2'. Sporocarps with one spore......goto 7

3. Stalk long, 65-225 µm, flexuous; spores (1-) 2-4 (-8); found on rotting wood or bark of living trees; common......Protosporangium

3'. Stalk very short to up to 50 µm, relatively rigid; spores 2-4; found on aerial dead plant parts, bark of living trees, bark of dead trees......goto 4

4. Stalk bipartite, 12-35 µm, upper three quarters of its length recurved, turgid; spores 2 (-4), forcibly discharged by sudden rupture of upper segment of stalk; found on aerial dead plant parts; rare......Clastostelium

4'. Stalk of one part, straight......goto 5

5. Spores packed tightly into a spherical mass, 2-4 (may be considered a 2-4 celled single spore); stalk 10-20µm, apex tapering suddenly to a fine point; found on bark of living and dead trees; rare......Microglomus

5'. Spores individually distinct; slime sheath surrounding spores very hygroscopic, may adsorb water and swell making spore mass appear spherical, but spores individually visible in swollen sheath......goto 6

6. Spores (1-) 4 (-8), spherical, smooth; stalk gradually tapered, 15-45µm; found on aerial dead plant parts; common......Echinosteliopsis

6'. Spores 2, in a linear dyad, spherical, micropunctate; stalk tapered, 7-14µm, with small, flared apical apophysis; found on aerial dead plant parts, bark of living trees; common......Echinostelium bisporum (A myxomycete with a reduced sporocarp)

7. Spores spontaneously deciduous (detaching from stalk without mechanical disturbance by a solid object)......goto 8

7'. Spores remaining attached to stalk unless mechanically disturbed by a solid object......goto 18

8. Sporocarps ballistosporic (spores actively discharged)......goto 9

8'. Spores passively drop off or are blown from stalk......goto 11

9. Stalk straight, robust, short to moderately long, 4-60µm, remaining intact after spore discharge, with cup-like apophysis at apex; spore spherical or obovate, with ring-shaped hilum at base; droplet or bubble may appear at stalk/spore junction just prior to spore release; found on aerial dead plant parts, bark of living trees, litter; one species common, two species rare......Schizoplasmodium

9'. Stalk tortuous or reflexed, disappears upon spore discharge; sporocarps observed primarily at night and in the early morning because sporocarps develop only at night and early morning and discharge spores quickly upon maturation......goto 10

10. Stalk reflexed at midpoint, 17-35µm, basal portion thicker than apical portion; prespore cells, if seen, with central refractive papilla; found on aerial dead plant parts; uncommon......Soliformovum expulsum

10'. Stalk tortuous at maturity, 15- 32µm, tapers gradually from base; prespore cell, if seen, ellipsoid or ovoid; found on aerial dead plant parts, and dead twigs; uncommon......Protostelium nocturnum

11. Stalk long, (30-) 60-240µm, relatively robust with cup-like apophysis at apex; spore spherical or ovoid with ring-shaped hilum at base......goto 12

11'. Stalk of varying length; spore spherical, pyriform, or peanut-shaped, with rounded, apiculate, or invaginated base......goto 14

12. Spore ovate; found in litter, humus, rarely on aerial dead plant parts, common......Nematostelium ovatum

12'. Spore spherical to slightly turbinate; found in litter or on aerial dead plant parts......goto 13

13. Spore germinates as plasmodium or germling develops into cyst that produces amoeboflagellates; found on aerial dead plant parts; rare......Ceratiomyxella

13'. Spore germinates only as plasmodium; found frequently on litter, less frequently on aerial dead plant parts; common......Nematostelium gracile

14. Spore with invagination which encloses upper several µm of stalk, bell-shaped or pyriform or nearly spherical......goto 15

14'. Spore with rounded base, occasionally with apiculate extension to apex of stalk, spherical or elongated and peanut-shaped......goto 16

15. Stalk long, 30-120µm, straight, robust with pronounced widening at base and distinct particles in stalk; particles in regularly spaced swellings in most common species; spore bell- shaped or spherical, proportionally large, pendulous, waving about in slight air currents, found on aerial dead plant parts, one common species......Endostelium (in part)

15'. Stalk long, 50-100µm, curved, delicate; spore, pyriform, often reflexed at tip of stalk but not pendulous, showing little movement in slight air currents; found on aerial dead plant parts, rotting wood, litter; uncommon......Karpacanthamoeba (="Protostelium" pyriformis)

16. Spore ovate to irregularly peanut- shaped; stalk short to intermediate in length, 20-65µm, with small rounded apophysis visible when spore is shed; found on aerial dead plant parts, bark of living trees, litter; common......Endostelium arachisporum

16'. Spore spherical; stalk long......goto 17

17. Stalk (30-) 60-125µm, very straight, rigid, remaining so when spore is shed, with delicate hastate apophysis best seen after spore is shed; spore spherical, often drying into a fusiform shape perpendicular to the stalk axis while still attached; prespore cell, if seen, with central refractive papilla; found on aerial dead plant parts; very common......Soliformovum irregularis

17'. Stalk (10-) 30-75 (-100)µm, straight at base, usually curved for upper one third of its length, upper portion flexible waving around when blown upon gently, becoming tortuous and shriveled after spore is shed; stalk apex may be slightly swollen; spore spherical, often shed with uppermost 1-2µm of stalk attached; prespore cell, if seen, ellipsoid or ovoid; found on aerial dead plant parts; extremely common......Protostelium mycophaga

18. Identical to Protostelium mycophaga except spore nondeciduous; may germinate as amoeboflagellate; found on aerial dead plant parts; rare......Planoprotostelium

18'. Stalk of varying length, relatively straight, tapering to an acute point or relatively wide at apex......goto 19

19. Sporocarp with stalk rarely exceeding on spore diameter in length......goto 20

19'. Sporocarp with stalk typically several spore diameters in length......goto 22

20. Stalk 3-10µm, thick, with cup-like apophysis at apex; spore spherical with punctate sculpturing; sporocarps often densely packed on substrate; found on aerial dead plant parts; uncommon......Cavostelium

20'. Stalk (0-) 6-15µm, thin, tapering to a fine point at apex; spores with micropunctate sculpturing......goto 21

21. Spore small, 6-12µm diam.; sporocarps often packed into tight patches of a few to >100 on natural substrates; occasional sporocarps without stalks; found on aerial dead plant parts, bark of living trees, litter; common......Schizoplasmodiopsis pseudoendospora

21'. Spore large, 12-22µm diam., sporocarps scattered on natural substrates; sporcarps always with stalks; found on aerial dead plant parts, litter...... "Schizoplasmodiopsis" amoeboidea

22. Stalk coarse, tapered, but not coming to a fine point at apex, deliquesces in water; found on herbivore dung, soil, occasionally on aerial dead plant parts; uncommon......Protosteliopsis

22'. Stalk relatively delicate (at least on natural substrates), tapering to an acute point......goto 23

23. Spore spherical with coarse ridges, irregular thickenings or micropunctate sculpturing; found on aerial dead plant parts, litter; one species common, two species uncommon......long-stalked Schizoplasmodiopsis