8
ACADEMY OF SCIENCE POR 1950
ON THE STRUCTURE OF PROTOZOAN FLAGELLA
BARLEY P. BROWN, UDlyendly of Oklahoma, Norman
Among the flagellate micro-organisms (protozoa, algae, swarm spores of
fungi, etc.> there exists a diverse assortment of flagellar types. One type of
flagellum is somewhat feather-Uke. It has a shaft composed of a fibrillar
core or axoneme enclosed by a sheath, and along one or both sides of the
flagellum there extend many delicate fUaments. A German worker (3), describing these filaments long ago, called them "FUmmer." Cox (2) and Brown
,1) employ this wklelY-Wled term in preference to various others which have
been introduced. Euglenolds generally possess a flagellum with a single row.of
filmmer along one side. The chrysomonads or yellow-brown algae commonly
exhibit one short simple flagellum and a relatively long flimmer-flagellum with
fUaments on both sides. Cox (2) is the first to demonstrate the presence of
fUnuner upon cryptomonad flagella. They appear to be distributed along the
flagellum somewhat as in Euglena, although they seem to be sturdier than
th05e of the euglenoids.
There is no general agreement, as yet, concerning the nature and significance of filmmer. We do not know how they are formed or what functions
they perform, if any. It is not even known with certainty whether they occur
upon the flagella of normal UVing flagellates. What is proP05ed in this paper
is one hypothesis concerning the possible nature of filmmer and their mode ot
formation. It is based upon electron micrographs of the flagella of various
protozoa, but especially upon those of Ochromonas variabUis Meyer (Order
Chrysomonadina) depicted by Brown (1) and Cox (2), upon suggestions by
Owen (5) and Pitelka (6), and upon a vivid imagination. The hypothesis is as
follows:
fibrils of axoneme ,.
., .,
."
- ..... sheat h " ,.
granule
FIGURE 1
FIGURE Z
10
PROOBBDING8 OP TBB·OKLAHOMA
The bualgranule, a deeplY-ltalnlng body ui the cytoplasm at the base of the
naaeUum, contalDl a cluster of about a dozen "fibril factories." (Bee Pig. 1.)
Bach of these "faeten1es" eonaIate of enzyme molecules wbleh "manufacture"
protein mlce1Jel or fibrill. AI the flbr111 are pushed out toward the cell 8Ulfaee
aDd beyond, the cell membrane and a layer of cytoplasm are carried outward,
form1ng the flagellar sheath. The bundle of flbrill forms the axoneme of the
IJ'OW1DI flaIeUum. A amaller group of "flbrll factorles"-let us say three-is
extruding another bUDdJe of fibrill at the I8D1e time. 'I1Us second factory
clUlter 1.1 c10ler to the cell membrane, baa greater acceas to oxygen dlffusing
Inward, and thus, with a higher metaboUc rate than the basal granule, extrudes
ita fibril bundle lOJDewhat more rapidly than does the basal granule. This
difference in growth rate results in a coUlng of the IUperfic1al flbrlls about
the axoneme, and produces a fibrous hellx in the sheath.
Under certain conditions (perl1aps in the normal, active organism), the
fibrill of the .heath fray into individual micelles which commonly remain
attached only at one end (Plg. 2). Thele are the fUmmer. One, two, or all
thn!e of the parallel micelles may tray out in any given region along the
flapllum. If, during drying (as in the preparation of specimens for electron
m1cr'oIcopy), the sheath membrane shrlnka back toward the axoneme, bumps
or ridges remain in the region of the heUcal flbrlls, and the fUmmer arise from
these bumps, as seen in M1as Cox's micrographs (2).
AI indicated before, the above account is purely hypothetical. However, a
few points which fit into 8uch an interpretation might be mentioned. The
len,th and location of the ntmmer, as seen in electron micrographs, are Just
·rla'ht for such an interpretation. The diameter of the ntmmer, which we
eatlmate at about 0.02 or 0.03 micron, 18 within the range cited for axial
· (axoneme) fibrill of various protozoa by other investigators (e.g., 0.025 - 0.04
·micron 18 cited &8 the diameter of axial flbrlls of Trlchont/mpha flagella by
SChmitt, Hall, and Jakus, (8) ). VarioUB proteins, including myosin, collagen,
and fibrin, commonly form fibrils of these dimenalons (4, 7).
If the unilateral fl1mmer of ChUomo7UU and the euglenoids originate in the
manner here hypothea1zed, each micelle represents one entire hellcal turn
around the flaaellum, lnBtead of a half-tum as diagrammed for Ochro1n01lal.
AlIo, the coila of the he1lX must be closer together than inOchromoncu. Perhaps
the types of flagella which do not exhibit fl1mmer have a non-fibrous sheath.
LITERATURE CITED
1. BROWN, ILuLJry P.
UM5.
tozoan flarellum. Ohio J.
On the structure and mechanics of the proSCt. 45 (6): 247-301.
2. Cox, AVALa. 1960. A study of protozoan flagella. Master's Thesis, University of Oklahoma, Norman.
3. PIacBD. A. 18M. ttber die Gel&seln elnlger Flagellaten. Prlngshelms
Jahrb. f. wlaB. Bot 26: 18'7-235.
4. HALL, C. a, M. A. JAKtTs. and P. O. 8cH1O'l'T. 1946. An investigation of
crou striations and my08ln fUaments in muscle. BioI. Bull. 90 (1): 32-50.
S. OWD, H. MncoUi. IM7. Flagellar structUre: t. A c:U.scus8lon of fixation
and stalnIDg of the protozoan flagellum. Tran8. Am. Mlcr. Soc 66 (1):
SO-58.
e. PIftuu, DoaO'l'JlT R. lM9. Observations on flagellum structure in
P1agellata. Unlv. C&11f. Pub!. in ZOOl. 53 (11) : 37'1-430.
7. ·RoaA, G., A. s.nt-OJ6rIyt, and R. W. G. Wyckoff. 1950. The fine
structures of myoftbrUa. Exp. cen Research 1 (2): IM-205.
.. 8cIDDft, P.O., O. It HALL, and Y:. A. JAKV8. 1M3. The ultrastructure of
DI'Otoplaamlc tlbrlls. BlolOlical Symposia 10: 281-278.