174
PROCEEDINGS OF THE HELMINTHOLOGICAL SOCIETY
meyeri (Fig. 4). Intraspecific variation has been
reported for external markings (Meyer, 1946, J.
Parasitol. 32:467-476), ratio of body and sucker
diameter to length (Moore and Meyer, 1951,
Wasmann J. Biol. 9:11-77), and annulation
(Meyer and Roberts, 1977, Univ. Nacional Mex.
Inst. Biol. Publ. Esp. 4:513-519). Interpretation
of such variable or "changeable" features in these
soft-bodied animals is further complicated by
fixation artifact, as improper preservation may
cause gross distortion of specimens or fading of
pigmentation (Meyer, 1965, Atlantide Report No.
8:237-245, Danish Scient. Press, Ltd., Copenhagen). For these reasons, size or external markings should not be the sole criteria for classification of leeches. Such characters should be used
with caution and observations made on a representative sample of the population rather than
single specimens.
Recognizing that internal organs are less susceptible to fixation artifact, Johansson (1898,
Zool. Anz. 21:581-595) suggested a classification
of the Piscicolidae based primarily upon internal
anatomy. However, since the internal anatomy
of many species has not been fully described, a
comprehensive revision of the family on this basis is not possible. Likewise, the promising techniques of karyotype analysis and isoenzyme electrophoresis are limited in practical application
because they generally require fresh material. Although very subtle interspecific differences may
be detected by these methods, data can be obtained only from newly collected specimens.
Thus, at present, taxonomists have no alternative but to rely upon characters of external morphology despite their obvious shortcomings.
Specimens were collected and examined in collaboration with Dr. John S. Mackiewicz and Dr.
Anthony J. Grey, State University of New York
at Albany. Dr. Marvin C. Meyer, University of
Maine at Orono, provided assistance with the
original species description and shared with me
his extensive knowledge of the literature. This
work was supported, in part, by Grant No. 20A022-A from the Research Foundation of the
State University of New York to Dr. Mackiewicz, and by a Grant-in-Aid-of-Research from
the Society of the Sigma Xi to the author.
Proc. Helminthol. Soc. Wash.
51(1), 1984, pp. 174-175
Research Note
SEM of Tapeworm Flame Cells
WILLIAM H. COIL
Systematics and Ecology, University of Kansas, Lawrence, Kansas 66045
Parasitologists have been intrigued by the nature of the platyhelminth flame cell—the morphology, the taxonomic significance of the "flame
cell formula," the possible function in osmoregulation and/or in excretion, etc. This interest is
illustrated by numerous literature citations, but
the landmark papers are those of: Kiimmel (1958,
Z. Naturf. 136:677-679), Wilson (1969, Parasitology 59:461-467), Howells (1969, Parasitology
59:449-459) and Wilson and Webster (1974, Biol.
Rev. 49:127-160). More recent contributions are
those of Gambrion (1981, These, Montpellier,
France) and Rohde (1982, Prog, and Abstr., Fifth
Int. Cong. Parasitol., Toronto, Vol. II, p. 99). All
of the above references are based on TEM studies.
The data presented here are the result of scanning electron microscope studies on Dioecocestus
acotylus and Schistotaenia tenuicirms that were
prepared by ethanol cryofracture for embryoJogical studies (Coil, 1979, Z. Parasitenk. 59:151159).
Basically, the terminal organ consists of a cell
body that extends from the base of a parenchymal crater (Fig. 1). Internally, and not seen here,
the cell body bears a tuft of typical, but fused
cilia that project into the tubule. The distal end
of the tubule is composed of two parts: (1) an
Copyright © 2011, The Helminthological Society of Washington
OF WASHINGTON, VOLUME 51, NUMBER 1, JANUARY 1984
175
Figure 1. Schistotaenia tenuicirrus. SEM of ethanol cryofracture showing flame cell body and distal tubule.
Terminal part of cell body was lost during cleavage. Scale bar equals 1 ^m. CB —cell body, M —muscle, N —
nephrostome, PC —parenchymal crater, and S—slits.
external, corrugated barrel that is derived from
the tubule, (2) an internal series of bars that are
derived from the flame cell body (Wilson, 1969,
loc. cit.). The internal bars form a covering for
the slits that are seen around the circumference
of the barrel. The barrel extends over the cell
body forming a cytoplasmic fold beneath which
lies the nephrostome (Howells' term, 1969, loc.
cit.).
The cleavage of worm tissue to reveal flame
cells is a fortuitous event and the subsequent
viewing of the terminal organ is a matter of
chance. External leptotriches as reported by
Kiimmel (1964, loc. cit.) in Fasciola and by
Lumdsen (1981, Hymenolepis diminuta, Academic Press) were not seen on the bars between
the slits in the species studied here. The structures are not highly developed in the cestodes,
but at the magnifications used here they would
be visible. The number of slits is close to 40 based
on extrapolations; in no case were all the slits
visible in one flame cell.
It should be noted that the genera studied here
(Dioecocestus and Schistotaenia) must be considered as bizarre tapeworms (unusual, at least)
with a number of attributes not ordinarily seen
in "typical" tapeworms. For example: (1) they
lack vaginae, (2) both infect primitive hosts
(grebes), (3) one is dioecious, etc. (Coil, 1970, Z.
Parasitenk. 33:314-328; Boertje, 1974, Proc. La.
Acad. Sci. 37:89-103). On the basis of only a few
studies on tapeworm flame cells, it would be premature to conclude that the flame cells here represent the primitive (plesiomorphic) condition
by lacking the leptotrichs, but this is an interesting idea that may warrant further study. This
is especially true since Rohde (1980, Angew. Parasitol. 21:32-48; 1982, loc. cit.) has proposed
that relationships among the platyhelminths can
be discerned by a study of the morphology of the
flame cells.
Copyright © 2011, The Helminthological Society of Washington