Comparative Parasitology 68(2) 2001 - Peru State College

GIBLIN-DAVIS ET AL.—CUTICULAR CHANGES IN FERGUSOBIID NEMATODES 247
harenkova and Chizhov, 1991, and Allantonema
rnirabile Leuckart, 1884 (Allantonematidae),
were similar to those of P. nicholasi, being composed
of a hypertrophied epidermis with microvilli
that was covered by a cuticle-like layer
(Subbotin et al., 1994).
Insect hemolymph characteristically has high
levels of amino acids, trehalose, other nonamino
organic acids, and salts (Chapman, 1972), making
it a nutrient-rich environment for parasites
that can overcome innate host defense mechanisms.
Insect-parasitic tylenchid nematodes have
adapted to the challenges of obtaining nutrition
from a living insect host in a variety of ways,
including acquisition per os (through the
mouth), through a modified or absent cuticle, or
through prolapsis and modification of the uterus
as in the Sphaerulariinae (Sphaerulariidae). Tylenchids
from the Neotylenchidae, Allantonematidae,
lotonchiidae, and Parasitotylenchidae
have insect-parasitic forms that are obese and
have degenerate esophagi, intestines that are degenerate
or modifed as storage organs, and the
stylet often sunken into the body or even lacking
(Siddiqi, 2000), suggesting that they employ
some form of transcuticular or transepidermal
uptake.
Deladenus (Neotylenchidae), Paraiotonchium
(lotonchiidae), Howardula (Allantonematidae),
Skarbilovinerna (lotonchiidae), and Fergusobia
(Neotylenchidae) may represent contemporary
examples of an evolutionary trend from per os
to transepidermal nutrient acquisition in insectparasitic
Tylenchida. Of course, this is a highly
speculative exercise until more information
about the transition between preparasitic and
parasitic females is known and some independent
phylogenetic data are available. The evolutionary
trend is hypothesized to be: 1) Per os
acquisition via a stylet, esophagus, and gut. This
strategy takes advantage of the existing stylet for
feeding on fungi, plants, or other invertebrates.
It is a less energy- and time-efficient method of
nutrient acquisition for a hemocoelic parasite because
obtaining food through the stylet requires
expending energy to maintain and operate its
esophagus and intestine. 2) Per os acquisition
with thinning and partial apolysis of the cuticle
and coincident epidermal folding to increase surface
area for supplemental transcuticular uptake
of nutrients (possibly Deladenus spp.). 3) Early
per os acquisition followed by apolysis, partial
absorption of the cuticle without the creation of
a new cuticle, and folding of the epidermis such
that uptake is transcuticular and somatic muscles,
esophagus, and gut degenerate (e.g., Paraiotonchium).
4) Early per os acquisition followed
by full apolysis and ecdysis without the
creation of a new cuticle. There is hypertrophy
and folding of the epidermis, and nutrient uptake
is transepidermal, somatic muscles and esophagus
degenerate, and the gut degenerates or is
transformed into a storage organ (e.g., Howardula,
Skarbilovinema, and Fergusobia). The epidermal
hypertrophy and folding are superficially
similar to the formation of plicae (epidermal
folds) during the development of a new cuticle
(Bird and Bird, 1991) but are more extensive
and apparently are not accompanied by the formation
of a new cuticle.
Acknowledgments
We thank Drs. Bill Howard and Thomas
Weissling for review of the manuscript and Matthew
Purcell, Jeff Makinson, and Dr. John
Goolsby for making the senior author's visit to
the Australian Biological Control laboratory in
Indooroopilly, Queensland, Australia, such a
productive and enjoyable experience. This project
was funded in part by USDA-ARS Specific
Cooperative Agreement No. 58-6629-9-004
from the USDA Invasive Plant Research Laboratory
in Davie, Florida, U.S.A. This is Florida
Agricultural Experiment Station Journal Series
No. R-07870.
Literature Cited
Bird, A. F., and J. Bird. 1991. The Structure of Nematodes,
2nd ed. Academic Press, Inc., New York,
U.S.A. 316 pp.
Chapman, R. F. 1972. The Insects: Structure and
Function. American Elsevier Publishing Co., Inc.,
New York, U.S.A. 819 pp.
Currie, G. A. 1937. Galls on Eucalyptus trees: A new
type of association between flies and nematodes.
Proceedings of the Linnean Society of New South
Wales 62:147-174.
Giblin-Davis, R. M., K. A. Davies, G. S. Taylor, and
W. K. Thomas. 2001. Entomophilic nematode
models for studying biodiversity and cospeciation.
Pages 00-00 in Z. X. Chen, S. Y. Chen, and D.
W. Dickson, eds. Nematology, Advances and Perspectives.
Tsinghua University Press/Springer-
Verlag, New York, U.S.A. (In press.)
Maggenti, A. R. 1982. General Nematology. Springer-
Verlag, New York. 372 pp.
Nicholas, W. L. 1972. The fine structure of the cuticle
of Heterotylenchus. Nematologica 18:138-140.
Poinar, G. O., Jr. 1979. Nematodes for Biological
Copyright © 2011, The Helminthological Society of Washington