Book of Abstracts (PDF) - International Mycological Association

IMC7 Tuesday August 13th Lectures
septate thalli that produce arthrospores in their fertile
branches. They attach through holfast cells that have
unique morphology commonly used for species
identification. Sexual reproduction is not known for either
group. No species of either order has been axenically
cultured so far. Most of their taxonomy, if not all, is based
on a few micromorphological characters. Molecular
markers have been developed to study the relationship of
these orders to other groups of fungi. Ribosomal gene (18S
and 28S) sequence analyses do not support a close
association of these orders to the Harpellales, their putative
sister taxon.
150 - Recent advances in trichomycete ecology and
physiology
C.E. Beard 1* , P.H. Adler 1 & J.W. McCreadie 2
1 Clemson University, Department of Entomology, Clemson,
SC, 29634-0365, U.S.A. - 2 University of South Alabama,
Department of Biological Sciences, Mobile, AL, 36688,
U.S.A. - E-mail: cbrd@clemson.edu
Although the systematics of trichomycetes represents a
fairly mature level of knowledge, studies of trichomycete
ecology and physiology have lagged behind. To address
this imbalance, we have investigated the ecology of
trichomycetes and aspects of their physiology. We asked
whether the distributions of trichomycetes in time and
space were predictable. A two-year study revealed that the
prevalence of trichomycetes inhabiting black flies is related
to season. In some streams, Harpella melusinae was most
prevalent in spring and fall. Efforts to relate prevalence to
environmental characteristics showed that the prevalence
of H. melusinae is greatest in mountain streams. Prevalence
of this species in the black fly Simulium tuberosum is
related to stream pH and conductivity. We also investigated
physiological aspects of establishment of trichomycetes in
hosts. Zygospores of H. melusinae and Stachylina spp. are
rare, but formation can be stimulated by elevated levels of
potassium and pH (as KOH). Smittium megazygosporum
has a disjunct distribution and large zygospores (150 µm
long). Large zygospores might enable trichomycetes to
persist in the environment. The role of zygospores in the
life history of trichomycetes remains unclear. Smittium
culisetae inhabits specific regions of the host hindgut,
which might be related to the timing of spore germination
as spores transit the gut. Nutritive characters of the hindgut
regions might determine which areas are habitable.
151 - Dispersal mechanisms in species of Harpellales
A.M. Rizzo * & S.T. Moss
University of Portsmouth school of Biological Sciences,
King Henry St. Portsmouth PO5 3EN, U.K. - E-mail:
alan.rizzo@port.ac.uk
Fungi of the Harpellales (Trichomycetes) live attached to
the mid-gut (Harpellaceae) and hind-gut
(Legeriomycetaceae) of their dipteran hosts. The hosts
include species of both simuliid and culiciid vectors for
river blindness and malaria respectively. Transmission of
these fungi within host populations is by means of
asexually produced sporangia termed trichospores. These
spores are produced by the thallus within the host gut.
Light microscopic images of these spores from
representative genera will be shown and an explanation
made of the mode of transmission and infection. Some
members of the Harpellales have a chlamydosporic stage
which is associated with the eggs of host Diptera. These
spores are thought to provide a means of dispersal to new
or ephemeral habitats. Data relating to the occurrence of
these spores at various collection sites will be presented.
Light and scanning electron micrographs showing the
structure of this stage will also be provided for three
species of the Harpellales: Genistellospora homothallica,
Harpella melusinae, Smittium sp. Results of infection trials
in order to establish positively a process for reinfestation
within the host by these spores will be given. The
mechanism(s) by which species of the Harpellales invade
the tissue of the adult fly is unknown. Transmission
electron micrographs of pupae and gravid adults will be
provided to show a possible pathway of infection.
152 - Selected habitats of Xylaria species of Mexico
F. San Martín 1* , J.D. Rogers 2 & P. Lavín 1
1 BIOTA, Sierra Hermosa 617 Fr. Villa Real. Cd. Victoria.
Tam. 87027, Mexico. - 2 Washington State University,
Pullman, WA 99164-6430, U.S.A.
Due to its diverse floristic composition, México is, perhaps,
the area of the New World with more species of Xylaria. In
this contribution, 50 species of Xylaria are reported
growing on different habitats, i.e., on wood and fruits of
Quercus spp., on Guazuma ulmifolia, Liquidambar
styraciflua and Magnolia spp. fruits, on pods and pod-like
structures, on fallen leaves, on wood of several dicots and
monocots, on different fruit remains and soil and dung.
Morphologic and host relationships are presented for the
following species of Xylaria: X. adscendens, X. alata, X.
albisquamula, X. amphithele, X. apiculata, X. aristata, X.
castilloi, X. coccophora, X. delicatula, X. dichotoma, X.
diminuta, X. duranii, X. enteroleuca, X. equina, X.
eugeniae, X. feejeensis, X. cf. filiformis, X. gracillima, X.
guazumae, X. inaequalis, X. ianthino-velutina, X. ianthinovelutina
large-spored variety, X. jaliscoensis, X. juniperus
var. asperula, X. lancea, X. liquidambar, X. longiana, X.
longipes, X. magniannulata, X. magnoliae, X. cf.
magnoliae, X. mexicana, X. michoacana, X. microceras, X.
multiplex, X. oxyacanthae, X. palmicola small-spored
variety, X. perezsilvae, X. phyllocharis, X. poitei, X.
rhizomorpha, X. quercinophila, X. sp. aff. hypoxylon, X. sp.
aff. longiana, X. sp. cubensis complex, X. scabriclavula, X.
cf. scruposa, X. striata, X. subcoccophora, and X.
tumulosa.
Book of Abstracts 49