A mention of the INHS collections elicits visions of glass-topped Cornell cases stacked 10 feet high, holding rows of pinned and carefully labeled butterflies, beetles, and other insects. Perhaps a visitor will see drawers of carefully stored birds and small mammal skins, each stuffed with cotton and awaiting study. Shelves of glass jars and vials hold small invertebrate animals and primitive plants in preservative fluids, as well as pressed and dried herbaceous plants in a neatly organized herbarium. In addition to these dead and preserved biological wonders, INHS houses other kinds of collections, some of which may be a surprise to visitors. One such collection is probably the world's largest and most diverse accretion of living entomopathogenic microsporidia, protozoa-like organisms that cause chronic or acute disease in insects.
Microsporidia are single-celled organisms with one or two nuclei and are always parasitic. They are sufficiently unique to be assigned to their own phylum, Microsporidia (formerly Micro-spora). Approximately 1,000 species have been described, most from insects and other invertebrates, but species have also been found infecting most other animal groups, including man. Microsporidia are typically host-specific and those species collected from insects cannot survive the warm body temperatures of mammals and birds. The "mature" forms of microsporidia are environmentally resistant spores or "environmental spores." Millions of these spores are produced per individual host late in the infection process and enter the environment via feces, silk trails, or decomposed tissues of dead hosts. Other individuals of the same host species become infected when they ingest these spores. Many microsporidian species are also transmitted from infected females to their offspring inside or on the surface of the eggs.
Unlike preserved collections, the different species of micro-
sporidia in
the INHS collection are kept in a living state, cryofrozen at -321[[ring]]F in
liquid nitrogen. Approximately 1,000 samples, representing more than 100
species of microsporidia, have been collected over the past 30 years.
Environmental spores are suspended in purified water and placed into small
polypropylene cryovials. The vials are snapped onto a stainless steel "cane"
and suspended in liquid nitrogen tanks. Our studies have shown that by adding
50% glycerin by volume and a small amount of antibiotic and fungicide to each
cryovial to retard bacterial and fungal growth, the spores will live almost
indefinitely in a state of suspended metabolism. Spores we tested after 25
years of storage were still viable and infected their hosts when ingested.
Specimens from the collection at INHS are used by insect pathologists all over
the world. We provide spores to our research cooperators for studies in
systematics and evaluation as possible biological control agents for insect
pests. We investigate the infective processes of
Stephen Lavallee (left) and Diego Roman
of INHS store insect pathogens in a liquid
nitrogen tank.microsporidia to determine
the effectiveness of these diseases in reducing insect populations. In
addition, we can make comparisons between species of microsporidia using
techniques that were not available when the microsporidia were first collected.
Another function of the insect pathology laboratory staff is to assist persons
rearing insects for scientific or commercial endeavors who discover unwanted
diseases in laboratory colonies or beneficial insects. The collection is a
valuable resource for insect pathologists and for studies of these fascinating
organisms.
Leellen F. Solter and Joseph V. Maddox, Center for Economic Entomology
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