Abstract Detail

Ecology/Pathology

Beard, Charles E [1].

Nutritional sources for the trichomycete fungus Harpella melusinae.

The trichomycete fungus Harpella melusinae is common in midguts of aquatic larval black flies. H. melusinae is generally considered to have a commensal relationship with its hosts, but little is known of its nutritional relationship with the hosts. Taxonomic resolution of species in the genus has been difficult due to limited and variable morphological features and difficulty extracting DNA for genomic analysis. One way to provide tools for addressing questions about the fungus would be to grow cultures. However, H. melusinae has defied efforts to isolate and culture it in vitro. We have, therefore, tried in vivo assays to shed light on the nutritional sources. By providing different nutritional sources to hosts with H. melusinae and observing fungal growth characters, optimal food sources might be determined. Finding components in the stream that provide the best growth for the fungus in the host gut will provide information on nutrition sources for in vitro cultures. Typically, laboratory black flies are grown with a fish food diet, which supports H. melusinae growth in the larvae, but fish food does not support in vitro growth of H. melusinae. We hypothesize that biofilms might be an important source of nutrition for H. melusinae. Therefore, we developed a food recipe which should mimic aspects of biofilms as a nutritional source. Black fly larvae (Simulium innoxium) with H. melusinae were field collected and placed in feeding containers. Food sources were provided and growth of H. melusinae was assayed (spore production and recolonization). The growth of H. melusinae did not qualitatively differ based on food source for the host larvae.  Since biofilm components did not enhance growth, we reject the hypothesis that biofilms are a better nutritional source. The control, unfed larvae, also supported growth of H. melusinae, indicating that H. melusinae might be using components intrinsic to the host and rather than depending on stream nutritional materials. This result raises the possibility of a mild parasitic relationship. Anecdotal assays support this possibility; larvae collected during periods of reduced host growth sometimes show lower colonization levels. 

1 - Clemson University, School of Agricultural, Forest and Environmental Sciences, E143 Poole Ag Center, Clemson, SC, 29634, USA

Keywords:
trichomycetes
symbiosis
Diptera
aquatic.

Presentation Type: Offered Paper - Paper
Session: 1
Location: Room 103 AB/Kellogg Hotel and Conference Center
Date: Monday, June 9th, 2014
Time: 9:15 AM
Number: 1004
Abstract ID:141
Candidate for Awards:None