PROC. ENTOMOL. SOC. WASH. 105(3). 2003, pp. 794-796 Note Bdelloid Rotifers (Rotifera: Bdelloidea) Inhabiting Larval Black Flies (Diptera: Simuliidae) and Their Effect on Trichomycete (Zygomycota) Fungal Abundance Black fly larvae (Diptera: Simuliidae) are restricted to lotic habitats where they an-chor themselves with a silken pad spun onto solid substrates (e.g., rocks) and filter food from the water column (Adler and Mc-Creadie 1997). Symbiotic relationships have evolved between black flies and other organisms, including, bacteria, fungi, nem-atodes, viruses, and protozoans (Crosskey 1990). During laboratory investigations of endosymbiotic trichomycete fungi of the genus Sinittium (Zygomycota: Trichomy-cetes) and the larval black fly SiuniUuni vit-tatiini Zetterstedt cytospecies IS-7, we found bdelloid rotifers (Rotifera: Bdello-idea) in the simuliid larval midgut (Fig. 1 ). Here we report the first record of this as-sociation and provide evidence that the presence of rotifers in the larval midgut in-fluences the ability of Sinittium to establish in the hindgut. Larvae of Siinuliuin vittatum cytospecies IS-7 were reared from eggs obtained from a parasite-free colony housed at the Uni-versity of Georgia (Athens, GA, U.S.A.). Approximately three weeks after submer-gence of eggs in 500 ml of aged tap water maintained at 22°C (Percival® incubator. Model: 1-36 VL), 40 larvae each were placed in 1-L polypropylene containers with 500 ml of aged tap water and moved to another incubator All containers were aerated with aquarium pumps, and larvae were fed daily on a fish food slurry (McCreadie and Colbo 1991). Fungi were reared on plates of 1/10 Brain Heart Infusion agar (Difco® 235-500: 0037-17) at room temperature (22-25°C) with sterile water overlays added to induce trichospore production. Trichospores are single sporangia, each housing a single spo-rangiospore and are the asexual infective stage of trichomycete fungi (Lichtwardt 1986). Once the trichospore enters the black fly larval hindgut, the sporangiospore ex-trudes, attaches to the cuticle, and produces a new thallus. In our experiments, a dosage of 4,000 trichospores/ml of rearing water was used. To determine fungal abundance in hosts, larvae 4 days after inoculation were dis-sected in a drop of distilled water and the mid-and hindguts removed. Under phase-contrast microscopy, the hindgut was viewed at 400X through a 10 mm X 10 mm ocular grid. The number of grid squares that contained one or more hyphae were count-ed; relative abundance was expressed as the percentage of grid squares containing hy-phae. During routine dissections in three experiments, four different treatment con-tainers, out of 36, had larvae with active bdelloid rotifers in their midguts. In exper-iments 1 and 2, one out of 12 containers in each experiment had larvae with rotifers: in experiment 3, two out of 12 containers housed infected larvae. A total of 186 lar-vae were examined from these containers and 37 (19.9%) contained rotifers; abun-dance of bdelloids ranged from to 24 in-dividuals per larval host. Rotifers used a telescoping-type locomotion and fed on green algae in the simuliid midgut. Al-though the identity of the rotifers remains unknown, they possess characters consis-tent with the family Philodinidae (Wallace and Snell 2001). Whether the black fly lar-vae acquired bdelloids before or after tri-chospore inoculation, is unclear. Bdelloid rotifers are free-living inverte-brates that inhabit aquatic vegetation, sedi-ment of lentic habitats, moist forest soils (Wallace and Snell 2001), and even the sur-face of freshwater insects and crustaceans
Bdelloid rotifers (Rotifera: Bdelloidea) inhabiting larval black flies (Diptera: Simuliidae) and their effect on trichomycete (Zygomycota) fungal abundance
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