Parasitic association of Nanocladius (Diptera : ...
|Title||Parasitic association of Nanocladius (Diptera: Chironomidae) and Pteronarcys biloba (Plecoptera : Pteronarcyidae): insights from stable-isotope analysis|
|Author(s)||R. Doucett, D. Giberson, G. Power|
|Journal||Journal of the North American Benthological Society|
|Abstract||Nymphs of Pteronarcys biloba Newman and attached chironomid larvae (Nanocladius [Plecopteracoluthus] undescribed sp, nr. branchicolus) were collected from Catamaran Brook, New Brunswick, in May and November 1997 for stable-carbon- and stable-nitrogen-isotope analysis. Nanocladius (P.) sp. had mean (+/- SD) delta(13)C and delta(15)N values of -27.7 +/- 1.0 parts per thousand and 4.9 +/- 0.6 parts per thousand, respectively, whereas those of P. biloba were -28.4 +/- 1.0 parts per thousand and 1.3 +/- 0.7 parts per thousand, respectively. Nanoclaudius (P.) sp. always had more positive delta(13)C and delta(15)N values than P. biloba, and average fractionation factors (isotope differences between symbiont and host) were +1.2 parts per thousand and +3.5 parts per thousand for carbon and nitrogen, respectively. These results confirm a parasitic relationship between Nanoclaudius (P.) sp, and I! biloba. No statistical differences were found among the delta(13)C values of the plecopteran shredder in 4 stream reaches from headwaters to mouth, and delta(13)C values were similar to those of their expected leaf litter diet. Pteronarcids from the headwater site (Upper Reach) were not parasitized and had distinct delta(15)N values from those at downstream sites. However, stable-isotope ratios of parasitized stoneflies were not significantly different from those of non-parasitized individuals at the 3 other study locations. Nanoclaudius (P.) sp. were more enriched in N-15 than other chironomid genera in Catamaran Brook, including Ablabesmyia, a chironomid with predatory feeding habits, and fell within the range of: other known invertebrate predators. These findings highlight the usefulness of stable-isotope technology to distinguish between phoresy and parasitism in ectosymbiotic relationships among aquatic organisms.|
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