The Phoretic Association of Urnatella gracilis (Entoprocta:Urnatellidae) and Nanocladius downesi (Diptera:Chironomidae) on Corydalus cornutus (Megaloptera:Corydalidae)

Abstract

Colonies of Urnatella gracilis Leidy and Nanocladius downesi (Steffan), Polypedilum sp. and Rheotanytarsus sp. larvae were discovered living phoretically on Corydalus cornutus (L.) larvae collected in the James River, Missouri. This is the first record for a phoretic association between U. gracilis and C. cornutus and the first record for chironomids living phoretically on C. cornutus in Missouri. Phoresy seems to provide U. gracilis with mobility and despersal within and out of the original habitat, protection from predation and habitat stability. Colonies in close proximity to the ventral abdominal gill tufts may also be provided with a constant source of oxygen-rich water containing food particles. Chironomid larvae were also in close proximity to the gill tufts but no specific segment site of attachment was observed.