Effects of pH on the Biology and Distribution of Ephemerella Funeralis (Ephemeroptera)

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Abstract
Life history emergence, sex ratio, fecundity, food habits, microhabitat, distributional pattern and effects of experimental acidification on the emergence, growth and recruitment of E. (Eurylophella) funeralis McD. are reported. E. funeralis is the only member of the Ephemerellidae known to have a 2 yr life cycle. Emergence of adults was recorded from June 1-July 11 in the Hubbard Brook [New Hampshire, USA] watershed. Larval sex ratio from all study sites was approximately 1 male for every 8 females. Adult sex ratio was site dependent, with males increasing in representation as stream size decreased. Average number of eggs per female was 1853 .+-. SE 87. Facultative parthenogenesis is indicated by the development of 53% of 381 eggs taken from an unmated female sub-imago. Larvae were in accumulations of organic matter in slower flowing portions of streams and also in permanent woodland pools. Gut contents of larvae were composed of detritus and decomposing higher plant matter (especially leaves) and fungal growth of submerged wood. E. funeralis apparently decreases in abundance with decreasing stream pH and organic matter. Experimental acidification of Norris Brook had no effect on the emergence of adults but caused a decrease in growth and nearly eliminated recruitment of the new cohort. A direct relationship between pH and the abundance of E. funeralis in the Hubbard Brook watershed is indicated by the results.