Analysis of a northern mayfly (Ephemeroptera) population, with special reference to allometry of size

Abstract

Life history phenomena of the mayfly Leptophlebia cupida (Say) from a subarctic stream of Canada were found to be best interpreted by combining size-frequency distributions and developmental stage data. Autumn was a period of intense growth and uniform development; both growth and development were retarded but not completely stopped during the 6-month winter period; development accelerated rapidly after the spring breakup even though water temperatures were still near 0 °C. Total fecundity, average egg size, and total egg volume varied directly with the size of the female. Last instar nymphs and sub-imagos of a given length had about the same number and size of eggs, but imagos of the same length had larger eggs. Analysis of nymphal size allometry indicated that none of the investigated body parts of either sex was exhibiting isometric growth with that of total length. All female dimensions and some male dimensions deviated from simple size allometry when the nymphs were about 7 to 9 mm in total length; a hypothesis with biological implication is; offered, accounting for these deviations. Length–volume biomass regression showed the nymphs conforming closely to the cube law; similar regressions for other stream invertebrates are also presented.