ESTIMATING AGE AND GROWTH IN LONG-LIVED TEMPERATE FRESH-WATER CRAYFISH USING LIPOFUSCIN

1. In ecological studies on freshwater crayfish, determination of basi c population parameters is often complicated by the lack of a suitable age estimation method. 2. Previously, lipofuscin age pigment in the o lfactory lobe cell masses (OLCM) of short-lived tropical crayfish has been used for accurate age determination. Here we present the first te st of this method on a longer-lived, temperate species, the signal cra yfish, Pacifastacus leniusculus. 3. Confocal fluorescence microscopy a nd image analysis of histological sections were used to quantify OLCM lipofuscin in a reference sample of Swedish P, leniusculus from severa l known year-classes, reared under naturally variable temperature cond itions. Lipofuscin concentration was linearly associated with age (r(2 ) = 92.4%) and produced much more accurate age estimates than conventi onal body size-based procedures. 4. A model derived from the crayfish of known-age was used to estimate the ages of wild P. leniusculus from an English stream. The relationship between lipofuscin-estimated age and carapace length suggested relatively slow growth in this wild popu lation, consistent with a high population density and severe competiti on. The analysis also extended the known longevity of P, leniusculus t o approximately 16 years. 5. The lipofuscin method for determining age and growth may be widely applicable to freshwater crayfish with proba ble further potential both within and outside the Crustacea.