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MEMOIRS OF THE QUEENSLAND MUSEUM 285 SENESCENCE, FLUORESCENCE AND to place only 51% of the experimental individuals into their CRUSTACEAN AGE DETERMINATION correct age class, lipofuscin volume fraction correctly placed Assessment of the age of individuals is currently a signif- 93% of the same. individuals. Lipofuscin volume fractions scant problem in studies of crustacean population dynamics, were similar in the olfactory lobes of crayfish of similar specifically the management of commercially important chronological age despite a wide disparity in bady size and crustacean stocks, which are coming under increasing threat weight, of over exploitation, Several methods have been tried for assessing age in Discussion crustaceans, butall are severely restricted. The most widely The present results suggest that lipofuscin has significant used method, that involving prediction of age trom body size, potential as an index of crustacean age. Although lipofuscin based on growth rates determined from modal analysis, tag accumulates with physiological age, rather than strict recapture programs or laboratory rearing, suffers a fun- chronological age, and its accumulation is affected by en- damental problem9 4 variability of growth raie between vironmental paramoters such as temperature (Sheehy, individuals, Individuaolft sh e sume chronological age, Brow- 1990b), growth is also influenced by environmental factors. ing in the same environmental regime, may sometimes differ At this slage, there is no reason to believe thal lipotuscin in their size by an order of magnitude. This phenomenon would nol be a superior predictor of age 10 body size under clearly limits the usefulness of body size as an indicator of variable field conditions. Early results suggest that it may be age. The wide application of this method of age prediction possible to predict absolute chronological age of field ani- reflects the need for, but lack of, a suitable alternative. Thus, mals. using relatively simple luboratory established models new approaches to crustacean age determination are essen- incorporating ambien! lemperature (Sheehy, 1990b), lial. Ettershank (1983) attempted to use the inlensily of extracted chloroform-soluble fluorescence to age field-cap- Literature Cited tured Antarctic krill, Euphausia superba. Similar extractable Eltershank, G. 1983, Age structure and cyclical annual size fluorescence had been shown to accumulate linearly with age change in the Antarctic krill, Euphausja superbu Dana. in insects and was thought to be derived from the universally Polir Biology 2: 189-193. occurring lipotuscin age-pizment. Nicol, 8, }987, Some limitations on the use of the lipofuscin Subsequently however, work by the presen! author and upoing technique. Marine Biology 93: 609-614. athers (Nicol, 1987; Sheehy and Ettershank, 1989; Sheehy Sheehy, M.R.J. 1989. Crustacean brain lipofuscin: an exami- and Roberts, in press),.some of which was on crustaceans of nation of the morphological pigment in the freshwater known age, revealed some serious flaws in the methods used crayfish Cherax cuspidarus (Crustacea: Parastacidae), by Ettershank and previous workers, Most importantly, 8lipo- Joumal of Crustacean Biology 9(3): 387-391, fuscin-like9 extractable Muorescence did not appear to bo 1990a, The widespread occurrence of fluorescent morpho- derived from lipofuscin und ils inlensily bure little relation- logical lipofuscin im the crustacean brain, Journal of ship to age. Recently, prominent workers in the broader field Crustacean Biology 14): 615-622. of gerontology have been voicing serious doubts about the 1990b. Individual variation in. and the effect of rearing hiochemical extraction method for lipofuscin determination temperature and body size on, the concentration of (Sohal, 1987). fluorescent morphological lipofuscin in the brains of Clearly, the polential of lipofuscin as am index of age in freshwater crayfish, Cherax cuspicatus (Crustacea; Par- crustaceans required reassessment. astacidae). Comparative Biochemistry and Physiology Methods and Results 9M A): 281-286. Flvorescent morphologies! lipofuscin was identified in Shechy, M,R.J, and Bttershank, G. 1989. Solventextractable, histological sections from a wide range of crustaceans, in- age pigmentlike autofluorescence and its relationship to cluding several of economic imporlance (Sheehy, 1989, growth and age in the waterflea Daphnia carinata King. 1990a). Alternative quantification techniques were Australian Journal of Zoology 36; 611-625, developed, Using fluorescence microscopy and new image Shechy, M,R.J, and Roberis, B. tn Press, An alternative analysis methods (Sheehy, 1989, 1990b). conclusive evi- explanation for discrepancies in lipofuscin fluorescence dence of the physiological age dependence of lipofuscin data from insects, crustaceans and other aquatic species. accumulation in the Crustacea was obiained for the first time. Experimental Gerontology. in laboratory reared freshwater crayfish, Cherax quadricari- 8Sohal, R.S, 1987. Quantification of lipofuscin: a critique of natus, of precisely known chronological age, lipofuscin the current methodology. Advances in the Biusciences quantities in the base of the olfactory lobe cell mass of the 64. SS49L. brain were superior predictors of chronological age (r= 0,96) to morphometric parameters, such as carapace length, nor- MRS. Sheehy, Zoology Department, University of mally used for this purpose. While carapace length was able Ouweensland, St Lucia, Queensland 4072, Australia.