AGING THE EUROPEAN LOBSTER HOMARUS-GAMMARUS BY THE LIPOFUSCIN IN ITS EYESTALK GANGLIA

In this study, lipofuscin was examined in the eyestalk ganglia of tagg ed European lobsters Homarus gammarus released into the wild at Scapa Flow, Orkney, Scotland, at approximately 3 mo of age and recaptured at ages between 5.4 and 9.6 yr. Lipofuscin deposits were often most abun dant in cell cluster A of the medulla terminalis (MT-A), where they ex hibited typical autofluorescence, histochemical, distributional and st ructural properties. Confocal fluorescence microscopy and image analys is were used to quantify the deposits. The study demonstrated that lip ofuscin accumulation in the MT-A is age-dependent (r = 0.640, p = 0.00 02). For the available sample range, no other statistically significan t relationships were found (carapace length vs age: r = 0.147, p = 0.3 59; body weight vs age: r = -0.054, p = 0.738; carapace length vs lipo fuscin concentration: r = 0.331, p = 0.0849; body weight vs lipofuscin concentration: r = 0.181, p = 0.358). Body size had no age discrimina ting power. There was no difference in lipofuscin accumulation rate be tween males and females. When placed in perspective against the highes t lipofuscin concentrations so far measured for wild individuals of th is species, it was apparent that the available sample of tagged lobste rs, spanning an age interval of about 4 yr, represented only a very sm all window of the total lifespan. The results indicate that measuremen t of MT-A lipofuscin concentration will provide considerably more accu rate age determination of fished lobsters than the current body-size-b ased approach. MT-A lipofuscin concentration correctly ages approximat ely 43% of lobsters in a sample to within 1 yr or less of their true a ge, and 95% of lobsters to within 3.5 yr. Carapace length correctly ag es only 3% of individuals correctly to within 1 yr. The width of the 9 5% confidence intervals for carapace-length-based age estimates are so large as to render these estimates meaningless. Size-at-age and numbe r-at-age data obtained using lipofuscin will prove useful for estimati ng growth and mortality in wild lobster populations and provide insigh t into potential biases in the current, conventionally derived estimat es of these parameters. From a practical perspective, it is easier to sample nerve tissue containing lipofuscin from the eyestalk than the b rain and has the advantage of leaving the lobsters in marketable condi tion.