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We report the results of controlled feeding trials on the tiger shrimp, Penaeus monodon (Fabricius). The desired colour was obtained by feeding a diet supplemented with astaxanthin (50 p.p.m) for 7± 8 weeks before harvest. Similar coloration was achieved, however, by including in the feed an algal material (Dunaliella salina) that contains bcarotene but no astaxanthin. Feed containing bcarotene at 125 p.p.m also gave the required coloration at 7±8 weeks, whereas the same results was obtained after only 5±6 weeks when feed containing 175 p.p.m b-carotene was used. Irrespective of whether the shrimp were fed astaxanthin or b-carotene, the main carotenoid accumulation was astaxanthin, in free and esteri®ed form, showing that P. monodon has the metabolic ability to convert b-carotene into astaxanthin. The supplementation with b-carotene or astaxanthin had no signi®cant effect on growth, average ®nal weight, survival rate or feed conversion ratio, nor on the immune response of the shrimp in terms of production of haemocytes phenoloxidase in the cytoplasmic granules of the haemocytes, microbial clearance ability and resistance to infectious diseases. This is a highly signi®cant development for commercial aquaculture, because it shows that supplementing diets with b-carotene can achieve the same result as doing so with much more expensive astaxanthin.

A¯atoxin B 1 was studied in juvenile black tiger shrimp (Penaeus monodon Fabricius) (1±2 g) to see the effects on growth performance and histopathology, and in adult shrimp (10±12 g) to study the effects on immuno-physiological function, histopathology and a¯atoxin residue. Feeds supplemented with 0, 50, 100, 500, 1000 and 2500 p.p.b. a¯atoxin B 1 were given to test groups for an 8-week period. A¯atoxin B 1 in the diet showed highly negative correlation to average weight, weight gain and survival (r = ± 0.99, ±0.96 and ±0.95 at P < 0.05, respectively)