Effect of vitamin C and astaxanthin on stress and disease resistance of postlarval tiger shrimp, <i>Penaeus monodon</i> (Fabricius)

Postlarvae of tiger shrimp, Penaeus monodon (Fabricius), were fed semipurified diets supplemented with various levels of astaxanthin (AX) and ascorbic acid-polyphosphate (ApP): three groups were fed 230 mg AX kg-1 diet combined with 100, 1700 and 3400 mg ascorbic acid (AA) kg-1 diet, respectively; two diets contained 810 mg AX kg-1 mixed with 200 and 1700 mg AA kg-1, respectively. Each treatment was run in four replicates. Incorporated levels of AA and AX, production output, and physiological condition were recorded after 4 weeks feeding. Whole-body AA (21-47 µg-1) and AX concentrations (19-35 µg-1) were linked to dietary ApP and AX supply, respectively, although not significantly for the latter. The biomass of the group receiving the lower dietary ApP-AX combination was significantly lower than for all other treatments, i.e. 3.1 versus 3.9 g, respectively. In the groups fed 230 mg AX kg-1 diet, significant differences in stress resistance were observed according to the dietary ApP level, i.e. raising the vitamin C content in the feed from 100 to 3400 mg AA kg-1 resulted in a concomitant drop in mortality after an osmotic shock. For the treatments receiving 810 mg AX kg-1 diet, the beneficial effect of extra dietary vitamin C was not significant. An increase in the dietary AX for shrimp fed comparable ApP levels resulted in a significant drop of the stress index from 56 to 33 (cumulative mortality index). An increased resistance to salinity shock was demonstrated in association with supplementation of high dietary AA or AX levels. No conclusive results regarding possible improved disease resistance could be made since no mortality was observed after a disease challenge with Vibrio harveyi

Comportamento alimentar do camarão de agua doce, Macrobrachium rosenbergii (De Man) (Crustacea, Palaemonidae) durante a fase larval: análise qualitativa Feeding behavior of the prawn, Macrobrachium rosenberch (De Man) (Crustácea, Palaemonidae), during the larval phase: qualitative analysis

<abstract language="eng">Feeding behavior of the larvae's prawn, Macrobrachium rosenbergii De Man, 1879, in each stage of development was studied face alArtemia Linnaeus, 1758 nauplii, dry and wet diets. Groups of ten larvae in each stage were placed in 500 ml beakers at 29ºC in filtered brackish water. After the fasting period of acclimatization, the three types of food were offered separately to the larvae and the feeding behavior was observed during 30 min. Feeding perception, capture, grasp and ingestion of food were used to determine feeding pattern. Stage I lawac do not eat. The feeding behavior of larvae was similar on the stages II - XI. The perception in distance does not occur in most individuais; the feeding process generally started with the physrcal contact of food with the animal. Food is captured by thoracic appendages (maxillipeds until stage III, and maxillipeds + pereopods in stages IV - XI) and particles are grasped and handled by maxillipeds. Inopposition at the capture, the ingestion is a seletive process. Selective responses decrease in later stages and larvae become omnivorous in greater degree