GROWTH SURVIVAL AND FATTY ACID PROFILE OF HEDISTE DIVERSICOLOR (O.F.MULLER, 1776) FED ON SIX DIFFERENT DIETS
Fidalgo e Costa, P.1; Narciso, L.1 & Fonseca, C. da2
1 Laboratório Marítimo da Guia, Faculdade de Ciências da Universidade de Lisboa, Estrada do Guincho, 2750 Cascais, Portugal
2UCTRA - Universidade do ALgarve, Campos de Gambelas, 8000 Faro, Portugal
In order to investigate the effects of food quality on growth rate and survivorship of Hediste diversicolor, rearing experiments were undertaken over a period of 60 days. The principal objectives were to establish growth and survival rates experienced under various different diets so than an optimal diet could be determined. All trials were carried out using 1 month-old individuals at the commencement of the experiment. These were fed ad libidum, on alternate days, with one of six different types of food. The diets employed were: decapsulated Artemia cysts, sea bream dry food, Lansy (diet for late post larval stage of shrimp), Tetramin (fish dry food), extruded soy and pollen. The photoperiod was adjusted to long days (16L:8D) with an average light intensity of 175 Lux. Temperature and salinity were mantained constant at 20±2º C and 15ºC respectively. Three replicates were established for each treatment, with 6 individuals per replicate. Lansy appeared to be the food type which gave both the highest daily growth rate (13.94 mg/day) and survivorship (100%). Each type of food was analysed for organic content, caloric content and total lipid. The organic matter content of sediments was also analysed. There seemed to be no direct relationship between growth rates and the different diets. The fatty acid profile of juvenile worms reflects the fatty acid profile of the diet. Higher levels of dietary total lipids, DHA and EPA result in higher levels of these in the lipid profile of the juveniles. When the diet has high DHA/EPA ratios, however, the juveniles do not reflect this ratio. This seems to indicate that H. diversicolor does not require high levels of DHA. It appears, generally, that higher HUFA levels (mainly EPA and DHA) result in better growth rate and higher survivorship.