Effects of algal diet on larval survival and growth of the barnacle Amphibalanus (=Balanus) improvisus

The effects of algal diet on larval survival and growth of the barnacle Amphibalanus improvisus was for the First time examined under controlled laboratory conditions. Larvae were obtained by dissecting egg lamellae at later developmental stage out of the adults. Hatched nauplii were reared in 0.6-1 glass beakers (200 larvae I(-1)) on a monoalgal diet of Chaeloceros calciltrans, Chlorella vulgaris and Scenedesmus quadricauda at I X 105 and 2 x 105 cells ml(-1), under continuous light at 25 +/- 1 degrees C. The rate of development, survival and size (at Stage V of the larvae were measured for each diet. The majority of nauplius 11 larvae (similar to 70%) fed with Cha. calcitrans and Oil. vulgaris developed into cyprids within seven days while those fed with S. quadricauda remained at Stage II. A shorter time interval for Stage II to III was observed in larvae fed with a Chl. vulgaris monoalgal diet than Cha. calcitrans. Larvae fed with Cha. calcitrans had shorter developmental intervals for later larval stages (Stages IV-VI). The highest mortality was observed in the treatment with a monoalgal diet of S. quadricauda, while the highest survival was achieved with a diet of Cha. calcitrans. The mixed diet of Cha. calcitrans, Chl. vulgaris and S. quadricauda resulted in a shorter developmental duration of larval cycle (six days). Both food type and food concentration significantly affected the length and width of the nauplius larvae.