The growth rates of Aplysia punctata Cuvier feeding on eight species of marine algae were found to decrease in the order: Plocamium > Enteromorpha > Ulva > Heterosiphonia > Cryptopleura > Delesseria > Laminaria. The brown alga, Desmarestia aculeata, was not eaten. Except for Enteromorpha and Desmarestia, this was also the order found for the feeding preference of sublittoral Aplysia. Enteromorpha was eaten by Aplysia in preference to all the other algae studied.
No clearly defined trends in the concentrations of ash, protein, fat and carbohydrate in the seaweeds were found to account for these differences in growth rates. Absorption of total dry food matter was lowest from the algae giving the poorest growth (45 and 53%, respectively, of the total dry weight consumed for Delesseria and Laminaria diets) and highest from the seaweeds giving moderate growth (71–75% for Ulva, Heterosiphonia and Cryptopleura diets). For Plocamium and Enteromorpha diets the values were 59 and 65%, respectively. Carbohydrate materials were found to constitute 42–75% of the total dry weight of food material absorbed by Aplysia on all the algal diets, and represented the major portion of each. The efficiency of conversion of absorbed food matter into tissues was highest on the algae giving the poorest over-all growth (73% for Delesseria and 40% for Laminaria). For the other seaweed diets the efficiencies decreased in direct relation to the decrease in the value of each for growth of Aplysia (from 35% for Plocamium to 15 % for Cryptopleura).
The same amino acids were found in each food.