CONSUMPTION AND APPARENT DRY-MATTER DIGESTIBILITY OF 6 INTERTIDAL MACROALGAE BY TURBO-SARMATICUS (MOLLUSCA, VETIGASTROPODA, TURBINIDAE)

Laboratory experiments on feeding of Turbo sarmaticus have shown that this gastropod mollusc is capable of consuming and digesting algae fro m the Rhodophyta (Gelidium pristoides and Corallina spp.), Chlorophyta (Ulva rigida and Codium extricatum) and Phaeophyta (Ecklonia radiata and Iyengaria stellata). The consumption rates of animals feeding on t hese different algae at 20 degrees C ranged from 1.45 to 9.5% body wei ght per day (juveniles) and 1.06 to 6.08% body weight per day (adults) . Juvenile T. sarmaticus had significantly (P < 0.05) higher consumpti on rates (1.6-2.8 times higher) for each algal species (except E. radi ata) than adults. In both juveniles and adults, consumption rates of t hree species of algae (G. pristoides, U. rigida and Corallina spp.) we re 1.5 to 5.8 times higher at 20 degrees C and 25 degrees C than at 15 degrees C. The apparent dry matter digestibility for the different al gae at 20 degrees C ranged from 9.1 to 74.8% (juveniles) and 7.3 to 77 .1% (adults). Juvenile T. sarmaticus had significantly (P < 0.01) high er apparent dry matt:er digestibility values (12-24% higher) for each algal species, except G. pristoides where there was no significant dif ference (P = 0.444). In both juvenile and adult T. sarmaticus, algal d igestibility was not affected by temperature. Monthly comparisons of t he energetic value and nutritional content (protein, soluble carbohydr ate and lipid) of the algae indicated that, with the exception of U. r igida and C. extricatum, there was little seasonal variation. (C) 1998 Published by Elsevier Science B.V. All rights reserved.