Feeding rhythms of the green-lipped mussel, Perna viridis (Linnaeus, 1758)(Bivalvia : Mytilidae) during spring and neap tidal cycles

Food availability and feeding responses of the green mussel Perna viridis w ere investigated for two complete tidal cycles during both spring and neap tides. Temporal changes in total particulate matter (TPM), particulate inor ganic matter (PIM) and particulate organic matter (POM), were smaller durin g neap than spring tides. Seston characteristics at different times of a ti dal cycle were compared for both spring and neap tides. Only during spring tides were TPM and PIM significantly higher at high tides while POM remaine d relatively constant (P>0.05). The clearance rate of the mussels underwent temporal variations with tides, and was a negative power function of TPM a nd a positive linear function off (organic content), during both spring and neap tides. f was the key factor influencing filtration rate, organic inge stion rate, absorption rate and absorption efficiency. Ail feeding rates in creased linearly with increases in organic content. Pseudofaeces were produ ced only during spring but not neap tides. Feeding rates and absorption eff iciency were highest at low and lowest at high tides (P<0.01). There was no significant temporal change in the wet weight and protein content of the c rystalline style with the tidal regime. For the digestive gland, ol-amylase activity was higher at spring than at neap tides, and higher during high t ides in a tidal cycle. The digestive gland cellulase activity did not chang e significantly with the tides. For the crystalline style, both the activit y of cellulase and a-amylase were not significantly different (P>0.05) betw een spring and neap tides. Tidal rhythms in feeding and digestion in this s pecies were likely controlled by temporal variations in food availability i n the seawater. By adjusting feeding rates and enzymatic activities, absorp tion in Perna viridis remained constant, irrespective of the changes in foo d availability. (C) 2001 Elsevier Science B.V. All rights reserved.