Energetics of the chiton Sypharochiton pelliserpentis from a sheltered shore at Kaikoura
Degree GrantorUniversity of Canterbury
Degree NameMaster of Science
Energy budgets are reported for high- and low-shore groups of the chiton Sypharochiton pelliserpentis from a sheltered shore, Kaikoura Peninsula. All components of the budget were measured; i.e., growth production (Pg), mucous g production (Pm), reproductive production (Pr), respiration (R), defaecation (F), excretion (U) and consumption (Cm). Previous molluscan energetics studies have usually ignored Pm and U, and calculated consumption by summing all other M terms. The largest single component of the budgets of both groups was mucous production which accounted for about 72% of assimilated energy, whereas respiration (generally assumed to be the largest component of energy expenditure by animals) accounted for only about 23% of assimilation. This finding shows the importance of mucous production in molluscan energetics. Assimilation efficiencies of both chiton groups (89 and 93%) are higher than those reported generally for other molluscs. Differences between the budgets occurred in faecal production and reproductive effort. High-shore chitons defaecated only 7% of their ingested energy, compared with 11% egestion by low-shore chitons. High-shore chitons expended 4.2% of their assimilated energy (excluding Pm) on M reproduction, whereas low-shore chitons expended only 2.6%. High-shore chitons exhibited some adaptations enabling them to maintain consumption in the face of reduced available feeding time, and reduce metabolic costs in the face of exposure to higher environmental temperatures. Annual energy flow through the high-shore group (509 kJ m-²) was only about a third of the low-shore flow (1375 kJ m-²). Measured consumption (Cm) on the high shore was 8% lower than the m estimate of consumption obtained by summing all other components (Cs), whereas on the low shore, Cm was 9.6% higher. The small differences between Cm and Cs for both groups m suggest that the reported budgets are accurate representations of energy flow through the groups. The inclusion of mucous production in the budgets for S. pelliserpentis is the main cause of differences between these budgets and budgets reported for other herbivorous gastropods.