Effects of starvation on the physiology and foraging behaviour of two subtidal nassariid scavengers

The present study investigated the effects of starvation on the foraging behaviour and physiology of two subtidal nassariids Nassarius conoidalis and Nassarius siquijorensis, which play an important ecological role in removing a large number of dead animals on the local sea bed. In both nassariid species, 8, 16 and 32 days of starvation significantly reduced the respiration and ammonia excretion rates and Scope For Growth (SFG) compared with their well-fed counterparts; the respiration and ammonia excretion rates of the starved groups decreased with increasing starvation periods. Under well-fed conditions, SFG of N. siquijorensis was higher than that of N. conoidalis. In contrast, the SFG was more negative for N. siquijorensis than N. conoidalis when starved. This study also showed that the percentage of numbers of both nassarrid species that arrived at bait was affected by both distance from the bait and starvation, but not their interaction. A shorter distance and starvation increased the percentage of numbers of arrivals. A speed ranging from ~ 1 to 3 cm min^− 1 was recorded for N. conoidalis and N. siquijorensis locomotion toward food. Furthermore, the majority of the starved nassariids moved toward food at a speed of ~ 0.18 to 1.30 cm min^− 1 higher than their well-fed counterparts. The differential responses of the two gastropods to food availability may provide insight into the dominance of N. siquijorensis in Hong Kong waters.