THE THERMAL ECOLOGY OF NERITIDAE ON TROPICAL SEAWALLS

Abstract

Temperature has wide-ranging effects on the physiology and behaviour of ectotherms, especially slow-moving intertidal snails. While tropical species experience greater temperature-related mortality risk than temperate ones, thermal research in the tropics remains limited. With increasing coastal urbanization intersecting with climate warming, it is crucial to examine how the novel thermal landscapes of seawalls dominating Singapore’s shores impact the nerite snails (Nerita spp.) that are abundant on them. Here, I (i) tested self-constructed biomimetic temperature loggers (“Robonerites”) designed to measure nerite body temperatures, (ii) investigated nerite thermal tolerance using heartrate as a response in temperature ramping assays and (iii) examined nerite thermal preference on a specially-fabricated thermal gradient plate. My findings demonstrated Robonerites to be reliable at providing realistic nerite body temperatures and indicated that nerites could withstand current temperature conditions on Singapore’s seawalls. They also generally preferred higher temperatures than non-tropical intertidal gastropods but move to lower temperatures if the opportunity arises. However, a warming climate still poses the potential risk of mortality. Interestingly, nerites from different seawalls had different thermal tolerances but not thermal preferences, suggesting an interplay of microclimatic and behavioural factors in their thermal ecology.