Calumenin is a Ca(2+) binding protein localizing at the lumen of the endoplasmic reticulum (ER). Although it has been implicated in various diseases, the in vivo functions of calumenin are largely unknown. Here, we report that calumenin has pleiotropic roles in muscle and cuticle function in Caenorhabditis elegans. Mutant analysis revealed that the calu-1 is required for regulating fertility, locomotion and body size. In addition, calu-1 is important for two behaviors, defecation and pharyngeal pumping, consistent with its ability to bind Ca(2+). The genetic analysis further suggested the possibility that calu-1 regulates the pharyngeal pumping together with the inositol 1,4,5-triphosphate (IP(3)) receptor encoded by itr-1. Taken together, our data suggest that calumenin is important for calcium signaling pathways in C. elegans.