Prey preferences of juvenile whelk Neptunea arthritica (Gastropoda: Buccinidae) in Hakodate Bay, Hokkaido, Japan

抄録

Juvenile Japanese Neptune whelk Neptunea arthritica preys on small gastropods in the field. Although the most common prey is Homalopoma sangarense, its density is lower than those of other prey species (e.g., Barleeia angustata, Reticunassa fratercula, and Cantharidus japonicus) in the field. To clarify whether N. arthritica juveniles show an “actual” or “apparent” preference for H. sangarense, we conducted a single-prey feeding experiment. Although N. arthritica attacked H. sangarense earlier and more frequently than B. angustata and C. japonicus, there was no difference in attack frequency and latency between H. sangarense and R. fratercula. Attacks on H. sangarense failed more frequently than on the other species, and the handling time for H. sangarense was significantly longer compared to the other three species. The large difference in handling time (over 10-fold difference) could be caused by the presence of a thick calcareous operculum on H. sangarense. Eventually, N. arthritica consumed more individuals of R. fratercula than of H. sangarense in the experiment. These results indicate that N. arthritica juveniles exhibit both “actual” and “apparent” preferences for H. sangarense. The “actual preference” of N. arthritica juveniles may reflect the past species compositions of small gastropods, because H. sangarense has been previously reported as the dominant species at the study site.