EFFECTS OF THE STIPE-BORING AMPHIPOD PERAMPHITHOE STYPOTRUPETES (COROPHIOIDEA: AMPITHOIDAE) AND GRAZING GASTROPODS ON THE KELP LAMINARIA SETCHELLII

The ampithoid amphipod Peramphithoe stypotrupetes hollows and infests the stipes of the alga Laminaria setchellii after intense grazing of its lamina by gastropods. The intensity of gastropod grazing and subsequent levels of amphipod infestation appear to be correlated with calm ocean conditions. Once established in the stipe, a pair of adult amphipods produces multiple cohorts of offspring, which hollow and kill the plant. At a study site off northern California, an entire bed of the alga was infested and no plants survived. Aspects of the natural history of P. stypotrupetes are discussed.