The burrowing bivalve Lithophaga curta is abundant (8 to 9 per 100 cm²) in the encrusting, hermatypic coral Montipora berryi at Enewetak; this is the first report of L. curta colonizing living coral. Conversely, larvae of M. berryi appear to settle in empty bivalve burrows, tentatively identified as those of L. curta, located in dead M. berryi. Several hypotheses are suggested on the adaptive significance of substrate selection by larvae of both species and an overall hypothesis of reciprocal recruitment, describing the dynamic aspects of this apparently co-evolved relationship, is proposed.