An analysis of the shell microstructure of A. granosa and P. viridis experimentally cultured in coastal waters of Thailand revealed that the formation of growth lines was closely related to tidal periodicity. This study concludes that growth lines are formed when the bivalves react with shell closure to reduced water flow, the degree of sensitivity being species-specific. However, the application of this methodology to tropical bivalves is not recommended given the rather demanding preparative work and the large degree of uncertainty involved in the interpretation of observed growth lines. Fitting of growth data from the culture experiments to the von Bertalanffy growth function (VBGF) showed large variations of the single growth parameters but little variance in the resulting growth index (the phi prime concept) supporting the perception of phi prime being a species-specific parameter. This concept was further investigated by computing the phi prime index from growth parameters of 190 bivalve stocks compiled or computed from the literature. It was shown that phi prime is usually narrowly distributed around a species-specific mean. Use of the phi prime concept for growth comparison between different genera is generally limited because of the different shell shape, which strongly influences the phi prime. However, mytilids, with their relative uniform shell shape, displayed a linear increase of the phi prime with environmental water temperature, suggesting that bivalves tend to grow larger in warm waters. This is in contrast to general observations in fish, and is explained by the difference in energy demand for the precipitation of calcium carbonate from seawater.