Fig. 3. Phospholipid to sterol ratios (mean ± s.e.m.) for two varieties of juvenile hard clams, wild Mercenaria mercenaria (circles) and selectively bred M. mercenaria var. notata (squares), as a function of time. Clams were placed in the field in August 2003 at two tidal locations and overwintered subtidally and in the laboratory between October 2003 and May 2004. Sampling took place in the field until October (filled symbols) and then in the laboratory until May (open symbols). Clams were sampled simultaneously in the field and in the laboratory in May to validate agreement between field and laboratory results. The first time at which a significant increase occurred is indicated by a single asterisk; double asterisks indicate the time at which the value returned to the initial level.