KENNEDY ET .-XL.: TEMPER.ATURE-TIME REL.^TIONSHIPS 



Table 1. — Percentage mortality of cleavage stages of Mercenaria mercenaria under different temj>erature-time combinations. 

 Values in parentheses are temperatures corrected for the influence of injection water. 



Table 3. — Percentage mortality of straight-hinge larvae of Mercenaria mercenaria under different temperature-time combinations. 

 Values in parentheses are temperatures corrected for the influence of injection water. 



in most of the vials containing the cleavage stages 

 and trochophores was found to have developed a 

 precipitate that hindered microscopic analysis of 

 the results. Consequently, in March 1973 we 

 spawned 2-yr-old individuals of the Fo generation 

 produced in the hatchery in 1971 from the same 

 local wild stock. These clams had been held in 

 beds near the hatchery. They were conditioned for 

 6 wk in warm water before being spawned (Loo- 

 sanoff and Davis, 1963) and provided us with re- 

 placement cleavage stages and trochophore 

 larvae. Results of experiments using these re- 

 placements did not appear to differ from prelimi- 

 nary results of the 1972 experiments. 



Embryos and larvae not used immediately in 

 experiments were held at ambient temperatures 

 in 60-liter plastic containers at a density of about 

 33/ml (cleavage stages, trochophores) or about 

 17/ml (straight-hinge) with the seawater changed 

 daily. Development appeared normal with no high 

 mortalities observed. Larvae not used in our 

 experiments were successfully carried through to 

 metamorphosis. 



We used clarified, ultraviolet irradiated sea- 

 water (28-31"/oo) in the experiments. The cast 

 aluminum block, bored to hold 88 test tubes 

 (25 mm) in an 8 )( 11 matrix (see Figure 1, 

 Kennedy et al., 1974) provided a thermal gradient 



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