. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ANTARCTIC ECHINODERM DEVELOPMENT 47 20 15 - o £:• i 10 -2-10123 Temperature (°C) Figure 2. The number of nonviable eggs and embryos in each cul- ture at each temperature step. Oclonmsler incriilionalis (•) was htted by hnear regression (v = : -I- 11T5, r = ). as was O. valulus (O) (v = + r = ). Sterechimis neuimiyeri (A) data were titled with a broken stick model by the likelihood method (94% of variance accounted for). lated and fitted to the two data sets by analysis of covaii- ance. Th
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ANTARCTIC ECHINODERM DEVELOPMENT 47 20 15 - o £:• i 10 -2-10123 Temperature (°C) Figure 2. The number of nonviable eggs and embryos in each cul- ture at each temperature step. Oclonmsler incriilionalis (•) was htted by hnear regression (v = : -I- 11T5, r = ). as was O. valulus (O) (v = + r = ). Sterechimis neuimiyeri (A) data were titled with a broken stick model by the likelihood method (94% of variance accounted for). lated and fitted to the two data sets by analysis of covaii- ance. The resulting intercepts were significantly different (difference = , / = , P < ). indicat- ing that O. validus embryos were, on average, developing at a rate times faster than O. meridioiudis. A broken stick model was fitted to the data for the development rate of 5. neiimayeri (Fig. 3); the fit ac- counted for 98% of the variance. Maximum likelihood showed that the break point occurred at °C. Below this temperature, development rate increased rapidly with temperature (v = r = ). but above it development rate did not alter significantly with tempera- ture (V = , r = ). Q,„ values The Qw coefficient is a measure of the change in rate of a process with temperature (Cossins and Bowler, 1987). It is expressed as the factorial rate change over a 10°C temper- ature step and was originally devised for biochemical sys- tems. It is useful here for comparing development rates between species and emphasising differences between rates. In physiological systems, g,,, values are usually between 2 and 3 (Clarke. 1983), and a C?ii) of 1 indicates no change with temperature. Although the temperature range here is development rates to the blastula stage for S. neumuyeri. and results indicated that embryos took just over 40 h to reach this stage. Clearly, very small differences in devel- opment rate could have gone undet
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