A small subset of eggs were removed from a bell jar, placed on ice and staged according to Price (1934a, 1934b, 1935)and Sreetharan et al. (2015) under a Zeiss AXIO Zoom V16 microscope(Carl Zeiss AG; Oberkochen, Germany). When embryos had reached the target stages, approximately 1000 eggs or 500 hatchlings were selected from four bell jars and transferred to ten 15 ml tubes (each tube contained embryos from a single bell jar) and snap frozen in liquid nitrogen. The frozen samples were then stored at −80 °C until lipid extraction. Due to a malfunctioning incubator, when 2 °C embryos reached constant fin flutter, incubation temperature was changed to 3.9 ± 0.3 °C until hatching. This resulted in an average incubation temperature throughout development of 3.3 ± 0.2 °C, and thus we refer to hatchlings from this group as being incubated at 3.3 °C throughout the manuscript.