Table 1.

Average heart rate of st.34 medaka embryos measured at 26°C

	Hd-rR embryos
	Control	Incubated at 15°C
Heart rate (bpm; mean ± SD)	116.0 ± 10.6	117.5 ± 1.82

Average heart rate (bpm; measured at 26°C) at st.34 after incubation of the embryos at 15°C from st.18 onwards (“Incubated at 15°C”, n = 26) in the Hd-rR. All embryos incubated at 15°C showed blood regurgitation. Control embryos were incubated at 26°C and did not exhibit blood regurgitation (n = 27).