Davison J
Science. 1976 Nov 5;194(4265):618-20. doi: 10.1126/science.982029.
Hydra hymanae, a hermaphroditic freshwater coelenterate, reproduces asexually at 24 degrees C and sexually at 15 degrees C. The appearance of gonads begins 12 days after transfer from 24 degrees to 15 degrees C and is complete 35 days after the temperature transition. Testes appear before eggs. Fifty percent of the mature embryos maintained at 15 degrees C hatch by day 61, but they have a low level of survival. Fifty percent of the mature embryos pretreated for from 5 to 25 days at 4 degrees C hatch by about day 45, and these have a high level of survival. Embryos maintained at 4 degrees C for longer periods (55 to 85 days) accumulate in a prehatching state and hatch with a high degree of synchrony approximately 7.5 days after return to 15 degrees C. Populations derived from newly hatched polyps are refractory to sex induction for approximately 120 days. The system is well adapted to ensure a regular alternation of reproductive modes in the natural environment.
海德拉·希马内（Hydra hymanae）是一种雌雄同体的淡水腔肠动物，在24摄氏度时进行无性繁殖，在15摄氏度时进行有性繁殖。从24摄氏度转移到15摄氏度后12天开始出现性腺，温度转变后35天性腺发育完全。精巢比卵巢先出现。在15摄氏度下培养的成熟胚胎，到第61天时有50%孵化，但存活率较低。在4摄氏度下预处理5至25天的成熟胚胎，大约在第45天孵化，且存活率较高。在4摄氏度下培养较长时间（55至85天）的胚胎会积累在孵化前状态，回到15摄氏度后约7.5天高度同步地孵化。新孵化的水螅群体产生的后代在大约120天内对性诱导不敏感。该系统非常适合确保在自然环境中生殖模式有规律地交替。
