||Water temperature, photoperiod and feed β-carotene level were the three factors in a four months lasted factorial experiment to investigate the growth and gonad development of the urchin. The interaction between the two factors, water temperature and photoperiod, were significantly influencing the growth and gonad formation of the urchin investigated. Body growth rate of the urchin exhibited better growth rate cultured at 25℃ than those at 29℃. Low water temperature (25℃) had been found to elevate the urchin body growth rate within each of the three different photoperiod treatments. Interaction between water temperature and photoperiod was observed by the differences in the enhancement of body growth rate from short photoperiod (10L14D) the most followed by the mid photoperiod group (12L12D) and the least enhanced the long photoperiod group (14L10D). Gonad somatic index within short photoperiod group was increased over 9% for those urchin cultured at low temperature than those at high temperature. Feed β-carotene was an independent factor which neither interacted against of temperature factor nor the factor of photoperiod on body growth rate and gonad color enhancement. However increased the level of β-carotene in feed had no effect on the improvement of GSI value.
The larval settlement experiment of the sea urchin Tripneustes gratilla had been conducted four times from March through October 2006. None of the larvae induced by various levels of MGDG and DGDG were able to settle on the surface of the Petri-dish used in the experiment. Only very few larval grew out spines during the metamorphosis stage.
It was concluded that a 60 ppm of β-carotene level cultured at 25℃ with a short photoperiod (10L14D) may speed up both the body growth rate and gonad deposit rate of the Tripneustes gratilla.