Thermal perception is crucial for the fitness of marine invertebrates in intertidal and shallow waters. TRPA1 is a non-selective cation channel that belongs to the TRP family with pivotal roles in initiating signal transduction of thermal perception. We investigated expression patterns of SiTRPA1 in different tissues (tube feet, coelomocytes, gonads and gut) of the sea urchin Strongylocentrotus intermedius. SiTRPA1 expression patterns under acute and long-term temperature stimuli were investigated in tube feet of sea urchins. In the present study, the highest expression of SiTRPA1 was detected in tube feet of S. intermedius. The SiTRPA1 expression level in tube feet were significantly 235.7-fold, 450.0-fold and 3299.7-fold higher than those in the coelomocytes, gonads and gut (df = 3, F = 47.382, P < 0.001). Expression levels of SiTRPA1 in the other tissues (coelomocytes, gonads and gut) were not significantly different (df = 3, F = 47.382, P = 0.972). There was no significant difference of SiTRPA1 expression among all groups in the acute temperature increase experiment (df = 4, F = 0.25, P = 0.902). In the acute temperature decrease experiment, the expression of SiTRPA1 showed no significant difference among all groups (df = 4, F = 1.802, P = 0.205). With long-term exposure (6 weeks) to different temperatures, SiTRPA1 expression in the low temperature group (10°C) was significantly higher than those in the high temperature (20°C) and the control groups (15°C) (df = 2, F = 9.57, P = 0.014). There was no significant difference of SiTRPA1 expression between the high temperature (20°C) and the control temperature (15°C) groups (df = 2, F = 9.57, P = 0.808). These results indicate that SiTRPA1 expression significantly responds to long-term low temperature but not to acute temperature decrease. The present study provides new insights on the distribution and temporal expression of TRPA1 in marine invertebrates after acute and long-term temperature stimuli.

Feeding regime is an important concern for sea urchin aquaculture. However, optimal feed regimes have not been established for land-based sea urchin ventures using a formulated feed. In this study, we investigated the effects of short-term continuous and intermittent feeding regimes on food consumption, growth, gonad production and quality of the sea urchin Strongylocentrotus intermedius (54.90 ± 2.28 mm of test diameter) fed a formulated feed. The results showed that (1) compared with initial conditions, all involved traits except a* (test diameter, test height, body weight, gonad weight, gonad index, gonad moisture, L* and b*) showed significant increase at the end of the experiments; (2) only the longest term feed regime tested in this trial (S2) significantly negatively affected growth and gonad production of S. intermedius fed a formulated feed; (3) there was a trend but this was not significant for inhibiting gonad development of S. intermedius in intermittent feeding regimes and there was no change in the gonad colour and sweetness; (4) S0.5 (fasting half day and then feeding half day) is the optimal intermittent feeding regime for S. intermedius fed a formulated feed. To our knowledge, the present study is the first report of finding an effective intermittent feeding regime for land-based cultured sea urchins of relatively large size, and thus has direct application potential in the field of aquaculture.

Water temperature is one of the most important factors greatly affecting the aquaculture of sea urchins. However, no information is available on how to improve commercial traits of sea urchins reared at high water temperature. Here, we investigated the effects of water temperature and feeding regime on food consumption, growth, gonad production, gametogenesis and gonad quality of the sea urchin Strongylocentrotus intermedius. We found that high water temperature (22°C) significantly decreased dried food consumption and gonad production of S. intermedius, but not the somatic growth. The feeding regime of formulated feed and kelp has direct application potential in S. intermedius aquaculture, especially at field temperature. Feeding kelp alone is not effective in supporting growth and gonad production for S. intermedius cultured at high water temperature. This finding greatly challenges the current commonly used feeding regime (feeding macroalgae only) for S. intermedius cultured at high water temperature. Based on the current results, we suggest the feeding regimes of formulated feed and kelp or formulated feed alone for S. intermedius aquaculture at high water temperature. The present study provides new information for aquaculture of S. intermedius at high temperature and for production out of season.

In the field, both covering materials and shelters are commonly available to sea urchins. The behavioural decision between covering and sheltering thus obviously exists. However, no information is available on the preference between the two natural behaviours. Two conditions were designed with covering and sheltering materials to comparatively describe the diel trade-off between covering and sheltering behaviours in male and female Strongylocentrotus intermedius. In the present study S. intermedius had an obvious diel trade-off between covering and sheltering behaviours, preferring covering over sheltering when both behaviours were possible. Sex did not significantly affect the trade-off between the two behaviours, no matter whether covering materials were inside or outside the shelters. The rhythm of covering behaviour was not well correlated with intensity of light in the trade-off with sheltering behaviour. The present study provides new insights into behavioural ecology of sea urchins.