Interactive effects of temperature and salinity on early life stages of the sea urchin Heliocidaris crassispina
Marine organisms are currently challenged by multiple and interactive environmental stressors. In the subtropics, warming and intensified precipitation, and hence, reduced salinity, are particularly relevant. Using the sea urchin, Heliocidaris crassispina, we investigated the effects of warming and low salinity on fertilization success and early development. These planktonic developmental stages play significant roles in shaping population dynamics. Gametes were exposed to a temperature gradient (28–43 °C) while being held at two salinities (24 and 32). Fertilization had a higher critical temperature (LT50), the temperature at which 50% individuals reached the designated stage, of 39 °C than that of blastula formation at 31 °C for both salinities, suggesting between-stage variations in sensitivity. The LT50 for blastula formation was very close to present-day recorded maximum sea surface temperature of 31 °C suggesting a small thermal safety factor. Larvae were also reared to the eight-arm stage in one of the four combinations of temperatures (24 and 28 °C) and salinities (24 and 32), which correspond to sea surface temperatures and salinities observed during the urchin’s spawning season. Low salinity and high temperature had interactive effects in reducing larval survivorship. However, amongst larvae that survived the combined stress, warming reduced the negative impact of reduced salinity on arm growth. Unexpected release of blastula-like particles was documented in all treatments except the control (24 °C and salinity 32). Incomplete separations that resulted in conjoined twins, however, were only found at 28 °C. There were significantly different responses in fertilization success and larval growth between maternal lineages. Such intra-specific variations highlight the presence of phenotypic plasticity and could imply the presence of genetic variations in response to thermal and salinity stress. Such plasticity suggests that although purple urchins are experiencing extreme conditions that are stressful at present, they may be able to cope with the future ocean conditions.
We thank the reviewers for their inputs, Y. K. Tam and L. W. Pang for their technical assistance during this study, C. Yau, N. Dorey and J. Ngo for their input on the manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interests.
All applicable international, national, and/or institutional guidelines for the care and use of animals were followed.
- Chiu S (1985) Feeding biology of the short-spined sea urchin Anthocidaris crassispina. In: Agassiz A (ed) Hong Kong proceedings of the fifth international echinoderm conference Balkema, Boston, pp 223–232Google Scholar
- Ding J, Chang Y, Wang C, Cao X (2007) Evaluation of the growth and heterosis of hybrids among three commercially important sea urchins in China: Strongylocentrotus nudus, S. intermedius and Anthocidaris crassispina. Aquaculture 272:273–280. https://doi.org/10.1016/j.aquaculture.2007.07.231 CrossRefGoogle Scholar
- Foo SA, Sparks KM, Uthicke S, Karelitz S, Barker M, Byrne M, Lamare M (2016) Contributions of genetic and environmental variance in early development of the Antarctic sea urchin Sterechinus neumayeri in response to increased ocean temperature and acidification. Mar Biol 163:130CrossRefGoogle Scholar
- IPCC (2014) Climate change 2014: synthesis report. Contribution of working groups I, II and III to the fifth assessment report of the intergovernmental panel on climate change. IPCC, Geneva, SwitzerlandGoogle Scholar
- Kinoshita K, Fujii Y, Fujita Y, Yamasu K, Suyemitsu T, Ishihara K (1992) Maternal exogastrula-inducing peptides (EGIPs) and their changes during development in the sea urchin Anthocidaris crassispina. Dev Growth Differ 34:661–668. https://doi.org/10.1111/j.1440-169X.1992.tb00034.x CrossRefGoogle Scholar
- Lee T, Leung W, Ginn E (2008) Rainfall projections for Hong Kong based on the IPCC fourth assessment report. Hong Kong Meteorol Soc Bull 18:12–22Google Scholar
- Strathmann MF (1987) Reproduction and development of marine invertebrates of the northern Pacific coast: data and methods for the study of eggs, embryos, and larvae. University of Washington Press, SeattleGoogle Scholar
- Yamasu K, Watanabe H, Kohchi C, Soma G-I, Mizuno D-I, Akasaka K, Shimada H, Suyemitsu T, Ishihara K (1995) Molecular cloning of a cDNA that encodes the precursor to several exogastrula-inducing peptides, epidermal-growth-factor-related polypeptides of the sea urchin Anthocidaris crassispina. Eur J Biochem 228:515–523. https://doi.org/10.1111/j.1432-1033.1995.0515n.x CrossRefPubMedGoogle Scholar