Contributors: Estefania Paredes Rosendo, University of Vigo (UVigo, Spain); Maria Ina Arnone, Stazione Zoologica Anton Dohrn (SZN, Italy); Jenifer Croce, LBDV – Institut de la Mer de Villefranche (IMEV, France); Stefania Castagnetti, LBDV – Institut de la Mer de Villefranche (IMEV, France), Eva Jimenez-Guri, Centre for Ecology and Conservation, University of Exeter.

About the organism

As echinoderms, sea urchins are part of the large family of animals called the Deuterostomes, which further include us, humans. They thus share with humans and vertebrates in general comparable developmental and molecular features that make them important models in biology. 

Sea urchins, and in particular Paracentrotus lividus (P. lividus) have been used as model systems in biology and ecotoxicology for more than a century now. This species can be found in intertidal and subtidal areas rocky shores of the Atlantic Ocean from north of Africa to the UK and the Mediterranean Sea. 

The sea urchin is a gamete ‘production powerhouse’. Male and female sea urchins are easily induced to shed massive numbers of eggs or sperm. The eggs are mature at release and are fertilised externally simply by mixing egg and sperm. Given the transparency of the egg, the synchronicity of divisions, the ease of manipulation and the abundance of gametes, P. lividus provides an excellent system to address general cell biological questions. 

Picture of a sea urchin
Sea urchin picture from the OCIMER project at UVIGO

Relevant fields of research 

Sea urchins are used in ecotoxicology (ie the study of the effects of toxic chemicals on biological organisms). Current strategies of water quality assessment integrate chemical analysis with biological parameters to evaluate the effects of pollution on living resources. 

Due to the sensitivity of the early stages of development to pollutants present in seawater even at very low concentrations, sea urchin embryo-larval bioassays have been routinely used for water quality assessment for decades. P. lividus is one of the most widely used for this purpose in the eastern Atlantic Ocean and the Mediterranean Sea. 

Sea urchins have also been established as a good model for cryopreservation (ie the process of cooling and storing cells, tissues, or organs at very low temperatures to maintain their viability). 

Sea urchins have been studied since the 19th century as model organisms in developmental biology (ie the scientific discipline primarily concerned with embryogenesis), as their embryos are relatively large and easy to observe. Biologists have in effect relied on a relatively small number of model organisms, including sea urchins, to study the cellular, molecular, and genetic mechanisms of embryogenesis[i]. Sea urchins remain extremely useful today in the field of development biology, which has greatly evolved over the decades. They are frequently used in genome studies because of their unusual fivefold symmetry and relationship to chordates. 

Recently the sea urchin has been used to analyse microtubule dynamics during mitosis and to address questions of organelle scaling in cells[ii]For example, Lacroix et al. used live cell imagine to analyse spindle scaling during embryo cleavage in the nematode Caenorhabditis elegans and sea urchin P. lividus. They revealed a common scaling mechanism, where the growth rate of spindle microtubules scales with cell volume, which explains spindle shortening.

Picture of baby sea urchins
Baby sea urchins

What are the available tools or techniques to study the marine organism?

All classical developmental biology techniques and tools are available to study sea urchin embryos and larvae. The techniques include pharmacological treatment, microinjection into oocytes, fertilised eggs or blastomeres of RNA, DNA, Morpholino antisense oligonucleotides or CRISPR/Cas9, in situ hybridisation, immunohistochemistry, and live imaging. 

The tools include several cDNA libraries available for distinct embryonic stages, BAC libraries, as well as transcriptomic and genomic resources. The MARIMBA website aims to provide all sorts of resources related to the sea urchin species P. lividus, including primer sets for qPCR, general protocols, a developmental and anatomical ontology and diverse spatial and temporal expression patterns. For information on sea urchin sequencing, see Echinobase or the Human Genome Sequencing Center (HGSC).

Impact & commercial application

Sea urchin eggs, embryos and larvae are notoriously use in embryotoxicity tests. They could thus have a potential commercial interest as environmental indicators. Sea urchins, and in particular P. lividus, are also of great interest for fisheries and aquaculture purposes as they are edible animals.

Picture of a purple sea urchin

Example of research done at EMBRC sites

How have EMBRC users made use of sea urchins for their research at EMBRC sites? One example is provided by Dr Eva Jimenez-Guri from the University of Exeter, who conducted research on the ‘Effects of microplastics on the development of sea urchins (P. lividus)’ through the EMBRC-coordinated ASSEMBLE Plus programme. She conducted her research in part at the EMBRC Italy partner site Stazione Zoologica Anton Dohrn (SZN) in Naples and the Institute of Oceanology, Polish Academy of Sciences, Sopot, Poland: 

‘We wanted to determine the embryotoxicity of chemicals present in plastic particles. We used particles accidentally found in the environment and particles used in the fabrication process. After soaking those plastics in sea water for 72 hours, we removed them and used the water to raise sea urchin (Paracentrotus lividus) embryos. We determined that plastics had leached toxic chemicals (PAHs and PCBs) into the water. The developing sea urchin larvae were affected by chemicals released from microplastics: gastrulation was delayed, axis formation was abnormal, and the skeletons and nervous and immune systems were affected. Our findings show clear and specific detrimental embryological effects of plastic pollution which, given the conservation of the developmental processes, may be affecting other animal species'.

This work has been published as 'Developmental toxicity of plastic leachates on the sea urchin Paracentrotus lividus (Rendell-Bhatti, Flora, et al. Environmental Pollution 269 (2021): 115744).

Interested in using sea urchins for your research? Check out the EMBRC service catalogue to see where they are available in our 9 member countries.

Related resources, images & videos

[i] Ettensohn CA. Sea urchins as a model system for studying embryonic development. Reference Module in Biomedical Sciences. Amsterdam: Elsevier. 2017 Jan 1.
[ii] Lacroix B, Letort G, Pitayu L, Sallé J, Stefanutti M, Maton G, Ladouceur AM, Canman JC, Maddox PS, Maddox AS, Minc N. Microtubule dynamics scale with cell size to set spindle length and assembly timing. Developmental cell. 2018 May 21;45(4):496-511.

Images: Courtesy of Estefania Paredes Rosendo

Sabrina Gaber
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