Establishing the sea cucumber as an emerging model in developmental biology

5/7/2025

By Caroline Halmi

Margherita Perillo, a research scientist at the Marine Biological Laboratory (MBL), was awarded the 2024 Society for Developmental Biology Emerging Research Organism Grant for her work on establishing the sea cucumber (Holothuria tubulosa), as an emerging model for developmental biology research. The award recognizes Perillo’s pioneering work in developing methods to generate and culture larvae in the laboratory; work she has done in collaboration with her colleagues at the MBL and at the Stazione Zoologica Anton Dohrn in Naples, Italy.

Sea cucumbers belong to the phylum Echinodermata, which includes starfish, sea urchins, and sea lilies. Despite appearances, echinoderms have a close evolutionary relationship with vertebrates, which makes them valuable tools for research. Like vertebrates they possess a central nervous system, a digestive tract with both mouth and anus, and segmented body plans. Perillo highlighted their ability to regenerate their entire bodies when cut in half and their quick responses to external stimuli. Sea cucumbers also have a distinct defense mechanism against predators: when threatened, they eject their internal organs into the water in a process known as evisceration. This creates a cloud of organs that distracts predators and gives the sea cucumbers time to escape. Within a few months, the sea cucumber will have regenerated all the lost organs.

Sea cucumber, Holothuria tubulosa. (Credit: Margherita Perillo)

Unlike most animals, sea cucumbers and all echinoderms undergo extreme changes in body structure during their development and establish their body plans twice. As larvae, they possess bilateral symmetry, meaning their bodies are symmetrical along a central axis. This is followed by metamorphosis, where their bodies and organs are drastically remodeled. As adults, they acquire pentameral symmetry, where the body is divided into five equal parts. Amongst echinoderms, sea cucumbers have distinct characteristics that make them valuable tools for understanding the development and evolution of body plans. They are the only echinoderm that retains both bilateral and pentameral symmetry in adulthood. Additionally, sea cucumbers undergo their remodeling without an opaque rudiment found in other echinoderms, making it easier to study underlying developmental processes.

Perillo’s own scientific journey was not a direct one. Originally from Italy, she began her career at the University of Napoli Federico II studying pharmaceutical biotechnology and drug development before enrolling in a doctoral program at the Stazione Zoologica Anton Dohrn in Naples where she was introduced to both developmental biology and marine species while studying gut morphogenesis in the sea urchin. Though Perillo has worked with more traditional organisms like Drosophila melanogaster, her interests led her back to echinoderms. When asked whether she would ever be interested in transitioning her research away from marine organisms, she gently declined. “Life came from the ocean, and the majority of species still live in the ocean,” she said. “I like that [echinoderm] embryos … are small, you can make tons of them, and they are super cheap to keep in the lab.”

One of the main hurdles in using sea cucumbers as models is their reproductive cycles. Although they can reproduce asexually, they primarily rely on sexual reproduction in the wild. Environmental factors contribute to the release of oocytes, making it difficult to continuously generate larvae in a lab. However, Perillo and her colleagues have identified a peptide that triggers the maturation of oocytes, allowing them to generate sea cucumber embryos in the lab year-round. She has also identified unique groups of cells present in sea cucumber larvae that are not found in other echinoderm species. With the SDB Emerging Research Organism Grant she hopes to discover whether these cells contribute to the unique mode of sea cucumber development.

Perillo plans to uncover the shared and unique features of sea cucumber body remodeling and organogenesis using transcriptomics at different developmental stages. Using in situ hybridization, she will spatially map gene expression patterns to understand how these patterns drive development. Further down the road, she wishes to create the first gene-editing tools for the sea cucumber, something that will greatly enhance its use as a model organism. To that end, she also plans to make her transcriptome data publicly available to ensure that other investigators can use it to further explore sea cucumber development.

If her ground-breaking research invites, skepticism, Perillo is used to it. “It’s happened to me all my life,” she said. “People asked me ‘Why do you study sea stars instead of flies?’ Then I studied flies, and people asked me, ‘Why don’t you study the mouse instead of flies?’” By exploring the body plan and organogenesis of an animal that is distinct from even its closest relatives, Perillo’s ultimate goal is to advance our understanding of evolutionary developmental biology, while at the same time demonstrating how lesser-known organisms can help us gain a greater understanding of life’s diversity.

“Nature is very broad. If you only study one animal, you don’t have a clear view of how nature works,” she said. Expanding further on the topic, Perillo believes that staying inquisitive and eager to explore our surroundings is important to continue understanding biology. “It’s what scientists have done since the 1800s.”

Perillo would like to thank her colleague, Rossella Annunziata at the Stazione Zoologica Anton Dohrn for kindly sharing her space with Perillo and greatly contributing to the development of this new system. This work would not be possible without Annunziata’s support. She would also like to acknowledge the EngageBio post-bac scholar Talia Marc in the Perillo lab who is now working to develop the MBL local sea cucumber species as an additional model for developmental biology.

Last Updated 05/07/2025