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Care Guide: Sea Urchins for Embryological Studies

Living Care Information

Eucidaris tribuloides, Lytechinus variegatus
commonly known as pencil urchin,
green sea urchin, variegated sea urchin

Quick Start Information

  • Fertile sea urchins are shipped directly from our vendor after they are collected. Use the urchins within 3 days of receipt to produce optimal numbers of gametes.

  • We ship two species of sea urchins: Eucidaris tribuloides or Lytechinus variegatus.

  • Sea urchins will begin to reabsorb their gametes after they are collected. Most will not produce gametes 4 days after receipt.

  • Sea urchin gametes can be stored, but for best results, plan to use the gametes the day they are released.

About the Organism

  • Both of our urchin species are collected from the tropical waters of the Western Atlantic ocean.
  • In nature, sea urchin reproduction is controlled by both seasonal and lunar cycles.
  • Sea urchins breed year round, but peak fertility occurs in the late summer to early fall around the full moon.
  • Sea urchins are habitually nocturnal creatures. They anchor themselves atop rocks or in crevices during the day time.
  • A sea urchin larva is called a pluteus.
  • Domain: Eukarya
  • Kingdom: Animalia
  • Phylum: Echinodermata
  • Class: Echinodea
  • Order: Cidaroida
  • Family: Cidaridae
  • Genus: Eucidaris
  • Species: tribuloides
  • Domain: Eukarya
  • Kingdom: Animalia
  • Phylum: Echinodermata
  • Class: Echinodea
  • Order: Temnopleurioda
  • Family: Toxopneustidae
  • Genus: Lytechinus
  • Species: variegatus


The Sea Urchin Embryology Kit includes a gallon of seawater. If you are not using the kit, we recommend that you have on hand 1 gallon or more of Carolina™ Seawater. You can use Instant Ocean® Synthetic Sea Salt or a similar product if you prepare it at least 48 hrs before you receive the urchins. Mix the salts with water according to the instructions on the packaging. If the instructions are missing, mix the salts with water to get a specific gravity between 1.020 and 1.025.


We ship each urchin in its own bag with a small amount of seawater. Keep the urchins separated. If they are mixed, they may be stimulated to release their gametes before you are ready to collect.

Open the bags. The urchins can be left in the bags or transferred to individual glass or plastic containers. Deli cups work well for this (64 oz). Cover the tops of the containers to prevent the urchins from crawling out.

Slowly add seawater until the spines of the urchins are covered. Adding water too rapidly can stress the urchins. Stress is indicated by retraction of the tube feet or drooping of the spines. If the water in a shipping bag is cloudy, discard it and replace with fresh seawater. If you have the option, aerate with an air stone. Occasionally inspect the containers until you are ready to use the urchins.


Urchins being used for embryological studies do not require feeding. Feeding may foul the water in the holding containers, killing the urchins. Urchins in an established tank can be offered chopped fish or shrimp, lettuce leaves, or seaweeds. Place any food directly under the animal to encourage it to eat. Remove any uneaten food to prevent fouling the tank.

Maintaining and culturing

After their gametes are extracted, the urchins can be added to an established marine aquarium. Float them in a bag in the tank for about 20 minutes to equalize the temperature. Add some aquarium water to the bag and observe the urchins for signs of stress. Once urchins are acclimated, release them into the tank. Keep a close watch on them for a few days. If an individual urchin begins to lose spines, remove it so it does not foul the aquarium.


Carolina provides living organisms for educational purposes only. As a general policy, we do not advocate the release of organisms into the environment. In some states, it is illegal to release organisms, even indigenous species, without a permit. The intention of these laws is to protect native wildlife and the environment.

We suggest that organisms be:

  • Maintained in the classroom
  • Donated to another classroom or science department
  • With parental permission, adopted or taken home by students
  • Donated to a nature center or zoo
  • Frozen in a sealed bag and disposed of according to your state and local regulations


No Biosafety information needed for this organism.


No suggested Video or Video Playlist available for this organism.


We will receive our sea urchins on Wednesday or Thursday. Can we hold them until our lab on the following Monday?

You can, but the delay may reduce the urchins’ gamete production. It would be better to schedule your lab closer to the time of the urchins’ arrival.

Should we refrigerate the urchins?

No, these are warm-water animals and chilling them may result in reduced gamete production.

How do I extract sea urchin gametes?

Procedures for extracting gametes and observing development are given in the instructions sent with the Sea Urchin Embryology Kit. There are also instructions available through Stanford University.

Can I collect sea urchin gametes and use them for classes that meet later in the week?

This is possible, but gamete viability decreases over time. For best results, use gametes the day they are released. Sperm must be collected dry and refrigerated. Do not allow sea urchin sperm to come into contact with seawater. Eggs can be collected, stored in seawater, and refrigerated overnight.

How can I tell male from female sea urchins?

There are no external differences. The difference will become apparent once you inject the urchins and see initial expulsion of the gametes (eggs are yellow, sperm white).

Need help?

We want you to have a good experience. Orders and replacements: 800.334.5551, then select Customer Service. Technical support and questions: caresheets@carolina.com