West Indian Sea Egg, Tripneustes ventricosus

West Indian Sea Egg, Tripneustes ventricosus. Underwater photograph taken in coastal waters off Cozumel Island, Quintana Roo, March 2021. Photographs and identification courtesy of Marina Sutormina, Stockholm, Sweden.

Phylogeny: The West Indian Sea Egg, Tripneustes ventricosus, (Lamarck, 1816) is a member of the Toxopneustidae Family of Globular Sea Urchins. There are eight genera in that family.  The Tripneustes genus has four members, two of which reside in Mexican waters; this species in the Atlantic Ocean and one in the Pacific Ocean.  This species is also known as the White Sea Urchin and in Mexico as erizo blanco. The West Indian Sea Egg is very similar to and easily confused with the Collector Sea Urchin, Tripneustes gratilla (resident of the Indian Ocean and central and western Pacific Ocean).

Morphology: The West Indian Sea Egg has a large semi-spherical dark black, dark purple or reddish brown test (shell) with white bands and radial symmetry with white spines that are 1.0 cm (0.4 inches) to 2.0 cm (0.8 inches) in length. The protrusible mouth (Aristotle’s Lantern) is found at the center of the underside of the disc; the anus on the dorsal side of the disc. The bottom of the test has tube feet and pedicellariae. West Indian Sea Eggs reach a maximum of 15 cm (5.9 inches) in diameter, and are often found covered with pieces of seagrass, shell fragments, and other debris which they acquire for protection from sunlight.

Habitat and Distribution:  West Indian Sea Eggs are found predominately in seagrass meadows, rubble areas, and under shallow rocky reefs ledges. They live intertidally, and to depths of 55 m (180 feet), though most are found in the top 10 m (33 feet). They are mobile, taking shelter during daylight hours in crevices and under rocks, and emerge at night for feeding. In Mexican waters the West Indian Sea Egg is found in the eastern Gulf of Mexico and the Caribbean within coastal waters of Campeche, Yucatán, and Quintana Roo.

Diet:  West Indian Sea Eggs primarily eat algae, supplemented with small organisms and sea grasses.

Predators:  Their pedicellariae of West Indian Sea Eggs are tipped with poison which is used for defense against predation by the Cushion Sea Urchin, Oreaster reticulatus, the Long-spine Sea Urchin, Diadema antillarum,  the Slate Pencil Urchin, Eucidaris tribuloideds, and the large gastropods Cassis tuberosa and Charonia variegata.  Their spines are also utilized for defense.  Young West Indian Sea Eggs are eaten in large number by Queen Triggerfish. Their roe is also consumed in large quantities by parrotfish, pufferfish and triggerfish.

Reproduction: West Indian Sea Eggs are gonochoric (male or female for life).  Reproduction is sexual and fertilization is external. Reproduction occurs twice a year in six-month intervals in large groups and involves both sexes with broadcast spawning into the sea where fertilization takes place. The females’ gonads are bright orange and the males’ gonads are light yellow. The eggs hatch quickly into planktonic larvae that undergo a series of larval stages before settling out on the seabed and undergoing metamorphosis into juveniles. Adult females normally outnumber adult males by 3:2 in most locations. The have life spans of just three years.

Ecosystem Interactions: The West Indian Sea Eggs hosts the parasitic shrimp Gnathophylloides mineri. These shrimp, up to a dozen per urchin, eat the epithellium which covers the urchin’s spines.

Human Interactions:  Seasonal roe harvesting of the West Indian Sea Egg is considered to be of significant cultural and economic value and is an important human food source throughout the Caribbean. Urchin roe is considered to be a traditional delicacy. Each of the Caribbean countries has historically harvested in excess of one million urchins annually. They have been heavily pursued commercially and have been subject to overfishing to near extinction regionally. As they are a shallow water species they are easily collected by hand, at levels of a thousand in a few hours with a focus on the mature adults. They are sold for high prices, representing an important source of income that does not require a significant investment in equipment. Their populations are also significantly affected by hurricanes, storm runoffs, increasing water temperature and toxins, including phosphates, nitrates, and sewage effluent. Major conservation efforts are ongoing to preserve or reestablish the fishery in many areas which include seasonal fishing closures, limited numbers of fishing permits, collection quotas and size harvesting limits. However, collection information is limited, significantly underreported, and such regulations are poorly enforced. They are subject to year-round poaching, including international illegal seafood trade. Efforts to rebuild regional depleted stock by aquaculture are on-going.

A Word of Caution!  The West Indian Sea Egg is not very venomous, but should be handled with care because the spines are sharp, will break off in the skin, can be very painful to humans and are exceedingly difficult to remove completely.

Synonyms: Echinus ventricosus, Heliechinus gouldii, Hipponoe esculenta, Tripneustes esculenta, and Tripneustes esculentus.