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.
The West Indian Sea Egg, Tripneustes ventricosus, (Lamarck, 1816) is a member of the Toxopneustidae Family of Globular Sea Urchins that is also known as the White Sea Urchin and in Mexico as erizo blanco. The Tripneustes Genus has three members of which two reside in Mexican waters, one, this species, in the Atlantic Ocean and one in the Pacific Ocean.
The West Indian Sea Egg has a large semi-spherical dark black, dark purple or reddish brown 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.
West Indian Sea Eggs reach a maximum diameter of 15 cm (5.9 inches), and are often found covered with pieces of seagrass, shell fragments, and other debris which they acquire for protection from sunlight. The bottom of the test has tube feet and pedicellariae. They are found predominately in seagrass meadows, rubble areas and shallow rocky reefs at depths of 10 m (33 feet) spending their entire life within a 1 km range; they have been found at depths of up to 55 m (180 feet). They are mobile, taking shelter during daylight hours in crevices and under rocks, and emerge at night for feeding. Their diet consists primarily of algae supplemented with small organisms and sea grasses. Their pedicellariae 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, and the Slate Pencil Urchin, Eucidaris tribuloideds. Their spines are also utilized for defense. The sexes are indistinguishable unless ripe. 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.
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.
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).
Seasonal roe harvesting of the West Indian Sea Egg is considered to be of significant cultural, economic value and is a human food source throughout the Caribbean where they are considered to be a traditional delicacy. Each of the Caribbean countries has historically harvested in excess of 1 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. Their roe is also consumed in large quantities by parrotfish, pufferfish and triggerfish.
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.