Tripneustes ventricosus

Geographic Range

Tripneustes ventricosus , a tropical sea urchin, inhabits a region stretching from just north of Miami, Florida south through the West Indies into the Caribbean Sea and down to Brazil. The species is also found off the coast of west Africa.

• Biogeographic Regions
• atlantic ocean atlantic ocean
  • native native

Habitat

Within its habitat, Tripneustes ventricosus can be found in two characteristically different places. The first is on sand bottoms in dense beds of grass and algae. The second is on reefs, reef-crest bedrock, and among rocks along shorelines. Tripneustes ventricosus is equipped to withstand the slightly more violent areas such as rocky shorelines and oftentimes coexists with another species, Lytechinus variegatus . This habitat is also tropical with mostly mild to warm temperatures throughout the year.

• Habitat Regions
• tropical tropical
• saltwater or marine saltwater or marine

• Aquatic Biomes
• reef reef
• coastal coastal

• Other Habitat Features
• intertidal or littoral intertidal or littoral

Physical Description

Tripneustes ventricosus has highly developed external appendages. Its body shape is a dark brown, hemispherically shaped test that can grow to horizontal diameters as great as 150 mm. The test is what provides support for internal organs, spines, and tube feet. Three different sizes of short spines with a white coloring protrude from the test as well as globiferous pedicellariae that are covered in a thick, dark brown layer of tissue. Tube feet are located on the aboral side of the urchin and have the same coloring as the test. A white nerve ganglion is visible near the terminal disks, also of the same uniform brown color on the same side, near the tube feet. On the oral side, coloring becomes a lighter brown with spines and feet retaining the same physical characteristics as mentioned above. The peristome, or mouth, is this light brown, but tissue around the jaws returns to the dark brown that is seen on the rest of the urchin.

• Other Physical Features
• ectothermic ectothermic
• heterothermic heterothermic
• radial symmetry radial symmetry

Development

The life cycle of Tripneustes ventricosus begins when the eggs of the species are released into the water to be externally fertilized. After fertilization occurs, T. ventricosus goes through a life cycle consisting of a planktotrophic larval stage followed by metamorphosis, after which the species is at the juvenile stage. Growth occurs until the adult stage is reached, at which point the gonads have developed enough to release either eggs or sperm into the water, depending on whether the individual is female or male, respectively. After sexual maturity, T. ventricosus can continue to grow in size, but reproductive capacity will not increase. This life cycle proceeds under normal conditions, but in the event that temperatures become abnormally low, T. ventricosus can become hermaphroditic until temperatures return to normal. Sexual reproduction is the normal method of reproduction, and the species is gonochoric with males and females of approximately equal size. Experimental results have proven inconclusive when determining whether the gender of the species is chromosomally determined.

• Development - Life Cycle
• metamorphosis metamorphosis
• temperature sex determination

Reproduction

Sexual reproduction with external fertilization is the normal means of reproduction for Tripneustes ventricosus . Since fertilization is external and in an aquatic environment, it is not necessary for the male to make an effort to mate with the female. Each gender, at the appropriate time, just releases the gametes corresponding to its sex, and that is all that is necessary. The males and females do not interact with one another physically to reproduce. The male to female sex ratio does not deviate much from the normal 1:1 ratio. In individuals with horizontal diameters ranging from 80-100 mm, the ratio is 1:1.5. In the smaller individuals, the ratio is 1:1.

The reproductive behavior of Tripneustes ventricosus relies on a number of factors including temperature and increasing age. There is a correlation between larger gonads and colder winters. Also, reproductive output decreases four-fold with the increasing age of the urchin. Spawning is observed with T. ventricosus , and since the gonads are temperature dependent, the severity of the winter season can be a good indicator of the spawning pattern that will be followed the next summer. In general, this species exhibits two spawnings per year, each of them six months apart.

• Key Reproductive Features
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• simultaneous hermaphrodite
• sexual sexual
• fertilization fertilization
  • external external

Since external fertilization takes place, the egg, once fertilized, could be miles away from one of the two parent urchins. Therefore, parental care is not observed.

• Parental Investment
• pre-fertilization
  • provisioning

Lifespan/Longevity

The lifespan of Tripneustes ventricosus in most cases, is two to three years. Environmental changes, predators, and other external causes can reduce the lifespan of individuals. On the other hand, if an individual is held in captivity with optimum conditions at all times, the lifespan of that individual is likely to increase slightly.

Behavior

The most interesting and most studied aspect of the behavior of Tripneustes ventricosus deals with phototaxis. Tripneustes ventricosus does not like light, and responds accordingly by a covering reaction. Using its tube feet, an individual of the species takes up a fragment of eel grass, shell gravel, algae, or some other opaque object, and it "masks" its upper surface from excess light with this fragment.

Behavior in response to predation involves the globiferous pedicellariae. Varying in position on the either large or small pedicellariae are both glandular tissue and valves with poison glands. Aiding in this defense mechanism, the heads of the pedicellariae automise after they have been used. When this happens, it causes a chain reaction with the pedicellariae of other individuals in the area, and they automise as well.

• Key Behaviors
• nocturnal nocturnal
• motile motile

Communication and Perception

Tripneustes ventricosus communicates with other individuals when predators are around. Varying in position on the either large or small pedicellariae are both glandular tissue and valves with poison glands. The heads of the pedicellariae automise after they have been used. When this happens, it causes a chain reaction with the pedicellariae of other individuals in the area, and they automise as well.

• Communication Channels
• chemical chemical

• Perception Channels
• visual visual
• tactile tactile
• chemical chemical

Food Habits

Tripneustes ventricosus is an omnivore, depending upon environmental conditions. Foods eaten include algae, aquatic grasses, plants and small organisms in the environment.

For the urchin to feed, there must be a strong flow of water over it. Temperature changes have an effect on feeding. Higher summer temperatures lead to a general slight feeding in the species, whereas in lower temperatures, the feeding rate increases. An important anatomical aspect of feeding is the lantern mechanism. This mechanism provides a way for T. ventricosus to bite off and ingest food.

• Primary Diet
• omnivore omnivore

• Animal Foods
• aquatic or marine worms
• aquatic crustaceans
• other marine invertebrates

• Plant Foods
• algae
• macroalgae macroalgae

• Other Foods
• microbes

Predation

Globiferous pedicellariae, or poisonous pedicellariae, are the best line of defense for Tripneustes ventricosus . Varying in position on the either large or small pedicellariae are both glandular tissue and valves with poison glands. The heads of the pedicellariae automise after they have been used, causing a chain reaction with the pedicellariae of other individuals in the area, which automise as well. Released into the surrounding sea water, this automization acts as a defense reaction against the species listed below and against predatory asteroids. The "poison" released from the poison glands has been experimentally determined to be pharmacologically active, and are injurious.

Ecosystem Roles

Tripneustes ventricosus does not really play any major roles in the ecosystem. Part of the food chain, it keeps the underwater environment diverse.

Economic Importance for Humans: Positive

Tripneustes ventricosus provides only a couple of benefits for humans, primarily dealing with food and research. It is considered to be a "gourmet delicacy" in the West Indies, the Mediterranean, and Japan. Since large amounts of eggs are easily obtained, more developmental knowledge has been accumulated from the sea urchin than from any other animal.

• Positive Impacts
• food food
• research and education

Economic Importance for Humans: Negative

Tripneustes ventricosus is in the family Toxopneustidae, the toxic sea urchins. The toxin produced is either injected into other organisms by way of the globiferous pedicellariae, or it is released into the water when the pedicellariae automise after use. Wounds are inflicted in humans by the spines. Sometimes small segments of the spinal epithelium cause a foreign-body reaction, causing either nodules or lesions to form which then have the chance of becoming infected. Although unlikely this is still a the threat for humans.

• Negative Impacts
• injures humans
  • bites or stings

Conservation Status

No information found for this subject.

Additional Links

Encyclopedia of Life

Contributors

Renee Sherman Mulcrone (editor).

Catherine Warlick (author), Southwestern University, Stephanie Fabritius (editor), Southwestern University.

References

Alender, C., F. Russell. 1966. Pharmacology. Pp. 536-537 in Physiology of Echinodermata . New York: Interscience Publishers.

Anderson, J. 1966. Aspects of Nutritional Physiology. Pp. 335-336 in Physiology of Echinodermata . New York: Interscience Publishers.

Hendler, G., J. Miller, D. Pawson, P. Kier. 1995. Sea Stars, Sea Urchins, and Allies: Echinoderms of Florida and the Caribbean . Washington: Smithsonian Institution Press.

Lawrence, J. 1987. A Functional Biology of Echinoderms . Baltimore: The Johns Hopkins University Press.

Moore, H. 1966. Ecology of Echinoids. Pp. 74-82 in Physiology of Echinodermata . New York: Interscience Publishers.

Stearns, L. 1974. Sea Urchin Development: Cellular and Molecular Aspects . Stroudsberg, PA: Dowden, Hutchinson, and Ross, Inc..

Yoshida, M. 1966. Photosensitivity. Pp. 450 in Physiology of Echinodermata . New York: Interscience Publishers.