Species Description: The green sea urchin, Lytechinus variegatus, is one of several urchin species common to Florida and the Caribbean. The spines of L. variegatus are characteristically short, and the underlying test is hemispherical with smoothly curving sides adorned with numerous small tubercles (Hendler et al. 1995). Tubercles are sparse on the aboral portions of the ambulacra and interambulacra, resulting in naked patches. Globiferous pedicellariae are numerous and conspicuous, appearing as stalked and nearly spherical white or pink structures. The color of the test and spines is variable, and has been used to identify subspecies of L. variegatus (Serafy 1973).
Potentially Misidentified Species: L. variegatus is similar in appearance to L. williamsi. However, the latter has purple pedicellariae instead of white or pink, fewer plates in each column of the test, and 12 wedges in the spines compared to the 24 found in L. variegatus (Hendler et al. 1995).
Indian River Lagoon Distribution: The distribution of L. variegatus within the IRL remains undocumented. However, this urchin is likely most abundant in the southern lagoon, where turtle grass beds are more prevalent.
Size: L. variegatus reaches a total diameter of about 110 mm, with a test diameter of about 85 mm (Hendler et al. 1995).
Abundance: In turtle grass beds, L. variegatus can reach extremely high numbers. Although little information is available concerning the abundance of this species in the IRL, densities of L. variegatus in other locations have been reported at 636 individuals per square meter (Camp et al. 1973).
Reproduction & Embryology: The green sea urchin is normally gonochoric. Reproduction of hermaphroditic individuals has been linked to abnormally low water temperatures (Moore et al. 1963). The spawning period of the green sea urchin is shorter in northern latitudes (Moore et al. 1963). In tropical locations like Panama, L. variegatus is sexually ripe throughout the year (Lessios 1985, 1991). In Florida, reproduction varies with season and environmental conditions (Ernest & Blake 1981). Mazur & Miller (1971) reported a reproductive season of March to October for Florida urchins held in the laboratory. Spawning in Panama, and possibly other locations, tends to occur during the new and full moons (Lessios 1991).
Pearce & Cameron (1991) provide a review of the extensive literature available describing fertilization and early development in L. variegatus. Full development from zygote to metamorphosis takes 33-43 days in the laboratory (Mazur & Miller 1971), and can be accelerated by increasing the water temperature (Petersen & Almeida 1976). Salinities below 35 ppt result in decreased larval survival and developmental rates, even when the parents are acclimated to such salinities (Roller & Stickle 1993). In response to low food supply, larvae can increase their feeding efficiency by enlarging their ciliated bands (Boideron-Metairon 1988). After metamorphosis, juveniles can grow to a test diameter of about 15 mm in 6 months, and to 25 mm in 9 months (Pawson & Miller 1982, Michel 1984). Pearse & Cameron (1991) found some evidence for a difference in the number of chromosomes between male and female urchins.
Trophic Mode: When population densities are high, L. variegatus can overgraze seagrass beds (Camp et al. 1973). However, studies have shown that the majority of the reported 0.6 g dry weight of T. testudinum consumed daily by each urchin consists of dead blades, having a minimal effect on live turtle grass (Vadas et al. 1982).
Movement & Behavior: L. variegatus often covers itself with plant and shell debris, holding the material in place with its tube feet (Mortensen 1943, Millott 1956, Sharp & Gray 1962, Kier & Grant 1965). Millott (1956) documented a rise in covering behavior in response to increased light levels, suggesting that the collected debris acts to shade the animal from strong light.
Predators: Predators of this urchin include: several species of fish (Randall 1967), shorebirds such as ruddy turnstones, Arenaria interpres (Hendler 1977), and herring gulls, Larus sp. (Moore et al. 1963); the reticulate cowrie-helmet, Cypraecassis testiculus (Hendler 1977); and the Caribbean helmet, Cassis tuberosa (Engstrom 1982).
Parasites & Associated Species:
The turbellarian, Syndisyrinx collongistyla, has been reported to infest the body cavity and intestines of L. variegatus (Nappi & Crawford 1984, Hertel et al. 1990). Protozoan parasites are also reported for this urchin (Mortensen 1943). The polychaete, Podarke obscura, has been listed as an occasional associate (Ruppert & Fox 1988).
Boideron-Metairon IF. 1988. Morphological plasticity on laboratory-reared echinoplutei of Dendraster excentricus (Eschscholtz) and Lytechinus variegatus (Lamarck) in response to food conditions. J. Exp. Mar. Biol. Ecol. 119: 31-41.
Camp DK, Cobb S & JF van Breeveld. 1973. Overgrazing of seagrasses by a regular urchin, Lytechinus variegatus. BioScience 23: 37-38.
Engstrom NA. 1982. Immigration as a factor in maintaining populations of the sea urchin Lytechinus variegatus (Echinodermata: Echinoidea) in seagrass beds on the southwest coast of Puerto Rico. Studies Neotrop. Fauna Environ. 17: 51-60.
Ernest RG & NJ Blake. 1981. Reproductive patterns within sub-populations of Lytechinus variegatus (Lamarck) (Echinodermata: Echinoidea). J. Exp. Mar. Biol. Ecol. 55: 25-37.
Hendler G. 1977. The differential effects of season stress and predation on the stability of reef-flat echinoid populations. In: Taylor DL (Ed.). 217-223. Proceedings: Third International Coral Reef Symposium. Volume 1 (Biology). Rosenstiel School of Marine & Atmospheric Science, University of Miami. Miami, Florida.
Hendler G, Miller JE, Pawson DL & PM Kier. 1995. Sea stars, sea urchins, and allies: echinoderms of Florida and the Caribbean. Smithsonian Institution Press. Washington, D.C. 390 pp.
Hertel L, Duszynski DW & JE Ubelaker. 1990. Turbellarians (Umagillidae) from Caribbean urchins with a description of Syndisyrinx collongistyla, n. sp. Trans. Amer. Microscop. Soc. 109: 272-281.
Kier PM & RE Grant, 1965. Echinoid distribution and habits, Key Largo Coral Reef Preserve, Florida. Smithsonian Misc. Collect. 149: 1-68.
Lessios HA. 1985. Annual reproductive periodicity in eight echinoid species on the Caribbean coast of Panama. In: Keegan BF & BDS O’Connor (Eds.). 303-311. Echinodermata. Proceedings of the Fifth International Echinoderm Conference. Galway, 24-29 September 1984. Belkema, Rotterdam.
Lessios HA. 1991. Presence and absence of monthly reproductive rhythms among eight Caribbean echinoids off the coast of Panama. J. Exp. Mar. Biol. Ecol. 153: 27-47.
Mazur JE & JW Miller. 1971. A description of the complex metamorphosis of the sea urchin Lytechinus variegatus cultured in synthetic sea water. Ohio J. Sci. 71: 30-36.
Michel HB. 1984. Culture of Lytechinus variegatus (Lamarck) (Echinodermata: Echinoidea) from egg to young adult. Bull. Mar. Sci. 34: 312-314.
Millot N. 1956. The covering reaction of sea urchins. 1. A preliminary account of covering in the tropical echinoid Lytechinus variegatus (Lamarck), and its relation to light. J. Exp. Biol. 33: 508-523.
Moore HB, Jutare T, Bauer JC & JA Jones. 1963. The biology of Lytechinus variegatus. Bull. Mar. Sci. Gulf Carib. 13: 23-53.
Mortensen T. 1943. A Monograph of the Echinoidea. Volume III. (3). Camarodonta. I. Orthopsidae, Glyphocyphidae, Temnopleuridae and Toxopneustidae. CA Reitzel, Copenhagen. vii + 553 pp. 56 pls.
Nappi AJ & JA Crawford. 1984. The occurrence and distribution of a syndesmid (Turbellaria: Umagillidae) in Jamaican sea urchins. J. Parasitol. 70: 595-597.
Pawson DL & JE Miller. 1982. Studies of genetically controlled phenotypic characters in laboratory-reared Lytechinus variegatus (Lamarck) (Echinodermata: Echinoidea). In: Lawrence JM (Ed.). 165-171. Echinoderms: Proceedings of the International Conference. Tampa Bay, 14-17 September 1981. Balkema, Rotterdam.
Pearse JS & RA Cameron. 1991. Echinodermata: Echinoidea. In: Giese AC, Pearse JS & VB Pearse (Eds.). 513-662. Reproduction of Marine Invertebrates, Volume VI, Echinoderms and Lophophorates. The Boxwood Press. Pacific Grove, CA.
Petersen JA & AM Almeida. 1976. Effects of salinity and temperature on the development and survival of the echinoids Arbacia, Echinometra and Lythechinus. Thalassia Jugoslavia 12: 297-298.
Randall JE. 1967. Food habits of reef fishes of the West Indies. Inst. Mar. Sci. Univ. Miami. Studies in Tropical Oceanog. No. 5: 665-847.
Roller RA & Stickle. 1993. Effects of temperature and salinity acclimation of adults on larval survival, physiology, and early development of Lytechinus variegatus (Echinodermata: Echinoidea). Mar. Biol. (Berlin) 116: 583-591.
Ruppert, EE & RS Fox. 1988. Seashore animals of the Southeast: A guide to common shallow-water invertebrates of the southeastern Atlantic coast. University of SC Press. Columbia, SC. USA. 429 pp.
Serafy DK. 1973. Variation in the polytypic sea urchin Lytechinus variegatus (Lamarck, 1816) in the western Atlantic (Echinodermata: Echinoidea). Bull. Mar. Sci. 23: 525-534.
Serafy DK. 1979. Echinoids (Echinodermata: Echinoidea). Memoirs of the Hourglass Cruises 5: 1-120.
Sharp DT & IE Gray. 1962. Studies on factors affecting the local distribution of two sea urchins, Arbacia punctulata and Lytechinus variegatus. Ecology 43: 309-313.
Vadas RL, Fenchel T & JC Ogden. 1982. Ecological studies on the sea urchin Lytechinus variegatus and the algal-seagrass communities of the Miskito Cays, Nicaragua. Aquat. Botany 14: 109-115.
Aboral: In a direction away from the mouth; the part of the body opposite the mouth.
Anal Cone: In crinoids and echinoids, a fleshy projection bearing the anus at its apex; also known as an anal tube.
Apical System: In echinoids, a ring of specialized skeletal plates, including the genital plates and ocular plates; usually located on the highest point of the test.
Arm: In asteroids, crinoids, and ophiuroids, a movable, jointed ambulacral projection, distal to the disk or calyx that carries a radial branch of the water vascular system and the nervous system; sometimes called a ray.
Basket: One of several types of microscopic skeletal ossicles in holothuroids; minute cup-shaped ossicle, usually with four projections.
Button: One of several types of microscopic skeletal ossicles in holothuroids; minute ossicle with four perforations; may be smooth or knobbed.
Disk: The round or pentagonal central body region of ophiuroids and asteroids; see also Terminal Disk.
Distal: In a direction away from the center of the body; for example, toward the tip of the arm in asteroids or the tip of a spine in echinoids.
Dorsal: In echinoderms, this term is variously applied; in asteroids, ophiuroids and echinoids it usually refers to the surface of the body that is opposite the mouth, the surface that is uppermost; in holothuroids, with mouth and anus opposite ends of the cylindrical body, the uppermost surface is considered dorsal; in crinoids, the surface opposite the mouth in considered dorsal by convention, even though it is functionally the ventral (lower) side.
Echinulate: Something spiny or prickly, usually referring to the microscopic texture of a skeletal element such as a spine.
Hermaphrodism: A condition in organisms whereby one individual possesses both functional male and female reproductive structures; hermaphroditic individuals may express both sexes simultaneously, alternately, or sequentially.
Interambulacral Area: An oral or aboral section of the body lying between two ambulacra; in interradius; also known as an interambulacrum.
Interradial: Referring to interambulacral areas of the body; interradius and interradii also commonly used.
Oral: In a direction toward the mouth; a part of the body on the same surface as the mouth.
Oral Papillae: In ophiuroids, small plates at the edge of the mouth, attached to the edges of the jaw plate and/or to the aboral shield; may be variously shaped, from spine-like to scale-like.
Papillae: In holothuroids, specialized dorsal tube feet that lack a suckered tip; in ophiuroids, certain skeletal elements of the jaws or disk.
Papillate: Covered with papillae.
Papillose: Covered with papillae.
Pedicellariae: Small stalked or unstalked pincer-like organs on the body of asteroids and echinoids, used for defense and grooming.
Peltate: Shield-shaped; used to describe the tentacles of some holothuroids.
Perforated Plate: One of several types of microscopic skeletal ossicles in holothuroids; sieve-like and widespread; may also be found in other echinoderm classes, especially in juvenile individuals.
Periproct: In echinoids, a flexible region surrounding the anus, which consists of a membrane containing embedded plates and often bearing spines and pedicellariae.
Plates: One of several types of skeletal elements in echinoderms; tabular structures with a characteristic shape and a fixed position.
Primary Plates: The first-formed plates on the dorsal side of the disk; in ophiuroids, these are the central and five radial plates; in adults, they may form a rosette of scales near the center of the disk, or they may be separated by numerous secondarily developed scales.
Radial: In a direction toward the central axis of an arm or ambulacrum; a part of the body near an arm or ambulacrum.
Radial Shields: Pairs of plates on the dorsal surface of the ophiuroid disk, which lie near the base of each arm; usually relatively large and conspicuous, but may be hidden by granules or superficial scales.
Rods: One of several types of microscopic skeletal ossicles in holothuroids; commonly found as supporting structures in tentacles or tube feet.
Scales: One of several types of skeletal elements in echinoderms; flat, thin structures that are overlapping, tessellate, or haphazardly arrayed.
Sole: In some holothuroids, the flattened ventral part of the body, either covered with or surrounded by tube feet.
Spines: One of several skeletal elements in echinoderms; movable, articulating structures that are long, slender and attenuated.
Teeth: In ophiuroids, small plates or spines attached to the dental plate on the inner edge of the jaw, a series of them extending into the mouth; in echinoids, the five hard, sharp, and movable ossicles incorporated in Aristotle’s lantern; the term also refers to five movable ossicles that surround the anus of some holothuroids.
Tentacle Scales: Small, movable spines or scales, associated with ophiuroid tube feet, which are attached to the ventral arm plate and/or lateral arm plate; may cover the tentacle pores and protect the retracted tube feet.
Tentacles: In holothuroids, feeding structures in the form of highly modified tube feet arranged in a ring around the mouth.
Terminal Disk: Round portion on the end of the tube foot in many echinoderms; usually employed for attachment to substrates.
Tube Feet: Fluid-filled, fingerlike extensions of the water vascular system that protrude through the openings in the skeleton or between skeletal elements; muscles and nerves in the shaft of the tube feet control their movements; glands, and sometimes a muscular sucker, at the tip function in adhesion; specialized tube feet are used for locomotion, feeding, burrowing, respiration, and a combination of functions.
Ventral: In echinoderms, this term is variously applied; in asteroids, echinoids and ophiuroids, it is the surface of the body that carries the mouth; this surface is in contact with the substrate; in holothuroids, with mouth and anus at opposite ends of a cylindrical body, the ventral surface is lowermost, in contact with the substrate; in crinoids, the ventral surface carries the mouth and is functionally the uppermost surface.