Species Description: The rock boring urchin, Echinometra lucunter, has an elongate oval test with two rows of large tubercles along the ambulacra and interambulacra, pairs of pores arranged in arcs of six, and a large peristome (Hendler et al. 1995). The spines are long and slender, thickened at the base, and sharply pointed at the tips.
On the aboral side, the primary and secondary spines are dark olive green, with greenish violet to purple tips (Hendler et al. 1995). The general color of the spines is blackish, although some specimens may exhibit a reddish color. Test and muscle bases of the spines are shades of red-brown. Tube feet on the aboral surface are light brown, and the terminal disks are dark brown to blackish. Oral spines have a lighter color than aboral ones, light olive green with a violet gradient near the tips. The test and peristome are flecked with creamy brown. The tube feet near the mouth are translucent, with terminal disks that are creamy white in color, lined with a narrow dark brown band, and measuring about twice the size of those on the aboral feet.
As with many intertidal organisms, studies have revealed differences in the structure of E. lucunter from environments with varying wave action. Specimens from high-energy areas tend to have tests that are flatter, thicker, smaller, and narrower, and a distinctive pattern of insertion of ocular plates in the apical system (Lewis & Storey 1984).
Potentially Misidentified Species: The general shape and size of E. lucunter is similar to that of the reef urchin, E. viridis. However, the latter usually has a more circular test shape and longer spines, a reddish test, pore pairs in arcs of five instead of six, and conspicuously white milled rings around the base of each spine (Hendler et al. 1995).
Habitat & Regional Occurrence: The rock-boring urchin is commonly found on limestone reef rock in the surf zone (Hendler et al. 1995). It can be very common in shallow, exposed fore reef or reef crest habitats, occupying shallow depressions or burrows created by the abrading action of the urchin’s spines and teeth on the rock surface. The success of E. lucunter in harsh environments may be partially due to its apparent resistance to stresses caused by increased temperature and salinity (Hendler 1977).
The range of E. lucunter extends from Beaufort, North Carolina and Bermuda southward throughout the Caribbean and eastern Central America to Desterra, Brazil. Populations can also be found in West Africa. The subspecies E. lucunter polypora Pawson is common at Ascension and St. Helena Islands (Pawson 1978). The depth range for this species is generally zero to 45 meters (Serafy 1979).
Indian River Lagoon Distribution: The distribution of E. lucunter within the IRL remains undocumented. However, this species appears to be concentrated mostly around rock jetties and other hard structures near inlets (LH Sweat, personal observation).
Size: E. lucunter reaches a maximum size of 15 cm, though most individuals are about half that size (Hendler et al. 1995).
Abundance: The abundance of E. lucunter in the IRL is undocumented. However, studies have reported densities elsewhere of up to 129 individuals per square meter (Greenstein 1993).
Reproduction & Embryology: The annual spawning cycle for the rock-boring urchin has been reported to occur in late summer in the Florida Keys (McPherson 1969), peaks in the fall in Puerto Rico (Cameron 1986), and occurs variably throughout the year in Panama (Lessios 1981). Lewis & Storey (1984) documented one spawning event per year in urchins from high-energy environments, and two events annually in urchins from low-energy areas. Tennent et al. (1931) reported that spawning in one individual takes about 15 minutes. Fertilization and development are adversely affected by reducing salinity (Petersen & Almeida 1976). Larvae of this species have been reared through metamorphosis in the laboratory (e.g. Mortensen 1921).
Trophic Mode: The rock-boring urchin feeds mostly at night from their burrows, consuming clumps of drift algae, or venturing out of the burrow to feed and then usually returning to the same hole (McPherson 1969, Abbott et al. 1974, Ogden 1976). In Panama, individuals were observed to clear the area around their burrows of all organisms except calcareous algae (Hendler et al. 1995).
Movement & Behavior: Antagonistic behaviors among conspecifics have been observed for this urchin. Grunbaum et al. (1978) found that intruding urchins were pushed and bitten by the individual originally inhabiting the burrow, and that the inhabitant won most altercations. Escape responses have been observed in individuals following exposure to chemical extracts from other Echinometra spp. (Parker & Shulman 1986).
Predators: Predators of E. lucunter include: ruddy turnstones, Arenaria interpres; conchs; and fish including triggerfish, grunts, jacks and wrasses (Abbott et al. 1974). Predation by the reticulate cowrie-helmet, Cypraecassis testiculus, has also been documented for individuals in Panama (Hendler 1977).
Parasites & Associated Species:: The eulimid gastropod, Monogamus minibulla is a parasite of the rock-boring urchin (Warén & Moolenbeek 1989). The turbellarian, Syndisyrinx collongistyla, has been reported to infest the intestines of E. lucunter in Jamaica, S. evelinae has been found in specimens from St. Barthélemy (Hertel et al. 1990). Protozoans have also been reported to infest E. lucunter (Mortensen 1943). The rock-boring urchin has been observed to share its burrow with several associates, including a goby, a porcelain crab, and a brittle star (Schoppe 1991).
Ecological Significance: The burrowing behavior of E. lucunter can contribute greatly to the breakdown of coral reefs and intertidal limestone shorelines, especially when urchin population densities are high. Hoskin & Reed (1985) estimated that burrows are excavated in approximately 3 years. Rates of erosion on coral reefs due to this excavation have been reported at 3.9 kg per square meter annually in the Virgin Islands, 7.0 kg per square meter annually in Bermuda, and 24 g per urchin per year in Barbados (Ogden 1977).
Ablanedo et al. (1990) found that individuals of E. lucunter accumulate certain heavy metals in the gonads, test, spines, and lantern. Therefore, they can be used as an indicator species to reflect the level of environmental pollution to which they are exposed.
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Ablanedo N, Gonzalez H, Ramirez M & I Torres. 1990. Evaluación del erizo de mar Echinometra lucunter como indictor de contaminación por metales pesados, Cuba. Aquat. Living Res. 3: 113-120.
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Warén A & R Moolenbeek. 1989. A new eulimid gastropod, Trochostilifer eucidaricola, parasitic on the pencil urchin Eucidaris tribuloides from the southern Caribbean. Proc. Biol. Soc. Wash. 102: 169-175.