Species Description: The purple-spined sea urchin, Arbacia punctulata, is named for its long slender spines, which are often purple to brown in color. However, spines of some individuals can also vary in color from reddish or reddish gray to almost black (Harvey 1956). The spines are generally the same color as the fused plates of the outer skeleton, or test, and the muscle bases are whitish with several brown to purple spots (Hendler et al. 1995). Tube feet are olive in color and inconspicuous aborally. Stalks of the aboral pedicellariae share the same color as the muscle bases. The oral side of the test is light brown to light purple, with a white peristome area, and silvery white circumoral feet with white terminal disks. The oral primaries are lighter than the aboral primaries, and sometimes appear with white and pink bands.
The area of the apical system is naked, as are the interambulacral areas on the upper surface of the test (Hendler et al. 1995). Four prominent plates cover the periproct. Pore pairs are arranged in a vertical series, and the interambulacral tubercles are equal in size. While most urchins possess both long primary and short secondary spines, A. punctulata possesses only the long type (Ruppert & Barnes 1994).
Habitat & Regional Occurrence: A. punculata occurs in beds of the turtle grass, Thalassia testudinum, under coral rubble, and on rock, sandy or shelly bottoms (Hendler et al. 1995). Most individuals reside in shallow waters less than 50 m deep, although A. punctulata has been found down to 225 m (Serafy 1979).
The range of A. punctulata extends from Maine to Cuba, the Yucatán Peninsula, Florida to Texas in the Gulf of Mexico, Panama to French Guiana and north to Barbados (Serafy 1979, Kaplan 1988).
IRL Distribution: The distribution of A. punctulata in the IRL is undocumented. However, they tend to be concentrated around rock jetties and other hard structures near inlets (Ruppert & Fox 1988; LH Sweat, personal observation).
Size: A. punctulata reaches a total diameter, including spines, of about 100 mm. The test alone reaches a diameter of about 50 mm (Hendler et al. 1995).
The sex ratio of A. punctulata has been reported to be 1.03 males to every female (Shapiro 1935). Detailed abundance data remain unreported for the IRL, but both solitary individuals and aggregated urchins can be found in the lagoon.
Reproduction & Embryology:
Shapiro (1935) reported an incidence of hermaphrodism in 1 of every 2,350 A. punctulata. The reproductive season of this urchin is long in the warm waters of Florida, but discrete spawns are more evident in spring and summer near the northern part of its range (Harvey 1956, Serafy 1979). A. pulchella is a popular species for biological research, especially embryological and larval studies.
Agassiz A. 1873. Revision of the Echini. Illustrated Catalogue of the Museum of Comparative Zoology at Harvard College. University Press. Cambridge, MA.
Bell SS & JB McClintock. 1982. Invertebrates associated with echinoderms from the west coast of Florida with special reference to herpactacoid copepods. In: Lawrence JM (Ed.). 165-171. Echinoderms: Proceedings of the International Conference. Tampa Bay, 14-17 September 1981. Balkema, Rotterdam.
Fell PE, Parry EH & AM Balsamo. 1984. The life histories of sponges in the Mystic and Thames Estuaries (Connecticut), with emphasis on larval settlement and postlarval reproduction. J. Exp. Mar. Biol. Ecol. 78: 127-141.
Harvey EB. 1956. The American Arbacia and Other Sea Urchins. Princeton University Press. Princeton, New Jersey. xiv + 298 pp. 16 pls.
Hay ME, Lee Jr. RR, Guieb RA & MM Bennett. 1986. Food preference and chemotaxis in the sea urchin Arbacia punctulata (Lamarck) Philippi. J. Exp. Mar. Biol. Ecol. 96: 147-153.
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.
Kaplan EH. 1988. A field guide to southeastern and Caribbean seashores: Cape Hatteras to the Gulf coast, Florida, and the Caribbean. Houghton Mifflin Co. Boston, MA. USA. 425 pp.
Renaud PE, Hay ME & TM Schmitt. 1990. Interactions of plant stress and herbivory: Intraspecific variation in the susceptibility of a palatable versus an unpalatable seaweed to sea urchin grazing. Oecologia (Berlin) 82: 217-226.
Ruppert EE & RD Barnes. 1994. Invertebrate zoology, 6th edition. Saunders College Publishing. Orlando, FL. USA. 1056 pp.
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. 1979. Echinoids (Echinodermata: Echinoidea). Memoirs of the Hourglass Cruises 5: 1-120.
Shapiro H. 1935. A case of functional hermaphrodism in the sea urchin, Arbacia punctulata, and an estimate of the sex ratio. Amer. Nat. 69: 286-288.
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.