Luidia alternata (Say 1825)

US Federal List: no special status

CITES: no special status

Since this species feeds on other seastars, it may be beneficial to shellfish fisheries because it eats other sea stars, some of which eat shellfish. Also, L. alternata is often used for eductional study.

L. alternata usually preys on other echinoderms like brittle stars, but on occasion they consume dead bait thrown overboard by fishermen. Since it is a common inhabitant of scallop beds off the Carolina coast, it usually preys on small individuals of the sea star species Astropecten articulatus. Because their tube feet lack the suckers needed to open bivalves, they swallow their prey whole, then regurgitate the undigestable portions.

Luidia alternata can be found from North Carolina down to Argentina. Although they concentrate on the coasts of Mississippi, Texas, and Mexico, L. alternata are also seen in the Caribbean and off of Florida's coast.

Biogeographic Regions: atlantic ocean (Native )

These sea stars occur in sandy and muddy sediment in 3-50 meters of water.

Aquatic Biomes: benthic

Luida alternata usually reaches 20 cm from arm to arm but some may increase to a diameter of 40 cm. Its dorsal side is white or cream-colored with bands of dark green, purple, black or brown scattered on it. Its ventral surface is yellow with bright orange tube feet. They have five straplike arms fringed with slender spines. They appear fragile with the rows of paxillae irregularly arranged. The paxillae near the arm margins are larger than the midline and they hold a single long, pointed erect spine surrounded by small spinelets.

Other Physical Features: ectothermic

The ovaries of a female are pale salmon and contains egg cells about 1.9 mm in diameter. Female stars release their eggs into the water when they detects the presence of sperm, and vice versa for males. The triggers to begin the process are not known. The eggs that are fertillized develop into a free-swimming bilaterally symmetrical larvae called a bipinnaria. After about a month the 2mm long bipinnaria settles to the bottom and metamorphoses into the radially symmetric adult form.

Luidia alternata (Say)

Asterias alternata Say, 1825:144–145.

Luidia alternata.–Lutken, 1859:42–43; 1871:301.–Verrill. 1867:343.–Perrier, 1876a:254; 1878:34, 91, 96.–Sladen, 1889:250–251, 740.–Ives, 1890:326.–H. L. Clark, 1898a:5; 1919:54, 55, 71; 1933:20, pl. 1.–Doderlein and Hartmeyer, 1910:151.–Doderlein, 1920:241, 267–268, figs. 7, 11.–Caso, 1943:56–57, pl. 16: figs. 1–2, pl. 17: figs. 1–2; 1961:44–47, figs. 11–12.–Engel and Schroevers, 1960:–Ummels, 1963:97–98, pls. 8, 10.–Gray, Downey and Cerame-Vivas, 1968: fig. 6.–Tommasi 1970: pl. 8: fig. 24.

Luidia granulosa Perrier, 1869:109.

Luidia variegata Perrier, 1876b:257.

This species has five arms, and the skeleton is not compact. The paxillae are small, high, and well separated, in regular rows along the side of the arm, irregular and compact in the middle of the arm and disc. The sides of the arms appear higher in this species because the paxillae of the second, third, or fourth row above the inferomarginals bear a stout acute spine. Similar spines may appear on a few other paxillae as well. Paxillae without a central spine have 1–8 central clavate spinules, and all paxillae have numerous subclavate peripheral spinules. The inferomarginal plates bear 2 or 3 long, acute, erect marginal spines, not at all flattened, and below, 2–5 moderately long, somewhat flattened spines; the channels between the inferomarginals are deep and bordered on each side by numerous fine spinules. The adambulacral plates bear a long, fine, curved, laterally flattened furrow spine and 2 or 3 other spines, long, acute, and not flattened. There may be small supplementary spines as well. The very few actinal interradial plates usually bear pedicellariae. The mouth plates are prominent, each plate bearing a double row of short, stout, acute spines. Actinal pedicellariae, stout and three- or four-valved, are usually present. The madreporite is hemispherical, with fine shallow channels.

This is the only nonbrooding starfish showing what I believe to be sexual dimorphism. The female (the specimen from Oregon Station 5894) is much larger, looser of skeleton, and bears many more pedicellariae.

The color in life is distinctive: blotched or banded in creamy white and black or brown. Specimens in this collection came from 0–20 fathoms, from Florida and the Caribbean. The range of the species is from Cape Hatteras to northern South America; it is not known from the western Gulf of Mexico.

MATERIAL EXAMINED.–Oregon Stations: 5894 (1) [R=115 mm, r=7 mm, Rr=1:17]; 1937 (1) [R=44 mm, r=6 mm, Rr=1:6]; 5456 (1) [R=56 mm, r=10 mm, Rr=1:5.6]; 3555 (1) [R=7 mm, r=3 mm, Rr=1:3].