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Two color variations of the brittle star, Amphiodia pulchella. Note five arms radiating out from the central disk in both the left and right specimens. Photo by JE Miller, courtesy of DL Pawson, Smithsonian Institution. Used with permission.

Species Name: Amphiodia pulchella Lyman, 1869
Common Name: Brittlestar
Synonymy: Amphiura pulchella Lyman, 1869
  1. TAXONOMY

    Kingdom Phylum/Division Class: Order: Family: Genus:
    Animalia Echinodermata Ophiuroidea Ophiurida Amphiuridae Amphiodia

    Please refer to the accompanying glossary for definitions of the descriptive terms used in this report.

    Species Description

    Fine scales cover the disk of Amphiodia pulchella, and the pairs of radial shields on the dorsal surface of the disk are closely joined (Hendler et al. 1995). Primary plates are prominent on the disks of smaller specimens, but are usually absent on larger individuals. The middle arm spine is dorsoventrally flattened, with a truncate, echinulate tip. The tips of the other two spines are bluntly rounded. Both distal pairs of oral papillae are elongate with blunt tips, and each of the tube feet have a bulbous tip.

    The color of the disk can vary from gray to brownish gray, with reddish or purplish gray marking the primary plates and other large scales. The radial shields are dark near the center of the disk with a pale distal tip. Reddish brown pigmentation of the stomach may be visible through the body wall. The color of the arms is variable, often pale gray, blotched or having dark gray, brown or reddish brown bands. A dusky internal spot is usually visible on the arm spines, and a light mid-dorsal arm stripe is sometimes evident (Thomas 1962), which is likely from the visibility of the vertebrae through the thin dorsal arm plates (Hendler et al. 1995).

    Potentially Misidentified Species

    In some parts of its range, A. pulchella may be confused with the similar but slightly larger A. atra.  However, A. atra is reportedly absent in southern Florida and the Florida Keys (Hendler et al. 1995). Furthermore, A. pulchella is easily distinguished from A. atra and other shallow-water Amphiodia and Amphipholis species by the presence of only a single tentacle scale.

  2. HABITAT AND DISTRIBUTION

    Habitat & Regional Occurence

    A. pulchella occupies shallow burrows in soft sediments at depths from 1 to 71 m, often in back reef areas along with seagrasses and sponges, or among coral colonies and clumps of algae such as Halimeda (Hendler et al. 1995). Burrowing individuals will frequently extend two to four arms across the sediment surface, while the disk and other arms remain inside the burrow.

    The range of A. pulchella extends along both coasts of Florida, throughout the Florida Keys and Dry Tortugas, throughout the Gulf of Mexico, Cuba, Jamaica, Puerto Rico, the Windward and Leeward Islands of the Lesser Antilles, Tobago, Mexico, Belize, Brazil and Argentina (Hendler et al. 1995).

    IRL Distribution

    The distribution of A. pulchella within the IRL remains undocumented. However, this cryptic species likely occurs in soft sediments and seagrass beds throughout the IRL, especially in the southern lagoon.

  3. LIFE HISTORY AND POPULATION BIOLOGY

    Size

    A. pulchella is one of several species of small brittle stars found in and around the IRL. The diameter of the central disk rarely exceeds 5 mm, and the five slender arms are only 40-50 mm long (Hendler et al. 1995).

    Abundance

    The abundance of A. pulchella in the IRL is not known. However, studies have reported densities elsewhere of up to 100 individuals/L of algae, or 4 individuals/0.22 m2 of sediment (Hendler & Littman 1986, McNulty 1961). These brittle stars can be especially abundant in the poorly oxygenated sediments of Halodule seagrass beds (O’Gower & Wacasey 1967).

    Reproduction & Embryology

    The small oocytes of A. pulchella measure only 0.65 mm in diameter, implying that the developing larvae have low yolk reserves. Therefore, A. pulchella is believed to have a planktonic, feeding larval stage (Hendler & Littman 1986).

  4. PHYSICAL TOLERANCES

    No information is available at this time

  5. COMMUNITY ECOLOGY

    Predators

    A. pulchella has been found in the stomach contents of the nine-armed sea star, Luidia senegalensis (Halpern 1970), and the belted sandfish, Serranus subligarius (Shirley 1982). When disturbed or falling through the water column, this brittle star folds its arms in a zigzag configuration (Hendler et al.1995).

    Associated Species

    A. pulchella has been collected along with several other brittle star species in sand, seagrass beds and mats of filamentous algae at Looe Key, Florida (Hendler et al. 1995).

  6. ADDITIONAL INFORMATION

    No information is available at this time

  7. REFERENCES

    Halpern JA. 1970. Growth rate of the tropical sea star Luidia senegalensis (Lamarck). Bull. Mar. Sci. 20: 626-633.

    Hendler G & BS Littman. 1986. The ploys of sex: relationships among the mode of reproduction, body size and habits of coral reef brittle stars. Coral Reefs 5: 31-42.

    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.

    McNulty JK. 1961. Ecological effects of sewage pollution in Biscayne Bay, Florida: sediments and the distribution of benthic and fouling macro-organisms. Bull. Mar. Sci. Gulf Carib. 11: 394-447.

    O’Gower AK & JW Wacasey. 1967. Animal communities associated the Thalassia, Diplanthera, and sand beds in Biscayne Bay. I. Analysis of communities in relation to water movements. Bull. Mar. Sci. 17: 175-210.

    Shirley TC. 1982. The importance of echinoderms in the diet of fishes of a sublittoral rock reef. In: South Texas Fauna. Chapman BR & JW Tunnell (Eds.). 49-55. Caesar Kleberg Wildlife Research Institute, College of Agriculture, Texas A&I University, Knoxville, Texas.

    Thomas LP. 1962. The shallow water amphiurid brittle stars (Echinodermata, Ophiuroidea) of Florida. Bull. Mar. Sci. Gulf Carib. 12: 623-694.

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