Smithsonian Marine Station at Fort Pierce

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The brittle star, Amphioplus thrombodes. Photo by JE Miller, courtesy of DL Pawson, Smithsonian Institution. Used with permission.

Species Name: Amphioplus thrombodes
Common Name: Brittlestar
Synonymy:
  1. TAXONOMY

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

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

    Species Description

    Amphioplus thrombodes is one of several small brittle stars occurring in the Indian River Lagoon. The bumps on the edge of the dorsal scales give the disk a rough, papillate texture (Thomas 1962, Hendler et al. 1995). The five arms have three spines each. The middle spine is thickest and slightly compressed. The disk is pale gray and speckled with brownish scales. The radial shields are joined distally, are tipped in white, and are twice as long as they are wide (Thomas 1962). The arms are pale tan and blotched with dark gray (Hendler et al. 1995).

    Potentially Misidentified Species

    A. thrombodes resembles A. sepultus, except for the presence of bumps on the edge of the dorsal scales in the former species (Hendler et al. 1995). A. thrombodes also exhibits only a single pair of tentacle scales on most arm joints, and a narrower tip on the middle arm spine.

  2. HABITAT AND DISTRIBUTION

    Habitat & Regional Occurence

    A. thrombodes inhabits muddy sand in shallow waters 0.3 to 0.6 m deep. Individuals are often seen burrowing in beds of the seagrass, Halodule wrightii (Hendler et al. 1995). The range of A. thrombodes extends along the Gulf Coast of Florida, and from Fort Pierce southward along Florida's east coast.

    IRL Distribution

    This brittle star is found from Fort Pierce to the southern tip of the IRL.

  3. LIFE HISTORY AND POPULATION BIOLOGY

    Size

    The disk diameter of A. thrombodes is approximately 5 mm, with arms 60 mm long (Hendler et al. 1995).

    Abundance

    The sex ratio in populations of A. thrombodes at Cedar Key, Florida has been documented as 1 male to every 0.79 females (Stancyk 1970).

  4. PHYSICAL TOLERANCES

    No information is available at this time

  5. COMMUNITY ECOLOGY

    Associated Species

    A. thrombodes has been collected with other burrowing brittle stars such as A. sepultus (Hendler et al. 1995).

  6. ADDITIONAL INFORMATION

    No information is available at this time

  7. REFERENCES

    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.

    Stancyk SE. 1970. Studies on the biology and ecology of ophiuroids at Cedar Key, Florida. Unpublished MS thesis. University of Florida, Gainesville.

    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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Page last updated: 31 October 2012

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