Back to Completed Reports List

Amphioplus thrombodes

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

SPECIES NAME: 
Amphioplus thrombodes HL Clark 1918

COMMON NAME:
Brittlestar

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.

II.  HABITAT & 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.

INDIAN RIVER LAGOON DISTRIBUTION:
This brittle star is found from Fort Pierce to the southern tip of the IRL.

III. LIFE HISTORY & 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).

IV. COMMUNITY ECOLOGY

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

V. 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 Unpublished MS thesis.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.

Page by LH Sweat

For questions, comments or contributions, please contact us at:
irl_webmaster@si.edu
Page last updated: 31 October 2012