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You are here:   OldClasses > 2012 > Alloeocomatella pectinifera | Shuting Jin

 

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Alloeocomatella pectinifera

(Clark 1911)

Red Feather Star

Shuting Jin (2012)

 

Fact Sheet

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Summary


Physical Description


Ecology


Local Distribution and Habitats


Commensalisms


Life History & Behaviour


Reproduction


Feeding


Cyclicity


Anatomy and Physiology


External Anatomy


Internal Anatomy


Physiology


Evolution & Systematics


Fossil Record


Phylogeny


Biogeographic Distribution


Conservation


Status


Threats


Resources


References


Acknowledgements


Contact

External Anatomy


Brief Summary

Key external features of feather stars:
  • Bilateral symmetry as larvae and pentameral (five-sided) symmetry as an adult.
  • Motile arms used for suspension feeding and locomotion.
  • A calcareous endoskeleton of bony ossicles embedded in the body wall.
  • Both mouth and anus located on the dorsal side.

​Symmetry


The pentaradial symmetry of A. pectinifera can be readily seen in the positioning of its ten arms, which radiate in pairs from five radial ossicles (Fig. 6). A. pectinifera also exhibits a secondary bilateralism, with the arms arising from the edge closest to the mouth significantly longer than the opposing arms. The bilaterally symmetrical larvae of feather stars are shaped like short, rounded cylinders encircled by four bands of cilia. One end is blunt, and one is rounded and embedded with a tuft of sensory cilia (Ruppert et al.2004).




Fig. 6. Detailed aboral view of Alloeocomatella pectinifera showing bases of arms emerging in pairs from radial segments and robust, curved cirri. Creative Commons License This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License

 

​Cirri

Highly ossified cirri on the aboral side are used by A. pectinifera to cling to the substrate. Cirri tend to be long and slender on animals living on soft substrates and more robust and curved on animals living on or in hard substrates (Ruppert et al. 2004). The specimen in Fig. 6 was found partially hidden in a crevice, clinging to the hard coral rubble and has correspondingly strong, curved cirri.


​Arms and Pinnules

The arms radiate out from the center of the body and are covered in numerous, pinnately arranged short appendages called pinnules (Ruppert et al. 2004), see Fig. 2. Ambulacral grooves run down the middle of the oral surface of the arms and bifurcate to extend down the middle of each pinnule (Ruppert et al. 2004). The ambulacral grooves house the tube feet, which function in suspension feeding in crinoids (Ruppert et al. 2004). In crinoids the arms function in both suspension feeding and locomotion. In Comasteridae, the oral pinnules, those pinnules nearest the central disk, bear comb-like structures on the outer segments (Clark 1911Messing 1995). 

Body
 
The body is covered by an epidermis over a connective tissue layer embedded with ossicles. These ossicles (small bones) act as a skeleton, stiffening the animal. The ossicles in the cirri, arms, and pinnules are very robust and resemble vertebrae, but, especially in the arms and pinnules, are joined in such a way that allows some mobility (Ruppert et al. 2004).

A calcified cup called the calyx supports the main portion of the body on the oral side and the centrodorsal, where the cirri connect, on the aboral side. The portion of the body supported by the calyx on the oral side consists of the viscera covered by a fleshy membrane called the tegmen. The openings to the mouth and anus are located here, with the anal opening usually located in the center, on top of a slightly raised portion of the central disk (Fig. 2, reproduced below for ease of reference).



Fig. 2. False color visual atlas of Alloeocomatella pectinifera showing oral (A) and aboral (B) sides. A) The theca is the central body portion of a feather star. The fleshy central disk on the oral side is shown in royal blue. It is surrounded by numerous oral pinnules (pale yellow). The oral opening (purple) is near the margin of the central disk, and the anal papilla is a small protrusion in the middle of the central disk (orange). The unbroken arms near the oral opening of this specimen are called the anterior arms and are noticeably longer than the posterior arms on the other side. B) The calyx is shown in pink. The centrodorsal plate (green) is surrounded by several cirri (yellow). The arms (sky blue) bear numerous pinnules (red). Creative Commons License This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License


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