Access

You are not currently logged in.

Access your personal account or get JSTOR access through your library or other institution:

login

Log in to your personal account or through your institution.

Particle Retention and Flow in the Pharynx of the Enteropneust Worm Harrimania planktophilus: The Filter-Feeding Pharynx May Have Evolved before the Chordates

Christopher B. Cameron
Biological Bulletin
Vol. 202, No. 2 (Apr., 2002), pp. 192-200
DOI: 10.2307/1543655
Stable URL: http://www.jstor.org/stable/1543655
Page Count: 9
  • Subscribe ($19.50)
  • Cite this Item
Particle Retention and Flow in the Pharynx of the Enteropneust Worm Harrimania planktophilus: The Filter-Feeding Pharynx May Have Evolved before the Chordates
Preview not available

Abstract

An investigation of the feeding behavior of the acorn worm Harrimania planktophilus suggests a novel form of enteropneust feeding with significant phylogenetic implications. H. planktophilus is a holoinfaunal worm that feeds on deposited sediments, and filter feeds on suspended particles in interstitial pore water. To visualize the particle retention behavior involved in filter feeding, adult animals were held in chilled seawater under low light and fed food coloring and fluorescent particles. The behavior was recorded by videography. Most particles ingested were drawn into the mouth by an incurrent flow created by cilia on the pharyngeal bars and without the aid of mucus. Particles that passed freely through the gill pores averaged 3.04 μm, whereas particles retained in the gut and defecated in the feces averaged 13.9 μm. Food coloring entered the mouth and was pumped through the pharynx at a rate of 0.5-2.0 mm/s. There is no evidence of an endostyle or mucus-net capture mechanism in H. planktophilus, but instead particles are filtered and manipulated by a dense covering of cilia on the pharyngeal gill bars. This study suggests that the filter-feeding pharynx is not an innovation of the chordates, but evolved prior to the evolutionary divergence of the hemichordate-echinoderm clade from the chordates.

Page Thumbnails

  • Thumbnail: Page 
192
    192
  • Thumbnail: Page 
193
    193
  • Thumbnail: Page 
194
    194
  • Thumbnail: Page 
195
    195
  • Thumbnail: Page 
196
    196
  • Thumbnail: Page 
197
    197
  • Thumbnail: Page 
198
    198
  • Thumbnail: Page 
199
    199
  • Thumbnail: Page 
200
    200