title used in learnabout sections of A SNAIL'S ODYSSEY
  Foods & feeding
   
  black dot
  Deposit-feeding
 

Examples of studies dealing with deposit-feeding are presented here, while ones on SUSPENSION-FEEDING and ABSORPTION OF DOM are considered elsewhere.

 
Research study 1
 

Spionids inhabit tubes in sediments where they feed on organic matter in the surface layers.  An alternate feeding mode is facultative suspension-feeding.  This type of feeding involves extending the 2 large anterior tentacles, arrayed in a novel helical pattern, into the water flow.  The helical shape increases the surface area of the tentacles normal to the flow.  Studies at Friday Harbor Laboratories, Washington show that the spionid Polydora kempi japonica will switch from a deposit-feeding mode to a suspension-feeding mode in response to concentration of suspended particulate matter in the water.  By using their tentacles in this manner the worms can capture particles as large as newly hatched brine shrimp, as photograph of a spionid worm Polydora kempi japonica extending its tentacles in a unique helical shape for suspension-feeding well as smaller flocculent material.  By narcotising worms with MgCl2 and implanting them in the sediment along with normal control worms, the authors show that the helical form of the tentacles is controlled by the worms and is not a passive response to water flow.  Taghon et al. 1980 Science 210: 562.

NOTE  the Family Spionidae includes about 40 west-coast species, of which about half are in the genus Polydora

The original photograph in the authors' has poor contrast (see photo on Left), but a better one for the related Pseudopolydora paucibranchiata is shown on the Right 4X

This photo clearly shows the
helical shape of tentacles of
P. paucibranchiata
. The tentacles
appear to have food particles
attached. Photo courtesy
Jeff Shimeta, Melbourne,
Australia

 
  RETURN TO TOP