title for sandworms & relatives section of A SNAIL'S ODYSSEY
  Predators & defenses
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photograph of scaleworm Arctonoe fragilis crawling amongst the spines and pedicellariae of a sea-star's arm Orthasterias koehleriMost free-living polychaetes rely on a cryptic habit of life for protection from predators, living under rocks, among mussels, or in their tubes during the day, and coming out to feed mostlly at night.  Large jaws are possessed by some species, thought to be used in defense and/or in resolving territorial disputes.

A scaleworm Arctonoe fragilis crawls among the pedicellariae
of a sea star Orthasterias koehleri. Note that all the
pedicellariae are quiescent. This raises the question as to
what stops the worm from being bitten by its host's
pedicellariae? Or is the relationship some type of mutualism? 3X

drawing of anterior end of a nereid polychaete showing proboscis and jaws




Sandworms Nereis spp. have large pincer-
type jaws that they employ in territorial
disputes and in defense from predators

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Research study 1
 

A nereid polychaete being attacked by nemertean Paranemertes peregrina, photograph courtesy Rebecca Kordas, Biodiversity Research Centre, UBC, VancouverOf 2 common species of sandworms eaten by predatory nemerteans, Nereis vexillosa seems much the tougher prey than Patynereis bicanaliculata.  When being wrapped up by the proboscis of the nemertean Paranemertes peregrina, for example, Nereis bites aggressively with its jaws, flips its hind end and crawls or, in extreme instances, swims away from danger.  Other non-polychaete-eating nemerteans, including Emplectonema gracile, elicit no swimming response in nereid polychaetes.  Roe 1970 Biol Bull 139: 80.

 

 

 

 

Polychaete Nereis vexillosa being attacked by a nemertean
Paranemertes peregrina
. This species of nemertean is
commonly active during periods of low tide, which might
explain why the polychaete does not appear to be protecting
itself...i.e., it is out of water.. In fact, the encounter ends with
the nemertean giving up the attack and wandering away. Photograph
courtesy Rebecca Kordas, Biodiversity Research Centre, UBC, Vancouver.

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Research study 2
  Examination of regurgitated “morning pellets”, chick regurgitations, and reference to literature data on stomach contents of 3 species of pelagic cormorants in localities ranging from Alaska to Baja California discloses only a small dietary reliance on sandworms. For example, less than 1% of 9519 prey items from cormorants in the Farallon Islands, California and 7% of 15 prey items from cormorants in Kodiak Island, California are polychaetes, most likely sandworms Nereis spp..  Ainley et al. 1981 The Condor 83: 120.
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Research study 3
 

drawing of sculpin Oligocottus armatusPredators of adult sandworms include fishes, birds, crabs, and nemerteans, just to name a few.   Studies in Grays Harbor, Washington show that summer diets of staghorn sculpins Leptocottus armatus have a large component of sand worms Nereis brandti, representing about 30% of the fishes' diets based on Index of Relative Importance. Armstrong et al. 1995 Fish Bull 93: 456.

NOTE  this index takes into account both number and size of prey consumed

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