title for sandworms & relatives section of A SNAIL'S ODYSSEY
  Predators & defenses
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Research study 1
 

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 seems well camouflaged as it crawls
among the pedicellariae of its host 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?
Could the relationship be some type of mutualism rather than parasitism? 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 2
 

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. Photograph
courtesy Rebecca Kordas, Biodiversity Research Centre, UBC, Vancouver.

 

 

 

 

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

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Research study 3
  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, Alaska are polychaetes, most likely sandworms Nereis spp.  Ainley et al. 1981 The Condor 83: 120.
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Research study 4
 

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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Research study 5
 

The photo series below, taken from a video, shows a sandworm Nereis sp. (or Neanthes sp.) in a California tidepool being captured and eaten by hermit crabs Pagurus sp. The action depicted here takes 8.5 sec. The initial withdrawal of the worm at Time 2.5sec is mediated by chemotactile stimulation of sensory appendages (antennae, palps, cirri) on the worm's head. The question arises as to whether the worm's response is an innate one to some type of chemical emanation from the crab's antenna, and this leads to a corollory question, whether the worm has remembered a similar previous contact and has responded accordingly. For invertebrates such as molluscs and seastars, such a memory capability is well known, but whether it exists in a polychaete worm has not yet been determined. Originial video courtesy Mila Zinkova, Fitzgerald Marine Reserve, Moss Beach, California.

 
photograph 1 in a series of 12  taken from a video showing a sandworm Nereis sp. (or Neanthes sp.) being captured and eaten by hermit crabs Pagurus sp. photograph 1 in a series of 12  taken from a video showing a sandworm Nereis sp. (or Neanthes sp.) being captured and eaten by hermit crabs Pagurus sp. photograph 1 in a series of 12  taken from a video showing a sandworm Nereis sp. (or Neanthes sp.) being captured and eaten by hermit crabs Pagurus sp.
Time 0sec: a sandworm emerges from rock crevice Time 2sec: the worm touches the antenna of a hermit crab Time 2.5sec: the worm recoils and twists violently
photograph 1 in a series of 12  taken from a video showing a sandworm Nereis sp. (or Neanthes sp.) being captured and eaten by hermit crabs Pagurus sp. photograph 1 in a series of 12  taken from a video showing a sandworm Nereis sp. (or Neanthes sp.) being captured and eaten by hermit crabs Pagurus sp. photograph 1 in a series of 12  taken from a video showing a sandworm Nereis sp. (or Neanthes sp.) being captured and eaten by hermit crabs Pagurus sp.
Time 3sec: the worm twists away and touches the extended leg of a second hermit crab Time 3.5sec: this second hermit crab immediately grabs at the worm with its right chela Time 4sec: while being pulled inwards to the crab the worm escapes
photograph 1 in a series of 12  taken from a video showing a sandworm Nereis sp. (or Neanthes sp.) being captured and eaten by hermit crabs Pagurus sp. photograph 1 in a series of 12  taken from a video showing a sandworm Nereis sp. (or Neanthes sp.) being captured and eaten by hermit crabs Pagurus sp. photograph 1 in a series of 12  taken from a video showing a sandworm Nereis sp. (or Neanthes sp.) being captured and eaten by hermit crabs Pagurus sp.
Time 4.5sec: the worm touches the leg of a third crab ( leg is near the shell, not the longer piece of spotted debris) Time 5.5sec: this third hermit crab immediately investigates the disturbance, and extends another leg Time 7sec: meanwhile, the second hermit crab lunges some distance out of its shell and again grabs the worm
photograph 1 in a series of 12  taken from a video showing a sandworm Nereis sp. (or Neanthes sp.) being captured and eaten by hermit crabs Pagurus sp. photograph 1 in a series of 12  taken from a video showing a sandworm Nereis sp. (or Neanthes sp.) being captured and eaten by hermit crabs Pagurus sp. photograph 1 in a series of 12  taken from a video showing a sandworm Nereis sp. (or Neanthes sp.) being captured and eaten by hermit crabs Pagurus sp.
Time 7.5sec: the worm is grappled closer by the second crab's chelae and maxillipeds. The third crab investigates Time 8sec: the third crab quickly closes in on the activity, opposing its shell aperture to that of the second crab Time 8.5sec: the worm is now being attacked and likely consumed by both hermit crabs simultaneously
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