Defenses & predators
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  Swimming
  Defenses of swimming will be considered in this section, while THICK BODY WALL/SKIN OSSICLES, WITHDRAWAL INTO CREVICES/"CATCH" CONNECTIVE TISSUES, EVISCERATION & REGENERATION, TOXIC CHEMICALS/UNPALATABILITY, SEA-STAR PREDATORS and SEA-OTTER PREDATORS will be considered in other sections.
 
Research study 1
 

photograph of a sea cucumber Parastichopus californicus rearing up in preparation for swimming
photograph of a sea cucumber Parastichopus californicus rearing up in preparation for swimming When stimulated by a predator, such as the sunflower star Pycnopodia helianthoides, sea cucumbers Parastichopus californicus are able to swim away.  Initially, the front of the body rises, followed by waves of contraction of circular muscles in the body wall proceeding from back to front.  The waves are cyclic, each lasting about 15-18sec, and continue for 7-8 cycles before diminishing.  At this time, 5 pairs of longitudinal muscle bands located on the inner side of the body wall contract on alternate sides.   The end result is a slow but strong side-to-side thrashing that carries the animal upwards and away from danger.   The action appears clumsy, but is strong and remarkably effective.  Margolin 1976 Ophelia 15: 105.

A Parastichopus californicus rises up from contact with a
sunflower star Pycnopodia helianthoides, preparatory to swimming.
The individual on the Left has retracted the tentacles around its
mouth fully and the mouth is just visible, while the one on the
Right has only partly retracted its tentacles

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photograph of a sea cucumber Parastichopus californicus preparing to swim from a sunflower star Pycnopodia helianthoides taken from a video

CLICK HERE to see a video of Parastichopus californicus swimming from a predatory sea star Pycnopodia helianthoides. The activity is not very vigorous, but the escape potential is obvious.

NOTE  the video replays automatically

 
Research study 2
 

table of % swimming of sea cucumbers Parastichopus californicus from 16 species of west-coast sea-star speciesTests at Friday Harbor Laboratories, Washington on frequency of swimming after contact with different species of sea stars show that Parastichopus californicus swims immediately, or almost immediately, on contact with only 3 species: Pycnopodia helianthoides (100%), Solaster stimpsoni (89%), and Solaster dawsoni (91%). Three other species induce graded responses (body contraction, crawling) in Parastichopus leading in about half the cases to swimming (see Table). Ten other species induce graded responses in Parastichopus, but do not lead to swimming. As positive results are obtained from sea-star species in 3 Orders of Asteroidea and over a broad range of dietary preferences (including strong responses from Solaster dawsoni, a strict predator of other sea stars) neither taxonomic nor dietary affinities are evident. The author notes that there is no evidence of actual predation by any sea-star species on the sea cucumber.  Margolin 1976 Ophelia 15: 105.

NOTE  the author uses 100 individual sea stars in each set of tests

NOTE  this topic is considered elsewhere in the ODYSSEY: LEARN ABOUT SEA ANEMONES: PREDATORS & DEFENSES

 

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