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  Predators & defenses
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Escape by crawling

  Defenses of asteroids include escape by crawling, considered here, and SPINES & OSSICLES, PEDICELLARIAE, DISTASTEFUL CHEMICALS, MUCUS, AUTOTOMY, and CAMOUFLAGE, considered in other sections. 
Research study 1

photograph of sea star Luidia foliata showing tube feet

The sea star Luidia foliata commonly inhabits sand/mud habitats over which it can crawl quite quickly, possibly owing to the lack of suckers on the tube feet. Thus, it moves tippy-toe fashion. Interestingly, its diet includes a range of invertebrates, including bivalves, but how it catches and manipulates its prey without suckers is not known.






Research study 2

photograph of sun star Solaster dawsonii vigorously pursuing a large sunflower star Pycnopodia helianthoidesSubtidally, the most aggressive predator of west-coast sea stars is the sun star Solaster dawsoni.  Responses of prospective prey species as observed at Friday Harbor Laboratories, Washington is to crawl away, and the ones listed below are mostly capable of out-running the predator:

Crossaster papposus
Dermasterias imbricata
Evasterias troschelii
Mediaster aequalis
Pycnopodia helianthoides

One species, Solaster stimpsoni even pushes back against the predator when attacked.  A similar pushing defense is also photograph of a leather star Dermasterias imbricata being digested by a sun star Solaster dawsoniiused by S. stimpsoni to repel attacks by conspecifics.  Mauzey et al. 1968 Ecology 49: 603.



This leather star Dermasterias
was unable to outrun its predatorSolaster dawsoni 0.7X



A sunflower star Pycnopodia helianthoides
successfully escapes from a pursuing sun star
Solaster dawsoni
by fast crawling

Research study 3

Subtidal measurements of Solaster dawsoni’s locomotory rate show a top chase speed of about 10cm . min-1. Interestingly, when touched by one of Solaster’s rays, even some sluggish-seeming species can outrun the predator.  At crawling speeds of 120-160cm . min-1 the sunflower star photograph of sunflower star Pycnopodia helianthoides crawling quicklyPycnopodia helianthoides is, of course, in a class by itself, but even the normally quiescent Mediaster aequalis (33cm . min-1) and Crossaster papposus (65cm . min-1) easily outrun the predator.  Of asteroids whose crawling speeds are recorded, the bat star Patiria miniata may be one of the slowest, at 6cm . min-1.  It does not appear to be eaten by Solaster, however, perhaps for reasons of distastefulness or by living in habitats not frequented by the predator. Data mostly from Mauzey et al. 1968 Ecology 49: 603; Kjerschow-Agersborg 1922 Biol Bull 42: 202 (for Pycnopodia); Rumrill 1989 Mar Ecol Progr Ser 56: 37 (for Patiria).

NOTE  locomotory rates are for adult-sized individuals for all sea stars save Pycnopodia and Patiria, which are about half maximum size (46 and 5cm diameter, respectively)

This large sunflower star Pycnopodia helianthoides is
photographed crawling directly towards the camera.
Within a few moments it transit completely over the
camera and the SCUBA diver, and departs on the other side

Research study 4

Much the same kind of data for behavioural responses of asteroids to contact with Solaster dawsoni are presented in a study at the Bodega Marine Laboratory, California.  Here, strong escape responses are displayed by Patiria miniata, Henricia leviuscula, Leptasterias hexactis, Pycnopodia helianthoides, and small Pisaster ochraceus.  However, all the slow-moving species are subsequently captured and eaten.  Only P. helianthoides crawls quickly enough to escape.  Although large-sized Pisaster ochraceus can defend itself from the predator with its pedicellariae, small-sized individuals, as noted, are photograph of a sun star Solaster dawsonii and a half-eaten leather star Dermasterias imbricatagenerally eaten.  Of 7 species tested, only the leather star Dermasterias imbricata is immune to predation.  The authors use the presence or absence of an escape response to predict whether a species is susceptible to predation from SolasterVan Veldhuizen & Oakes 1981 Oecologia 48: 214. Photograph courtesy Brooke Reiswig and Dave Cowles, Walla Walla University, Washington

NOTE  in this study an attacking Solaster dawsoni of 6.5cm radius can reach crawling speeds of 12cm . min-1

NOTE  the authors note that D. imbricata has a pungent odour and the possibility of toxic substances in the skin has been reported

Extra-hungry and just less discriminating than
usual? A sun star Solaster dawsoni with its half-
digested meal of leather star Dermasterias imbricata