Many thousands of times I have seen shells and pebbles stuck to sea urchins, but it is the tube feet that pick up the shells and pebbles, because the tube feet have a tiny sucker at the end. And Steve said often the wentletraps he saw were stuck in the aperture-up position. Logic dictates it was the tube feet that they were stuck to, not the spines.
> On Aug 8, 2019, at 6:54 PM, Harry Lee <[log in to unmask]> wrote:
>
> Amazing how Susan knew this; did I miss something?
>
> Harry
>
>
> On 8/8/2019 9:32 AM, steve rosenthal wrote:
>> correct, thank you!
>>
>> On 8/8/19, Susan Hewitt or Ed Subitzky <[log in to unmask]> wrote:
>>> A small point, but it is the tube feet of the sea urchins that the shells
>>> are stuck to, not the spines.
>>>
>>>> On Aug 7, 2019, at 5:09 PM, Steve Rosenthal <[log in to unmask]> wrote:
>>>>
>>>> It is well known that wentletraps (Epitoniidae) are associated
>>>> ecologically and distributionally with sea anemones. Does anybody know if
>>>> there is any association between sea urchins and wentletraps?
>>>>
>>>> While collecting shells over the weekend in SE Alaska I stumbled upon a
>>>> population of Boreoscala greenlandica (Perry, 1811) in spatial
>>>> association with bunches of green sea urchins (Strongylocentrotus
>>>> drobachiensis) in the lowermost intertidal/uppermost subtidal zone of the
>>>> rocky shoreline. Of the 100 or so live snails I saw, at least half were
>>>> actually 'stuck' on the spines of the sea urchins with their
>>>> apertures/opercula facing upwards. Almost all the other wentletraps I
>>>> saw were nearby on sediment or hard surfaces adjacent to (and often in
>>>> contact with) the urchins, while a few were crawling around in, or
>>>> partially buried in, bare patches of soft sediment nearby. I didn't see
>>>> any of the snails in any other microhabitat or bottom type in the areas I
>>>> explored. Furthermore, I didn't notice any sea anemones in the areas
>>>> where the urchins and the wentletraps were living. I can't help but
>>>> wonder if there is an ecological association between these two species,
>>>> and then of course how did so many living wentletraps wind up 'stuck' on
>>>> the sea urchins, and what- if any- harm (or benefit) could result for the
>>>> snails as a consequence. It's well known that many species of sea urchins
>>>> will attach dead shells (especially bivalves), pebbles and other debris to
>>>> their spines to help disguise them from potential predators. Do they also
>>>> 'use' live shells? It sure looked like it.
>>>> Another thing i did notice was the first low tide of that weekend (a
>>>> minus 3.0) was so low that the urchins were eventually exposed to the
>>>> air, and from that point onward, could no longer find any wentletraps,
>>>>
>>>> Anybody ever seen anything like this or have any knowledge as to what was
>>>> going on?
>>>>
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