Marine silk webs
There seems to be a few recent observations of underwater marine silk web structures. I'm not sure whether there are just Desis marina or something else. So just collecting them together here for the time being:
Feel free to add links to more, similar, observations, and comments.
Comments
@fiestykakapo, @stephen_thorpe, @corvink , @phil_sirvid, @steve_kerr, @clinton, @readgb , @russellclarke, @luchoperalta, @leslieh, @susanhewitt, @predomalpha, @invertebratist, @luca_dt
Maybe I should start a project so others can add observations as they find them
Very interesting!
I suspect most of those are made by polychaetes. I agree that a project will help, maybe even a worldwide one.
I searched comments for things like "underwater web", "marine spiders" etc, that should have picked up obs from everywhere and these were the observations that came up. There was some discussion on South African obs, but no photo of similar structures. Mind you I was only searching in English. Also maybe I am looking for "spiderish" terms and others elsewhere know what they are and discuss them in other terms ;-)
These look like the work of terebellidae polychaetes which we found made such webs not long ago. The conversation is in this observation: https://inaturalist.nz/observations/111074873
I had seen these a bit and posted an observation afterwards:
https://inaturalist.nz/observations/112128996
I have since found similar webs and lifted a rock they were attached to to reveal a large terebellid underneath. I guess we can't say for sure for these past observations but the only webs I've seen like this were from terebellidae.
Thanks Luca, I have grouped all these into this observation group: https://inaturalist.nz/observations?field:Observation%20group=112128996. If our experts (@leslieh, @nicolavex, @readgb) confirm that they think Terebellidae is the most likely creator of all these nets, perhaps we should add that genera as an ID to all those observations, as at the moment they have a variety of IDs.
Cool, thanks for organising it all. Yes I agree.
As I've said on a couple of these observations I think they're probably vermetids for the most part. Image #4 with the two large holes is more typical of eunicid webbing centered around a burrow's mouth. Underwater spider webs I've never seen except in images where they seem to have a different look -- smooth silk instead of rough fluff.
Vermetid pics:
https://reefkeeping.com/issues/2005-01/rs/index.php
https://aquariumbreeder.com/vermetid-snails-how-to-remove-them/
https://www.naturepl.com/stock-photo-vermetid-worm-snail-serpulorbis-imbricatus-adamsii-eating-its-mucus-image01353538.html plus this one already mentioned by @lukas_scharer https://www.inaturalist.org/observations/40675306
And for eunicids, this is from an earlier post of mine
"....you can download Chisholm & Kelley 2001 Worms Start The Reef-Building Process here https://www.nature.com/articles/35051660 There are several articles easily found on-line on how Eunice norvegica's relationship with Lophelia pertusa cements reefs
The thread where I learned about eunicids catching food on their web is here https://wetpixel.com/forums/index.php?/topic/40054-question-about-segmented-worm-behavior/&tab=comments#comment-274989 I later had an email discussion with the photographer Bud Barr who sent me additional photos"
Thanks @leslieh for that comprehensive reply. I particularly enjoyed https://reefkeeping.com/issues/2005-01/rs/index.php as it was a great introduction to the world of snails (about which I am pretty ignorant).
I take it then that what look like attachment points in our "nets", are each actually a source of mucus threads from an individual worm snail. If we were to investigate any such 'attachment' point we should find the opening to a snail's tube?
The "web" is actually just an overlap of many such fans of mucus?
I still haven't found any photos quite like our nets, but went through every photo under the Vermetidae taxon and came up with these:
https://www.inaturalist.org/observations?verifiable=any&place_id=any&field:Worm%20snail%20mucus%20net=Yes
(there are lots of others with a few mucus threads, but not much of a 'net')
None of which are quite like our webs, but certainly hint that we're on the right track :-)
The attachment points may also be where strands or a net touches down & sticks rather than the tube opening.
The shape & size of the mucus (strands in a straight line, a broad sheet) might depend on the species, or how much mucus a single animal can emit at one time, or several mucus structures combining, or water currents moving the mucus around.... It would be nice to have a mollusc/ vermetid specialist weight in here for an expert opinion instead of the babblings of a polychaete maven
Thanks @tony_wills for this work. My take is that a number of marine organisms use mucous webs, and thus each web photo needs to be evaluated on its own. So unless you can see a eunicid tunnel opening, a vermetid calcareous tube opening, a terebellid tentacle working along a web, a spider peering out, the webbing can't be assigned to be the work of a particular creator. The iNaturalist aim is to identify organisms and accumulate occurrences of them, but as we all know, this sometimes is just not possible if the photo lacks the necessary info, especially if what we are looking at is something built by an organism, rather than the organism itself. For instance polychaete tubes without anything distinctive about them.
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