Diopatra along the eastern Australian coast

Anyone who has beachcombed along the eastern Australian coast at least a few times will likely have stumbled upon a Diopatra tube at some point. The inner lining of this tube is made of a tough, parchment-like layer, and isn't too exciting looking:

The outer layer, however, is much more unusual, with the worm attaching seaweed, shells and other debris to the tube:

At time of writing there are ~160 observations of Diopatra on iNat along the east Australian coast, from the Sunshine Coast down to the Victorian border. Most of these (~85%) are identified as Diopatra dentata, including many IDs by myself. At face value it seems like a straightforward one; a number of books and other marine ID resources, such as W.J Dakin's Australian Seashores and Graham Edgar's Australian Marine Life show images of these tubes and ID them as Diopatra dentata.

However, I recently discovered that this is not the only species found along the east coast, and there are in fact three described species in this region: amboinensis (at the northern end of the range), aciculata (along NSW) and dentata. Paxton's 1993 revision of the genus (see https://www.biodiversitylibrary.org/part/271283) provides descriptions for the tubes of each:

You'll notice that the descriptions are quite similar, and that, if dealing with an old and damaged tube with the outer layer partially or fully lost, as is often the case, it becomes very difficult to make an ID. So last night I emailed Pat Hutchings, an incredible polychaete expert and authority, about the situation. She confirmed to me that these Diopatra can realistically only be confidently IDed to species from the worms themselves, and that any records of just the tubes should ideally be kept at a genus ID.

Now based on collections and records referenced in the literature, dentata does indeed seem to be the most widespread and common of the three, and thus many of the records currently IDed as dentata on iNat are almost certainly correctly IDed. But because of the uncertainty, it's most appropriate to keep these IDs to genus, so I'm going to go through and bump them back now

tagging top IDers and observers:
@adrian2370 @nicklambert @twan3253 @urungaroger @ben_travaglini @leslieh @lynsh @cesdamess

feel free to tag others too

Posted on May 23, 2024 01:57 AM by thebeachcomber thebeachcomber

Comments

Devastating blow to my species count. Thanks for that. It will be interesting though as I'll now pay closer attention to their tubes with these descriptions in mind...

Posted by nicklambert 2 months ago

Thanks Tom, I’ll adjust my observations and keep that information in mind for future observations/identifications.- Roger.

Posted by urungaroger 2 months ago

Thanks Tom for the info. I think I missed this originally.

Posted by lynsh 2 months ago

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