Hi Chris,

I have recently come across a problem with the Barrel Jellyfish (Rhizostoma pulmo) and the apparent differing understanding of the relationship between this species and Rhizostoma octopus (which currently the UKSI shows as being a synonym of R.pulmo).

The issue began on iNaturalist as can be seen from the discussion on the following link:  https://www.inaturalist.org/observations/32489790.  Here the user on iNat (wyattp11) notes that the international understanding is now that R.pulmo and R.octopus are separate species with differing distributions

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wyattp11 commented:
Yes, that is all old, incorrect information. There has been considerable work done recently, the life cycles of both have been independently described:
https://link.springer.com/article/10.10 … 006-0594-8
https://link.springer.com/article/10.10 … 011-1730-7

And even more recently it was shown that R. octopus may actually comprise several species or sub-species:
https://academic.oup.com/biolinnean/art … 82/2440366

A third species, R. luteum is now recognized which was also synonymized into R. pulmo previously. This species separates the two around the Iberian Peninsula.

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WoRMS seems to support this - see here:  http://www.marinespecies.org/aphia.php? … tributions and  http://www.marinespecies.org/aphia.php? … ;id=152203

Thanks for your help - it looks like Rhizostoma pulmo will need to be split once more.

Steve