Re: Phyllodesmium magnum on Sinularia

Dear Gary,
Our knowledge of the world would be much poorer without the efforts of what you call 'gentleman scientists'. Charles Darwin was an honoured amateur or gentleman scientist. One of reasons I spend so much of my time on the Forum is because I recognise the great wealth of untapped information and knowledge that is held by 'gentleman and lady scientists', enthusiastic amateurs, etc etc. When I asked why you thought the juveniles were juveniles, and why you thought they were P. magnum, it was to see if you had some background information to share with us all. Trained scientists often get criticised because they won't give a straight answer - they always want to add 'perhaps' or 'but' or 'if'. I guess we develop a way of thinking which puts value in retaining a doubt. Doubts are valuable because they leave the way open for new ideas, and for us to look just 'once more'.  So my first thought when you said these were juvenile P. magnum, was 'how does Gary know that?' not because I disbelieved you or disagreed with you, but because it's important to know why you thought that - perhaps you found them on the same soft coral?, perhaps they had anatomical similarities ? etc. That is the way we build up knowledge, piece by tiny piece.

Concerning the soft corals. I don't claim any expertise in soft coral identification and like many marine invertebrate groups there is still much work to do. There is an excellent book on the topic (Fabricius & Alderslade, 2001) but as you will see there, some of the most common groups are not that easy, and photos alone are not always enough.

With that in mind, the one in your upper photo could well be Sinularia - which is the genus P. magnum has been reported on previously. There is a slight possibility it is Lobophyton, but as that genus has two types of polyps it's not possible to be sure from photos in which the polyps are retracted. And of course the skeletal sclerites and other internal features can't be seen. The soft coral in your lower photo lacks any lobes and could well be Sarcophyton. In your photo you can see well spaced dark pits which I assume are retracted polyps. Sarcophyton has two types of polyps, the large ones are quite widely spaced - like in your photo, and between them are many small polyps, which I think I can make out in your photo as much smaller dark indentations.

• Fabricius, K. & Alderslade, P. (2001) Soft Corals and Sea Fans. A comprehensive guide to the tropical shallow-water genera of the Central-West Pacific, the Indian Ocean and the Red Sea. Australian Institute of Marine Science: Townsville. 1-264.

Best wishes,
Bill Rudman