Halgerda formosa -colour variation [1].

Dear Yves,
Thanks for your great collection of photos. As I wanted to keep the images reasonably large I have separated them into a number of separate messages [see message 2, message 3, message 4]. I am sure they are all one species and so show the variability found in Halgerda formosa. As I have often said, extra photos are never a waste. In this case we now have an excellent idea of the variation to be found in this species. I have discussed the variation in a separate message.

Your observations of this species on a red sponge are also of great interest and almost certainly indicate its food sponge. It is most likely that this species has a seasonal cycle. In tropical waters we tend to think that because there aren't the obvious temperature changes associated with the 'seasons' found in temperate climates, that tropical waters don't have changes during the year. Anyone who has spent much time in tropical environments soon realises that there are indeed seasonal changes in the tropics associated with monsoons, wet seasons etc, and althought there is not much published on the topic, many organisms go through annual cycles just like in temperate waters,

Thanks again for this wonderful collection of photos
Bill Rudman