As this is my first post I'd just like to say I think this is a great tool for persons with an interest in the outdoors such as myself.
My question concerns the small animal we found on a recent trip to the Caribbean (picture attached). We saw a few and they generally range in size from 10mm-15mm. The were extremely mobile in the water. From my google searches I believe it may be some kind of isopod and possibly a parasite of fish (gills) but I am quite unsure.
Any help you could provide in identifying this animal would be much appreciated.
Such a good photo of such a tiny creature surely deserves a decent ID, but the best photomatch I could find was Australian of the cirolanidae, http://crustacea.net/crustace/isopoda/www/cirolan.htm . But then I found "guide to the marine isopods of the caribbean (1989, Smithsonian institution)" which happily is on the net (238 pages), & the group containing Cirolanidae ( the Flabellifera) is on pp's 114-236 eg http://archive.org/stream/guidetomarineiso00kens#page/114/mode/2up ,but to decipher all the text you'd need the glossary on P.6 & especially diagram P.8 (substitute 8 for 114 in above link or better use slider line at foot of page to navigate). Contents page n7 [NB Flabellifera is an older group now superceded].[& NB even the glossary doesn't explain it's own terms, such as Setae=bristles].
Anyway,by focussing largely on the size of 3 features, the large antenna, the antennule (=small antenna; on yours looks like a moustache), & eyesize, the only one I found to fit was Excorallina tricornis tricornis on P.164. Unfortunately the illustration & text shows the "cephalon" (=head) has 3 "horns" which the photo P. 167 confirms ;but rereading the text it's "cephalon in the male". So conclude it's most probably a female Excorallina tricornis [another source says it's a parasite of the gills& spiracles of fish]
Wow Rhossilian, thank you very much for your efforts. It looks like female Excorallina tricornis could be the one. That is also a very interesting guide that you have highlighted and I will be sure to bookmark it.