Yesterday the ‘Borneo orange’ zoes started metamorphosing into post-larvae. The visual change isn’t very dramatic, but their behavior is totally different. Rather than hovering in the water column occasionally puttering backwards, now they perch in one place and occasionally zoom forwards to a new perch.
Most likely this means that they’re ready to start a marathon swim upstream into fresh water. I moved the above photo subject into a cup of fresh water to see how it likes the change. With larvae that live in pure sea water (Yamato shrimp and others) I’ve been very careful to move them gradually through several stages of brackish before transferring them into pure fresh water. Since these guys live in water that’s already only barely salty, I’m hopeful that I can skip that tedious phase.