Check out this pip-squeak fish: a 2 inch culia inconstins: the brook stickleback. Note the lack of pelvic fins.
Note how inconstant they are. Mine didn't have pelvic spines, and it's head is really narrow like a pike or something. Sometimes they have a nice jaguar like pattern of light green on a shiney greenish dorsal surface with a redish tint to the belly. Some have 6 spines, some have 4... the ones I found have 5 spines along their back.
According to a book of mine, they don't have pelvic spines after enough natural selection, if there aren't very many predators. Find the snail in the picture below.
Eh, fathead juvenile at 1.5 inches, Silver and brown, with a dark line going along. I think they are the cutest. Not the best fathead picture around. I couldn't seem to keep these fatheads alive for long... because they were wild caught...juvenile... and possibly being terrorized by tankmates.
