Amphibious African Killifish

[Ekona]

Check this out: I got a bunch of wild Scriptaphyosemion geryi killifish from Jeff. After being in the aquarium for a few days and seemly doing fine, one point , one-by -one, all the killifish started jumping out of the water and sticking themselves on the glass sides of the aquarium. They would stay stuck to the glass sides for up to several minutes before flipping back into the water and then jumping back out after a few seconds. It started with one and then the others seemed to catch on and do the same thing. I've never seen anything like it.

I suspect that the temperature of the water was getting too warm (~78F) and perhaps lowering the dissolved oxygen content to a level unacceptable to the fish (they are said to originate in streams with high O2 content). Species of the genus Scriptaphyosemion are known to be exceptionally good jumpers, able to escape through the tiniest of openings in an aquarium. I've known this, but never considered why they are such good jumpers. Now I think I see at least one reason why - when water temps or other parameters become unfavorable to them, they can resort to literally "flipping out" of the water to get more oxygen in a semi-amphibious manner. I can imagine them flipping into moist leaf letter or sticking themselves onto leaves of overhanging plants at the water's edge and lodging there for a while or even migrating to a better water hole. I now recall that certain species of Rivulus do this as well.

I've lowered the water level, reduced the temperature and added an airstone to increase O2 levels and the jumping behavior has stopped. Pretty neat to observe it though, and was able film the geryi jumpers in the video below.

Also got this rather amusing photo of three of the females stuck to the glass sides, hanging out as if they were "at the beach" or something.

 

[gerald]

Could they be avoiding annoying males? Or maybe it's an athletic competition. My Kryptolebias did this a lot when they were younger, usually in response to being startled, but sometimes for no obvious reason (to me). It's surprising that there aren't any killies known to lay eggs above water, given how common this jump+stick behavior is among a wide variety of killies.

 

[Ekona]

There is one male and 4 females in this group, I think, and the male did not appear to be overly aggressive. I really think it was the rise in temperature and lowered DO, but who knows could be they just like to have fun? The other thing that induces them to jump is any kind of current in the tank - I was trying a small mini filter set on low which put out a rather mild current, but as soon as it came on the started swimming right up to the outflow and then they started jumping. Turned it off, no jumping.

 

[ChiefBrody]

Some fish lay eggs on overhanging leaves in this way also

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