Has anyone had external gills present on their adult polys? I'm trying to form a hypothesis about bimodal respiration and the development of external gills in polypterus and I need to answer this question first.
Do your big guys and gals have external gills: mehanisms of bimodal respiration
- Thread starter LRM
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Are you thinking that, in a deoxygenated environment, the fish would keep the external gills through adulthood?
Doesn't matter what you do with the oxygen level. It will depend on the species of bichir, size and age that when the external gills disappear. Weeksii are known to have the longest external gill that stays even when adults. Also some PBB and congicus will still have their external gills even at 18"+. No matter what you do it will disapear as time passes by unless it's genetically altered in the lab.
Okay okay, I'll explain my thought process. I study bimodally breathing turtles. By that I mean I work with turtles that respire both by breathing air and by exchanging gas in the water. Believe me, turtles are good at that. There is one species that takes 70% of its O2 from the water and it is not a sea turtle.
So here is the deal. The theory of optimal breathing (Kramer 1988) states that aquatic bimodal breathers will decrease their reliance on pulmonary (lung) stores of oxygen as the cost to obtain it increases.
This means that if the risk of predation increases, they'll spend more time breathing aquatically
If the distance to the surface is too great and it would take a lot of energy to surface, they will spend more time breathing aquatically
If the dissolved oxygen in the water is very high, they will spend more time respiring aquatically
If the current is very strong, they will spend more time respiring aquatically.
So I imagine that there is a phenotype (physical gene expression) in young polypterus in the form of increased gill surface area (external gills) to maximize the amount of aquatic gas exchange that manifests itself depending on external factors.
Ya dig?
So here is the deal. The theory of optimal breathing (Kramer 1988) states that aquatic bimodal breathers will decrease their reliance on pulmonary (lung) stores of oxygen as the cost to obtain it increases.
This means that if the risk of predation increases, they'll spend more time breathing aquatically
If the distance to the surface is too great and it would take a lot of energy to surface, they will spend more time breathing aquatically
If the dissolved oxygen in the water is very high, they will spend more time respiring aquatically
If the current is very strong, they will spend more time respiring aquatically.
So I imagine that there is a phenotype (physical gene expression) in young polypterus in the form of increased gill surface area (external gills) to maximize the amount of aquatic gas exchange that manifests itself depending on external factors.
Ya dig?
Okay, for example, they live in shallow water in African river systems right? So its warm water areas. Warm water holds less oxygen than cold water so they should be taking advantage of atmospheric air by "gulping". But... with lots of predators, large water bugs, fish, turtles, snakes, water birds, crocodilians etc. they would probably benefit from being able to extend dive times between gulps of air. So I was thinking that developing these external gills to increase gill surface area would probably be an amazing adaptation to give them an edge on survival.
You have a clear point that makes sense to me. So would you be seeking out an existing population of polys that have been meeting these conditions for a long time to compare that population's external gill reabsorption pattern with that of others?
Right now my plate is really full. This is sort of a back burner thing. Ideally I'd be able to get 60 or so in the lab and just run a bunch of experiments on them to look at plasticity of the gills, diving behavior under different behaviors etc. Its something I neither have the funding or the time for but certainly something I wouldn't mind doing if the opportunity arose.knifegill;4365001; said: