So I’ve been to a lot of doctors offices and hospitals recently. Uterine Fibroid tumors are no joke! I’m on the mend now thankfully. Anyway, I noticed that many of them had aquariums, but they were all reef tanks. I mean they are pretty and all, but fresh water tanks can be just as beautiful. Do you guys have any idea why freshwater tanks aren’t more popular at places like this?
The general public like seeing marine fish, they are more colourful and odd (a debatable point, but it is widely held). When I visit the Vancouver Aquarium and browse the marine tanks and the freshwater, I can certainly understand where this comes from. I have never ventured into marine because of the expense and work (perhaps also debatable) but more to the point, I find freshwater habitats absolutely fantastic. One can certain see evolution more clearly in freshwater than marine; the oceans have identical parameters (GH, KH and pH) so all marine fish evolved in that habitat. But each freshwater water course can be very different from the others, and the fish in each individual water course have evolved to fit in that specific habitat and no other. Though obviously many are similar, but the species clearly show evolution at work.
We can see this occurring today. One example, the freshwater hatchetfish
Carnegiella marthae, which is found in many blackwater (and I believe clearwater) habitats in Amazonia and northern South America. One assume it is one species. Not so; phylogenetic analysis have now determined there are actually three distinct lineages among this "species," each having evolved from a different common ancestor. There are no external differences, but the genetics tell this story. Something similar is occurring or has occurred in the sister species,
C. strigata which is the lovely marble hatchetfish. More recent phylogenetic analysis has shown that while the genus
Carnegiella is monophyletic, the species
C. strigata is not. Examination of populations within the Negro and Uatuma blackwater rivers has revealed two monophyletic lineages within this species, with considerable genetic distance (10-12%) between them, making it probable that there are two distinct species within this complex (Schneider,
et al, 2012; Abe,
et al, 2013).