drop eye again....... wikipedia
- Thread starter johnptc
- Start date
If you need a theory then here is mine. Some PhD doctoral student should study it. Silver aros evolved in acidic tannin rich streams and rivers in the Amazon basin. These fish were surface feeding predators and required large eyes and optic lobes to support their need to see in these dark waters as well as the branches above it. Since there are no barriers to leaping for a riverine fish; the enlarged eye was not an evolutionary liability until we started keeping these in aquaria with solid glass or plastic lids. The specific gravity of the Amazon water may also be different than that of the habitat of jars and Asians and may help support the large eye formation of the Silver. I bet that jars come from clearer water and are piscivorous as adults, rather than wanting to feed as much from the surface as they did when they were juveniles. Asians have clearer waters to swim in than silvers but also inhabit tannin rich water. Along with these other observations, one should also consider the more snake like appearance of the silver and the reduction of the caudal fin considering that these likely had a single ancestor before the breakup of the Continents. The silver moves by a series of pressure waves exerted against the water. This type of serpentine motion is not seen in the jar and asian. Can one of these touch it's mouth with it's tail? I think not. Therefore the fluid environment and hydrostatic forces are different for the evolution of the silver.
Miguel;832986; said:
I still have her and my 8 year old son that tried to show his friends that he could pet my Aro before I found out what he was doing. He was standing up on a chair ready to crash through the glass before I scolded him. I broke a good rule of aro keeping by locating my tank in the family den. The dogs, Wife and son walk by this constantly. Now he is a calm aro and I leave on the light.
Crustman;833004; said:
my large jar (24"+) was a mid water fish and didnt spend alot of time at the surface
Crustman;832997; said:
and what, or where, will my learned colleague, apply to the black which, admittedly, is as serpentine as the silvers and hails from the very same environment???
Crustman;832997; said:
One must also consider that the Potamotrygonids are the only fw stingrays (with the exception of D. sabina) and this adaptive radiation occurred in Amazon rivers and streams. They also move by a serpentine pressure waves exerted ventrally instead of laterally like the silver.
I am not going to try and comment on everything said here but you guys no my theory and high protein diet isnt a woory in my book my silver is on a 46% protien pellet and his DE has only gotten better but I think that is due to the pond
I don't know enough about the blacks and their feeding niche. I bet if more people kept and could afford blacks then the incidence of drop-eye would go up. Are their eyes of the same form as the silvers? They don't get as large as the silvers and the orbital size in relation to the skull size may not be as large. Also what are the diameters of the eye as compared to body length for juveniles of both silvers and blacks. There has to be some papers on all this stuff. Surely the ichthyologists have taken micrometer measurements of all the cranial bones. I studied ichthyology and marine biology but now work in crustacean taxonomy. There has to be a logical explanation for drop-eye but all ideas need to be tested and there is no one to do it. Maybe TFH offers grants for study of aquarium fish or even NSF if someone is in a college setting and get a government grant to study it. There needs to be a place on this site where one can record the following for every silver purchased:
tank size
initial size
wild caught or pond raised if known
diet
size when drop eye observed
head tauma or not
missing head scales indicating bashing
eye affected
other parameters
This would give a baseline of information instead of all these random posts on fish affected.
tank size
initial size
wild caught or pond raised if known
diet
size when drop eye observed
head tauma or not
missing head scales indicating bashing
eye affected
other parameters
This would give a baseline of information instead of all these random posts on fish affected.
