Normally freshwater fish meristic character of fin ray counts example dorsal fin or caudal fin rays count variability of same within species it possible or not if possible why it occurred.
It varies within species. It is partly heritable, and partly dependent on a range of environmental factors during development affecting developmental rates, e.g. temperature. Meristic differences between populations of the same species can depend on different temperatures in the water when they grow up. If you search for "meristic variation" on Google Scholar you will find many papers on this.
It varies within species. It is partly heritable, and partly dependent on a range of environmental factors during development affecting developmental rates, e.g. temperature. Meristic differences between populations of the same species can depend on different temperatures in the water when they grow up. If you search for "meristic variation" on Google Scholar you will find many papers on this.
The variation occurs within the species and also within the same species depending partly on genetics and partly on environment basically depending on temperature.
Populations at higher latitudes and colder climates may have a more slow growth and counts in the meristic characters with higher values.
The ambient temperature at certain early embryonic stages can affects meristic characteres like number of fin rays, vertebrae etc. See e.g. Tånings work on Atlantic salmon during WW2. Low temperature usually result in higher counts.
I really don't know how it is with other species, but looking at developmental series of gars (Lepisosteus oculatus and Lepisosteus osseus) I have noted that in counting forming scales along the lateral line and body myomeres there is one scale formed for each myomere. There is a possible exception that there appears to be the fusion of some of the most anterior myomeres so that the most anterior lateral line scale may be over two or three small, fused myomeres. Once the number of myomeres is established within an individual the number of lateral line scales is fixed. My guess is that there is an interaction between environmental factors, such as temperature, and the HOX genes so that there should be a fairly short period of developmental plasticity in these species.
Numeric or meristic characters, a set of quantitative variables that result from counting the elements of a fish organ, are used to characterize the different species (their number varies according to species and their morphology).
They correspond, in fact, to discrete variables that provide objective data because they are independent of examined fish size.
However, within the same species, they discriminate populations, due to the influence of certain environmental factors, especially temperature, on these characters during growth.
Some fin counting formula are there and it contains the range also. If exceed the range means exceptional...the reason mostly genetic-environmental variation. Formula for fins of fishes-
https://link.springer.com/content/pdf/bbm%3A978-3-642-82858-4%2F1.pdf
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