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Nannostomus – adipose fin

Home Forums Fresh and Brackish Water Fishes Nannostomus – adipose fin

This topic contains 0 replies, has 1 voice, and was last updated by  deepinpeat 3 years, 5 months ago.

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  • #303207

    Graham Ramsay
    Participant

    Acording to the weitzman paper the adipose fin is absent in N. minimus whilst in N. marilynae it is always present. In the N. minimus I have most have an adipose fin and a few don’t. (You can make out the adipose in the pictures of mine in the profile for N. miminus including the fry). I ordered some marilynae (definitately not minmus said the store, they are different from the minimus we had before) and a friend picked them up and has them in his tanks just now. They appear to all have an adipose and look suspiciously like my existing N. minimus. So what I guess I’m saying is that the presence, or not, of an adipose fin is not a diagnostic feature for N. minimus assuming all these fish are indeed N. minimus.

     

    Capture.JPG

    #352894

    Byron Hosking
    Participant

    Your last sentence may be the answer, on two fronts.  Could this species be N. digrammus?  Looks similar to me, but photos are not always easy in identification.

    There are some photos supposedly of N. minimus here

    http://apisto.sites.no/fish.aspx?FishIndexID=2469&gruppeId=5

    though I’ve no idea as to the reliability of the species ID.

    In the species N. eques the adipose may or may not be present, according to Weitzman.  I have this species, and the adipose fin is so tiny I can barely see it but it is present at least on some of my fish.  I also have the similar N. unifasciatus which is supposed to have an adipose, but mine do not, unless here again it is so miniscule I just can’t see it.  It would seem that there is some variation within certain species in this genus.

    Weitzman and Cobb (1975) is not a recent work.  Weitzman (Stanley and I believe his wife Marilyn) supplied the data on these species for the 2003 Checklist…does anyone have access?  I did once, but now can’t seem to get it online.  It is pages 241-251.  This might have something more recent?

     

    Byron.

    #352900

    Matt
    Keymaster

    Graham, is presence or absence of the fin variable in the fry or only the adults?

    Weitzman gets his information regarding N. eques from the o.d. by Steindachner. I’d always assumed that presence or absence of an anal fin in Nannostomus was relative to population, i.e., some have it, some don’t, but if there’s variation within populations could it be that the group is in the process of losing the fin? It appears to be a variable trait throughout Lebiasinidae.

     

    #352917

    Graham Ramsay
    Participant

    From what I can see, and it’s difficult to make out, some have, most have not.

     

    Nannostomus_minimus_6weeks.jpgNannostomus_minimus_6weeks_2.jpg

    #352962

    Matt
    Keymaster

    That’s really interesting. Wonder if it’s natural or a result of population-mixing.

    #353077

    deepinpeat
    Participant

    Did anyone consider this could be a mutation caused by some endogenous factor or such mutation already fixed in an aquarium population? Where did the breeders come from + if they were wild cought are you sure they come form the some population? Some populations species may also be able to crossbreed. I know a guy offering N.mortenthalleri x N.beckfordi hybrids. Def interresting stuff here, glad to find such a forum. 

     

    Pavel

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