Hi all,
In a very interesting ~recent paper re-describing the Sheep Pacu (Ossubtus xinguense Jéju) [see link to pdf below], the authors commented on sexual dimorphism in general among the silver dollar fish [see quote below] -
The first part of the quote i.e., bilobed anal fin in males, versus straight in females of Metynnis, or strongly hooked in females of Myleus, Myloplus, Mylesinus and others, is well known to many of us silver dollar keepers. Nothing new there.
However, the second part of the quote may not be well known, and I wanted to share it here and offer it in invitation to conversation and possibly sharing of observations.
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From Andrade et al 2016, PLos ONE-
[httpd://doi.org/10.1371/journal.pone.0161398]
"...Ossubtus xinguense shares with herbivorous Serrasalmidae... dimorphic features mainly evidenced by the anal fin wherein mature males have an additional lobe formed by elongation of the middle rays, which sometimes bear divergent hooks distally, ..."
Their figure 12 shows in detail such hooks. They are amazing! Check them out. We are not talking about the "hooks" we describe on our Red Hook or Emperor Hook fish, but to micro-hooks on the actual surface of the fin. Check the figure!
One may infer that these micro hooks assist the courting male, who is courting and shimmiing towards the female, to fold his anal fin over that of hers during courting and spawning. I have seen such behavior in Metynnis videos and on my own fish, but I had no idea that in some species there could even be mini hooks on the fin to assist the purpose.
Cool!
In a very interesting ~recent paper re-describing the Sheep Pacu (Ossubtus xinguense Jéju) [see link to pdf below], the authors commented on sexual dimorphism in general among the silver dollar fish [see quote below] -
The first part of the quote i.e., bilobed anal fin in males, versus straight in females of Metynnis, or strongly hooked in females of Myleus, Myloplus, Mylesinus and others, is well known to many of us silver dollar keepers. Nothing new there.
However, the second part of the quote may not be well known, and I wanted to share it here and offer it in invitation to conversation and possibly sharing of observations.
--------------
From Andrade et al 2016, PLos ONE-
[httpd://doi.org/10.1371/journal.pone.0161398]
"...Ossubtus xinguense shares with herbivorous Serrasalmidae... dimorphic features mainly evidenced by the anal fin wherein mature males have an additional lobe formed by elongation of the middle rays, which sometimes bear divergent hooks distally, ..."
Their figure 12 shows in detail such hooks. They are amazing! Check them out. We are not talking about the "hooks" we describe on our Red Hook or Emperor Hook fish, but to micro-hooks on the actual surface of the fin. Check the figure!
One may infer that these micro hooks assist the courting male, who is courting and shimmiing towards the female, to fold his anal fin over that of hers during courting and spawning. I have seen such behavior in Metynnis videos and on my own fish, but I had no idea that in some species there could even be mini hooks on the fin to assist the purpose.
Cool!
