WELCOME TO OPEFE ARCHIVES
Examining Piranha Gonads: Is it possible for a hobbyist to determine sex using scientific methods?
by Frank Magallanes - February 18, 2005
There is much interest among hobbyists that breed piranhas if it is possible to determine sex of a piranha during fry stages by examining the belly region via bright light and magnification. This question was brought forth after I made available information found on the internet about Medaka Fish and the examination of ovaries.
Unfortunately, it is not possible for just anyone to do it. The gonadal examination of Pygocentrus piraya is an often cited article by hobbyists who believe they can sex piranhas using this method. However, it is a complex procedure and the fishes used in that report were in the range of 6 cm to 34 cm SL (juvenile to adult). The gonads were examined by histological sections by embedding them in paraffin blocks and slicing, and couter staining with eosin/hematociciline. This is the standard method at looking at egg development. Using the Medaka model above it is also not possible to see ovaries on piranha fry fish as well. Gonads are under-developed in fry fish, therefore not possible to determine sex of piranhas. Some hobbyists have reported seeing granules or globule like objects similar to the Medaka model. Those are more than likely fat beads. Larvae and/or fry that consume brine shrimp naupalii will also give the illusion of eggs in that region, but it is undigested food (see photo upper left).
Presently, the only piranha species known to be sexually dimorphic (external sexual characteristics) is Pygopristis denticulata, the anal fin is bi-lobed.
BLACKSMITH, R.M.A.; BAZZOLI, N.; RIZZO, E.; SATO, Y. - reproductive Aspects of piranha, Pygocentrus piraya (Teleostei, Characiformes), native species of the basin of the River Sâo Francisco. Arq. Bras. Med. Vet. Zootec. 48 (supl. 1): 71-76, 1996.
CROSS, A.M.G.; SATO, Y.; RIZZO, E.; SAINTS, G.B.; BAZZOLI, N. sexual Maturação of piranha Pygocentrus piraya (Cuvier, 1820) (Pisces, Characidae) in the dam of Three Marias, Minas Gerais. Bios , 4 (4): 17-22, 1996.
Cuvier, G., Memoires du Museum National d'Histoire Naturelle, Publishing date; 1819, Sur les poissons du sous-genre «Hydrocyn, sur deux nouvelles espèces de «Chalceus», sur trois nouvelles espèces de «Serrasalmes», et sur l'«Argentina glossodonta» de Forskahl, quiest l'«Albula gonorhynchus» de Bloch. Cuvier, G. . 1819 Mem. Mus. Natl. Hist. Nat.. 5:351-379.
USE YOUR BACKSPACE TO RETURN OR CLICK HERE TO RETURN RESEARCH PAGE
TO RETURN HOME CLICK HERE
The OPEFE web site and its contents; is disclaimed for purposes of Zoological Nomenclature in accordance with the International Code of Zoological Nomenclature, Fourth Edition, Article 8.3 and 8.4. No new names or nomenclature changes are available from statements at this web site.
Copyright© 1994-2012 Oregon Piranha Exotic Fish Exhibit (The OPEFE fish exhibit is permanently CLOSED as of 2000) Sutherlin, Oregon. Information posted on this web site is archival data on fish scientific classifications and other information. DISCLAIMER: The copyrighted material may not be used for any purpose other than private study, scholarship or research. Cited information requires credit and this link www.opefe.com. All rights reserved. All images shown (unless otherwise noted) is property of OPEFE.