ANN ARBOR, Mich., Dec. 9 (UPI) -- A U.S. biologist estimates as many as 1,600 catfish species might be venomous, and venomous fish far outnumber all other venomous vertebrates.
Graduate student Jeremy Wright of the University of Michigan said he employed "histological and toxicological techniques" in his examination of 158 catfish species. He then used the resulting data to estimate the total number of venomous catfish species.
"Based upon the generic identity of the venomous species identified, the number of species contained within those genera and the number of remaining unexamined species in those families shown to contain venomous representatives, an estimate of 1,234-1,625 venomous catfish species was developed.
"The number of venomous catfishes estimated by this study (when combined with estimates of venomous spiny-rayed and cartilaginous fishes) supports previous claims that venomous fishes far outnumber all other venomous vertebrates, and also demonstrates that venomous catfish diversity likely equals or exceeds that of all other venomous vertebrates (including other fishes) combined," he said.
Wright said his analyses also indicate catfish venom glands originated from at least two independent evolutionary pathways.
"Further examination of the chemical composition of the venoms will provide valuable insight into the mechanisms and potential selective factors driving venom evolution in fishes", he added.
The study is reported in the journal BMC Evolutionary Biology.
