Ostrich penis clears up evolutionary mystery BRENNAN AND PRUM 2011 Flashcards
authors
brennan and prum 2011
what is the long running question to do with bird penises?
how the ratites erect their penises
what was the study species
2 members of the ratites ostrich and emu
how did they do it?
dissection of specimens
what did they find?
erect penises using a burst of lymphatic fluid rather than blood as is seen in reptiles and other mammals
what could the findings have implications for?
the understanding of the shared and divergent evolutionary history ofbirds and reptiles
the authors suggest that the lymphatic erection occurred when in the bird phylogeny?
in the ancestor of all birds
the origin of lymph driven erections has yet to be uncovered but what may it reflect?
an evolutionary arms race
male ducks often force sex on females, and in response females have evolved complex anatomical defences against these unwanted attentions but the lymphatic erection offers a way around these because it allows a rapid on/off means of extending the penis and enables deep insemination
what does it say about reptile and bird penis?
although they use different mechanisms to acheive erection there are also similarities in the tissue in both organisms and it is likely that they evolved from the same tissue
what is the most provocative thing about this research?
not what it says about bird penises, but rather what it implies about the lack of them for the vast majority of birds.
“Darwin and others said that penises were primary sexual traits, meaning they’re essential for reproduction. But the birds say they’re not,” notes Montgomerie. Instead, he says, the penis may be a secondary sexual trait, helpful for stimulating the female, signalling reproductive fitness and even an aspect of competition among males — but not indispensable.
