Tuesday 26 November 2013

FACT! A female duck's vagina have multiple entrance to prevent rape

Bi­ol­o­gists have found ana­tom­i­cal de­tails about the fe­male re­pro­duc­tive tract in wa­ter­fowl that they say in­di­cate male and fe­male an­atomy have co-e­volved in a “sex­ual arms race.”
Bird cop­u­la­tion most­ly con­sists of a sim­ple, and rath­er chaste, “cloa­cal kiss” in which two open­ings come to­ge­ther. But a few an­cient bird lin­eages, in­clud­ing wa­ter­fowl, re­tain the grooved phal­lus of their rep­til­i­an an­ces­tors. Wa­ter­fowl are al­so dis­tinct in hav­ing great di­ver­si­ty among spe­cies in the length and or­na­men­ta­tion of the phal­lus.
Sci­en­tists pre­vi­ously at­trib­ut­ed this di­ver­si­ty to sperm com­pe­ti­tion. They spec­u­lat­ed that sperm from ma­les with a long­er phal­lus had a com­pet­i­tive edge over sperm from those less well-en­dowed. The new re­port in the on­line re­search jour­nal PLoS One finds more to the sto­ry.
“As part of a re­search pro­gram on the ev­o­lu­tion of the avi­an phal­lus, I was cu­ri­ous to know if there were con­se­quenc­es to fe­male ducks of the tre­men­dous ana­tom­i­cal var­i­a­tion found in the male phal­lus,” said lead au­thor Pa­tri­cia Bren­nan of Yale Uni­ver­si­ty in New Hav­en, Conn. and the Uni­ver­si­ty of Shef­field, U.K.
Her study is a com­ple­men­tary ex­plo­ra­tion of the an­atomy of the fe­male re­pro­duc­tive tract, called the ov­i­duct or va­gi­na, which is usu­al­ly very sim­ple and si­m­i­lar among birds. Bren­nan found two un­ex­pect­ed­ly com­plex and new struc­tures that she said seem de­signed for one pur­pose — to se­lec­tive­ly ex­clude the phal­lus.
In most birds, the ov­i­duct is a sim­ple tube, but in some wa­ter­fowl, the tube has unique sacs and spi­rals. The sacs are out­po­cket­ings in the sides of the tube that are just in­side the ov­i­duct open­ing. “They ap­pear to func­tion as ‘dead-ends,’ or false pas­sages,” said Bren­nan. “If the phal­lus were to en­ter one of these sacs, it would not prog­ress fur­ther in­to the ov­i­duct where it would de­pos­it sperm more ef­fec­tive­ly.”
The sec­ond nov­el­ty is a se­ries of tight, clock-wise spi­rals in the tub­u­lar ov­i­duct. “In­ter­est­ingly, the male phal­lus is al­so a spir­al, but it twists in the op­po­site, counter-clockwise, di­rec­tion,” said Yale or­ni­thol­o­gist and co-au­thor Rich­ard Prum. “So the twists in the ov­i­duct ap­pear de­signed to ex­clude the op­pos­ing twists of the male phal­lus.”
The num­ber of sacs and spi­rals in the re­pro­duc­tive tract of var­i­ous fe­male wa­ter­fowl cor­re­lates strongly with the length of the male phal­lus, the sci­ent­ists wrote.
Com­par­ing the phal­lus size and ov­i­duct shape in 14 dif­fer­ent spe­cies of ducks and geese, the au­thors con­c­luded that the gen­i­ta­lia of ma­les and fe­ma­les have dy­nam­i­cal­ly co-e­volved: in var­i­ous se­parate duck lin­eages, fe­males de­vel­oped more elab­o­rate ov­i­ducts as males evolved long­er phal­luses. In oth­er lin­eages fe­males lost ov­i­duct com­plexity as the phal­lus evolved to­ward smal­ler size.
Bren­nan hy­poth­e­sizes that the fe­male wa­ter­fowl have evolved these ana­tom­i­cal fea­tures to block male at­tempts at re­pro­duc­tive con­trol. “De­spite the fact that most wa­ter­fowl form mo­nog­a­mous pairs, forced cop­u­la­tions by oth­er ma­les — the avi­an equiv­a­lent of rape — are com­mon in many wa­ter­fowl,” said Prum. “The length of the phal­lus of a spe­cies is strongly cor­re­lat­ed with the fre­quen­cy of forced cop­u­la­tions.”
“In re­sponse to male at­tempts to force their pa­ter­ni­ty on fe­ma­les, fe­male wa­ter­fowl may be able to as­sert their own be­hav­ior­al and ana­tom­i­cal means of con­trolling who fa­thers their off­spring,” Bren­nan said.
The au­thors pro­pose that ornate phal­luses and fe­male ov­i­ducts have co-e­volved in re­sponse to one an­oth­er. More elab­o­rate phal­luses have se­lected for im­proved means of ex­clud­ing them, and vi­ce versa.
What hap­pens when a fe­male duck wants to mate with its cho­sen part­ner? The au­thors spec­u­late that these phys­i­cal bar­ri­ers are eas­i­ly overcome when fe­ma­les co­op­er­ate, and that they only func­tion to ex­clude un­want­ed ad­vanc­es. Bren­nan is pur­su­ing the find­ings with fur­ther ex­plo­ra­tion of the de­vel­op­ment and ev­o­lu­tion of bird gen­i­ta­lia. “I am sure there are more sur­prises out there,” she said.



Culled from World-Science.com

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