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Boa Constrictor Gives Birth to Remarkable Fatherless Offspring ­ 80beats : 80beats
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Boa Constrictor Gives Birth to Remarkable
Fatherless Offspring
By Andrew Moseman | November 3, 2010 10:48 am
A tiny fraction of vertebrate species have
ever been seen reproducing through
parthenogenesis, the fatherless birth of
offspring in which the embryo develops
without fertilization by a male. Now you can
add boa constrictors to that short list: A
study in Biology Letters documents the case
of a boa that gave birth to 22 offspring over
the last two years, all of whom are female
and born this unusual way.
“Only with the development and
application of molecular tools have we
truly begun to understand how common
this form of reproduction may be,” lead
author Warren Booth [says]. Booth, a
research associate at North Carolina
State University’s Department of Entomology, and his team first suspected something was up when
the mother boa constrictor gave birth, twice, to a total of 22 caramel­colored females. The males
housed with the female did not carry the gene for this recessive color trait. [Discovery News]
When Booth’s team analyzed the DNA of the young snakes, they found no evidence of paternity by any of
the males who’d mated with their mother previously. Furthermore, the chromosomes of the 22 young
gave them away.
In place of X and Y, snakes and many other reptiles have Z and W chromosomes. In all snakes, ZZ
produces males and ZW produces females. Bizarrely, all the snakes in these litters were WW. This
was further proof that the snakes inherited all their genetic material from their mother, as only
females carry the W chromosome. [BBC News]
WW snakes have been produced in the lab before, but never seen occurring naturally. It was not even
clear whether a WW snake could be viable.
So Booth’s team has achieved a first, though previous studies have seen parthenogenesis in sharks,
lizards, and Komodo dragons.
Long thought to be vanishingly rare, parthenogenesis is becoming more common the more scientists
look for it. For instance, in 2003 a Burmese python in an Amsterdam zoo produced embryos
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Boa Constrictor Gives Birth to Remarkable Fatherless Offspring ­ 80beats : 80beats
parthenogenetically, but they were not allowed to develop so we do not know if they were truly
viable. [New Scientist]
Now the researchers are left with a question: Why would the boa constrictor reproduce this way if it
didn’t need to? Despite the fact that there were males aplenty with whom to mate, the female reproduced
twice through parthenogenesis. But reproducing this way is generally a last­ditch method—and one that
diminishes genetic diversity.
“This female has given birth to sexually produced babies in the past, and only in years that she was
housed with males has she produced offspring,” Dr Booth explains. “It appears that some interaction
with a male is required. However, why she does not utilise his sperm is at present unknown.” [BBC
News]
Related Content:
80beats: Female Shark Gets Pregnant on Her Own, No Male Required
Discoblog: The Science of Virgin Birth
Not Exactly Rocket Science: Virgin Birth By Komodo Dragons
DISCOVER: Why Bother With Sex?
DISCOVER: The Real Dirty Secret About Sex
Image: Warren Booth
CATEGORIZED UNDER: LIVING WORLD
MORE ABOUT: ASEXUAL REPRODUCTION, CHROMOSOMES, REPTILES, SEX & REPRODUCTION, SNAKES
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