Re: Are there animals that can change their gender.

Hello Patty,

The short answer to your question is "Yes!"  But I suspect that you want 
more information, so let me elaborate.

Animals that function as both males and females, whether at the same time or 
at different times, are called hermaphrodites.  Hermaphrodites can be 
divided into two groups:  simultaneous hermaphrodites function as males and 
females at the same time; sequential hermaphrodites function first as one 
sex, then change to the other.  And the sequential hermaphrodites can be 
either protandrous (male first) or protogynous (female first).

Now let's talk about specific examples.  There are many invertebrate animals 
that are sequential hermaphrodites.  One of my favorite stories is that of 
Crepidula fornicata, a little slipper-shell limpet.  These limpets live in 
stacks of up to 5 on the shells of other snails.  The oldest (and largest) 
animal is at the bottom of the stack, and is a female.  The ones on her back 
tend to be males.  If the oldest one dies or gets knocked off, very often 
the whole stack dies with her.  But, if one of the small males manages to 
stay attached to the snail shell, he will develop into a female, and others 
will stack on her back.  This is an example of protandrous hermaphroditism.

There are some tiny shrimp-like crustaceans called tanaids that inhabit the 
mudflats near where I live.  These animals start life as females, and only 
the largest individual is a male.  The male mates with many of the females, 
and when he dies, the next largest individual (female) develops into a male.  
This is an example of protogynous hermaphroditism.

Among the vertebrates, sequential hermaphroditism occurs in some groups of 
fish.  The sheepshead is a fish that lives in kelp forests in California.  
They start off life as females, and only the largest ones are males.  When 
the male dies, one of the large females in the group develops into a male.

This is probably more information than you want, but I wanted to be sure to 
answer your question thoroughly.  Thanks for asking the question!

Allison J. Gong
Mad Scientist