Many of nature’s greatest wonders are about sex. It is impossible not to be
astonished by the mating display of a male peacock. Plants are equally remark-
able: the flowers of an orchid are to the plant what the peacock’s feathers are
to the bird.
Animals and plants reproduce in a staggering diversity of ways (FIGURE 10.1).
Many species are hermaphroditic: each individual has both male and female
gonads, and mating involves exchanging eggs and sperm (in animals) or mutual
pollination (in plants). When a pair of leopard slugs mate, their intimate moment
begins as they hang together from a long thread of mucus (see Figure 10.1A).
Each of them extrudes its penis, and the two fertilize each other’s eggs simulta-
neously. Some hermaphrodites, like the cactus shown in Figure 10.1C, dispense
entirely with the complications of mating by simply fertilizing themselves.
The slipper shell is a snail with the provocative name Crepidula fornicata that
lives in stacks of several individuals (see Figure 11.14C). A young snail settles on
the top of a stack and matures into a male. All the snails beneath him in the stack
are also male except the one at the very bottom, which is female. When she
dies, the male immediately above her, which is the largest and oldest male in
the stack, changes sex to become the new female. Other species that switch sex
include the famous clownfishes (see Figure 10.1B). Like the slipper shell, clown-
fishes live in groups that consist of a single female and several males. When
the female dies, the most dominant male changes sex to become the group’s
female.10
Courtship displays provide some of the most spectacular and unex-
pected sights in nature. This is a male yellow-crowned night heron
(Nyctanassa violacea).All About Sex
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