Cloning normal for some animals

THE NATURAL VIEWPOINT

It may take two to tango, and two to produce a baby, but a surprising

number of animals, including some local ones, have other ways to make

the next generation. In our tide pools, anemones of either sex can

simply split in two and become two new identical animals, in a

process that echoes how plants clone themselves.

More common among animals are situations where there is no male

involved in reproduction. Only the female is needed, producing eggs

that develop spontaneously, without waiting for a sperm to add its

genes. Biologists call this parthenogenesis, or virgin birth. The

offspring are all identical to the female and carry only her genes,

so it’s cloning.

Aphids that suddenly appear all over the rose bushes in spring are

reproducing by parthenogenesis. It’s a huge advantage when finding a

mate is difficult, and it’s a timesaver that allows the aphids to

produce large numbers of offspring quickly to take advantage of a

good food supply. Cloning is not instant reproduction, of course; it

does not shorten the time needed for the young aphids to mature.

Years ago, San Francisco writer David Gerrold created for “Star

Trek” prolific furry aliens called Tribbles that reproduced by

parthenogenesis so fast they threatened the food supply.

Unfortunately, it wasn’t an entirely fictional scenario. The New

Zealand mud snail, a tiny snail under 1/8-inch long, multiplies like

crazy in rivers and lakes. It’s been invading the western U.S. since

1980 -- an enormous population growth spurred by the ability of

unmated females to each produce over 100 live offspring.

Partheno-genesis is very useful to invading species, because it takes

only one individual to start a whole new population.

Closer to home are two local species of long-tailed lizards, the

Western Whiptail and the Orange-Throated Whiptail. These hyperactive

lizards seem to be constantly on the move, searching under coastal

sage shrubs for insects.

Of the 45 species of whiptails in the New World, 15 have no males and reproduce only by cloning. Although our local species have both

males and females, a related lizard in Colorado, the Plateau

Whiptail, has only females. They lay eggs which develop and hatch

into clones of their mother.

Interestingly, although they’re all females, the lizards still

need to pair up and go through courtship before one of them lays

eggs. Then they switch roles and the other one lays eggs. This

suggests that if a male appeared, the female could mate “normally.”

It might be a backup reproductive system in times of environmental

stress or rapid change, when new genes are needed in a hurry.

Compared to these other animals human cloning is not so strange;

most of us already know one, more likely two, human clones. They were

the kids in first grade who dressed alike, and drove the teachers

crazy because no one could tell them apart. * ELISABETH BROWN is the

president of Laguna Greenbelt, Inc.