Professor uses DNA clues
in study of egg-eating
fish
By Betsy Osos
Staff Writer
Cannibalism in the fish nest has led one Purdue
professor to probe deeper into the sex lives of wild fish using common
forensic techniques.
Andrew DeWoody, assistant professor of forestry
and natural resources, used genetics to look further into the sex lives
of certain types of fish.
Three types of sunfish and the tessellated darter,
another type of fish, were observed for the study. These fish are external
fertilizers, which means the male builds the nest and waits for a female
to swim by and drop some, or all, of her eggs. The male then fertilizes
the eggs and stays near the nest to protect it from predators.
"Female fish spawn and leave, and provide no parental
care," said DeWoody.
Quite frequently, parasite fish, known to scientists
as satellites and sneakers, will disguise themselves in order to swim
over and fertilize another male's nest. The risk of predators keeps
the nest-tending male from leaving his post. This leaves him with few
resources for food.
DeWoody said, "The male fish will eat some of the
eggs in the nest to satisfy hunger."
This fact led DeWoody and his colleagues to question
the male's ability to distinguish its own kin.
The largemouth bass was also studied during this
project, but unlike most fish, this type is highly monogamous, mating
with only one fish per season. Also, both the male and female bass tend
the nest. Because of this, there was a much lower occurrence of eggs
fertilized by an outside male.
DeWoody and colleagues from the University of Georgia
wanted to see whether the nest-tending males only ate those eggs fertilized
by other males.
"We captured male fish and extracted DNA samples
from fin clips, scales, or liver and stomach tissue," says Mark Mackiewicz,
research coordinator at the Genome Analysis Facility at the University
of Georgia.
DNA testing was performed on about 150 fish and
the fertilized eggs found within their stomachs. The findings revealed
that the males were just as likely to eat their own kin as opposed to
those of a parasite fish.
Since the male fish were unable to determine their
own kin at such an early age in development, DeWoody has decided to
expand his research. Now, he is working to understand exactly which
genes are used in kin recognition and if olfactory senses play a role.
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