2015 Photo Contest, Nature, Stories, 1st prize

Mindsuckers

Photographer

Anand Varma

National Geographic

01 August, 2013

Hyalella azteca, a tiny amphipod, lives at the bottom of lakes and ponds. Amphipods that have been invaded by the larva of a thorny-headed worm abandon the dark safety of the depths and swim to the surface. For the amphipod, this journey proves fatal, as it is a favored food of waterfowl, but for the larva (turned orange by pigments taken in from the host’s tissue) it is essential. Thorny-headed worms can grow to maturity only in the gut of waterfowl.

Many parasites not only feed off their hosts, but appear to manipulate the host’s behavior in a way that is advantageous to the parasite’s life cycle. Recent research indicates that this influence occurs at a genetic level—certain parasite genes seem to be able to take control of the host’s brain. Research has shown that in some cases a single parasite gene is responsible for altering the host’s behavior, though in most instances it is thought that the phenomenon is brought about by a combination of genes.

About

Anand Varma

Anand Varma is a freelance photographer and videographer who grew up in Atlanta, Georgia. He started photographing natural history subjects while studying biology at the Universi...

Technical information

Shutter Speed
1/166
Focal length
65.0 mm
F-Stop
11.0
ISO
640
Camera
Canon EOS 5D Mark III

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