It's Alive

Tiny creature, giant sperm

11:20am, July 23, 2012

A dotted line shows the site of the sperm-moving structure called a Zenker organ in this microscope view of a Pseudocandona marchica ostracod. This tiny crustacean, a relative of shrimps and crabs, uses the organ to route extralong sperm.

Crustaceans called ostracods face an unusual challenge: Their sperm can be up to 10 times as long as their bodies.

Admittedly, an ostracod’s body fits on the head of a pin, and the longest sperm filaments stretch only about a centimeter. Still, the mismatch intrigues biologists of a species that would have to produce sperm more than 15 meters long to reproduce in ostracod style. Now, two scientists have tackled the question of how ostracods’ internal plumbing handles such extreme sperm.

Part of the ostracod sperm duct has evolved into a segment called a Zenker organ, toughened with crabshell-like chitin in ornate shapes. Detailed microscopy now suggests how Zenker organs work as pumps for giant sperm, says Shinnosuke Yamada of Shizuoka University in Japan.

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