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Co-opulation: Sometimes It Takes More Than 2 to Tango [Slide Show]

How insect sperm team up to navigate complicated female reproductive tracts
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STYLE ROD:

Some species, such as the whirligig beetle ( Dineutus assimilis ), produce sperm that are embedded within a stiff rod. The sperm cells detach from the rod once inside the female reproductive tract. "We have no idea what function the rods serve, if any," says Dawn Higginson, a scientist at the University of Arizona, who researches sexual selection insects.....[ More ]

UNDULATING MEMBRANES:

The sperm of some species use undulating membranes instead of whiplike tails, or flagella, to get around. The membranes are typically thin flaps of plasma membrane, although thicker membranes may contain cytoplasm.....[ More ]

HOOK HEADS:

Head modifications like the apical hooks shown here in the sperm of the common house mouse ( Mus musculus ) tend to be found in species where the sperm of several males doggedly compete with each other to reach the unfertilized egg.....[ More ]

MANY TAILS:

The sperm of the Darwin termite ( Mastotermes darwiniensis ) was, in 1978, the first animal species that was discovered to have multiple tails, or flagella. Each sperm has approximately 100 flagella that are "feebly motile." The adaptive significance of having so many tails is unclear.....[ More ]

NONSWIMMERS:

The sperm of Acerentomon microrhinus (a hexapod insect) lack the whiplike tail common to other species' sperm, and are immobile. In other species, sperm cells without tails take disk-shaped, pincushion, and amoeboid forms.....[ More ]

SIZE MATTERS:

At six centimeters long, the tangled sperm of the fruit fly Drosophila bifurca is one of the longest sperm cells on Earth, and it is typically 20 times longer than the fly itself. The sperm balls unravel after insemination and straighten out inside the female's sperm storage organ, says Scott Pitnick, who studies sexual selection at Syracuse University.....[ More ]

SPINNERS:

The sperm of Ptinella aptera beetles are twice as long (but much thinner) as the male itself, ringing in at 1.4 millimeters long. Zoologist Victoria Taylor from the University of Oxford was one of the first to examine Ptinella sperm in 1982.....[ More ]

CORKSCREWS:

The sperm of the Japanese green tree frog ( Rhacophorus arboreus ) is wound into 20 counterclockwise coils. In the lower portion of the sperm (pictured), wide coils that contain the cell's genetic material surround inner coils that support the acrosome—the sperm head that penetrates the ovum during fertilization.....[ More ]

ROULEAU YOUR BOAT:

Sperm of the beetle Hydrovatus pustulatus have a different way of stacking together. Seen here, the sperm swim through a female reproductive tract in "rouleau" formation (from the French for roll, as in a roll of quarters)—the tip of one sperm head slips into a hooded portion of another, forming lines of two to 25 individuals.....[ More ]

TWO OF A KIND ... OR NOT:

The diving beetle Hygroutus sayi produces two kinds of sperm: one has a broad head and a short tail, and the other has a stringy head and a long tail. To build the form shown here, hundreds of broad-headed sperm stack together into the backbone of the filament, and hundreds more stringy sperm attach to it and provide locomotion.....[ More ]

TWO HEADS ARE BETTER THAN ONE:

The sperm of the diving beetle Graphoderus liberus are cemented together into pairs or into aggregates of up to 20 sperm. Working together may help the sperm to anchor in the female’s reproductive tract.....[ More ]

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