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]
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.
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Dawn Higginson/PNAS
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....[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. In other species with dimorphic sperm, non-fertilizing sperm may be involved in providing nutrients to the egg, disabling the sperm of other males or interfering with the female's ability to mate again by clogging her reproductive tract.
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Dawn Higginson/PNAS
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]
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. In other species, rouleau trains contain up to 1,000 sperm.
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Dawn Higginson/PNAS
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]
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. The whipping of the sperm's tail end causes it to move in a counterclockwise spiraling movement.
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Mizuhira et al./Journal of Ultrastructure and Molecular Structure Research
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]
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. They move "quite rapidly, coiling around one another in the spermatheca," she wrote. "They are not restricted to movement in one direction and appear able to swim backwards and forwards with equal facility."
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Taylor et al./Tissue and Cell
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....[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. Why the sperm are so long is a mystery, but some studies have found that long sperm are associated with long female reproductive tracts; in D. bifurca, the female’s sperm storage organ is eight centimeters long.
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Romano Dallai/Nature
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]
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. These forms could theoretically only evolve in species where females are monogamous and there is little-to-no competition between the sperm of different males.
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Dallai et al. 2010/Zoomorphology
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....[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.
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Baccetti & Dallai 1978/Journal of Cell Biology, and Riparbelli et al. 2009/Cell Motility and the Cytoskeleton
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]
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. What function they serve is unknown but in some rodent species, the hook allows sperm to conjugate into rouleaux (see slide 2). It is also possible that apical hooks are related to motility or sperm–egg interactions.
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Reproduced with permission from The International Journal of Developmental Biology (1995) 39: 675-685.
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]
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. Undulating membranes are commonly found in frogs, fish and salamanders, and may enhance swimming capacity
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Lee & Jamieson 1992/Zoologica Scripta
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....[More]
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.
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Dawn Higginson/Biological Reviews
YES! Send me a free issue of Scientific American with no obligation to continue the subscription. If I like it, I will be billed for the one-year subscription.
Most unbred animals (English sparrows, for example) all look alike to
me. People, of course, not so. Do I just not recognize the traits that
distinguish one animal from another, or do they really lack the
individual distinctiveness of humans?
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Have Some Sugar with Your Protein
1 Comments
Add CommentI'm sure that once a right-wing Republican reads this article, he'll want to douse all the bugs with DDT.
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