from male to female in 30 seconds

Hermaphrodism is relatively common among forms of marine life

image found here

Take nudibranchs. These snails-without-shells, also called sea slugs, are true hermaphrodites, having male sex organs on one end, female organs on the other. When these creatures have sex, they line up end to end, sometimes several individuals at a time, creating a kind of conga-line orgy.

alabaster nudibranch found here

Fish equipped with both testes and ovaries are called simultaneous hermaphrodites.

One such type of sea bass spawns about 14 times a day. About half the time, the individual releases eggs; the other half sperm. This fish can switch from one to the other in 30 seconds.

black sea bass (1900) found here

As these sea bass grow older, their female gonads grow larger, causing the fish to release more and more eggs and less and less sperm. This probably increases the species’ reproductive success rate since most eggs get fertilized, but most sperm don’t link with eggs.

black sea bass found here

Other simultaneous hermaphrodite fish grow more male tissue as they age. Usually, these fish keep changing, eventually becoming all male. Fish that change sex completely like this are called successive hermaphrodites. Wrasses, parrotfish, some gobies and several other reef fish are in this group.

tattooed parrotfish found here

Successive hermaphrodites perform sex-change acts in a variety of ways, depending upon the species and circumstances.

In clownfish (those cute orange fish that live with anemones), only the largest female and male of a group reproduce. If this large female dies, her mate becomes a female. Then the largest juvenile in the family moves up, becoming the new male.

clownfish found here

Other fish make more than one sex change. In Japanese reef gobies, a female in a group will become male if the dominant male leaves. If a larger male joins the group, the changed fish reverts to her former female self. This sex change takes only four days.

reef goby on brain coral found here

A two-male species, the midshipman of Northern California, has been studied extensively. Type I males take longer to mature, but grow bigger and develop strong vocal systems for courting.

These males, whose gonads account for only 1 percent of their weight, hum to attract females to their carefully built nests.

midshipman found here

Type II males, however, mature early. Their gonads account for a whopping 9 percent of their body weight. (This would be 16 pounds of testicles on a 180 pound man). And humming to attract mates? Forget it. These males use invasion to get mates, stealing both nests, and the females in them, from type I males.

Hermaphrodite fish are on the rise, thanks to the birth control pill and other natural and unnatural forms of estrogen that have made their way into the water. It is believed that it is the female estrogen hormones released from sewage treatment plants that are responsible for the feminization of wild fish.

image found here

Published in: on September 21, 2011 at 7:55 am  Comments (61)  
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the world is awash in sperm

The Navanax sea slug is a sort of legend in its own lifetime according to zoologist Janet Leonard. It’s known as the “if you can’t eat it, mate with it” slug.

Navanax is a hermaphrodite: like many other species, it has the anatomy and the ability to be either male or female. And Navanax gets to choose between the genders over and over again–it never has to settle for one or the other.

The name of the mating game, after all, is to pass along the most DNA, and sperm cells, which are small, require far less energy to make than do the much larger eggs. Eggs are expensive, but the world is awash in sperm, says evolutionary biologist Eric Fischer. Accordingly, females make many fewer eggs than males make sperm. And while males try to spread their inexpensive, abundant sperm far and wide, females try to invest their precious and limited store of eggs carefully.

Janet Leonard has been peeping in on and videotaping Navanax sex for more than a decade now. And, she reports, it’s a curious affair. Every Navanax comes equipped with a penis on the right side of its head; a few inches behind is a genital slit that leads to an ovary. Mating begins when one slug follows the trail of another and comes up from behind. The first slug pokes its head under the other’s tortilla of skin, twisting around to position its penis near the other’s genital opening. The second slug responds to this courting by raising its tail and unwrapping the sheath of skin around its body. After the sperm has passed from the first animal to the other, the female swings around and begins nudging its penis toward the genital slit of the male. If all goes well, they exchange jobs.

The animals keep trading roles, four, five, or more times. Fittingly, it’s a sluggish affair. One round of copulation, Leonard sighs, can take five hours. One of the first things you learn working with these animals is patience.

Often chains of three or more mating animals will form with those in the middle acting as male and female simultaneously.

This is a video of a Navanax biting an Aplysia, not having sex. I’ve included it because the two researchers making the video get so damn excited… “Hold on, Lafonda… this is a beautiful thing… atta girl”


Published in: on March 8, 2010 at 7:12 am  Comments (37)  
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