Tuesday, February 26, 2008

The Zombie Snail

“A shade-loving snail has been invaded by worms. These parasites take over the snail’s brain, and push into his tentacles, transforming them into swollen, colorful, pulsating targets…”

This parasite is apparently called Leucochloridium paradoxum.

There are many other “mind-controlling” parasites such as the Spinochordodes Tellinii which infect grasshoppers and forces them to drown themselves. The animal develops inside land-dwelling grasshoppers and crickets until the time comes for the worm to transform into an aquatic adult. Somehow mature hairworms brainwash their hosts into behaving in way they never usually would – causing them to seek out and plunge into water.


Once in the water the mature hairworms – which are three to four times longer that their hosts when extended – emerge and swim away to find a mate, leaving their host dead or dying in the water.

Sunday, February 24, 2008

The Scotch-tape Test

The adult worms live in the colons (large intestines) of human children and apparently feed on human fecal matter.

When adult male and female worms copulate, each female pinworm produces about 10,000 fertilized eggs. At night, the pregnant female migrates from the colon, out through the child's anus and onto the skin of the buttocks. There she violently expels all of her eggs and dies. Some of the eggs become airborne and land elsewhere in the child's room, but the great majority of the fertilized eggs stay on the skin of the child's buttocks. The eggs mature within six hours of being laid.

The adult worms and the eggs on the skin of the buttocks can cause intense itching in the child. When the sleeping child scratches, the eggs often get on the fingers and under the fingernails. If the child sucks his or her thumb or otherwise brings his or her hand to the mouth (perhaps while eating breakfast), the pinworm eggs are swallowed. They usually hatch within the small intestine and mature there. When they become adults, they move to the colon where they take up residence. The entire life cycle lasts four to six weeks.

NEJM -- Enterobius vermicularis -- Data Supplement - Video

How did sex begin?

We've seen that sex is central to evolution, that it generates diversity, that despite the trouble it causes, it's something most of us can't live without, that abstinence almost always leads to extinction. But how did sex begin?

One idea is that gene exchange [among early microbes similar to our modern day bacteria] facilitated the repair of damaged DNA: an intact string of DNA received from a partner could perhaps be used to replace or repair genes that had been broken.

A second, more exotic idea is that sex was simply infectious. In other words, it arose because a segment of DNA promoted gene exchange in order to spread itself through the population. To use an analogy, it's as though the common cold caused humans to be promiscuous - an effect that would clearly enhance its transmission. One reason a modern bacterium will be moved to have sex is because it's become infected with a particular segment of DNA known as the F plasmid. An individual who's got the F plasmid is then driven to mate with an individual who hasn't, and so spreads the sex habit around.

Why do Males Exist? An Unanswered Question in Science

Mysteries of the male

Why do males exist? If you look at any standard biology textbook, you will probably read that the point of having males as well as females is to promote variation by the exchange of different mutations, and hence to increase the chances of species survival. Unfortunately, most evolutionary biologists stopped believing in this explanation over 20 years ago. From a reproductive point of view, no individual is interested in anything beyond donating genes to the next generation, while species survival happens more or less at random, according to the whims of climate and geology. You don't actually need sexes in order to mutate and produce variation. In any case, most mutations have no effect, or mainly deleterious ones. John Maynard Smith talks of ‘the twofold cost of males’. Firstly, it is incomprehensible that any female should want to chuck away half her genome. Secondly, the males of many species are useless at doing anything except sitting around, getting fat at the females’ expense, and—in the words of Richard Dawkins—duffing up other males. Among some animals, such as elephant seals, the vast majority die as wasteful, disappointed virgins.

Given the cost of males, it is perhaps not surprising that there are at least 40 species where the female kills the male during or after sex. In the case of the praying mantis, she literally bites his head off as part of foreplay, and he carries on in a delighted reflex of posthumous orgasm. Females of other species are equally imaginative: male scale insects have been demoted to microscopic excrescences on their females’ legs, while female angler fish carry their mates on their backs as tiny dwarves. More pertinently, there are many effective ways of reproducing apart from sex as we understand it. These include simple division and gene exchange, which have served prokaryotes so well that they have produced the longest-enduring of all species on the planet, as well as comprising the greatest number of species, and probably constituting most of the biomass as well.

Among other organisms, alternative methods of reproduction include budding, hermaphroditism and isogamy (i.e. two individuals, not distinguished as males and females, combining their genes). There are asexual variants among all sorts of creatures, including jellyfish, dandelions, lichens and lizards. Of the creatures who do reproduce sexually, some species have two sexes, but others have three, or thirteen, or 10 000, if you are a fungus. Many species alternate between sexual and asexual reproduction, either on a regular basis or occasionally, as the circumstances require. Bdelloid rotifers—tiny invertebrates who live in drains and puddles—went off sex about 80 million years ago, and have cheerfully diversified into several hundred species since then, without regaining the inclination. Maynard Smith described them an ‘an evolutionary scandal’.

The various current theories about why males evolved and still remain in existence are nicely set out in Matt Ridley's book ‘The Red Queen’. They are also covered in Olivia Judson's racy and wonderfully informative book ‘Dr Tatiana's Sex Advice to All Creation’. Different theories rejoice in names like Muller's ratchet, Kondrashov's hatchet, and the eponymous red queen of Ridley's book (named after the character in Alice in Wonderland who perpetually runs without getting very far because the landscape moves with her). This last theory seems to be the front runner at the moment. It is based on W.D. Hamilton's idea that sex is part of a continual race to outwit external pathogens. What is clear, however, is that the consensus that existed on this topic from Darwin until the 1980s has totally broken down. The purpose of males has instead become one of the biggest unanswered questions in science. My guess is that we will eventually come to understand fertilization by males in a similar way to how we now understand the appearance of ancient autonomous organisms such as mitochondria or chloroplasts in the eukaryotic cell. In other words, we will see it as an evolutionary compromise poised half way between invasion and alliance, parasitism and symbiosis, or genetic rape and informed consent. There is already much evidence to show how females resist the process physiologically (for example by stripping male gametes of all extra-nuclear DNA) and how males try to control reproduction against their females’ will (for example, by killing off competitor sperm or genetic material in the female genital tract, or alternatively killing the competitors and their offspring directly).

If the status of males in evolutionary terms is an equivocal one, the consequences of sexual dimorphism are not reassuring for males either. In a review of the evidence relating to human males, my colleague and mentor Sebastian Kraemer has set out the scale of the problem. Throughout life, men are more vulnerable than women on most measures. This starts with the biological fragility of the male foetus, leading to ‘a greater risk of death or damage from almost all the obstetric catastrophes that can happen before birth’. If they survive these catastrophes, boys then have a far greater susceptibility to developmental disorders than girls. These are magnified in turn by our cultural assumptions about masculinity, and by our low expectations of males. The toxic interaction of biological and social ingredients shows itself in far higher rates of suicide and deaths through violent crime. Males also do worse in (among other things) scholastic achievement, emotional literacy, alcoholism, substance abuse, circulatory disorders, diabetes, and of course in longevity. Kraemer looks at how male disadvantage is ‘wired in’ from infancy and persists to the grave, but he suggests that we shouldn't necessarily conclude that maleness is a genetic disorder. Instead, he argues, we should show more curiosity about the reasons for boys and men being so vulnerable, and should pay more attention to redressing this in child-rearing and in medicine.

It may be no coincidence that questions about the ‘raison d’etre’ for males, and concerns about their relative deficiencies, should have arisen at this point in history; enough of the relevant information behind them would probably have been available to an observer in Darwin's time. The recent appearance of these scientific preoccupations may well be the consequence of understandable male anxiety. In the last few generations of our species, female control over fertility has developed at a rate so phenomenal that it may justify comparison with the sudden emergence of male-female reproduction itself, around a thousand million years ago. In evolutionary terms, it has taken only the twinkling of an eye from the introduction of the vaginal diaphragm and the contraceptive pill in the middle of the last century, to the widespread use of frozen sperm and extracted eggs, and hence to the actualization of human oocyte cloning. Within the span of just one lifetime, women have advanced through several enormous stages of biological liberation and have reached the threshold of elective parthenogenesis.

Assuming that the minor technical problems of gene damage during cloning can soon be overcome, and that legal constraints will in time be removed—assumptions that seem reasonable by any standard—it is possible that the women of our species will soon have the overall choice of doing with very few men, or with none at all. If, in the mean time, they can prevent males from destroying any environment in which to survive, they might be forgiven if they choose to follow the path that has already been pioneered by the bdelloid rotifers. Attempts to understand maleness or to redress its difficulties will then become entirely academic.

QJM: An International Journal of Medicine

Forsten's tortoise (Indotestudo forstenii)

Really, really funny.

Hermaphroditic Penis Fencing

Flatworms penis fencing

We often think of animals hunting and fighting for food, but many flatworms appear to hunt and fight for mates. Each worm is hermaphroditic, containing both ovaries with eggs and testes with sperm. Some even have two penises and one or more genital pores for receiving a unique, two-tailed sperm delivered during copulation.

Using new camera technology, Marine Biologist Leslie Newman of Australia's Southern Cross University participated in filming the marine flatworm Pseudobiceros hancockanus engaging in some odd reproductive behavior -- referred to as penis fencing.

During penis fencing, each flatworm tries to pierce the skin of the other using one of its penises. The first to succeed becomes the de facto male, delivering its sperm into the other, the de facto female. For the flatworms, this contest is serious business. Mating is a fight because the worm that assumes the female role then must expend considerable energy caring for the developing eggs.

The Shape of Life . The First Hunter | PBS

(Article found at The Shape of Life)

Gay Penguins! Hide the Children!


Remember the infamous gay penguin scare of 2006, when it was revealed that gay mating behavior among penguins was not at all unusual? It wasn't just the two male penguins at the Central Park Zoo taking care of an egg and acting as a family, it turned out that this sort of thing was commonly observed in penguin populations in captivity all over the world. Well a couple of authors wrote a children's book about it and people are trying to ban it from libraries all over the country.

The latest instance is in Loudon County, Virginia, where a parent is complaining and trying to get the book removed from an elementary school library, presumably on the theory that if their child happens to stumble upon the fact of the existence of gay penguins, they will turn out to be interior decorators or gym teachers.

"And Tango Makes Three" by Peter Parnell and Justin Richardson is based on the true story of two male penguins who took turns sitting on an orphaned egg at the Central Park Zoo. In the story, the penguins, Roy and Silo, start their family when the chick, Tango, is hatched.

A parent at Sugarland Elementary in Sterling filed a request with the school principal that the book be reviewed. The principal and several staff members deemed the book appropriate for general circulation.

The parent appealed the school's decision with the Loudoun County Public Schools administration. According to David Jones, the LCPS library media supervisor, a district-level committee was formed with teacher, parent, school librarian and administrative representatives who reviewed the book and offered a recommendation to Superintendent Edgar B. Hatrick III, who ultimately decided on the book's status.

Dr. Hatrick determined that "And Tango Makes Three" should be taken out of general circulation at the elementary level and placed in each school's professional library. Teachers may reference and share the book with students at their own discretion. Children and parents may not check the book out of the library.

The American Library Association says that this book is one of the most challenged books of the last couple years all over the country. All because there are people ridiculous enough to believe that if you even acknowledge the existence of gays, whether human or some other species, their kids will turn out to be gay. I love the smell of irrationality in the morning.

(Article found at Science Blogs)

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(Roy and Silo, a now famous same-sex penguin couple who successfully raised a penguin chick, Tango)

Experimenting with a Four-headed Penis


A new paper about the reproductive behaviour of the spiny anteater, to be published in the December issue of American Naturalist, makes for fascinating - if slightly disturbing - reading.

The spiny anteater (Tachyglossuss aculeatus) is a primitive mammal with an unusual four-headed penis. The animal is difficult to observe in the wild, and does not readily copulate when in captivity, so exactly how the male uses its penis was a mystery.

Stephen Johnston of the University of Queensland and his colleagues obtained a male spiny anteater which regularly produced erections when handled during public viewing sessions at a zoo, and had been "conditioned to develop an erection to the point where it would ejaculate." Johnston's team were therefore able to make the first observations of the animal's erection and ejaculatory mechanism.

They discovered that the anteater's ejaculatory mechanism is very strange - it is unique among mammals, and actually cloesly resembles the form of ejaculation observed in some reptile species. Further, they found that the anteater's sperm forms bundles which consist of up to 100 cells (above right).


The spiny anteater's penis is bilaterally symmetrical, and the glans is subdivided into four "rosettes", all of which remain displayed during the early stages of an erection. But as the erection continues, the two rosettes on one side become engorged with blood, and the two on the opposite side retract.

Because the two unused rosettes retract, the erection is symmetrical in appearance (right). The erect penis - which is one-quarter the anteater's body-length - is therefore fully compatible with the female, which has only two reproductive tracts.

Observation of consecutive ejaculations showed that the left and right sides of the penis are used alternately. But it remains whether or not ejaculation becomes restricted to one side of the penis during copulation; it is possible that sperm travels to the vas deferens on the unused side of the penis without being discharged.

When semen samples were examined using a scanning electron microscope, they were observed to contain bundles of up to 100 spermatozoa. This apparently increases the motility of the cells - although the precise velocities were not measured, large sperm bundles were found to swim more quickly than smaller bundles or individual cells.

Female anteaters sometimes copulate with up to 11 males in quick succession, so bundling may have evolved as a form of sperm competition. Alternatively, it could be a means of storing sperm within the female reproductive tract, or of preventing the cells on the inside of the bundle from maturing before fertilization can occur. A better understanding of sperm bundling should be possible now that the researchers have the ability to collect semen samples regularly.

This is the first time such ejaculatory behaviour has been described in a mammal. The ejaculation mechanism of the spiny anteater is reminiscent to that of the squamate reptiles (lizards and snakes), which have two alternately-used hemipenes that otherwise remain inverted inside the tail.

This study therefore supports the theory that monotremes (the mamalian order to which anteaters belong) have a close evolutionary relationship with reptiles. And further studies of the spiny anteater's reproductive behaviour may provide useful information about how all mammals evoloved.

(Article from Science Blog)

Did T.rex have a penis?

Evolutionary biologist Olivia Judson is my hero. She is the author of “Dr. Tatiana’s Sex Advice to All Creation: The Definitive Guide to the Evolutionary Biology of Sex,” and also writes a blog for the New York Times. The following article is from her blog called "The Wild Side," and asks the burning question, "did dinos have penises?"

First, she describes why we have not yet answered this question based on good 'ol fossil evidence:

"The reason we don’t know whether T. rex had one is that the organ is generally too soft to leave a fossil trace. (There’s an exception to this: some mammals have a bone in their penis, the os penis or baculum. This can fossilize. Humans are unusual among primates in not having one; in case you’re wondering, it’s not clear whether the bone plays a role in maintaining erections.)"

To summarize the article: yes, she thinks they did. She bases her opinion on a few key evolutionary pieces of evidence. First, the two extant groups most closely related to dinosaurs are the crocodiles and birds.

Male crocs (of Class Reptilia) have a penis they keep tucked inside their cloacae. Unlike mammalian penises, that of the crocodile transports the sperm along an external groove, as opposed to through an internal tube.

The other group related to dinosaurs is the birds (of the violently disputed Class Aves). Birds can be divided into two main groups: those of the palaeognathous and those of the neognathous.

"The palaeos comprises the big flightless birds such as ostriches, emus, rheas, and cassowaries, as well as kiwis and an obscure (but flying) group of south American birds, the tinamous; the neos covers everything else. The palaeos have penises; like crocodiles, they keep them tucked into their cloacae. Again like crocodiles, the organ has an external groove for sperm. What’s more, the lineage leading to the other endowed birds, the ducks, geese, and swans, appears to have split off from that of the other neos relatively early."


All of this informations points to the conclusion that the ancestor of all birds in fact had a penis. At some point early in the evolution of neognathous birds, the penis was lost (and regained in many types of waterfowl in what probably was an independent event. Waterfowl often mate in the safety of the water, and a penis assists in steering the sperm and balance). So crocodiles have one, and ancestral birds probably did, and since the two groups have a very similar genital morphology - it may be safe to infer that T.rex probably had one too!

The Sex Lives of Birds

Boy sees girl, girl sees boy. Boy and girl meet, date, and become a pair. They may eventually go on a honeymoon and raise a family.

As it is with people, birds also go through similar steps to ultimately produce offspring. Some species of birds remain together after copulation (sex), sharing in the incubation of the eggs, feeding and raising of the young birds, as well as staying together after the breeding season. Other types of birds are briefly attracted to each other only for the purposes of fertilizing the eggs, with the female incubating and rearing her family by herself.

During breeding season, it is usually the female birds who are wooed and courted by the males. These males have established their territories and work hard to attract a mate.

The male Mockingbird will sing his verses to all who can hear, sometimes into the night, advertising that he is certainly available as a husband. American Robins are another bird that will sing love songs to woo the females.

Male peacockMale Peacocks strut about, fanning their gorgeous multicolored tail feathers. As gorgeous as peacocks are, the male Bird of Paradise is even more spectacular! They grow long iridescent tails that look as though they would impede his flight. When a female comes closer to hear his song better, he will clutch his perch tightly and hang upside down so his prospective mate can better see his tail.

The male Bowerbird builds his lady a room of sticks and leaves, furnishing it with objects that he feels a female will love, such as a pretty stone, flower petals, shells, pods, and other love items.

During breeding season, the male Magnificent Frigatebird's throat turns bright red. When a female comes near, he puffs it up, showing her his very sexy throat which she may find very alluring!

The Great Egret grows long wispy feathers that he fans and displays to any female who saunters by. Male hummingbirds perform swooping aerial dances for the females watching. Northern Harrier males will perform dances in the sky consisting of huge U-shaped swoops.

The male Prairie Chickens meet in a clearing, called a lek, where they raise the feathers on their neck and head to resemble ears, fan their tails, drop their wings to the ground and parade around. They fill air sacs located on either side of their head, then force out the air, producing booming love songs, while they strut around for the ladies' benefit and approval.

Once a female bird has shown that she is interested, the male may do a bit of courting to further entice her.

Just as a human male may take his girlfriend out to dinner, quite a few male birds, including the Northern Cardinals and Blue Jays, feed tender morsels of food to their ladies. Sometimes the females will assume a fledgling begging posture while being fed. Other birds, such as the Roadrunner, may bring food to the female just before mating. Species of birds that feed their girlfriends usually are the guys who stick around to help feed and raise the young chicks.

After dinner, what about going dancing?? Whooping Cranes and Sandhill Crane pairs perform dances together, bowing, jumping, turning and perhaps even presenting a twig to the other. Other pairs of cranes may join in this contagious and joyful dance. Roseate Spoonbills may grasp each other's bill in an amorous clench. And don't forget the Western Grebes who dance across the water, side-by-side, with their wings outstretched.

Pairs of Red-winged Blackbirds fly through the air together, with the male singing, raising his red epaulet feathers, and chasing the female in this courtship ritual. He may even grasp her rump and cause both to crash to the ground, hopefully unhurt, all in the name of love.

Many species of birds, once bonded as a pair, will perch close together, preen each other, and rarely leave each other's side. Ah, love is in the air!

The Honeymoon

Mr. Bird has found his season's love, and she loves him back. What causes these birds to form these bonds in the spring and summer, not when it is cold and snowy, nor while they are migrating?

Hormones from the pituitary gland are the answer. During breeding season in response to the hormones, the male's testes become several hundred times larger than normal to produce sperm, with the left testis usually larger. The female bird's ovaries also enlarge during breeding season to produce the ovum. Female birds usually only have one functional ovary, the left one.

In birds, an ovum is fertilized in the female bird's oviduct by a sperm cell from the male bird. Once fertilized, the ovum becomes the nucleus of the egg. The egg, that has its own food source, the yolk, will be laid by the female into her nest, incubated, and then the baby bird will hatch.

But how does the sperm from the male bird get into the female? How can they have intercourse without any external male organs, such as a penis? The male's sperm, produced in the testes, passes to the cloaca where it is stored until copulation (act of sex). The female also has a cloaca that leads from the ovaries. The female bird unfans her tail, moves it to one side while the male climbs up onto her back or gets close to her. Their cloacas are pressed together and the sperm moves from the male to the female. This act is called a cloacal kiss.

The sperm is stored by the female for at least a week, in some species over a hundred days. Then as each ovum from the ovary moves into the oviduct, it gets fertilized with the stored sperm, producing a clutch of many eggs, all with the sperm from that one cloacal kiss.

There are a few species of birds where the males do possess a retractable penis that can be pulled back into the bird. These birds include ostriches, cassowaries, kiwis, swans, geese, and ducks. Since waterfowl sometimes make love while in the lake or pond, the penis helps ensure that the sperm is not washed away by the water.

Sperm can be transferred from male cloaca to the female in a blink of an eye - less than a second. Some birds seem to want to linger longer though, sometimes having sex for more than an hour! And, although it is not necessary to copulate frequently since the sperm is stored within the female, remember those hormones are still making the birds excited. Many pairs of birds will mate numerous times within a few days.

Gulls mating

Gannets mating

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Mating Variations

Most of the birds you see in your backyard are monogamous, at least for that breeding season. The cardinals, the jays, the robins stay together as a pair, helping with the nest building, the feeding of the young and perhaps even with the incubation of the eggs.

Some birds enjoy having more than one spouse. Polygyny is when a male bird has multiple wives, such as the Northern Harrier and the Eastern Meadowlark. It occurs in species where there is abundant food (male does not need to help the female feed the young.) Polyandry is when the female has multiple husbands, such as the Spotted Sandpiper who may have four husbands. And then there is is polygynandry where both the female and male have multiple spouses.

The Red-winged Blackbird male has an avian harem with up to 15 females in his territory. These females find that nesting close to each other helps deter predators as long there is a sufficient food supply for all of them.

Although two birds may be paired together for the season and may have already produced a clutch of eggs, either spouse could have wandering eyes and commit adultery. Tree Swallows, the Red-winged Blackbird females, some woodpeckers, some buntings, and even Baltimore Orioles are only a few species that have extra-martial flings now and then.

Some males just entice a female for sex, then leave to find another female to mate. In these cases, the female builds the nest, incubates the eggs, and raises the chicks by herself. Species of birds that follow this pattern include the hummingbirds. However, to feed hungry young birds and defend them from predators it usually takes both parents. Therefore, most birds work with their spouse to ensure that the greatest number of their chicks survive.

Hummingbirds usually allow no other hummer within their territory. They will chase off all other hummers, male or female, who try to feed at "their" flowers or feeders. However, female hummingbirds have been observed being allowed to feed within a male's territory before or after having sex with him.

And then there are the Galapagos Hawks who live in threesomes, one female with two attentive males. She mates with both, although one at a time, and both help her with raising the young hawks. Harris' Hawks threesomes have one male with two females. These threesomes find that life is easier and the chick survival rate higher with three parents.

Divorce and Death

Troubles do arise occasionally in bird pairings, and divorce is not unheard of.

A frustrated pair of birds who are unable to produce any eggs, may "divorce" and go in search of new mates, hoping that with their new lover, a nest full of healthy babies can be raised.

Most birds remain with the same mate throughout the breeding season, although they might have a few extra-marital flings.

Some birds such as raptors, swans and geese, live their entire lives with the same spouse. These birds remain together for years, both migrating back to the same territory each year. Even in species that don't migrate, staying with the same spouse, year after year can be beneficial. The territory is familiar and sources of food are known. Each bird knows the other's habits as well they know their mating will produce offspring.

Once a spouse dies or fails to return to the territory, the remaining spouse will eventually attempt to find a new mate. It is an old wives' tale that the remaining spouse will die of a broken heart.

(Article found at About.com:Birding/Wild Birds)

Zoological Curiosities.

There are just too many fun facts floating around Kingdom Animalia. This blog's purpose is to act as a electronic cavity in which I may pool my findings.