Flowers that have both male and female parts

The Description of Flowers

Terms describing flower anatomy

Classical angiosperm phylogeny is based mainly on flower anatomy, and in particular, the arrangement and form of the principle parts. The fruiting body is used as well, but its structure is often apparent in the flowers. More recently, genetic studies have been employed to determine the relationship of various botanical groups to each other. Many parts of the old classification system have proven more or less consistent with these studies, but there have also been a large number of changes, even to large and well studied groups. The changes to the classical system have been far more extensive than in the animal kingdom, where the classical, anatomy-based phylogeny has held up remarkably well. As a result, botanical nomenclature has been undergoing a bit of a revolution in the last two decades, and the process (as of 2009) is still ongoing. A community known as the Angiosperm Phylogeny Group or APG has provided some centrality to this process, but there are many areas where no consensus has been reached. Botany has always been prone to what might be termed “vanity species” with some genera (e.g. hieracium, the hawkweeds) having thousands of specific scientific names. The recent trend has been to recognize certain species as highly variable; but history dies hard, especially for those who discovered and described the “species”.

A flower is the reproductive unit of an angiosperm plant. There is an enormous variety of flowers, but all have some characteristics in common. The definitive characteristic of the angiosperms is the enclosed ovary, which contains and protects the developing seeds. Floral reproduction is bisexual, and flowers have “male” and “female” parts. The “male” or pollen-bearing part is called the stamen, and is composed of the filament and the anther. The “female” or seed-bearing part is called the pistil, and is composed of the ovary, the stigma, and the style. A flower may have exclusively male parts, exclusively female parts, or commonly, both. When there are separate flower types, both may occur on the same plant; occasionally a plant may bear only male or female flowers.

Surrounding the reproductive parts is the perianth, a double envelope consisting of an outer portion, the calyx, which forms the sepals, and an inner portion, the corolla, which forms the familiar petals. There may also be leafy elements, termed bracts, surrounding a flower. Individual flowers are often organized into a larger group or cluster, termed an inflorescence. The stalk supporting a single flower is called a pedicel, that supporting an inflorescence, or an isolated flower, a peduncle.


Anther: The pollen-bearing body of the stamen, usually relatively compact, and supported at the end of the narrow filament. Under a lens, anthers exhibit a wide variety of forms and means of attachment. These characteristics are often important in technical keys for flower identification.
Bract: A leaf-like element below a flower or on an inflorescence. Bracts are typically shaped differently than other leaves on the plant. They are usually green, but occasionally are brightly colored and petal-like.

Calyx: The outer perianth of a flower. The calyx surrounds the corolla, and is typically divided into lobes called sepals. These are frequently green, and reduced relative to the petals, but they can also be large, and brightly colored, resembling petals. In many flowers, the sepals enclose and protect the flower bud prior to opening.
Corolla: The inner perianth of a flower. The corolla typically surrounds the reproductive parts of the flower. It may be continuous as in a petunia, lobed, or divided into distinct petals. In some cases, especially in cultivated varieties, the corolla may be doubled or even further multiplied, producing multiple layers of petals. In other cases, it may be lacking entirely.
Filament: The usually narrow and often threadlike part of the stamen which supports the pollen-bearing anther.
Involucre: A circle or cup of bracts that surrounds and supports the multiple florets of the head in the composite flowers of the family asteraceae. The shape and arrangement of the involucral bracts is important in describing the members of this family.
Ovary: The part of the pistil that encloses the unfertilized seeds or ovules, and that typically develops into a dry or fleshy fruit once pollination takes place. The ovary is generally central to the flower, and supports the other principle parts. Whether they are attached at the top (ovary inferior) or the bottom (ovary superior) is an important anatomical characteristic for classification. Not all “fruits” are mature ovaries; some form from supporting parts of the flower, for example, strawberries develop from the receptacle – the enlarged top of the flower stalk.
Pedicel: The footstalk supporting a single flower in an inflorescence.
Peduncle: The stalk supporting an inflorescence or solitary flower.
Perianth: The technical term for the envelope that surrounds the reproductive parts of a flower. This enclosure is composed of two concentric units, the outer perianth, or calyx which may be divided into sepals, and the inner perianth, or corolla, which may be divided into petals. Either the calyx or the corolla (or both) may be much reduced or lacking.
Petal: A division or lobe of the corolla or inner perianth of a flower.
Pistil: The seed-bearing or “female” reproductive part of a flower. The pistil is composed of the ovary, the style, and the stigma. The ovary contains the developing seeds, and is connected to the pollen-receiving stigma by the style. Flowers often contain a single pistil, but may contain several. Staminate or “male” flowers contain only stamens and lack pistils entirely.
Receptacle: The generally enlarged top of the footstalk, which supports the other parts of the flower. Some “fruits” are enlarged receptacles rather than ovaries.
Sepal: A division or lobe of the calyx or outer perianth of a flower. Sepals are often green, and/or reduced in size, but they can be colorful and petal-like as well.
Stamen: The pollen-bearing or “male” reproductive part of a flower. The pollen is borne on a more or less compact body termed the anther, which is supported by the filament. A flower may have hundreds of stamens, or only a few. Pistillate or “female” flowers have pistils but no stamens.
Stigma: The upper part of the pistil which receives the pollen. The stigma is often sticky, or covered with fine hairs or grooves, or other anatomical features that help the pollen to adhere. It may be cleft into several parts.
Style: The usually elongated part of the pistil that connects the ovary to the stigma.

Hermaphroditic Plant Info: Why Are Some Plants Hermaphrodites

All living beings continue their existence on this earth through reproduction. This includes plants, which can reproduce in two ways: sexually or asexually. Asexual reproduction is when plants are reproduced by offshoots, division or cuttings. Sexual reproduction in plants happens when the male parts of plants produce pollen, which then fertilize the female parts of a plant thus producing seed. In humans and animals, it is quite simple: one being has male reproductive organs, the other has female, and when they join reproduction can occur.

Plants, however, are more complex. The reproductive organs of plants can be found on separate male and female plants or one plant can have both male and female parts. These male and female structures can be on separate flowers or flowers may also be hermaphroditic. What are hermaphrodite plants? Let’s learn more about plants that are hermaphrodites.

Hermaphroditic Plant Info

Flowers contain the reproductive organs of plants. The main function of the colorful flower petals that most gardeners are drawn to is to attract pollinators to the plant. However, the flower petals also protect the delicate reproductive organs which form in the center of the flower.

The male parts of a flower are known as the stamens and anthers. The anthers contain the flower’s pollen. The female organs of a flower are known as the pistil. This pistil has three parts – the stigma, style and ovary. Pollinators carry pollen from the male anthers to the pistil, where it then fertilizes and grows into seeds.

In plant breeding, it is important to know where the male and female reproductive organs are on plants. Hermaphroditic plants have male and female reproductive organs within the same flower, like tomatoes and hibiscus. These flowers are oftentimes referred to as bisexual flowers or perfect flowers.

Plants that contain male and female reproductive organs on separate flowers on the same plant, like squash and pumpkins, are called monoecious plants. Plants that have male flowers on one plant and female flowers on a separate plant, like kiwi or holly, are known as dioecious plants.

Hermaphroditic Plants in Gardens

So why are some plants hermaphrodites while others are not? The placement of the reproductive parts of a plant depends upon how they are pollinated. Flowers on hermaphroditic plants can pollinate themselves. The result being seeds that produce replicas of the parent.

Plants that are hermaphrodites are more common than you may think. Some popular hermaphroditic plants are:

  • Roses
  • Lilies
  • Horse Chestnut
  • Magnolia
  • Linden
  • Sunflower
  • Daffodil
  • Mango
  • Petunia

I’ll give you credit for one thing, Atrehyeu. You used intersex, the term for those with genital anomalies that many prefer to hermaphrodite, which is a bit too redolent of the freak show for some tastes. In other respects, however, you could stand some serious ignorance intervention.

Strictly defined, intersexuality is when someone’s genitals are either ambiguous or combine male and female elements. Attempts have been made to tease out fine distinctions within this category, including true hermaphrodites, male pseudohermaphrodites, and female pseudohermaphrodites. However you sort it out, this is a pretty exclusive group — something like one person in 5,000 is different enough from the standard model to be considered intersex.

Intersexuality is almost always the result of a genetic disorder. Some conditions, such as androgen insensitivity syndrome (where a genetic male baby can’t process male hormones and grows up female) or Klinefelter syndrome (where males are born with an extra X chromosome), have only a modest impact on quality of life — hell, a few people have parlayed their genetic idiosyncrasies into Olympic gold. Other conditions present more serious challenges. One reads of gonads that are combinations of male and female parts, women born without a vagina, even a few folks born with both a penis and a vagina. One especially unusual type of intersex person is known as a chimera, which results when male and female embryos meld together genetically to form one individual — and if you think you’ve got identity issues in your garden-variety life, try coming to terms with that.

Historically those not falling into one of the two traditional sex buckets have had a tough time of it. The tale is told of a Scottish intersex person, living as a female servant in the 1600s, who was buried alive as punishment for the crime of impregnating at least one of her master’s daughters. Another case involved a close local election in Salisbury, Connecticut, in 1843, when one Levi Suydam applied to vote as a Whig. The opposition objected, claiming Levi was female — women wouldn’t get the right to vote for another 80 years. Doctors called in to scrutinize the hanging chad, as it were, found Levi had a mix of sexual equipment but decided he was mostly male. His ballot was counted and the Whigs won by one vote. On further examination some days later, though, it was discovered that Levi had been menstruating for years and sported a set of “well developed mammae” which the doctors had somehow missed the first time around.

Could an intersex person get him- / herself pregnant (or as doctors put it, “autofertilize”)? Well, think about the necessities for pregnancy: a sperm, an egg, a way for the two to meet, a uterus for fetal development, and the proper hormone levels to ensure the baby doesn’t turn into a squid. Most intersex folks are unable to provide at least one of these critical bits. Surveys suggest functioning ovaries are fairly common in the intersexed; pregnancy and birth don’t happen often, but they happen. Functioning testes are rarer, but again not completely unknown. Functioning ovaries and functioning testes, however, plus functioning everything else — well, I suppose I can propose one far-fetched scenario where it could possibly happen. But as a practical matter: get out. Remember, the idea in intersexuality typically is that you get a mix of male and female pieces. You don’t get two complete sets.

To find a living being that can get itself with child, we need to turn elsewhere in the animal kingdom, and even there the pickings are slim. Hermaphroditism is common in some species; so is having fully functional sets of male and female organs at different stages of life. Despite this, autofertilization is rare, mostly limited to certain earthworms and such. I did come across an oddball case involving an intersex rabbit which, having already birthed more than 250 baby bunnies, became pregnant twice in a row after being placed in isolation. When researchers investigated they found both ovaries and testes (although the latter seemed to be infertile), plus some strange sex chromosomes. What can I say? Nature coughs up some weird shit.

The only way I can imagine self-fertilization happening in a human — and I’m telling you, this one’s a reach — is in a chimerical individual, formed of two embryos that fused. Would the child of such a person be a clone? Of course not, nudnik. First, you’d have to duplicate the genetics of an individual whose makeup was, by definition, an irreproducible accident. Second, the two fused embryos would be fraternal twins (one’s male and one’s female, right?) and thus have different genes. Third, the chromosome-level mechanics of sexual reproduction (surely you remember that fascinating discussion of meiosis from sophomore biology) would ensure that the genetic deck got a good honest shuffle. So while the child of an autofertilizing hermaphrodite would certainly be a close relative of its parent, it’d be a far cry from a xerox copy.

Cecil Adams

Send questions to Cecil via [email protected]

Hermaphroditism

Hermaphroditism, the condition of having both male and female reproductive organs. Hermaphroditic plants—most flowering plants, or angiosperms—are called monoecious, or bisexual. Hermaphroditic animals—mostly invertebrates such as worms, bryozoans (moss animals), trematodes (flukes), snails, slugs, and barnacles—are usually parasitic, slow-moving, or permanently attached to another animal or plant.

In humans, conditions that involve discrepancies between external genitalia and internal reproductive organs are described by the term intersex. Intersex conditions are sometimes also referred to as disorders of sexual development (DSDs). Such conditions are extremely rare in humans. In true gonadal intersex (or true hermaphroditism), an individual has both ovarian and testicular tissue. The ovarian and testicular tissue may be separate, or the two may be combined in what is called an ovotestis. Affected individuals have sex chromosomes showing male-female mosaicism (where one individual possesses both the male XY and female XX chromosome pairs). Most often, but not always, the chromosome complement is 46,XX, and in every such individual there also exists evidence of Y chromosomal material on one of the autosomes (any of the 22 pairs of chromosomes other than the sex chromosomes). Individuals with a 46,XX chromosome complement usually have ambiguous external genitalia with a sizable phallus and are therefore often reared as males. However, they develop breasts during puberty and menstruate and in only rare cases actually produce sperm. In 46,XX intersex (female pseudohermaphroditism), individuals have male external genitalia but the chromosomal constitution and reproductive organs of a female. In 46,XY (male pseudohermaphroditism), individuals have ambiguous or female external genitalia but the chromosomal constitution and reproductive organs of a male, though the testes may be malformed or absent.

Treatment of intersex in humans depends upon the age at which the diagnosis is made. Historically, if diagnosed at birth, the choice of sex was made (typically by parents) based on the condition of the external genitalia (i.e., which sex organs predominate), after which so-called intersex surgery was performed to remove the gonads of the opposite sex. The remaining genitalia were then reconstructed to resemble those of the chosen sex. The reconstruction of female genitalia was more readily performed than the reconstruction of male genitalia, so ambiguous individuals often were made to be female. However, intersex surgery has long-term consequences for affected individuals. Later in life, for example, the person may not be satisfied with the results of surgery and may not identify with the assigned gender. Thus, patient consent has become an increasingly important part of decisions about intersex surgery, such that surgery may be delayed until adolescence or adulthood, after patients have had sufficient time to consider their gender and are able to make informed decisions about treatment. In older individuals the accepted gender may be reinforced by the appropriate surgical procedures and by hormonal therapy.

Can Hermaphrodites Teach Us What It Means To Be Male?

The vinegar worm (officially known as Caenorhabditis elegans) is about as simple as an animal can be. When this soil-dwelling nematode reaches its adult size, it measures a millimeter from its blind head to its tapered tail. It contains only a thousand cells in its entire body. Your body, by contrast, is made of 36 trillion cells. Yet the vinegar worm divides up its few cells into the various parts you can find in other animals like us, from muscles to a nervous system to a gut to sex organs.

In the early 1960s, a scientist named Sydney Brenner fell in love with the vinegar worm’s simplicity. He had decided to embark on a major study of humans and other animals. He wanted to know how our complex bodies develop from a single cell. He was also curious as to how neurons wired into nervous systems that could perceive the outside world and produce quick responses to keep animals alive. Scientists had studied these two questions for decades, but they still knew next to nothing about the molecules involved. When Brenner became acquainted with the vinegar worm in the scientific literature, he realized it could help scientists find some answers.

Its simplicity was what made it so enticing. Under a microscope, scientists could make out every single cell in the worm’s transparent body. It would breed contentedly in a lab, requiring nothing but bacteria to feed on. Scientists could search for mutant worms that behaved in strange ways, and study them to gain clues to how their mutations to certain genes steered them awry.

Brenner’s instinct proved correct. In 2002, he shared the Nobel Prize with John Sulston and Robert Horvitz for their research on the vinegar worm. Other scientists have done pioneering work on the animal as well, with over 22,000 papers published on it over the past five decades. Today, they show no signs of slowing down.

But something fascinating unfolded along the way. The more scientists examined the supposedly simple vinegar worm, the more complexity they uncovered. And some of the most fascinating complexity about the vinegar worm involves its sex life.

By comparison, our own sex life is pretty dull. In humans and many other animal species, individuals are typically either males or females. The males produce the sperm, and the females produce the eggs. In C. elegans, individuals can either be males or hermaphrodites.

The biology of the male worms is straightforward enough: they have sperm, which they can insert into a mate. But the biology of the hermaphrodites is unquestionably strange. They start out life essentially as males, producing sperm that they store in a special chamber deep inside their body. Later in life, their gonads undergo a radical transformation: now they only make eggs.

The hermaphrodite never develops an organ for delivering sperm into other worms. And so it can only use its sperm to fertilize its own eggs. When an egg is ready to develop, it swims past the sperm chamber, picks up a sperm, and then continues on to the worm’s uterus, where it can develop into a larva. This self-fertilization is called selfing.

For a male worm to become a father, he has to interrupt the selfing going on inside a hermaphrodite. After mating, the male’s sperm swim to the chamber, where they dump out the hermaphrodite’s own sperm and swim inside to take their place. When an egg travels past the chamber, it picks up the male’s sperm for fertilization.

Another peculiar feature of the sex life of vinegar worms is the balance of the sexes. In many species—like our own—the population is split pretty much down the middle, half male and half female. The balance is more complicated for the supposedly simple vinegar worm. Many scientists still raise the strain that Sydney Brenner selected in the early 1960s. Those worms will typically produce one new male for every thousand females. The frequency of males can by higher in wild populations, though. In some places, a third of the worms turn out to be male.

Scientists are left with some puzzling questions. Why do males vary from one population to the next? Why are there even males at all?

On paper, at least, abandoning males would seem like the superior evolutionary strategy. If a hermaphrodite produces only hermaphrodites, all of its offspring can start reproducing as soon as they become mature. The males can only reproduce if they find a willing hermaphrodite. And even then, their offspring will only inherit half of their genetic material. By this reasoning, you would expect that the genes for making males should have disappeared from the C. elegans gene pool long ago.

To find out why males stick around, Henrique Teotonio, a biologist at Ecole Normale Superieure in France, and his colleagues have run experiments on vinegar worms. They mix males and hermaphrodites together and rear them under challenging conditions, holding back on their regular supply of bacteria to eat. They then let the worms reproduce for 100 generations, watching for any changes along the way.

Over the course of the experiment, Teotonio observed, the worms produced more males. Somehow, natural selection was favoring a more male-heavy ratio. And at the end of the experiment, the scientists compared how well worms produced from outcrossing did against worms produced by selfing. The outcrossed worms fared better.

These experiments hint that outcrossing has some advantages over selfing. When a male fertilizes a hermaphrodite, their offspring inherit a mixture of genes. Across a whole population of worms, this has the effect of shuffling different decks of genetic cards together, producing new combinations of different variants of genes. Some of these new combinations may prove to make worms better able to meet the challenges posed by their environment.

Selfing, on the other hand, can’t shuffle the decks much, because a worm is simply combining its own sperm and egg. Sometimes a mutation will arise that will make a worm better able to survive, but this is a slow way to produce genetic variation. As a result, selfing worms may be less able to cope with life’s challenges.

Still, the advantage of males has its own limits. Other experiments Teotonio has run suggest that hermaphrodites hold onto their own sperm as an insurance policy. If they had to depend entirely on male worms for sperm, they would run the risk of never finding a mate in their short lifetime and never producing offspring.

These insights are shedding light on the long-term evolution of C. elegans. The most closely related species of worms have males and females, indicating that the ancestors of today’s C. elegans started out that way, too. But then mutant females arose that could produce their own sperm. They became more common, thanks to the advantages of selfing, although a little outcrossing still offers some evolutionary benefits.

In worms with two sexes, the males attract the females by producing courtship chemicals. In C. elegans, the males still release those same chemicals. But hermaphrodites no longer respond as their female ancestors did. They immediately try to escape the attentions of the male worm. By minimizing sex, the vinegar worm may get the most benefit from sex while paying the fewest costs.

If there is a simple lesson about sex that the vinegar worm can teach us, it’s that sex is never simple. Evolution transforms it into an ever-shifting rainbow of forms. And in the simplest animal imaginable, sex can be wonderfully difficult to decipher.

You don’t have to be an expert on the plant to at some point have encountered the term ‘feminized’ in relation to cannabis seeds. As it suggests, this means cannabis plants can be either female or male and in some cases have both sexes. This is what you need to know to spot Male, Female and Hermaphrodite cannabis plants in your garden:

Male or Female Cannabis Plants

Before we dive into the more complicated matter when it comes to sexing a cannabis plant, let’s start with some basics. Cannabis plants are so called ‘dioecious plants’. This means they produce either male of female reproductive organs, known as the flowers. In contrast to ‘monoecious plants’, which produce two different types of flowers on the same plant.

The cannabis plants most consumers know and love are often female. As these are the plants that produce the smokeable flowers – the dried buds sold in Amsterdam’s best coffeeshops – but which can also be grown at home. These weed flowers are covered in trichomes / resin which holds the plants active components, like cannabinoids and terpenes. Male cannabis plants however are less popular with consumers, as their only task in life is to release pollen into the air.

Feminized Cannabis Seeds

When pollen from a male cannabis plant reaches a female cannabis flower, the female flower will start producing seeds with traits from both plants involved. That’s great for growers that like crossbreeding strains and develop their own cannabis varieties. But if you’re growing for your personal consumption, you might want to avoid pollination. Not only do seeds add a harsh taste to your smoke. Producing them also takes a lot of energy from the plant. Costly energy that should rather be put into the development of cannabinoids like THC and CBD.

Las flores hembra llenarán sus cálices
with seeds when they’re pollinated

The best thing you can do to guarantee you’ll grow female cannabis plants, is to purchase feminized cannabis seeds. In contrast to regular cannabis seeds, which will grow 50/50 males and females, feminized seeds guarantee for 98% to grow into female cannabis plants.

So even if you use feminized seeds, it is advised to keep a close eye and determine the sex of the plant as soon as you can. As there’s always a small chance at finding a male plant in your garden which could screw up your harvest. Or for the plant to turn hermaphrodite and develop both sexes on one plant; as we’ll explain later on.

Female Cannabis Plants

The sex of cannabis plants can be determined by looking for the first signs of bloom on the plant. These are visible a few days to a week after you switch your light to 12/12 and give your plant the sign to start flowering – or when nature itself ignites the flowering phase by making days shorter than 14 hours.

Female cannabis plants are easy to spot once they start showing the first signs of flowering

Female weed plants are distinguished by the development of bracts with small white hairs (stigma’s) on their nodes. A node is the part of the plant where branches and leaves emerge from the stem. After a while, the plant starts pushing out more and more of these hairs until they swell up from the bottom up. This means the plant is now forming ‘calyxes’ that eventually stack up to become the flower as we know it.

These ‘calyxes’ remain empty as long as the plant is not pollinated. When it does get pollinated, these calyxes will fill up to hold and protect the plant’s babies: seeds. It is even thought that the resin on weed plants serves only that purpose in nature: to protect the plant’s offspring from burning in the sun.

Male Cannabis Seeds

Male Cannabis Plants are recognized by the formation of pollen sacs on the plant’s nodes. This happens around the same time as female reproductive organs should be forming. Although female plants tend to develop their reproductive organs a bit faster. Luckily, these male pollen sacs can be distinguished pretty easily. As they look like small balls hanging from the side of the plant; instead of the upward facing hairs from the female plant.

Male Cannabis Plants form small ball-shaped pollen sacs on their nodes

When left to grow, these balls will eventually open up like a flower and release pollen into the air. As we’ve explained, this pollen is only interesting when you’re trying to make your own strains or seeds. If you’re not making seeds, make sure to remove every male plant from your garden or grow room before this happens. Do it with the upmost care, as rocking the plant could force it to release the pollen.

Hermaphrodite Cannabis Plants

The first paragraph of this article explains cannabis plants grow only one set of reproductive organs. Although there is still a ‘but’ to this. Because there always remains the possibility that female cannabis plants form male reproductive organs too. This usually happens when the plant(s) experience excessive stress. And so they try to guarantee the survival of their species.

Hermaphrodite cannabis plants develop both female and male reproductive organs

Because when cannabis plants turn ‘hermaphrodite’, it is so they can pollinate themselves. A risk you take with growing plants that are sensitive to stress and developing hermaphroditic traits – like the well-known Original Glue (Gorilla Glue #4). To avoid hermaphrodite cannabis plants from pollinating themselves, carefully remove the male reproductive organs that form on the nodes. You can do so by gently taking a pollen sac in between two fingers and twist/pull it off. This way you can have a banging harvest from any hermaphrodite, without having to pluck the seeds from your buds.

Lets face it; most things in the natural world revolve around sex. Specifically, making sure you survive long enough to find and impress a mate—then have lots of offspring. It’s a complicated game that has led to all sorts of adaptations, but the one we’re sharing with you today is amongst the most surprising—the ability to change sex.

For lots of animals, sex is largely defined before birth, and depends on the chromosomes you receive during fertilisation. Yet for other animals like fruit flies, fish and some reptiles, things work a little bit differently. Depending on environmental and social conditions, some animals can change sex (and then even change back again!).

Here are six surprising animals that can change their sex.

6. Fish

Photo by Dezay / Shuttestock

Of all the sex changers in the animal kingdom, fish are the most well known. For clownfish, it’s very much a man’s world because all clownfish are, in fact, born male. The most dominant male of the group will become female. There will only be one female per clownfish group. If she dies, then it’s normally down to the largest male to change sex and take her place.

Wrasses on the other hand work the other way, with groups being made of many females and one male. Exactly how this works is still something of a mystery, but it seems to consist of massive changes in hormone levels with ovaries transforming into testes. Amazingly, the fish can complete this transformation in as little as a week.

Whilst this was once thought to be rare, sex changes have now been observed in several dozen fish families. For many, it seems to be a strategy to ensure that the individual can find a mate. For example in the deep sea, where densities are extremely low, it may be very rare to encounter another of your species—thus being able to change sex would be a huge advantage.

5. Corals

Forest fire mushroom coral. Photo by goobafish /

To jump to something a little more obscure, in 2008 it was discovered that mushroom corals can also change sex…in both directions! In comparison to fish, very little is known about the sex lives of corals, although it seems quite common for polyps to bud off from the parent in a form of clonal reproduction. Whether this ability to change sex will be discovered in other coral species remains to be seen.

4. Slugs

The banana slug, so called because, you guessed it, it looks like a banana. Photo: Wikipedia

Amongst animals with a weird sex life, slugs are surely right up there at the top of the list. For slugs it seems choosing one sex just isn’t enough. Slugs are hermaphrodites, having both female and male reproductive organs, which they use to mate simultaneously.

Unfortunately, things get even weirder with a group called the banana slugs (Ariolimax). These slimy critters engage in Apophallation, which is the scientific term for biting off the partners’ penis. Some scientists have hypothesised that preventing the partner mating as a male again might be a selective advantage. Other than that, it’s just strange.

3. Frogs

The Common reed frog. Photo: Wikipedia

Spontaneous sex change has also been observed in the common reed frog (Hyperolius viridiflavus) from West Africa (fans out there might also note that this is the same species of frog whose DNA was used to fill gaps in dinosaur DNA in the movie Jurassic Park).

Unfortunately in some cases human activity seems to also have had an impact on the sex of animals. A commonly used pesticide called atrazine has been found to change the sex of frogs exposed to it. It causes the frogs to increase production of oestrogen, turning males into fully functional females. The impact of this on wild populations is currently a hot research topic.

2. Snakes

The yellow-bellied water snake. Photo by Nick Stroh /

Who needs men anyway? Some female snakes such as the yellow-bellied water snake (Nerodia erythrogaster) kept alone in captivity have unexpectedly given birth to litters of baby snakes. Known as parthenogenesis, it’s a type of asexual reproduction and might have evolved as a last resort strategy when no males can be found.
Exactly how it works on a cellular level is still a mystery, but scientists think that under certain conditions one of the egg cells can behave like a sperm. More parthenogenesis has been described in other species such as sharks and amphibians, but so far it has never been reported in mammals.

1. Butterflies, Birds and Lobsters

Some birds can be both sexes simultaneously. A number of cardinals have been observed displaying both the red colouration of the male (right) on one half their body, and the more mottled grey colouration of the female (left) on the other.
Photo by Bonnie Taylor Barry /

Last, but not least, very occasionally animals can be born as both male and female. But these unusual cases aren’t hermaphrodites, they are literally half of each sex. This is perhaps most striking in butterflies, where each wing could be a different colour. Known as gyandromorphs, it most likely occurs as a mistake in very early cell division. Gyandromorphs have subsequently been found in a handful of other animals, including birds and lobsters.

@James_Borrell

PMC

DISCUSSION

Previous experimental studies of sex allocation in simultaneously hermaphroditic animals often have focused on mating-group size and competition among individuals to fertilize eggs (local mate competition). Theory predicts that individuals should reduce proportional male allocation as mating-group size decreases and causes local mate competition to increase. The theory is supported by data from fishes (12, 27–29) and a barnacle (30). The selective effects of local mate competition can be explained in several ways (see refs. 5 and 31). To understand the analogy with self-fertilization, consider a reduction in mating-group size. Competition among individuals to fertilize eggs will increase. As a result, the fitness returns per unit of male investment begin decelerating at a lower investment than in a larger group. Local mate competition therefore selects for decreased allocation to male function in hermaphrodites and for lower male-progeny sex ratios in dioecious taxa (2–5, 12, 31–33). Similarly, as self-fertilization increases, the pool of eggs available to be fertilized by outcrossed sperm diminishes, and each sperm, or unit of male investment, is competing for fewer available eggs (5, 11).

The present study found that mussels in populations with higher rates of self-fertilization devoted a lower proportion of reproductive tissue to sperm production. Male allocation ranged from about 0.3 to 0.6. In Rivulus marmoratus (Cyprinodontidae), a simultaneously hermaphroditic fish with a very high natural selfing rate, Harrington (34) reported male allocation to be approximately 0.03, one-tenth the value found in the most highly selfing mussel population. The correlation between selfing rate and proportional male investment previously has been investigated only in plants, which display great evolutionary lability in mating systems. Among unrelated angiosperm taxa, it has long been appreciated that highly selfing species, as often judged by floral–morphological characteristics, produce less pollen than highly outcrossing species (35–37). Lloyd (38) found that pollen production in species of Cotula (Asteraceae) judged more likely to be outcrossers was lower than in species judged to be more highly selfing. Among nine species of wind-pollinated herbs, the effort (mass) devoted to anthers relative to seeds was lower in self-compatible, and therefore potentially self-fertilizing, species than in self-incompatible (n = 1) or dioecious species (n = 2) (39).

Correlations between selfing rate and sex allocation can be measured only when the mating system is quantified. Genetic markers can be used to estimate population selfing rates either from inbreeding coefficients (22), as in the present study, or by analysis of progeny genotypes (40, 41). Furthermore, tests are best conducted between closely related species or populations within species, so that unmeasured factors do not confound the correlation. There are very few studies meeting both criteria, and all have found a negative relationship (42). With selfing rates ranging from 0.04 to 0.85 among seven populations of Gilia achilleifolia (Polemoniaceae), an insect-pollinated annual, Schoen (43) found the correlation between proportional male allocation and selfing rate to be approximately −0.99, similar to the value found in the present study. A similar negative correlation (approximately −0.9) occurred among six populations of Eichhornia paniculata (Pontederiaceae), where selfing rates ranged from 0 to 0.9 (44). The correlation was approximately −0.5 among eight closely related species of Mimulus (section Simiolus, Scrophulariaceae), among which selfing rates ranged from 0.31 to 0.84 (45). The Mimulus allocations were measured at flowering and therefore omitted seed production, which is the major portion of female allocation. It seems likely that the absolute value of the correlation would be somewhat increased if measured at the fruiting stage, as was found by comparing the two measures in Eichhornia (44). A negative but statistically nonsignificant relation was found among Jamaican populations of Turnera ulmifolia (Turneraceae), where selfing rates ranged from 0 to 0.31 (46). In the only study of a wind-pollinated plant, Charnov (16) investigated 31 varieties of wild rice, Oryza perennis (Poaceae), and found a correlation of −0.84 between selfing rate and the ratio of anther mass to seed mass, a measure of male allocation slightly different from that used in the other studies.

Our method assumed that the relevant components of reproductive allocation have been measured. Brooding may represent an unmeasured female cost, given that some extra tissue is devoted to gills and that larvae may reduce food intake of the parent. We were, however, concerned with the decline of male allocation with selfing rate, rather than absolute measures of allocation. It seems unlikely that incorporating costs of brooding would have much effect on this relationship. Our method furthermore assumed that the cost per tissue area remained constant at all levels of allocation. Unequal true costs per area for male and female tissues would again change the absolute allocations but not the pattern of decline. Gonads might also mature at slightly different rates within seasons, which would introduce some error into the estimates of sex allocation (17). Such error should not be systematic, because our collections occurred throughout the reproductive season.

The mussel populations showed great variability in mating system, from nearly complete outcrossing to complete selfing. Evolution of rates of self-fertilization depends on the balance of several ecological and genetic factors, as well as on phylogenetic history. For example, self-fertilization should be advantageous when the probability of successful outcrossing is low, as in colonization events (47). Self-fertilization furthermore transmits two gene copies to each offspring, as compared with one through outcrossing. This genetic transmission advantage automatically selects for increased selfing rates unless checked by other factors, such as lowered fitness of progeny from selfing (inbreeding depression) or reduced success through sperm broadcast (sperm or pollen discounting) (48). In addition, mutations causing large increases in the selfing rate can increase in frequency regardless of the level of inbreeding depression, because individuals bearing such mutations will form a subpopulation that is largely genetically isolated (49).

Previous reports on U. imbecillis suggested that low male investment is characteristic of high-density, central-range populations of lakes and canals, whereas high male investment is characteristic of lower-density, peripheral populations of creeks and rivers (17). Those reports, however, measured the ratio of male to female areas, rather than male to total. They furthermore failed to determine areas throughout the visceral mass, reporting this to be relatively constant, in disagreement with the present results.

The generality of sex-allocation theory will be determined only by examining diverse taxa, and current sex-allocation theory is framed in terms that should apply equally to plants and animals. Hermaphroditism and self-fertilization are common among the vascular plants (50) but proportionally rarer among animal species. Nevertheless, several animal phyla, such as mollusks, include both dioecious and hermaphroditic groups (51, 52) in which it should prove profitable to investigate the evolutionary forces acting on rate of self-fertilization. Testing sex-allocation theory in plants often involves measuring investment in attractive structures and then either assigning a fraction of the investment to male and female function (53) or determining the effects of attraction on success through male function, female function, and self-fertilization (15). Animals, in contrast, do not attract or pay biotic agents to transfer gametes and should therefore prove especially useful for straightforward tests of many predictions of sex-allocation theory. These tests ideally will be not made among higher taxa but rather among closely related populations or species, where it is most likely that the selective forces are currently operating (ref. 3, p. 123).

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The life of the cottony cushion scale insect reads like something from the most ridiculous of tabloid newspapers. Dad leaves parasitic body parts in his own daughter, which produce sperm that fertilise her eggs. He is both father and grandfather to his own grandchildren. On top of that, these insects are mostly hermaphrodites. With the exception of the odd pure male, almost every individual is both male and female. They reproduce by having sex with themselves, fertilising their own eggs with their own sperm. And this means that scale insects can be father, mother, grandfather and grandmother to all of their grandchildren. Good luck drawing that family tree. Scale insects are small animals that suck on plant sap for a living. Encased in bizarre waxy shells, most people wouldn’t even recognise them as insects – the cottony cushion scale, for example, looks like a dollop of shaving foam. It and two of its close relatives are the only known hermaphrodites out of several millions of insect species. In most hermaphroditic animals, an individual grows up and develops the organs that make both sperm and eggs. But that’s not the case for the cottony cushion scale. When it mates with itself, it fertilises its own egg with its own sperm. Then, after the point of conception, yet more sperm invades the embryo. This “infectious tissue” creates sperm-producing organs inside the daughter* and the resulting sperm eventually fertilises the daughter’s eggs. (A note on terminology: obviously, each insect is hermaphrodite but they’re referred to as “daughters” because they have the body of a female. The rare pure males look very different.) How did this bizarre sexual system evolve? In 2009, Benjamin Normark suggested that it’s the result of a battle of the sexes. He envisioned a time when males and females were separate entities. When males gained the ability to infect their daughters with “parasitic” sperm, they could fertilise the eggs of multiple generations. This trait spread until the parasitic tissue became the norm, and true males all but disappeared. Normark assumed that the infectious sperm would be parasitic, that it would always benefit the male lineage at the expense of the daughters’ health or reproductive ability. That’s a reasonable assumption, given the sexual conflicts that rage in other insects – many species produce sperm that do harm females or even shorten their lives. But Andy Gardner and Laura Ross from the University of Oxford think that there’s more to the evolution of the scale insect’s sex life than males versus females. They developed a mathematical model to simulate these sexual conflicts among ancestral scale insects where the sexes were still separate. The model accounts for the fact that daughters aren’t infected with any old parasitic tissue – it comes from their “father”, and carries many of the same genes that they have. As such, there’s potential for them to cooperate, rather than compete. Their model predicts that when this odd tactic first evolved, the infectious tissue would probably have harmed the females in some way, who would have adapted to suppress it. In fact, if the harms were high enough, the infectious tissue would probably have evolved to suppress itself – its genes would have had a higher chance of reaching the next generation if it let the daughter get on with things herself and mate with a true male. Over time, this conflict would have weakened. The infectious tissue would have become more common, and inflicted less harm upon the females. Eventually, daughters would actually benefit from being fertilised by dad’s sperm. At some time, there would have been a tipping point when conflict gave way to collaboration. Females would pass on more of their own genes to the next generation if they mate with their own parasitic fathers rather than with other males. Normal males started to disappear and the hermaphrodites took over. Rather than existing as a distinct sex, males turned into a lineage of parasitic tissue, passed down from one daughter to the next. There is a final twist to this tale: Gardner and Ross think that the scale insects carry a passenger that could have quickened the demise of the males – a bacterium. Many insects carry helpful bacteria that provide them with important nutrients, and the cottony cushion scale is no different. These bacteria can often be found in tight clusters around the infectious tissue, and if they are killed with antibiotics, females are more likely to produce sons. To Gardner and Ross, this suggests that the bacteria could help to protect the infectious tissue from being destroyed. Why? Because the bacteria are passed down from mother to daughter. Males are a dead-end to them. In this regard, their “interests” are the same as those of the infectious tissue. Sons are a dead-end; daughters provide vessels that sail into the next generation. Reference: Gardner & Ross. 2011. The evolution of hermaphroditism by an infectious male-derived cell lineage: an inclusive-fitness analysis. American Naturalist citation tbc Photo by P. Hollinger More bizarre animal sex:

  • All-male clams escape from genetic canyons by stealing eggs

  • The sexual battles of flatworms: barbed sperm, mating rings, traumatic insemination, and going down on yourself

  • Crayfish females lure males with urine, but then play hard to get

  • Sperm war – the sperm of ants and bees do battle inside the queens

  • Ballistic penises and corkscrew vaginas – the sexual battles of ducks

  • Study reveals sexual tactics of male flies by shaving their genitals with a laser

  • Male water striders summon predators to blackmail females into having sex

Thunderclap headaches are severe…

Linnaeus carefully examined the sexual organs (stamens and pistil) of every Stamen: The organ of a flower that produces the male gamete, and consists of an . Every time a plant grows a new flower, it is growing a new sex organ. Flowers under chemical influence grow in a viable masculine form. However, the plant is . Flowers contain the plant’s reproductive structures. The androecium is the sum of all the male reproductive organs, and the gynoecium is the.

N Many flowers have no calyx, as several of the lily tribe, the bippurir, &c.; many lVe therefore infer from exPerience, that the stamina are the male organs of.

organs of the female called ovaries. Each cacao flower has male parts and female Do not climb cacao trees, as climbing may damage the flower cushions. “Many flowers have no calyx, as several of the lily tribe, the hippuris, &c.; many We therefore infer from experience, that the flamina are the male organs of. “Many flowers have no calyx, as several of the lily tribe, the hippuris, &c.; many We, therefore, infer from experience, than the stamina are the male organs of.

Many flowers have no calyx, as several of the lily tribe, the bippun’r, &c.; many want We therefore infer from eXperience, that the flamina are the male organs of.

Some flowers have both the pollen (male part) and the seed Plants and trees have genders but fruits don’t, because its an organ of an. Pollen grains, which contain the plants’ male gametes (sperm cells), are carried from the male organ of the flower (the stamen) to the female. A gynoecious genotype of J. curcas was found, whose male flowers are of male organs to generate andromonoecious plants (Boualem et al.

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Do Plants Have Sexes?

© neirfy/Fotolia

The idea of “male” and “female” in plants is a bit mysterious to many people, and there are several variations on the theme throughout the plant kingdom. In plants, as with most animals, the male parts are associated with production of sperm, and the female parts are associated with eggs. Thus, in angiosperms (flowering plants) and gymnosperms (plants with “naked seeds”), the male structures produce pollen (which contain sperm), and the female structures have one or more ovaries (which contain eggs known as ovules). We’ll skip over spore-producing plants, such as ferns and liverworts, because their life cycles are more complicated, but they too have male and female parts.

Some plants are indeed only male or only female.Ginkgo, kiwi, cannabis, and willow all have individuals that make only pollen or only seeds. Botanically, they are known as dioecious plants, and their strategy ensures genetic outcrossing. Interestingly, many street trees are dioecious, and, to avoid the mess of flowers and fruits, only male trees were often planted. Unfortunately, this proved to be somewhat of a failure in urban planning, as pollen allergies have worsened in some places, thanks to the high density of male trees happily producing pollen.

However, most plants are monoecious, meaning that individuals have both female and male structures. In flowering plants, these structures can be borne together in a single bisexual flower, or the flowers can be only male (staminate) or only female (pistillate). Many of the most iconic flowers, such as roses, lilies, and tulips, are bisexual, and the female pistil is characteristically surrounded by the male stamens. Other monoecious plants, such as squashes, corn, and birches, have unisexual flowers. That is, some flowers are male and some are female, but both types are formed on the same individual plant. This strategy is also seen in most conifers. Pollen borne in male cones must be blown by the wind to female cones for pollination to occur.

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