I THE DISCOVERY OF SPERM PART ONE
Sperm cells were first observed by van Leeuwenhoek in 1679. Van Leeuwenhoek (1632-1723) was a merchant and scientist from Delft, best known for improvement of the microscope and the establishment of cell biology. Using a handcrafted microscope, van Leeuwenhoek was the first to observe and describe muscles fibers, bacteria, blood flow in capillaries and spermatozoa. Van Leeuwenhoek carved over 500 optical lenses. Van Leeuwenhoek’s microscope was used and improved by Huygens for Huygens’ own investigations into microscopy.
Van Leeuwenhoek was introduced to microscopy by Huygens to observe the quality of fabrics. Van Leeuwenhoek grew interested in microscopy for its own sake and spent many nights in study and notation. The scientific language of the time was Latin but van Leeuwenhoek spoke only Dutch. Van Leeuwenhoek sent a letter to Hooke, who knew both Dutch and Latin, and Hooke instantly realized the quality and pertinence of van Leeuwenhoek’s work. Their correspondence was translated by Hooke into Latin and published in the proceeding of the Royal Society. To honor van Leeuwenhoek’s discoveries, the Dutch Royal Academy presents the van Leeuwenhoek medal to the scientist judged to have made the decade’s most significant finding in microbiology. This is regarded by microbiologists as the highest honor in their field.
Van Leeuwenhoek is thought to have been be the model for the painting titled The Geographer by van Leeuwenhoek’s friend, Vermeer. Van Leeuwenhoek also appeared on an unused design for a 10 Guilder note designed by Escher in 1951.
II THE DISCOVERY OF SPERM PART TWO
Working in the 19th Century, biochemists initially isolated DNA and RNA together from cell nuclei. They were relatively quick to appreciate the polymeric nature of their “nucleic acid” isolates, but realized only later that nucleotides were of two types – one containing ribose and the other deoxyribose. It was this subsequent discovery that led to the identification and naming of DNA as a substance distinct from RNA. Not until 1943 did Avery provide the first compelling evidence that DNA could carry genetic information.
How it could do so was unknown at the time. Because chemical dissection of DNA samples always yielded the same four nucleotides, the chemical composition of DNA appeared simple, perhaps even uniform. Organisms, on the other hand, are fantastically complex individually and widely diverse collectively. The idea that information might reside in a chemical in the same way that it exists in text – as a finite alphabet of letters arranged in a sequence of unlimited length – had not yet been conceived. It would emerge upon the discovery of DNA’s structure, but not many researchers imagined that DNA’s structure had much to say about genetics.
In the 1950s, only a few groups made it their goal to determine the structure of DNA. These included an American group led by Pauling, and two in England. At Cambridge University, Crick and Watson were building physical models using metal rods and balls, in which they incorporated the known chemical structures of the nucleotides, as well as the known position of the linkages joining one nucleotide to the next along the polymer. At King’s College, London, Wilkins and Franklin were examining x-ray diffraction patterns of DNA fibers.
A key inspiration in the work of all of these teams was the discovery in 1948 by Pauling that many proteins included helical shapes. Pauling had deduced this structure from x-ray patterns. Even in the initial crude diffraction data from DNA, it was evident that the structure involved helices. There remained questions such as how many strands came together as one, whether this number was the same for every helix, whether the bases pointed toward the helical axis or away from it, and ultimately what were the explicit angles and coordinates of all the bonds and atoms. Such questions motivated the modeling efforts of Watson and Crick.
In their attempts to model DNA, Watson and Crick restricted themselves to what they saw as chemically and biologically reasonable. A breakthrough occurred in 1952, when Chargaff visited Cambridge and inspired Crick with a description of experiments Chargaff had published in 1947. Chargaff had observed that the proportions of the four nucleotides vary between one DNA sample and the next, but that for particular pairs of nucleotides (adenine and thymine, guanine and cytosine) the two nucleotides are always present in equal proportions.
Watson and Crick had begun to contemplate double helical arrangements, and they saw that by reversing the directionality of one strand with respect to the other, they could provide an explanation for Chargaff’s puzzling finding. This explanation was the complementary pairing of the bases, which also had the effect of ensuring that the distance between the phosphate chains did not vary along a sequence. Watson and Crick were able to discern that this distance was constant, and to measure its exact size from an X-ray pattern obtained by Franklin. The same pattern also gave them the expected pitch of the helix. The pair quickly converged upon a model, which they announced before Franklin published any work on the topic. The great assistance Watson and Crick derived from Franklin’s data has become a subject of controversy, and some believe Franklin has not received due credit. The most controversial aspect is that Franklin’s critical X-ray pattern was shown to Watson and Crick without Franklin’s knowledge or permission. Wilkins showed it to them in a lab while Franklin was away.
Watson and Crick’s model attracted great interest immediately upon its presentation. Arriving at their conclusion on February 21, 1953, Watson and Crick made their first announcement on February 28. Their paper A Structure for Deoxyribose Nucleic Acid was published on April 25. In an influential presentation in 1957, Crick laid out the “Central Dogma”, which foretold the relationship between DNA, RNA, and proteins, and articulated the “sequence hypothesis.” A critical confirmation of the replication mechanism that was implied by the double-helical structure followed in 1958 in the form of the Meselson-Stahl experiment. Work by Crick and coworkers deciphered the genetic code not long afterward. These findings represent the birth of molecular biology. Watson, Crick, and Wilkins were awarded a Nobel Prize in 1962, by which time Franklin had died.
III THE GENERATION OF SPERM CELLS PART ONE
Protein biosynthesis is the process in which cells build protein. The term is sometimes used to refer only to protein translation, but more often it refers to a multi-step process, beginning with transcription and ending with translation.
Transcription generates only one side of the DNA double helix. This strand is called the coding strand. The transcription starts with initiation. RNA polymerase, an enzyme, binds to a specific region on the DNA, marking the starting point, called the promoter. As the RNA polymerase binds on to the promoter, the DNA strands begin to unwind. As the RNA polymerase travels through the opposite strand to the coding strand it matches corresponding mRNA nucleotides to the DNA. The mRNA is elongated as the polymerase proceeds. This process is known as elongation. As the polymerase reaches the termination, modifications are required for the newly transcribed mRNA to be able to travel to the other parts of the cell. A cap is added to the mRNA to protect is from degradation. A poly-A tail is added on the end as a protection and template for further process.
A sperm cell is a haploid cell. Haploid cells have only one copy of each chromosome. Only reproductive cells are haploid in the higher organisms. When reproducing, haploid sex cells will generally merge. The non-haploid cells, the somatic cells, carry one copy of the chromosomes from the sperm. During translation, the message of mRNA is decoded to make proteins. Translation includes initiation, elongation, translocation, and termination. Initiation and elongation occur when the ribosome recognizes the starting codon on the mRNA strand and binds to it. The ribosome has sites which allow another enzyme, tRNA to bind to the mRNA. On tRNA, there is an anticodon that is used to match the codon on the mRNA. tRNA also has a single unit of amino acid attaches to it.
As the ribosome travels down the mRNA one codon at a time, another tRNA is attached to the mRNA at one of the ribosome site. The first tRNA is released, but the amino acid that is attached to the first tRNA is now moved to the second tRNA, and binds to that amino acid. This translocation continues and a long chain of amino acid (protein) is formed. When the entire unit reaches the end codon on the mRNA, it falls apart and a newly formed protein is released. This is the termination. Many enzymes are used to either assist or facilitate the whole procedure during this process. During and after its synthesis, a polypeptide chain begins to coil and fold spontaneously, sometimes with the assistance of chaperone proteins to assume secondary and tertiary structure. Post-translational modification may involve the formation of disulfide bridges and attachment of any of a number of biochemical functional groups, such as acetate, phosphate or various lipids or carbohydrates. Enzymes may also remove one or more amino acids from the leading (amino) end of the polypeptide chain, leading a protein made up by two polypeptide chains connected by disulfide bonds. In other cases, two or more polypeptides that are synthesized separately may join to become subunits of a protein with quaternary structure.
IV THE GENERATION OF SPERM CELLS PART TWO
Sperm is produced in the testicles; most of the remaining semenal fluid is produced by the prostate. The prostate is a gland that is part of a human’s sex organ and surrounds the tube called the urethra, located just below the bladder. A healthy prostate is approximately the size of a walnut. The urethra has two functions: to carry urine from the bladder during urination and to carry semen during ejaculation. To function properly, the prostate needs human hormones (androgens). Such hormones are responsible for human sex characteristics. The main human hormone is testosterone, which is produced by the testicles. Some human hormones are produced in small amounts by the adrenal glands. Massage of the prostate gland can be pleasurable; one way to stimulate it is through receiving anal sex.
To produce sperm, testicles need to be several degrees cooler than body temperature. If the testicles are subject to heat, sperm production temporarily stops. Immersing the testicles in hot water for a period of time each day for several weeks can result in a temporary inability to produce sperm. Pushing the testicles inside the body, tight clothing and tying the empty scrotum for a period of time also achieves this effect. In antiquity this effect was achieved by sitting on hot rocks or painting the testes with molten pitch.
V THE DEFINITION OF SPERM
A sperm cell is the human gamete. Gametes are the cells that come together during fertilization or conception in organisms that reproduce sexually. A gamete’s chromosomes are not duplicates of either of the sets of chromosomes that are carried in the somatic cells of the individual that produced the gametes. Instead, they are hybrids which are produced through the recombination or crossing over of chromosomes that takes place in the making of gametes (“meiosis”). This hybridization has a random element and every gamete a human produces the chromosomes tends to be unique.
In humans, sperm cells consists of (1) Acrosome (2) Cell membrane (3) Nucleus (4) Mitochondria (5) Tail (flagella). The acrosome develops over the anterior half of the head. It is a cap-like structure containing corrosive enzymes. The acrosome derives from the Golgi apparatus. The tail flagellates, which propels the sperm.
The sperm cell membrane (or plasma membrane) is a thin, structured layer of lipid and protein molecules that completely envelopes the cell, separating its interior from the surroundings and strictly controlling what moves in and out. In animal cells, the membrane establishes this separation alone; in yeast, bacteria and plants an additional cell wall forms the outermost boundary providing primarily mechanical support. The plasma membrane may be discerned only faintly with a transmission electron microscope.
The sperm cell nucleus is an organelle within an eukaryotic cell. Its main function is to control chemical reactions in the cell cytoplasm. The nucleus, being the largest sub-cellular compartment, varies in diameter. It is surrounded by a double membrane forming the nuclear envelope. This selectively allows molecules to enter and leave the nucleus, and separates chemical reactions taking place in cytoplasm from reactions occurring within the nucleus. The outer membrane has ribosomes. The inner and outer membrane fuse at regular spaces, forming nuclear pores.
Similar to the cytoplasm of a cell, the nucleus contains nucleoplasm: a highly viscous solid containing the chromosomes and nucleoli. Chromosones contain information encoded in DNA attached to proteins called histones arranged in to a dense network called chromatin. Nucleoli are granular structures which make ribonucleic DNA (rDNA) and assemble it with proteins.
Sperm cell mitochondra are membrane-enclosed cellular organelles. Mitochondria are distributed through the cytosol of most eukaryotic cells. Their main function is to convert the potential energy (via electron transport) of food molecules into ATP (the universal energy currency of the cell). They are composed of folds called cristae which give a much increased surface area on which chemical reactions can occur. The outer membrane encloses the entire organelle and contains channels made of protein complexes through which molecules and ions can move in and out of the mitochondrion. Large molecules are excluded from traversing this membrane. The inner membrane, folded into cristae, encloses the matrix (the internal fluid of the mitochondrion). It contains several protein complexes. Stalked particles are found on the cristae: these are the ATP synthetase enzyme molecules, which produce ATP. The intermembrane space between the two membranes contains enzymes that use ATP to phosphorylate other nucleotides and that catalyze other reactions. The word mitochondrion has the etymological root of ‘thread granule’, describing their appearnace under a microscope; tiny rod-like structures present in the cytoplasm of all cells. The matrix contains soluble enzymes that catalyze the respiration of pyruvic acid and other small organic molecules. Parts of the Krebs Cycle occur within mitochondria. The matrix also contains several copies of the mitochondrial DNA (usually 5-10 circular DNA molecules per mitochondrion), as well as special mitochondrial ribosomes, tRNAs, and proteins needed for DNA replication.
Endosymbiosis describes the situation in which one organism lives within cells of another organism. The intracellular organism is called an endosymbiont. It is also generally believed that certain organelles of eukaryotic cells, especially mitochondria and chloroplasts, originated as bacterial endosymbionts. This theory is known as the endosymbiotic hypothesis.
Sperm flagella are a propulsive structure used to move through a liquid medium. There are three main varieties of flagellum; the bacterial flagellum (a helical filament that rotates like a screw), archaeal flagellum (similar but nonhomologous to the bacterial flagellum), and the eukaryotic flagellum (a whip-like structure that lashes back and forth). Humans produce eukaryotic flagellum.
The eukaryotic flagellum, also called a cilium or undulipodium, is completely different from the prokaryote flagella in structure and in evolutionary origin. The only characteristic that the bacterial, archaeal, and eukaryotic flagella have in common is that they exist outside of the cell and move to produce propulsion. A eukaryotic flagellum is a bundle of nine fused pairs of microtubules called doublets surrounding two central single microtubules (axoneme). At the base of a eukaryotic flagellum is a microtubule organizing center, called the basal body or kinetosome. The flagellum is encased within the cell’s plasma membrane, so that the interior of the flagellum is accessible to the cell’s cytoplasm. This is necessary because the flagellum’s flexing is driven by the protein dynein connecting the microtubules all along its length and forcing them to slide relative to each other, and ATP must be transported to them for them to function.
It is possible the ancestral eukaryote was a flagellate, and if not they appeared fairly early on in their development. Animals, fungi, and plants are all derived from various lines of flagellates, something reflected in the presence of flagellate cells in most forms, whose ultrastructure is a useful guide to determining relationships. Humans that consume any amount of coffee have sperm that travel faster than those who consume no coffee.
Ribonucleic acid (RNA) is a nucleic acid. It is structurally distinguished from DNA by the presence of an additional hydroxyl group attached to each pentose ring and functionally distinguished by its role in the transmission of genetic information from DNA (by transcription) and into protein (by translation).
RNA has 4 different bases: adenine, guanine, cytosine, and uracil. The first 3 bases are the same as those found in DNA, but uracil replaces thymine as the base complementary to adenine. This may be because uracil is energetically less expensive to produce, although it easily degenerates into cytosine. Thus, uracil is appropriate for RNA, where quantity is important but lifespan is not, whereas thymine is appropriate for DNA. Structurally, RNA is indistinguishable from DNA except for the presence of an additional hydroxyl group attached to the pentose ring. This additional group gives the molecule far greater catalytic versatility and allows it to perform reactions that DNA is incapable of performing.
A major difference between RNA and DNA is that RNA is found in the single-stranded form (an exception being the genetic material of some kinds of viruses). RNA molecules often fold into more complex structures by making use of complementary internal sequences; that is, one part of a single RNA molecule is the nucleic acid complement of another part of the same molecule (for exampls, 5′-ACUCGA-3′ and 5′-UCGAGU-3′), so that the two strands bind together. This allows the formation of hairpin loops, coils, etc., which then direct the formation of higher-order structures.
The first life on earth may have been RNA-based, due to RNA’s ability both to carry genetic information like DNA and also to catalyze biochemical reactions like enzymes. This possibility is termed the RNA world hypothesis. Even today, some viruses, such as retroviruses, use RNA as their sole genetic material. RNA is less stable than DNA, however, and is also a less efficient catalyst than a protein-based enzyme. These facts may have led to selection for reduced use of RNA in cells, and greater use of DNA and proteins.
Deoxyribonucleic acid (DNA) is the primary chemical component of chromosomes and the material of which genes are made. It is sometimes called the molecule of heredity, because humans transmit copied portions of their own DNA to offspring and because in doing so they propagate their traits.
In fact, the units of DNA that reside in the nucleus of eukaryotic cells, and DNA are not single molecules. They are pairs of molecules, which entwine like vines to form a double helix. Each strand of DNA is a chemically linked chain of nucleotides, which each consist of a deoxyribose sugar, a phosphate, and one of four varieties of aromatic bases. Because DNA strands are composed of these nucleotide subunits, they are polymers. The diversity of the bases means that four distinct kinds of nucleotide exist, which are commonly referred to by the identity of their base. These are adenine (A), thymine (T), cytosine (C), and guanine (G).
In a DNA double helix, two polynucleotide strands come together through complementary pairing of the bases, which occurs by hydrogen bonding. Each base forms hydrogen bonds readily to only one other (A to T and C to G) so that the identity of the base on one strand dictates what base must face it on the opposing strand. Thus the entire nucleotide sequence of each strand is complementary to that of the other, and when separated, each may act as a template with which to replicate the other from free nucleotides.
Because pairing causes the nucleotide bases to face the helical axis, the sugar and phosphate groups of the nucleotides run along the outside, and the two chains they form the backbones of the helix. Chemical bonds between the phosphates and the sugars that link one nucleotide to the next in the DNA strand.
When the ends of a piece of double-helical DNA are joined so that it forms a circle, as in plasmid DNA, the strands are topologically knotted. This means they cannot be separated by any process that does not involve breaking a strand. The task of unknotting topologically linked strands of DNA falls to enzymes known as topoisomerases. Some of these enzymes unknot circular DNA by cleaving two strands so that another double-stranded segment can pass through. Unknotting is required for the replication of circular DNA as well as for various types of recombination in linear DNA. The DNA helix can assume one of three slightly different geometries, of which the B form described by Watson and Crick is believed to predominate in cells. The frequency of twist (known as the helical pitch) depends largely on stacking forces that each base exerts on its neighbors in the chain.
The narrow breadth of the double helix makes it impossible to detect by conventional electron microscopy except by heavy staining. At the same time, the DNA found in many cells can be macroscopic in length. Consequently, cells must compact DNA to carry it within them. This is one of the functions of chromosomes, which contain spool-like proteins known as histones, around which DNA winds. Many molecular biological processes can induce strain. A DNA segment with excess or insufficient helical twisting is referred to, respectively, as positively or negatively super coiled. DNA typically begins by being negatively super coiled, which facilitates the unwinding of the double-helix required for RNA transcription.
The two other known double-helical forms of DNA, called A and Z, differ modestly in their geometry and dimensions. The A form appears to occur only in dehydrated samples of DNA, such those used in crystallography experiments, and possibly in hybrid pairings of DNA and RNA strands. Segments of DNA in which cells have methylated for regulatory purposes may adopt the Z geometry. In Z, the strands turn about the helical axis like a mirror image of the B form. Within a gene, the sequence of nucleotides along a DNA strand defines a protein, which an organism is liable to manufacture at one or several points in its life using the information of the sequence. The relationship between the nucleotide sequence and the amino-acid sequence of the protein is determined by simple cellular rules of translation, known collectively as the genetic code. Reading along the protein-coding sequence of a gene, each successive sequence of three nucleotides (called a codon) specifies one amino acid.
In many species of organism, only a small fraction of the total sequence of the genome appears to encode protein. The function of the rest is a matter of speculation. It is known that certain nucleotide sequences specify affinity for DNA binding proteins, which play a wide variety of vital roles, in particular through control of replication and transcription. These sequences are called regulatory sequences, and only a tiny fraction of the total that exist have been identified. Junk DNA represents sequences that do not yet appear to contain genes or to have a function.
Sequence also determines a DNA segment’s susceptibility to cleavage by restriction enzymes, the quintessential tools of genetic engineering. The position of cleavage sites throughout the genome determines a human’s DNA fingerprint.
XYY is a trisomy in which a human has an extra Y chromosome. The incidence of this condition is about 1 per 1000 in humans. Other than being slightly taller and having more severe acne than normal, XYY humans are not significantly different from most humans. Studies suggesting that there were more XYY humans incarcerated than chance would suggest have been determined to be procedurally flawed.
IX THE FUNCTION OF SPERM PART ONE
Sperm is carried in a fluid called semen. Semen is a whitish fluid containing water and small amounts of salt, protein, and fructose sugar, and is in itself harmless on the skin or when ingested. Semen can be the vehicle for many sexually transmitted diseases, including HIV, the virus that causes AIDS. Contact with the semen of a human infected with HIV should be avoided, even by persons already infected with the virus.
At the time of orgasm, semen is ejected through the urethra of the penis. When a human is sexually excited, a small amount of a clear fluid (pre-ejaculate) may leak out of the penis before orgasm and ejaculation. This pre-ejaculate fluid may also contain sperm. In 1997 the British Medical Journal reported that humans that had the highest frequency of orgasms had half the death rate of those with the least frequency of orgasms. Orgasms have also been linked to an increased sense of smell, reduction of heart disease, weight loss, overall fitness, reduction of depression, pain relief, a lessening occurrence of flu and colds, better bladder control, greater prostate health and better teeth. Since semen contains zinc, calcium and other minerals known to reduce tooth decay, ingestion of sperm can be considered a healthy dietary supplement. According to a June 2002 article in the Archives of Sexual Behavior, sperm acts as an antidepressant. Dr. Gallup administered the Beck Depression Inventory to 293 subjects on their sexual activities and happiness. The results, confirmed by a second clinical trial of 700 subjects, suggest that subjects who take in sperm are happier, on average, than those whose do not. Access to sperm also appears to lead to more sexual activity: this may be caused by the testosterone and prostaglandin E1 found in sperm.
X THE FUNCTION OF SPERM PART TWO
Reports of alien abduction often include claims of the harvesting of or depositing of sperm. The Christian religion claims that when a sperm cell enters another kind of cell, a soul is created. Castaneda (a 20th Century novelist), claimed that sperm went to the recipient’s brain, causing a pleasant sensation. Bardon (a 20th Century occultist) claimed that retaining sperm in a special container called a condenser could allow the manipulation of energy and magnetic fluid. The Temple ov Psychick Youth claimed that placing sperm on paper while concentrating on a desired goal would make that desired goal occur. The religion of Islam claims that sperm is produced between the backbone and the ribs, and that all kinds of humans generate sperm.
XI THE FUNCTION OF SPERM PART THREE
A majority of the world’s economy, technological progress, art and culture are centered on extracting sperm from one or more human and putting it inside of or in proximity to one or more other humans or images. The second most active engine of the world’s economy, technological effort, art and culture is the prevention of these activities. The entire history of humanity can be explained as the dynamics of these two forces.
Some of the genetic information known to be found in Neanderthals and other early contemporaries with humans is found in sperm. This is true not only in the sense of the trunk of evolution being visible in each of its branches, but in the sense of genetic information found specifically in Neanderthals being found in human sperm – a bending-back of the branch. It is likely that humans and Neanderthals shared a common ancestor, and then Neanderthals were absorbed (in part) back into the human branch of evolution. Some humans exhibit these Neanderthal traits more strongly than others, but no claim is made that they are more Neanderthal than others.
XII THE FUNCTION OF SPERM PART FOUR
Ownership of sperm is increasingly contested in the legal sphere. Sperm donated to a clinic Illinois in 1990 was screened for the disease cystic fibrosis. This sperm was used to create three humans. The sperm donor and the subject knew they had the gene for cystic fibrosis, and therefore sought outside sperm to limit the chance their created human would have this disease. But the sperm screening was ineffective, and one of the created humans had cystic fibrosis. In 1996 a subject in Florida sought sperm to create a human. The subject found a sperm donor, but was not told that the sperm donor was the physician conducting the operation. The subject sued the physician for not using the sperm that the subject wanted to be used. In 1998 a young human died in a game of ‘Russian Roulette.’ The human’s sperm was harvested and frozen until such time as a new human could be created based on the dead human’s sperm. In 1999 a subject in Prague tricked a human into donating sperm to a local sperm bank with the claim this was part of a medical process. The subject actually used the sperm to create two new humans, which the donor human was then was required by to financially support the created humans. In 2002 a human in Sweden was asked by two subjects to donate sperm so they could create humans. When the two subjects parted ways, the courts ruled that the donor human was the legal guardian and was required by to financially support the created humans. Also in 2002, a subject in Japan used sperm from the subject’s dead human partner to create new humans. The courts did not, however, recognize the dead sperm donor as the parent of the created human: this created human is defined by law as having only one biological parent. In 2003 a subject in North Queensland was denied access to the sperm of the subject’s dead partner.
Hymenoepimecis Ichneumondiae is a variety of wasp that has an unusual control over the physiology and behavior of a variety of spider known as Plesiometra Argyra Araneidae. The spider normally spins a web made of sticky spirals, but under the influence of the wasp it spins a completely different sort of web. The wasp stings the spider while the spider is in its web, causing temporary paralysis. The wasp then deposits a cell on the spider and leaves. The cell develops into a larvae. The spider recovers and goes on building and maintaining its web as it had before, while the larval wasp feeds on the haemolymph (blood) of the spider. The sting of the wasp and the feeding of the larvae influence the behavior of the spider. One or two weeks later, when the larva is about to moult, the spider spins a web consisting of four strands supporting a central cocoon. This sort of web is entirely without function for the spider; it does not offer protection nor does it gather food. But when the larva moults, kills and eats the spider, it is a perfect temporary home for the new wasp.
Myxobolous Cerebralis is parasite found in some cold water fish. The parasite is not found exclusively in fish, however, and in fact it depends on other species for the completion of its life cycle. In the first part of its life cycle, the parasite is released from the bodies of infected fish. At this stage the parasite is a spore which can survive drought, freezing and other adverse conditions for decades. The spore enters the second phase of its life cycle when it enters tubifex worms, where it grows into the form that infect fish.
The parasite is released by the worms and enter the bodies of fish through their skin, where it becomes lodged in the fish’s spinal column and nervous system. This is the third stage of the parasite’s life cycle. During this stage, the physiology and behavior of fish changes: the fish grows deformities that make it more visible from the air, and it begins to whirl and thrash near the water’s surface. In the fourth stage of the parasite’s life cycle, the fish (now a highly visible target for aerial predators) are consumed by birds. The parasite passes through the bird’s digestive tract and is returned to the water in a new location by the bird’s fecal matter. At this point the parasite returns to the first stage in its life cycle.
Humans can put sperm in each other and in subjects. Dramatic physiological and behavioral changes can result from this exchange, including (in some cases) the creation of new humans. These newly generated humans sometimes contain sperm cells, and so the human life cycle may continue. No human has ever been generated without sperm: sperm is the agent of all life, and that which is outside of life is the inorganic.
XIV THE PENIS PART ONE
The penis (plural penises or penes) or phallus is the copulatory organ, and, in mammals, the organ of urinary excretion. The sexual organs comprise both the penis and the testes. The penis is capable of erection for use in sexual intercourse. The human penis differs from some other mammalian penises in lacking an erectile bone (instead relying entirely on engorgement with blood to reach its erect state), lacking the ability to be withdrawn into the groin, and being larger than average in proportion to body mass.
The human penis is built of three columns of erectile tissue: the two corpora cavernosa and one corpus spongiosum which lies below them. The end of corpus spongiosum is enlarged and cone-shaped and forms the glans penis. The glans supports the foreskin or prepuce, a loose fold of skin that can retract to expose the glans. It aids in sexual insertion, keeps the glans moist and provides a gliding action which is said to increase sexual pleasure. For various cultural, religious, and (more rarely) medical reasons, the foreskin is sometimes partly or completely removed; this is called circumcision. The area on the underside of the penis, where the foreskin attaches, is called the frenum. The inner portion of the foreskin near the sulcus is a highly innervated area known as the ridged band. Removal of the foreskin by circumcision also usually removes the ridged band and injures or removes the frenulum.
The urethra, which is the last part of the urinary tract, traverses the corpus spongiosum and its end lies on the tip of the glans penis. It is both a passage for urine and for the ejaculation of semen. Sperm is produced in the testes and stored in the attached epididymis. During ejaculation, sperm are propelled up the vas deferens, two ducts that pass over and behind the bladder. Fluids are added by the seminal vesicles and the vas deferens turns into the ejaculatory ducts which join the urethra inside the prostate gland. The prostate as well as the bulbourethral glands add further secretions, and the semen is expelled through the penis.
XV THE PENIS PART TWO
An erection is the hardening, enlarging and rising of the penis which often occurs in the sexually aroused human. In addition to sexual arousal, erections can be caused by friction or by the pressure of the filled urinary bladder. In humans, erections occur several times per night during sleep, and morning erections are common.
Physiologically, an erection is achieved by two mechanisms: increased inflow of blood into the vessels of erectile tissue, and decreased outflow. After a signal from the sympathetic nervous system, muscles in the region relax, allowing more blood to enter the sponge-like tissues. Contraction of other muscles reduce the outflow. The enlarged structure then exerts pressures on the exit vein, further reducing the outflow. As blood flows in, the penis stiffens, its girth and length increases, and it rises to an angle that can vary from horizontal to almost vertical. Normally, the foreskin retracts and exposes the glans. Erections may occur even during or after death, if the pressure within the penis increases for some reason.
XVI THE PENIS PART THREE
In comparison to body size, the human penis is among the largest of the primates. The average human penis is less than the span of a human hand in length when fully engorged with blood during arousal. The size of a flaccid human penis varies in both length and width in ways that often do not predict the size of a fully aroused member. A human with a relatively small flaccid penis may have an above average length penis when fully aroused. The opposite is also true.
The most common form of penile body modification is the practice of circumcision. Less commonly, the penis is pierced and modified by other body art. Piercings of the penis include the Prince Albert piercing, the Apadravya piercing, the Ampallang piercing, the dido piercing, the frenum piercing and others. Apart from a penectomy, the most radical of these is the subincision, in which the glans penis is bifurcated to look similar to that of the kangaroo. This modification was originally done among Australian Aborigines, although it is now done by some in the U.S. and Europe. A small number of humans who are circumcised attempt to restore their foreskin through surgical and other means. This is called foreskin restoration.
XVII THE FUTURE OF SPERM PART ONE
Stem cells are human cells that can be manipulated into becoming other types of cells, and this includes (in theory) sperm cells. Dr Lacham-Kaplan of Monash University in Melbourne successfully created mice without mouse sperm in 1991. Scientists at the Reproductive Genetics Institute in Chicago created a means of creating new humans without sperm in 2002.
This research also opens the possibility of elimination of genetic flaws in humanity at the point of creation, thereby reducing a great deal of human suffering and expense. What is more, better humans can be created – humans able to live longer, healthier lives in a greater variety of environments with less reliance on outside resources.
Efforts to create better humans through manipulation of sperm have already been carried out. In 1989 a study by Wille and Beier compared 99 surgically castrated sex offenders and 35 non-castrated sex offenders ten years after their release from prison. The recidivism rate of castrated offenders was 3%, while the rate for non-castrated offenders was 46%.
Sperm count differs by geographical region. In the United States, New Yorkers issue 102.9 x 100000/mL sperm, Los Angeles humans issue 80.8 x 100000/mL, and Columbia (Missouri) humans issue only an average 53.5 x 100000/mL sperm.
A study conducted in 1999 by The Lancet suggested that out of 650 humans who were unable to create new humans, 20 had been exposed to high levels of pesticides. Information gathered between 1938 and 1990 suggests sperm densities in the United States have an average annual decrease of 1.5 million sperm/mL of collected sample, or about 1.5 percent per year. European sperm has declined at about twice that rate (3.1%/year). As the inability to create new humans increases so does the need to manufacture artificial sperm. In contrast, the bdelloid rotifer has evolved into 370 species over fifty million years: clearly, the need to reproduce with sperm is an option and not a requirement. In 1967, Surveyor 3 landed on the moon. The bacteria Streptococcus mitis was accidentally on board placed there by the sneeze of a NASA worker. The bacteria survived liftoff, space travel, a lack of atmosphere, a lack of food, and three years of cosmic radiation on the surface of the moon. A component of Surveyor 3 was returned to Earth in 1969 by astronaut Conrad, where it was discovered that the bacteria was still alive. In 1997, Cano recovered living bacteria found in the stomach of a bee preserved in amber thirty million years ago.
XVIII THE FUTURE OF SPERM PART TWO
Humans are a sperm’s way of making more sperm, until such inevitable time as we can make our replacements.
(from OVO 15 SPERM February 2005)