Phase Contrast and DIC Comparison

Phase contrast and differential interference contrast (DIC) should be considered as complementary (rather than competing) techniques, and employed together to fully investigate specimen optical properties, dynamics, and morphology. In many cases, each technique will reveal specific details about a particular specimen that is not apparent from observing images captured by other methods. The wide variety of images presented in this gallery are derived from both thick and thin transparent specimens, as well as specimens that have inherent contrast originating from synthetic dyes (stains) or natural pigments.

Aurelia Ephyra-Stage Jellyfish

Members of the jellyfish in the class Scyphozoa undergo a complex life cycle including a larval medusa or ephyra stage. The genus Aurelia demonstrates the typical life stages for this class of invertebrates, which also includes the free-swimming planula, the stalked and tentacled scyphistoma polyp, the strobila bud, and the mature medusa stages.

  • Aurelia Ephyra-Stage Jellyfish - Phase Contrast

    Phase Contrast

    Aurelia Ephyra-Stage Jellyfish - Phase Contrast

    Between the dominant adult medusa stage and the small and inconspicuous larval polyp stage, Aurelia jellyfish undergo the ephyra stage. The common and cosmopolitan moon jelly (A. aurita) is often used as a laboratory experimental and dissection model to illustrate the typical Aurelia life stages. Tiny ephyrae swim free of the sessile scyphistoma polyps. As a dispersal stage, the ephyra allows the jellyfish to spread to potential suitable habitats and prevents the placing of all offspring within one locality where they are subject to changes in environmental conditions and catastrophic events.
  • Aurelia Ephyra-Stage Jellyfish - DIC


    Aurelia Ephyra-Stage Jellyfish - DIC

    In less than a year, the ephyrae mature sexually into medusas. Although not mature, most of the adult characteristics (except gonads) are present in this larval stage, but in different proportions. Most notably, the eight pairs of lappets are disproportionately large in comparison with adult jellyfish of the same species. While lappets are inconspicuous on adult Aurelia members, they dominate the ephyrae. Other body parts, such as the manubrium and the arms, are common to both larval ephyrae and mature medusas in most Scyphozoa species. The rhopalia are eight sensory organs that are evenly spaced around the fringe of the bell of both stages. Each rhopalium contains a statocyst for balance and sensing gravity and an ocellus for photoreception. In the adult stage, the large lappets of the ephyra are reduced to small, triangular sense organs located adjacent to the rhopalia.

Blue-Green (Spirulina) Algae

Blue-green algae growing in natural environments may be composed of numerous species. Because some of them may contain harmful toxins, Spirulina that is intended for human consumption is generally harvested from controlled ponds. In the last few decades, commercial Spirulina systems have developed in many countries, including the United States, Thailand, Taiwan, Japan, Mexico, China, and India.

  • Blue-Green (Spirulina) Algae - Phase Contrast

    Phase Contrast

    Blue-Green (Spirulina) Algae - Phase Contrast

    Historically, Spirulina has been utilized as a food source for thousands of years. However, the algae did not enter into the modern limelight until the early 1980s when it was advertised as an all-natural diet pill. Although some studies suggest that Spirulina is an excellent source of protein and may have some health benefits, there is by no means a consensus on the topic. The amazing claims of miraculous weight-loss and disease recovery that are frequently present in advertisements are not supported by any clear evidence, as was noted by the Food and Drug Administration during its investigation of Spirulina products.
  • Blue-Green (Spirulina) Algae - DIC


    Blue-Green (Spirulina) Algae - DIC

    Blue-green algae growing in natural environments may be composed of numerous species. Because some of them may contain harmful toxins, Spirulina that is intended for human consumption is generally harvested from controlled ponds. In the last few decades, commercial Spirulina systems have developed in many countries, including the United States, Thailand, Taiwan, Japan, Mexico, China, and India. Due to interest in growing Spirulina on a small scale, the first practical startup kits have recently become available for use by small communities and home businesses.

Buccal Epithelial Cells

The human body constantly sheds cheek, or squamous epithelial, cells. Samples can be easily obtained by swabbing the inside of the mouth and are, therefore, often used in school laboratory settings. Scientists also frequently examine cheek cells since they contain human DNA and may hold clues that enable the early diagnosis of certain health conditions.

  • Buccal Epithelial Cells - Phase Contrast

    Phase Contrast

    Buccal Epithelial Cells - Phase Contrast

    Squamous epithelial cells divide about once in every 24-hour period and line the human mouth as part of the buccal muscosa. The cells secrete mucin, the substance that is the principal component of mucus. With the additional help of the salivary glands, the mucin keeps the mouth's interior moist. The mouth needs to maintain moisture in order to help secreted enzymes soften food, facilitate swallowing and begin the digestion process.
  • Buccal Epithelial Cells - DIC


    Buccal Epithelial Cells - DIC

    The nucleus of each tiny cheek cell holds the genetic make-up of the entire body. Consequently, cheek cells are frequently used in diagnostic tests, such as paternity determination, and DNA fingerprinting efforts. A group of scientists in Australia, however, have found a new use for cheek cells. The researchers are examining the sodium transport level of squamous epithelial cells in children to determine whether or not they have a predisposition for developing hypertension. If their studies and testing procedures prove successful, those with a greater proclivity may receive early warning and will be able to take preventative measures to avoid the condition.

Cabbage Clubroot Fungus

Clubroot is a disease caused by the fungus Plasmodiophora brassicae, which affects cabbages and other closely related crops. Early signs of clubroot include a yellowing of leaves and a tendency to wilt, but a characteristic swelling of the roots is the primary symptom of the condition.

  • Cabbage Clubroot Fungus - Phase Contrast

    Phase Contrast

    Cabbage Clubroot Fungus - Phase Contrast

    Presence of the pathogen in soil and proper environmental conditions, such as low pH levels and humidity, initiate the proliferation of clubroot in new plants. The fungus generally enters the plant through the roots, where it initiates the rapid growth of cells and causes the roots to swell with excess tissue. The impaired root system cannot efficiently absorb water or nutrients, leading to a weakening of other parts of the plant. If a plant harboring Plasmodiophora brassicae carries out its full life cycle, the roots eventually decompose and ultimately release more of the fungus into the surrounding soil.
  • Cabbage Clubroot Fungus - DIC


    Cabbage Clubroot Fungus - DIC

    Farmers and gardeners can attempt to stem the disease, but infected plants cannot be saved. Since the fungus survives in soil and crop debris, any movement of dirt can result in instances of clubroot in new areas and should be avoided unless the material can be verified to be pathogen free. Fungicide treated soil, especially if it is alkaline, can help prevent clubroot, but often with limited success. The only sure method of avoiding the disease is to not grow susceptible plants in an infected area for at least ten years, which is the maximum amount of time that the fungus can survive in soil.

Cat Testis Thin Section

The Ancient Egyptians considered cats sacred animals and were the first to domesticate the predators, most likely to control rodent populations around granaries. Though they generally no longer hold a religious status, cats can be found in more homes than ever before. Cats reach a maturity level that allows breeding sometime between seven and twelve months of age. Unlike their wild brethren, cats can have multiple litters in a single year.

  • Cat Testis Thin Section - Phase Contrast

    Phase Contrast

    Cat Testis Thin Section - Phase Contrast

    Cats reach a maturity level that allows breeding sometime between seven and twelve months of age. Unlike their wild brethren, cats can have multiple litters in a single year. Since the average number of kittens in a litter is four, cat populations can increase quite rapidly if efforts are not made to counteract the occurrence of pregnancy. Historically, selective killing was the primary means of keeping newborn numbers manageable, but sterilization has become preferential in present day society. Interestingly, sterilized cars have a longer life expectancy than those that are reproductively unaltered.
  • Cat Testis Thin Section - DIC


    Cat Testis Thin Section - DIC

    Kittens, similar to many other carnivores, are born helpless. They begin blind and deaf and do not develop their senses until many days later. Newborns also generally lack their distinctive coloration, developing their true colors and marking several weeks after birth. For instance, the widely popular Siamese cat is born a solid white, the characteristic dark marks only appearing as they grow older.

Chick Embryo Retina

Composed of many layers, the retina of humans and most vertebrates contains a stratum of rods and cones, the photosensitive cells of the eye. Rods are elongate and are responsible for perceiving the basics of a visual image, such as size, shape, and intensity. Cones, on the other hand, are shorter than rods and can perceive color and subtle detail. They are also less sensitive to light than rod cells and are significantly less numerous.

  • Chick Embryo Retina - Phase Contrast

    Phase Contrast

    Chick Embryo Retina - Phase Contrast

    Composed of many layers, the retina of humans and most vertebrates contains a stratum of rods and cones, the photosensitive cells of the eye. Rods are elongate and are responsible for perceiving the basics of a visual image, such as size, shape, and intensity. Cones, on the other hand, are shorter than rods and can perceive color and subtle detail. They are also less sensitive to light than rod cells and are significantly less numerous.
  • Chick Embryo Retina - DIC


    Chick Embryo Retina - DIC

    As one of the most simply structured parts of the central nervous system and because it is located accessibly outside the skull, the retina is often used in experiments. Since studies on humans, however, are generally not possible or practical, other animals are frequently exploited. The chick embryo is often a prime choice because it is a higher vertebrate that can easily be manipulated and observed during the entire process of embryonic growth through the use of eggs with a window in the shell or even eggshell free cultures.

Cyanobacteria (Tolypothrix)

Tolypothrix is a genus of cyanobacteria that occurs in small tufts either floating in torpid water or attached to plants and rocks. Cyanobacteria are the oldest known fossils, dating back over three and a half billion years.

  • Cyanobacteria (Tolypothrix) - Phase Contrast

    Phase Contrast

    Cyanobacteria (Tolypothrix) - Phase Contrast

    Frequently referred to as blue-green algae, cyanobacteria are photosynthetic and can manufacture their own food. However, though cyanobacteria resemble algae in many ways, they are prokaryotic and are classified with other bacteria in the kingdom Monera. The characteristic blue-green color they are known for is a result of a combination of chlorophyll and the blue pigment phycobilin. Yet, some species may contain additional pigments and may appear in various other colors, such as black, brown, yellow, and red.
  • Cyanobacteria (Tolypothrix) - DIC


    Cyanobacteria (Tolypothrix) - DIC

    Cyanobacteria are important to life on Earth in many ways. The oxygen in the atmosphere that humans depend upon was largely generated by an abundance of cyanobacteria billions of years ago. Cyanobacteria help convert atmospheric nitrogen into a form that can be consumed by plants and are, therefore, useful as a natural fertilizer that is beneficial to crop cultivation around the world. Moreover, the organisms are active in reducing erosion by facilitating the binding together of soil particles and many have formed symbiotic relationships with other plants.

Cycloid Fish Scale

The principal purpose of scales is to give fish external protection, but not all fish species have them. However, those that do may be covered in scales of various shapes, sizes, and types. The primary categories of fish scales are placoid, cosmoid, ganoid, cycloid and ctenoid scales.

  • Cycloid Fish Scale - Phase Contrast

    Phase Contrast

    Cycloid Fish Scale - Phase Contrast

    Cycloid scales are smooth, flat, round and consist of two distinct regions. The deeper fibrous layer is mainly composed of collagen and the outer bony layer is an organic framework saturated primarily with calcium-based salts. Cycloid scales grow larger with the fish they cover, which sometimes result in growth rings that are similar to those found in trees. When weather is cooler, cycloid scales grow more slowly and the rings lie closer together, leaving a dark band known as an annulus. Biologists can estimate the age of fish by counting the annuli on its scales, a feat that can be extremely useful in scientific studies.
  • Cycloid Fish Scale - DIC


    Cycloid Fish Scale - DIC

    Cycloid scales are most often found on advanced fish species, such as trout, herring, and carp. However, fish are not necessarily covered in a single type of scales. Some species, such as flounders, have ctenoid scales on one side of the body and cycloid scales on the other. Scale type can also vary depending on the sex of the fish. The males of certain species may be covered in ctenoid scales, although the females are enveloped in cycloid scales.

Diatom Frustule

Diatoms are unicellular algae that inhabit both fresh and salt water, sometimes living together in colonies. Typically classified as members of the phylum Bacillariophyta, the estimated 16,000 species of diatoms that exist compose an important link in the aquatic food chain.

  • Diatom Frustulex - Phase Contrast

    Phase Contrast

    Diatom Frustule - Phase Contrast

    Each individual diatom possesses a cell wall known as a frustule that consists of overlapping halves, similar to a pillbox. Covered in delicate markings and intricate designs, diatom frustules are primarily composed of silica and are valuable for testing a microscope's resolving power. Reproduction of diatoms is usually asexual, the frustule halves separating and secreting new, smaller bottom halves. Since diatoms decrease in size each time they divide, periodic spore formations are needed in order for the diatoms to be restored to their initial dimensions.
  • Diatom Frustule - DIC


    Diatom Frustule - DIC

    Diatoms, an estimated 6 million of which may be found in a single cubic foot of salt water, are both prolific and important. Most diatoms are free-floating and serve as a food source form many other animals. Diatomaceous earth, a material consisting of fossilized diatoms, is often a component of various products, such as filters, insulation, abrasives, paints, and varnishes. Moreover, the extensive fossil record of diatoms has made them extremely useful to scientists researching changes in ecological conditions over long periods of time.

Fat-Stained Adipose Tissue

Adipose tissue is a connective tissue that specializes in the synthesis and storage of fat reserves. In mammals, adipose tissue exists in both a brown and a white form, each serving different bodily needs.

  • Fat-Stained Adipose Tissue - Phase Contrast

    Phase Contrast

    Fat-Stained Adipose Tissue - Phase Contrast

    White adipose tissue primarily stores energy in the form of long-chain fatty acids and triglycerides. However, the tissue, which is usually directly below the skin, also acts as a cushion that protects against bodily impact and as insulation to keep the body warm. Depending upon the species and age of an organism, brown adipose, which derives its coloration from densely packed mitochondria, may be found in a variety of locations in the body. The tissue is more metabolically active in hibernating animals and can be activated by cold weather.
  • Fat-Stained Adipose Tissue - DIC


    Fat-Stained Adipose Tissue - DIC

    Adipose tissue may atrophy as a result of prolonged periods of undernutrition or, in a localized area, from injury. Atrophy in a specific area is known as lipodystrophy and is sometimes a primary symptom of a disease of unknown origin that mainly affects women. Frequently beginning at a young age, victims of the disease suffer the progressive wasting of adipose tissue. The face, arms, and trunk are the areas most affected as the number of their specialized fat-holding cells drastically diminishes.

Fern (Polypodium) Leaflet

A genus of fern, Polypodium plants are most often found in the New World. The plants grow above ground, but are usually supported by another object and are frequently seen growing from rocks and tree trunks.

  • Fern (Polypodium) Leaflet - Phase Contrast

    Phase Contrast

    Fern (Polypodium) Leaflet - Phase Contrast

    The ferns constitute an ancient division of vascular plants, some of them dating back 360 million years ago to the Carboniferous Period. There are an estimated 12,000 fern species, approximately 75 of which are members of the Polypodium genus. In addition to acting as common ornamental plants, humans utilize many of the Polypodium ferns for medicinal purposes. For instance, the common polypody, P. vulgare, which is found on shady rocks and in mountainous areas of the United States, may help eliminate parasites, act as a purgative, and aid in treatments for pulmonary and hepatic diseases. The rhizome of the plant is considered to be the pharmaceutically active part and has a long history of use.
  • Fern (Polypodium) Leaflet - DIC


    Fern (Polypodium) Leaflet - DIC

    The size and shape of fern fronds vary greatly by species, but most are quite similar at the tissue level. Leaflets have an upper and a lower epidermis, the latter of which contains numerous microscopic pores. Between the layers is the mesophyll, generally composed of cells with large intercellular spaces. However, in many ferns the mesophyll was eliminated at some point during evolution and, therefore, photosynthesis primarily takes place in the epidermal layers. Veins of ferns range widely in size, from massive midribs to delicate capillaries.

Frog Testis Stained Thin Section

The breeding behavior of frogs is one of their most distinctive characteristics. The annual occurrence takes place in freshwater, usually in still or slow-moving areas. Some species, however, have adapted sexual organs, such as enlarged testes that produce massive amounts of sperm, that enable fertilization to take place in rapidly flowing waters.

  • Frog Testis Stained Thin Section - Phase Contrast

    Phase Contrast

    Frog Testis Stained Thin Section - Phase Contrast

    Frogs inhabit almost every part of the world and breed in a wide variety of areas. Since eggs can only develop in moist conditions, many frogs flock to temporary pools during their brief breeding seasons, but others reproduce in streams and water bodies that they always inhabit. Male frogs use mating calls to attract females, which can differentiate between their species and others based on the sound and location of the call. When a female reaches a calling mate, the male clasps her in a tight embrace, known as amplexus, in order to fertilize the eggs. The female then selects the site for egg deposition.
  • Frog Testis Stained Thin Section - DIC


    Frog Testis Stained Thin Section - DIC

    Although frogs are not generally aggressive, during breeding season they may become territorial and antagonistic. Males of many species will wrestle, kick, and bite in order to protect their calling areas. Moreover, some frogs that use boulders and other raised surfaces as calling sites may attempt to knock competitors into the surrounding waters. Males are the most frequent fighters, but female frogs, such as the Venezuelan Colostethus trinitatus, are also willing to exhibit aggressive behavior in order to protect egg-laying sites.

Giant Leopard Moth Wing Scales

The giant leopard is one of the most eye-catching moth species. With large white wings covered in blue or black spots, the giant leopard moth soars through the night skies of eastern North America. Exclusively nocturnal, the adults feature ultrasound-sensitive ears, which offer protection against bats, as well from terrestrial predators.

  • Giant Leopard Moth Wing Scales - Phase Contrast

    Phase Contrast

    Giant Leopard Moth Wing Scales - Phase Contrast

    The female giant leopard moth is much larger than the males of her species and can be differentiated by her dark brown or yellow abdomen marked with black spots and broad bluish bands. After dark, the sedentary female moth extends a scent gland from the tip of her abdomen and releases her airborne pheromones. Night-flying males zigzag their way to the receptive female, picking up the gradient of chemical attractants with their well developed, long, thin, curled antennae. After mating, the males fly off to seek another mate, while the female oviposits her eggs on a wide variety of host plants, including violets, plantains, cherries, maples, and willows.
  • Giant Leopard Moth Wing Scales - DIC


    Giant Leopard Moth Wing Scales - DIC

    When disturbed or threatened, the giant leopard moth larva curls up into a black, hairy ball and reveals its bright red intersegmental rings. The large caterpillar's spiracles are also ringed in bright red, which completes a warning coloration that discourages predation. The giant woolly bear's long black setae cause skin irritations and, in some cases, more serious allergic reactions when handled. Each hair bears numerous minute barbs and the defensive compounds stored in the hollow setae work by entering scratches and other wounds created by the barbs.

HeLa Cell Culture

HeLa cells have been cultured continuously for scientific use since they were first taken from the tumor of a woman suffering from cervical cancer in the 1950s. They have been utilized for many purposes, including the development of a polio vaccine, the pursuit of a cure for diseases such as leukemia and cancer, and the study of the cellular effects of drugs and radiation.

  • HeLa Cell Culture - Phase Contrast

    Phase Contrast

    HeLa Cell Culture - Phase Contrast

    The woman from which the HeLa cells are derived was named Henrietta Lacks, and she was a wife and mother of five when she passed away at John Hopkins University at the age of thirty-one. A sample of one of her tumors was sent to George and Maragret Gey who had been seeking a line of human cells that would survive indefinitely outside the body for research purposes. The tumor cells they received multiplied like nothing they had ever seen before and soon the cells, dubbed HeLa in a truncated form of Lacks' name, were being shipped to their colleagues stationed around the world. The cells later became a laboratory standard and have even been grown in space.
  • HeLa Cell Culture - DIC


    HeLa Cell Culture - DIC

    Interestingly, the aggressive nature of HeLa cells in culture led not only to scientific discoveries, but also to experimental mistakes. HeLa cells can easily invade other cultures during routine lab transfer procedures and had contaminated many other cell lines used in research by the late 1960s. As a result, numerous research papers that were published based on a variety of cultured cell types have subsequently been proven to be HeLa cells and have, therefore, been discounted.

Heliozoans (Actinophrys sol)

Actinophrys sol is a fresh-water species of heliozoa frequently referred to as the sun animalcule. The name spawns from the numerous radiating pseudopodia that surround the spherical organism, which give it a sun-like appearance under the microscope.

  • Heliozoans (Actinophrys sol) - Phase Contrast

    Phase Contrast

    Heliozoans (Actinophrys sol) - Phase Contrast

    The pseudopodia of Actinophrys species and other heliozoans are generally used to capture prey. However, the cytoplasmic extensions can also be utilized to some extent for locomotion of the organisms. Heliozoans contain several large vacuoles and feed by engulfing their prey through a process known as phagocytosis. The tiny creatures consume almost anything in their path, primarily protozoa and algae, paying little heed to the size of their prey.
  • Heliozoans (Actinophrys sol) - DIC


    Heliozoans (Actinophrys sol) - DIC

    Found predominantly in freshwater, Actinophyrs sol is common in lakes, ponds, and pools. The species usually reproduces via binary fission, but can also propagate through autogamy, which results in zygotes that are able to defer development until conditions are suitable. A similar species, Acanthocystis turfacea, colored by the green algae with which it lives in symbiosis, is frequently called the green sun animalcule.

Human Erythrocytes

Blood is essential to human life, delivering vital elements and removing harmful wastes during its cycle throughout the body. All human blood is composed of the same basic elements, but antigens on the surface of red blood cells produce differences in blood types. When discordant types of blood are mixed within the body, the reaction can be fatal.

  • Human Erythrocytes - Phase Contrast

    Phase Contrast

    Human Erythrocytes - Phase Contrast

    Each component of blood has its own individual and beneficial characteristics. Plasma is primarily water, but also contains sugar, fat, protein, salts, and chemicals that aid in blood clotting. Red blood cells contain hemoglobin, which transports oxygen and carbon dioxide throughout the body as needed and is responsible for the color of the cells. White blood cells are larger than the red counterparts and produce antibodies that help fight bodily infection and disease. Platelets, however, are fragments rather than complete cells. If the body suffers an injury, platelets gather and stick to the edges of the wound, as well as release chemicals that help start the clotting process.
  • Human Erythrocytes - DIC


    Human Erythrocytes - DIC

    The blood type from an individual can be of critical importance and is determined before birth. One gene copy comes from each parent, combining to determine blood type by causing proteins called agglutinogens to exist on the surface of red blood cells. If an incompatible type of blood enters a body through a transfusion, special antibodies, known as agglutinins, in the recipient's blood will attack the foreign blood and cause blood clots to form. Although stringent testing methods are implemented, accidents do occur and transfusion patients sometimes receive the wrong blood type. In hopes of alleviating the risk, scientists are trying to find ways to chemically convert all donated blood into type O, which is compatible with all blood types.

Intercellular Bridges

When tissue is prepared for microscopy, the cells shrink and pull apart from each other, but remain attached to neighboring cell membranes via desmosomes. The intercellular bridges that can sometimes be observed are actually tiny extensions of cytoplasm connected to the desmosomes.

  • Intercellular Bridges - Phase Contrast

    Phase Contrast

    Intercellular Bridges - Phase Contrast

    Desmosomes are major tissue stabilizing elements that consist of dense plaques on two opposing cytoplasmic membranes. Cell adhesion proteins cross the intercellular space and bind adjacent cells. The gap between cell membranes is filled with amorphous material that can move freely around the connected areas. Desmosomes and their accompanying intercellular bridges are particularly prominent in tissues that have to endure mechanical stress, such as skin.
  • Intercellular Bridges - DIC


    Intercellular Bridges - DIC

    The basic function of the cutaneous desmosome is to assure the epidermal integrity by attaching the cytoskeleton of a cell to the cytoskeleton of the adjacent cell. Desmosomes are also important because they play a role in epithelial morphogenesis and differentiation. Moreover, the proteins of desmosomes are major antigens in autoimmune skin disorders, such as pemphigus. Pemphigus is characterized by the separation of skin cells, causing burn-like lesions and blisters.

Lancelet (Amphioxus) Pharynx

The amphioxus is a small, slender fish-like organism that spends the majority of its time buried in gravel or mud on the ocean floor. Sometimes alternatively referred to as lancelets, the marine animals rarely grow longer than a few inches long and are most often found around the coasts of warm regions of the world.

  • Lancelet (Amphioxus) Pharynx - Phase Contrast

    Phase Contrast

    Lancelet (Amphioxus) Pharynx - Phase Contrast

    When Piotr S. Pallas discovered amphioxi in 1778, he misidentified the marine animals as slugs, an understandable mistake most likely caused by their tapered, sheathed forms without eyes or defined heads. The creatures, which do not have brains or hearts, most often swim at night. To do so, amphioxi contract the staggered muscle blocks that line both sides of their bodies, moving from side to side. Since they are not buoyant, whenever the invertebrates cease to swim, they sink. During the daytime, amphioxi usually remain buried under the bottom of the ocean, but allow the anterior end of their bodies to protrude during feeding so that they can filter particles that pass through their gill slits.
  • Lancelet (Amphioxus) Pharynx - DIC


    Lancelet (Amphioxus) Pharynx - DIC

    Unlike other members of the phylum Chordata, amphioxi are capable of phagocytosis, a digestive process in which food particles are consumed by individual cells. The oral cavity of the small animals is lined with cirri, which act as a food filtration system. Cilia fringing the gill slits direct water through the small mouth opening of the organism into the pharynx. The mucous membrane of the gill basket catches food particles in the water and passes them to the gut where they are exposed to various enzymes that initiate digestion.

Lichen Thallus

The classification of lichens has been tremendously problematic for taxonomists. Once thought to be a single organism, microscopy revealed that lichens are a structure composed from a symbiotic relationship between two distinct organisms, fungi and algae. Although each individual species can flourish independently, in certain harsh environments they must work together in a mutually beneficial relationship in order to endure.

  • Lichen Thallus - Phase Contrast

    Phase Contrast

    Lichen Thallus - Phase Contrast

    Certain characteristics make algae and fungi extremely useful to each other. Algae form simple carbohydrates that are excreted and subsequently absorbed and transformed by fungi cells. Algae also produce several vitamins that are required by fungi. In return, fungi absorb water vapor from the air and provide shade for the algae, which are very sensitive to light. Working together in such ways enables lichens to colonize extremely inhospitable areas, including bare rock, solidified lava flows, and regions at temperature extremes.
  • Lichen Thallus - DIC


    Lichen Thallus - DIC

    Fungi and algae retain their individual genetic make-up even in symbiosis, but the composite body they form is known as a thallus. The shape and appearance of lichens is dependent on the species of fungi present, not the algae. Lichens grow relatively slowly and their propagation is unclear. Scientists generally agree, however, that the most frequent kind of lichen reproduction is vegetative, a portion of an existing lichen breaking away and starting a new growth in an adjacent area.

Mouse Intestine

Mice are not a distinct species or group of animals. The term is commonly applied to small rat-like rodents in a number of families, but most species are members of Muridae. The intestines of mice are similar to those of most vertebrates, primarily absorbing water and electrolytes from digestive residues and storing fecal matter.

  • Mouse Intestine - Phase Contrast

    Phase Contrast

    Mouse Intestine - Phase Contrast

    Due to their similarities to humans, mice are frequently used for scientific study and research. Laboratory mice are not collected from the wild, but are a special breed of house mice. The small creatures are much easier to handle and less expensive to rear than large mammals, which are generally not practical for laboratory use. Mice are also useful in study because their reproduction is rapid and prolific, allowing scientists to see prompt results of their actions.
  • Mouse Intestine - DIC


    Mouse Intestine - DIC

    Although science has found a noble purpose for the animals, most humans generally consider mice a nuisance. The rodents are extremely hearty and can exist almost anywhere if humans are also present to provide warmth and food. Perhaps not as objectionable as rats, mice are more common than their rodent comrades and cause a significantly greater amount of damage. Rodent infestations have been a long-term problem for homeowners, a fact demonstrated by the rat and mice bones that have been unearthed in the cave dwellings of prehistoric man.

Mouse Kidney Thick Section

The kidney is an organ that maintains water balance and expels metabolic wastes in vertebrates and some invertebrates. Primitive and embryonic kidneys have sets of specialized tubules that empty into two collecting ducts that pass urine into a primitive bladder. The more advanced mammalian kidney is a paired compact organ with functional units, called nephrons, that filter the blood, reabsorbing water and nutrients and secreting wastes, producing the final urine.

  • Mouse Kidney Thick Section - Phase Contrast

    Phase Contrast

    Mouse Kidney Thick Section - Phase Contrast

    Mouse kidneys are located on the dorsal (upper) wall of the abdominal cavity and are securely held in place by fibrous capsules. Like other mammalian kidneys, the outer layer of the kidney is brownish red and granular in appearance, with a firm consistency. Mouse kidneys are similar to human kidneys, which is why they are often used to simulate human kidneys in scientific studies. Mice have played a significant role in experiments used to diagnose the possible cause and treatment of IgA nephropathy, or Berger's ("burrjays") Disease. This is the most common non-diabetic kidney disease and affects as many as two to four percent of the world's population.
  • Mouse Kidney Thick Section - DIC


    Mouse Kidney Thick Section - DIC

    Laboratory mice represent specialized breeds of house mice and are used in many scientific experiments because of their close mammalian relationship to humans. Compared to larger mammals, mice and other rodents are small, easy to handle, inexpensive to house, and breed quickly. During the Twentieth Century, scientists bred different strains of mice with genetic deficiencies in order to produce models for human diseases.

Nucleic Acid Stains in Animal Cells

Cells are the basic building blocks of all living organisms. While describing plant tissues in 1665, Robert Hooke first coined the term because the cellulose walls of cork that he was able to see through his microscope reminded him of the cells inhabited by monks. The images presented below compare a thin section of animal tissue stained for the nucleic acids RNA and DNA.

  • Nucleic Acid Stains in Animal Cells - Phase Contrast

    Phase Contrast

    Nucleic Acid Stains in Animal Cells - Phase Contrast

    The finer points of cellular purpose and composition were not understood form many years, slowly developing as microscopes improved. In fact, the realization that cells were the fundamental unit of plants and animals did not occur until the 1830s. Previously cells had been believed to be simply pores, but the detection of nuclei and moving protoplasm put an end to the misconception. For other discoveries, additional microscopical enhancements needed to be made. Walter Flemming's advanced methods of fixing and staining cells, for instance, facilitated his observation of chromosome transmission between cells and led to his very precise account of mitosis and cell division in 1882.
  • Nucleic Acid Stains in Animal Cells - DIC


    Nucleic Acid Stains in Animal Cells - DIC

    Recent experimentation has been aimed at utilizing animal cells for human recovery from diseases, such as Parkinson's. Scientists hope to use cloned cells to replace improperly functioning cells in patients, thereby reducing tremors and other symptoms. Although the research is in its early stages, if it proves successful the medical world could be revolutionized. However, concerns such as the possibility of transmitting animal disease to humans through cell transplantation and the ethics of genetic cloning are problems that may hinder future developments.

Obelia Hydroid Polyp Stage

Obelia is the primary genus of widely distributed animals belonging to the phylum Cnidiria. Members of Obelia must complete two generations, each with its own form and set of behaviors, in order to finish a single life cycle.

  • Obelia Hydroid Polyp Stage - Phase Contrast

    Phase Contrast

    Obelia Hydroid Polyp Stage - Phase Contrast

    Members of the first generation of Obelia exist as branching stalk-like polyps that live in colonies. Through filaments, Obelia attach to various surfaces, most often the ocean floor, but sometimes seaweed, shells or wharves. Reproduction of Obelia in this life stage occurs by budding, new polyps growing and breaking away to become members of the increasingly larger colony. Two different types of polyps exist together in the colonies of Obelia, each serving different primary purposes. The role of gastrozooids, which have mouths surrounded by tentacles tipped with stinging cells, is to capture and consume food. The reproductive duties, however, belong to the gonzooids, which create the successive generation, small jellyfish known as medusae, via budding.
  • Obelia Hydroid Polyp Stage - DIC


    Obelia Hydroid Polyp Stage - DIC

    When the young medusae swim away from their parent gonzooids, the second generation truly begins. The umbrella shaped creatures have tentacles covered in nematocysts and suctorial pads that assist in capturing prey. Reproduction of Obelia medusae occurs sexually, eggs and sperm uniting to become small larvae surrounded by cilia. Although, beginning as a free moving individual, the larvae eventually settle, each one becoming the founding member of a new polyp colony.

Salamander Liver Tissue Mitochondria

Amphiumas are a genus of aquatic salamanders that spend the majority of their lives burrowed in mud and debris. Due to the extremely small size of their limbs, the creatures are frequently mistaken for snakes or eels from a distance.

  • Salamander Liver Tissue Mitochondria - Phase Contrast

    Phase Contrast

    Salamander Liver Tissue Mitochondria - Phase Contrast

    Three species of Amphiuma exist and can be differentiated by their number of toes. The two-toed Amphiuma means is the most widely distributed, but there are also three-toed and one-toed varieties that can be found in wetland areas of the southeastern United States. The elongate bodies of Amphiumas can reach up to three feet in length, dependent on species, and their body color is generally dark brown or gray. The undersides of Amphiumas, however, are usually a lighter shade than the rest of their bodies.
  • Salamander Liver Tissue Mitochondria - DIC


    Salamander Liver Tissue Mitochondria - DIC

    As predators, Amphiumas have large mouths and numerous very sharp teeth. Their diet typically consists of worms, insects, mollusks, crustaceans, small fish, frogs and other small animals. Females are fertilized internally and can deposit up to 200 eggs at a time under large objects or in depressions in the mud, an area they guard until hatching. As tadpoles, Amphiumas are only a few inches long and have gills and all four limbs. When they grow to maturity, however, only the gill slits remain.

Spirogyra Algae

The filamentous algae genus Spirogyra owes its name to the characteristic spiral shape of the chloroplasts possessed by its members. Sometimes alternatively known as water-silk, mermaid's tresses, or pond scum, a large presence of the unbranched algae often indicates the nutrient enrichment of freshwater bodies.

  • Spirogyra Algae - Phase Contrast

    Phase Contrast

    Spirogyra Algae - Phase Contrast

    More than 400 species of Spirogyra have currently been catalogued, all of which can be differentiated by the spores they produce during sexual reproduction. Spirogyra usually reproduce via vegetative means, individual filaments fragmenting to form new algal strands. However, during periods of poor environmental conditions, Spirogyra may switch to a sexual means of proliferation. Adjacent filaments are capable of extending conjugation tubes toward each other in order to exchange genetic material and produce a zygospore, which is protected by a thick cellular wall that enables it to survive in sediment until more favorable conditions emerge.
  • Spirogyra Algae - DIC


    Spirogyra Algae - DIC

    On sunny days, mats of tangled Spirogyra usually float on the surface of the water, kept afloat by tiny bubbles of oxygen created through photosynthesis. The algal mats sink when the sun goes down and the process reverses as the level of photosynthesis diminishes. Subsequently, the algal strands consume oxygen for cellular respiration and produce carbon dioxide as a waste product. In highly fertile areas, thick algal mats may cause large fluctuations in the dissolved carbon dioxide and oxygen content of the water body. The resulting changes in the water's pH can occur rapidly, leading to stress and even death of other organisms present in the environment.

Sweet Flag (Acorus) Rhizome

Acorus is the only genus in the plant family Acoraceae and its members are commonly known as sweet flag. Humans have utilized the grass-like perennial plants that grow in wetlands and around freshwater bodies for thousands of years.

  • Sweet Flag (Acorus) Rhizome - Phase Contrast

    Phase Contrast

    Sweet Flag (Acorus) Rhizome - Phase Contrast

    Sweet flag plants have long, narrow, aromatic leaves, greenish brown cylindrical flowers, and roots that spread close to the surface of the soil. A thick subterranean stem, known as the rhizome, enables the propagation of sweet flag by producing shoots and root systems that develop into new individuals. The rhizomes of sweet flag plants also maintain food reserves and allow the species to survive cold winter weather, sprouting again the following spring.
  • Sweet Flag (Acorus) Rhizome - DIC


    Sweet Flag (Acorus) Rhizome - DIC

    In Ancient Egypt and the Far East, sweet flag rhizomes were believed to act as potent aphrodisiacs, but they have since been used for many other purposes. Once consumed as a candy by the Dutch, rhizomes of sweet flag plants have sometimes been employed to fight infectious diseases and to make products such as tea and dry shampoo. Other parts of sweet flag plants and their extracts enjoy a long history of utility, as well, especially as components of medicinal remedies. However, modern studies suggest that some sweet flag species have carcinogenic properties and, consequently, the plant extracts have been banned from products intended for human consumption by the Food and Drug Administration.

Tapeworm Echinococcus granulosus Hydatid Cyst

Echinococcus granulosus is a tapeworm parasite that in its larval form can cause hydatid disease, which is characterized by cysts forming within the victim's body. In order to complete its lifecycle, the tapeworm must infect two hosts, a carnivore and a herbivore.

  • Tapeworm Echinococcus granulosus Hydatid Cyst - Phase Contrast

    Phase Contrast

    Tapeworm Echinococcus granulosus Hydatid Cyst - Phase Contrast

    The adult form of Echinococcus granulosus exists benignly in carnivores, which are primarily infected by eating the raw or undercooked internal organs of other animals that contain hydatid cysts. The tapeworm larvae that fill the cyst are released into the animal's body after the cyst wall is digested. The larvae attach themselves to the intestines, where they grow into egg-producing adults. When the eggs are passed outside the body with excretory material, they may then by digested by grazing animals. The eggs hatch within the herbivorous host and travel throughout the body, settling into tissue and developing into cysts.
  • Tapeworm Echinococcus granulosus Hydatid Cyst - DIC


    Tapeworm Echinococcus granulosus Hydatid Cyst - DIC

    Hydatid disease is most frequently associated with sheep herding, but humans should wear gloves when handling scat, and avoid allowing their pets to lick them on the mouth, in order to decrease the possibility of becoming infected by a tapeworm-infested dog or cat. Yet, even if the parasite does find a way into a human host, infection does not always lead to serious health effects. Cysts may exist in humans for many years before symptoms become apparent and, occasionally, there are never any signs of illness. The cysts can become extremely problematic, however, if they grow to large sizes, develop on the brain, or rupture.

Tilia Stem Thin Section

The Tilia species are deciduous trees that grow in northern temperate climates and may live as long as 1,000 years and reach heights of up to 90 feet. Tilia americana, also known as the American basswood or linden, has a large round crown that makes the species an excellent shade tree on warm, sunny summer days.

  • Tilia Stem Thin Section - Phase Contrast

    Phase Contrast

    Tilia Stem Thin Section - Phase Contrast

    Basswoods are also prized for their beautiful and fragrant flowers. In June and July, between shiny green heart-shaped leaves, small creamy colored blossoms exude a delightful smell similar to that of honey. Bees frequently visit the aromatic blooms to partake of their sweet nectar. The honey produced by bees that feed solely on basswood trees is pale and has a unique, but delicious flavor.
  • Tilia Stem Thin Section - DIC


    Tilia Stem Thin Section - DIC

    Basswood trees, which are the softest of the hardwoods, have tall, straight trunks and are used by humans for a variety of purposes. Frequently a choice of wood carvers, basswood is generally lightweight, light-colored, and has a fine, even texture. Basswood timber is most often used in the manufacture of cooking utensils, furniture, toys, veneer, paper pulp, pianos, and guitars. The fiber of the inner bark of basswood trees is also useful and can be employed to make items such as baskets and mats. Native Americans even used the material to construct an especially durable form of rope.

Tooth Stained Thin Section

On land, the mammal with the most teeth is the giant armadillo, which can have as many 100 teeth in its mouth. In water, the long-snouted spinner dolphin exceeds that number, possessing as many as 252 teeth in its long thin jaws. Humans have comparatively few, producing only 20 primary teeth and 32 permanent ones.

  • Tooth Stained Thin Section - Phase Contrast

    Phase Contrast

    Tooth Stained Thin Section - Phase Contrast

    All true teeth have certain characteristics in common and are composed of three layers. The innermost section of a tooth is the pulp, which consists of small blood vessels, cells, and a nerve. The pulp nourishes the dentine that is similar in composition to bone and comprises the bulk of each tooth. Enamel (illustrated above), the hardest substance of the body, covers the dentine of the tooth's crown. Due to the enamel, the teeth of mammals are the part most often fossilized and since the number, size, organization and shape of the teeth are different in every species, they are extremely useful for taxonomy.
  • Tooth Stained Thin Section - DIC


    Tooth Stained Thin Section - DIC

    Mammalian teeth have evolved into different forms because they are used for different purposes. Elephant tusks, which can be used for defense and for lifting, are actually modified incisors and are the largest teeth in the world. The lower incisors of pigs are close together and projected forward so that they can be used as a tool for digging. Baboons feature enlarged canine teeth that are utilized for defense and display. However, the sawfish may be the most unusually adapted since it is the only animal with true teeth outside its mouth. Members of the species utilize the teeth on the sides of their snouts to lacerate prey.

Vas Deferens Stained Thin Section

The vas deferens is part of the male reproductive system in mammals. Each of the pair of tubes possesses strong muscles that are utilized to transport sperm from the testes to the urethra.

  • Vas Deferens Stained Thin Section - Phase Contrast

    Phase Contrast

    Vas Deferens Stained Thin Section - Phase Contrast

    A congenital bilateral absence of the vas deferens ((CBAVD)) is sometimes an underlying cause of sterility in men. Certain techniques, however, have been developed that enable men having the condition to father children. Yet, the advisability of assisted reproduction in such cases is questionable. Scientists have genetically linked the condition to another disease, and men with CBAVD are believed to be more likely to produce children with cystic fibrosis.
  • Vas Deferens Stained Thin Section - DIC


    Vas Deferens Stained Thin Section - DIC

    When a man elects to have a vasectomy, each of his vas deferens is surgically affected. During the male sterilization process, two small incisions allow a physician to sever and then seal each tube. The relatively simple procedure is sometimes performed to help prevent infections rather than to inhibit reproduction and is generally considered permanent. However, the process can sometimes be reversed and success rates are likely to improve with further advances in microsurgery.

Whipworm Eggs (Trichuris trichiura)

Whipworms are intestinal parasites belonging to the genus Trichuris that infect mammalian hosts. The common name of the nematodes is based on the characteristic shape of the adult species.

  • Whipworm Eggs (Trichuris trichiura) - Phase Contrast

    Phase Contrast

    Whipworm Eggs (Trichuris trichiura) - Phase Contrast

    Trichuris trichiura is the whipworm species that primarily infects humans. Greater incidence of infection is present in regions with heavy rainfall, a subtropical climate, or highly polluted soil. Infection rates are also highest in children, who may play in soil contaminated with eggs of the parasite and do not always understand the necessity of good hygiene. Some human hosts do not suffer any symptoms related to whipworm infection, but if the parasite burden is high enough diarrhea, dysentery, anemia, pallor, loss of appetite, and other problems may arise. In cases involving large infestations in children, physical and mental retardation can occur.
  • Whipworm Eggs (Trichuris trichiura) - DIC


    Whipworm Eggs (Trichuris trichiura) - DIC

    Whipworm infections transpire as a result of accidental ingestion of Trichuris trichiura eggs or embryos. After they are swallowed, the eggs move to the host's small intestine, where they develop into juveniles. The young worms then move to the large intestine and attach their anterior ends to the intestinal wall. After approximately three months, the parasite becomes a sexually mature adult, females producing up to 10,000 eggs per day, which are passed out of the host's system with digestive wastes. The eggs need a warm moist environment to survive outside the body and become infective in about three weeks. Since whipworms do not actually multiply inside a host, each individual worm represents a separate incident of infection.

Zygnema Filamentous Algae

A genus of filamentous freshwater algae, Zygnema features two stellate chloroplasts per cell. There are numerous species of Zygnema, which are distinguishable by the shape, size, and other characteristics of the zygospores they produce.

  • Zygnema Filamentous Algae - Phase Contrast

    Phase Contrast

    Zygnema Filamentous Algae - Phase Contrast

    Zygnema species are often found alongside another algal species, Spirogyra, and can reproduce asexually, sexually, or vegetatively. In harsh conditions, Zygnema generally will produce spore-like akinetes for asexual reproduction or reproduce sexually via conjugation tubes. If reproduction is sexual, a zygospore is formed and sinks into the sediment until habitat conditions become more favorable. When algal nutrients are widely available and the environment is suitable, Zygnema frequently fragment as a means of vegetative reproduction.
  • Zygnema Filamentous Algae - DIC


    Zygnema Filamentous Algae - DIC

    Thick mats of Zygnema filaments may indicate that a body of water is enriched with nitrates and phosphates, an attribute often caused by run-off from farmlands. Water chemistry can be greatly affected by a large presence of the algae and sometimes causes serious problems for other species inhabiting the same area. The concern may be greatest during the winter months in temperate regions when algal mats die and decompose, producing a substantial biological oxygen demand caused by respiring bacteria feeding on the decaying organic material. Intense competition for limited amounts of dissolved oxygen between the bacteria and other aquatic organisms may result in a phenomenon known as winterkill, the sudden death of large populations of fish.

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