Muscles contract and relax to allow for locomotion, and they accomplish this with structures called sacromeres. In this fruit fly larva, sacromeres appear as the thin, striped bands within the red muscle tissue along the body wall. Flying insects have sacromeres that are not built for maximum energy output; rather, they are long with a limited range of motion in order to assist in wing movement during flight.
Image by Timothy Mosca, Stanford University.
Nearly 85% of cancers derive from epithelial cells that line almost every organ in the human body. When cancers become aggressive, they can lose their epithelial characteristics and become more motile. Motile cancerous cells can result in cancer metastasis. To understand the process by which epithelial cells become more motile, the fruit fly egg chamber is an excellent model system as groups of epithelial cells detach and migrate during egg development. Seen here are several egg chambers from Drosophila melanogaster.
Image by Denise Montell.
The stinging nettle has hollow stinging hairs called trichomes that, when broken, inject chemicals like histamine under the skin. Ironically, nettle leaf extract also has compounds that reduce TNF-α, an inflammation-promoting molecule.
Image by Marek Mis.
Just as gills allow crustaceans to breathe underwater, tracheae (yellow, with cell nuclei in blue) allow insects to breath on land. Crustacean gills and insect tracheae share many similarities, indicating an evolutionary relationship exists between them. It will take the discovery of new fossils that capture insects’ water-to-land transition to understand this relationship in better detail.
Image by Dr. Robert Markus, Stockholm University.
Sensory neurons convey signals from the outside world to our brain for interpretation. As they mature, sensory neurons grow radially outward, expanding their volume over 1,000 times that of other animal cells. This growth in size is important, because the conduction speed of signals increases as the diameter of a neuron increases. In these sensory neurons, axons (which transmit signals) are stained in green while the cell body is stained red.
Image by Dr. María Alejandra Lopez-Verrilli, Pontificia Universidad Católica de Chile.
Mushrooms have evolved gills, called lamella, that grow underneath the main cap of some species. Lamella function to dramatically increase the surface area of a mushroom, increasing the amount of spores produced and dispersed during reproduction.
Image by Charles Krebs.
Butterfly wing scales at 75-times magnification. Butterfly scales most likely evolved in order to provide insulation, as high body temperatures are required for efficient flight. Scales that are pigmented with bright colors warn predators of a butterfly’s potential toxicity or inedibility. Other inert butterfly species mimic this bright coloration scheme to fool predators into thinking they too are poisonous, thus sparing the butterfly’s life.
Image by Oleg Kolesnikov, Russian State Agrarian University.
Astrocytes (in red) are the most abundant cell in the brain and help support neurons (in green) by recycling old cellular byproducts and regulating a healthy environment for neuronal function. Unlike other organs of the body where an injury results in a fibrous scar, the brain instead forms an astrocyte scar to promote neuron survival.
Image by Dr. Shelley Jacobs, McMaster University.
The green algae Acetabularia is a remarkable tool for studying cell biology because, although complex in shape and giant in size, it is a single-celled organism. Acetabularia were used in an experiment by Joachim Hämmerling to show that the nucleus determines a cell’s development and characteristics.
Image by Dr. John Huisman, Western Australian Herbarium.
Epithelial cells line surfaces and cavities throughout the body, forming skin, glands, and tracts. This mouse embryo has been genetically engineered to allow for the visualization of epithelial cells, showing the pattern of whisker placement on the face.
Image by Evan Heller, Rockefeller University.
