Hamsters are rodents belonging to the subfamily Cricetinae, which contains 19 species classified in seven genera. They have become established as popular small pets. The best-known species of hamster is the golden or Syrian hamster, which is the type most commonly kept as a pet. Other hamster species commonly kept as pets are the three species of dwarf hamster, Campbell's dwarf hamster, the winter white dwarf hamster and the Roborovski hamster.
Color vision, a feature of visual perception, is an ability to perceive differences between light composed of different frequencies independently of light intensity.
A photoreceptor cell is a specialized type of neuroepithelial cell found in the retina that is capable of visual phototransduction. The great biological importance of photoreceptors is that they convert light into signals that can stimulate biological processes. To be more specific, photoreceptor proteins in the cell absorb photons, triggering a change in the cell's membrane potential.
The golden hamster or Syrian hamster is a rodent belonging to the hamster subfamily, Cricetinae. Their natural geographical range is in an arid region of northern Syria and southern Turkey. Their numbers have been declining in the wild due to a loss of habitat from agriculture and deliberate elimination by humans. Thus, wild golden hamsters are now considered endangered by the International Union for Conservation of Nature. However, captive breeding programs are well established, and captive-bred golden hamsters are often kept as small house pets. They are also used as scientific research animals.
Tetrachromacy is the condition of possessing four independent channels for conveying color information, or possessing four types of cone cell in the eye. Organisms with tetrachromacy are called tetrachromats.
Trichromacy or trichromatism is the possession of three independent channels for conveying color information, derived from the three different types of cone cells in the eye. Organisms with trichromacy are called trichromats.
In visual physiology, adaptation is the ability of the retina of the eye to adjust to various levels of light. Natural night vision, or scotopic vision, is the ability to see under low-light conditions. In humans, rod cells are exclusively responsible for night vision as cone cells are only able to function at higher illumination levels. Night vision is of lower quality than day vision because it is limited in resolution and colors cannot be discerned; only shades of gray are seen. In order for humans to transition from day to night vision they must undergo a dark adaptation period of up to two hours in which each eye adjusts from a high to a low luminescence "setting", increasing sensitivity hugely, by many orders of magnitude. This adaptation period is different between rod and cone cells and results from the regeneration of photopigments to increase retinal sensitivity. Light adaptation, in contrast, works very quickly, within seconds.
Melanopsin is a type of photopigment belonging to a larger family of light-sensitive retinal proteins called opsins and encoded by the gene Opn4. In the mammalian retina, there are two additional categories of opsins, both involved in the formation of visual images: rhodopsin and photopsin in the rod and cone photoreceptor cells, respectively.
Intrinsically photosensitive retinal ganglion cells (ipRGCs), also called photosensitive retinal ganglion cells (pRGC), or melanopsin-containing retinal ganglion cells (mRGCs), are a type of neuron in the retina of the mammalian eye. The presence of an additional photoreceptor was first suspected in 1927 when mice lacking rods and cones still responded to changing light levels through pupil constriction; this suggested that rods and cones are not the only light-sensitive tissue. However, it was unclear whether this light sensitivity arose from an additional retinal photoreceptor or elsewhere in the body. Recent research has shown that these retinal ganglion cells, unlike other retinal ganglion cells, are intrinsically photosensitive due to the presence of melanopsin, a light-sensitive protein. Therefore, they constitute a third class of photoreceptors, in addition to rod and cone cells.
A hamster wheel or running wheel is an exercise device used primarily by hamsters and other rodents, but also by other cursorial animals when given the opportunity. Most of these devices consist of a runged or ridged wheel held on a stand by a single or pair of stub axles. Hamster wheels allow rodents to run even when their space is confined. The earliest dated use of the term "hamster wheel", located by the Oxford English Dictionary, is in a 1949 newspaper advertisement. Squirrel cages featured in an 1885 catalog titled Catalogue of the Osborn M’F’G Co. came with running wheels for the squirrels, just like a hamster cage.
Glaphyridae is a family of beetles, commonly known as bumble bee scarab beetles. There are eight extant genera with about 80 species distributed worldwide and two extinct genera described from the Aptian aged Yixian Formation of China. There are cases of flower-beetle interactions, in the southeast Mediterranean region between red bowl-shaped flowers and Glaphyridae beetles.
The desert long-eared bat is a species of vesper bat found in North Africa and the Middle East.
The evolution of color vision in primates is highly unusual compared to most eutherian mammals. A remote vertebrate ancestor of primates possessed tetrachromacy, but nocturnal, warm-blooded, mammalian ancestors lost two of four cones in the retina at the time of dinosaurs. Most teleost fish, reptiles and birds are therefore tetrachromatic while most mammals are strictly dichromats, the exceptions being some primates and marsupials, who are trichromats, and many marine mammals, who are monochromats.
Color vision, a proximate adaptation of the vision sensory modality, allows for the discrimination of light based on its wavelength components.
Vision is the most important sense for birds, since good eyesight is essential for safe flight. Birds have a number of adaptations which give visual acuity superior to that of other vertebrate groups; a pigeon has been described as "two eyes with wings". Birds are theropods, and the avian eye resembles that of other sauropsids, with ciliary muscles that can change the shape of the lens rapidly and to a greater extent than in the mammals. Birds have the largest eyes relative to their size in the animal kingdom, and movement is consequently limited within the eye's bony socket. In addition to the two eyelids usually found in vertebrates, bird's eyes are protected by a third transparent movable membrane. The eye's internal anatomy is similar to that of other vertebrates, but has a structure, the pecten oculi, unique to birds.
Double cones (DCs), known as twin cones when the two members are the same, are two cone cells joined together that may also be coupled optically/electrically. They are the most common type of cone cells in fish, reptiles, birds, and monotremes such as the platypus and are present in most vertebrates, though they have been noted as absent in most placental mammals, elasmobranches and catfish. There are many gap junctions between the cells of fish double cones. Their function, if they have any unique function compared to single cones, is largely unknown; proposed uses include achromatic tasks such as detecting luminance, motion and polarization vision.
Syrian hamster behavior refers to the ethology of the Syrian hamster.
Syrian hamsters are one of several rodents used in animal testing. Syrian hamsters are used to model human medical conditions including various cancers, metabolic diseases, non-cancer respiratory diseases, cardiovascular diseases, infectious diseases, and general health concerns. In 2014, Syrian hamsters accounted for 14.6% of the total animal research participants in the United States covered by the Animal Welfare Act.
Nicholas Mrosovsky was a Canadian zoologist known for his research in the fields of homeostasis, chronobiology, and sea turtle biology. He spent his whole professional career at the University of Toronto. His laboratory was notable for its seminal investigations of the influence of behavioural arousal on circadian rhythms. He was also the founder, in 1976, of Marine Turtle Newsletter. He received a Guggenheim Fellowship in 1973, and in 1993 he was elected a Fellow of the Royal Society of Canada.
