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Cosmine was first described in the Osteolepiform Megalichthys hibberti by Williamson in 1849, in a purely descriptive, pre-Darwinian, non-evolutionary framework. [4] Goodrich [5] expanded on Williamson's descriptions, hypothesizing a transition from a monoodontode scale (like a chondryicthian placoid scale) to a complex polyodontode scale through fusion of discrete units.
Reptile scale types include: cycloid, granular (which appear bumpy), and keeled (which have a center ridge). Scales usually vary in size, the stouter, larger scales cover parts that are often exposed to physical stress (usually the feet, tail and head), while scales are small around the joints for flexibility.
Ichthyosis (also named fish scale disease) [1] is a family of genetic skin disorders characterized by dry, thickened, scaly skin. [2] The more than 20 types of ichthyosis range in severity of symptoms, outward appearance, underlying genetic cause and mode of inheritance (e.g., dominant, recessive, autosomal or X-linked). [3]
Dorsal view of right-bending (left) and left-bending (right) jaw morphs adapted for eating fish scales [68] Lepidophagy (Ancient Greek for scale-eating) is a specialised feeding behaviour in fish that involves eating the scales of other fish. [69] Lepidophagy has independently evolved in at least five freshwater families and seven marine ...
Prokaryotes (bacteria and archaea) usually undergo a vegetative cell division known as binary fission, where their genetic material is segregated equally into two daughter cells, but there are alternative manners of division, such as budding, that have been observed. All cell divisions, regardless of organism, are preceded by a single round of ...
The mineral texture of alligator gar scales consists of bundles of cross-plied hydroxyapatite minerals oriented towards the scale's surface. Ganoine or ganoin is a glassy, often multi-layered mineralized tissue that covers the scales , cranial bones and fin rays in some non-teleost ray-finned fishes , [ 1 ] such as gars and bichirs , as well as ...
One of two things can occur to produce offspring with exclusively paternal genetic material: the maternal nuclear genome can be eliminated from the zygote, or the female can produce an egg with no nucleus, resulting in an embryo developing with only the genome of the male gamete.
Ciliate conjugation is a sexual phenomenon that results in genetic recombination and nuclear reorganization within the cell. [24] [22] During conjugation, two ciliates of a compatible mating type form a bridge between their cytoplasms. The micronuclei undergo meiosis, the macronuclei disappear, and haploid micronuclei are exchanged over the bridge.