The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Molting

the periodic shedding of external coverings in animals. In invertebrates, such as crustaceans, myriapods, insects, other arthropods, and some worms, molting consists in shedding the chitinous covering and replacing it with a new one. This process is necessary for the growth and development of the organism. In arthropods and other invertebrates, molting is confined to specific stages of individual development and is a complex process, involving the desquamation and partial dissolution of the old cuticle, proliferation of the cells of the epidermis, and the secretion and hardening of a new cuticle. In insects, molting is effected predominantly by the action of the molting hormone ecdysone, which acts on the chromosomal apparatus of the cells by changing the permeability of the cellular and nuclear membranes. The insect larva has glands in its head or thorax that produce and discharge a molting hormone under the influence of an activating hormone manufactured by the neurosecretory cells of the brain.

In vertebrates that is, amphibians, reptiles (except crocodiles and most turtles—which do not molt), birds, and mammals, molting is caused by the need for restoring worn-out coverings and is associated not with stages of development but with seasonal changes. In amphibians and reptiles, moltings occur one after another throughout the summer; their frequency depends on the temperature regime. At the onset of winter frosts, molting ceases. In birds and mammals each molting is confined to a specific time of the year. Its onset is associated with the change in the length of the solar day, which regulates the activity of the pituitary gland. The thyrotropic hormone produced by the pituitary gland affects the activity of the thyroid gland, whose hormone promotes molting.

As a result of molting, plumage and hairy coverings become thicker; bird plumage and the hairy covering of some mammals change in color. Molting does not always include the entire covering; there are additional moltings that involve only part of the covering. During molting the animals’ metabolism changes: protein metabolism increases and the use of oxygen increases. The rate of molting in birds and mammals can be regulated by artificially changing the light regime.

REFERENCES

Beliaev, D. K. “Rol’ sveta ν upravlenii biologicheskimi ritmami mlekopitaiushchikh.” Zhurnal obshchei biologii, 1950, vol. 11, no. 1.
Naumov, N. P. Ekologiia zhivotnykh, 2nd ed. Moscow, 1963.
Wigglesworth, V. B. Insect Hormones. Edinburgh, 1970.

E. N. POLIVANOVA

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References in periodicals archive

Molting is a critical physiological characteristic of crab.

Reconstruction and Subcellular Localization Analysis of Eriocheir sinensis Molting Protein-Protein Interaction Network

Crabs grown in an aquaculture setting readily consume each other, especially during molting, with excellent growth performance (Zmora et al.

Growth and enzyme production in blue crabs (Callinectes sapidus) fed cellulose and chitin supplemented diets

cheiragonus is linked to molting in sexually mature females, as in Callinectes sapidus, and the sex pheromones may have molting-related metabolites as a component.

The molting biomarker metabolite N-acetylglucosamino-l,5-lactone in female urine of the helmet crab Telmessus cheiragonus

The dearth of museum specimens of molting Ancient Murrelets may be attributable to the occurrence of molt offshore (Pyle 2009) where few specimens have been collected in late summer and fall.

Ancient murrelets molt flight feathers after the precocial young become independent

Five mate and 5 female African penguins (total n = 10; age range, 7-22 years) were randomly selected from the colony maintained at Mystic Aquarium to examine the hematologic and stress hormone changes associated with molting. Subsequently, a second study was conducted by using 5 penguins (2 from the previous study and 3 additional birds) outside of the molt season to assure that observed significant changes in hematologic parameters were not experimentally induced.

Molt-associated changes in hematologic and plasma biochemical values and stress hormone levels in African penguins (Spheniscus demersus)

Eiders form large, dense concentrations on their breeding, molting, and wintering areas (Lehoux and Bordage, 1999; Goudie et al., 2000), which makes them sensitive to disturbance, highly vulnerable to oil spills and overharvest, and vulnerable to disease transmission.

Molting, staging, and wintering locations of common eiders breeding in the gyrfalcon archipelago, Ungava Bay

Additional shifts in habitats for molting between years occurred for all three species: Lucy's warbler (from cottonwood and willow-riparian habitats in 2007 to grasslands in 2008), lazuli bunting (from grasslands and mesquite in 2007 to desert scrub in 2008), and lesser goldfinch (from grasslands in 2007 to desert scrub in 2008).

Habitats and conservation of molt-migrant birds in southeastern Arizona

However, feed conversion ratio was significantly improved in hens received probiotics during molting (Table 5).

Probiotics in drinking water alleviate stress of induced molting in feed-deprived laying hens

Chitobiase activity in the epidermis and hepatopancreas of the fiddler crab Uca pugilator during the molting cycle.

Moult-modulating effect of serotonin in the crab Oziotelphusa senex senex (Fabricius)

Just last week an in Rhode Island in America made headlines around the world after announcing its female lobster had turned blue after molting.

An out of the blue discovery

However, because the same type of streamer tag was used and each lobster was handled individually, the fishermen participation could not explain the difference between recapture rates for lobsters tagged in premolt and postmolt stages for a given year; hence possible tag loss at molting was suspected as the cause of the lower recapture rates (Comeau et al., 1999).

The effect of timing of tagging on streamer-tag recapture rates for American lobster (Homarus americanus)