Molting vs Metamorphosis
摩擦和变形是动物生命周期中两种重要事件,它们之间表现出一定的差异。摩擦和变形在insects. These two phenomena are controlled by the two classes ofhormones; ecdysteroids and juvenile hormones (JHs). Molting is not found invertebrates. However, some vertebrates likeamphibiansshow metamorphosis during their life cycle. In this article, difference between molting and metamorphosis will be explained via discussing individual events.
What is Molting?
All the insects have a hardenedexoskeletonmade up of chitin. This exoskeleton protects the inside organs and also prevents water loss. At the same time, it restricts the growth of insects. To avoid this problem, insects have to shed their exoskeleton several times during their life time. However, before they shed the exoskeleton, they always have a new developing exoskeleton underneath the old one. The entire process starting from the development of new exoskeleton to casting off the old exoskeleton is called molting. In addition, casting off the old exoskeleton is known asecdysis. The stages between the periods of molting are called龄.
Molting cycle consists of sequence of events that ultimately build a new, larger exoskeleton within the old one. These events are triggered by the hormone calledecdysone, which is secreted by a pair of glands in the thorax of insects. While secreting ecdysone, another pair of glands near the brain secretes juvenile hormone, which inhibits the metamorphosis. Hence, it causes an insect to remainlarvastage after ecdysis rather than transforming into pupil stage.
What is Metamorphosis?
Metamorphosis is the process of whicharthropods未成熟阶段和成人在成长过程中发生变化。在许多节肢动物中,这些变化很小,包括大小,颜色或图案的变化。但是,在昆虫从幼虫到成人的生长过程中,大多数可区分的变化都可以看到。变形主要由内分泌系统of arthropods. Metamorphosis is suppressed by juvenile hormone, which secretes during the molting. However, when decreasing the hormone concentration of blood, it increases the possibility of metamorphosis. There are two types of metamorphosis; complete and incomplete metamorphosis. Insects withcomplete metamorphosishave four stages in their life cycle, namely; egg, larva,pupa, and adult. Each of this stage is very distinguishable. This can be seen in insects likemoths and butterflies.Incomplete metamorphosishas three life stages; egg, nymph and adult. Nymph stage is more similar to adult form with the exception of color, size, and the lack of wings. Examples for insects with incomplete metamorphosis include mites, aphids,bugs,cockroachesetc.
What is the difference between Molting and Metamorphosis?
• Molting is the process of developing a new exoskeleton and casting off the old exoskeleton. Metamorphosis is the change in form between immature stages to adult stage.
• Molting does not involve the changes in life cycle stages, but metamorphosis does.
• Juvenile hormone triggers the molting whereas it suppresses the metamorphosis.
Image Courtesy:
- Cicada molting通过Wikicommons(公共领域)
- Complete metamorphosisbyBugboy52.40(CC BY-SA 3.0)
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