Diapause

Diapause meaning is a physiological state found mostly in arthropods. In this state, developmental arrest or dormancy is seen that signifies shutting down of most life processes. During the life cycle of an insect, the diapause can happen at any stage such as embryonic, larval, pupal, and adult. 

This developmental arrest is a spontaneous response amongst these animals to survive unfavourable environmental conditions.

However, this dormancy occurs majorly in the pupae stage of insects like cocoons of moths. Diapause during the pupil stage slows any physiological development to a halt. But, in an adult and active stage, the reproductive process or feeding habit halts or slows down.

Adverse conditions like shortage of food, changes in day length and temperature, etc. are usually the primary cause of diapause in insects. These conditions decrease the concentration of growth hormones in their body, and thus, developmental halt sets in.

So, even though diapause meaning indicates that it is a genetic phenomenon, it can be removed experimentally by providing favourable conditions to the animals. 

Organisms that Show Diapause

Several mites and insects, and a few snails and crustaceans exhibit diapauses. This developmental arrest is a spontaneous response of these animals to unfavourable environmental conditions. Some other certain groups of animals also exhibit diapauses.

A moth named Prodoxus Y-inversus can stay dormant for about 19 years. This is recorded as the longest diapause in biological science. This moth is seen in southwestern Mexico and the United States.

Diapause in the embryological stage is observed in several arthropods like southwestern corn borer, tobacco hornworm, and flesh fly.

A species of fish, mummichog also features dormancy in the embryo phase. The silkworm shows diapauses between its late larval and late embryonic stage.

Phases of Diapause in Insects

Diapause meaning is a developmental suspension in insects during any stage of their life cycle. Following stages can be found in an insect’s diapauses-

  • Induction

The induction stage happens before the beginning of unfavourable environmental cues. These specific environmental stimuli are known as “token stimuli” that starts the diapauses in insects. However, the stimuli don’t adversely impact any environmental conditions but help the animals to forecast impending environmental transformations. 

  • Preparation

As the name suggests, during the preparation stage, insects prepare their bodies for the life process suspension. This phase comes right after the induction phase. Insects start reserving metabolic sources like carbohydrates, lipids, and protein to survive during the diapauses.

  • Initiation

The initiation process is the most important phase to begin diapause. During this stage, the insects spontaneously terminate morphological development. The cessation includes releasing special enzymes, changing colour, etc.

Example: The firebugs generate some chemicals that help them to reduce the freezing point.

  • Maintenance

By reducing metabolism and suspending embryological development, the maintenance phase occurs. Moreover, certain environmental stimuli trigger the sensitivity that can prevent diapause termination.

  • Termination

The termination phase ends the developmental interruption. Nonetheless, some insects depend on certain environmental stimuli that help the termination phase to set in.

  • Post-Diapause Quiescence

After the termination of diapause, a phase of inactivity or quiescence occurs in insects. During this stage, the insects eventually start resuming their physiological development, if the environmental conditions are favourable.

Difference between Hibernation and Diapause

Hibernation implies to the seasonal inactivity that is seen in endotherms. By lowering heart-rate, metabolic rate, body temperature, etc. some animals stay inactive during the winter season. Animals like groundhogs, hedgehogs, squirrels, etc. exhibit hibernation.

Diapauses occur because of the onset of adverse environmental conditions like scarcity of food, changes in temperature, etc. Mostly arthropods show this developmental halt during any stage of their life cycle.

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FAQ (Frequently Asked Questions)

1. What is Diapause?

Ans. Diapause is a natural phenomenon that implies the suspension of physiological development and other life processes. Arthropods like insects exhibit diapauses.

2. What Triggers Diapauses?

Ans. Due to the onset of the unfavourable condition, diapause occurs. Adverse environments like a change of temperature and day length, shortage of food, etc. trigger diapauses.

3. What is the Difference between Hibernation and Diapauses?

Ans. Hibernation happens only during the winter season. However, diapause occurs due to unfavourable conditions.