Natures wonders: insect insulation protects larvae (Introduction)

by David Turell @, Friday, June 01, 2018, 18:04 (390 days ago) @ David Turell

A sugar cane pest uses a foam system to hold temperatures constant:

"Tiny balls of froth can often be seen near the roots of plants in sugarcane plantations in Brazil during summer. The foam protects nymphs of the root spittlebug Mahanarva fimbriolata, a major pest of crops and pasture throughout the Neotropics.

"Researchers have discovered that Mahanarva fimbriolata produces the foam to protect itself from temperature fluctuations in the external environment.

"The temperature inside the ball of froth is similar to that of the soil and ideal for the insect's development, as it remains constant during the day even as the sun heats the ground.


"To determine whether the foam does, indeed, confer thermal protection during this crucial stage of the insect's development before it reaches the adult stage, the researchers conducted field experiments, monitoring temperatures inside and outside of the foam and the soil on a sugarcane plantation in the Piracicaba region of São Paulo State on a warm summer's day when temperatures fluctuated significantly.

"Their analysis showed that while external temperatures ranged from 24.4 degrees C to 29.2 degrees C, the temperature inside the foam remained constant throughout the day at approximately 25 degrees C, which is ideal for the nymph stage and similar to the typical soil temperature.

"'We confirmed that the foam provides thermal protection for the insects during this stage of their development," said Mateus Tonelli, a Ph.D. student in entomology at ESALQ-USP and another co-author of the study.


"'We observed that the foam acts as a thermoregulatory mechanism, keeping the temperature around the nymph below 32 degrees C, the temperature that is lethal for the insect. In sum, the foam is a sort of microhabitat or microenvironment in which the temperature is lower than that outside and remains constant regardless of external temperature fluctuations," Tonelli said.

"The researchers also analyzed the chemical composition of the foam to identify the compounds related to bubble production and stability.
They found significant amounts of palmitic acid and stearic acid as well as proteins and carbohydrates. These substances act as surfactants that stabilize the foam by reducing surface tension and modulating bubble size and distribution based on viscosity and elasticity. Interactions between the carbohydrates and proteins create a stable film that stiffens and stabilizes the foam around the insect.


"To produce the foam, the spittlebug nymph uses its mouth apparatus to pierce the roots of the sugarcane plant to the xylem, the tissue that transports sap, and suck out the liquid. Part of this liquid blends with other substances present in the insect's Malpighian tubules, its main excretory organ.

"The nymphs produce foam by sucking air into the ventral cavity of the abdomen. This air is mixed with the surfactant molecules and fluid in the Malpighian tubules, forming bubbles in the terminal part of the abdomen.

"'Phylogenetic studies have shown that the spittlebug evolved some 200 million years ago from the cicada, which during the nymph stage, builds an underground tunnel enabling it to live for years in favorable thermal conditions. Its body temperature remains constant without any thermal insulation mechanism. The foam produced by the spittlebug nymph may serve as a 'soil extension' for the insect," Bento said.

"'Unlike the cicada's legs, the spittlebug nymph's front legs are not strong enough to burrow into the soil in order to maintain a constant temperature. The spittlebug nymph has a delicate cuticle, and without the protection afforded by the foam, it would be vulnerable to environmental factors, such as high temperatures and low humidity.'"

Comment: If the nymphs require this protection from birth, they had to know this mechanism from the beginning of the species in evolution. Only design fits.

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