Social System Protects From Disease

a colony of white termites climb among soil and wood

Biological Strategy

Pacific dampwood termite

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Image: TJ Gehling / Flickr / Some rights reserved

Protect From Fungi

Fungi–which include molds and mushrooms, amongst others–play important roles in every ecosystem, but can also create diseases in plants and animals. Fungi can rapidly reproduce, so living systems must fend them off early to avoid their spread and potential, physical harm. Living systems use both physical and chemical strategies to protect from fungi, and must ensure that these strategies don’t harm the threatened living system itself. For example, a pumpkin’s skin has antifungal proteins to prevent fungal growth without harming the pumpkin itself.

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Protect From Microbes

In living systems, microbes play important roles, such as breaking down organic matter and maintaining personal and system health. But they also pose threats. Bacteria can be pathogens that cause diseases. Some bacteria create colonies called biofilms that can coat surfaces, reducing their effectiveness–for example, inhibiting a leaf’s ability to photosynthesize. Living systems must have strategies for protecting from microbes that cause disease or become so numerous that they create an imbalance in the system. At the same time, living systems must continue living in harmony with other microbes. Some living systems kill microbes. Others repel without killing to reduce the chances that microbes will adapt to the lethal strategy and become resistant to it. For example, some pea seedlings exude a chemical that inhibits biofilm buildup.

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Insects

Class Insecta (“an insect”): Flies, ants, beetles, cockroaches, fleas, dragonflies

Insects are the most abundant arthropods—they make up 90% of the animals in the phylum. They’re found everywhere on earth except the deep ocean, and scientists estimate there are millions of insects not yet described. Most live on land, but many live in freshwater or saltwater marshes for part of their life cycles. Insects have three distinct body sections: a head, which has specialized mouthparts, a thorax, which has jointed legs, and an abdomen. They have well-developed nervous and sensory systems, and are the only invertebrate that can fly, thanks to their lightweight exoskeletons and small size.

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Members of termite colonies transfer immunity among colony members via a sort of social vaccination.

“Termites have devised an ingenious public health programme. By vaccinating their nest mates against infection, they prevent potentially devastating diseases destroying the colony, entomologists have discovered. This group immunity could be one reason why social insects are so successful…Now James Traniello and his team at Boston University in Massachusetts have found that living in a group boosts an individual termite’s immunity to disease. He had shown previously that termites that survive an infection are better able to fight off the same disease in future, suggesting that their immune system develops a ‘memory’ for the parasite, just as ours does. Traniello now wanted to find out whether this memory could be transferred between nest mates.

“The researchers exposed dampwood termites (Zootermopsis angusticollis) to a fungal infection to immunise them. Next, they placed the immunised insects with termites that had never encountered the fungus. When they infected different groups of termites with the fungus, they found that unimmunised termites did better in these mixed groups than in a group on their own. The immunised insects are carrying out a sort of ‘social vaccination’, says Traniello.

“As yet, the team doesn’t know how immunity is transferred. But Traniello has a few ideas. Termites regularly transfer gut bacteria to each other, which allows them to break down in wood. So they may be sharing fungicides produced by bacteria in their guts in the same way. Alternatively, the immunised termites might transfer inactivated fungal spores to their nest mates, which allows them to experience the pathogen safely.” (Randerson 2002:6)

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