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New research reveals the eating habits of isopods that influence the ecosystem

Vaseline

Woodlice (Hemilepistus reaumuri) are strange little creatures that look like lice or cockroaches – and are not insects at all, but crustaceans. Common names for them include woodlice, roly-poly, pill bug, sea roach and pill bug, but there are more than 10,000 identified species of woodlice around the world, half of which live on land, and 4,500 species that live in seabeds and other species occur. marine environments, and the remainder in freshwater.

They derived the name isopod from ‘iso’ meaning ‘equal’ and ‘pod’ meaning ‘foot’. What they have in common are segmented external skeletons, seven pairs of jointed limbs on the chest, two pairs of antennae, and five pairs of branching appendages on the abdomen used for breathing.

Now a new study has been conducted led by Prof. Dror Hawlena of the Hebrew University and led by Dr. Moshe Zaguri (then a doctoral student and now at the Volcani Institute in Rishon Lezion) in collaboration with Prof. David Raubenheimer of the University of Sydney.

The research sheds light on the complex nutritional and functional dynamics that shape the nutritional choices of desert woodlice. It has just been published in the magazine Ecology Letters titled “Food You Will Eat: Complex Considerations Underlying a Simple Diet.” The study presents the multifaceted considerations that influence the food selection of these fascinating creatures.

Contrary to expectations, wild woodlice showed a preference for macronutrient-poor organic soil crust (BSC) over plant litter, consuming three times more of the former.

These revolutionary findings could shed new light on how different animals and humans choose their diets by taking into account both the nutrients in the food and the existence of digestive support agents.

Dietary choices in desert woodlice

Isopod siblings start the day by cleaning the den before foraging. Uploaded on 5-8-2024 (credit: Moshe Zaguri)

Foods are complex mixtures of chemical compounds presented at varying levels of digestibility that humans and animals ingest to support nutrition. Often animals must consume different types of food to meet their multidimensional nutritional needs and can suffer damage to their health if they do not eat the necessary nutrients in specific amounts and proportions.

Understanding which factors influence food choices is thus a very important but extremely challenging question to study. The authors focused on the simple but mysterious diet of the desert isopods that eat dry leaves and a large amount of nutrient-poor biological soil crust (the upper burrow of desert soils that harbor many microorganisms).

They fed woodlice with natural and artificial food and discovered that, given a choice, woodlice can strictly regulate their food consumption to meet a very specific ratio of proteins, sugars and calcium. Woodlice got most of their proteins and sugars from dry leaves and eat soil crust to meet their very high calcium needs.

The exoskeleton of woodlice is made of calcium carbonates that they must consume in large quantities to grow; when they were able to supplement leaf litter with artificial calcium sources, they successfully met their exact calcium needs but suffered from reduced growth.

The scientists used gamma radiation to kill the microorganisms in the soil crust while maintaining nutritional value and measured the woodlice’s food assimilation efficiency and growth rate compared to woodlice that ate untreated crust. They discovered that the crustaceans eat the rind to absorb living microorganisms into their digestive systems. These microbes helped improve the digestion of the fibrous plant waste.

The team concluded that woodlice eat food that helps them meet their nutritional needs by providing the nutrients, but also by helping them digest them. People don’t eat bottom crust, but they can think about the general insights of this interesting study on their next visit to the local grocery store.

The study found that desert isopods rigorously regulate their macronutrient and calcium intake, leaving phosphorus intake unaffected. Furthermore, the team noted that, despite equivalent calcium intake, woodlice thrived better when consuming BSC compared to artificial food.

Notably, woodlice consuming gamma-irradiation sterilized BSC showed higher consumption but slower growth rates compared to those consuming live BSC, suggesting the critical role of ingested microorganisms in facilitating litter digestion.

Zaguri noted that “our findings underscore the complexity of dietary decision-making among desert isopods and highlight the importance of considering multifaceted factors when understanding trophic (food chain) interactions.”



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