The Water Content of Spiders Compared to Mammals and Vertebrates

Which animal has the smallest percentage of their body mass made up of water?

One group of animals that has a relatively low percentage of their body mass made up of water is the arachnids, specifically spiders. Unlike most other animals, spiders have an exoskeleton, a hard external skeleton made of chitin and proteins. This exoskeleton helps spiders retain moisture and prevents water loss. Additionally, spiders have a specialized respiratory system that limits water loss through evaporation.

Compared to mammals and other vertebrates, spiders have a much higher proportion of dry tissue, such as muscles and organs, in their bodies. This leads to a lower percentage of water content. While there is no specific percentage that applies to all spider species, their water content is estimated to be around 70-75% on average. In comparison, mammals typically have water content ranging from 75% to 90% of their body mass.

It’s important to note that even though spiders have a lower percentage of water in their bodies, they still require water to survive. They obtain water from various sources like prey fluids, dew, and drinking water droplets. Their unique adaptations allow them to thrive in drier conditions compared to many other animals.

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