Number of crustaceans in the world

Here is the number of crustaceans on the planet:

AnimalTypePopulationSource yearSource
CopepodsCrustacean1 x 10^182017Weborus estimation
ShellfishesCrustacean1,9 x 10^162017Weborus estimation
Sea urchinsCrustacean9 x 10^142017Weborus estimation
Antarctic krillsCrustacean5 x 10^142011NPR
CrabsCrustacean1,25 x 10^142006FAO
Spider crabsCrustacean100,000,0002017Weborus estimation
Horseshoe crabsCrustacean7,0002011Schaller and Dorsey

The crab breathes via gills. It keeps water in it when it emerges so that it can continue to breathe. The female can lay thousands of eggs (up to 3 million depending on the species) that are attached to its belly. A crab lives between 8 and 15 years depending on the conditions of its environment. There are over 4,000 crab species in the world. The crab is omnivorous, it can even eat congeners.

There is at least 1 quintillion (billion of billion) of crustaceans on Earth.