An enlarged image of a slime creature (in its spore-dispersing stage), which can parasitize salmon and trout. Image Source: CABI Digital Library website.
Most animal enthusiasts are familiar with blue whales, known as the largest animals on Earth, but what about the smallest? According to scientists including Professor Bayes Occamra from the Natural History Museum in London, the title for the smallest animal known to date goes to the slime creature, as many adult slime creatures consist of just a single cell.
Slime creatures, tiny invertebrates related to jellyfish, can have a diameter as small as 0.02 millimeters. Data provided by scientists from the University of Hawaii indicates that their "bulk" is only 1/100th the size of a grain of sand.
Evolved into a simplistic form, slime creatures are adept at inhabiting other life forms. Most produce spores capable of dispersal in water. Cells from these spores invade vertebrate hosts (such as fish) and invertebrate hosts (such as segmented worms), developing within them. For instance, some slime creatures infect the gallbladders of Amazonian fish, growing into worm-like organisms resembling multicellular roundworms but possessing single-cell bodies.
While some slime creatures can cause illness in hosts, many are harmless. Their harmless nature, combined with their minuscule size, often leads scientists to overlook them, yet thousands of species of slime creatures inhabit various parts of the globe.
Other animals are also renowned for their "diminutive stature." A study published in the journal "Mammal Review" in 2012 identified the Etruscan shrew and the bumblebee bat as sharing the title for the smallest mammals. The bumblebee bat measures 2.9–3.3 centimeters in length, while the shrew measures 5 centimeters.
The smallest vertebrate is a tiny frog. In a study published in the journal "Zootaxa" in February of this year, the Paedophryne amauensis was identified as the smallest known vertebrate. Mature individuals of this frog species have an average length of only 8.2 millimeters, with males measuring as little as 7.1 millimeters, small enough to perch on a human fingernail.
