Picozoa

Picozoa, also known as Picobiliphyta, picobiliphytes, or piliphytes, are tiny organisms that live in the ocean. They are a type of protist, which means they are simple, single-celled creatures. These organisms are very small, smaller than about 3 micrometers, which is about 30 times smaller than a single hair.

At first, scientists thought picozoa were a kind of algae because they were found among very small plants in the water. But later, they learned that picozoa do not make their own food through photosynthesis like plants and algae do. Instead, they get their food by eating other tiny organisms, which makes them heterotrophic.

Right now, scientists know of only one species of picozoa, called Picomonas judraskeda. These organisms are thought to be closely related to another group of ocean plants called Rhodophyta, or red algae, and they probably belong to a larger group called Archaeplastida. They were once thought to be related to another group of ocean organisms called cryptomonads and haptophytes, but that is no longer believed.

Discovery

In the late 1990s, a European project called "Picodiv" studied small organisms found in ocean water. Researchers collected samples from the Atlantic Ocean, the Mediterranean Sea, and areas near Scotland, Alaska, and Norway. They discovered Picobiliphyta in nutrient-poor, cold coastal waters, where these tiny organisms can make up to half of the living material in the water.

Affinities to other organisms

Picozoa were first found in 2007 by looking at special genes called 18S ribosomal RNA. Scientists Klaus Valentin and Linda Medlin studied these genes and realized they did not match any known group of living things. These tiny organisms were found in water samples from the North Atlantic and the Mediterranean Sea, showing that they are common in many places.

Later studies in 2011 showed that picozoa do not use sunlight to make food like plants do. Instead, they get their food by eating other small organisms or particles in the water. This made scientists classify them as a unique group of organisms that feed differently from plants or algae.