Picozoa

Picozoa

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

At first, scientists thought picozoa were a kind of algae because they were found with very small plants in the water. Later, they learned that picozoa do not make their own food 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 a group of ocean plants called Rhodophyta, or red algae. They probably belong to a larger group called Archaeplastida. They were once thought to be related to other ocean organisms called cryptomonads and haptophytes, but that is no longer believed.

Discovery

In the late 1990s, a European project called "Picodiv" looked at small organisms in ocean water. Scientists took samples from the Atlantic Ocean, the Mediterranean Sea, and places near Scotland, Alaska, and Norway. They found Picobiliphyta in cold, nutrient-poor coastal waters, where these tiny organisms can make up 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 saw that they did not match any known group of living things. These tiny organisms were found in water 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. Instead, they get their food by eating other small organisms or particles in the water. This helped scientists classify them as a special group of organisms.