Scientists have resurrected the "forgotten" algae living in marine animals

University of Pennsylvania Park

In a paper published in the journal Nature in 1882, Sir Patrick Geddes, a biologist at the University of Edinburgh, proposed that these cells are not only different entities, but also beneficial to the animals they live in.

Now, more than a century after Geddes's paper was published, an international research team re-examined these "yellow cells".

In a study published in the European Journal of Physiology on June 28, the team used modern technology to thoroughly identify the two algae studied by Geddes and six new related algae.

"Patrick Geddes recognized that the'yellow cells' found in some animals are actually different entities-microalgae symbionts-that exist in animal tissues and created a photosynthetic animal He was the leader in his time

LaJeunesse and his colleagues used genetic information; external physical or morphological characteristics; ecological characteristics; and geographic distribution to define the diversity found within the newly discovered genus Philozoon

LaJeunesse said: "Because our team is composed of scientists from 7 countries, we were able to collect all these samples, some samples were collected during the global pandemic

LaJeunesse said: "From the Mediterranean to New Zealand to Chile, the fact that these algae exist in animals reminds us how widespread these symbiotic organisms are on earth

The research team recorded that at their northernmost and southernmost latitudes, the water temperature of Clostridium feilotus may reach a low temperature of nearly 40 degrees Fahrenheit in winter and a high temperature of nearly 90 degrees Fahrenheit in summer

LaJeunesse said: "These Philozoons can withstand a wide range of temperatures, probably due to their diversification in the colder late Pliocene and the most recent Pleistocene

He added that careful identification and classification of these symbiotic algae is crucial to understanding the biology and evolution of marine animals that depend on these organisms for survival

Pilar Casado-Amezúa, a researcher at the HyT Association in Spain, said: "The advanced molecular genetics technology we use today has greatly improved our ability to study and understand these microorganisms

LaJeunesse noticed that although some other scientists were also studying these "yellow cells" at the end of the 19th century, Geddes clearly recognized the full importance of his previous evidence

He explained, "In describing the association between cells and host animals, Godes called it "animal lichens" and eloquently wrote, "Such associations are more complicated than fungal and algal lichens, and are indeed unique.
The highest development of physiology is not parasitism, but the interaction between the animal kingdom and the plant kingdom.
Geddes strongly advocates that these algae are symbiotic in nature
.
Now, more than a century after they were discovered, the true identity of these algae has finally been correctly described
.
"

###