Kamptozoa and Bryozoa are two phyla of small aquatic invertebrates. They are related to snails and clams (collectively known as mollusks), earthworms, earthworms and leeches (collectively known as annelids), and banded worms (nemertea). But their exact location on the tree of life, and their close relationship with other animals, has puzzled evolutionary biologists. Previous research has been changing them. What’s more, although camptozoans and bryozoans were originally considered a group, they were separated based on their appearance and anatomy. Now, by using cutting-edge sequencing techniques and powerful computational analysis, scientists at the Okinawa Institute of Science and Technology Graduate School (OIST), in collaboration with colleagues at St. Petersburg University and the University of Tsukuba, have revealed that the two phyla, molluscs and worms, predate previous studies showed that they did indeed form a distinct group.
“We have shown that by using high-quality transcriptome data, we can use our existing technology to answer a long-standing question,” said a staff scientist in OIST’s Marine Genomics Division, published in scientific progress.
The genome is the complete set of genetic information found in every cell. It is subdivided into genes. These genes are made up of DNA base pairs, and each gene contains the instructions needed to produce proteins, leading to the proper care and maintenance of cells. In order to execute instructions, DNA must first be transcribed into RNA. The transcriptome is the result, like a reflection of the genome, but written in RNA base pairs instead of DNA.
This genetic information varies from species to species. People who are closely related have very similar genetic information, and the greater the evolutionary distance, the greater the genetic difference. Using these data, researchers have improved our understanding of animal evolution, but some questions remain difficult to answer.
Since Kamptozoa and Bryozoa are closely related to mollusks, annelids, and nematodes, small errors or missing data in the dataset may result in incorrect placement on the evolutionary tree. Additionally, other organisms, such as algae, that contaminate the samples are easy to spot when collecting these small animals. Dr. Khalturin emphasized that they were careful to avoid contamination and later screened their dataset for RNA from algae and small animals to remove any RNA that might have come from them.
Overall, the researchers sequenced the transcriptomes of four Kamptozoa and two Bryozoa, but at a level of quality that was much higher than before. While the completeness of past datasets was 20-60%, in this study, the completeness of the transcriptome was over 96%.
Using these transcriptomes, they predicted proteins and compared them with similar data from 31 other species, some closely related to Kamptozoa and Bryozoa, such as clams and caterpillars, and some more distant, such as frogs, starfish , insects, and jellyfish. High-quality datasets mean they can compare many different genes and proteins simultaneously. Dr. Khalturin praised researchers’ access to the computing power at OIST.
“Our main finding is that the two phyla belong to the same class,” Dr. Khalturin said. “This result was first proposed in the 19th century by biologists who grouped animals according to their appearance.”
While Dr Khalturin said this question is now best answered, he also stressed that the dataset could answer other fundamental evolutionary questions – such as where mollusks and annelids are more precise on the tree of life, and how they lived Diversification.