The Mystery of Lamprey Species

Freshwater fish are found in many places like lakes, rivers, and streams. These fish often travel between different homes, such as going from rivers to lakes. Some even make journeys to salty seas! These special travelers are called diadromous fishes. Among them, many fish, especially in lakes that formed after glaciers retreated, show a variety of shapes and sizes. Some people even think that different shapes can mean different Species.

#The Challenge of Identifying Species

Identifying what makes a fish a different species can be tough. This is especially true for certain groups, like the Salmoniformes, which include trout, charr, and whitefish. The confusion doesn't just stop at freshwater fish though. There are many tricky examples in purely salty waters where similar species live too.

One tricky family of fish is the lamprey. Lampreys can be non-parasitic freshwater fish or larger, migratory ones that suck the life out of other fish. For instance, the European river lamprey is a migratory fish, while the brook lamprey stays in freshwater and doesn’t feed once it matures. These two are closely related but have very different lifestyles.

Despite many studies examining their DNA, scientists cannot say for sure if these lampreys are separate species or just two types of the same fish. The larval stages of the river and brook lamprey look similar, as both feed by filtering food from the bottom of streams for several years. But when they reach adulthood, things change! The brook lamprey develops eyes and a sucker mouth, stops eating, and completes its life cycle in the same freshwater it grew up in. Meanwhile, the river lamprey migrates to lakes or the sea, feeding off larger fish before returning to rivers to mate and die.

A burning question remains: Are the differences in their looks and lifestyles a result of their genetics, or can they change based on their surroundings?

#DNA Studies and Speciation

Scientists have conducted various DNA studies on these lampreys, but none have found clear differences that would suggest they are different species. Some researchers think that the river and brook lampreys may be at different stages of becoming separate species, depending on where they live. They believe that more detailed studies using whole genome sequencing are needed to observe not only small changes in DNA but also bigger structural changes, like rearrangements of chromosomes.

To do this, it’s essential to have high-quality reference Genomes for both lamprey types. Recent scientific work has provided two detailed chromosome-level genomes for the river lamprey (Lampetra fluviatilis) and the brook lamprey (Lampetra planeri). Using advanced sequencing technology, researchers have created detailed maps of their DNA.

#Collecting Samples

To get the DNA they needed, scientists collected lamprey specimens from different places in Scandinavia. They caught the river lamprey in Norway and the brook lamprey in Sweden. After carefully processing these fish, the researchers sent the samples to a sequencing center for analysis.

#Preparing for Sequencing

In the lab, DNA was extracted from the blood and tissues of the lampreys. The scientists followed strict protocols to ensure high-quality DNA. This involved several steps, including cleaning the DNA and checking its quality to ensure accuracy in the sequencing process.

Once the DNA was ready, the researchers sequenced it using advanced technology. They prepared samples and sequenced them using special libraries that help record the DNA sequences accurately. The scientists also used another method to capture the three-dimensional structure of the lamprey’s DNA, which helps them understand how the DNA is organized.

#Assembling the Genomes

After sequencing, the researchers needed to assemble the lamprey genomes. They used various software tools to put together the pieces of DNA based on the sequences they obtained. The result was two separate assemblies for each lamprey type.

The total lengths of the completed genomes were impressive, with the river lamprey assembly being larger than its brook counterpart. The quality of the assemblies was also checked for completeness and potential errors. This is crucial, as a high-quality genome can reveal much about the genetics and biology of an organism.

#Genome Assembly Metrics

The scientists gathered various metrics to assess the quality of their assembled genomes. They found their assemblies to be quite complete, with a high percentage of known genes present. This strong performance means they can trust their findings when comparing the two lamprey species.

#Comparing the Genomes

With the genomes assembled, researchers began to compare the river and brook lamprey genomes. They looked for similarities and differences in their DNA sequences. Surprisingly, they found that the two lamprey types shared many similarities, which led to questions about whether they were indeed different species.

The scientists also compared their findings with another lamprey species, the sea lamprey. Differences in gene order and chromosomal layout were noted, pointing to evolutionary changes that have happened over time.

#The Synteny Puzzle

One interesting aspect of their research was studying synteny, or the conservation of gene order across related species. When comparing the lampreys, researchers noted that there were many conserved gene patterns, suggesting that the lampreys share a common ancestry. They also observed some differences, particularly when looking at the sea lamprey.

The researchers discovered that significant rearrangements of genes had occurred over time, with some chromosomes showing more changes than others. This opens up a larger discussion about how lampreys evolved and adapted to their environments.

#What Does This Mean for Species Classification?

The findings raise important questions about how we classify species. If the river and brook lampreys are indeed very similar, we might be looking at a complex of species rather than two separate entities. The researchers suggest that future studies should look at individuals from various locations across Europe and include fish during different life stages to create a clearer picture of their relationship.

#Conclusion

The study of freshwater lampreys proves to be a captivating exploration of genetics, evolution, and the intricacies of nature. While researchers have uncovered exciting bits of information, many questions remain unanswered. The world of fish is diverse and complex, and as scientists continue their work, we might just learn more about how these creatures fit into the wider tapestry of life. Who knows, maybe one day, we will have a lamprey encyclopedia!

Through the careful examination of DNA, researchers are piecing together the stories of these remarkable fish. With humor, patience, and a pinch of curiosity, they continue to unravel the mysteries swimming just beneath the surface.