Discovered 7 new leech species living in freshwater mussels

Research published November 11 shows that the link between leeches and freshwater mussels has developed over millions of years.

The location and shape of the eyes are the characteristics that help identify new leeches. Photo: UPI.

A team of molluscs, led by expert Arthur Bogan from the North Carolina Museum of Natural Science, has spent the past 16 years traveling to many parts of the world, such as East Asia, South Asia, and Southeast Asia. , Africa and North America to collect more than 3,000 freshwater mussels to discover what exists inside this bivalve creature. The project not only revealed 7 new leech species but also changed our understanding of the symbiotic relationship between the two species.

Previously, the presence of leeches inside freshwater mussels had been recorded since the mid-19th century but were only considered an accidental phenomenon. New research shows that at least two of the seven leech species are found to be obligated parasite living in freshwater mussels, meaning they cannot complete the life cycle without a host.

According to Ivan N. Bolotov, a member of the research team, this parasitic lifestyle has been an evolutionary trait over millions of years. Natural selection has motivated parents to change their behavior of caring for eggs and young children, whereby the reproduction inside freshwater mussels not only provides an incubation environment but also helps protect the offspring after hatching. from predators.

The team compared modern leeches with a fossil specimen from the middle of the Three Gorges and came to the conclusion that they were slow evolutionary creatures. The analysis of gastric composition also shows that seven leeches living inside freshwater mussels sometimes leave their hosts to suck fish blood, especially during the pre-spawning period.

Together with amphibians such as newts and breeds, freshwater mussels are one of the fastest extinct groups of animals. The team's new findings show that the decline of species populations has a much greater impact on the ecosystem than previously thought by scientists.