Genetic Diversity of Ramisyllis Across Japanese Endemic Waters (BSc Thesis)

Branching worms (Syllidae, "ribbon clade") are among the most unusual annelids known. These remarkable animals possess a single head but multiple randomly branching, asymmetrical posterior ends that ramify throughout the water canal system of their sponge host. Despite its considerable size within its host, the worm does not appear to disrupt the sponge's water intake, suggesting a symbiotic relationship in which the sponge provides shelter and food while the worm may act as a 'housekeeper'. Although the precise nature of this partnership is still under study, the intimacy of the association raises the question of how the worm's evolutionary history has been shaped by geographic and oceanographic factors.
To date, only three species have been described, making them an exceptionally rare phenomenon. This project focuses on one of these species, Ramisyllis kingghidorahi, which is endemic to Japanese waters. The Sea of Japan is an oceanographic region characterised by high levels of endemism across many marine invertebrate groups, driven by complex current systems, temperature gradients, and historical isolation. Preliminary data suggest genetic differentiation among R. kingghidorahi from different Japanese localities, indicating that gene flow may be restricted within this enclosed sea. To fully characterise the population structure and phylogeography of the species, a broader sampling effort across Japanese waters is planned. This BSc project contributes the first steps towards this goal by focusing on specimens collected from Sado Island, establishing a baseline characterisation of genetic diversity within this locality that future sampling efforts can build upon.

Project description

Using multilocus sequencing of mitochondrial and nuclear markers, you will characterise the genetic diversity within R. kingghidorahi specimens from Sado Island. This project involves extensive molecular lab work, including DNA extraction and PCR amplification of multiple markers, followed by phylogenetic and population genetic analyses. You will assess levels of genetic variation, test for signals of population structure or cryptic diversity within the Sado population, and place your findings in the context of the oceanographic characteristics of the Sea of Japan. As this project represents the first systematic genetic assessment of R. kingghidorahi from a single locality, your results will form a critical foundation for future comparative work across the species' range.


Main questions:

(I) What is the genetic diversity of R. kingghidorahi among specimens from Sado Island?
(II) Is there evidence for cryptic diversity or genetic structure within the Sado population?
(III) How do the observed patterns of genetic variation relate to the oceanographic characteristics of the Sea of Japan?
(IV) Do the results provide preliminary insights into potential restricted gene flow that can guide future sampling efforts across the species' range?