How Evolution Shapes the Microbes in Octopus Reproductive Organs

Jim Crocker
23rd March, 2024

How Evolution Shapes the Microbes in Octopus Reproductive Organs

Image Source: Natural Science News, 2024

Key Findings

  • Cephalopods have a special organ, the ANG, housing bacteria that protect their eggs
  • Different cephalopod species have unique bacterial communities in their ANGs
  • Closely related cephalopods tend to have similar, yet distinct, bacterial partners
In the underwater world of cephalopods, creatures like squids and cuttlefish harbor a secret weapon within their reproductive systems—a special organ called the accessory nidamental gland (ANG). This organ is not just a part of the reproductive system; it plays a crucial role in defending their eggs against harmful microbes and organisms that could potentially damage or infect them. A recent study by researchers at the University of Connecticut[1] has delved into the microscopic universe of the ANG to understand the diversity of bacteria that reside within it and how these relationships may have evolved. The study focused on the ANG microbiome of 11 cephalopod species from four different families. These species were collected from seven different geographic locations, providing a broad scope for analysis. Using a technique called 16S rRNA gene community analysis, the researchers were able to identify and classify the bacteria living within the ANGs. They discovered that while all ANGs contained bacteria from the classes Alphaproteobacteria, Gammaproteobacteria, and Flavobacteriia, the specific bacterial communities varied significantly between cephalopod families. Interestingly, despite the vast distances separating their habitats, members of the Sepiolidae family, which includes bobtail squids, shared many bacterial taxa. About half of the bacteria found in their ANGs belonged to the Opitutae (Verrucomicrobia) and Ruegeria (Alphaproteobacteria) species. This finding resonates with earlier research[2] that demonstrated environmental bacteria's essential role in the development of the ANG in the Hawaiian bobtail squid, Euprymna scolopes. In that study, it was shown that without exposure to environmental bacteria, the ANG did not develop properly, highlighting the importance of these symbiotic relationships. The study also tested for a concept known as phylosymbiosis, which suggests that the evolutionary relationship between host organisms might be reflected in the similarities of their associated microbial communities. A positive correlation was indeed found between the phylogenetic distance of the host cephalopods and the dissimilarity of their ANG bacterial communities. This suggests that closely related cephalopods tend to select similar, yet distinct, symbionts from the available bacterial taxa. This finding expands on previous research[3], which reported that the gut microbiomes of cephalopods are composed of distinctive microbes and are strongly associated with their phylogeny. The study's findings are significant because they provide a clearer picture of the microbial diversity within cephalopod ANGs and hint at the evolutionary processes that may influence these symbiotic relationships. The researchers' work underscores the complexity of these relationships and the potential for these symbionts to contribute to the host's fitness, possibly through antimicrobial activities that protect the eggs. The research also builds on the broader understanding of animal-microbe interactions. A previous study[4] on microscopic marine invertebrates suggested that host identity is a minor factor shaping microbiomes, with the presence of guilds of microorganisms that are not host-specific. However, the current study indicates that in the case of cephalopods, the host's evolutionary history does play a significant role in shaping its microbiome, particularly in the ANG. In conclusion, the University of Connecticut's research has illuminated the intricate and diverse world of bacteria living symbiotically with cephalopods. By analyzing the ANG microbiomes across various species and families, the study has revealed that these microbial communities are not random assemblages but are influenced by the evolutionary history of their hosts. This insight into the complex interplay between cephalopods and their bacterial partners opens the door to further exploration of these relationships and their implications for the health and survival of these fascinating marine animals.

GeneticsMarine BiologyEvolution

References

Main Study

1) Evolutionary history influences the microbiomes of a female symbiotic reproductive organ in cephalopods.

Published 20th March, 2024

https://doi.org/10.1128/aem.00990-23

Related Studies

2) "Failure To Launch": Development of a Reproductive Organ Linked to Symbiotic Bacteria.

https://doi.org/10.1128/mbio.02131-22

3) Host phylogeny, habitat, and diet are main drivers of the cephalopod and mollusk gut microbiome.

https://doi.org/10.1186/s42523-022-00184-x

4) Microbiomes of microscopic marine invertebrates do not reveal signatures of phylosymbiosis.

https://doi.org/10.1038/s41564-022-01125-9


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