Research conducted at the University of Hawai’i (UH) at the Mānoa School of Ocean and Earth Science and Technology (SOEST) on a marine sponge in Kāne’ohe Bay, O? Ahu revealed a strategy of unique diet, in which the terry animal acquires important components of its diet. of symbiotic bacteria living in the sponge.
Coral reefs are one of Hawaii’s most important natural resources and support the state’s fisheries and economy. Marine sponges are important components of coral reef ecosystems, but in Hawaii, the Indo-Australian sponge Mycale grandis is an invasive alien species that was only first documented on the islands in the late 1980s. 1990. M. grandis is now found in and near major ports on the major Hawaiian Islands as well as Kāneʻohe Bay.
Alien and invasive species are one of the threats to endemic and native species, which are vulnerable due to their evolution in the remote archipelago. M. grandis competes with coral for space on the reef, but unlike coral, which builds hard bedrock with its skeletons, M. grandis is a soft, non-reef-building animal and does not provide the same habitat for other reef organisms.
In a study led by Dr Joy Leilei Shih for her doctoral research at UH Mānoa, the diet of M. grandis sponges collected from Kāneʻohe Bay was elucidated using a novel application of a technique that relies on natural stable isotopes to understand the origin of specific compounds in the tissues of plants and animals. In this case, the team tested where the amino acids, the building blocks of proteins in tissue, come from in the sponge. Did they come from food captured and filtered in seawater or were they supplied to the sponge by the microbes living inside the sponge itself?
When one organism consumes another, the elemental properties of the prey are retained and leave a unique chemical pattern with the predator. By evaluating the chemical difference between the tissues of predators and prey, Shih and his colleagues found that the diet of sponges did not come from photosynthetic microbes (like those seen in corals) and that the diet of M. grandis did not. did not follow the general patterns of other multicellular animals. Instead, the isotopic patterns of the sponge and its symbiotic microbes were not different from each other, indicating that the sponge feeds on the uptake of amino acids from its symbiotic microbes.
“While we knew that sponge symbionts play an important role in their diet, the mechanism by which this happened was unknown,” Shih said. “The only way to produce the observed isotopic amino acid pattern, or the fingerprint, if you will, is through the direct transfer of amino acids from their symbiotic bacteria.”
“The patterns we have detected in M. grandis and its symbionts are very interesting, as they suggest that sponges can actively capture material in seawater to meet the needs of their microbial community, which in turn provides sponge from the building blocks of essential tissues, “said Dr Chris Wall, postdoctoral researcher at UH Mānoa and co-author of the study.
“The symbiosis that we see between the sponge and its microbial community is remarkable,” Shih said. “We know that sponges depend on their symbionts for a variety of purposes including chemical defense, elimination of metabolites, and now we have an overview of this well-tuned and efficient feeding strategy and the major role these microbial symbionts play. in sponge nutrition. The intimate relationship between sponges and their symbionts developed over their long evolutionary history. Sponges are the oldest multicellular animal on earth. This is why they are so well adapted and resilient. “
Marine sponges in Hawai’i are not well studied. A 2017 study by the MarineGEO Hawai’i program organized by the Smithsonian Institution identified 150 species of sponges unheard of in Hawai’i, about a third of which are new species. Previously, only about ten species of sponges were known in Kāneʻohe Bay. The researchers’ new approach to studying sponge feeding strategies can be applied to future research on other marine sponges in Hawai’i and elsewhere. Sponges play an important role in the nutrient dynamics of coral reefs, and in the future, sponges may rise to dominate coral reefs as corals decline under direct pressure from human activity and change. climate. This work brings new knowledge on the biology of sponges and shows the importance of marine microbes in the diet of an invasive sponge.
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