An invasive species of sponge common throughout Hawaii packs its own lunch, scientists have found.

That’s the conclusion from a study of the Indo- Australian Mycale grandis, the orange keyhole sponge, which arrived at Pearl Harbor in 1996.

The invader is now taking up residence in and near major harbors in the main Hawaiian Islands and in Kaneohe Bay.

But unlike most other sponges, M. grandis does not get nutrients directly from seawater.

Instead, the sponges consume amino acids, the building blocks of proteins, from tiny passengers.

Scientists at the University of Hawaii used chemical fingerprints called isotopes to track the nutrients and found they came from cooperative or symbiotic microbes within the sponge itself.

“The symbiosis we see between the sponge and its microbial community is remarkable,” Joy Leilei Shih, a doctoral student and principal researcher on the project, said in a release Wednesday. “We know that sponges rely on their symbionts for a variety of purposes including chemical defense, metabolite removal, and now we have insight into 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,” she added. “Sponges are the oldest multi-cellular animal on earth. That’s why they are so well-adapted and resilient.”

The findings appear in the journal Microbial Ecology.

Sponges in Hawaii waters pose a bit of a mystery.

A study by the Smithsonian Institution’s MarineGEO Hawai‘i program in 2017 identified 150 previously unseen sponge species, roughly one-third of them new species. Previously, only about 10 sponge species were known to exist in Kaneohe Bay.

Sponges play an important role in the nutrient dynamics of coral reefs, the scientists said, and in the future sponges might dominate reefs as corals decline from human pressure and climate change.

“The patterns we detected in M. grandis and its symbionts are very interesting, as they suggest sponges may be actively capturing materials in seawater to support the needs of their microbial community, which in turn supply the sponge with essential tissue building blocks,” said Chris Wall, a postdoctoral researcher in the UH School of Ocean and Earth Science and Technology and a co-author of the study.