Sponges first evolved on Earth hundreds of millions of years ago, which means these organisms (including their associated symbiotic microbes) have had an incredible, lengthy opportunity to evolve unique biologically active compounds within their cells. Recently, researchers have discovered possible medical treatments for humans in sponge compounds, and now it’s finally their turn in the scientific spotlight. In 2011, researchers reviewed hundred potential anticancer agents, and one of the most prolific sources was sponges. Eighteen sources derived from Porifera (marine sponges), and of those, 6 of those have been put through preclinical trials. Every sponge contains secondary metabolites called alkaloids, or toxicants, which allow the organism to protect itself against predators like fish. Secondary metabolites are organic compounds that allow organisms to perform tasks that are nonessential to their immediate survival but may be crucial for long-term survivability, traits of reproduction, appearance, etc. The variety of metabolites created serve as protection from predators, microbial infections, biofouling, and overgrowth by other sessile organisms, like barnacles and coral.
Sponges that live in harsher environments and environments that have more competition for food tend to produce more usable compounds. Japan, Indonesia, Korea, and Australia all have competitive reefs typified by high numbers of species. Sponges from Japan alone have provided a staggering 332 compounds. That number of compounds is approximately the same as China and Australia’s combined! Sponges can live in a large range of environments of many depths, water salinities and temperatures. Marine sponges, which represent the vast majority of known sponge species, have yielded the highest number of compounds. They have bioactivities that include anticancer, antiviral, antibacterial, antifungal, antiprotozoal, antihelmintic, anti-inflammatory, immunosuppressive, neurosuppressive, neuroprotective, and antifouling properties, among a range of other known and yet-to-be discovered abilities. We'll be covering some of the different medicines derived from sponges in an upcoming post, so stay tuned.
The search for ocean-derived solutions to widespread medical issues developed significantly in the 1950’s with Bergmann and Feeney’s discovery of nucleoside derivatives in the sponge Tethya crypta. Nucleoside derivatives are linked to anticancer and antiviral agents. Even so, the utilization of sponges for their medically applicable metabolites didn’t really take off until the late 1960’s. In the 1980’s, marine chemists and pharmacologists worked together to look at the toxins in the sponge’s nervous system. In the past decade (2001-2010), 8,368 new compounds were identified from sponges, accounting for nearly half of the total findings from sponges since 1951.
One major problem remains with pursuing marine sponge-based medicine. If a large number of people ultimately rely on medical compounds derived from marine sponges there needs to be a long term sustainable plan to harvest or otherwise generate the compounds. Because Sponges have the potential to provide many possible applications to widespread diseases and medical issues, a sustainable method of collection needs to be found. Sponges are crucial to the health and productivity of marine environments. For instance, the sponge Geodia barretti can filter up to 1,000 liters of water per kilogram of tissue each day. They absorb pollutants and overall allow for regulated coral reefs. However many reefs are currently endangered, a large percentage of reefs have disappeared in the last 50 years and many more are at risk in the next few decades. If sponges are extracted in large quantities for their valuable compounds, it would likely contribute to coral reef destruction.
Currently, most sponges extracted from reefs are acquired for research purposes, using underwater remotely operated vehicles (ROVs) that essentially cut off each sponge from the reef structure. For example, the Deep Reef Observation Project (DROP)’s manmade metal pipe is used to pry off stony specimens of “sclerosponge.” While this is an environmentally sound practice for collecting only a few specimens, in order to extract compounds for large numbers of medicinal applications, other methods must be developed. One possible solution may be sponge farming, where sponges could be grown in the ocean on large nets and then collected from the nets. This approach could also be used to battle the increasing amounts of pollutants in the water by increasing the number of sponges in coastal areas where pollutants are commonly released. An artificial method that could be used to extract only the compounds of interest is cell culture, that is, by multiplying only specific bioactive cells, living sponges would sustain little to no damage. A common solution for producing these natural products is synthesis of compounds in laboratories.
Ultimately, it is important that we recognize that if we wish to harness the medicinal power of sponges, as they say “With great power, comes great responsibility”.
By—Zoe Grabenstetter, Intern [Editors: Allen Collins, Liz Boatman, and Cheryl Ames]
More about natural products of sponges below:
Florida’s Atlantic University’s extraction of sponges
DROP’s program to find anticancer compounds on the sea floor
Other articles about marine animal’s medical products:
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