When a marine organism once thought to be globally extinct was found in Singapore waters in 2011, marine scientists were overjoyed, twice over. They had found not one, but two neptune’s cup sponges.
Despite its size, Singapore abounds with animal and plant species. Conserving them is an ongoing challenge. In this third of a five-part series leading to Singapore Biodiversity Week starting on May 20, The Straits Times highlights a species saved from extinction: the neptune's cup sponge.
Audrey Tan Straits Times 12 May 17;
When a marine organism once thought to be globally extinct was found in Singapore waters in 2011, marine scientists were overjoyed, twice over. They had found not one, but two neptune's cup sponges.
Unfortunately, the heavily sedimented waters around Singapore allowed only one to be relocated.
However, Lady Luck smiled on them last year: the scientists rediscovered the "missing" sponge, nicknamed Neppie by the team who found it in 2011.
That is not all. They also found nearby two more individuals.
The discovery of the sponges, which resemble large wineglasses, seemed a toast to serendipity.
Said Dr Karenne Tun, director of the coastal and marine branch at National Parks Board's (NParks) National Biodiversity Centre: "We knew Neppie was about 60m away from the original sponge. So we formed a chain - five of us held on to a rope at 2m intervals, and we just swam in that direction."
Dr Tun was part of the team that discovered Neppie in 2011 and led a team of five that found it again last year. Using finstrokes to measure distance - one kick cycle was roughly 1m - the four divers from NParks and Mr Stephen Beng from the Nature Society (Singapore) swam about 60m in the waters off St John's Island without finding anything.
But at the 60m mark, Mr Beng tugged on the rope. Translation: "Sponge!" The team agreed to tug on the rope if there was good news before they descended 10m underwater. Amid circular jubilant swims around Neppie, another member of the team, Mr Koh Kwan Siong, a manager at the coastal and marine branch of NParks' National Biodiversity Centre, found two more.
More eyes underwater, favourable current conditions and good underwater visibility of about 3m that day, instead of the usual 1m to 2m, contributed to the discovery, said Dr Tun.
There are now five known neptune's cup sponges in Singapore - one more was found off Semakau Island in 2014, and moved to the Sisters' Islands Marine Park. Two more neptune's cup sponges were spotted off Singapore's southern shores, but the divers who found them did not log their exact locations.
Dr Tun hopes good visibility and more surveys of Singapore's seas would uncover the duo and, hopefully, other individuals too.
Meanwhile, NParks' goal is to see if the five sponges can help to build up the organism's population in Singapore's waters, where they were once found in abundance until overharvesting by museums and private collectors, and individuals who harvested it so they may use the cup-like structure as a bathtub for infants, nearly wiped them out.
NParks is working with researcher Lim Swee Cheng, of the National University of Singapore's Tropical Marine Science Institute, on a species recovery programme for the sponge.
Said Mr Lim: "The three discovered sponges look young. It shows larvae from this species, either from Singapore or neighbouring waters, recently settled in our waters."
But how exactly the sponges reproduce is still a mystery the scientists hope to solve through various methods, including studying its tissue to figure out when it reaches sexual maturity.
Three of the five sponges have been moved to Sisters' Islands Marine Park, and NParks plans to take the remaining two there soon. Living in close proximity gives them a better chance to reproduce and spread the eggs around Singapore waters, said Mr Lim.
"But it is also important we find out more about its life history, like when the eggs and sperm are released. Only after these studies are done, can we propagate this iconic species effectively," he added.
The scientists also discovered that the neptune's cup sponge grows fast, and had a quick rate of regeneration. Bite marks on Neppie left by turtles had been replaced with new tissue in several months. It was previously thought the sponge was likely a slow-growing species, thus contributing to its disappearance.
"Now that we know the sponge regenerates quickly, it might be possible to propagate them by taking cuttings from them - similar to how plants are propagated," said Dr Tun.
Sponges in general are natural water filters which draw in water to extract nutrients. Good sponge diversity can help to manage water quality in the reef, which provides shelter and food for other marine organisms such as fish.
