Sponges are considered to be the oldest form of multicellular life on Earth. Fossils of microscopic sponges were found in rocks in Africa that date back to 760 million years ago. Given this potential great age, it is not surprising to find that sponges are an extremely primitive, although highly successful, form of life.
Sponges, like those seen in today’s photo, are simple colonies of individuals all working together to achieve common goals – eating and reproducing. The typical hollow sack-like structure of sponges facilitates both goals. Examined closely, the outer surface of sponges is covered by tiny pores through which water is drawn by the beating of the flagella (whip-like tails) of specialized cells in the colony. Flowing through the channels microscopic planktonic organisms are removed and used as food for the colony. The filtered water passes into channels that eventually lead back to the outside, often through a large chamber that gives a sponge the basket or bottle shape with which we are familiar.
The individual cells in a sponge are fairly independent of each other, leading to an ability that, if true, is amazing. It is said that at least some sponge species can be pushed through a sieve to break the cells apart and then reform as the cells get back together. I’ve never seen this first hand, and I doubt that the new sponge re-forms in any way purposefully resembling the original sponge, but it can apparently become a colony again.
Today’s photo was taken at a location on Rainbow Reef off the island of Vanua Levu known as Freeway. The beautiful green and red colors of the sponges caught my eye, but I’ve been unable to identify any of them.
This photo was taken with a Canon EF100 mm f/2.8 macro lens on a Canon EOS 5D Mk. III in an Ikelite underwater housing. Lighting was provided be an Ikelite DS161 strobe set to eTTL exposure. The overall exposure was set to 1/60 sec. at f/11 and ISO 200.