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We’re all familiar with sponges - those colourful, handy and very affordable synthetic workhorses easily obtainable at the local market, and in bulk, usually 10 for a $1. Most well-stocked bath aisles also offer an assortment of “spongy” bathing aids and accessories that help make your evening soak in the tub that much more relaxing and enjoyable. True bath lovers, though, will agree that for pure bathing luxury there’s no contest when it comes to choosing between the synthetic sponge or the more costly natural sea sponge. Why? Natural sea sponges are much softer, they absorb more water, don’t retain odours and they’ll last much longer than their fake counterparts. But does the average bathing beauty know that their sea sponges are actually the skeletons of a once living sea creature?
Until the mid-1700’s, the texture and appearance of sponges suggested they were plants. Zoologists eventually debunked this theory, re-classifying the sea sponge as a simple multi-cellular, bottom-dwelling animal called “Porifera”. The word means “pore-bearing” and refers to the many tiny openings or holes visible on all sponges. There are 3 additional sub-species of Porifera: the Calcispongiae, the Hyalospongiae, and the Demospongiae. Sponges are found in every ocean of the world, particularly the Antarctic, and can thrive in not only shallow waters but the deepest regions of the seas, including sea caves where there’s little or no light. There are even some varieties that live in fresh water locations. Scientists have identified approximately 5000 species of sponges thus far.
Most sea sponges attach themselves to coral, rocks or rock walls, shell beds and other hard or stable surfaces along the ocean floor. There are a few varieties that are free-standing, however, like the Barrel sponge. All sponges are commonly referred to as “filter feeders”, that is, they capture and digest bacteria, plankton, and other organic particulates floating in the water. The outer holes or pores of a sponge are called “ostia”. These lead to larger internal pores called “oscula”. Inside these larger canals are still more chambers, all lined with “collar cells”, the tops of which are funnel shaped. Minute appendages called “flagellum” hang from these specialized funnels and as these flagellum beat back and forth, they force water inside the sponge. Nutrients and oxygen are absorbed and wastes and carbon monoxide are eventually filtered out. Still other cells called “amebocytes” transport these filtered nutrients further inside the sponge.
Most sponges are hermaphrodites, that is, a single sponge can display either male or female tendencies as required. They release living young through the outgoing oscula. The new-born baby sponges resemble plankton and after a few days of free floating will attach themselves to a hard surface and begin to grow. Sponges have a life span of a few months to 20 years or more. They also have the ability to regenerate into new individuals from even the tiniest fragments of the original. This is of particular value when sponge habitats begin to degrade or can no longer support the growing population or if food supplies suddenly diminish. When any of these variables occur the sponges fragment and lie dormant until such time as growing conditions once again become ideal.
Sea sponges come in many different shapes and sizes and literally every colour of the rainbow depending on their location. Some look like thin, swaying tree branches or floating bushes. Others resemble shapely urns or vases. Still others look like floating cylindrical tubes or swaying fans. There are even some sponges that resemble common flowers like the tulip and still more that have no definitive shape at all. While most sponges grow to only a few centimetres, there are certain species that balloon to many times the size of a man. Scientists believe that age, environmental conditions and food supply may be related to the size certain sponges achieve.
In some areas of the ocean like the warmer waters around Australia there are large sponge gardens that all manner of sea life call home. Like earthbound gardens, sponge gardens are delicate habitats. Even the most minute change in conditions can impact these floating aquatic arboretums. Pollution, introduced species, over-harvesting by sponge divers, and the warming of the oceans over the last few decades is having an increasingly negative impact on sponges and sponge gardens. Commercial harvesting of sponges is done either by manual hooking, harpooning or more automated deepwater fishing. Once the sponges have been cleaned of all their living cells, these animal “skeletons” are ready for sale.
Before the advent of the synthetic age early Mediterranean and European civilizations used the natural sea sponge for many daily tasks like painting, washing and sweeping floors or as a way to gather drinking water when cups or other vessels were unavailable. Roman soldiers used them to line their helmets and doctors and healers used the burnt sponge as a therapeutic aid for certain maladies. Nowadays the natural sponge’s many uses has dwindled to selected areas like arts and crafts, painting and re-decorating, or for use in operating rooms during surgical procedures. Modern science is also investigating properties found within these sea creatures that could one day treat a host of human diseases.
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