In the early scientific studies, sponges were considered marine plants, and it was not until the mid-19th century that they were recognized as what they are: animals. Fossil specimens found demonstrate that sponges existed on our planet 500 million years before the first human beings. With 4,500 known species, of which only 150 species live in freshwater, sponges can be found in all the seas of the world and appear to have adapted well to all conditions of life. During the Galatea expedition, sponges were recorded at a depth of 6,400 meters.
Sponges have a chimney-like shape, which allows them to filter water to obtain their food. The external wall of the sponge has pores through which water is filtered. The cells, which feed independently of each other, take nutrients from this water that passes through the pores, and waste exits through the main cavity of the chimney. A sponge the size shown in the photo can filter about two liters of water per minute, which means it can filter over a million liters of seawater per year.
Precisely, the fact that cells feed independently without the need for a digestive system is what gives sponges their most surprising characteristic. If a piece of sponge breaks off from the animal, it can attach itself to the seabed and continue filtering water, eventually forming a new animal. Furthermore, if the entire individual is passed through a fine silk cloth, separating it into tiny particles, these particles will settle on the bottom, forming small clusters that, over time, will develop into fully grown individuals.
Sponges have had a strong connection with humans for a long time. The Greeks used them as water containers instead of canteens, and the Romans created the first version of a pacifier with them, so it is not surprising that Christ on the cross was given a drink “from a sponge.” Fortunately, today technology has replaced the use of marine sponges with synthetic sponges that are used in almost every household around the world.
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