DIVE DRY WITH DR. BILL #867: A REAL SPONGE BATH
Now I'm an old enough geezer to remember taking a bath with a real sponge. Not the silly cellulose ones people use these days, but from a real formerly living thing. I also remember going to Tarpon Springs, Florida, back in the 1950s to watch the sponge divers harvest them. Of course I'm glad we have mostly stopped taking these creatures and switched to man-made, non-living cellulose to bathe and wash dishes!
Today most people, at least the youngsters, get their kicks from SpongeBob SquarePants. When I dove in Puerto Galera, Philippines, the pillow case on my bed featured him... but that's as close as I got. As a diver, I encounter real sponges frequently both in our local waters and when I travel internationally. Many are quite beautiful to observe and film.
But what is a sponge? They are certainly not evolutionarily advanced life forms... no brain. In fact they are the oldest multi-cellular life form... even older than my geezer friends. The first ones appeared way back in the pre-Cambrian, more than 540 million years ago. During this period many different life forms appeared in the seas... but there were no critters on dry land.
Sponges belong to the Phylum Porifera. They are composed of a number of different cells with several different functions, but have no real organs or tissues (not even Kleenex when they get the sniffles!). They have no digestive, circulatory or respiratory systems. The name Porifera means "pore bearing." Sponges have internal cavities or canals through which sea water flows. There are incurrent pores through which the water enters and excurrent openings through which it exits.
Cells known as choanocytes have whip-like flagella within the canals that create the water flow. Munching by sponges is accomplished by filter feeding bacteria and other small organisms out of the water. Not exactly a diet I'd thrive on, but most sponges survive on it quite nicely. A few of the more than 10,000 species are actually carnivorous, capturing small crustaceans and others have tiny symbiotic photosynthetic organisms that produce excess food and oxygen the sponge utilizes.
Since these are invertebrates with no skeletal system, something has to hold the cells together. This is accomplished in several different ways. Some use a gelatinous matrix known as a mesohyl which is made of collagen. Others reinforce this in several ways. Demosponges, which include the majority of sponges, use fibrin fibers to firm them up. They are the ones used as bath sponges. Others use mineral structures known as spicules. These may include calcium carbon and silica. Those would be a bit scratchy to bathe with!
Sponges using calcium carbonate spicules are usually found in shallower water where the mineral is more easily created. The glass sponges which use silica are found in colder waters such as near the poles or in the deep ocean. Spicules are often used to identify species since the external morphology of a sponge may vary significantly due to environmental factors.
I know my readers have been chafing at the bit to learn about the sex life of sponges, so I'll titillate you. A common form of reproduction involves the release of sperm into the surrounding water. It is then either taken in by another sponge to fertilize gametes inside, or the female gametes are also cast into the water for external fertilization. In either case the fertilized ovum develops into a free-swimming larva. A sponge may also develop from fragments of another.
Now aren't you glad I let you sit in for a little sex education. As a biology teacher, I never had a chance to teach that subject. I think many of my students learned it through trial and error late at night. Sigh, as a single man at a remote school I rarely had a chance to myself.
Finally, there are many different specialized cells in sponges. Lophocytres and collencytes produce collagen. Rhabdiferous cells secrete sugars that help constitute the mesohyl. Oocytes and spermatocytes produce the sexual gametes. Sclerocytes secrete the spicules. Spongoctyes produce collagen for the spongin. Myocytes conduct signals between the sponge's cells. Perhaps most important are the archaeocytes, also known as amoebocytes, that are capable of transforming into any other kind of cell. I wonder if one could develop into a lovely and intelligent mermaid for the good doctor?
© 2020 Dr. Bill Bushing. For the entire archived set of over 850 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: A variety of sponges from the Caribbean (Aruba and Bonaire)
Now I'm an old enough geezer to remember taking a bath with a real sponge. Not the silly cellulose ones people use these days, but from a real formerly living thing. I also remember going to Tarpon Springs, Florida, back in the 1950s to watch the sponge divers harvest them. Of course I'm glad we have mostly stopped taking these creatures and switched to man-made, non-living cellulose to bathe and wash dishes!
Today most people, at least the youngsters, get their kicks from SpongeBob SquarePants. When I dove in Puerto Galera, Philippines, the pillow case on my bed featured him... but that's as close as I got. As a diver, I encounter real sponges frequently both in our local waters and when I travel internationally. Many are quite beautiful to observe and film.
But what is a sponge? They are certainly not evolutionarily advanced life forms... no brain. In fact they are the oldest multi-cellular life form... even older than my geezer friends. The first ones appeared way back in the pre-Cambrian, more than 540 million years ago. During this period many different life forms appeared in the seas... but there were no critters on dry land.
Sponges belong to the Phylum Porifera. They are composed of a number of different cells with several different functions, but have no real organs or tissues (not even Kleenex when they get the sniffles!). They have no digestive, circulatory or respiratory systems. The name Porifera means "pore bearing." Sponges have internal cavities or canals through which sea water flows. There are incurrent pores through which the water enters and excurrent openings through which it exits.
Cells known as choanocytes have whip-like flagella within the canals that create the water flow. Munching by sponges is accomplished by filter feeding bacteria and other small organisms out of the water. Not exactly a diet I'd thrive on, but most sponges survive on it quite nicely. A few of the more than 10,000 species are actually carnivorous, capturing small crustaceans and others have tiny symbiotic photosynthetic organisms that produce excess food and oxygen the sponge utilizes.
Since these are invertebrates with no skeletal system, something has to hold the cells together. This is accomplished in several different ways. Some use a gelatinous matrix known as a mesohyl which is made of collagen. Others reinforce this in several ways. Demosponges, which include the majority of sponges, use fibrin fibers to firm them up. They are the ones used as bath sponges. Others use mineral structures known as spicules. These may include calcium carbon and silica. Those would be a bit scratchy to bathe with!
Sponges using calcium carbonate spicules are usually found in shallower water where the mineral is more easily created. The glass sponges which use silica are found in colder waters such as near the poles or in the deep ocean. Spicules are often used to identify species since the external morphology of a sponge may vary significantly due to environmental factors.
I know my readers have been chafing at the bit to learn about the sex life of sponges, so I'll titillate you. A common form of reproduction involves the release of sperm into the surrounding water. It is then either taken in by another sponge to fertilize gametes inside, or the female gametes are also cast into the water for external fertilization. In either case the fertilized ovum develops into a free-swimming larva. A sponge may also develop from fragments of another.
Now aren't you glad I let you sit in for a little sex education. As a biology teacher, I never had a chance to teach that subject. I think many of my students learned it through trial and error late at night. Sigh, as a single man at a remote school I rarely had a chance to myself.
Finally, there are many different specialized cells in sponges. Lophocytres and collencytes produce collagen. Rhabdiferous cells secrete sugars that help constitute the mesohyl. Oocytes and spermatocytes produce the sexual gametes. Sclerocytes secrete the spicules. Spongoctyes produce collagen for the spongin. Myocytes conduct signals between the sponge's cells. Perhaps most important are the archaeocytes, also known as amoebocytes, that are capable of transforming into any other kind of cell. I wonder if one could develop into a lovely and intelligent mermaid for the good doctor?
© 2020 Dr. Bill Bushing. For the entire archived set of over 850 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: A variety of sponges from the Caribbean (Aruba and Bonaire)
