Dominic Stone
Sponges are multicellular organisms that consist of a jelly-like mesohyl sandwiched between two thin layers of cells. They are known to have unspecialized cells that can transform into other types and migrate between the main cell layers and the mesohyl. Sponges do not possess any structures that can be considered organs, and they lack complex nervous, digestive, or circulatory systems. Interestingly, sponges are capable of movement despite lacking muscle cells. So, how do sponges move without muscles, and do they have any muscle-like structures?
| Characteristics | Values |
|---|---|
| Muscle contractions | Sponges are able to contract without muscles |
| Movement | Sponges are not incapable of movement |
| Muscle cells | Sponges do not have muscle cells |
| Contractile cells | Sponges have contractile cells |
| Contractile module | Sponges have a muscle-like contractile module |
| Neurons | Sponges lack neurons |
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What You'll Learn
Sponges can contract without muscles
Sponges are multicellular organisms that consist of jelly-like mesohyl sandwiched between two thin layers of cells. They usually have tube-like bodies full of pores and channels that allow water to circulate through them. Sponges are defined as sessile metazoans, or multicelled immobile animals, that have water intake and outlet openings connected by chambers lined with choanocytes, or collar cells. These collar cells have whip-like flagella that create a constant water flow through the sponge's body, allowing it to obtain food and oxygen and remove waste.
Sponges do not have complex nervous, digestive, or circulatory systems. Instead, they rely on the water flow system to support these functions. They filter food particles out of the water flowing through them and can also perform movements that are coordinated across their bodies, such as contractions.
While sponges do not have muscles, they are capable of movement and contraction. A group of scientists led by Dr. Michael Nickel of Friedrich Schiller University Jena, Germany, investigated the evolutionary origins of muscle cells and found that sponge epithelial cells, or pinacozytes, cause strong body contractions in sponges. This research provides new insights into the evolutionary development of musculature and suggests that muscle cells likely evolved from a common contractile cellular predecessor.
Sponges have unspecialized cells that can transform into other types and migrate between the main cell layers and the mesohyl. This ability to remodel their bodies allows them to perform coordinated movements and contractions, even without specialized muscle cells.
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Sponges have muscle-like contractile modules
Sponges are multicellular organisms with jelly-like mesohyl sandwiched between two thin layers of cells. They usually have tube-like bodies full of pores and channels that allow water to circulate through them. Sponges do not have complex nervous, digestive, or circulatory systems. Instead, they rely on water flow through their bodies to obtain food and oxygen and to remove waste. Sponges are believed to have been the first outgroup to branch off the evolutionary tree from the common ancestor of all animals.
Sponges are capable of movement and can contract without muscles. They have muscle-like contractile modules, and their contractile module shares elements of homology with contractile tissues in other animals, including muscles. This indicates a descent from a common, multifunctional tissue in the animal stem lineage. The contractile tissues that line water canals in sponges can dynamically remodel in response to flow and reform normally from stem cells.
Sponges have myocytes or "muscle cells" that conduct signals and cause parts of the animal to contract. They also have archaeocytes or amoebocytes, which are amoeba-like cells capable of transforming into any other type of cell. These cells play important roles in feeding and clearing debris that blocks the ostia.
Zoologists are interested in studying the movement of sponges without muscles. A group of scientists from Friedrich Schiller University Jena, Germany, is specifically researching the evolutionary forerunners from which muscle cells derived. They generated three-dimensional images using synchrotron radiation-based X-ray microtomography to compare and visualize the 3D structure of contracted and expanded sponges.
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Sponges have no complex nervous, digestive or circulatory systems
Sponges are multicellular organisms with jelly-like mesohyl sandwiched between two thin layers of cells. They usually have tube-like bodies full of pores and channels that allow water to circulate through them. Sponges do not have complex nervous, digestive or circulatory systems. Instead, they rely on a constant water flow through their bodies to obtain food and oxygen and to remove waste. This water flow is usually facilitated by the flagella movements of "collar cells".
Sponges are filter-feeding experts, straining thousands of litres of water through their bodies every day to collect their food. They achieve this complex behaviour without a brain or even a single neuron. Sponge cells do, however, communicate with each other within their digestive chambers, with the help of synapse genes.
Sponges do have muscle cells, or "myocytes", which conduct signals and cause parts of the animal to contract. They also have "grey cells", which act as an immune system, and "archaeocytes" or "amoebocytes", which are totipotent and can transform into any other type of cell. These archaeocytes also have important roles in feeding and clearing debris that blocks the ostia.
Sponges are mostly marine species, ranging in habitat from tidal zones to depths of over 8,800m, although there are some freshwater species. All adult sponges are sessile, attaching to an underwater surface and remaining fixed in place.
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Sponges are multicellular organisms
Sponges consist of jelly-like mesohyl sandwiched between two thin layers of cells. They usually have tube-like bodies full of pores and channels that allow water to circulate through them. The mesohyl functions as an endoskeleton in most sponges and is the only skeleton in soft sponges that encrust hard surfaces. In some sponges, the mesohyl is stiffened by mineral spicules, spongin fibres, or both. Sponges have unspecialised cells that can transform into other types and often migrate between the main cell layers and the mesohyl.
Sponges do not have complex nervous, digestive, or circulatory systems. Instead, they rely on maintaining a constant water flow through their bodies to obtain food, oxygen, and to remove waste. This is usually achieved through flagella movements of the "collar cells". The single-celled choanoflagellates resemble the choanocyte cells of sponges, which are used to drive their water flow systems and capture most of their food.
Sponges are believed to have been the first outgroup to branch off the evolutionary tree from the last common ancestor of all animals. Fossil evidence of primitive sponges, such as Otavia, dates back to the Tonian period, around 800 million years ago.
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Sponges are the first outgroup to branch off the evolutionary tree
Sponges are multicellular organisms that consist of jelly-like mesohyl sandwiched between two thin layers of cells. They usually have tube-like bodies full of pores and channels that allow water to circulate through them. Sponges do not have muscle cells, but they do have "myocytes", which are muscle cells that conduct signals and cause parts of the animal to contract.
Sponges are believed to be the first outgroup to branch off the evolutionary tree from the last common ancestor of all animals. Fossil evidence of primitive sponges such as Otavia dates as early as the Tonian period, around 800 million years ago. This evidence, along with phylogenetic studies of ribosomal molecules, has been used as morphological support for sponges being the sister group to the rest of the animals. The branch of zoology that studies sponges is called spongiology.
The idea that sponges were the first to branch off from the evolutionary tree was the subject of a 2017 debate. The discussion centred around whether sponges or comb jellies (marine invertebrates) were the first to branch off. The debate was resolved with statistical analysis, which concluded that sponges came first. This analysis found that sponges are a monophyletic group and, with cnidarians, form the sister group to the bilaterians.
The internal relationships within the sponge phylum (Porifera) have been less uncertain. A close relationship between Homoscleromorpha and Calcarea has been observed in nearly all studies, regardless of whether they support sponge or eumetazoan monophyly.
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Frequently asked questions
No, sponges do not have muscles. However, they are capable of movement and contraction.
Sponges are multicellular organisms that consist of jelly-like mesohyl sandwiched between two thin layers of cells. They do not have complex nervous, digestive, or circulatory systems. Instead, they rely on maintaining a constant water flow through their bodies to obtain food and oxygen and to remove waste.
Sponge cells are responsible for bodily functions and the day-to-day activities that sustain life. For example, "grey cells" act as the sponge's immune system, and myocytes ("muscle cells") conduct signals and cause parts of the animal to contract.
No, sponges do not possess any structures that can be considered organs. They lack stomachs, kidneys, and brains.
Sponges usually have tube-like bodies full of pores and channels that allow water to circulate through them. Some are radially symmetrical, but most are asymmetrical, with shapes adapted for maximal efficiency of water flow through the central cavity.
