28.1 Phylum Porifera
3 min read•june 14, 2024
, the simplest animals, are filter-feeding aquatic creatures with unique body structures. They lack true tissues and organs, instead relying on specialized cells and a water current system for survival. Their simple yet effective design has allowed them to thrive for millions of years.
Sponges' bodies consist of outer and inner layers with a jelly-like middle. They feed by filtering water through tiny pores, trapping food particles with specialized cells. Sponges can reproduce both sexually and asexually, and their cells can transform into any type needed.
Phylum Porifera
Structure and function of sponges
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- , , aquatic invertebrates lack true tissues and organs (sponges)
- Body structure consists of an outer layer (), inner layer () composed of , and a gelatinous matrix between layers called the
- Mesohyl contains and skeletal elements such as or that provide support and structure
- Water current system allows water to enter through small openings called , flow through the sponge body, and exit through a large opening called the
- Water flow maintained by flagellated cells called choanocytes that create currents to bring in food and oxygen while removing waste
- The is the central cavity of the sponge where water collects before exiting through the osculum
Feeding and digestion in sponges
- trap and consume food particles from the water that flows through their bodies
- Choanocytes, flagellated cells lining the inner chambers, create water currents to bring in food and trap and food particles
- Amoebocytes, mobile cells within the mesohyl, transport and digest nutrients intracellularly and distribute them throughout the sponge body
- No specialized digestive system as digestion occurs within individual cells ()
Cell types and roles in sponges
- are flattened cells that cover the outer surface providing protection and support (skin cells)
- Choanocytes (collar cells) are flagellated cells lining the inner chambers that create water currents for filter feeding and trap and phagocytize food particles
- Amoebocytes () are mobile cells within the mesohyl that perform various functions:
- Transport and digest nutrients
- Produce skeletal elements such as spicules or spongin fibers
- Differentiate into other specialized cell types as needed
- are tubular cells that form the ostia and control water flow into the sponge
- secrete spicules, which are siliceous or calcareous skeletal elements that provide structural support ()
- Spongocytes secrete spongin fibers, which are flexible protein fibers that form the skeleton in some sponges ()
Reproduction and development in sponges
- Sponges can reproduce both sexually and asexually
- occurs through:
- Budding: small outgrowths develop and detach from the parent sponge
- Fragmentation: pieces of the sponge break off and regenerate into new individuals
- involves:
- Production of gametes by specialized cells
- External fertilization in the water column
- Development of a free-swimming larva that eventually settles and metamorphoses into an adult sponge
- Sponge cells exhibit , allowing them to differentiate into any cell type needed for regeneration or reproduction
Body plan and organization
- Sponges have a simple with no true tissues or organs
- Three main types of body plans in sponges:
- Asconoid: simplest form with a single central cavity (spongocoel)
- Syconoid: more complex with folded inner walls and a central cavity
- Leuconoid: most complex with a system of canals and chambers
Key Terms to Review (30)
Amoebocytes: Amoebocytes are specialized cells found in sponges (Phylum Porifera) that play multiple roles in the organism's biology. These versatile cells are crucial for transporting nutrients, waste removal, and providing structural support within the sponge. Their ability to move through the mesohyl, the gelatinous matrix in which sponge cells reside, allows them to perform essential functions that contribute to the overall homeostasis of the sponge.
Archaeocytes: Archaeocytes are specialized cells found in sponges that play a crucial role in various physiological processes, including digestion, repair, and reproduction. These versatile cells are capable of transforming into other cell types, allowing them to contribute to the sponge's cellular organization and overall function. Archaeocytes serve as the main form of totipotent stem cells in sponges, demonstrating their importance in maintaining the sponge's homeostasis and responding to environmental changes.
Asexual reproduction: Asexual reproduction is a mode of reproduction where offspring are produced by a single parent without the involvement of gamete fusion. This process results in offspring that are genetically identical to the parent.
Asexual reproduction: Asexual reproduction is a mode of reproduction that involves a single organism producing offspring without the involvement of gametes or fertilization. This process allows organisms to rapidly produce genetically identical offspring, which can be beneficial in stable environments where adaptation to changing conditions is not immediately necessary.
Asymmetrical: Asymmetrical refers to a lack of symmetry or balance in the structure or form of an organism. In the context of certain organisms, this means that their body shape or arrangement of parts does not conform to a standard or mirror image on either side. This characteristic is particularly significant in understanding how certain organisms interact with their environment, as well as their evolutionary adaptations.
Bath Sponges: Bath sponges are marine organisms that belong to the Phylum Porifera, commonly known for their porous bodies and ability to filter water. These simple creatures are made up of specialized cells and a skeleton of spongin or silica, which gives them their characteristic texture and structure. Bath sponges are an important part of marine ecosystems, contributing to water filtration and serving as habitats for various marine life.
Body plan: A body plan refers to the general structural organization of an organism, including its shape, size, and the arrangement of its organs and systems. This concept is crucial for understanding how different animal species are classified based on their evolutionary relationships and morphological characteristics. Body plans can reveal a lot about an organism's lifestyle, habitat, and evolutionary adaptations.
Choanocytes: Choanocytes are specialized cells found in sponges, belonging to the Phylum Porifera, that play a crucial role in the sponge's feeding and water filtration processes. These cells have a unique structure featuring a flagellum surrounded by a collar of microvilli, which aids in capturing food particles from the water as it flows through the sponge's body. By creating water currents and filtering nutrients, choanocytes are essential for the survival and functioning of sponges.
Choanoderm: The choanoderm is the innermost layer of cells in sponges, specifically composed of specialized cells called choanocytes. These cells play a crucial role in the feeding mechanism of sponges, as they possess flagella that create water currents, allowing for the filtration of food particles from the water. The choanoderm is vital not only for nutrient acquisition but also for gas exchange and waste removal in these simple aquatic organisms.
Filter feeders: Filter feeders are organisms that obtain their food by straining suspended matter and food particles from water, using specialized structures. This feeding strategy is essential for many aquatic animals, allowing them to thrive in environments where nutrients are often scarce. In the context of marine ecosystems, filter feeders play a crucial role in maintaining water quality and cycling nutrients.
Gemmules: Gemmules are asexual reproductive structures produced by certain sponges. They are composed of a group of archaeocytes surrounded by a protective coat made of spicules and spongin.
Glass sponges: Glass sponges are a unique group of sponges characterized by their silica-based skeletons, giving them a glassy appearance. These organisms belong to the class Hexactinellida within the Phylum Porifera and are known for their intricate, often beautiful structures that can form large colonies in deep-sea environments.
Intracellular digestion: Intracellular digestion is a process where organisms break down food particles within their cells, allowing for the absorption of nutrients directly. This method is a key feature of certain simple organisms, particularly sponges, which lack complex digestive systems. By utilizing specialized cells to engulf and digest food, these organisms efficiently convert nutrients into forms they can use for energy and growth.
Mesohyl: Mesohyl is a gelatinous matrix found between the outer layer of cells and the inner layer of cells in sponges, specifically within Phylum Porifera. This supportive structure is crucial for the sponge's overall function, serving as a medium for nutrient transport, structural support, and housing various cells that contribute to the sponge's filter-feeding capabilities.
Monoecious: Monoecious organisms have both male and female reproductive structures on the same individual. This term is commonly used in botany and zoology to describe certain plant species and invertebrates.
Osculum: An osculum is a large opening in a sponge that serves as an outlet for water to flow out after it has been filtered for nutrients. This structure is crucial for the sponge's feeding process, as it allows the expelled water to carry away waste products and excess water, facilitating the sponge's unique method of respiration and circulation.
Ostia: Ostia are small openings found on the surface of sponges, which allow water to flow into their porous bodies. These openings play a vital role in the feeding, respiration, and excretion processes of sponges, as they enable the organism to filter food particles and oxygen from the surrounding water.
Phagocytize: Phagocytize refers to the process by which certain cells, known as phagocytes, engulf and digest foreign particles, bacteria, or dead cellular debris. This process is crucial for the immune system, helping to protect organisms from infections and maintain tissue health. In the context of Porifera, this ability allows sponges to filter feed and obtain nutrients from their environment, showcasing a primitive form of immune response and nutrient acquisition.
Pinacocytes: Pinacocytes are specialized flat cells that form the outer layer of sponges, contributing to the structure and function of the sponge's body. These cells play a crucial role in protecting the sponge and regulating water flow through its porous body, as they line the oscula and other openings. Pinacocytes also help maintain the shape of the sponge and can respond to environmental changes.
Pinacoderm: The pinacoderm is the outermost layer of cells that forms the protective covering of sponges, belonging to the Phylum Porifera. This layer consists of flattened cells called pinacocytes, which help maintain the sponge's structure and regulate water flow. The pinacoderm plays a crucial role in protecting the internal cavity and contributes to the overall functionality of the sponge's body plan.
Porifera: Porifera, commonly known as sponges, is a phylum of simple, multicellular animals characterized by a porous body structure and a lack of true tissues and organs. They are primarily aquatic organisms that play a crucial role in marine and freshwater ecosystems, acting as filter feeders and contributing to nutrient cycling.
Porocytes: Porocytes are specialized cells found in the body of sponges (Phylum Porifera) that form the pores, or ostia, through which water enters the sponge. These cells play a crucial role in the sponge's filter-feeding mechanism, allowing water to flow through the sponge's body and enabling it to obtain nutrients while removing waste products. Porocytes are essential for maintaining the internal water flow that is vital for the sponge's survival and functioning.
Sclerocytes: Sclerocytes are specialized cells found in the phylum Porifera, responsible for the production of structural components called spicules. These spicules provide support and protection to sponges, which are simple aquatic animals that lack true tissues and organs. Sclerocytes play a crucial role in the overall structure and function of sponges, contributing to their unique morphology and aiding in their ability to filter feed.
Sessile: The term 'sessile' refers to organisms that are permanently attached to a substrate and do not move freely. In the context of certain aquatic organisms, particularly in Phylum Porifera, being sessile means that sponges are anchored to the ocean floor or other surfaces, relying on water currents to bring food and oxygen to them. This lifestyle impacts their morphology and feeding strategies significantly.
Sexual reproduction: Sexual reproduction is a biological process that involves the combination of genetic material from two parent organisms to produce offspring with genetic variation. This process is significant as it allows for greater adaptability and evolution within a species, providing advantages in changing environments.
Spicules: Spicules are small, needle-like structures found in the skeletons of many sponges, specifically within the Phylum Porifera. These structures are made of silica or calcium carbonate and provide support and protection to the sponge's body. Spicules come in various shapes and sizes, contributing to the diversity among sponge species and their ability to adapt to different aquatic environments.
Sponges: Sponges are simple, multicellular organisms belonging to the phylum Porifera, characterized by their porous bodies and lack of true tissues or organs. They play a crucial role in aquatic ecosystems, acting as filter feeders that help maintain water clarity and quality while providing habitat for various marine life.
Spongin fibers: Spongin fibers are a type of structural protein found in the skeleton of some sponges, specifically within the Phylum Porifera. These fibers provide support and flexibility to the sponge body, allowing it to maintain its shape while also facilitating the flow of water through its porous structure. Spongin is primarily composed of collagen and is crucial for the overall function and resilience of certain sponge species.
Spongocoel: The spongocoel is a central cavity found within the bodies of sponges, belonging to the Phylum Porifera. This cavity plays a crucial role in the sponge's feeding and water filtration system, allowing water to flow through and facilitating the exchange of nutrients and waste. The spongocoel is lined with specialized cells called choanocytes, which aid in capturing food particles and creating a current to draw water into the sponge.
Totipotency: Totipotency is the ability of a single cell to develop into an entire organism, including all of its cell types. This unique characteristic allows certain cells to not only give rise to all the specialized cells in an organism but also to generate the extra-embryonic tissues necessary for development. In the context of specific organisms, totipotent cells can play crucial roles in regeneration and repair processes.