Phylum Porifera

Question 1

Explain the meaning of “Porifera” and how the structure of sponges reflects this name.

Answer 1

Porifera means pore-bearing.The body of sponges are covered with many tiny holes called ostia that facilitate water transport and filtering of nutrients.

Question 2

Describe how sponges differ from other animals in terms of symmetry and body organization.

Answer 2

1.Asymmetrical
2.Cellular level of organization (simple and basic, there are few tissues)

Question 3

Give 5 xtics of sponges

Answer 3

• sponges are sedentary(sessile), filter-feeding metazoan with a single layer of flagellated cells that drive a unidirectional current of water
• they have water intake and outlet openings connected by chambers (porocytes) lined with flagellated cells called choanocytes
• no nervous systems
• reproduce sexually or asexually
• asymmetrical
• sexual reproduction can be either gonochoristic or hermaphroditic

Question 4

Explain how sponges are able to feed despite having no nervous system or complex organs.

Answer 4

Sponges filter food particles from the water by pumping it through their bodies using specialized cells called choanocytes. Despite not having a nervous system or organs, this simple system allows them to survive.

Question 5

Describe the basic body plan of sponges, including the role of the spongocoel and osculum.

Answer 5

Sponges have a body made of two cell layers(pinacoderm and choanocytes) with a jelly-like substance (mesohyl) in between surrounding a chamber called spongocoel.

Canals run throughout the body which water flows.The canals have openings to the outside called pores.Water enters the sponge system through small holes called ostia, flows throught a body cavity called the spongocoel and leaves through a large cavity called osculum.

Question 6

pinacoderm, mesohyl, choanoderm

Describe the three layes of the sponge body

Answer 6

• the pinacoderm, single layer of flattened cells(pinacocytes), forms a skin-like layer that covers the outer surface of the sponge.
• Pinacocytes next to the subtratum secrete adhesive material that attach sponge to substratum
• pinacoderm is perforated by pores
• a short tubular cell called porocytes forms each of the pores.It controls water flow through the ostia.
• Beneath the pinacoderm, is a gelatinous matrix caleed mesohyl(mesoglea or mesonchyme).
• Mesohyl contains fibrous proteins and skeletal spicules (skeletal elements that provide support) interspersed with a variety of amoeboid cells called amoebocytes.
• amoebocytes deliver nutrients to cells.
• a single layer of cells called** choanoderm** lines internal water chambers.

Question 7

What is the function of choanocytes in sponges, and how do they contribute to feeding?

Answer 7

Choanocytes are the flagellated cells that line the inner surface of the body of sponges.They keep the water flowing through the canals in the right direction by beating their flagellum.They also trap food nutrients which the sponge then digest.

Question 8

Explain the role of the mesohyl in sponges and its importance in supporting their structure.

Answer 8

The mesohyl is the jelly-like layer between the sponge’s outer and inner layers. It contains fibrous proteins and skeletal spicules (skeletal elements that provide support) interspersed with a variety of amoeboid cells called amoebocytes.
- amoebocytes deliver nutrients to cells.
- helps support the sponge’s structure, giving it shape and flexibility.

Question 9

Compare and contrast the roles of pinacocytes and porocytes in the body wall of a sponge.

Answer 9

• pinacocytes are flattened cells that form the outer covering of the sponge.They provide mechanical support and protection form predators.
• porocytes are tubular cells that form the pores.They control water flow through the ostia

Question 10

Explain the function of amoebocytes and why they are essential to sponge survival.

Answer 10

• amoebocytes are mobile cells that deliver nutrients to the cells and help with digestion, repair and defense.They can change into different types of cells when needed, making them essential for sponge survival.

Question 11

What are sclerocytes, and how do they contribute to the skeletal structure of sponges?

Answer 11

• cells that secrete silica spicules.Spicules provide support, shape, and protection against predators.

Question 12

Discuss the types of skeletal elements found in sponges and their functions in providing support and protection.

Answer 12

Sponges have skeletons made of spicules (made of calcium carbonate or silica) or spongin fibers (a type of protein). These structures provide support, help maintain the sponge’s shape, and protect it from predators.
- the skeleton is located in the mesohyl but the spikes of the spicules may project through the pinacoderm providing a spiny, predator-repellent body surface

Question 13

mega, micro

What are the 2 categories of spicules?(basis of size)

Answer 13

1.megascleres- large spicules that form main supporting elements in spicules
2.microscleres - smaller spicules

Question 14

Explain the difference between calcareous and siliceous spicules and spongin fibres, and in which classes of sponges each is found.

Answer 14

Calcareous spicules: Made of calcium carbonate, found in sponges of the class Calcarea.
Siliceous spicules: Made of silica (glass-like), found in sponges of the class Hexactinellida
Spongin fibres ; Made of protein, found in sponges of the class Demospongiae.

Question 15

*Describe the differences between the three main types of sponge body forms: asconoid, syconoid, and leuconoid.

Answer 15

1. Asconoid Sponges:
   Structure: Asconoid sponges have the simplest and least complex structure. Their bodies are tubular or vase-like, and they consist of a large central cavity called the spongocoel. The spongocoel is lined with choanocytes (collar cells), which have flagella that drive water movement through the sponge.

Water Flow: Water enters through small openings called ostia (pores), passes directly into the spongocoel, and exits through a single large opening called the osculum. The entire spongocoel is lined with choanocytes, which filter out food particles from the water as it flows through.

Efficiency: Asconoid sponges are inefficient at filtering food because the water passes quickly through the spongocoel, and only a small portion of it contacts the choanocytes for feeding. This limited surface area reduces their filtering capability, so asconoid sponges are generally small in size.

Example: Leucosolenia is an example of an asconoid sponge.

2. Syconoid Sponges:
   Structure: Syconoid sponges are more complex than asconoids. Their body walls are folded, increasing the surface area for water filtration. The folds create internal chambers, which are lined with choanocytes. However, unlike asconoid sponges, the choanocytes do not line the entire spongocoel but are instead confined to chambers.

Water Flow: Water enters the sponge through incurrent canals, which are lined by pinacocytes (flattened outer cells). The water then flows into the chambers through small openings called prosopyles. These chambers are lined with choanocytes, which trap and filter food particles from the water. The filtered water then passes into the spongocoel and exits through the osculum.

Efficiency: Syconoid sponges are more efficient at filtering food than asconoids because the folding of the body wall creates more surface area lined with choanocytes. This means that a larger volume of water is filtered as it passes through the chambers.

Example: Scypha (or Grantia) is an example of a syconoid sponge.

3. Leuconoid Sponges:
   Structure: Leuconoid sponges are the most complex and the largest in size. Their body walls are highly folded and divided into an intricate network of radial chambers and canals. The spongocoel is either very small or completely absent in leuconoid sponges. Instead, they have flagellated chambers where choanocytes are located.

Water Flow: Water enters through dermal pores (ostia) into a system of subdermal spaces and then into incurrent canals. The incurrent canals lead to the flagellated chambers through small openings called prosopyles. Within the flagellated radial chambers, choanocytes filter food particles from the water. After passing through the chambers, the filtered water flows into excurrent canals and exits through one or more large oscula. The complexity of this canal system allows for a more controlled and efficient flow of water through the sponge’s body.

Efficiency: Leuconoid sponges are the most efficient water filters. Their complex system of flagellated chambers and canals provides a large surface area for filtering water. This efficiency allows them to process a much larger volume of water, making them well-suited for larger body sizes.

Example: Most sponges, including bath sponges (Spongia), are leuconoid.

Question 16

Describe the process of asexual reproduction in sponges and explain how fragmentation works.

Answer 16

Sponges can reproduce asexually by breaking into pieces (fragmentation). Each piece can grow into a new sponge. This often happens when parts of the sponge are broken off by water currents or predators.

Question 17

What is the significance of sexual reproduction in sponges, and how does it differ in gonochoristic and hermaphroditic species?

Answer 17

Sponges can reproduce sexually by releasing sperm and eggs into the water. Some species have separate sexes (gonochoristic), while others produce both sperm and eggs in the same individual (hermaphroditic).

Question 18

Explain the role of the larval stage in the life cycle of sponges and its ecological importance.

Answer 18

Sponge larvae are** free-swimming and help the species spread to new locations**. Once they settle, they attach to a surface and grow into adult sponges. This dispersal is important for their survival and colonization of new habitats.

Question 19

How do sponges capture and digest food without a digestive system or organs?

Answer 19

Sponges** capture food particles from the water as it flows through their bodies**. Choanocytes trap tiny food particles and pass them to other cells for digestion, which happens inside individual cells (intracellular digestion).

Question 20

Describe how water flows through the sponge’s body and how this flow is related to its feeding and waste removal.

Answer 20

Water enters through small pores (ostia), flows through chambers where food is filtered, and exits through the osculum. This constant flow helps sponges get food, oxygen, and remove waste.

Question 21

Explain the process of intracellular digestion in sponges and the role of choanocytes in this process.

Answer 21

Once food is captured by choanocytes,** it is engulfed by amoebocytes** and digested inside the cells. This is called intracellular digestion, as the food is broken down inside the cell.

Question 22

Why are sponges considered sessile animals, and how does this lifestyle affect their structure and function?

Answer 22

Sponges are sessile, meaning they are fixed in one place and do not move. Their bodies are adapted for this lifestyle, with structures designed to filter water while remaining anchored to rocks or other surfaces.

Question 23

Discuss the variety of habitats where sponges can be found and the factors that influence their distribution.

Answer 23

Sponges live in both marine (saltwater) and freshwater environments, but most are found in the ocean. Their distribution depends on factors like water temperature, depth, and the availability of surfaces to attach to.

Question 24

How does the body structure of sponges help them adapt to aquatic environments, particularly in terms of water filtration?

Answer 24

Sponges are designed to filter water efficiently. Their pores and canals allow water to flow through the body, and the choanocytes filter out food particles. This adaptation helps them thrive in various aquatic environments.

Question 25

Discuss the characteristics of the class Calcarea and its unique features compared to other sponge classes.

Answer 25

Sponges in the class Calcarea have skeletons made of calcium carbonate spicules. They are usually small and found in shallow marine waters. These sponges have simple body forms (asconoid or syconoid).

Question 26

Explain the defining features of class Hexactinellida and why its members are known as “glass sponges.”

Answer 26

Glass sponges have skeletons made of silica, giving them a glass-like appearance. They often live in deep ocean waters and have a** unique six-rayed spicule structure**.

Question 27

What distinguishes class Demospongiae from other sponge classes, and why is it the largest group of sponges?

Answer 27

Demospongiae is the largest class of sponges, and they have skeletons made of spongin fibers, silica spicules, or both. Most sponges, including bath sponges, belong to this group, and they have leuconoid body forms.

Question 28

*Describe the roles of archaeocytes and their totipotency in sponges.

Answer 28

Archaeocytes are specialized cells in sponges that can transform into any other type of cell (totipotent). They are important for digestion, reproduction, and repair within the sponge.

Question 29

What is the function of lophocytes in sponges, and how do they contribute to collagen secretion?

Answer 29

Lophocytes are highly mobile cells that** produce and secrete collagen**, a protein that helps strengthen the sponge’s structure. Collagen fibers help hold the sponge together and provide flexibility.

Question 30

Explain the importance of spongocytes and their role in secreting spongin fibers.

Answer 30

Spongocytes secrete spongin, a tough protein that forms the sponge’s flexible skeleton. Spongin fibers are common in sponges from the class Demospongiae and give them their soft texture.

Question 31

How do sponges protect themselves from predators, and what role do spicules play in this defense?

Answer 31

Sponges protect themselves with sharp spicules that can deter predators. Some sponges also produce toxins to make themselves less palatable or harmful to predators.

Question 32

Discuss the role of sponges in their ecosystems and their contribution to marine biodiversity.

Answer 32

Ecological Role of Sponges in the Ecosystem
Sponges (phylum Porifera) are vital components of aquatic ecosystems, particularly in marine environments. Their role extends far beyond being simple filter feeders, impacting the overall health, stability, and biodiversity of ecosystems. Here’s an in-depth exploration of their ecological contributions:

1. Water Filtration and Nutrient Cycling:
   Water Filtration: Sponges are among the most efficient natural water filters. By constantly pumping water through their bodies, they remove suspended particles, bacteria, plankton, and organic matter from the water. A single sponge can filter hundreds to thousands of liters of water per day. This filtration process not only clears the water but also improves its quality, benefiting other marine organisms.
   Nutrient Cycling: Sponges play a critical role in nutrient cycling by breaking down organic matter and recycling nutrients, such as nitrogen and phosphorus. Through their feeding, sponges process organic particles and convert them into simpler forms, which are then available for other organisms. This is particularly important in nutrient-poor environments like coral reefs, where sponges help maintain nutrient balance.
2. Habitat Formation:
   Structural Complexity: Sponges contribute to habitat complexity in marine ecosystems, particularly in coral reefs and deep-sea environments. Their often large and varied body forms provide shelter, hiding spots, and attachment surfaces for numerous small organisms, including crustaceans, mollusks, worms, and microorganisms.
   Biodiversity Support: By creating habitats within their porous bodies and surrounding areas, sponges enhance biodiversity. These microhabitats support a range of symbiotic and commensal organisms that rely on the sponge for food, protection, and breeding grounds. The sponge microbiome is rich in bacteria, fungi, and protists, which contribute to nutrient cycling and other ecological processes.
3. Symbiotic Relationships:
   Mutualistic Symbiosis: Sponges often host symbiotic microorganisms, such as photosynthetic algae and bacteria. In exchange for shelter, these symbionts provide sponges with nutrients, especially in nutrient-scarce environments. For example, cyanobacteria living inside some sponges photosynthesize and supply the sponge with carbohydrates, which is crucial for their survival in low-food environments.
   Chemical Interactions: Some sponges produce chemical compounds to protect themselves from predators or to compete for space on reefs. These chemicals can have antimicrobial or anti-fouling properties, which also benefit other organisms living on or near the sponge by reducing harmful bacteria or algae.
4. Coral Reef Health and Resilience:
   Ecosystem Engineers: In coral reef systems, sponges are considered ecosystem engineers. Their ability to filter large amounts of water and trap sediments helps keep the water clear, allowing sunlight to penetrate and support the photosynthetic activities of corals and algae.
   Nutrient Exchange with Corals: Some sponges engage in nutrient exchanges with corals, particularly in oligotrophic (low-nutrient) environments like tropical reefs. They help recycle dissolved organic matter (DOM) into particulate forms that can be used by corals, contributing to the overall productivity of the reef ecosystem.
   Resilience to Environmental Stress: Sponges are often more resilient than corals to environmental changes such as ocean acidification and warming. As coral reefs face stress from climate change, sponges may become more dominant, helping maintain some ecosystem functions in degraded reef environments.
5. Bioerosion:
   Erosion of Reef Structures: Some sponges, known as bioeroding sponges (e.g., Cliona species), play a role in the natural erosion of coral reefs. These sponges break down the calcium carbonate skeletons of corals, which contributes to the long-term dynamics of reef formation and degradation. While this process might seem destructive, it’s a natural part of reef ecology, helping recycle calcium carbonate and shape reef structures over time.

Question 33

What are the medical and biological significance of sponges, and how are they used in research or industry?

Answer 33

Medical and Biological Significance of Sponges
Sponges are not only ecologically important but also have significant medical and biological relevance. Their unique biology and chemical diversity have made them the focus of research in medicine, biotechnology, and evolutionary biology. Here’s a detailed exploration of their significance:

1. Source of Bioactive Compounds:
   Natural Chemical Factories: Sponges produce a vast array of chemical compounds, many of which are secondary metabolites used for defense against predators, competition for space, and protection from microbial infections. These compounds have caught the attention of researchers for their potential in drug development.
   Anticancer Compounds: Some of the most promising anticancer drugs have been derived from sponges. For example, Halichondrin B, isolated from the sponge Halichondria okadai, led to the development of Eribulin, a drug used to treat breast cancer. Similarly, the compound Discodermolide, from the deep-sea sponge Discodermia, has shown potential as an anticancer agent by inhibiting cancer cell growth.
   Antiviral and Antibacterial Properties: Several sponge-derived compounds have demonstrated antiviral activity, including compounds effective against HIV, herpes, and other viral infections. Sponges also produce antimicrobial peptides and other chemicals that could be used to combat antibiotic-resistant bacteria. For instance, Ara-A and Ara-C, derived from marine sponges, have been developed into antiviral and anticancer drugs.
2. Pharmaceutical Development:
   Pain Relief and Anti-inflammatory Drugs: Some sponge compounds are being explored for their ability to relieve pain or reduce inflammation. These could be beneficial for conditions such as arthritis, chronic pain, and other inflammatory diseases.
   Antifungal and Antimalarial Agents: Sponge-derived substances are being investigated for their antifungal and antimalarial properties. Some of these compounds have the potential to be used as treatments for fungal infections or in the fight against malaria, a major global health issue.
3. Biotechnological Applications:
   Enzyme Production: Sponges produce unique enzymes that have biotechnological applications. For example, some sponge enzymes are used in biotechnology for the development of biosensors, industrial processes, and even waste management.
   Spongin and Biomaterials: Spongin, the protein found in some sponge skeletons, is being researched for its potential in developing biomaterials, such as scaffolds for tissue engineering and regenerative medicine. These biomaterials could be used to repair damaged tissues or support the growth of new tissues in medical treatments.
4. Evolutionary Biology and Research:
   Understanding Early Animal Evolution: Sponges are among the earliest multicellular animals (metazoans) and are considered a key group for understanding the evolution of complex life forms. They provide insights into the transition from single-celled organisms to multicellular organisms and how different tissues and organs evolved.
   Genetic Studies: The simple body structure of sponges, combined with their ancient lineage, makes them an important subject for genetic and evolutionary studies. Research into sponge genomes can help scientists understand the origins of genes and genetic pathways that are essential in more complex animals, including humans.
5. Environmental Indicators:
   Bioindicators of Environmental Health: Sponges are sensitive to changes in water quality, making them useful bioindicators for monitoring environmental conditions. Sponges respond to pollution, temperature changes, and other stressors in ways that can indicate the health of marine ecosystems.
   Carbon and Nutrient Cycling: Through their feeding and waste processing, sponges influence the cycling of carbon and nutrients in marine environments. This can have implications for understanding global carbon cycles and how marine ecosystems respond to climate change.

Question 34

Amoebocytes occur in different forms.Explain the functions of all its cell types :
1.Archaeocytes
2.Spongioblast
3.Scleroblast
4.Collencyte
5.Lophocytes
6.Rhabdiferous cytes
7.Oocytes and spermatocytes
8.Sclerocytes
9.Spongocytes
10.Mycocytes

Answer 34

Amoebocytes, also known as archaeocytes, are versatile cells in sponges that play crucial roles in feeding, digestion, waste removal, reproduction, and repair. They are found within the jelly-like mesohyl of sponges and exist in different forms, each specialized for particular functions. Here are the different forms in which amoebocytes exist:

1. Archaeocytes (or Amoebocytes):
   
   • Totipotent Cells: Archaeocytes are totipotent, meaning they can transform into other types of sponge cells as needed. This ability allows them to perform a wide range of functions and respond to the needs of the sponge.
   • Role in Feeding: They are responsible for digesting food particles captured by choanocytes (collar cells). After digestion, they transport nutrients to other cells throughout the sponge body.
   • Role in Reproduction: Archaeocytes are involved in the formation of reproductive cells, such as sperm and eggs, during sexual reproduction.
2. Scleroblast:
   - Function: Sclerocytes are responsible for producing the spicules, which are the structural elements of the sponge’s skeleton. These spicules can be made of silica or calcium carbonate, depending on the type of sponge.
   - Role in Defense: Spicules also serve a defensive purpose by making the sponge less palatable or harder to consume by predators.
3. Spongioblast:
   - Function: Spongocytes secrete spongin, a fibrous protein that forms the flexible framework of many sponges, particularly in the class Demospongiae.
   - Role in Support: The spongin fibers provide structural support and elasticity to the sponge body, giving it resilience and flexibility.
4. Collencytes:
   
   • Function: Collencytes are star-shaped cells that secrete collagen, a fibrous protein that contributes to the sponge’s mesohyl structure. Collagen helps maintain the integrity and strength of the sponge body.
   • Role in Structural Support: These cells help create a strong but flexible scaffold that supports the sponge’s overall structure.
5. Lophocytes:
   - Function: Lophocytes are highly mobile cells that also secrete collagen, but they are considered more active and involved in rapid collagen production and repair.
   - Role in Repair and Maintenance: Due to their mobility, lophocytes can move around the sponge body to areas that require reinforcement or repair, producing collagen as needed.
6. Oocytes and Spermatocytes:
   - Function: These are the reproductive cells in sponges. Oocytes develop into eggs, while spermatocytes develop into sperm. Both types of cells arise from amoebocytes during sexual reproduction.
   - Role in Reproduction: These cells are vital for sexual reproduction in sponges, helping to produce the next generation.
7. Rhabdiferous Cells:
   
   • Function: Rhabdiferous cells secrete polysaccharides, which contribute to the formation of the sponge’s mesohyl. These polysaccharides add to the matrix’s gel-like consistency.
   • Role in Supporting the Mesohyl: The secreted polysaccharides provide structural support and help in the transport of materials within the mesohyl.
8. Myocytes:
   - Function: Myocytes are contractile cells that can contract and control the opening and closing of pores and canals in the sponge’s body.
   - Role in Water Flow Regulation: By controlling the size of the sponge’s oscula (large openings) and ostia (small pores), myocytes help regulate water flow through the sponge, ensuring efficient feeding and waste removal.

9.Spongocytes
- secrete a form of collagen that polymerizes into spongin that stiffens the mesohyl.
10.Sclerocytes
- secrete mineralized spicules.

Their versatility and specialization enable sponges to survive and thrive in diverse aquatic environments.