Sponge Anatomy and Ecology

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Questions and Answers

What is the primary method by which sponges capture the smallest food particles?

Diffusion

Endocytosis

Phagocytosis (correct)

Osmosis

Which sponge body type has the simplest organization with choanocytes located in a single internal chamber?

Asconoid (correct)

Leuconoid

Calcispongiae

Syconoid

How do syconoid sponges differ from asconoid sponges in their structure?

Syconoids are smaller and less complex.

Syconoids have thickened walls with radial canals. (correct)

Syconoids have no spongocoel.

Syconoids lack dermal ostia.

Which of the following statements accurately describes the leuconoid sponge body structure?

It features multiple food-collecting regions lining small chambers. Signup and view all the answers

What is the primary role of choanocytes in sponges?

To generate water flow and capture food particles. Signup and view all the answers

What process allows sponges to take in liquid nutrients?

Pinocytosis Signup and view all the answers

Which term describes the opening through which water is expelled from an asconoid sponge?

Osculum Signup and view all the answers

What is the primary function of archaeocytes in sponges?

They facilitate food processing and transport. Signup and view all the answers

What factors influence the growth patterns of sponges?

Species diversity in the habitat and speed of flow Signup and view all the answers

Which of the following statements about sponge interactions is true?

Certain species use sponges for camouflage. Signup and view all the answers

Which statement accurately describes the skeletal structure of sponges?

Sponges can be classified based on spicule composition and shape. Signup and view all the answers

Which class of sponges is characterized by calcium carbonate spicules?

Calcispongiae Signup and view all the answers

What primary role do choanocytes play in sponge feeding?

They generate water currents and capture food particles. Signup and view all the answers

What is the primary composition of siliceous spicules found in sponges?

Silica Signup and view all the answers

Which type of sponges have spicules with six rays?

Hexactinellida Signup and view all the answers

What feature distinguishes Homoscleromorpha sponges from other classes?

Absence of spicules entirely Signup and view all the answers

What is the primary function of the excurrent canals in sponges?

To discharge used water and waste Signup and view all the answers

Which type of sponge system has evolved independently many times?

Leuconoid system Signup and view all the answers

How do sponges manage respiration and excretion?

By diffusion at the cellular level Signup and view all the answers

What is the role of collar cells in the sponge body?

To increase water flow and filter particles Signup and view all the answers

What mechanism allows sponges to respond to environmental factors such as heavy sediment load?

Closing of the osculum Signup and view all the answers

What is the significance of the gelatinous extracellular matrix in sponges?

It provides a medium for cellular processes Signup and view all the answers

What is the primary advantage of a leuconoid sponge's structure?

Increased proportion of flagellated surface Signup and view all the answers

How do mechanical stimuli affect sponge activity?

They trigger electrical impulses or signaling molecules Signup and view all the answers

What is the function of the collar of choanocytes?

To filter and strain food particles Signup and view all the answers

Which process allows sponges to regenerate lost parts?

Fragmentation Signup and view all the answers

What type of cells are archaeocytes?

Amoeboid cells with versatile functions Signup and view all the answers

Which of the following types of cells secrete spicules in sponges?

Sclerocytes Signup and view all the answers

What are gemmules?

Small internal buds that can survive harsh conditions Signup and view all the answers

How do pinacocytes regulate the surface area of the sponge?

By contracting Signup and view all the answers

What is the primary mechanism through which food is processed in sponges?

Intracellular digestion within choanocytes Signup and view all the answers

What features are found in the pinacoderm of sponges?

Various intercellular junctions but no basal membrane Signup and view all the answers

What is the main function of micropyles in gemmules?

To allow live cells to escape and develop into new sponges Signup and view all the answers

Which statement accurately describes the nature of most sponges regarding reproduction?

Most sponges are monoecious, having both male and female sex cells. Signup and view all the answers

In viviparous sponges, what is the fate of the zygote after fertilization?

It is retained within the parent sponge and nourished until released. Signup and view all the answers

What is the main characteristic of oviparous sponges?

They release both sperm and oocytes into the water for external fertilization. Signup and view all the answers

What developmental pattern is unique to Calcispongiae and some Demospongiae?

Hollow stomoblastula develops with flagellated cells oriented toward the interior. Signup and view all the answers

During which stage does the inversion of the blastula occur in sponges?

When developing from stomoblastula to parenchymula Signup and view all the answers

What are choanocytes derived from in sponges?

Choanocytes or archaeocytes Signup and view all the answers

What provides the basis for the differences in developmental patterns in sponges?

The environmental conditions and habitat Signup and view all the answers

Study Notes

Sponge Growth and Interactions

Sponge growth patterns are influenced by the shape of the substratum, water direction, flow speed, and available space.
Sponges can often be found growing on other living organisms, including crabs, nudibranchs, and fish.
Some crabs use sponges for camouflage and protection.
Sponges and associated microorganisms often have a noxious odor and produce bioactive compounds that are being investigated for medical and pharmaceutical purposes.

Sponge Skeletal Structure

Sponges have a skeletal structure that can be fibrous and/or rigid, comprised of calcareous or siliceous spicules.
The fibrous portion is created by collagen protein fibrils in the intercellular matrix.
Sponges contain a specific type of collagen called spongin.
The composition and shape of spicules are used for classification.

Spicule Forms

Spicules come in diverse forms, including:
- Monaxons: single-pointed spicules
- Triaxons: three-pointed spicules
- Tetraxons: four-pointed spicules
- Hexaxons: six-pointed spicules

Poriferan Classification

Sponges date back to the early Cambrian period, and potentially even the Precambrian.
They are traditionally classified into three classes based on their spicules and chemical composition:
- Calcispongiae: have calcium carbonate spicules with one, three, or four rays.
- Hexactinellida: glass sponges with six-rayed siliceous spicules.
- Demospongiae: have siliceous spicules around an axial filament, spongin fibers, or both.
A fourth class, Homoscleromorpha, was later identified as sponges without a skeleton, or with siliceous spicules without an axial filament.

Feeding in Sponges

Sponges feed by filtering suspended particles from water pumped through their internal canal systems.
Water enters through numerous small incurrent pores (dermal ostia) in the outer cell layer (pinacoderm).
Choanocytes, flagellated collar cells, create currents that move water past them via the beating of their flagella.
Microvilli on the collar trap food particles, which are then phagocytized.
The efficiency of food capture depends on the movement of water through the sponge body.

Sponge Food

Sponges are non-selective feeders, consuming detritus, plankton, and bacteria.
The smallest particles (80%) are taken into choanocytes by phagocytosis.
Protein molecules can be absorbed by pinocytosis.
Pinacocytes and archaeocytes also contribute to feeding.
Dissolved nutrients can be absorbed by sponges.

Sponge Body Structures

Sponges have three main body structures:
- Asconoid: The simplest body type; small and tube-shaped, allowing water to flow directly across cells.
- Syconoid: Resembles asconoids, but has a thicker body wall with radial canals lined with choanocytes.
- Leuconoid: The most complex and largest, with a series of chambers lined with choanocytes.

Asconoid Sponge Body

The simplest body organization in sponges.
Small and tube-shaped to allow water to flow directly across cells without “dead space.”
Choanocytes in a large internal chamber, the spongocoel.
Water is drawn in through the pores and food particles are extracted by the choanocyte flagella.
Used water is expelled through a large single osculum.
All asconoid sponges belong to the class Calcispongiae, examples include Leucosolenia sp. and Clathrina sp.

Syconoid Sponge Body

Resembles asconoids, but larger with a thicker and more complex body wall.
Body wall folds outwards with choanocyte-lined radial canals that empty into the spongocoel.
Water enters through dermal ostia, moves through tiny openings (prosopyles) into the radial canals, and is then pumped through internal pores called apopyles to exit the osculum.
The spongocoel is lined with epithelial cells, not choanocytes like in asconoids.

Leuconoid Sponge Body

The most complex and largest sponge body type, with more food-collecting regions.
Choanocytes line small chambers within the sponge, allowing for efficient filtration of all water.
Clusters of flagellated chambers are filled by incurrent canals and discharge to excurrent canals that lead to the osculum.
Used water is pooled, forming an exit stream that is expelled through a pore at high velocity, preventing re-filtering of used water and waste products.
Most sponges are of the leuconoid type.

Leuconoid Evolution and Distribution

The leuconoid system provides an adaptive advantage for efficiently meeting the high food demands of a larger body size.
It has a higher proportion of flagellated surface per volume of cell tissue, allowing more collar cells to filter more particles.
Water flow slows inside due to the greater surface area in the chambers, allowing more time for filtering.
Large sponges can filter up to 1500 liters of water per day for maximum food collection.
The leuconoid system has evolved independently many times in sponges.

Sponge Cells

Sponge cells are arranged in a gelatinous extracellular matrix called mesohyl or mesenchyme, acting as a connective “tissue” within the sponge.
All fundamental processes occur at the individual cell level due to the absence of organs.
Respiration and excretion occur via diffusion.
Water regulation is achieved through contractile vacuoles in the archaeocytes and choanocytes.

Sponge Activity and Response

Sponge activities include slight alterations in shape, local contraction, and propagating contractions.
Sponges can close their osculum to prevent entry of heavy sediment loads.
Sponge movements are slow, but they suggest a whole body response in organisms lacking complex organizational structures above he cell level.
Excitations appear to spread from cell to cell by mechanical stimuli, signaling molecules (hormones), and electrical impulses.

Types of Sponge Cells

Choanocytes: One end is embedded in the mesohyl, the exposed end has a flagellum surrounded by a collar. They trap and phagocytize food particles too large to enter the collar.
Archaeocytes: Amoeboid cells with multiple functions, travelling through the mesohyl. Phagocytize particles in the pinacoderm, receive digested particles from choanocytes, and can differentiate into various specialized cells, including sclerocytes, spongocytes, collencytes, and lophocytes.
Pinacocytes: Thin, flat, epithelial-like cells covering the exterior and interior surfaces of sponges. Form the pinacoderm with various intercellular junctions. Ingest food by phagocytosis and are contractile to regulate the surface area of the sponge. Form myocytes that regulate water flow.

Regeneration and Asexual Reproduction

Sponges possess remarkable regenerative abilities, allowing them to repair injuries and regenerate lost parts.
Regeneration following fragmentation is a common means of asexual reproduction.
Asexual reproduction methods include:
- Fragmentation: A sponge breaks into parts that can each grow into a new sponge.
- Bud formation: External buds detach from the parent when it reaches a certain size, or internal buds (gemmules) are formed by archaeocytes in the mesohyl. Gemmules are coated in tough spongin and spicules, allowing them to survive harsh conditions.

Gemmulation

Gemmules are dormant survival structures that can withstand harsh conditions.
When the parent sponge dies, the gemmules can remain dormant and survive until favorable conditions return.
Living cells within gemmules escape through a special opening called a micropyle and develop into new sponges.
Gemmulation is an adaptation to changing seasons and allows for colonization of new habitats.
Gemmule formation can be influenced by climate, internal chemicals, and their location within the parent sponge.

Sexual Reproduction

Most sponges are monoecious (both male and female sex cells within one body).
Gametes develop from choanocytes or archaeocytes.
Most sponges are viviparous (live birth); the zygote is retained in the parent for nourishment until it is released as a ciliated larva.
One sponge releases sperm that enters the pores of another sponge.
Choanocytes phagocytize the sperm, transport it through the mesohyl, and eventually to oocytes to form zygotes.

Poriferan Larvae

Some sponges are oviparous, releasing both sperm and oocytes into the water for external fertilization.
The free-swimming larva of most sponges is a solid-bodied parenchymula larva.
Six other larval forms also exist.
The outward-directed flagellated cells of the parenchymula become choanocytes.

Unique Developmental Pattern

Found in Calcispongiae and some Demospongiae.
A hollow stomoblastula develops with flagellated cells oriented towards the interior.
The blastula turns inside out (inversion), bringing the flagellated cells to the exterior.
Small flagellated cells (micromeres) are located at the anterior end, while larger non-flagellated macromeres are at the posterior end.
Macromeres overgrow the invaginating micromeres during metamorphosis and settlement.
Micromeres become choanocytes, archaeocytes, and collencytes, while macromeres give rise to the pinacoderm and sclerocytes.

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Description

Explore the fascinating growth patterns and skeletal structures of sponges. This quiz delves into the interactions between sponges and their environments, including their use by other organisms and the significance of spicule forms. Test your knowledge on the biological and ecological aspects of sponges.