ZOO 101_Porifera_cnidaria

Page 1: Introduction to Porifera, Cnidaria and Ctenophora

Page 2: Porifera

Page 3: Introduction to Porifera

Etymology

• The term "Porifera" is derived from the Latin

  • "porus" meaning pore, and

  • "ferre" meaning to bear, indicating an organism with pores.

General Characteristics

• Commonly known as sponges.

• Mistaken for plants at first, but they are indeed animals.

• Primarily found in marine environments, mostly in shallow waters.

• Sessile organisms that attach to substrates, sometimes on animals like crabs.

• Classified as the most primitive metazoans, lacking true tissues or organs.

• Multicellular with a structure filled with pores and channels that allow water circulation, with a jelly-like mesoglea between two thin cellular layers.

Page 4: Characteristics of Porifera

1. Lack of definite symmetry.

2. Multicellular structure with limited tissue organization; no true organs.

3. Water-filled space surrounded by cells and tissues; no true body cavity.

4. All members are sessile as adults.

5. Reproduction can be sexual (gonochoristic or hermaphroditic) or asexual.

6. Absence of a nervous system.

7. Distinct larval stage that is planktonic.

8. Habitat: aquatic environments, primarily marine.

9. Feeding: all are filter feeders.

10. Skeleton typically made of spicules.

Page 5: Phylum Porifera (Pore-bearer)

Characteristics

• Generally exhibit asymmetry or sometimes radial symmetry.

• Lack true tissues, organs, or muscles.

• Filter feeding mechanism: water enters through pores to a central body cavity and exits via the osculum.

• Skeleton can consist of needle-like spicules of silicon salts or calcium carbonate, or a pliable structure made of organic fibers (spongin/collagen).

Page 6: Cellular Organization of Porifera

• Classified under Metazoa.

• No true tissues or body systems; minimal cell coordination.

• Layers of cells do not form basement membranes.

• Adults are mostly asymmetrical, sometimes superficially radially symmetrical.

• Presence of totipotent cells akin to stem cells.

• Choanocytes (collar cells) create water flow through canals (aquiferous system).

• Larvae are typically motile and lecithotrophic (non-feeding, high yolk supply).

• Mesohyle is the middle layer, housing motile cells and skeletal materials like spicules and spongin.

Page 7: Cellular Types in Sponges

• Pinacocytes: Outermost cells; akin to epidermal cells.

• Choanocytes: Collar cells resembling choanoflagellates; flagella generate water currents and trap food.

• Amoebocytes: Amoeba-like cells; involved in food storage, digestion, transport, waste excretion, secreting skeletons, and asexual reproduction.

Page 8: Overview of Sponge Cells

Three main cell types:

1. Pinacocytes: Line the outer surface; may have contractile abilities.

2. Mesenchyme cells: Amoeboid cells moving within the mesohyl; involved in reproduction, secretion of skeletal elements, food transportation, and forming contractile rings around pores.

3. Choanocytes: Flagellated cells creating water currents and filtering food via phagocytosis.

Page 9: Anatomy of Sponges

• Diagrams illustrating:

  • Porocyte (water flow).

  • Amoebocyte.

  • Pinacocyte.

  • Spicules.

  • Choanocyte.

Page 10: Maintenance Functions in Sponges

Functions

• Digestion: Occurs intracellularly in food vacuoles/lysosomes.

• Excretion: Nitrogenous waste via diffusion.

• Respiration: O2 and CO2 exchange by diffusion.

• Endocrine system: Chemical communication among cells.

• Sexual reproduction: Monoecious, eggs and sperm produced at different times; zygotes develop into swimming larvae.

Page 11: Asexual Reproduction in Sponges

Methods

• Gemmules: Formed under stress; resistant capsules with amoeba-like cells in mesohyl.

• Regeneration: A process of internal budding creating clones of the parent sponge.

Page 12: Types of Sponge Anatomy

Morphology Based on Water Currents

1. Asconoid Sponges: Simplest; water flows through ostia to spongocoel and exits via a single osculum.

2. Syconoid Sponges: Water enters through ostia, passes through incurrent canals, radial canals, then to spongocoel and exits via osculum.

3. Leuconoid Sponges: Complex structure with branched canals, water moves through ostia, incurrent canals, excurrent canals to smaller spongocoels and exits through multiple oscula.

Page 13: Sexual Reproduction in Sponges

Process

• Gametes derived from amoebocytes; species can be hermaphroditic or dioecious.

• Hermaphrodites produce gametes at different intervals to prevent self-fertilization.

• Sperm released via osculum enters another sponge through ostia; fertilization occurs in the sponge.

• Zygote expelled and develops into a larva.

Page 14: Asexual Reproduction in Sponges

Two Types

1. Budding: Body wall fragmentation; buds develop, detach, and settle as new sponges.

2. Gemmules: Formed by freshwater sponges under unfavorable conditions; allow sponges to survive adverse climates.

Page 15: Structure of a Gemmule

• Illustrates structure:

  • Micropyle (opening).

  • Inner membrane.

  • Archaeocytes.

  • Spicules.

Page 16: Sponge Classification

Page 17: Class Calcarea

Characteristics

• Composed of calcium carbonate spicules; monaxons, tri-, or quadraxons.

• Size typically less than 10 cm; commonly found in shallow coastal waters.

• Example species: Leucosolenia, Grantia; all marine.

Page 18: Class Hexactinellida (Glass Sponges)

Features

• Made of silica; spicules fused for support.

• Structurally shaped like a cup or vase, with well-formed spongocoel.

• Beautiful example: Euplectella (Venus flower basket).

• Found at depths of 500-1000 meters; these are all marine species.

• They can have commensal relationships with shrimp (male and female can get trapped inside).

Page 19: Class Demospongiae

Overview

• Largest class, accounting for 95% of sponges.

• Spicules siliceous or made of spongin; exhibit diverse shapes, many very large.

• Almost all are leuconoid; all but one family (Spongillidae) is marine.

• Six species are commercially marketable; their skeletons consist solely of spongin.

• Mediterranean, Red Sea, and West Indian species have varying quality and durability in commercial sponges.

Page 20: Natural Bath Sponge

• Description: The skeleton of a primitive marine sponge.

• Composed of silica, calcium carbonate, spongin, or a combination.

Page 21: Class Sclerospongiae

• Proposed in 1970 for six species from Jamaica.

• Feature siliceous spicules and spongin, with an outer calcium carbonate layer.

• Structured as leuconoid sponges.

Page 22: Economic Importance of Sponges

Uses & Benefits

• Play roles in marine ecosystems offering habitats.

• Some contain chemicals useful for medical purposes (cancer treatment, HIV).

• Important for filtering contaminants, contributing to coral reef structures.

• Ancient use: Fibrous skeletons for washing and mopping due to their capacity to retain water.

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Page 24: Ecological Roles of Sponges

Mutualism & Commensalism

• Provide habitat for various organisms, often full of commensal species.

• Sponges, snails, crabs all find protection from larger predators amongst sponge structures.

• Example: Large sponges can harbor thousands of shrimp or diverse organisms.

• Decorative usage in some cultures, like the Venus flower basket, which harbors bundled shrimp.

Page 25: Sponges and Humans

Concerns & Importance

• Medical uses aside, sponge farming practices face overharvesting in numerous regions.

• Population declines linked to diseases and environmental factors.

Page 26: Phylum Cnidaria

Introduction

• Cnidarians are multicellular, tissue-forming animals including sea anemones, jellyfish, and corals.

• Exhibit radial symmetry, a trait evolved specifically in cnidarians.

• Name derived from cnidocytes, which are the specialized stinging cells.

Page 27: Characteristics of Cnidarians

General Features

• Exhibit radial or biradial symmetry.

• Diploblastic with two tissue layers: endoderm and ectoderm, with mesoglea.

• Possess a gastrovascular cavity (GVC) for digestion and movement.

• Contain a nerve net for sensory capabilities; possess cnidocytes armed with nematocysts.

Page 28: Feeding Structure of Cnidarians

• Centrally-located mouth surrounded by tentacles used for food capture.

• Stinging cells (nematocysts) deliver neurotoxins for prey immobilization; exhibit various types.

• GVC opens to the gut, which has a single opening for both intake and waste expulsion.

Page 29: (Link to video on nematocysts)

Page 30: Maintenance Functions in Cnidarians

Functions

• Digestion: Initiates in GVC, completed in food vacuoles; no anus.

• Excretion: Exchange of nitrogenous waste via GVC diffusion.

• Respiration: O2/CO2 diffusion through GVC.

• Reproduction: GVC aids in gamete release.

• Skeletal Movements: Supported by hydrostatic skeleton.

Page 31: Muscular and Reproductive Systems

• Muscular System: Contraction of epitheliomuscular cells aids in movement.

• Reproduction: Exhibits alternation of generations with distinct body forms.

Page 32: Forms of Cnidarians

Two Major Forms

• Polyp: Asexual, sessile; cylindrical shape with a mouth on top.

• Medusa: Free-swimming, dioecious; releases gametes for external fertilization.

Page 33: Medusa Reproduction

• Medusa is dioecious (two sexes); capable of sexual reproduction by releasing gametes into water.

• Results in planula larva that eventually grows into a new polyp generation.

Page 34: Classification of Cnidarians

1. Class Hydrozoa: Includes species like Obelia and Hydra.

2. Class Scyphozoa: True jellyfish such as Aurelia.

3. Class Cubozoa: Cube-shaped medusa, e.g. Sea Wasp.

4. Class Anthozoa: Sea anemones, corals.

Page 35: Class Hydrozoa

• Comprises small, predatory Cnidarians, can be solitary or colonial.

• Contains specialized colonies (Siphonophores) for distinct functions with tentacles and digestive cells.

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Page 37: Class Scyphozoa

Characteristics

• Includes most common jellyfish.

• Display a short polyp stage and predominantly a long medusa stage.

• Swimming is limited, causing painful stings.

Page 38: Class SCYPHOZOA

• The Scyphozoans (class Scyphozoa) include most of the common medusa-like 'jellyfish'

Larger than Hydrozoans

Short polyp age; Long medusa-stage

Scyphozoan polyps are very small and release juvenile medusa

Adult medusa have a rounded body, or bell

Scyphozoans swim with rhythmic contractions of their bell, but their swimming ability is limited

Planktonic!

• Painful stings to swimmers

Page 39: Importance of Cnidarians

Economic Impact

• Cnidarians support various fished species and provide habitat for marine organisms.

• Coral reefs crucial for tourism; however, trade has led to habitat destruction.

• Considerable roles in food chains; capable of negative impacts, e.g., jellyfish swarms affecting tourism and fisheries.

Page 40: Ctenophora Overview

General Features

• Ctenophores (comb jellies) are exclusively marine; differ from cnidarians as they lack nematocysts, possessing instead colloblasts for prey capture.

• Display biradial symmetry and are considered voracious feeders, having the ability to double their size within a day.

Page 41: Ctenophore Anatomy

• Colloblasts: Capture prey with adhesive properties.

• Comb Rows: Eight rows of cilia for movement.

Page 42: Ecology of Ctenophores

• Predominantly marine, can influence zooplankton populations.

• An introduced species to the Black Sea caused considerable ecological and economic damage to local fisheries.

Page 43: Ctenophore Classification

Orders

1. Order Beroida: Prey on other ctenophores by engulfing them.

2. Order Cestida: Ribbon-like body structure; utilizes cilia for movement and feeding.

3. Order Lobata: Contains lobes for food collection, trapping zooplankton.