4. LOPHOTROCHOZOA Superphylum

Mollusca, Annelida

LOPHOTROCHOZOA Characteristics (5)

Triploblastic

Bilateral

Cephalization Beginning

• Evolution of concentration of nervous tissues and sensory organs in head of organisms

Protostomes

• Acoelomate, pseudocoelomate, and eucoelmoate phyla

Lophophore

• Crown of ciliated tentacles that function in feeding

• Feeding apparatus/trochophore larva

PLATYHELMINTHES Phylum (Flatworms)

Flatworms

• Acoelomate

• Free-living and parasitic

• Lophophore/trochophore larvae absent

• Spiral cleavage

• Rhabditophora

  • Rod-like structures discharged in mucus produced by free-living flatworms

PLATYHELMINTHES (Flatworms) Anatomy

ABSENT Circulatory and Respiratory systems

• Gas and nutrient exchange dependent on diffusion and cell-to-cell junctions

Monoecious, internal fertilization

Asexual reproduction by fission

NERVOUS SYSTEM

• Cerebral Ganglia

• Eyespots

• Longitudinal Nerve Cords

• Transverse Nerves

• Peripheral Nerves

DIGESTIVE SYSTEM

• Mouth and Anus

• Pharynx

• Intestine

EXCRETORY SYSTEM (Protonephridia)

Protonephridia: Primitive network-like excretory organs

• Flame Cell

• Tubule/Tube Cell

• Excretory Canal

• Excretory Pore

PLATYHELMINTHES (Flatworms) Nervous System (5)

NERVOUS SYSTEM

• Cerebral Ganglia

  • Concentrations of nerve cell bodies

  • “Brain-like”

• Eyespots

  • Sensory organs for detecting light

• Longitudinal Nerve Cords

  • Main nerves running length of body

• Transverse Nerves

  • Connect longitudinal cords in ladder-like structure

• Peripheral Nerves

  • Branching nerves extending to body wall

PLATYHELMINTHES (Flatworms) Digestive System (3, 1 contains 2)

DIGESTIVE SYSTEM

• Mouth and Anus

  • Single opening to take both food in and expel waste out

• Pharynx

  • Muscular tube to pull food into body

• Intestine

  • Branched gastrovascular cavity that digests and distributes nutrients

PLATYHELMINTHES (Flatworms) Excretory System (PROTONEPHRIDIA)

EXCRETORY SYSTEM (Protonephridia)

Protonephridia: Primitive network-like excretory organs

• Flame Cell

  • Filters waste

  • Contains nucleus and cilia to propel fluid

• Tubule/Tube Cell

  • Channels that transport filtered fluid

• Excretory Canal

  • Main duct for waste transport

• Excretory Pore

  • Opening where waste exits body

CESTODES (Tapeworms)

Lack a mouth and gastrovascular cavity

ROTIFERA Phylum (“Wheel-bearer”) Characteristics

• Pseudocoelomates

• Corona (feeding structure)

• Filter-feeders

• Dioecious

• Microscopic

• Free-swimming/planktonic

ROTIFERA Anatomy (3 Regions, 9 Parts, 3-5-1)

3 Body sections

• Head, Trunk, Foot

Reproduction: Parthenogenesis

Parthenogenesis = Development from unfertilized eggs

HEAD REGION:

1. Corona

2. Mouth

3. Cerebral ganglion

TRUNK REGION:

1. Mastax

2. Digestive gland

3. Pseudocoel

4. Stomach & Intestine

5. Anus

FOOT REGION:

1. Foot & Toe

ROTIFERA Head Region (3)

HEAD REGION:

1. Corona

   • Food and locomotion

2. Mouth

   • Opening for food ingestion

   • Within corona

3. Cerebral ganglion

   • “Brain”

   • Central concentration of nerve cells

ROTIFERA Body Region (5)

BODY REGION:

1. Mastax

   • Muscular pharynx

   • “Toothy” jaw-like structures

     • Grind food

2. Digestive gland

   • Secretes enzymes to break down food

3. Pseudocoel

   • Fluid-filled body cavity that provides structural support

4. Stomach & Intestine

   • Primary sites for digestion and nutrient absorption

5. Anus

   • Opening for waste elimination

ROTIFERA Foot Region (1)

FOOT REGION:

1. Foot and Toe

• Posterior end used for attachment onto surfaces

NEMERTEA Phylum (Ribbon worms)

Bilateral

Coelomic/Acoelomates

Dioecious/monoecious

Fragmentation

Marine

Carnivore

NEMERTEA Phylum (Ribbon worms) Anatomy

KEY SPECIALIZED STRUCTURES:

• Proboscis

  • Long, muscular everisble tube to capture prey

  • Within rhynchocoel

• Rhynchocoel

  • Fluid-filled cavity that houses proboscis

NERVOUS SYSTEM (3):

1. Cerebral ganglion

2. Lateral nerve cord

3. Sensory papillae

DIGESTIVE SYSTEM (4):

1. Mouth

2. Stomach

3. Intestine

4. Anus

NEMERTEA (Ribbon worms) NERVOUS SYSTEM (3)

NERVOUS SYSTEM (3):

1. Cerebral ganglion

   • “Brain”

2. Lateral nerve cord

   • Two main nerve cords

   • Along sides of body

3. Sensory papillae

   • Small sensory organs, anterior tip

NEMERTEA (Ribbon worms) DIGESTIVE SYSTEM (4)

DIGESTIVE SYSTEM (4):

1. Mouth

   • Opening for food intake

2. Stomach

   • Initial processing chamber for food

3. Intestine

   • Long tube with diverticular pouches to increase surface area for nutrient absorption

4. Anus

   • One-way digestive system

MOLLUSCA Phylum Characteristics

Snails, slugs, squids, octopuses, clams, oysters

• Soft body

• Bilateral

• Cephalized

  • Sensory, feeding, neural organs concentrated at anterior

    • Forming distinct head and brain

• Triploblastic

• Protosomes

  • Mouth first

• Eucoelomates

  • Have a coelom completely lined by mesoderm

• Dioecious

MOLLUSCAN BODY REGIONS (3 Sections, 5-4-4)

PRIMARY BODY STRUCTURES (5):

1. Mantle

2. Mantle Cavity

3. Visceral Mass

4. Foot

5. Shell

DIGESTIVE SYSTEM (4):

1. Radula

2. Crop

3. Stomach & Digestive Gland

4. Intestine & Anus

NERVOUS SYSTEM (4):

1. Heart

2. Coelom

3. Nerve Cords

4. Gonad

MOLLUSCAN PRIMARY BODY STRUCTURES (5)

PRIMARY BODY STRUCTURES:

1. Mantle

   • Secretes calcium-carbonate-hardened shell

2. Mantle Cavity

   • Houses respiratory structures

     • Gills or Lungs

3. Visceral Mass

   • Digestive, nervous, excretory, reproductive, respiratory systems

   • Central region

4. Foot

   • Locomotion and anchorage

   • Muscular organ

     • MODIFIED FOOT IN CEPHALOPODS = ARMS & TENTACLES

5. Shell

   • Protective Outer Layer

MOLLUSCAN DIGESTIVE SYSTEM (4)

MOLLUSCAN DIGESTIVE SYSTEM:

1. Radula

   • Abrasive, tongue-like

   • Feeding

2. Crop

   • Storage pouch for food before digestion

3. Stomach & Digestive Gland

   • Primary sites of digestion and enzyme secretion

4. Intestine & Anus

   • Processes waste for elimination

MOLLUSCAN OTHER INTERNAL SYSTEMS

MOLLUSCAN OTHER INTERNAL SYSTEMS:

1. Heart

   • Central organ of circulatory system

2. Coelom

   • Main body cavity

3. Nerve Cords

   • Components of nervous system extending throughout body

4. Gonad

   • Reproductive organ

MOLLUSCA IMPORTANT CLASSES (3)

1. Gastropoda

2. Cephalopoda

3. Bivalvia

GASTROPODA CLASS (Stomach Foot)

“Stomach foot” (based on muscular foot placement

Flat stomach on foot

Snails

• Torsion embryonic development

  • Counterclockwise rotation of embryo

• 50% of aquatic and terrestrial mollusks

• Asymmetrical with coiled shells

CEPHALOPODA CLASS (Head Foot)

“Head foot”

Modified foot (arms & tentacles) that connect to head

Octopuses/squids/nautilus

• Bilateral

• Highly developed nervous system

• Jet propulsion

• Carnivores, predators

  • Beak-like jaw + radula

• Water/gas chambers for buoyancy

• Rapid color changing

• Dioecious

  • Lays eggs after mating

  • No larvae formation

BIVALVIA CLASS (2 Valves)

“2 Valves”

• Flattened body, no conspicuous head or mouth

• Filter feeders

• Absent radula

ANNELIDA Phylum (“Little Rings/Segmented”) (2)

“Little Rings”

• SEGMENTED

  • Metamerism = True segmentation

TWO TYPES:

1. Polychates

   • MARINE annelids with MULTIPLE appendages

     • PARAPODIA

       • Fleshy bristle-bearing appendages

       • Well-developed head with sensory organs

2. Oligochaetes

   • TERRESTRIAL

POLYCHATES

Annelida

• Marine

  • Bristle worms

• Multiple appendages

PARAPODIA

• Fleshy bristle-bearing appendages

• Well-developed head with sensory organs

OLIGOCHAETES

Annelida

• Terrestrial

  • Earthworms

ANNELIDA CHARACTERISTICS

• Teloblastic Growth

  • Growth BEHIND head

• Setae

  • Forms parapodia/pairs

  • Hair-like bristles

    • Traction, anchoring, preventing backsliding

• Well-developed and COMPLETE digestive system

  • 2 Separate Openings

• Simple respiratory system

  • Gas exchange across moist surface

EARTHWORM ANATOMY