Unit 2 Zoo

What is part of the super phylum Lophotrochozoa?

Nemertea, Platyhelminthes

Platyhelminthes Lophotrochozoa have either

• Lophophore feeding apparatus
• Cilia around the mouth

or
• Trochophore larvae
• Larva have two bands of cilia

Which phylums have a BILATERAL body plan

Nemertea, Platyhelminthes, Nematoda, Tardigrada

Which phylums have Triploblastic and Acoelomate tissues

Nemertea, Platyhelminthes

Epidermis for Nemertea and Platyhelminthes

layer of epithelial cells formed from ectoderm tissue

Mesoderm for Platyhelminthes

differentiates into a layer of circular muscle. also differentiates into mesenchymal cells that are excretory

Mesoderm for Nemertea

differentiates into muscle tissue

Endoderm for Nemertea and Platyhelminthes

differentiates into digestive system

Phylum Platyhelminthes AND Nemertea AND Nematoda AND Tardigrada Are

protosome

What is Simple cephalization in Platyhelminthes

Nerve tissue and sensory organs in a head

have eye spots called ocelli (sense intensity of light)

Platyhelminthes free-living species are

predators/scavengers

Platyhelminthes parasitic species

absorb nutrients from host’s gut

Platyhelminthes digestive system is

incomplete (protosomes)

• Mouth is also anus
• Branching gastrovascular cavity (GVC)
• Ingested food goes into branching digestive system
• Food is digested in the GVC then absorbed into cells lining the GVC and transported
throughout the body via diffusion across gap junctions

Platyhelminthes excretory system

network of tubules along the periphery of the animal

-connects to flame cells with cilia that propel metabolic waste out of the body through pores

Platyhelminthes Nervous system

consists of two lateral nerve cords running the length of the body

-cords connect to each other across the body, transverse nerves

-two cerebral ganglia surround ocelli for sensing light and chemicals

have no Respiratory system instead:

-O2 is absorbed through epidermis, Co2 released through epidermis

What does Platyhelminthes, Nematoda and Nemertea not having a respiratory system limit?

thickness of its body

Platyhelminthes have no Circulatory system instead:

Gases and nutrients move via diffusion and gap junctions

Platyhelminthes Reproduction

Most species are monoecious
• Highly regenerative
• Asexual reproduction through fragmentation
• Sexual reproduction, internal fertilization via “penis fencing”

What is penis fencing

• Individuals evert their penises and attempt to stab each other
• When one is victorious, sperm is released into body of the stabbed individual
• Sperm migrate to oviducts and fertilize the eggs
• Fertilized eggs are released
• Larvae hatch and grow through multiple larval stages

Defining characteristic of Nemertea

eversible proboscis

Eversible Proboscis in Nemertea

• Located in structure called rhynchocoel
• Harpoons prey
• Some species’ proboscis has barbs

Phylum Nemertea are usually part of what marine

benthic marine

Nemertea size

varies widely from 1cm to several meters

Nemertea have simple cephalization

• Cerebral ganglia comprise a rudimentary “brain”
• Sensory papillae provide sense of touch
• Ocelli are present in most species

Most Nemertea are

carnivorous

Nemertea circulatory system

• Have closed circulatory system
• Closed loop formed by a pair of connected blood vessels
• Blood flow is maintained by muscle contraction

Nemertea excretory system

a pair of tubules called protonephridia

Removes metabolic waste and maintains osmoregulation (*)

Nemertea nervous system

“brain” of four ganglia around the head and rhynchocoel
• A pair lateral nerves emerge on either side of the brain and travel the length of the body
• Most species have ocelli, often several pairs

Platyhelminthes, Tardigrada, Nemertea and Nematoda have no respiratory system, instead

• O2 absorbed through epidermis, CO2 released through epidermis

Nemertea Reproduction

• Highly regenerative
• Asexual via fragmentation
• Mostly dioecious

Where do Nemertea have gonads

along the digestive tract

What does Nemertea having gonads in their digestive tract mean

• Stem cells differentiate into gametes
• Typically exhibit courtship spawning
• External fertilization
• Larvae develop into trochophore larvae, growth through several larval stages

What superphylum is Nematoda in?

Ecdysozoa

Superphylum Ecdysozoa have

a cuticle (tough, flexible exoskeleton. Molt to grow)

Made of collagen and chitin

What tissues do Nematoda have

triploblastic and psudocoelomate

-Cylindrical tubular morphology

Where do Nematoda’s and Tardigrada’s live

all habitats

Are all Nematodas free-living?

some are free-living and some are parasitic

Phylum Nematoda have simple Cephalization, what does this mean?

• Cerebral ganglia comprise a rudimentary “brain”
• Sensory papillae and bristles provide sense of touch

What kind of digestive system do Nemertea, Nematoda and tardigrada have?

Complete

What makes a complete digestive system

• Has mouth and anus, food travels in one direction
• Well-developed digestive system
• Mouth has lips and teeth
• Prey enters mouth, then pharynx, then intestines
• Solid food waste exits anus

What do Nematoda do without a circulatory system?

diffuse gases and nutrients throughout body

Nematodas excretory system is very simple, how?

metabolic waste is ammonia, removed by diffusion

Nematoda’s nervous system

simple “brain” from which four longitudinal nerve cords
emerge and travel down length of body
• One nerve on dorsal side, two nerves are lateral (one on each side), one ventral nerve
cord is more developed

Reproduction in Nematoda is

Species specific:

• Monoecious
• Dioecious
• Parthenogenic

Reproduction in dioecious Nematoda

fertilization is internal

• Female lays eggs that develop for approximately two weeks
• Larvae molt four times, ecdysis

What superphylum is tardigrada part of?

Ecdysozoa

What is the Tardigrade cuticle made of?

chitin that is divided into plates

What tissues do Tardigrada have?

Triploblastic and eucoelomate

have hemocoel

What unique ability do Tardigrada have?

can suspend metabolism, cryptobiosis

What do Tardigrada’s eat

algae, plants, small animals

What size is tardigrada

very small, less than 1 mm

Tardigrada Morphology

• Cylindrical body with four pairs of legs
• First 3 pairs are for locomotion, last pair is for clinging
• Have bands of muscle for movement of legs
• Have simple cephalization
• Pair of eye spots for sensing light
• Sensory papillae and bristles provide sense of touch

What is different about Tardigradas complete digestive system

mouth with saliva instead of lips and teeth

Tardigrada have no circulatory system, what does it do instead?

Bodily fluid, blood contained within hemocoel

What is Tardigradas excretory system like?

malpighian tubules that transport metabolic waste to digestive system

What is tardigrada’s nervous system like?

simple brain with ventral nerve

individual ganglia extend into each leg

Tardigrada reproduction

dioecious

external fertilization

What does Tardigradas external fertilization look like?

• Reproduction occurs when animals molt
• Eggs are attached to molted cuticle
• Young molt many times at they grow into adults

Tardigrada

Nematoda

Nemertea

Platyhelminthes