Invertebrates Flashcards
Animals are part of the clade:
Closest relative
Opisthokonts
Closest relative: Choanoflagellates
Early milestones in animal diversification
Oldest animal fossil: 575Mya
DNA divergence: Suggest 850 Mya
When did most species arise?
Cambrian explosion: 542-525 Mya
Mal’s favourite
Hallucigenia
Spined worm
Similar to our velvet worm today
4 branches of phylogenetic tree
1) Parazoa
2) Eumetazoa
3) Lophotrochozoa
4) Ecdysozoa
Clade Porifera
Part of Parazoa "Pore-bearers" - sponges Multicellular, lack true tissue Filter/suspension feeders Asexual/sexual reproduction Vet significance: Drug discovery
Poriferan structure
Sponge structure Water diffuses through membrane Contains Choanocycts Engulf by phagocytosis Water movement out the top
Choanocysts
Create a current that draws water in through the porocytes
Clade Eumetazoa divided into 2 clades
1) Radiata
2) Bilateria
Radial Symmetry
- Many surgical plane forms symmetry
- Cutting oral to anus in many planes will all form symmetry
Bilateral Symmetry
- Only 1 surgical plane forms symmetry
Example of Radial Symmetry
Phylum Cnidarians “nettle animals”
Cnidarians are: (4)
- true tissues
- Radial symmetry
- diploblastic
- all venomous
Cnidarias diploblastic tissue (2)
1) Epidermis (ectoderm)
2) Gastrodermis (endoderm)
What type of gastrovascular cavity do Cnidarians have?
Blind gastrovascular tract
- mouth doesn’t open to anus
Compare/contrast gastrointestinal tract of sponges, cnidarians, animals
Sponges: have spongocoel - cavity containing seal water
Cnidarians: Simple gastro-tract surrounded by tentacles
Animals: Contain have gastrointestinal tract
Cnidocil
Stinging sites: spikes on the outer surface which is a trigger for cnidocyte
Cnidocyte
stinging portion which discharges threat to attach predator
4 clades of Cnidarian Diversity
[CASH]
1) Cubozoa
2) Anthozoa
3) Scyphozoa
4) Hydrozoa
Cubozoa
- hydrozoans
- poly dominant
Anthozoa
- Anemones and corals
- Sessile polyps
Scyphozoa
- Jellyfish
- Medusa dominant
Why were Hydrozoa (hydra) used as a model?
1) Regeneration of tissue
2) Asexual reproduction by budding
3) Staining of live tissue
4) Eyeless animals can respond to light
Box Jellyfish
- ambush predator
- highly venomous (neurotoxin)
- lethal to humans
- nematocysts fire on contact with skin
Treatment: Vinegar to disable nematocysts
Bilateria has allowed for (2)
1) Forward, directed movements
2) Cephalization
Cephalization
Formation of a head region
Results in:
1) sensory structures
- can respond to environmental gradients
Are bilateria monoblastic, diblastic, or triploblastic organisms
Triploblastic
Triploblastic
Ectoderm (outside)
Mesoderm (Middle)
Endoderm (inside)
Are Cnidaria monoblastic, diploblastic, or triploblastic?
Diploblastic
Ectoderm
Brain, nerves, peripheral nerves
Skin, hair, nails, mouth lining, tooth enamel
Mesoderm
Kidneys, gonads, circulatory system, muscles, notochord, and body cavity
Endoderm
Lining of GI tract, respiratory tubes, liver, pancreas
Clades of Bilateria
1) Lophotrochozoa
2) Ecdysozoa
3) Deuterostomia
Phyla of Lophotrochozoa (4)
[PAAM]
1) Platyhelminths
2) Annelida
3) Acanthocephela
4) Mollusca
4 classes of Platyhelminths
[CTTM]
1) Cestoda
2) Trematoda
3) Turbellaria
4) Monogenea
Turbellaria
Class of Platyhelminths
- Free living
- commensal
- some parasitic
- ciliated epidermis for locomotion
- acoelomate
- Excretory system - Protonephridial
Protonephridial system
- waste material drains from body to excretory cells called flame cells
Metanephridia system
- filtrate is filtered from blood in special filtration sites (ex, kidney)
Planaria
- models for regeneration
- worm contain 279 pieces - each can regenerate an entire worm
- each cell is a neuroblast - can develop onto many different tissues
Syncytial
Cells have merged to form a super-cell, but contain many nuclei
Flukes and Tapeworms are aways (1)
Parasitic/commensal organisms
Monogenea
Parasites of Fish
Obligate ecto-parasites
Life cycle: Eggs laid on host, fall off host, hatch, larvae seeks new host
Gyrodactylus
Russian doll life cycle
Only gives rise to 2-4 offspring
Offspring already contained within parent
Trematoda
Class of platyhelminths obligate parasites Adults live in intestine - attach to mucosal wall Hermaphroditic Complex life cycle with 2 or more hosts
Fasciola hepatica
Trematoda
Fluke of sheet, cattle, grazing animals, us
Liver fluke
Anaemia due to blood sucking nature
Fasciola hepatica life cycle
1) Eggs pass in faeces
2) (Larval stage) Miracidium in water passed to snail
3) Sporocysts, redia, cercaria by Asex, repro.
4) Encystment (metacercaria)
5) Eaten by host (ex, sheep)
How do Fasciola hepatica and Schistosomes differ?
Fasciola: Hermaphroditic
Schistosomes: 2 different sexes (dioecious)
Similarities between Fasciola and Schistosomes
1) Both infect snails as intermediate hosts
2) Change in larval stages due to asexual reproduction
Cestoda
Tapeworms Parasite of SI Class of Platyhelminths No mouth, digestive tract, or anus Repro. system replicated as chain
5 structures of Cestodes
1) Scolex
2) Neck
3) Immature proglottids
4) Mature proglottids
5) Gravid proglottids
6) Strobila
Examples of tapeworms
Taenia Sagitta (cows) Taenia Solium (pigs)
Life cycle of tapewors
1) Gravid proglottids leave host in faeces
2) Intermediate host ingests
3) Cysts in intermediate host muscle / larval scolex attaches
4) Definitive host eats infected intermediate host
Echinococcus granulosus
- class Cestodes of Platyhelminth phylum
- Hydatid tapeworm
- Hermaphroditic
- Definitive host: dog, dingo, fox
- Intermediate host: sheep, cow, marsupials, humans
- Transmission: through ingestion of hydatid cysts
Clade Lophotrochozoans contains four phylums
1) Playhelminths (no body cavity)
2) Mollusca (body cavity)
3) Annelida (body cavity)
4) Acanthocephala
3 types of body cavities
1) Acoelomate
2) Coelomate
3) Pseudocoelomate
Acoelomate
No body cavity
Body is solid
Coelomate
Fluid filled cavity lies between gut and body wall Lined by mesoderm on both sides 1) Separate control of organs 2) Circulatory system - larger size 3) Greater body complexity
Pseudocoelomate
Intermediate form of body structure
Lined by mesoderm on one side only
Examples of Acoelomate, coelomate, and pseudocoelomate
Acoelomate: Platyhelminths
Coelomate: Annelids, Mollusca
Pseudocoelomate: Nematoda
Annelida are (segmented/non-segmented) Example: (1)
Segmented
Example) Leaches
What are two benefits of segmentation in annelids?
1) Better control of body secretions
2) Diversification
Benefits of having body cavity
Coelomate
1) separate movement of body wall and organs
2) space for complex organs
3) storage for eggs and sperm
4) coelomic fluid protects internal organs
5) circulatory function and oxygen movement
6) wate removal
7) function as hydrostatic skeleton
Phylum Acanthocephala
Part of clade locotrophozoans
“thorny headed worms”
All parasitic
No gastrointestinal tract (acoelomate)
Intermediate hosts: Arthropods
Definitive hosts: Vertebrate
Life cycle of Acanthocephala
1) Eggs passed in faeces
2) Eggs ingested by beetle larvae
3) Pig ingests beetle larvae
4) Adult parasite lives in SI of Pig
Macracanthorhynchus hirudinaceous
Clade Ecdysozoans contains 2 phylums
1) Nematoda
2) Arthropda
What does Ecdys- mean?
- shedding exoskeleton
Nematoda
Roundworms Psuedocoelomate body cavity Longitudinal muscles only No respiratory/circulatory system Non-segmented, cylindrical body Internal transport via body fluid Complete gut - separate mouth/anus Dioecious
Dioecious
Seperate male and female individuals
Organism only contains male or female reproductive structures
Are Nematoday monoblastic, diblastic, or triploblastic?
Triploblastic
Psuedocoelomate body cavity
How do Nematodes grow?
Grow through moulting
Egg, 4 larval stages, adult
What allows Nematodes to be great parasites?
- very thick cuticle
- Cuticle has capacity to correct itself
What is the model organism for Nematodes?
C. elegans
Caenorhabditis elegans
C. elegans
Model organism of nematodes
Few cell types
First multicellular organisms to be sequenced
959 somatic cells in adult hermaphrodite
Important nematodes (2)
Nematodes - Roundworms
1) C. elegans
2) Haemonchus contortus
3) Ascarids
Types of Ascarids (4)
Ascarids = roundworms
1) Ascaris suum (pigs)
2) Ascaris lumbercoides (humans)
3) ParAscaris equi (horses)
4) Toxocara canis (dogs)
Types of Hookworms (2)
Hookworms are nematodes - roundworms
1) Ancylostoma caninum (dog/human hookworm)
2) Necator americanus (human)
General Ascarid information
Large intestinal worm
Occlude intestine
Females lay desiccation resistant eggs
Parascaris equorum
1) eggs in faeces
2) eggs ingested my horse
3) larvae hatch in SI
4) Larvae burry into SI wall, find blood ves.
5) Migrate to Lungs
6) Burst through alveoli to Trachea
7) Swallowed once in trachea
8) Adults live in SI
9) Eggs in faeces
What are the effects of Parascaris on equine host? (5)
1) Pneumonia due to migrating larvae
2) Loss of energy
3) Colic
4) Intestinal perforation
5) Intestinal obstruction
Pinworms
Enterobius vermicularis - humans
Oxyuris equi - horses
Dog Heartworm
Dirofilaria immitis
Dirofilaria immitus
Dog heartworm
Adult worms: live in the right side of heart and pulmonary artery
Also found in cats
Cause immune associated problems
Dog Heartworm lifecycle
Dirofilaria immitis
1) Microfilaria (L1’s) are ingested by mosquito
2) Mosquito transmits vector with blood mean
3) L1’s develop into L3’s in muscle in mosquito
4) L3’s migrate to mosquito salivary gland
5) Bite host
What is the infective agent in dog heartworm
Dirofilaria immitis
Microfilaria (L3’s) are infective agent
L3’s are in mosquito salivary gland
Lymphatic filariasis is caused by
Wuchereria bancrofti - causes elaphantitis in humans
- enlargement of the legs (edoema)
- enlargement of the scrotum (edoema)
What are three different types of muscle parasites?
1) Taenia sagitta (cows)
2) Taenia solium (pigs)
3) Trichinella spiralis (pigs)
Trichinella spiralis
muscle worm in pigs
intracellular parasite
Trichinella spiralis life cycle
1) ingestion of undercooked meat
2) Larvae released into SI
3) Adults in SI
4) Larvae deposited in mucosa
5) Encyst larvae in muscle of host
