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Questions and Answers
What is the approximate number of species in the Protostomes group?
What is the approximate number of species in the Protostomes group?
Where are nematodes commonly found?
Where are nematodes commonly found?
What is the ecological role of non-parasitic nematodes?
What is the ecological role of non-parasitic nematodes?
What is the potential density of nematodes in ocean sediments?
What is the potential density of nematodes in ocean sediments?
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Which of the following nematodes are known to be significant pests?
Which of the following nematodes are known to be significant pests?
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How do certain fungi trap nematodes?
How do certain fungi trap nematodes?
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What is a characteristic feature of nematode body plans?
What is a characteristic feature of nematode body plans?
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Which of the following statements about nematodes is incorrect?
Which of the following statements about nematodes is incorrect?
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What are the key features of basal Ecdysozoan groups like Nematoda?
What are the key features of basal Ecdysozoan groups like Nematoda?
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Which statement accurately describes the ecological importance of Nematodes?
Which statement accurately describes the ecological importance of Nematodes?
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What is a primary characteristic of the life cycle of key nematode parasites?
What is a primary characteristic of the life cycle of key nematode parasites?
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Which of the following statements is true regarding Pan-arthropods?
Which of the following statements is true regarding Pan-arthropods?
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What is a distinguishing feature of the Ecdysozoan phylogeny?
What is a distinguishing feature of the Ecdysozoan phylogeny?
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Which of the following organisms are included in the Ecdysozoa group?
Which of the following organisms are included in the Ecdysozoa group?
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What is a common misconception about Nematodes?
What is a common misconception about Nematodes?
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The Cambrian group split in the Ecdysozoan phylogeny led to the diversification of which groups?
The Cambrian group split in the Ecdysozoan phylogeny led to the diversification of which groups?
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Study Notes
Ecdysozoa: Nematodes & Pan-arthropods
- Course: BIO1427
- Recording date: 8.2
- Lecturer: Jolyon Troscianko
Learning Objectives
- Understand key features of basal Ecdysozoa: Nematoda, Tardigrada, and Onychophora
- Understand the niche and ecological importance of Nematodes
- Understand the life cycle of key nematode parasites and their interaction with hosts
- Understand the basics of pan-arthropods
Warning
- Images of parasitic worms and their hosts may be present in the material
- Content may not be considered "beautiful" natural history
Ecdysozoan Phylogeny
- Ecdysozoa is a broad animal group in Bilateria.
- Mouth develops first during embryonic development (protostomes)
- Includes nematodes, tardigrades, and arthropods
- Cambrian group split from other protostomes ~510 million years ago
- Roughly 83% of all bilaterians
- Includes over 1.2 million named and extant species (likely many more total)
Nematoda (Roundworms)
- Over 18,500 species, possibly up to 1 million
- Half of them are parasitic
- Common examples: C. elegans, human pinworm, dog roundworm, hookworm, heartworm, and canine whipworm
Nematode Basics
- Abundant in various environments, including marine sediment (up to 4 million individuals/sq meter)
- Essential for nutrient cycling
- Important in a wide range of habitats (ocean sediment, soil, inside plants and animal tissues, hot springs and polar ice)
Fungi trapping & consuming nematodes
- Some fungi prey on nematodes by trapping them in nets or nooses
- They release chemical cues to attract nematodes toward food sources
Nematode body plan
- Typically cylindrical, but some parasites can be large (e.g., Placentonema gigantissima)
- Covered by a tough, elastic cuticle
- No circulatory system, but nutrients are moved via pseudocoelom fluid
- Longitudinal muscles for undulatory movement
Flatworms vs. Annelid worms
- Flatworms are flat, lack a coelom, and move via cilia
- Annelid worms are segmented, have both circular and longitudinal muscles for movement
Caenorhabditis elegans
- Model organism in developmental biology
- Simple, transparent, and easily manipulated
- Entire development of every single cell mapped out, >4.5 million scientific papers published
- Used in research but medical models frequently fail for human results even with success in mice
Loiasis (Loa loa)
- African eye worm disease
- 12-13 million people infected
- Transmitted by deer fly bites
- Passes back into the deer fly via infected blood
- Treatable, but therapy can be dangerous for humans
Lungworms
- Important parasites of cattle
- Transmission occurs through soil, and ingestion of contaminated material
- Can cause serious illness in infected cattle
Accidental Hosts
- Certain roundworms (e.g. Ophidascaris robertsi) are normally in carpet pythons
- Humans can be accidental hosts, usually by contact and consumption of contaminated food
Anthelmitic eco-toxicity
- Anti-worming drugs used on farm animals
- Can negatively impact non-target organisms (e.g., dung beetles).
- Reduces prevalence of cattle nematode infections and pest flies
Hygiene hypothesis
- Connection exists between sanitized environments and inflammatory autoimmune diseases
- Lack of early exposure to pathogens may reduce immune system's resilience
- Th1 vs. Th2 response balance linked to autoimmune diseases
Ecdysozoa: Arthropods & their Cuticles
- Key features of arthropods
- Process of moulting and structure of arthropod cuticle & epicuticle
- Benefits and limitations of a rigid exoskeleton
- Sensory adaptations in arthropods
Arthropod Cuticle
- Thin outer layer (epidermis) with outer cuticle (procuticle, exo- and endocuticle).
- Epicuticle is thin at joints to allow for moulting
- Dermal glands secrete waxy layer after moulting
Epicuticle
- Covered by hydrophobic lipid or wax layer
- Reduces dehydration in terrestrial groups
- Used in signalling/recognition
Procuticle
- Primarily chitin (polysaccharide)
- Sclerotisation with cross-linking proteins makes cuticle darker
- Crustaceans add calcium carbonate to further strengthen cuticle
Arthropod musculature
- Have striated muscle bundles for movement
- Attached to epidermis and the hard cuticle
- Apodemes provide attachment area
Arthropod Exoskeleton
- Made of plates connected by articulation membranes
- Often has condyles and sockets for joints.
Arthropod Movement
- Muscle contraction used for locomotion and manipulation
- Exoskeleton acts as lever and joints
- Blood pressure in some cases moves body parts
Arthropod Hematocoel
- Filled with hemolymph
- Fluids transport some nutrients, hormones, and immune system components
Arthropod Conquest of Land
- Evidence suggests arthropods moved onto land in the early Cambrian period
- Exoskeletons were likely crucial for adapting to terrestrial environments (reducing desiccation, providing support for movement)
Arthropod Sense Organs
- Exoskeleton limits detection of stimuli, and requires sensilla for sensory input
- Different eye types found (pit eyes, camera eyes, compound eyes)
- Provide rapid directed feedback
- Complex visual systems evolved in the Cambrian
Arthropod Visual Adaptations
- Varied colour receptors, polarization, extreme low-light and speed vision
- Visual system requires large energy investment
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Description
Explore the fascinating world of Ecdysozoa, including Nematodes, Tardigrada, and Onychophora, in this BIO1427 course. Understand their ecological importance, unique features, and life cycles, especially focusing on nematode parasites. Get ready to dive deep into the evolutionary history and diverse species of this broad animal group.
