Podcast
Questions and Answers
What is the primary function of the mantle cavity in mollusks?
What is the primary function of the mantle cavity in mollusks?
Mollusks have a well-developed coelom that is extensive throughout their body.
Mollusks have a well-developed coelom that is extensive throughout their body.
False
What structure in mollusks conducts waste and fecal material from the body?
What structure in mollusks conducts waste and fecal material from the body?
mantle cavity
The shell of mollusks is primarily made of ______.
The shell of mollusks is primarily made of ______.
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Match the following structures with their functions in mollusks:
Match the following structures with their functions in mollusks:
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What are spiracles responsible for?
What are spiracles responsible for?
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Echinoderms are only found in freshwater environments.
Echinoderms are only found in freshwater environments.
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What is the function of trichomes in the tracheal system?
What is the function of trichomes in the tracheal system?
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Echinodermata are so named owing to their __________ skin.
Echinodermata are so named owing to their __________ skin.
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Match the following echinoderms with their common names:
Match the following echinoderms with their common names:
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What is the primary function of the cuticle in nematodes?
What is the primary function of the cuticle in nematodes?
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Nematodes have circular muscles that assist in burrowing movement.
Nematodes have circular muscles that assist in burrowing movement.
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What process do nematodes undergo to shed their cuticle?
What process do nematodes undergo to shed their cuticle?
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The muscle connections in nematodes are known as __________.
The muscle connections in nematodes are known as __________.
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How do nematodes primarily move?
How do nematodes primarily move?
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Match the nematode features with their descriptions:
Match the nematode features with their descriptions:
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What happens to free-living nematodes placed in a watery environment?
What happens to free-living nematodes placed in a watery environment?
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Nematodes have both longitudinal and circular muscles.
Nematodes have both longitudinal and circular muscles.
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What helps to provide support and shape to the body of walking leg arthropods?
What helps to provide support and shape to the body of walking leg arthropods?
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The process of shedding the exoskeleton is called ecdysis.
The process of shedding the exoskeleton is called ecdysis.
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What are the stages between molts in the molting process called?
What are the stages between molts in the molting process called?
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An exoskeleton is shed during the process of ______________.
An exoskeleton is shed during the process of ______________.
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Which of the following appendages is specifically mentioned for swimming locomotion?
Which of the following appendages is specifically mentioned for swimming locomotion?
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Match each term with its correct definition:
Match each term with its correct definition:
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What stores glycogen reserves that cannot be used during the molting process?
What stores glycogen reserves that cannot be used during the molting process?
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What is the process of apolysis involved in?
What is the process of apolysis involved in?
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The premolt stage involves the hardening of the new exoskeleton.
The premolt stage involves the hardening of the new exoskeleton.
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What role does the central nervous system play in the process of molting?
What role does the central nervous system play in the process of molting?
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During postmolt, the ___ of the new exoskeleton occurs.
During postmolt, the ___ of the new exoskeleton occurs.
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Match the following stages of molting with their description:
Match the following stages of molting with their description:
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Which organ performs digestion in crustaceans?
Which organ performs digestion in crustaceans?
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Crustaceans possess a complete gut system.
Crustaceans possess a complete gut system.
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What is the primary function of hemolymph in crustaceans?
What is the primary function of hemolymph in crustaceans?
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What type of symmetry do adult echinoderms exhibit?
What type of symmetry do adult echinoderms exhibit?
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Echinoderms have specialized excretory organs.
Echinoderms have specialized excretory organs.
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What is the primary material comprising the endoskeleton of echinoderms?
What is the primary material comprising the endoskeleton of echinoderms?
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Echinoderms are fundamentally __________, coelomate deuterostomes.
Echinoderms are fundamentally __________, coelomate deuterostomes.
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Match the echinoderm structure with its function:
Match the echinoderm structure with its function:
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What is the term for the connective tissue that allows echinoderms to maintain posture without muscular effort?
What is the term for the connective tissue that allows echinoderms to maintain posture without muscular effort?
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All echinoderms have a complete gut with an anus.
All echinoderms have a complete gut with an anus.
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What unique system do echinoderms use for locomotion and feeding?
What unique system do echinoderms use for locomotion and feeding?
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Study Notes
Phylogenetic Tree of Bilateria
- Bilateria is a group of animals with bilateral symmetry
- The tree shows the evolutionary relationships among major animal clades
- The tree displays the proposed evolutionary history of animals
- The phylogeny is based on the study of similarities and differences among animals
- The clades in the tree are indicated by branching patterns
- The tree demonstrates a proposed evolutionary history for animals
- Some clades are marked with red indicating their evolutionary relationships
Body Form: Platyhelminthe vs Annelida
- Both are bilaterally symmetrical and triploblastic (having three germ layers)
- Platyhelminthes lack an internal body cavity (acoelomate)
- Annelids are the first animals to develop a true coelom (internal body cavity) in the space between the body wall and gut
- A coelom allows for the development of complex organs with muscles
- Platyhelminthes have a simple body structure
- Annelids have a more complex and segmented body, with a complete gut
Phylum Annelida
- 20,000 species range from 1mm to 3m in size
- Found in all environments
- Includes earthworms, leeches, and polychaetes
Eunicidae
- The infamous sand striker (AKA bobbit worm)
- Predatory worms that burrow beneath the ancient seafloor
- Have scissor-like jaws to capture prey
Taxonomic Classification of Phylum Annelida
- Phylum Annelida is divided into: -Sedentaria -Errantia -Oligochaeta -Hirudinea -Class Polychaeta (primitive annelids & flatworms)
Phylogenetic relationships of Annelids
- Polychaeta is a clade of annelids
- Major clades of annelids are shown
- Relationships presented using morphology and molecular phylogenetics were compared
- Relationships are shown in red for groups not considered annelids due to modifications
- Relationships that lack: segmentation, closed circulatory system & chaetae are shown in blue
Characteristics of Annelids (polychaeta)
- Bilaterally symmetrical, triploblastic (3 germ layers) with coelom
- Segmented (but not in some groups like Sipuncula)
- Metamerically segmented worms
- Cephalization (head) = prostomium
- Complete digestive tract with regional specialization
- Ventral nerve cord, associated ganglia, & circular segmental connectives
- Parapodia (1 pair per segment): only in polychaetes
- Chaetae (bristles): laterally arranged epidermal in each segment
- Closed circulatory system: dorsal and ventral blood vessels (not in Sipuncula)
- Reproduction: asexual/sexual, gonochoristic/dioecious/hermaphroditic, and indirect/direct development
- Trochophore larvae in some polychaetes
Body Form of Phylum Annelida
- Well-developed metamerism (true segmentation)
- Allowed for the evolution of a new type of locomotion based on segmental hydrostats
- Septa divide coelom (except in leeches) ensuring constant volume
- Shape controlled by circular and longitudinal muscles
- Shape coordinated by segmental ganglia
Body form of Phylum Annelida (Cross Section)
- Ventral nerve cord + segmental ganglia
- Dorsal and ventral blood vessels + segmental vessels
- 1 pair of parapodia or chitinous setae per segment
- 1 pair reproductive and excretory organs per segment
Body form of Phylum Annelida (Four Main Regions)
- Presegmental region (prostomium): cephalization/head
- Region surrounding the mouth (peristomium)
- Segmented body(metameric segments)
- Posterior pygidium (anus)
Feeding, Digestion in Annelids
- Complete digestive tract with modifications
- Foregut (buccal tube, pharynx: often eversible/proboscis increasing hydrostatic pressure)
- Jaws & metal-like structures to close (release hydrostatic pressure), retractor muscles
- Glands: mucus, and poisonous substances
- Midgut
- Hindgut: esophagus, stomach, & intestine (secreted cells) & anus
- Raptorial, deposit, & suspension feeding(types of feeding)
Feeding & Digestion: Predators
- Mobile hunters, sit-and-wait/ambush
- Poison glands (jaw); Gyceriidae (examples of predators)
Feeding & Digestion: Suspension Feeders
- Tentacular crown, water currents
- Cilia generate currents to capture small food particles→ bring food to mouth
- Sabellidae (example of suspension feeder)
Feeding & Digestion: Deposit Feeders
- Subsurface non-selective (Arenicola example) and surface selective
- Some species of Arenicola have different feeding strategies
Feeding & Digestion: Symbiotic Feeding
- Scale worms (Polynoidae) → live on bodies of Molluscs, echinoderms, and cnidarians
- Other worms (Myzostomida) → feed on tissues of echinoderms
- Pompeii worms → chemoautotrophic sulfur bacteria on their back
Feeding & Digestion: Midgut Structures
- Smooth or many folds, esophagus → stomach → intestine (anterior), and absorptive region in posterior
- Gland cells produce mucus to aid digestion.
Life in Sediments: Sand
- Polygordius jouinae is a nematode that lives in sandy sediments
- Measured sizes (L, W)
Gas Exchange & Circulation
- Bilateral symmetry, triploblastic (having three germ layers)
- Metamerically segmented worms
- Cephalization (head), prostomium
- Ventral nerve cord, ganglia, & circular segmental connectives
- Parapodia in some species
- Closed circulatory system in some species.
- Various respiratory structures like gills (ctenidia), tracheae, or cutanesous (direct) respiration
Gas exchange & Circulation in Annelids
- Depends on the species
- Through body wall, some have gills, and others have a closed circulatory system
- Oxygen availability in water is essential for gas exchange
Bioturbation & Bioirrigation
- Worms play essential roles in the health of sediments
- Eutrophication affects water quality and oxygen availability in sediments
Nervous System & Sense Organs
- Dorsal cerebral ganglia (prostomium), paired circumenteric connectives
- Lateral nerves extend to body wall muscles, parapodia, and digestive tracts
- Ventral nerve cord, segmental ganglia,
- Sensory systems vary
Nervous System & Sense Organs (Free Living Flatworms)
- Protonephridia - a function in osmoregulation
- Connect to networks of collecting tubes (internally closed)
- Leaves through nephridiopores (often 2)
- Collect fluid carrying wastes across thin membrane
- Fluid intake driven by pressure differential
Reproduction & Life Cycle
- Asexual reproduction: budding (ex. Syllidae)
- Sexual reproduction (mostly): Dioecious or hermaphroditic
- Trochophore larva
- Many free-spawning forms to ensure high fertilization rates
Trochophore Larvae
- Planktotrophic trochophore
- Leicithotrophic trochophore/non-feeding
Reproduction & Life cycle (with Epitoky)
- Production of epitokous individual( vs. atoke); whole body transformation to epitokous
- Posterior segments swollen & filled with gametes; head with enlarged eyes
- Parapodia enlarged & with different chaetae
- Gut atrophies
Reproduction & Life Cycle (Asexual): Different Types
- Clonal production: clusters of outgrowths; linear series/single clones
- Some species of worms can reproduce both sexually and asexually
Reproduction & Life Cycle (Asexual): Palolos
- Palolos are a Pacific delicacy
- Current IUCN Red List as threatened species
Taxonomic Classification: Annelida
- Clade Polychaeta division (Sedentaria & Errantia)
- Classes Clitellata (Oligochaeta & Hirudinea)
- Crassiclitellata, a group of clitellates.
Feeding & Digestion: Crassiclitellata
- The gut is divided into foregut, midgut and hindgut
- Two structures: crop and gizzard
- Increased surface area, middorsal groove (typhlosole).
Gas Exchange & Circulation: Crassiclitellata
- Gas exchange primarily through skin
- Specialized pumping structures in the dorsal vessel called the pseudohearts
Nervous System & Sense Organs: Crassiclitellata
- Cerebral ganglion, single ganglionated ventral nerve cord (or paired ventral cords fused)
- Ventral ganglionated nerve cord.
Reproduction: Crassiclitellata
- Hermaphrodites (restricted to anterior segments)
- Cross fertilization
- Mucus secretion by clitellum
- Formation of a cocoon
- Egg deposition
Reproduction: Crassiclitellata
- Mating: worms align at opposite directions and sperm exchange occurs via spermathecae
- Fertilization occurs in the cocoon
- Direct development
Excretion & Osmoregulation:
- Metanephridia: serially arranged in segments (1 pair/segment).
- Open to outside and body fluids
- Inner ciliated funnel (nephrostome)
- Long duct; storage region
- Selective reabsorption of water and nutrients; waste excretion to different fluid composition
- Marine annelids: osmoconformers
- Body osmolarity fluctuates with environment
Excretion & Osmoregulation: Free-Living Flatworms
- Protonephridia primarily function in osmoregulation
- Connect to networks of collecting tubules (internally closed)
- Nephridiopores (often 2)
- Collect fluid carrying wastes across thin membrane
- Fluid intake driven by pressure differential
- Essential for movement to freshwater
Taxonomic Classification: Annelida
- Clade Polychaeta (Sedentaria & Errantia)
- Classes Clitellata (Oligochaeta & Hirudinea)
- Crassiclitellata, a group of clitellates
Body Plan: Hirudinea
- External annulation does not match segmentation
- 33 segments
- Anterior sucker, midbody segments, posterior sucker
Body Plan: Hirudinea (Internal)
- Crassiclitellata vs Hirudinea
- Obvious difference: septa, septum separating every segment, thinner vs. thicker epidermis, coelomic fluid flows throughout the body
Movement: Hirudinea
- Posterior sucker attaches
- Circular muscle contracts
- Anterior sucker explores/attaches
- Posterior sucker releases
- Longitudinal muscle contracts
Feeding & Digestion: Hirudinea
- Uniquely adapted to freshwater/terrestrial habitats
- Scavengers, predators (small invertebrates), parasites (blood-feeding)
- Mouth opening, salivary glands, enzymes aid penetration of proboscis (jawed/non-jawed)
- Crop with large caeca (food storage)
- Anus location: posterior sucker
Feeding & Digestion: Hirudinea
- Some have symbiotic bacteria to digest blood meal (Aeromonas hydrophila)
- Blood meal digestion may take 6 months
- Vulnerable to predators after blood meal due to reduced mobility
Medical Importance: Hirudotherapy
- Recent studies find new uses for an ancient treatment (blood restorative)
- Reduce hematomas difficult to treat
- Promotes bleeding & reduces scars
- Hirudo medicinalis and H. verbena listed as near threatened (protected)
- Reduce arthritis pain
Nervous System & Sense Organs: Hirudinea
- 2 to 10 dorsal eyes with varying complexity
- Sensory papillae
- Negatively phototactic
- Respond to vibrations or warm temperatures in environment
Reproduction: Hirudinea
- Hermaphrodites
- Sperm transfer between individuals using a copulatory apparatus
- Fertilization: How does it differ from Crassiclitellata?
- Cocoon receives?
Phylum Mollusca
- 73,000 species (second largest phylum)
- Most morphologically diverse phylum
- Includes giant squid (13m in length), clams >1m
- Gastropods are the only molluscan class to successfully invade terrestrial environments
Overview: Major Molluscan Taxa
- Many species are synonymized
- Identifying species is based on barcode gene sequences (esp. bivalves & gastropods)
- 8 classes: (3 common, 2 less known)
- Bivalvia (clams, scallops, oysters etc.), Gastropoda (snails, slugs, limpets), Cephalopoda (nautilus, squid, octopus), Polyplacophora (chitins with 8 shell valves), Scaphopoda (tusk shells), and others
Phylogenetic Tree of Bilateria (Major Clades)
- Displays a proposed evolutionary history for animals
- Shows evolutionary relationships among major animal clades
- Based on similarities among animals.
What is a Mollusc?
- Bilateral symmetry (or secondarily asymmetrical), unsegmented
- Triploblastic (but limited)
- Main body cavity = hemocoel; open circulatory system
- Mantle-thick epidermis secreting shell & enclosing mantle cavity
- Heart in pericardial chamber; ventricle & 2 atria
- Large muscular foot (locomotion & burrowing)
- Radula (if present)
- Complete gut with specializations, metanephridia
- Trochophore larva & shelled veliger larvae
Mollusca Body Plan
- 3 regions: head, foot & visceral mass
- Mantle- thick epidermis secreting shell & enclosing mantle cavity
- Mantle cavity-houses respiratory surface (ctenidia)
- Aquatic species use mantle cavity to circulate water for gas exchange & removal of wastes, receives fecal material from anus and excretory wastes from nephridia
- Shell (calcium carbonate)- protection & support
Mollusca Body Plan
- Complex multilayered cuticle (chitin, proteins)
- Epidermis, cuticle, muscular layers, hemocoele
- Mantle: extension of body wall that folds around visceral mass
- Shell (specialized) glands secrete calcium-carbonate
Mollusca Body Plan: Characteristics
- Complete gut (foregut, midgut & hindgut), coelom limited, open circulatory system (hemocoel, except cephalopods)
- 1+ pairs nephridia
- Paired dorsal cerebral ganglia, nerve ring, paired longitudinal nerve cords, pedal ganglia
Circulation & Gas exchange: Mollusca Body Plan
- Open circulatory system with hemocoel, contains hemolymph
- Hemocyanin, hemoglobin, or myoglobin pigments
- Varies, most have gills, (ctenidia), others have a mantle for gas exchange
Circulation & Gas exchange: Mollusca Body Plan
- Two branchial vessels along gill axis
- Water flowing across ctenidia
- Afferent vessel carries oxygen-depleted hemolymph
- Efferent vessel carries oxygenated hemolymph
- Countercurrent exchange
Mollusca Shell (e.g. Bivalve)
- Calcareous exoskeleton (CaCO3)
- Covered by a protein layer ("periostracum")
- Produced by mantle glands, grows as animal grows
- Growth lines visible on surface
Mollusca Shell (e.g. Bivalve)
- Layers: prismatically layered, nacreous (iridescent)
- Mantle epithelium-calcifying epithelium for production of shell
Ocean Acidification & Global Warming
- Higher CO2 levels lowers seawater pH, forming carbonic acid and making bicarbonate less abundant
- This affects shell formation
Development / Larvae
- Direct metamorphosis leads directly to a juvenile form
- Indirect metamorphosis involves trochophore & other larval stages
- Bivalves have a second larval stage (veliger larva)
- Planktotrophic & lecithotrophic larvae
Class Bivalvia (Clams, Oysters, Scallops)
- 2 valves connected by hinge
- Open and close shells by adductor muscles
- No head, eyes, tentacles or radula
- Pair of labial palps
- Enlarged mantle cavity (lines the shell & surrounds foot & visceral mass)
- May have siphons(fused mantle), for filtering & gas exchange
Class Bivalvia (Clams, Oysters, Scallops)
- Foot = laterally compressed, allows for burrowing and anchorage
- Sensory structures: statocysts & sensory nerves
Class Bivalvia (Clams, Oysters, Scallops)
- Sessile form: oysters & mussels, attach via threads(byssal threads, byssal glands)
- Move through burrowing/muscular action and hydraulic pressure
Class Bivalvia (Clams, Oysters, Scallops)
- Marine or freshwater habitats.
Class Gastropoda (Snails, Slugs, Limpets)
- Asymmetrical body
- Spiral coiled shell (reduced/lost in some)
- Head with eyes/tentacles
- Radula, or Crystalline style
- 1-2 Nephridia
- Foot (modified for swimming, burrowing & adhering to surfaces)
- Mantle rotates with respect to its foot
Gastropod Torsion
- During development, the mantle cavity & visceral mass are twisted
- Several theories exist about the consequences and advantages of torsion
Infraclass Heteropoda (Sea Slugs)
- Lack true ctenidia
- Simple gut (no glands)
- No crystalline style
- Short intestine
- Radula absent/reduced
- Shell reduced/absent/developed
- Operculum if present= horny
- Head with eyes & tentacles
- Hermaphroditic
Superorder Nudipleura
- Detorsion
- Reduction/loss of shell
- Mantle covers viscera, lost cavity
- Anal & excretory structures move to body surface
- No ctenidia
- Cerata (dorsal projections) with diverticula of gut & cnidosacs
- Rhinophores for sensory
- Warning coloration & chemical defense
Class Cephalopoda (Nautilus, Squid, Cuttlefish, Octopus)
- Highly modified
- Shell (reduced/lost) except nautilus
- Large, complex eyes, tentacles (arms w. suckers)
- Beak with radula
- Mantle cavity with 1-2 pairs of ctenidia, muscular funnel= siphon
- Well-developed nervous system (excellent learners)
- Benthic & pelagic marine predators
Giant Squid (with body & tentacles 13m!)
- Internal & rudimentary shell (chitin & protein), function unknown
- Mantle cavity
General anatomy of Octopus
- Visceral hump (organ mass)
- Arms & suckers
- Siphon (funnel)
- Ink sac
Class Polyplacophora (Chitins)
- Flattened body
- 8 dorsal plates/valves connected by flexible membranes
- Thick girdle (calcareous spines/scales/bristles)
- Marine, intertidal, deep-sea
Class Scaphopoda (Tusk Shells)
- Shell (one piece, 2 openings)
- Mantle cavity extends posteriorly
- No ctenidia or eyes
- Radula
- Long, contractile tentacles (clubbed)
- Marine, benthic
Movement: Bivalves
- Foot (compressed, anteriorly/posteriorly)
- Burrowing, anchor
- Muscle action, hydraulic pressure by adductor muscles, shell valve closure.
Movement: Sessile Bivalves (oysters, mussels)
- Sessile (attach to surfaces), use byssal threads
- Contrast to burrowing/motile bivalves
Movement: Gastropods
- Foot (important in locomotion),
- Muscular contractions / waves
- Can adhere to rocks (some)
Movement: Swimming in Molluscs
- Bivalves (valve flapping), Gastropods (undulations), Cephalopods (jet propulsion),
Feeding: Molluscs
- Browsing/scavenging, herbivory, predatory
- Jaws, radula & other structures
Feeding: Gastropods
- Radula diversity (scraping)
- Boring radula (acidic chemical)
- Some species feed sucking body fluids.
Feeding: Bivalves
- Microphagy (filter feeding) using ctenidia & labial palps.
- Suspension feeding
- Deposit feeding,
Feeding: Other Gastropods
- Some species parasitize fish; others suck body fluids
Feeding & Digestion: Molluscs
- Complete gut (with components)
- Glands that produce enzymes like salivary glands for herbivore digestion
- Some have caeca
- Extracelluar digestion in some
Feeding & Digestion: Cephalopods
- Prey captured using tentacles & delivered to mouth by muscular stomach contractions
- Digestive enzymes released
Feeding: Different types and examples
- Suspension feeders, deposit feeders, symbiotic feeders, other mollusks like predators
Symbiotic Relationships
- Giant clams & zooxanthellae (dinoflagellates in the mantle)
- Iridophores in mantle function.
Digestion:
- Complete gut(components?)
- glands in the body for secretion of enzymes
- Herbivores(gizzard)
Digestion: Bivalves & Some Gastropods
- Stomach: chitinized gastric shield, crystalline style, cilia for sorting
- Crystalline style produced by protostyle
Circulation & Gas Exchange: Arthropods
- Large, open hemocoel
Circulation & Gas exchange in Arthropods (details)
- High variability among taxa, various sizes and shapes of heart
- Structures for gas exchange
Excretion: Arthropod
- Variety of structures: nephridia, Malpighian tubules
Nervous System: Arthropods
- Similar to many other protostomes: cerebral ganglia, deutocerebrum, tritocerebrum
- Paired ventral ganglionated nerve cords
- Varied sensory structures, sense organs
Sense Organs: Arthropods
- Setae, hairs, bristles, pores, and slits are sensory structures
- Mechanoreceptors on various body parts
- Chemoreceptors for sensing chemicals
- Photoreceptors (simple ocelli, compound eyes)
Reproduction: Arthropods
- Gonochoristic (formal mating)
- Internal fertilization
- Parent care (brooding)
- Development mixed (brooding, encapsulation followed by larval stages), direct development
- Some cases of multiple reproductive modes.
Reproduction: Crustaceans (characteristic larval stage)
- Nauplius stage
- No external segmentation at this stage
- 3 appendages
- Median eye cluster
- Dorsal cephalic shield; true compound eyes, other larval stages.
Reproduction: Larval Stages
- Zoea larva (brachuran crab)- early life
- Megalopa larva (brachuran crab)- later life
Feeding: Barnacles
- Sessile
- Use cirri to filter feed (actively sweeping cirri through the water)
- Traps food and moves particles from the rear to the mouth
- Biramous/Uniramous structure.
Feeding: Different Crustacean Types
- Filter feeders, scraping surface feeders, detritus feeders
Feeding: Caprellids
- Are not shrimp, amphipoda
- Movement- inchworm-like, subchelate appendages (clinging)
- Filter/scrape food from substrate, ambush predators.
Digestion: Crustaceans
- Foregut (includes mouth, esophagus, etc.), contractions to move food to midgut
- Contains a stomach with different parts
- Common in scavengers, predators, & some herbivores
Gas Exchange: Crustaceans
- Varies
- Gills
- Cutaneous uptake (e.g. Isopods)
Reproduction: Crustaceans
- Gonochoristic (some hermaphrodites), copulation
- Many copulate (some courtship behaviors, seasonal pairing)
- Females may hold male sperm for long periods.
- Can vary in length of life cycle.
Reproduction & Development: Other Crustaceans
- Environmental stress can affect reproduction.
- Some crustaceans exhibit phenotypic plasticity.
Reproduction: Fiddler Crabs
- Gonochoristic
- Mate attraction
- Ebbinghaus Illusion
Phylum Arthropoda: Chelicerata
- Subphylum Chelicerata
- Classes: Euchelicerata
- Subclasses: Arachnida, Merostomata, & Pycnogonida
- Orders within subclasses
Order Scorpiones (True Scorpions)
- Among oldest terrestrial arthropods
- 3 main body regions: prosoma, mesosoma, metasoma
- Prosoma: pedipalps (grasp prey, defense), chelicerae, median & lateral eyes
- Mesosoma: walking legs, book lungs
- Metasoma: telson with stinger, gonopore, pectines
Order Scorpiones (Sensory Structures)
- Have setae (mechanoreceptors) on appendages & slit sensillae
- Trichobothria (for detecting airborne vibrations)
- Unique sensory appendages (pectines) for mechanoreception & chemoreception.
Order Scorpiones (Reproduction and Development)
- Complex courtship and mating ritual
- Spermatophore deposition
- Viviparous
- Development may take up to a year
Order Araneae (Spiders)
- Two tagmata: prosoma & opisthosoma attached by pedicle
- Prosoma includes chelicerae, pedipalps, mouthparts
- 8 simple eyes
- Opisthosoma: book lungs/tracheae, spinnerets
Order Araneae (Feeding and Digestion)
- Predators/carnivores
- Web capture or hunting, chelicerae & bite.
- Gnathobases grind food
- Suck up liquidized food by specialized coxae.
Order Araneae (Details and examples)
- Silk: complex protein from spinnerets(various types for specific functions: attachment/anchor, protection, immobilizing prey, protective egg sac)
- Spider webs
Respiration: Chelicerates
- Book lungs or tracheae
- Blood flow through lamellae
Respiration: Hexapods
- Tracheal system
- Openings through cuticle= spiracles→branching networks (tracheoles)
Phylum Echinodermata
- Exclusively marine: benthic adults, pelagic larvae
- Triploblastic
- 7300 species (includes sea stars, sea urchins, sand dollars, brittle stars, & sea cucumbers)
Characteristics of Echinoderms
- Deuterostome triploblastic, coelomate
- Pentaradial symmetry (secondarily)
- Water vascular system
- Body wall with mutable collagenous tissue
- No specialized excretory organs
- Decentralized nervous system
- Mostly gonochoristic
Body Wall: Echinoderms
- Epidermis overspongy Dermis
- Skeletal elements: ossicles (CaCO3, living cells)
- Muscles & peritoneum coelom form the body wall.
Body Wall: Echinoderms (details and examples)
- In echinoids, ossicles form a rigid test
Phylum Echinodermata (various aspects and examples)
- Body structures
- Larval stages
- Adaptations
- Other aspects of their body plans
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Description
Test your knowledge on the anatomy and functions of mollusks and nematodes. This quiz covers key structures, processes, and characteristics of these fascinating invertebrates. Perfect for biology students looking to deepen their understanding of these phyla.
