Lecture 5+6+7

Cards (130)

  • Molluscs
    • Triploblastic - bodies derived from 3 primary germ layers
    • Coelomates - possess a true coelom, a fluid-filled body cavity lined by mesoderm
  • Mollusc body plan

    • Head-foot portion (ventral) - contains head, sensory organs, foot for movement
    • Visceral mass (dorsal) - contains internal organs
  • Mantle
    Protective layer that can secrete the shell
  • Shell
    Hard, protective outer structure
  • Visceral Mass
    Area containing the internal organs
  • Anatomical features common to molluscs
    • Mantle and mantle cavity
    • Muscular foot
    • Visceral mass containing internal organs
  • Radula
    Tongue-like organ with chitinous teeth used for feeding, to scrape or cut food before ingestion
  • Many molluscs have a trochophore larval stage in their development, a free-swimming larva common among marine invertebrates
  • Circulatory system of molluscs
    • Open circulatory system - blood flows freely through cavities and bathes organs directly
    • Cephalopods have a closed circulatory system - blood contained within vessels for more efficient transport
  • Parts of the mollusc body
    • Mantle
    • Shell
    • Visceral Mass
    • Heart
    • Intestine
    • Anus
    • Mantle Cavity
    • Gill
    • Coelom
    • Digestive Gland
    • Stomach
    • Mouth
    • Radula
    • Eye
    • Head-Foot
    • Foot Retractor Muscles
  • Parts of the radula
    • Esophagus
    • Radula (ribbon-like structure with rows of teeth)
    • Radula sac
    • Muscles
    • Odontophore cartilage
  • Layers of the mollusc shell
    • Periostracum
    • Prismatic layer
    • Nacreous layer
  • Mantle epithelium
    Tissue of the mantle that secretes the shell's materials
  • Mantle
    Layer of tissue that drapes over the visceral mass and secretes the shell components
  • Shell gland
    Specialized region of the mantle responsible for initiating shell secretion
  • Gastropods are among the most numerous and diverse groups of molluscs, inhabiting marine, freshwater, and land environments
  • Torsion
    Unique developmental process characteristic of gastropods, resulting in the rotation of the visceral mass, mantle, and shell 180 degrees with respect to the head and foot
  • Stages of torsion in gastropods
    • Pre-torsion stage
    • Post-torsion stage
  • Torsion allows the gastropod to retract into its shell with the head entering last, which can be an effective escape response
  • Torsion introduces complications like the potential for fouling, as waste material from the anus is now in close proximity to the head and feeding structures
  • Reproductive strategies in gastropods
    • Egg-laying
    • Dioecious (distinct male and female)
    • Monoecious (hermaphroditic)
    • Protandry (start as male, later change to female)
    • Livebearing
  • The typical larval stage in marine gastropods is the trochophore, which then develops into a veliger larva
  • Bivalves
    • Possess a shell consisting of two hinged parts (valves)
    • Many lead a mostly sedentary lifestyle, attaching to substrates
    • Some can move by clapping their shells together to "swim"
    • Inhabit almost every aquatic habitat
    • Filter feeders, drawing in water through their gills to filter out plankton and organic particles
  • Anatomical features of bivalve shells
    • Adductor muscle scars
    • Line of mantle attachment
    • Teeth
    • Grooves for teeth
    • Umbo
    • Anterior
    • Posterior
    • Dorsal
    • Ventral
  • Bivalve body parts
    • Mantle
    • Shell
    • Adductor muscle
    • Incurrent aperture
    • Excurrent aperture
    • Paired gills
    • Foot
    • Suprabranchial chamber
    • Nephridium
    • Heart and blood vessels
    • Digestive tract
  • Bivalve digestive system
    • Mouth
    • Labial palps
    • Esophagus
    • Stomach
    • Style sac
    • Digestive gland
    • Intestine
    • Anus
    • Gonad
    • Heart
    • Pericardial cavity
    • Nephridium
    • Gill
    • Mantle
    • Cerebral ganglion
    • Pedal ganglion
    • Foot
  • Bivalve circulatory system
    • Heart
    • Pericardial cavity
    • Anterior aorta
    • Posterior aorta
    • Visceral mass
    • Vein from foot
    • Artery to mantle
    • Blood sinus of foot
  • Bivalvia - Circulation
    • Heart: Two auricles and one ventricle, pumps blood into arteries
    • Pericardial Cavity: Space surrounding heart where blood is collected from gills and pumped back into body
    • Anterior Aorta: Carries oxygenated blood from heart to anterior body
    • Posterior Aorta: Carries oxygenated blood from heart to posterior body
    • Visceral Mass: Area where internal organs are located, blood flows around to supply nutrients and oxygen
    • Vein from Foot: Blood vessels that return deoxygenated blood from foot to gills
    • Artery to Mantle: Carries oxygenated blood to mantle for gas exchange and shell formation
    • Blood Sinus of Foot: Cavity in foot filled with blood for nutrient/waste exchange
    • Artery to Foot: Delivers oxygenated blood to muscular foot for movement and burrowing
  • Red arrows represent flow of oxygenated blood, blue indicates return of deoxygenated blood to heart and gills
  • Bivalves do not have a separate set of capillaries, arterial blood is released directly into visceral mass sinuses
  • Bivalvia - Reproduction: Reproductive Modes

    • Dioecious: Separate male and female individuals
    • Monoecious (Hermaphroditic): Produce both eggs and sperm
    • Protandrous: Function as male then female at different life stages
  • External Fertilization
    Gametes released into water column, fertilization occurs externally
  • Developmental Stages
    • Trochophore: Free-swimming larval stage with cilia for swimming and feeding on plankton
    • Veliger: Larval stage with shell development and velum for feeding/propulsion
  • Unionid Bivalves and Brooding

    • Unionids brood larvae in mantle cavity
    • Glochidium Release: Larvae released to parasitize fish
    • Parasitic Stage: Larvae develop on fish host
  • Class Cephalopoda: General Characteristics
    • Modified Foot: Arms/tentacles surround head, foot evolved into funnel/siphon
    • Head and Visceral Mass Alignment: Head above body, head-first swimming
    • Muscular Mantle: Covers body, role in locomotion via jet propulsion
  • Cephalopoda: Circulation and Sensory Adaptations
    • Closed Circulatory System: Blood contained in vessels for efficient oxygen transport
    • Advanced Sensory and Nervous Systems: Complex brains, highly developed eyes
  • Cephalopoda: Diversity and Evolution
    • 550 living species
    • Octopuses, Squids, Nautilus
    • Extinct Ammonites: Coiled shells
  • Cephalopoda: Ecological and Biological Aspects
    • Predatory Lifestyle: Hunting strategies, beaks, venom
    • Camouflage and Communication: Rapid color change
    • Reproduction: Direct fertilization, mating behaviors, semelparity
    • Intelligence: Advanced learning and problem-solving
  • Nautiloids
    Ancient cephalopods with gas-filled chambered shells for buoyancy control
  • Ammonites
    Extinct cephalopods with complex, ornate chambered shells