CLASS TURBELLARIA

• • Free-living and parasitic and/or commensal
  • Aquatic and benthic, only a few are terrestrial
• Movement

  • Cilia: they glide over substrate; the ventral cells secretes mucus as they glide over
  • Musculature: (1) inner longitudinal and (2) outer circular muscle fibers (3) between these two, there's a set of diagonal muscles

  
• MOVEMENT

  • Pedal waves: waves of muscular contraction along the animal's ventral surface; undirectional from anterior to posterior
  • Peristaltic waves: progressive wavelike contractions
  • Looping: anterior attaches, pulls posterior forward, attaches posterior, releases anterior, organism moves forward.
• BODY WALL

  • Epidermis:
  • Monolayered, multiciliated, and syncytial
  • There's short microvilli found between cilia
  • gland cells are present
• BODY WALL

  • Duo-glands: paired secretory cells; temporary adhesion in interstitial organisms
  • viscid gland
  • releasing gland
  • Rhabdoid: rod-shaped and membrane bounded secretion; forms mucus that coats the animal's body to avoid predation
  • Rhabdite: aggregation of cells; secretes thick mucus
  • Frontal gland: anterior aggregation of secretory cells; defense, slime production for locomotion and adhesion

  
• NERVOUS SYSTEM AND SENSE ORGANS

  • Brain: subepidermal and ring like
  • Nerve cords: extends posteriorly; joins a nerve net located ventrally
  • Nerve net: ladder-like
  • Ocelli: eyes that may cluster over the brain
  • Statocysts: unpaired; medially near the brain; orients the animal's posture
  • Ciliary receptors: (mechanoreceptors) concentrated on tentacles, auricles and body margins
  • Chemoreceptors: locating food or mate
• PARENCHYMA is the connective tissue compartment between body wall musculature and the gut

  1. Epidermal replacement cells
  2. migrates from parenchyma to the body surface
  3. Replaces destroyed epidermal cells
  4. Neoblasts
  5. Totipotent
  6. Wound healing and regeneration
  7. Epidermal replacement cells
• PARENCHYMA

  3. Fixed parenchymal cells

  1. Branched cells that make junctions with other cells
  2. Gap junctions - intercellular channel for transport of gasses, metabolites and nutrients

  4. Chromatophores: allows cell to lighten or darken and is controlled by the brain
• DIGESTIVE SYSTEM AND NUTRITION

  • Incomplete digestive system
  • Gut wall
  • simple epithelium
  • ciliated
  • phagocytic and gland cells
  • Shape of gut
  • Microturbellarian
  • Macroturbellarian
  • Order Acoela

  
• DIGESTIVE SYSTEM AND NUTRITION

  Types of pharynx

  • Zero pharynx
  • mouth opens directly into the cytoplasm of the digestive syncytium
  • Simple
  • ciliated tube
  • Plicate
  • protrusible
  • long muscular tube
  • has a fold in its wall when retracted
  • free living
  • BUlbous
  • muscular bulb
  • for sucking
  • parasitic
• DIGESTIVE SYSTEM AND NUTRITION

  • Carnivorous
  • Extracellular digestion: enzymes
  • Intracellular digestion
  • Turbellarians: reabsorption of systemic tissues
  • Prey capture
  • Food swallowed whole or in pieces
  • Some organisms absorb nutrients through body wall
• REPRODUCTION

  • Regeneration
  • adjacent epidermis spreads over and seals the wound
  • blastema forms beneath the epidermis
  • Transverse cut (regeneration of new head)
  • regenerates faster on slices from the anterior than the posterior
• REPRODUCTION

  • Paratomy
  • parent's body differentiates into a chain of zooids before fission separates them into new individuals
  • Architomy
  • differentiation or regeneration after fission
• MALE REPRODUCTIVE SYSTEM

  • Testes: transports sperm
  • Sperm duct
  • Seminal vesicle: storage sac
  • Penis: copulatory organ that may be armed with stylet
  • Prostate gland: supplies secretions to penis
• FEMALE REPRODUCTIVE SYSTEM

  • Gonopore/vagina: copulatory organ
  • Copulatory bursa & seminal receptacle: storage of sperm
  • Ovaries
  • Oviduct
  • Uterus