fishies

• Why are we only studying aquatic fishes?

  • The term “fish” is paraphyletic (only becomes monophyletic if you consider tetrapods fishes)
• Gnathastomata


  Jawed fishes
• Groups under Agnatha (jawless fishes)

  • Myxini (hagfishes)
  • Petromyzontiformes (lampreys)
• Characteristics of Myxini

  • Monstrous-like
  • Elongated (can twist themself)
  • Ventral column/ belly has large slime glands
  • Sister to vertebrates
• Characteristics of Myxini

  • Monstrous-like
  • Elongated (can twist themself)
  • Ventral column/ belly has large slime glands
  • Sister to vertebrates
• Myxini twists themselves to tear up food
• Myxini has slime glands to:

  • Excrete slime to deter predators
  • Has biomedical potential
• Characteristics of Petromyzontiformes:

  • Elongated
  • Circular region on mouth called oral disc
  • Has specialized larvae: Amnocoete
• Petromyzontiformes is called "cyclostomata" because of their oral disc
• Petromyzontiformes using their oral disc to attach to substrate and host (to rasp away flesh)
• Group under Gnathastomata

  • Chondricthyes (sharks, rays, chimaeras)
• Chondrichthyes are known as "cartilaginous fishes"

  • Endoskeleton mostly made of cartilage (with calcium salts → makes them harder)
• 2 major groups under Gnathastomata:

  • Elasmobranchii (sharks, rays)
  • Holocephali (ratfish, chimaeras)
• Sharks = So. Selachimorpha
• Characteristics of Sharks (So. Selachimorpha)

  • Global distribution
  • Ecological distribution: carnivores
  • Mode of reproduction: internal (claspers)
  • Method of giving birth: oviparity and viviparity
• Example of a meso predator

  White-tip shark
• Specialized type of carnivory in sharks

  • Invertivorous (invertebrate feeding)
  • Zooplanktivorous (zooplankton feeding)
• Examples of Invertivorous shark

  Port Jackson Shark -- molari form jaws to crush the shells of gastropods
• Example of zooplanktivorous sharks

  • basking shark
  • whale shark
  • megamouth shark
• • Oviparity - lays eggs (EX. mermaid's purse)
  • Viviparity - live bearing
• In some viviparous shark pups, some pups feed on each other to survive
• Anatomy of Sharks (HICS-D)

  • Hetero circle tail
  • Continuously replacing teeth
  • Intestines have spiral valves
  • Scales have pulp inside them
  • Different portions in external anatomy: pelvic, pectoral, anal fins
• Sharks' pelvic fin pulls females during reproduction
• 2 modes of respiration for sharks

  • Ventilation - continuously moving
  • Buccal pumping - close and open mouths
• Ecological role of sharks

  • Carnivorous – apex/ meso predators
  • Food for humans (economical role)
• Other groups under Chondrichthyes

  • C. Sarcopterygii
  • sC. Holocephali
  • C. Actinopterygii
  • So. Batoidea
• Animals under Sc. Sarcopterygii (lobed fin fishes)

  • Coelocanths
  • Lungfish
• Animals under C. Actinopterygii

  • Ray-finned fishes
• Animals under sC. Holocephali

  • Ratfish
  • Chimaera
• Animals under sO. Batoidea:

  • Rays
  • Skates
• Defining characteristics of C. Sarcopterygii

  • Robus "lobes" (because of slow transition)
  • Has lung-like structure
• Sarcopterygii are found in deep water or freshwater:

  • Deep waters – Coelacanthiformes
  • Invertivorous and piscivorous
  • Freshwater – Dipnoi
  • Omnivorous
• Sarcopterygii practice "aestivation" (a form of torpor) when their habitats get hot and dry
• Sarcopterygii aestivation:

  • When water levels get low – >They burrow → slowly build cocoon underwater (with mucus to seal)
  • Rain will cause them to emerge 
• Who is the oldest living lungfish?

  Methuselah
• Holocephali key characteristics:

  • Operculum (bony gill-cover)
  • Separate urogenital and anal opening
  • 2 claspers: pelvic and cephalic claspers
• Holocephali's cephalic claspers are in the head; used for reproduction to hold female and deliver seminal fluid
• Holocephali are mostly benthic, therefore they are invertivores and piscivores
• Holocephali uses their food plates to crush hard-shell invertebrates
• C. Actinopterygii key characteristics:

  • Ossified endoskeleton (like Sarcopterygii)
  • Operculum (gill cover)
  • Scales come from dermal portion