Form and Function: Fish (begin)

Marine Vertebrates: Lecture 1

Challenges of the marine environment

•Density

•Pressure

•Temperature

Temperature stratification

Challenges of the marine environment

•Density

•Pressure

•Temperature

•Light

Light attenuation with depth

Challenges of the marine environment

•Density

•Pressure

•Temperature

•Light

•Salinity

•Oxygen

Oxygen vs. depth

Challenges of the marine environment• Density

• Pressure

• Temperature

• Light

• Salinity

• Oxygen

• Seasonality

• Substrate

Vertebrate phylogeny

• Vertebrates are thought to be monophyletic, descended from a cephalochordate (or urochordate?) ancestor So ultimately, all marine vertebrates are

related

• However, the “marine vertebrates” themselves are polyphyletic, with various groups arising from fresh water or land-based ancestors at different times.

Fish phylogeny

Likely common ancestor to vertebrates: Phylum ChordataSubphylum Cephalochordata

• Invertebrate chordate = “lancelet”

• Larvae and adults have all chordate features (four shown plus endostyle = thyroid precursor)

• Muscles develop from somites: blocks of mesoderm (segmented)

Subphylum Cephalochordata: lancelets

Fish phylogeny: “Craniata”•Derived character: neural

crest cells/cranium

Neural crest/ cranium

Neural crest (Craniata)

Phylum Chordata, Subphylum Myxini: Hagfish

Campbell, Fig. 34.9

Fish phylogeny: Phylum Chordata, Subphylum Vertebrata• Derived character: vertebral column

Vertebral column

Subphylum Vertebrata;Class Cephalaspidomorphi

Fish phylogeny: Phylum Chordata, Subphylum Vertebrata, “Gnathostomes”• Derived characters: jaws, bone,

paired fins

Jaws; Bone;

Paired fins

Gnathostomes

• Jaw development From which structures?

•Development of bone Which structures were first

mineralized?

•Development of paired fins Hypothesis for origins?

Class Chondrichthyes: Subclass Elasmobranchii

Elasmobranchii: Features

• Skeleton Vertebral

column Cranium Teeth Upper jaw Ceratotrichia

• Nostrils

Elasmobranchii: Features

Spiral valve within intestine:

Function?

Pelvic fins with claspers.

Function?

Elasmobranchii: Features

•Gills

•Scales: placoid

•Buoyancy

Australian Museum of Natural History

Circulation

Campbell, Biology

Respiration: countercurrent exchange

Campbell, Biology

Additional features

• Osmoregulation

• Reproduction Oviparity Ovoviviparity Viviparity

Feeding

Shark Orders

Order Lamniformes: mackerel sharks Overview

Focus: Family Lamnidae•Adaptations for effective

swimming Body shape (note snout!) Fins Ram ventilation Cruising speeds: ~3 km/h (great

white) Speed bursts: Up to 35 km/h (mako) Elevate body temperature

•Countercurrent heat exchange

Countercurrent heat exchange: Great white shark

The Behavior of White Sharks and their

Pinniped Prey during predatory attacks • Summary of research by Klimley,

Pyle and Anderson, 1996 (for next Monday!)

Deskpicture.com

Order LamniformesFocus: basking sharks

Photos: D. Burton

Order Charcharhiniformes Groundsharks: Overview

Photo: Paul Humann

Photo: Guillaume Chanfreau

Order CharcharhiniformesFocus: Hammerheads

Photo: Guillaume Chanfreau

Order CharcharhiniformesFocus: reef sharks (requim)

Order Orectolobiformes Carpetsharks: Overview

Order OrectolobiformesFocus: Wobbegongs

Order OrectolobiformesFocus: Nurse sharks

Photos: Paul Humann

Order OrectolobiformesFocus: Whale sharks

Photo: Werner Mischler

Order HeterodontiformesBullhead sharks

Horn shark Photo: Tom Campbell, Innerspace VIsions

Order Hexanchiformes

Photos: Michigan Science Art

Frill shark

Bluntnose sevengill shark

Order SqualiformesDogfish sharks

Spiny dogfish Photo: J. Stafford-Deitsch

Order SqualiformesCookie-cutter shark

Order Pristiophoriformessawsharks

Order SquatiniformesAngel sharks

Skates and raysOverview

Photos: Paul Humann

Order Rajiformes: skates

Order Torpediniformeselectric rays

Order Myliobatiformesbat rays, stingrays, manta rays

Photo: Andy Murch

Photo: Paul Humann

Class ChondricthyesSubclass Holocephali