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 Chordata Subphylum 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 Lamniformes Focus: basking sharks Photos: D. Burton

Order Charcharhiniformes Groundsharks: Overview Photo: Paul Humann Photo: Guillaume Chanfreau

Order Charcharhiniformes Focus: Hammerheads Photo: Guillaume Chanfreau

Order Charcharhiniformes Focus: reef sharks (requim)

Order Orectolobiformes Carpetsharks: Overview

Order Orectolobiformes Focus: Wobbegongs

Order Orectolobiformes Focus: Nurse sharks Photos: Paul Humann

Order Orectolobiformes Focus: Whale sharks Photo: Werner Mischler

Order Heterodontiformes Bullhead sharks Horn shark Photo: Tom Campbell, Innerspace VIsions

Order Hexanchiformes Photos: Michigan Science Art Frill shark Bluntnose sevengill shark

Order Squaliformes Dogfish sharks Spiny dogfish Photo: J. Stafford-Deitsch

Order Squaliformes Cookie-cutter shark

Order Pristiophoriformes sawsharks

Order Squatiniformes Angel sharks

Skates and rays Overview Photos: Paul Humann

Order Rajiformes: skates

Order Torpediniformes electric rays

Order Myliobatiformes bat rays, stingrays, manta rays Photo: Andy Murch Photo: Paul Humann

Class Chondricthyes Subclass Holocephali