Form to Function Body Shape and Locomotion in

Form to Function: Body Shape and Locomotion in the Aquatic Environment

Fish

History • 550 million years ago • >25 950 species today • “Natural selection has ensured that the mechanical systems [that] evolved in fish…are highly efficient with regard to the habitat and mode of life for each species. ” (Sfakiotakis et al. 1999, 237) • Began as jawless anguilloform parasites • Now have a variety of forms Thompson 1971

Body Shape and Locomotion • Body and Caudal Fin (BCF) locomotion • Anguilloform – Whole body – Elongated, slender, flexible bodies • Subcarangiform/Carangiform – 2/3 1/3 of body – Stiffer body and caudal fin • Thunniform Sfakiotakis et al. 1999 – Stiff body – Only caudal fin and attachment – High crescent shaped caudal fin

Ecology, Tradeoffs, and Conservation • Found in every existing aquatic habitat • Many species endangered because of fishing pressures • Habitat destruction • Pollution • Speed comes at the cost of maneuverability • Have other types of locomotion foraging and maneuvering

Sea Turtles

History • • Family Cheloniidae 90 million years ago Evolved from amphibious form Order testudinomorpha is a sister taxon to crocodilia • Ancestral forms were sequential quadrupedal paddlers –Hindlimbs larger than forelimbs • Modern forms “fly”synchronous pectoral gait –Forelimbs are much larger than hindlimbs

Body Shape and Locomotion • one of the fastest moving reptiles • Hypertrophied forelimbs generate thrust on upstroke and downstroke • Lift based movement much like flying • Hindlimbs are used as rudders/elevators Davenport et al. 1984 • Clawless, smooth, long, flat feet • Short blunt head and neck • Non-retractable head and limbs • Smooth flexible shell • Tear drop shaped – Rounded blunt front with gently tapered rear with flat bottomed hydrofoil shape

Ecology, Tradeoffs, and Conservation • • • Habitat/Nesting site destruction/degradation • Pet trade • Caught in fishing nets • Low reproductive rates • Are unable to protect young Faster swimmers Efficient Pelagic Nearly invulnerable to predation as adults • Poor terrestrial – Movement – Nests • Diet – Jellyfish, eelgrass

PENGUINS (Spheniscidae)

History • Tertiary period (60 million years ago) • Evolved from flying birds similar to albatrosses • Earliest fossils from New Zealand • Forelimbs shorter/broader than modern albatross’, not as short/broad as modern penguins’ • Semi-flexible elbows • Places where muscle attached to bone suggests foot-propulsion • Phylogeny disputed

Body Shape and Locomotion • Streamlined body • Feathers • Stiff – reduces vibration and fluttering • Tightly packed (up to 70 per square inch) • Oil gland near tail • Bones • Thick and dense • Wing-propelled • Flipper-shaped wings used in flying motion • Allows thrust on upstroke and downstroke

Ecology, Trade-offs, and Conservation • 17 modern species • Spend up to 75% of life in water • Inhabit islands and remote parts of continents in Southern Hemisphere • Cannot fly to escape predators • Short legs make for inefficient walking on land (waddling) • Tobagganing • All species protected under law, 3 considered at risk • Threats include hunting, habitat destruction, global warming • Non-native predators • Cannot fly to escape dogs • Oil pollution • Have to surface to breathe

CETACEANS (Whales, Dolphins, and Porpoises)

History • Eocene (40 -50 million years ago) • Terrestrial quadrupedal ancestor from extinct suborder Archaeoceti • Pakicetus Ambulocetus Rodhocetus Basilosauridae Durodontidae • Quadrupedal paddling pelvic paddling dorsoventral undulation caudal oscillation Bejder and Hall 2002 Ambulocetus Thewissen and Bajpai 2001 • Evolution: streamlined body, loss of fur, backward shift of nostrils, transformation of forelimbs into flippers, flukes for swimming, loss of hindlimbs

Body Shape and Locomotion • Body shape for decreased drag • Streamlined shape • Loss of hindlimbs • Thunniform swimming – caudal oscillation • Resembles a standing wave • Lower third of body and caudal fluke moved through water in vertical plane • Specialized caudal fluke – lunate shape, provides thrust on both upstroke and downstroke • Vertebral column – controls movement, dampens oscillations, acts as shock absorber

Ecology, Trade-offs, and Conservation • 76 extant species • Inhabit every ocean of the world • Size range from 4 feet and 100 pounds (dolphin) to 100 feet and 130 tons (blue whale) • Disadvantage: they are large animals, one or two large young at a time that require parental care. This makes population growth slow. • Many species are endangered • Threats: commercial whaling, entanglement in fishing gear, collisions with ships, marine pollution

Conclusions • more efficient methods of swimming – drag based paddling lift based oscillation • Reducing drag – Streamlining shape – Eliminating extra limbs/claws/hair • Variety of forms developing at different times from separate beginnings