br26820_03_sharks-i
Page 1: Introduction to Sharks
PRIFYSGOL ABERYSTWYTH
University: Adran Y Gwyddorau Bywyd
Course: BR26820 Vertebrate Zoology
Lecture Topic: Blacktip reef sharks (Carcharhinus melanopterus)
Classification: Class Chondrichthyes
Page 2: Early Jawed Fish Faunas
Fossil Evidence of Early Jawed Fish
Key periods: Late Middle-Late Devonian (387.7-358.9 Ma)
Notable locations:
Germany
Australia
Canada
Antarctica
USA
Study: Wildungen, Brazeau & Friedman (2015)
Page 3: Evolutionary History of Chondrichthyes
Timeline
Devonian period saw diversity in sharks and relatives
Cladoselache: A notable example from 360 mya (million years ago)
Initial diversity primarily in freshwater environments
Page 4: Current Chondrichthyes Orders
Orders and Species Count
8 shark orders under ‘Superorder Selachimorpha’ (403 species)
4 ray orders under ‘Superorder Batoidea’ (534 species)
1 order of Chimaeras in ‘Subclass Holocephali’ (33 species)
Examples:
Skates, Stingrays, Eagle rays, Manta rays
Page 5: Synapomorphy of Chondrichthyes
Defining Characteristics
Unique mode of endoskeletal mineralization
Absence of bone from cartilaginous endoskeleton
Prismatic calcification of cartilage surface layers
Presence of bone in teeth and scales
Page 6: Shark Cartilage Ultrastructure
Imaging Techniques Used
X-ray CT scans to view blue shark head
Cryo-SEM of stingray upper jaw showing uncalcified cartilage and calcified tiles
Detailed imaging of chondrocytes
Page 7: Shark Vertebrae Morphology
Basic Structure
Shark vertebrae have simple morphology
Spinal cord encased within the neural canal
Key Components:
Notochord
Basapophysis
Rib
Page 8: Phylogeny of Chondrichthyes
Ancient Characters in Evolution
Phylogenetic group: CHONDRICHTHYES
Traits include:
Dorsoventrally flattened bodies
Specialized jaws and enlarged pectoral fins
Prismatic endoskeletal calcification
Page 9: Early Fish Exoskeleton
Dermal Bone and Skin Structure
Derive from dermal bone that forms in skin
Reference to 'Dogfish' or 'catshark' (Scyliorhinus canicula) demonstrating rough skin due to placoid scales
Page 10: Placoid Scales Structure
Formation of Placoid Scales
Develop in dermis and project through to the surface
Components:
Enamel tip
Dentin layer
Pulp cavity
Page 11: Dogfish Teeth
Tooth Structure
Comparison between teeth and placoid scales
Analysis of 'dogfish' or 'catshark' (Scyliorhinus canicula) teeth and their homologous structures to placoid scales
Page 12: Dogfish Tooth Replacement
Development and Replacement
Ligamentous band facilitates developing teeth line behind functional teeth
Tooth replacement occurs roughly on a weekly basis in young sharks
Page 13: Anatomy of Shark Jaws
Cranial Kinesis
Jaw movements allow for protrusion of the upper jaw
Example: Great white shark (Carcharodon carcharias)
Page 14: Shark Jaw Suspension Type
Hyostylic Jaw Suspension
The jaw's movable attachment mechanism to cranium
Elastic ligaments provide flexibility for cranial kinesis
Page 15: Gill Openings in Chondrichthyes
Character Traits Related to Gill Structure
Includes various characteristics such as unsupported gill openings
Structures affected by evolutionary changes in elasmobranchs
Page 16: Shark Ventilation - Ram Ventilation
Definition
Water flows into the mouth and out through gills when in movement
Common in active species like Tiger shark (Galeocerdo cuvier) and Oceanic whitetip shark (Carcharhinus longimanus)
Page 17: Shark Ventilation - Buccal Pumping
Definition
Method of water intake at rest via mouth and spiracles
Example: Velvet belly lanternshark (Etmopterus spinax) demonstrating this method
Page 18: Combined Ventilation Strategies
Ventilation Systems
Various sharks utilize both ram ventilation and buccal pumping based on activity
Obligate ram ventilators include Great white and mako sharks; obligate buccal pumpers include nurse and carpet sharks
Page 19: Shark Gill Structures
Detailed Gill Anatomy
Frontal cross-section exhibits complex structure between various gill components including gill filaments and arches
Page 20: Basking Shark Feeding
Ecology and Behavior
Basking shark (Cetorhinus maximus) is known as a filter feeder
Important role in marine ecosystems, notably in the waters of the British Isles
Page 21: Gill Filaments in Basking Shark
Feeding Mechanics
Utilizes comb-like gill rakers to filter zooplankton from water
Description and functional importance outlined
Page 22: Evolutionary Theory of Filter Feeding
Studies and Findings
Investigated gill structure across multiple species including blue tilapia and paddlefish
Insight into evolutionary adaptations in sharks for filter feeding
Page 23: Vortical Flow Filtration Model
New Feeding Theory
Describes how vortices created by gill arches enhance feeding efficiency
Simulations indicated interaction between flow patterns and gill rakers
Page 24: Independent Origins of Filter Feeding
Diversity in Filter Feeding
Identified three distinct filter-feeding sharks differing in family structures and feeding morphology, including basking and megamouth sharks
Page 25: Summary of Key Findings
Important Points
Sharks have existed since the Devonian period with unique phylogenetic characters like prismatic calcification
Key adaptations for feeding and breathing strategies explored
Filter feeding appears to have evolved independently among various shark species
Page 26: Image Acknowledgements
References and Sources
Multiple publications and researchers cited for images and data regarding shark biology and evolutionary context.