Actinopterygian Relationships I Biology of Fishes 9.20.2012
Overview
Group Projects Intro
Review (Craniate Relationships)
Actinopterygian Relationships
Group Projects
Four General Categories (choose topic within 1 category)
Evolutionary Patterns (evolution of specific species or group; prehistoric fishes)
Biology (morphology, form and function, physiology)
Ecology (life history strategies, adaptations, behavior)
Conservation (historical issues, overfishing, invasive species, biodiversity loss, conservation methods)
Include an example of current research in that area
Group Projects
4-5 people per group
~15 min presentation, written paper
Sort into groups next Thursday (9.27)
Select topic by week of October 8
Review:
Craniate Relationships
Chondrichthyes CRANIATES
Sarcopterygii Vertebrates
Osteichthyes
Actinopterygii Review: Craniate Relationships
Hagfishes
Vertebrates
Lampreys
Gnathostomes (possess jaws) - Chondrichthyes (cartilaginous fishes) - Osteichthyes (bony fishes) Sarcopterygii (lobe-finned fishes) Actinopterygii (ray-finned fishes)
Review: Craniate Relationships
Characteristics
Possess a braincase (differentiates from tunicates and cephalochordates)
Other synapomorphies
Neural crest
Complex sense organs & cranial nerves
Muscularized gut wall, differentiated digestive organs
Respiratory gills, heart, and hemoglobin
Muscles to draw in water for feeding & respiration
Actinopterygian Relationships
Chondrichthyes CRANIATES
Sarcopterygii Vertebrates
Osteichthyes
Actinopterygii Actinopterygian Relationships
Sarcopterygii (lobe fins)
Actinopterygii (ray fins) - Cladistia (bichirs, reedfish) - Chondrostei (sturgeons, paddlefishes) - Neopterygii -Holostei (gars, bowfins) -Teleostei (teleosts, “modern fishes”)
Actinopterygian Relationships
Actinopterygii (Gr., aktin = ray + pteryg = wing or fin)
Fins supported by flexible rays (muscle & bone inside)
Teeth with enamel-like cap
Scales covered by enamel-like tissue, ganoine (primitive forms)
Single dorsal fin
Swim bladder connected to gut – can breathe air
Spiral valve – aids in digestion
Electroreception
Actinopterygian Relationships
Sarcopterygii (lobe fins)
Actinopterygii (ray fins) - Cladistia (bichirs, reedfish) - Chondrostei (sturgeons, paddlefishes) - Neopterygii -Holostei (gars, bowfins) -Teleostei (teleosts, “modern fishes”)
Actinopterygian Relationships
Cladistia (Polypteriformes; bichirs, ropefish/reedfish)
~13 species
Freshwater lakes, streams, swamps; tropical Africa
Lobe-like base of pectoral fins, ganoid scales
Obligate air-breather, two lungs
Maxilla fused to head
Long dorsal fin divided into finlets, each with a spine
Electroreception
Cladistia (Polypteriformes) Actinopterygian Relationships
Sarcopterygii (lobe fins)
Actinopterygii (ray fins) - Cladistia (bichirs, reedfish) - Chondrostei (sturgeons, paddlefishes) - Neopterygii -Holostei (gars, bowfins) -Teleostei (teleosts, “modern fishes”)
Actinopterygian Relationships
Chondrostei (sturgeons and paddlefishes)
Largely cartilaginous skeleton
Fusion of jaw bones – maxilla, premaxilla, dermopalatine
Loss of ganoid scales
Electroreceptors
Chondrostei
Sturgeons (Acipenseriformes)
~25 species
Distribution restricted to northern hemisphere
Some marine and some freshwater – lakes and large rivers
All migrate into freshwater rivers to spawn
Lake sturgeon (largest species in Great Lakes)
4 barbels, ventral sucking mouth, 5 rows of bony scutes
Valuable caviar – Beluga sturgeon worth over $100,000
Sturgeons (Acipenseriformes) Chondrostei
Paddlefishes (Acipenseriformes)
2 species – North American, Chinese
Freshwater, large rivers – extirpated from Great Lakes
Large paddle with electroreceptors
Filter zooplankton from water column
Chinese paddlefish different morphology, larger, and most endangered fish in China (likely extinct)
Paddlefishes (Acipenseriformes) Actinopterygian Relationships
Sarcopterygii (lobe fins)
Actinopterygii (ray fins) - Cladistia (bichirs, reedfish) - Chondrostei (sturgeons, paddlefishes) - Neopterygii -Holostei (gars, bowfins) -Teleostei (teleosts, “modern fishes”)
Neopterygii
Chondrichthyes CRANIATES
Sarcopterygii Vertebrates
Osteichthyes
Actinopterygii Actinopterygian Relationships
Neopterygii (Holostei and Teleostei)
Single independent skeletal support for each fin ray (dorsal and anal fins); allows fins to be collapsed and spread more easily
Specialized musculature allows fins to move side to side
Reduced heterocercal caudal fin
Loss of electroreceptors (eventually re-evolved)
Actinopterygian Relationships
Sarcopterygii (lobe fins)
Actinopterygii (ray fins) - Cladistia (bichirs, reedfish) - Chondrostei (sturgeons, paddlefishes) - Neopterygii -Holostei (gars, bowfins) -Teleostei (teleosts, “modern fishes”)
Actinopterygian Relationships
Holostei (gars and bowfins)
Debate of placement
Group “resurrected” based on new fossil evidence (2010)
Holostei
Gars (Lepisosteiformes)
7 species
North American distribution
Primarily freshwater but can tolerate brackish and marine
Elongated snout (ethmoid region), numerous teeth (piscivorous)
Thick ganoid scales
Air-breathers
Toxic eggs
Largest freshwater fish in N.America
Gars (Lepisosteiformes) Holostei
Bowfins (Amiiformes)
Single species (Amia calva)
Eastern North America
Freshwater lakes and rivers
Highly carnivorous; gular plate
Males construct nest & guard young
Long undulating dorsal fin, ocellus on tail
Cycloid scales
Air-breathers
Bowfins (Amiiformes) Actinopterygian Relationships II
Sarcopterygii (lobe fins)
Actinopterygii (ray fins) - Cladistia (bichirs, reedfish) - Chondrostei (sturgeons, paddlefishes) - Neopterygii -Holostei (gars, bowfins) -Teleostei (teleosts, “modern fishes”)
Actinopterygian Relationships II
Chondrichthyes CRANIATES
Sarcopterygii Vertebrates
Osteichthyes
Actinopterygii Actinopterygian Relationships II
Teleostei (“modern fishes”)
Caudal fin symmetrical – homocercal
Uroneural bones in tail support upper lobe – both lobes
Scales reduced – more flexible body
Mobile premaxilla – suction feeding capabilities
Advanced modes of locomotion and feeding, and therefore success (~24,000 species)