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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)
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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 CRANIATES Chondrichthyes 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 CRANIATES Chondrichthyes 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
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
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)
Actinopterygian Relationships • Sarcopterygii(lobe fins) • Actinopterygii(ray fins) - Cladistia(bichirs, reedfish) - Chondrostei(sturgeons, paddlefishes) - Neopterygii -Holostei(gars, bowfins) -Teleostei(teleosts, “modern fishes”)
Neopterygii CRANIATES Chondrichthyes Sarcopterygii Vertebrates Osteichthyes Actinopterygii
Actinopterygian Relationships • Neopterygii(Holosteiand 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
Holostei • Bowfins (Amiiformes) • Single species (Amiacalva) • 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
ActinopterygianRelationships II • Sarcopterygii(lobe fins) • Actinopterygii(ray fins) - Cladistia(bichirs, reedfish) - Chondrostei(sturgeons, paddlefishes) - Neopterygii -Holostei(gars, bowfins) -Teleostei(teleosts, “modern fishes”)
ActinopterygianRelationships II CRANIATES Chondrichthyes Sarcopterygii Vertebrates Osteichthyes Actinopterygii
ActinopterygianRelationships 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)