OEB 130: BIOLOGY OF FISHES Lecture 4: Overview of ray-finned fish diversity (Actinopterygii) Announcements 1 1. Please review the syllabus for reading and lab information! 2. Please do the readings: for this week posted now. 3. Lab sections: 4. i) Dylan Wainwright, Thursday 2 - 4/5 pm ii) Kelsey Lucas, Friday 2 - 4/5 pm iii) Labs are in the Northwest Building basement (room B141) Please be on time at 2pm! 4. Lab sections done: first lab this week tomorrow! 5. First lab reading: Agassiz fish story; lab will be a bit shorter 6. Office hours to come Announcements 2 8 pages of general information on fish external anatomy and characters to help you learn some basic external fish anatomy and terminology – the last slides in the uploaded lecture Powerpoint file for today. Please look at these before lab this week, but no need to bring them in with you. Scanned from: Hastings, P. A., Walker, H. J. and Galland, G. R. (2014). Fishes: A guide to their diversity: Univ. of California Press. Next Monday: prepare to draw/diagram in lecture (colored pencils/pens will be useful) Lecture outline Lecture outline: 1. Brief review of the phylogeny and key traits so far 2. Actinopterygian clade: overview and introduction to key groups and selected key traits 3. Special focus on: 1. Fin ray structure and function 2. Lung and swimblader evolution 3. Early diversity of teleost fishes Selected key shared derived characters (synapomorphies) Review from last lecture Chondrichthyes (sharks and rays and ratfishes): 1. Dentition: multiple rows of unattached teeth 2. Placoid scales: tooth-like structure 3. Prismatic (tile-like) calcification of cartilage 4. Fin structure: unsegmented fin rays termed ceratotrichia – bundles of collagen fibers 5. Ampullae of Lorenzini – sense electric fields 6. Pelvic claspers in males Selected key shared derived characters (synapomorphies) Osteichthyes (―bony fish‖ including all tetrapods): Three otoliths in the inner ear Lung or air-filled organ from ventral part of pharynx bony operculum covers the gills on each side Sarcopterygii: ―lobe fin‖ with single basal element (monobasic) intracranial joint (lost in many tetrapods) specialized scale type Actinopterygii: Single dorsal fin (some exceptions) Fin-rays termed ―lepidotrichia‖ – bilaminar design Specialized scale type (has pegs in early clades) Ray-finned fish (Actinopterygii) phylogeny: broad overview Actinopterygii Holostei Chondrichthyes Polypterus 1 and relatives Chondrostei Teleostei † Cheirolepis 1. Single dorsal fin 2. Fin ray structure: lepidotrichia 3. Scale structure Actinopterygii = ray-fin Actinopterygian synapomorphy #2: fin ray structure called a lepidotrich median and paired fins Dorsal fin A ray-finned Caudal fin fish Pectoral fins Anal fin Pelvic fins Actinopterygian synapomorphy #2: fin ray structure called a lepidotrich Ray-finned fishes have fins with unique fin rays: bilaminar, branching (usually) rays that support the fin membrane Actinopterygian synapomorphy #2: fin ray structure called a lepidotrich Ray-finned fishes have fins with unique fin rays: bilaminar, branching (usually) rays that support the fin membrane fin ray segments unsegmented basally Fin membrane Fin ray mechanics fin ray Half ray Half ray 4 muscles control each fin ray (+3) 14 fin rays in the pectoral fin; 59 muscle bundles total per fin Simple ray models Fin ray mechanics (zip-loc bag movie) A simple model fin ray Pectoral fin rays bend into flow during maneuvering Flow Fin curved into flow 14 Recall chondrichthyian synapomorphy #4: ceratotrich fin ray structure Ceratotrichia: unsegmented bundles of collagenous fibers Recall chondrichthyian synapomorphy #4: ceratotrich fin ray structure Ceratotrichia Cartilage fin supports (radials) Shark fin Another key feature of actinopterygian evolution: lungs and swimbladders Where do lungs come from, and what are key features of their evolution? Lungs are formed by ventral outpocketings from the esophagus which form air-filled cavities. The swimbladder is derived in evolution from ancestral lungs, and serves an important buoyancy function in fishes. It can also be respiratory. Swimbladder Actinopterygii Lungs Ancestral condition: gills present Sarcopterygii gills Early ray-finned fishes had lungs! The swimbladder (= gas bladder): a gas inclusion in the body cavity important for buoyancy. It arose in evolution from lungs. The swimbladder (= gas bladder): a gas inclusion in the body cavity important for buoyancy Ray-finned fish (Actinopterygii) phylogeny: broad overview Actinopterygii Holostei Chondrichthyes Polypterus 1 and relatives Chondrostei Teleostei † Cheirolepis 1. Single dorsal fin 2. Fin ray structure: lepidotrichia 3. Scale structure Actinopterygii = ray-fin Actinopterygian synapomorphy #3: scale type Actinopterygian synapomorphy #3: scale type Closely-packed rows of interlocking scales Bruet, B. J. F., Song, J., Boyce, M. C. and Ortiz, C. (2008). Materials design principles of ancient fish armour. Nature Materials 7, 748-756. Ray-finned fish (Actinopterygii) phylogeny: broad overview Actinopterygii Holostei Chondrichthyes Polypterus 1 and relatives Chondrostei Teleostei † Cheirolepis 1. Single dorsal fin 2. Fin ray structure: lepidotrichia 3. Scale structure Actinopterygii = ray-fin Early actinopterygian clades Bichirs and ropefish (Polypteriformes) Paddlefish and sturgeon (Chondrostei) Gar (Lepisosteidae) Bowfin (Amia) (Amiiformes) Bichirs and ropefish (Polypteriformes) Polypterus – ―bichirs‖, ~13+ species Bichirs and ropefish (Polypteriformes) Erpetoichthys – rope fish: 1 species Bichirs and ropefish (Polypteriformes) • There are ~13 species of bichir and they are considered the most earliest surviving branch of the ray-finned fishes. • They are heavily armored with dermal bone and a thick layer of ganoid scales. • Occur in swamps and streams in Africa and have a swim bladder that acts like a paired ventral lung. They will drown if unable to gulp air at the surface. • Because bichirs have paired fleshy pectoral fins and lungs they were formerly classified with the lungfishes, but are now considered to have evolved these traits independently. • Lung-like gas bladder – air breathing Paddlefish and sturgeon (Chondrostei -- Acipenseriformes) Chondrostei includes fossil forms Acipenseriformes – living sturgeon and paddlefish Acipenseriformes – sturgeon and paddlefish • ~25 species of sturgeon and 2 paddlefish species • Cartilaginous skeletons lacking vertebral centra • Strongly asymmetrical tail • Bony scutes on sturgeon • Sensory barbels • Mostly freshwater —few marine and anadromous sturgeon • Sturgeon prized for eggs = caviar • Caspian and Black Seas of western Asia • Stocks are collapsing in Asia, and many species endangered • Shovelnose sturgeon and pallid sturgeon • Very fecund; mature at a late age Acipenseriformes -- sturgeon Acipenseriformes -- paddlefish Acipenseriformes -- paddlefish • Paddlefish: – Lack bony scutes; long rostrum – 2 genera (each with 1 species: American (Polyodon spathula) Chinese Paddlefish (Psepherus gladius) – American: ―Spoonbill cat‖ – Mississippi, Ohio, and Missouri Rivers – Planktivore; Long, narrow gill rakers – Up to 2m in length; 75 kg – Rostrum: electrosensory function? -- rooting through sediment? Acipenseriformes -- paddlefish Paddlefish filter feeding Holostei Gar (Lepisosteidae) Holostei Gar (Lepisosteidae) • Gar are medium to large (1-4m) predatory fish with a distinctive elongated body and long jaws. • They have hard, interlocking, multilayered ganoid scales which provide excellent protection and are similar to the scales of many extinct Paleozoic and Mesozoic actinopterygians. • 7 species • Primitive predators; long jaws with sharp teeth • N. America; 1 species in Cuba • All but one freshwater • Alligator gar occasionally enters saltwater • Gas bladder/ lung divided internally • Dorsal and anal fins set far back on body • Air breathing Gar (Lepisosteidae) Flood plain dried up (2008) near the Mississippi river Photo by Andrew Carroll Gar (Lepisosteidae) Flood plain dried up (2008) near the Mississippi river Compare to fossil amphibian slab on the MCZ first floor! Photo by Andrew Carroll Holostei Bowfin (Amia) (Amiiformes) • There is only one (1) species of bowfin. • Scales are of a single layer of bone as in teleosts, but the caudal fin. • Predatory species • Can swim via undulations of the long dorsal fin • Gulping air for surviving low O2 waters • Males build and defend nests; may defend young until they are 10 cm long Ray-finned fish (Actinopterygii) phylogeny: broad overview Actinopterygii Holostei Chondrichthyes Polypterus 1 and relatives Chondrostei Teleostei † Cheirolepis 1. Single dorsal fin 2. Fin ray structure: lepidotrichia 3. Scale structure Actinopterygii = ray-fin Teleost fish phylogeny: broad overview Otocephala Elopomorpha Clupeiformes Ostariophysi (tarpons and eels) Osteoglossomorpha (“bony tongues”) Euteleostei 1. Mobile premaxilla bone in the skull 2. Specialized tail bones Teleostei Actinopterygii = ray-fin Teleost fishes (the Teleostei) • Tremendous species diversity • The swim bladder is primarily a buoyancy organ • Great diversity of body shapes • Around 30,000 species • 96% of all fishes • ~40 Orders, ~450 families Figure 24.15 • Diversification into all habitats Feb. 22th Lecture, and discussed in detail as the course progresses Selected key shared derived characters (synapomorphies) for Teleostei Teleostei: 1) Mobile premaxilla bone in head 2) Elongate bones in the tail skeleton – uroneurals (yellow in diagram below) 2 1 Teleostei: Elopomorpha (Eels,