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Chondrichthyan Fishes (Sharks, Skates, Rays) Announcements

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Chondrichthyan Fishes (Sharks, Skates, Rays) Announcements Chondrichthyan Fishes (sharks, skates, rays) Announcements 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) 4. Lab sections done: first lab this week on Thursday! 5. First lab reading: Agassiz fish story; lab will be a bit shorter 6. Office hours: we’ll set these later this week Please use the course web site: note the various modules Outline Lecture outline: -- Intro. to chondrichthyan phylogeny -- 6 key chondrichthyan defining traits (synapomorphies) -- 3 chondrichthyan behaviors -- Focus on several major groups and selected especially interesting ones 1) Holocephalans (chimaeras or ratfishes) 2) Elasmobranchii (sharks, skates, rays) 3) Batoids (skates, rays, and sawfish) 4) Sharks – several interesting groups Not remotely possible to discuss today all the interesting groups! Vertebrate tree – key ―fish‖ groups Today Chondrichthyan Fishes sharks Overview: 1. Mostly marine 2. ~ 1,200 species 518 species of sharks 650 species of rays 38 species of chimaeras Skates and rays 3. ~ 3 % of all ―fishes‖ 4. Internal skeleton made of cartilage 5. Three major groups 6. Tremendous diversity of behavior and structure and function Chimaeras Chondrichthyan Fishes: 6 key traits Synapomorphy 1: dentition; tooth replacement pattern • Teeth are not fused to jaws • New rows move up to replace old/lost teeth • Chondrichthyan teeth are diverse in shape and size • Similar in overall structure to mammalian teeth Chondrichthyan Fishes: 6 key traits Synapomorphy 1: dentition; tooth replacement pattern Chondrichthyan Fishes: 6 key traits Synapomorphy 1: dentition; tooth replacement pattern Helicoprion Chondrichthyan Fishes: 6 key traits Synapomorphy 2: placoid scales Dermal denticles: ―tiny skin-teeth‖ or scales Chondrichthyan Fishes: 6 key traits Synapomorphy 2: placoid scales Mammalian tooth Shark scale ~130 um Chondrichthyan Fishes: 6 key traits Synapomorphy 2: placoid scales Chondrichthyan Fishes: 6 key traits Synapomorphy 2: placoid scales "riblets" Biomimetic surfaces Speedo swim suits Shark skin as inspiration Chondrichthyan Fishes: 6 key traits Synapomorphy 3: prismatic calcification of cartilage Shark cartilage is *not* like the cartilage in your body, and is also not a ―miracle cure‖ © Mason Dean Tesserae: ―Tiles‖ of mineralized cartilage Also, head skeleton (chondrocranium) has no sutures Chondrichthyan Fishes: 6 key traits Synapomorphy 4: fin structure Ceratotrichia: unsegmented bundles of collagenous fibers that make up fin rays Chondrichthyan Fishes: 6 key traits Synapomorphy 4: fin structure Ceratotrichia: unsegmented bundles of collagenous fibers Chondrichthyan Fishes: 6 key traits Synapomorphy 5: Ampullae of Lorenzini WATER Pore Canal—filled with conductive jelly Electroreceptive Cells Nerve Chondrichthyan Fishes: 6 key traits Synapomorphy 5: Ampullae of Lorenzini Passive electroreception Ampullae of Lorenzini Chondrichthyan Fishes: 6 key traits Synapomorphy 5: Ampullae of Lorenzini Ampullae of Lorenzini Chondrichthyan Fishes: 6 key traits Synapomorphy 5: Ampullae of Lorenzini Electroreception Ampulla of Lorenzini: detect electric fields Chondrichthyan Fishes: 6 key traits Synapomorphy 5: Ampullae of Lorenzini Dogfish shark: Pores extend across head Round ray (A) and Bat ray (C): Pores extend across body, cluster around mouth Chondrichthyan Fishes: 6 key traits Synapomorphy 6: Pelvic claspers in males male Internal fertilization female Chondrichthyan Fishes: 3 key elasmobranch behaviors Behavior 1: Feeding (Great) white shark Chondrichthyan Fishes: 3 key elasmobranch behaviors Behavior 1: Feeding Basking shark filter feeding Chondrichthyan Fishes: 3 key elasmobranch behaviors Behavior 1: Feeding Angel shark suction feeding Chondrichthyan Fishes: 3 key elasmobranch behaviors Behavior 2: Locomotion Tail shapes Heterocercal Homocercal Chondrichthyan Fishes: 3 key elasmobranch behaviors Behavior 2: Locomotion Spiny dogfish swimming (seen from below) Chondrichthyan Fishes: 3 key elasmobranch behaviors Behavior 2: Locomotion Bamboo shark swimming (seen from behind) Chondrichthyan Fishes: 3 key elasmobranch behaviors Behavior 3: Reproduction Great diversity in chondrichthyan reproductive patterns OVIPARITY VIVIPARITY (egg-laying) (live birth) Skates & some sharks Rays & some sharks Chondrichthyan Fishes: 3 key elasmobranch behaviors Behavior 3: Reproduction Some species exhibit Intrauterine cannibalism: most females have 2 uteri and embryophagy/oophagy occurs in each – ultimately only 1 pup born from each uterus. Ovoviparous – another reproductive mode Embryo egg eating (oophagy) Chondrichthyan Fishes: diversity Carcharhiniiformes Lamniiformes Sharks Orectolobiformes Squaliformes “other” sharks Batoidea Skates & Rays Chimaeriformes Chimaeras modified from Human et al. 2006, Molecular Phylogenetics and Evolution Chondrichthyan Fishes: diversity Group 1: Chimaeras • Holocephalians (synapomorphies = unique jaw structure, covered gills, tooth plates), also known as ratfish, ghost sharks, rabbitfish • No stomach, venomous dorsal fin spine; ever-growing tooth plates that protrude like a rodent’s incisor teeth • fossils date back to early Devonian • diverged from sharks around 400 million years ago More basic facts – see book -- poisionous dorsal spine ??? Chondrichthyan Fishes: diversity Group 1: Chimaeras Tenaculum: present in males, and used for reproduction to somehow interact with females tenaculum Movie of ratfish swimming Chondrichthyan Fishes: diversity Group 1: Chimaeras • Oviparous – gestation time unknown • no parental care • oviducal gland secretes case around fertilized egg • 2 oviducal glands produce 2 egg cases simultaneously • egg case hardens (“tans”) in seawater Fossil egg case from Cretaceous Chondrichthyan Fishes: diversity Group 2: Elasmobranchii: sharks, skates, and rays Elasmobranchii Carcharhiniiformes Lamniiformes Sharks Orectolobiformes Squaliformes “other” sharks Batoidea Skates & Rays Chimaeriformes Chimaeras modified from Human et al. 2006, Molecular Phylogenetics and Evolution Chondrichthyan Fishes: diversity Group 2: Elasmobranchii: sharks, skates, and rays Chondrichthyan Fishes: diversity Group 2: Elasmobranchii: sharks, skates, and rays Synapomorphy 1 (of 1): Unique gill structure elasmos (Greek for "metal plate") and branchus (Latin for "gill") Chondrichthyan Fishes: diversity Group 2: Elasmobranchii: sharks, skates, and rays Carcharhiniiformes Lamniiformes Sharks Orectolobiformes Squaliformes “other” sharks Batoidea Skates & Rays Chimaeriformes Chimaeras modified from Human et al. 2006, Molecular Phylogenetics and Evolution Chondrichthyan Fishes: diversity Group 3: Batoids: skates, rays, and sawfish 54 million years ago Today Batoids: a very conservative body shape over a long evolutionary time frame Chondrichthyan Fishes: diversity Group 3: Batoids: skates, rays, and sawfish Batoid anatomy: dorso-ventral compression Chondrichthyan Fishes: diversity Group 3: Batoids: skates, rays, and sawfish Chondrichthyan Fishes: diversity Group 3: Batoids: skates, rays, and sawfish ray skate What are the differences between rays (left) and skates (right)? ―The major difference between rays and skates is in their reproductive strategies. Rays are live bearing (viviparous) while skates are egg laying (oviparous), releasing their eggs in hard rectangular cases sometimes called "mermaid´s purses". Also, skates typically have a prominent dorsal fin while the dorsal fin is absent or greatly reduced in rays. ‖ ―Most rays are kite-shaped with whip-like tails possessing one or two stinging spines while skates have fleshier tails and lack spines. Rays protect themselves with these stinging spines or barbs while skates rely on thorny projections on their backs and tails for protection from predators. Skates have small teeth while rays have plate-like teeth adapted for crushing prey. Another difference is that rays are generally much larger than skates. ‖ FMNH website Chondrichthyan Fishes: diversity Group 3: Batoids: skates, rays, and sawfish Family Pristidae: ―sawfish‖ All species are critically endangered A special note on Sawfish: They are not sharks – they are rays! Chondrichthyan Fishes: diversity Group 3: Batoids: skates, rays, and sawfish Rajidae (skates) • 200 species • Size: 30cm-2.4m • Oviparous Photos, counterclockwise: Big Skate Raja binoculata, Thornback Skate Raja clavata, Skate embryo in egg case & with yolk sac. Chondrichthyan Fishes: diversity Group 3: Batoids: skates, rays, and sawfish Rhinobatidae (guitarfish) • 45 species • Size: 1.5-1.8m • Viviparous White-spotted guitarfish Rhynchobatus djiddensis Bowmouth guitarfish Rhina ancylostoma Chondrichthyan Fishes: diversity Group 3: Batoids: skates, rays, and sawfish Narcinidae & Torpedinidae: electric rays ELECTRIC ORGANS: generate electric shocks used for predation & defense • 26 species • 21 species • Size: 15-66cm • Size: up to 200 lbs! • Viviparous • Viviparous • Electric organs: generate 8-37 volts • Electric organs: in largest, can generate 220 volts! Lesser electric ray Leopard Torpedo Narcine brasiliensis Torpedo panthera Chondrichthyan Fishes: diversity Group 3: Batoids: skates, rays, and sawfish Dasystidae: stingrays • 70 species • Size: 12cm-4m • Viviparous • Most with venomous spine(s) Photos, left to right: Southern Stingray Dasyatis americana, Blue-spotted stingray Taeniura lymna Chondrichthyan Fishes: diversity Group 3: Batoids:
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