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
~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: skates, rays, and sawfish Myliobatidae: mantas and eagle rays
• 42 species • Size: Mantas ~8m! • Viviparous • Includes LARGE filter feeders & benthic predators
Photos, counterclockwise from top left: Manta ray Manta birostris, Spotted Eagle Ray Aetobatus narinari, and Cownose Ray Rhinoptera bonasus Chondrichthyan Fishes: diversity Group 2: Elasmobranchii: sharks, skates, and rays
Selachii (sharks) 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 4: sharks Rhincodontidae: Whale shark Chondrichthyan Fishes: diversity Group 4: sharks Sphyrnidae: Hammerheads Chondrichthyan Fishes: diversity Group 4: sharks Dalatiidae: Cookiecutter shark
Isistius brasiliensis
Chondrichthyan Fishes: diversity Group 4: sharks Dalatiidae: Cookiecutter shark Chondrichthyan Fishes: diversity Group 4: sharks Dalatiidae: Cookiecutter shark Chondrichthyan Fishes: diversity Group 4: sharks Squatinidae: Angel sharks
Unusual for sharks – lower lobe of caudal fin is equal or larger than upper lobe Sit-and-wait predator (recall the suction feeding movie!) Chondrichthyan Fishes: diversity Group 4: sharks Pristiophoridae: Sawsharks
Convergent features but different from sawfish (Rajiformes): ~ smaller size ~ barbels Different from, but convergent ~ uneven, alternating sawteeth with, Pristidae, which are rays ~ gill slits on sides (not ventral)
Use snout to slash at prey Electro-receptive barbels sense prey in substrate Chondrichthyan Fishes: diversity Group 4: sharks Mitsukirinidae: Goblin shark
Mitsukurina owstoni Chondrichthyan Fishes: diversity Group 4: sharks
Mitsukirinidae: Goblin shark Chondrichthyan Fishes: diversity Group 4: sharks
Mitsukirinidae: Goblin shark Chondrichthyan Fishes: diversity Group 4: sharks Alopiidae: Thresher shark
Tail is nearly as long as the rest of the body
Hunt schooling fish by slapping and stunning them with their tails Chondrichthyan Fishes: diversity Group 4: sharks Cetorhinidae: Basking shark
Filter feeding
Up to 40 ft (12 m) long
Migrate following plankton blooms
Many historic ―sea-monster‖ sightings are thought to be basking shark remains (below from 1868) Chondrichthyan Fishes: diversity Group 4: sharks Lamnidae: Mackerel sharks; white sharks
Counter-current heat exchangers (rete mirabile) endothermy, to warm swimming musculature
White shark countershading varies by population: Grey/silver = North America Brown/copper = Australia Black = South Africa