Gnathostomes fishes (1) Chondrichthyes
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GNATHOSTOMES FISHES (1) Chondrichthyes
Two major innovations make this group successful: jaws developed from the first gill arch paired appendages (fins) These two characteristics allowed them to become predaceous jaws allowed them to catch and consume prey paired appendages gave fishes more maneuverability - fins add stability and control there is no good indication for the origin of appendages - one simply the fin-fold theory Gnathostomes developed into a number of clades: Ancestral gnathostomes =>
Class CHONDRICHTHYES - CARTILAGENOUS FISHES skeleton composed of calcified cartilage bone is thought to be more primitive to cartilage 500-700 species; almost all marine have jaws and paired appendages have 5-7 external gill openings or gill slits and one reduced gill called a spiracle or false gill no swim bladder internal fertilization may be viviparous, oviparous, or ovoviviparous Two Parental Clades for Chondrichthyes Subclass Elasmobranchii
Elasmobranchii subdivided into two groups: pleurotremata (“side hole”) - refers to location of gills on the side of the head: sharks hypsotremata (“below hole”) - refers to location of gills on the ventral surface: rays and skates gills of both groups ventilated by a double pump and by the spiracles in some sharks ventilation requires a continuous movement for water to pass over the gills sharks lack a swim bladder; have an oil (squalene) produced by the liver which acts as a density control device by adjusting overall body density PRIMARY REPRODUCTIVE PATTERNS Oviparous - egg layers Ovoviviparous - live birth during development the young are nourished by the yolk when the egg is fertilized, it has a large yolk and the embryo develops in the uterus while obtaining nutrient from the stored yolk Viviparous - live birth young receive nourishment from some type of placental attachment nourishment comes from the mother’s blood, secretions, or other tissues Generalized Classification of Elasmobranchii: Order Squalimorphes (Squaloids) - spring and green dogfish sharks, basking and megamouth sharks
Order Galeomorphs (Galeoids) - contains most of the sharks ~250 species all with five gill openings dominant carnivores of shallow waters hammerhead, great white, whale shark Order Batoidea (Rajiformes)- skates and rays ~425 species skates have pointed nose and lay eggs, rays give live birth Family: Echinorhinidae - Bramble sharks Order: Squalimorphes (bramble, sleeper and dogfish sharks) Subclass: Elasmobranchii - sharks and rays Large (3-4 m), wide-ranging, deepwater sharks in cold-temperate to tropical seas. Circumglobal distribution on continental and insular shelves and slopes from 11 to 900 m, on or near the bottom. Short-nosed, cylindrical sharks with no anal fin Skin covered with coarse denticles or enlarged thorns Feed on a variety of benthic and neritic fishes, including other sharks as well as crabs, octopuses and squids Thought to suck in their prey by suddenly expanding their mouths and pharynxes when in range Ovoviviparous and lack a yolk sac placenta Family: Squalidae - Dogfish sharks Order: Squalimorphes (bramble, sleeper and dogfish sharks) Subclass: Elasmobranchii (sharks and rays) Atlantic, Indian and Pacific Oceans No lateral teeth or barbels. Dorsal fin with or without spines 5 gill openings anterior to pectoral fin Maximum length at 6.3 m, reported for Somniosus microcephalus This family includes the smallest sharks in the world. Family: Ginglymostomatidae - Nurse sharks SubOrder: Orectolobiformes (carpet sharks) Order Squalimorphes Subclass: Elasmobranchii (sharks and rays) Marine, all oceans. Small to large sharks with nasoral grooves, short to long barbels, small spiracles behind eyes. Two spineless fins and an anal fin Common, small to large, nocturnal, inshore bottom sharks with a circumglobal distribution in subtropical and tropical waters, in depths from the intertidal down to at least 70 m. Cruise and clamber on the bottom with their mouths and barbels close to the substrate while searching for food. They use their short, small mouths and large mouth cavities as a bellows to suck in their prey: bony fish, crabs, shrimps, lobsters, squids, octopuses, corals, sea urchins, sea squirts. Family: Cetorhinidae - Basking sharks Order: Squalimorphes Subclass: Elasmobranchii (sharks and rays) Marine, all oceans, highly migratory. Gill openings exceptionally large; gill rakers elongate, plankton feeders, teeth reduced. The tail is nearly symmetrical with keel on caudal peduncle. Fifth gill opening in front of pectoral fin. The family contains the world's second largest fish, reportedly reaching 40 feet (12 m) in TL. Family: Sphyrnidae - Hammerhead, Bonnethead, and Scoophead sharks SubOrder: Carchariniformes (ground sharks) Order Galeomorphes Subclass: Elasmobranchii (sharks and rays) Marine, coastal; occasionally in brackish water. Global (chiefly warm waters). Head laterally expanded, with eyes and nasal openings much widely set than in other sharks. No spiracle. A maximum length of 4.5 m was reported for Sphyrna tudes. Feed on a wide variety of bony fish, elasmobranchs, cephalopods, crustaceans, and other prey. Family: Lamnidae - Mackerel sharks, White sharks SubOrder: Lamniformes (mackerel sharks) Order Galeomorphes Subclass: Elasmobranchii (sharks and rays) Distribution: global. Large sharks with pointed snouts and spindle-shaped bodies. Large gill openings. First dorsal fin large, high, erect and angular or somewhat rounded; second dorsal and anal fins minute. Caudal peduncle with a distinct keel; large teeth; fifth gill opening in front of pectoral fin; spiracle sometimes absent. Maximum length up to 6.4 m or more. Fast swimming predators - some are man-eaters. Ovoviviparous without a yolk-sac placenta but with uterine cannibalism. Family: Pristidae - Sawfishes SubOrder: Pristiformes (sawfishes) Order Galeomorphes Subclass: Elasmobranchii (sharks and rays) Atlantic, Indian, and Pacific Oceans. Snout elongated into a long flat blade with teeth of uniform size deeply embedded on each side. No barbels. Head depressed with the body more or less resembling a shark. Two distinct dorsal fins. Giant fishes of coastal waters, entering estuaries and ascending large rivers for great distances. Used for food and regarded as exciting game fishes because of their size. Although generally harmless to humans, their large size and sawlike beak make them dangerous when hooked or speared. Of the many nominal species only four appear to be valid. Family: Rajidae - Skates Order: Rajiformes (skates and rays) Subclass: Elasmobranchii (sharks and rays) Benthic rays occurring in all oceans, from Arctic to Antarctic waters and from shallow coastal shelves to abyssal regions; some species enter brackish waters. Disc quadrangular to rhomboidal. Mouth transversed to arched, with numerous teeth. Five pairs of ventral gill slits. Tail very slender, with lateral folds, usually 2 reduced dorsal fins and a reduced caudal fin. Electric organs weak, developed from caudal muscles. Skin prickly in most species, the prickles often in a row along midline of dorsal. Oviparous; eggs in a horny capsule with four long tips. Skates feed on other benthic organisms. Skate wings are considered good eating. Family: Anacanthobatidae - Smooth skates Order: Rajiformes (skates and rays) Subclass: Elasmobranchii (sharks and rays) Known from South Africa, Natal, and the tropical western Atlantic; also from Taiwan. A terminal filament of varying length arising from a small, bluntly rounded protuberance at the tip of the snout. Dorsal fins absent, but membranous caudal fin present. Five pairs of small, ventral gill slits. Dorsal and ventral surfaces of disc smooth, without dermal denticles. Tail slender, a bit shorter than disc. Small skates of slope regions in tropical/subtropical waters. Family: Platyrhinidae - Thornbacks Order: Rajiformes (skates and rays) Subclass: Elasmobranchii (sharks and rays) Atlantic, Indian and Pacific Oceans. Body form intermediate between that of a shark and a skate. Tail stout, not well demarcated from body. Dorsal fins 2; distinct. Caudal fin present. Denticles arranged in a row on dorsal midline. No spine in tail. Family: Rhinobatidae - Guitarfishes Order: Rajiformes (skates and rays) Subclass: Elasmobranchii (sharks and rays) Atlantic, Indian and Pacific Oceans mostly in tropical coastal waters. Body form intermediate between that of a shark and a skate. Also called shovelnose sharks. Numerous small, blunt teeth in jaws. Two large dorsal fins; caudal fin well developed. Denticles arranged in a row on dorsal midline. No spine in tail. They reach moderate to large size and are important commercial species in many coastal nations. Ovoviviparous. Feed on bottom organisms, including mollusks and crustaceans, but will also take small fishes. Family: Dasyatidae - Sting rays SubOrder: Myliobatiformes (eagle rays, stingrays and mantas) Order: Rajiformes Subclass: Elasmobranchii (sharks and rays) Chiefly marine; also in brackish and freshwater - Atlantic, Indian and Pacific Oceans. Side of head continuous with anterior margin of pectoral fin. Dorsal fin totally absent or indistinct, when present. Disc about 1.2 times as broad as long. No caudal fin. Tail long and whip-like. Most species with at least 1 long venomous spine on tail, which can cause excruciating pain to humans. Largest species to about 4m length or width. Live-bearing (ovoviviparous). Family: Mobulidae - Manta rays and devil rays SubOrder: Myliobatiformes (eagle rays, stingrays and mantas) Order: Rajiformes Subclass: Elasmobranchii (sharks and rays) Atlantic, Indian and Pacific Oceans. Head differentiated from disc. Eyes and spiracles on sides of head. Mouth ventral in Mobula and terminal in Manta. Size of gill openings almost the length of eye. Length of tail much greater than disc. Some with spines. Dorsal fin small. Caudal fin lacking. Three functional paired limbs. The cephalic pair of fins aid in feeding and are said to be essentially the anterior subdivision of the pectorals. Some reach about 6.1 m and weigh over 1360 kg. Subclass Holocephali chimaeras or ratfish ~25 species gills covered by an operculum no placoid scales Chimaeridae - Chimaeras or ratfishes Order: Chimaeriformes Subclass: Holocephali Atlantic, Pacific, and Indian oceans in temperate to tropical waters, mostly below 200 m Short and rounded snout First dorsal fin erectile, with a strong spine; second dorsal fin long and low Diphycercal tail - vertebral column runs straight to the tip, dividing the caudal fin symmetrically Anal fin confluent with caudal fin in Hydrolagus ; separate in Chimaera Feed on small fishes and bottom invertebrates Males with head clasper Oviparous; large tadpole-shaped egg capsules are deposited on substrate Dorsal spine with associated poison gland, the venom of which hurts humans Family: Rhinochimaeridae - Longnose chimaeras Remark: Found at scattered localities worldwide in temperate and tropical seas, in 200 to more than 2,000 m depth. Long and pointed snout, lacking a hooklike process. First dorsal fin erectile, with a strong, mildly toxic spine; second dorsal fin long, low and not falcate. Diphycercal tail, i.e., the vertebral column is extending to the tip and divides the caudal fin symmetrically; caudal fin may be confluent with or separate from anal fin. Oviparous: egg-cases spindle-shaped, with broad filamentous horizontal flanges Directory: biol -> 308 -> casaiud -> text biol -> For Thursday Nov 13th Students will choose one side of this assignment page biol -> For Thursday Dec 9th Students will choose one side of this assignment page. The Adaptationist Program Discussion biol -> Discussion Questions regarding the Adaptationist Program biol -> Activity How can fossil and rock data determine when an organism lived? 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