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Questions and Answers
What is the clade that includes sharks, rays, and chimaeras?
What is the clade that includes sharks, rays, and chimaeras?
Chondrichthyes
Which type of skeleton did cartilaginous fishes like sharks and rays adopt?
Which type of skeleton did cartilaginous fishes like sharks and rays adopt?
What defines a fish in modern terms?
What defines a fish in modern terms?
An aquatic vertebrate with gills, fins, and usually scales.
How many major groups of living fishes are mentioned in the text?
How many major groups of living fishes are mentioned in the text?
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Fish form a monophyletic group.
Fish form a monophyletic group.
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Hagfishes feed on annelids, molluscs, crustaceans, and __________ animals.
Hagfishes feed on annelids, molluscs, crustaceans, and __________ animals.
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What is the name of the group that includes hagfishes and lampreys?
What is the name of the group that includes hagfishes and lampreys?
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Which type of scales are characteristic of sharks and rays?
Which type of scales are characteristic of sharks and rays?
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What is the purpose of the lamprey injecting anticoagulant into a fish?
What is the purpose of the lamprey injecting anticoagulant into a fish?
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Hagfishes are attracted to live fish rather than dead or dying fish.
Hagfishes are attracted to live fish rather than dead or dying fish.
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Lampreys are known for grasping a ________ with their mouth to hold their position in current.
Lampreys are known for grasping a ________ with their mouth to hold their position in current.
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Which group of fishes has a skeleton of bone, usually absent notochord, distinct vertebrae, and jaws present?
Which group of fishes has a skeleton of bone, usually absent notochord, distinct vertebrae, and jaws present?
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Which subgroup is composed of sharks, skates, and rays?
Which subgroup is composed of sharks, skates, and rays?
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Match the following fish groups with their characteristics:
Match the following fish groups with their characteristics:
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Chondrichthyes have a ________ skeleton and their vertebrae are usually distinct.
Chondrichthyes have a ________ skeleton and their vertebrae are usually distinct.
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What is the largest shark species?
What is the largest shark species?
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Hagfishes have well-developed eyes and lampreys have poorly developed eyes.
Hagfishes have well-developed eyes and lampreys have poorly developed eyes.
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Shark finning is legal in the United States.
Shark finning is legal in the United States.
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What unique gland is attached to the short rectum of chondrichthyans?
What unique gland is attached to the short rectum of chondrichthyans?
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______ are represented by fossil fragments as early as the late Silurian period.
______ are represented by fossil fragments as early as the late Silurian period.
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Match the following shark species with their names:
Match the following shark species with their names:
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Stingrays have serrated spines with venom glands at the base.
Stingrays have serrated spines with venom glands at the base.
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Sharks have excellent vision, even in __________ lit waters.
Sharks have excellent vision, even in __________ lit waters.
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What type of endoskeleton do cartilaginous fishes of the clade Chondrichthyes have?
What type of endoskeleton do cartilaginous fishes of the clade Chondrichthyes have?
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Which species are the best known hagfishes in North America?
Which species are the best known hagfishes in North America?
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What are the three surviving genera of early neopterygians?
What are the three surviving genera of early neopterygians?
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How do many elasmobranchs prevent water from being drawn out of their bodies osmotically?
How do many elasmobranchs prevent water from being drawn out of their bodies osmotically?
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Which group of fishes has lungs and heavy ganoid scales?
Which group of fishes has lungs and heavy ganoid scales?
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Teleosts evolved from heavy, dermal armored fishes.
Teleosts evolved from heavy, dermal armored fishes.
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Match the following types of fish scales with their descriptions:
Match the following types of fish scales with their descriptions:
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What is the name of the living Australian lungfish mentioned in the text?
What is the name of the living Australian lungfish mentioned in the text?
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Where was a coelacanth found in 1938 surprising the scientific world?
Where was a coelacanth found in 1938 surprising the scientific world?
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Fish swim bladders are primarily used for respiration.
Fish swim bladders are primarily used for respiration.
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The propulsive mechanism of a fish is its trunk and tail ____________.
The propulsive mechanism of a fish is its trunk and tail ____________.
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Which of the following activities can generate heat in fishes?
Which of the following activities can generate heat in fishes?
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High temperatures in certain fish species do not promote powerful swimming.
High temperatures in certain fish species do not promote powerful swimming.
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Swimming is considered the most ______ form of animal locomotion.
Swimming is considered the most ______ form of animal locomotion.
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What is the term used to describe the ability of certain fish to maintain a high temperature in specific regions of their bodies?
What is the term used to describe the ability of certain fish to maintain a high temperature in specific regions of their bodies?
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Study Notes
Fishes
- Fishes are aquatic vertebrates with gills, appendages in the form of fins, and skin with scales of dermal origin.
- The modern concept of a fish is used for convenience, not as a taxonomic unit.
- Fishes do not form a monophyletic group, as the ancestor of land vertebrates (tetrapods) is found within one group of fishes (sarcopterygians).
Major Groups of Living Fishes
- Five major groups of living fishes:
- Hagfishes
- Lampreys
- Cartilaginous fishes (sharks, rays, and chimaeras)
- Ray-finned fishes
- Lobe-finned fishes
Evolution of Fishes
- Fishes first appeared in the early Paleozoic era, about 550 million years ago.
- Early vertebrates were an assembly of jawless agnathan fishes.
- One group of ostracoderms gave rise to the jawed gnathostomes.
Hagfishes and Lampreys
- Living jawless fishes include hagfishes and lampreys, with approximately 119 species.
- Both groups lack jaws, internal ossification, scales, and paired fins, and share porelike gill openings and an eel-like body form.
- Hagfishes and lampreys diverged from each other at least 450 million years ago.
Cartilaginous Fishes
- Cartilaginous fishes (Chondrichthyes) include sharks, rays, and chimaeras.
- They lost the heavy dermal armor of early jawed fishes and adopted cartilage for the endoskeleton.
- Most are active predators.
Ray-Finned and Lobe-Finned Fishes
- Ray-finned fishes (Actinopterygii) include nearly all familiar bony fishes.
- Lobe-finned fishes (Sarcopterygii) include lungfishes and coelacanths.
- Lobe-finned fishes are remnants of important lineages that flourished in the Devonian period.### Fish Evolution and Characteristics
- Widened areas in the lines of descent indicate periods of adaptive diversification and relative number of species in each group.
- The lobe-finned fishes (sarcopterygians) flourished in the Devonian period, but declined and are today represented by only four surviving genera (lungfishes and coelacanths).
Hagfishes (Myxini)
- Hagfishes have a distinctive body shape, with a long larval stage as an ammocoete, a disk-like buccal funnel, and slime glands.
- They have a low-pressure circulatory system served by three accessory hearts in addition to the main heart.
- Teeth are formed from keratin and are used to rasp flesh from prey.
- Hagfishes have a unique ability to generate enormous quantities of slime, which makes them difficult to grasp.
- They have a distinctive way of feeding, using their tongues to grasp and tear flesh from prey.
Lampreys (Petromyzontida)
- Lampreys are characterized by their ability to grasp a stone with their mouth to hold their position in current.
- They have a sucker-like mouth with sharp keratinized teeth, which they use to attach to fish and rasp through their flesh.
- Parasitic lampreys migrate to the sea or remain in freshwater, where they attach to fish and consume their body fluids or flesh.
- Brook lampreys are a type of lamprey that never feeds after metamorphosis and dies soon after spawning.
- Most lampreys ascend freshwater streams to breed, and males begin building a nest and are joined later by females.
Characteristics of Fish Groups
- Cyclostomata (hagfishes and lampreys) have a slender, eel-like body with no paired appendages, and their skin is naked or has keratinized plates.
- Chondrichthyes (sharks and rays) have a fusiform or dorsoventrally compressed body, with a caudal fin that is heterocercal or diphycercal.
- Actinopterygii (ray-finned fishes) have a caudal fin that is heterocercal or homocercal, and paired pectoral and pelvic fins supported by bony rays.
- Sarcopterygii (lobe-finned fishes) have a caudal fin that is heterocercal or diphycercal, and paired pectoral and pelvic fins supported by stout bones and bony rays.
Fish Characteristics
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Hagfishes have a brain that is small but distinct, with 10 pairs of cranial nerves, and eyes that are poorly developed.
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Lampreys have a brain that is moderately developed, with 10 pairs of cranial nerves, and eyes that are moderately developed.
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Fish have a range of senses, including vision, hearing, smell, and vibration reception.
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Fertilization in fish is usually external, but can be internal in some species.
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Fish have a range of reproductive strategies, including oviparity, viviparity, and ovoviviparity.
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The excretory system in fish varies, with some groups having pronephric and mesonephric kidneys, while others have opisthonephric kidneys.
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Fish have a range of gill structures, with some groups having five to seven pairs of gills, while others have a single pair of gills.### Heart Structure
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Heart with a sinus venosus, atrium, and ventricle; single circulation
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Heart with a sinus venosus, atrium, and ventricle; single circulation; nucleated red blood cells
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Heart with a sinus venosus, atrium, and ventricle; single circulation; nucleated red blood cells; pulmonary and systemic circuits incompletely separated
Lamprey
- Life cycle of the "landlocked" form
- Parasitic stage in lakes; migration toward lakes
- Filter-feeding ammocoete larvae; metamorphosis
- Attachment to fish with keratinized teeth and suction; feeding on body fluids
- Anticoagulant into the wound; nonparasitic lampreys do not feed after metamorphosis
Chondrichthyes
- Cartilaginous skeleton; calcium salts; phosphatized mineral tissues in teeth, scales, and spines
- Almost all chondrichthyans are marine; 28 species live primarily in freshwater
- Composed of two subgroups: Elasmobranchii (sharks, skates, and rays) and Holocephali (chimaeras)
Elasmobranchii
- 12 living orders; 1150 species
- Body of a dogfish shark is fusiform (spindle-shaped); asymmetrical heterocercal tail
- Paired pectoral and pelvic fins; median dorsal fin; median caudal fin
- Median anal fin present in most sharks; clasper in males; paired nostrils associated with olfaction
- Lateral eyes are lidless; spiracle behind each eye
- Five (rarely, six or seven) gill slits anterior to each pectoral fin
- Tough, leathery skin covered with toothlike, dermal placoid scales
Senses
- Highly sensitive senses; detect prey from a kilometer or more away with olfactory organs
- Detect prey at moderate distances by sensing low-frequency vibrations with mechanoreceptors
- Switch to vision as primary method of tracking prey at closer range
- Excellent vision; electroreception to find prey buried in the sand
- Ampullae of Lorenzini on the head; detect weak electric fields
Feeding
- Track prey using highly sensitive senses in an orderly sequence
- Detect prey from a kilometer or more away with olfactory organs
- Detect prey at moderate distances by sensing low-frequency vibrations with mechanoreceptors
- Switch to vision as primary method of tracking prey at closer range
- Final stage of attack guided by bioelectric fields surrounding all animals
Internal Anatomy
- Mouth cavity opens into a large pharynx; separate gill slits and spiracles
- Short, wide esophagus runs to the J-shaped stomach
- Liver and pancreas discharge their contents into a short, straight intestine
- Spiral valve slows passage of food and increases the absorptive surface
- Rectal gland secretes a fluid containing a high concentration of sodium chloride
- Paired kidneys regulate salt concentration of the blood
Reproduction
- Internal fertilization; maternal support of embryos highly variable
- Some species oviparous; lay large, yolky eggs soon after fertilization
- Some species viviparous; retain developing young in the uterus
- Ovoviviparous (lecithotrophic viviparous) species; retain developing young in the uterus while nourished by the yolk sac
- Viviparous species; embryos receive nourishment from the maternal bloodstream through a placenta or from nutritive secretions
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Description
This quiz covers the classification, anatomy, and ecology of fishes, including their phylogenetic relationships, characteristic features, and comparisons between different groups.
