Fishes Flashcards
Fishes are in what Phylum?
Phylum Chordata
What are Superclass Agnatha
jawless fishes
What are the 2 class of Superclass Agnatha?
Class Myxini - hagfishes
Class Petromyzontida - lampreys
Characteristics of Class Myxini (hagfishes)
-No scales or jaws – have keratinized plates
-Poorly developed eyes
-Slime glands
-Fibrous and cartilaginous skeleton
-Notochord persistent
-Vertebrae reduced or absent
Describe circulatory system of class Myxini
-Low pressure circulatory system with three accessory hearts
-Single circulatory system; main heart with sinus venosus, atrium, ventricle
Characteristics of Class Petromyzontida (Lampreys)
-No scales or jaws
-No paired appendages
-Moderately developed eyes
-Fibrous cartilaginous skeleton
-Persistant notochord; reduced vertebrae
-No stomach; spiral folds in intestine
Describe circulatory system of class Petromyzontida
-Single circulatory system; main heart with sinus venosus, atrium, ventricle
-no accessory hearts
Which class of Agnathans have:
-Sucker-like mouth withlips (sensory and attachment)
-Epidermal teeth line mouth
-Teeth cover moveable tongue-like structure
-Salivary glands secrete anticoagulant
Class Petromyzontida (Lampreys)
Explain the process of reproduction in Class Petromyzontida (Lampreys)
What are Superclass: Gnathostomata
Jawed Vertebrates
What are the 2 important events in vertebrate evolution?
- Evolution of jaws
-More efficient gill ventilation
-Ingestion of greater variety of food sources - Evolution of paired appendages
-Important to counteract roll during locomotion
-Also used to control tilt and lateral steering when swimming
Characteristics of Class Chondrichthyes
Superclass: Gnathostomata
-Biting mouthparts
-Paired appendages
-Strong swimming musculature
-Well developed sense organs
-Cartilaginous endoskeleton (no bone!)
-Phosphatized mineral tissues retained in teeth, scales, spines
What are the 2 subclasses of Class Chondrichthyes?
Subclass Elasmobranchii
Subclass Holocephali
Characteristics of Subclass Elasmobranchii
-Fusiform body; extensive fins
-Hetercercal tail – thrust
-Skin with dermal placoid scales that reduce friction
Reproduction and Development
of Subclass Elasmobranchii
-Male with modified pelvic fins = claspers
-Internal fertilization
-Various developmental modes (Oviparous, Ovoviviparous, Viviparous)
Defensive modifications of Subclass Elasmobranchii
Tail → defensive lash
Placoid scale remnants → venomous spine
Class Chondrichthyes
Subclass Holocephali Characteristics
-Large head, small mouth surrounded by large lips
-This group has specializations not found in other elasmobranchs:
-Gill cover (operculum)
-Teeth modified into large plates for crushing
-Lack scales
What are Osteichthyes?
Bony Fishes and Tetrapods
What characteristics links bony fishes and tetrapods?
-Endochondral bone
-Cranial/dental characters
-Lungs or swim bladder
What are the 2 classes of Osteichthyes?
Class Sarcopterygii – lobe-finned fishes
Class Actinopterygii – ray-finned fishes
Describe Class Sarcopterygii
-muscular lobes associated with fins
-use lungs for gas exchange
-live in areas where seasonal droughts common
Class Actinopterygii gave rise to what 3 groups?
- Clade Cladistia
- Chondrosteans
- Neopterygians
Describe Class Actinopterygii
-Over 31,000 species
-Paleoniscids (heterocercal tail, ganoid scales)
Which group of Class Actinopterygii is similar to paleoniscids?
Clade Cladistia
Which group of Class Actinopterygii is:
-Ancestral forms with bony skeleton
-Modern forms have:
cartilaginous skeletons,
tail with upper lobe
-Most live in sea; migrate to rivers to breed
Chondrosteans
Describe Neopterygians
-Modern bony fishes
-Diverged from ancient marine actinopterygians
-Underwent huge evolutionary diversification
What morphological trends that supported great diversification of the Teleost?
Flexible cycloid and ctenoid scales
Homocercal tail – speed
Flexible fins and other fin modifications
Fine control of gases in swim bladder
Suction feeding
Pharyngeal jaws – chewing, crushing, grinding
Why are fishes one of the most successful and diverse vertebrate groups?
Have been able to adapt to very demanding environment (aquatic)
1. Locomotion
2. Respiratory system
3. Highly efficient sensory systems
4. Efficient reproduction
Mechanisms for reducing friction
Streamlined shape
Mucoid secretions (lubricate body)
Buoyancy
Fishes can float due to one or more of four ways
Low density compounds incorporated into tissues (oily livers; squalene)
Fins provide lift (pectoral fins or upper lobe of caudal fin)
Reduction of heavy tissues in body
Less dense bones/cartilaginous skeletons
Swim bladder
Controls volume of gas within
How does gas get into swim bladder?
Gas gland lactic acid localized acidity of blood in rete mirabile hemoglobin releases O2 load counter-current multiplier high O2 in gas gland diffusion into swim bladder
How fishes achieve neutral buoyancy?
displace additional water by a volume of gas in swim bladder
Can then remove gas in swim bladder via
Pneumatic duct (ancestral physostomous condition) or
Ovale (derived physoclistous condition)
Fish Circulation and its disadvantage
Single circuit circulation
Disadvantage: gill capillaries give high resistance so blood pressure to body tissues is low
Explain gas exchange in fish
Pumping action by operculum helps move water through gills (continuous flow)
Water pumped into mouth and pharynx → over gills → out gill openings
Explain Sensory Functions of fish
Have specialized receptors for olfaction, vision, hearing, equilibrium and balance and detecting water movements
unique to fishes and used to detect water currents or predators/prey causing water movements
Lateral line system
sensory pits in epidermis of skin connecting to canals running just below epidermis
Lateral line system
Describe Reproduction and Development
of Fish
Most fish are:
Dioecious
External fertilization
Oviparous
Eggs develop outside female from stored yolk
