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39 terms

Fishes

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Superclass Agnatha
Classes Myxini and Cephalaspidomorphi
Characteristics of Superclass Agnatha
lack a jaw; no paired fins; no scales; persistent notochord
Class Myxini
hagfishes
Characteristics of Class Myxini
teeth on tongue; naked skin; fibrous and cartilaginous skeleton; 2 chambered heart (ventricle, atrium) & accessory hearts; pronephric & mesonephric kidney; no stomach; nervous system (no cerebellum, eyes degenerate, 10 pairs of cranial nerves); no larval stage- direct development
Characteristics of Class Cephalaspidomorphi
no jaws (mouth with circular sucker like structure with lots of teeth); pineal eye (third eye for orientation); persistent notochord; cartilaginous skeleton; two median fins, no paired appendages; two-chambered heart (blood with specialized cells- leucocytes, nucleated erythrocytes); gills as adults; mesonephritic kidney; brain with 10 cranial nerves; small cerebellum; poikilothermic (cold blooded)
Class Chondricthyes
chimarras, sharks, rays-- The cartilaginous fishes; most primitive living vertebrates that have a complete vertebra, movable jaws, and paired appendages
Chordate characteristics of Class Chondricthyes
Persistent notochord w/cartilaginous skeleton; dorsal hollow nerve cord protected in cartilaginous skeleton; heterocercal post-anal tail; 5-7 gill arches; thyroid gland (?)
Characteristics of Class Chondricthyes
Paired pectoral and pelvic fins; Pectoral and Pelvic girdles; pelvic fins in males modified as "claspers"; two median dorsal fins
Placoid scales
scales with spiny points; are modified anteriorly to form replaceable rows of teeth- resemble teeth of higher vertebrates-- these originate from the same tissues as teeth
Other characteristics of Class Chondricthyes
Spiral valve in intestine (increases surface area & efficiency of digestion); two-chambered heart (atrium & ventricle); well developed brain with 10 sets of cranial nerves and well developed olfactory bulbs
Locomotion in Class Chondricthyes
No swim bladder or lung (can't rest suspended in water column, must swim); heterocercal tail: provides thrust & lift; paired fins: provide lift
Reproduction in Class Chondricthyes
Dioecious; gonads paired, internal fertilization; development one of three types (oviparous, ovoviviparous, viviparous)
Oviparous development
lay eggs
Ovoviviparous development
eggs retained in uterus without attachment to female
Viviparous development
eggs attach and get nutrients directly from female
Three types of kidneys in vertebrates
pronephritic, mesonephritic, metanephritic
pronephritic kidney
functional kidney of adult hagfishes and the embryos of some higher vertebrates
mesonephritic kidney
functional kidney of sharks and bony fishes; collecting duct is the Wolffian Duct, also carry sperm
metanephritic kidney
functional kidney of birds reptiles and mammals; is drained by a ureter
Sensory Systems
Nostrils (nares): not connected to mouth cavity; have two nasal sacs; lateral line system: vibrations and currents in water; Ampullae of Lorenzini: electromagnetic forces
Digestive tract
Well developed; mouth, pharynx, esophagus, stomach, liver, pancreas, intestine w/spiral valve
Osmoregulation in Chondricthyes
Ancestor of these fishes evolved in freshwater-- sea water is hyperosmotic (i.e., salt conc. of blood less than that of seawater), so they have a problem of losing water from their tissues-- to prevent water loss they retain nitrogenous wastes in blood; this elevates solute conc. in blood to be slightly higher than sea water and therefore they will not lose water passively
Advances over Agnathans
2 pairs of lateral fins; movable jaws; enamel-covered teeth; scales; 3 semicircular canals (inner ear)- agnathans had two; paired reproductive organs and ducts
Features Primitive to Bony Fishes
Cartilage skeleton; placoid scales; separate gill clefts- no operculum; spiracle to pharynx; no air bladder
Superclass Osteichthyes
bony fishes
Two subclasses in Superclass Osteichthyes
Actinopterygii (ray-finned fishes); Sarcopterygii (lobe-finned fishes)
Class Actinopterygii
bony dermal scales: ganoid, cycloid and ctenoid; notochord- persists in some, absent in others; bony skeleton & paired fins; well developed skull with 60 bones; homocercal tail; operculum covering gills- more effective respiration; 2 chambered heart, 4 pairs of aortic arches
Swim Bladders
Most Actinopterygii have a swim bladder; some have lost it-- probably evolved from lungs of primitive bony fishes
Functions of swim bladders
Can maintain position in water column w/o expending much energy; a buoyancy device
Ancestral swim bladders
were attached to the esophagus by a pneumatic duct through which air is gulped or expelled; some fish such as trout have this type of bladder
Advanced swim bladders
separate from the esophagus; gas is added by the gas gland and its rete mirabilis (the "wonderful net") and absorbed from the bladder by the ovale
Osmoregulation in Actinopterygii
mesonephritic kidney; freshwater fishes are hyperosmotic to environment- tend to gain water, lose salt; kidney produces dilute urine to eliminate excess water; gills pump salts from water to blood; marine fishes are hypoosmotic to sea water- tend to gain salt and lose water; swallow water and unwanted salts are disposed of in two ways: salt excretion by gills; salt voided with feces
Reproduction in Actinopterygii
Sexes separate; fertilization usually external- most oviparous, some ovoviviparous; some species, such as wrasses, change sexes in their lifetime
Two types of breeding migration
Anadromous, catadromous
Anadromous migration
migrating from salt water to freshwater to reproduce; spend adult life in sea; ex. salmon (born in freshwater then migrate to sea when reach adulthood migrate back to spawning grounds)
Catadromous migration
migrating from freshwater to salt water to reproduce; spend adult life in freshwater; ex. eels (born in Sargassum Sea migrate to rivers)
Feeding in Fishes
Carnivorous, herbivorous, omnivorous, filter feeders, scavengers
Fish Mouth Morphology
Allows diverse feeding niches; position of mouth: terminal, subterminal, dorsal, ventral
Class Sarcopterygii
Have a fleshy lobe at base of paired fins- precursor of appendage to support body; diphycercal tail; includes lungfishes, coelacanth