Fish%20Diversity:%20Osteichthyes,%20Part%201

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Fish DiversityOsteichthyes, Part 1

• Marine Vertebrates Lecture 2

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Fish phylogeny
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Class OsteichthyesMajor features

• Lung and lung derivatives

Dorsal, with ventral connection to gut Early
ray-finned fishes
Ventral, with ventral connection to gut Remained
this way for tetrapod ancesters
Dorsal, with dorsal connection to gut Some
ray-finned fishes
Physostomous connection with gut (as seen
above) Physoclistous no connection with gut
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Class OsteichthyesMajor features

• Bone at least some ossification
• Lepidotrichia support of soft rays of fins
• segmented and flexible (compare to Ceratotrichia)
• Scales

Ganoid
Cycloid
Ctenoid
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Focus Subclass SarcopterygiiLobe-finned fishes
Fins linked to pelvic girdle
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Focus Subclass SarcopterygiiLobe-finned fishes

• Overview
• Similarities with tetrapods
• Fins articulated with pelvic girdle
• Jaw and tooth structure similar
• Groups
• Dipnomorpha (lungfishes) freshwater!
• Actinista (Coelacanths)

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Focus Actinista Coelacanths

• Discovery
• Features skeleton, osmotic regulation, swim
  bladder, reproduction

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Coelacanth behavior
Photo M. Erdmann
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Subclass ActinopterygiiRay-finned fishes
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Infraclass ChondrosteiSturgeon
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Infraclass ChondrosteiSturgeon

• Five rows of bony scales (ganoid or rhomboid)
• Secondarily cartilagenous skeletons
• Some with spiracles/spiracle remnants
• Spiral valve present
• Heterocercal tail
• No teeth (so how do they eat?)
• Sensory barbels, electrical sense
• Long, slow growth high fecundity
• Caviar sturgeon roe

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Infraclass Teleostii

• Most modern Actinopterygii are teleosts
• 23,681 species
• Derived characters
• Bone in scales reduced
• No spiracles
• Homocercal tail
• Other skeletal aspects