The Fishes: Vertebrate Success in Water

Chapter 18

• Phylogenec Relaonships – Subphylum Craniata • Skull surrounds brain, olfactory organs, eyes, and inner ear. • Infraphylum Hyperotre • Infraphylum Vertebrata – Fossils record • Craniates and bone date earlier than 500 mya.

• Infraphylum Hyperotre—Class Myxini (Hagﬁshes) – Head supported by carlaginous bars – Lack vertebrae and retain notochord for axial support – 4 pairs of sensory tentacles around mouth – Ventrolateral slime glands – Marine – Scavenge dead and dying ﬁsh – Likely most primive group of craniates

Copyright © 2016 McGraw-Hill Educaon. All rights reserved. No reproducon or distribuon without the prior wrien consent of McGraw-Hill Educaon. Survey of Fishes Figure 18.5 Arst’s Rendering of an Ancient Silurian Seaﬂoor. • Infraphylum Vertebrata – Vertebrae surround nerve cord & provide axial support – Ostracoderms • Exnct agnathans • Bony armor • Boom dwellers

• Class Petromyzonda – Lampreys – Marine and freshwater – Most are predators as adults, ﬁlter-feeders as larvae – Life cycles involve open water adult stages and stream or river larval stages (ﬁgure 18.7).

Copyright © 2016 McGraw-Hill Educaon. All rights reserved. No reproducon or distribuon without the prior wrien consent of McGraw-Hill Educaon. Survey of Fishes • Superclass Gnathostomata – Jaws developed from anterior pharyngeal arches. – Paired appendages – Classes of gnathostomes • Carlaginous – Chondrichthyes • Bony – Acnopterygii – Sarcopterygii

Figure 18.8 Paired Pectoral and Pelvic Appendages.

Copyright © 2016 McGraw-Hill Educaon. All rights reserved. No reproducon or distribuon without the prior wrien consent of McGraw-Hill Educaon. Survey of Fishes • Class Chondrichthyes – Placoid scales, carlaginous endoskeleton – Subclass Elasmobranchii • Sharks, skates, rays – Subclass Holocephali • Raish • Diverged from other chondrichthians 350 mya • Operculum present

Copyright © 2016 McGraw-Hill Educaon. All rights reserved. No reproducon or distribuon without the prior wrien consent of McGraw-Hill Educaon. Figure 18.9 Class Chondrichthyes. (a) and (b) Subclass Elasmobranchii. (a) Caribbean reef shark (Carcharhinus perezi). (b) A bluespoed ribbontail ray (Taeniura lymma). (c) Subclass Holocephali. The raish (Hydrolagus colliei).

• Class Sarcopterygii – Lobe-finned fishes • Fins with muscular lobes – Lungs used in gas exchange. – Lungfish • 3 genera • Australia, Africa, South America – Coelacanths • 2 species • African and Indonesian coasts – Tetrapodomorpha • Exnct ancestors of ancient amphibians and all tetrapods

Figure 18.11 Class Sarcopterygii. The Queensland lungﬁsh, Neoceratodus forsteri.

• Class Acnopterygii – Ray-finned fishes • Fins lack muscular lobes – Swim bladders – Chondrosteans • Sturgeons and paddlefish – Carlaginous skeletons – Neopterygii • Garpike (Lepisosteus) and dogfish or bowfin (Amia) • Modern bony fishes—the teleosts

Copyright © 2016 McGraw-Hill Educaon. All rights reserved. No reproducon or distribuon without the prior wrien consent of McGraw-Hill Educaon. Figure 18.13 Class Acnopterygii, the Chondrosteans. (a) Shovelnose sturgeon (Scaphirhynchus platorynchus). (b) Paddleﬁsh (Polydon spathula).

Copyright © 2016 McGraw-Hill Educaon. All rights reserved. No reproducon or distribuon without the prior wrien consent of McGraw-Hill Educaon. Figure 18.14 Class Acnopterygii, the teleosts. (a) A winter ﬂounder (Pseudopleuronectes americanus). (b) Yellowtail snappers (Ocyurus chrysurus). (c) The sarcasc fringehead (Neoclinus blanchardi)

• Locomoon – Streamlined shape, mucoid secreons, buoyancy of water, body-wall muscles, fin shape all promote efficient locomoon. • Nutrion and the digesve system – Filter feeders and scavengers • Earliest fishes • Modern filterers use gill rakers – Predators (most modern fish) • Swallow food whole – External parasites (lampreys) – Herbivores – Digesve tract • Specializaons include spiral valve (sharks) and pyloric ceca (bony fishes).

Copyright © 2016 McGraw-Hill Educaon. All rights reserved. No reproducon or distribuon without the prior wrien consent of McGraw-Hill Educaon. • Circulaon – Closed circulatory system – Heart • 4 embryological enlargements of ventral aorta – Sinus venosus – Atrium – Ventricle – Conus arteriosus – Most ﬁsh have single circuit. – Lungﬁsh • Pulmonary circulaon • Pulmonary and systemic circuits

Copyright © 2016 McGraw-Hill Educaon. All rights reserved. No reproducon or distribuon without the prior wrien consent of McGraw-Hill Educaon. • Gas exchange – Water movement over gills • Opercular and pharyngeal muscles pump water in most fishes. • Ram venlaon in elasmobranchs and open-ocean bony fish – Gas exchange surfaces • Gill (visceral) arches support gills • Gill filaments and pharyngeal lamellae – Countercurrent exchange mechanism (figure 18.16)

Copyright © 2016 McGraw-Hill Educaon. All rights reserved. No reproducon or distribuon without the prior wrien consent of McGraw-Hill Educaon. Figure 18.16 Gas Exchange at the Pharyngeal Lamellae. (a) Gill arches. (b) Flounder gill ﬁlament with numerous lamellae. (c and d) Comparison of countercurrent and parallel exchanges.

Copyright © 2016 McGraw-Hill Educaon. All rights reserved. No reproducon or distribuon without the prior wrien consent of McGraw-Hill Educaon. • Swim bladders and lungs – Pneumac sacs connect to digesve tract in nonteleost fish. • Funcon as lungs in lung fish, climbing perch and ancient rhipidisans • Funcon as swim bladders in other bony fish • Buoyancy Regulaon – use 1 or more of 4 possible strategies 1. Low density compounds 2. Fins provide vercal li 3. Reducon of heavy ssues 4. Swim bladders

Copyright © 2016 McGraw-Hill Educaon. All rights reserved. No reproducon or distribuon without the prior wrien consent of McGraw-Hill Educaon. Figure 18.17 Possible Sequence in the Evoluon of Pneumac Sacs. (a) Origin as ventral outgrowths of esophagus. (b) Primive lungs. (c) Swim bladders move dorsal in posion and lose connecon to gut tract.

Copyright © 2016 McGraw-Hill Educaon. All rights reserved. No reproducon or distribuon without the prior wrien consent of McGraw-Hill Educaon. • Nervous and sensory funcons – Brain and spinal cord – Sensory receptors • External nares • Eyes – Lidless and round lens • Inner ears – Equilibrium, balance, and hearing • Lateral line system – Sensory pits in skin detect water movements. • Electrorecepon – Prey detecon by chondrichthyians – Gymnarchus (ﬁgure 18.18) – Electrophorus (electric eel)

Copyright © 2016 McGraw-Hill Educaon. All rights reserved. No reproducon or distribuon without the prior wrien consent of McGraw-Hill Educaon. Figure 18.18 Electric Fishes. (a) Electrical ﬁelds are used to detect the presence of prey and other objects in a murky environment. (b) The electric ﬁsh (Gymnarchus nilocus).

Copyright © 2016 McGraw-Hill Educaon. All rights reserved. No reproducon or distribuon without the prior wrien consent of McGraw-Hill Educaon. • Excreon and Osmoregulaon – Kidneys • Filter nitrogenous wastes, ions, water, and small organic compounds at nephrons – Glomerulus is a filtering capillary network – Tubule system promotes reabsorpon • Freshwater fishes – Excess water must be excreted. – Ions and organic compounds are selecvely reabsorbed. • Marine fishes – Water must be conserved. – Excess ions excreted.

Copyright © 2016 McGraw-Hill Educaon. All rights reserved. No reproducon or distribuon without the prior wrien consent of McGraw-Hill Educaon. Figure 18.20 Osmoregulaon by (a) Freshwater and (b) Marine Fishes. Large arrows indicate passive uptake or loss of water or electrolytes through ingeson and excreon. Small solid arrows indicate acve transport. Small, open arrows indicate passive uptake or loss by diﬀusion through permeable surfaces.

Copyright © 2016 McGraw-Hill Educaon. All rights reserved. No reproducon or distribuon without the prior wrien consent of McGraw-Hill Educaon. • Excreon and Osmoregulaon – Diadromous ﬁshes • Migrate between freshwater and marine environments • Gills cope with both uptake and excreon of ions. – Nitrogen wastes • 90% ammonia (diﬀusion across gill surfaces) • 10 % urea, creane or creanine (excreted by kidneys)

Copyright © 2016 McGraw-Hill Educaon. All rights reserved. No reproducon or distribuon without the prior wrien consent of McGraw-Hill Educaon. • Reproducon and development – Most oviparous • ovoviviparous • viviparous – Ferlizaon • Most external • Copulatory structures – Claspers in elasmobranch males – Development • Usually lile or no parental care • Some tend nests or brood young

Copyright © 2016 McGraw-Hill Educaon. All rights reserved. No reproducon or distribuon without the prior wrien consent of McGraw-Hill Educaon. Figure 18.21 Male Garibaldi (Hypsypops rubicundus). Culvates a nest of red algae, ences a female to lay eggs in the nest, and defends the nest.