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1Announcements• Aravaipa Field Trip – leave Friday 10:50 –bring camping and breakfast, lunch – cool at night• Who wants to hike?•Mexico?• No Lab Today Function = feeding• Elaboration of inertial suction feeding mechanisms. • Remember - dealing with aquatic medium (800 times more dense and 80 times more viscous than air). • Premium on effective suction and fluid propulsion mechanisms• Also oxygen less, temperature stable, hydrate, buoyancy, viscosity (more drag). • Food acquisition on land is a very different matter than that underwater.Where did jaws come from? How to study feeding?• High speed cinematography• Electromyographic analyses• Measurement of buccal cavity pressure differentials• Strain gauge analyses• = complex picture.2Chondrichthyes – Sharks, Skates, RaysChondrichthyes – Sharks, Skates, Rays• MOUTH OPENING• Lift head with epaxial muscles• Mandible pulled down by ventral muscles between hyoid and pectoral girdle and between mandible and pectoral girdle. • Enlargement of mouth/pharynx = suction•BIG GAPEChondrichthyes – Sharks, Skates, Rays• MOUTH CLOSING - ADDUCTION• Formidable bite – Large adductor mandibulae (AM) and preorbitalis muscles• AM insertion - optimized out-force at teeth• Mouth volume restored by 3 muscles -levator palatoquadrati, interhyoideus and intermandibularisFeeding in Chondricthyes3Actinopterygian Feeding - Function• Functionally Actinopterygian feeding in 3 categories:1) Ram feeding - fish overtakes food/prey by vigorous forward swimming with open mouth and opercula.2) Inertial suction - low pressure center in buccal cavity by rapid mouth opening and expansion of buccal floor. Pressure differential btw mouth and surrounding water results in flow of water into mouth. If velocity at prey is sufficiently great, prey carried into mouth.3) Manipulation - most complex - covers broad range of feeding behaviors involving use of buccal jaws (clipping, rasping scrapping and biting)._ **********FISH USE ALL*****************Evolution of Feeding• Evolution of Actinopterygian feeding mechanism shows increase in structural complexity. Cladistically derived lineages are considered structural complexity -defined as the number of connections in the structural network - increases. Feeding in Primitive Actinopterygians -Anatomy• 1. Dorsal epaxial muscles-neurocranial coupling; Elevates head• 2. Ventral coupling – (hypaxial musculature, cleithrum, sternohyoideus and hyoid apparatus) = causes mandibular depression via insertion of mandibulohyoid ligament • Mechanism for mandibular depression hypothesized to be primitive for fishes • Found also in lungfish, coelacanths and SharksPrimitive Actinopterygians4Primitive Actinopterygians• Primitive Actinopterygians(Paleoniscoids) -living Polypterids -jaw structure adapted to primarily "gripping" and "biting" habit. Next Halecostomes Feeding Mechanism AmiidaeHalecostomes Feeding Mechanism• 2 independent biomechanical pathways for mandibular depression:• 1) Primitive ventral coupling retained.• 2) New coupling = opercular series. Levitation of operculum by levator operculi muscle causes dorsal rotation of opercular series (operculum, suboperculum and interoperculum). Applied as force on mandible via interoperculomandibular ligament. • Why have two biomechanically independent pathways of mandibular depression? • Disassociation of primitive hyoid coupling from obligatory mouthopening functions allows changes in timing of hyoid depression in mouth opening. Increases versatility of control of fluid movement through buccal cavity. Next Innovation - Halecostomes1. Maxilla - primitively firmly attached to neurocranium is free and pivots on a medially directed process posterior to the vomer. • High speed cinematography in Amia - maxilla swings anterior to its pivot as mouth opens = increase velocity of water from front of mouth into oral cavityAmiidae51. Opercular Series2. MaxillaHalecostome feeding mechanism• Water is dense viscous medium = places premium in effective suction and fluid propulsion mechanisms.• Food capture first accomplished by highly effective suction mechanism. Theoretically any kind of prey or food floating or swimming in the water column - can effectively be collected by this basic feeding mechanism.• ?Corollary? - no marked specializations or adaptations in trophic apparatus are necessary to collect wide variety of aquatic organisms - irrespective of position in water column or substrate. • Fundamental dichotomy between this aquatic feeding model and basic terrestrial modelTeleosts• Teleost feeding mechanism - distinguished from primitive halecostomes by division of premaxilla into a mobile, lateral toothed portion and a medial portion associated with ethmoid complex and change in opercleconnectionsTeleosts3 major changes occurred in structural network of head.• 1) Insertion of mandibulohyoid ligament to interoperculum- effectively shifts action of hyoid and opercular couplings onto interoperculum. Only interoperculomandibularligament transmits movement to mandible in Eurypteryii -Other teleosts retain primitive two-coupling system of Halecostomes.• 2) Development of elongate ascending process on premaxilla - principally associated with jaw protrusibility.• 3) Composition of adductor mandibulae muscle complex -again associated with evolution of jaw protrusion.6TeleostMOUTH OPENINGMOUTH CLOSINGTeleosts – Other Morphological Innovations• Pharyngeal Jaws• Cyprinids, Cichlids, Labrids etc• Functional DecouplingTeleosts – Modular Multiplicity• Hardware vs Software• Patterns of Neuromuscular Firing Teleosts – Modular Multiplicity• 1. Inertial suction (is); slow and horizontal - Universal mode of feeding strategy in teleosts. Profile more-or-less identical - Live fish, daphnia, crickets, frozen brine shrimp, tetramin - all collected in this way.• 2. Inertial suction; slow and upward; any food on water surface - collected by dorsally directed suction.• 3. Inertial suction; slow down; food from bottom -collected by ventrally directed suction • 4. Biting - Extreme mouth opening and jaw protrusion• 5. Manipulation - Continuously modulated, non-cyclical pattern is most complex.7Teleosts – Modular Multiplicity• Neuromuscular Firing in Different Species • EP = epaxial, LO = levator operculi, AM = abductor mandibulae,• SH = sternohyoidiusSummarize aquatic feeding model• Fish


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UA ECOL 482 - Lecture Notes

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