Announcements 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 1 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 2 Chondrichthyes Sharks Skates Rays Chondrichthyes 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 GAPE 3 Chondrichthyes 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 intermandibularis Feeding in Chondricthyes 4 Actinopterygian 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 5 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 Sharks Primitive Actinopterygians 6 Primitive Actinopterygians Primitive Actinopterygians Paleoniscoids living Polypterids jaw structure adapted to primarily gripping and biting habit Next Halecostomes Feeding Mechanism Amiidae 7 Halecostomes 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 mouth opening functions allows changes in timing of hyoid depression in mouth opening Increases versatility of control of fluid movement through buccal cavity Next Innovation Halecostomes 1 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 cavity Amiidae 8 1 Opercular Series 2 Maxilla Halecostome 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 model 9 Teleosts 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 opercle connections Teleosts 3 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 interoperculomandibular ligament 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 10 Teleost MOUTH OPENING MOUTH CLOSING Teleosts Other Morphological Innovations Pharyngeal Jaws Cyprinids Cichlids Labrids etc Functional Decoupling 11 Teleosts 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 12 Teleosts Modular Multiplicity Neuromuscular Firing in Different Species EP epaxial LO levator operculi AM abductor mandibulae SH sternohyoidius Summarize aquatic feeding model Fish feeding apparatus truncated cone or cylinder Suction is generated when cone expands Dense aquatic medium and expanding cone suction generating device extremely versatile feeding model taxonomic ecological diversity of prey collected by suction in single teleost species unsurpassed by any feeding Versatility of expanding cone model restricted not only to prey capture Pressure differences in different areas