TY - JOUR
T1 - Morphology of a picky eater
T2 - A novel mechanism underlies premaxillary protrusion and retraction within cyprinodontiforms
AU - Hernandez, L. Patricia
AU - Ferry-Graham, Lara A.
AU - Gibb, Alice C.
N1 - Funding Information:
We thank the following people for the loaning of specimens used in this study (and for specimens ultimately not included): Lynne Parenti (Smithsonian Institution), Philip Motta (University of South Florida), Dave Catania (California Academy of Sciences), Daphne Gehringer (Moss Landing Marine Labs). We also thank Nathan Bird and Katie Staab for assistance with specimen preparations at GWU. LPH was supported by NSF IOS-0615827, IOS-0726087 and DBI-0721662. LFG was supported by NSF MRI-0320972 and IOS-0726081; ACG was supported by NSF IOS-0726001 and Science Foundation Arizona CAA 0057-07.
PY - 2008/10/1
Y1 - 2008/10/1
N2 - Upper jaw protrusion is hypothesized to improve feeding performance in teleost fishes by enhancing suction production and stealth of the feeding event. However, many cyprinodontiform fishes (mid-water feeders, such as mosquitofish, killifish, swordtails, mollies and pupfish) use upper jaw protrusion for "picking" prey out of the water column or off the substrate; this feeding mode may require improved jaw dexterity, but does not necessarily require increased stealth and/or suction production. We describe functional aspects of the bones, muscles and ligaments of the anterior jaws in three cyprinodontiform genera: Fundulus (Fundulidae), Gambusia and Poecilia (Poeciliidae). All three genera possess a premaxillomandibular ligament that connects the premaxilla of the upper jaw to the mandible. The architecture of this ligament is markedly different from the upper-lower jaw connections previously described for basal atherinomorphs or other teleosts, and this loose ligamentous connection allows for more pronounced premaxillary protrusion in this group relative to closely related outgroup taxa. Within poeciliids, a novel insertion of the second division of the adductor mandibulae (A2) onto the premaxilla has also evolved, which allows this jaw adductor to actively retract the premaxilla during mouth closing. This movement is in contrast with most other teleosts, where the upper jaw is retracted passively via pressure applied by the adduction of the lower jaw. We postulate that this mechanism of premaxillary protrusion mediates the cyprinodontiforms' ability to selectively pick specific food items from the water column, surface or bottom, as a picking-based feeding mechanism requires controlled and coordinated "forceps-like" movements of the upper and lower jaws. This mechanism is further refined in some poeciliids, where direct muscular control of the premaxillae may facilitate picking and/or scraping material from the substrate.
AB - Upper jaw protrusion is hypothesized to improve feeding performance in teleost fishes by enhancing suction production and stealth of the feeding event. However, many cyprinodontiform fishes (mid-water feeders, such as mosquitofish, killifish, swordtails, mollies and pupfish) use upper jaw protrusion for "picking" prey out of the water column or off the substrate; this feeding mode may require improved jaw dexterity, but does not necessarily require increased stealth and/or suction production. We describe functional aspects of the bones, muscles and ligaments of the anterior jaws in three cyprinodontiform genera: Fundulus (Fundulidae), Gambusia and Poecilia (Poeciliidae). All three genera possess a premaxillomandibular ligament that connects the premaxilla of the upper jaw to the mandible. The architecture of this ligament is markedly different from the upper-lower jaw connections previously described for basal atherinomorphs or other teleosts, and this loose ligamentous connection allows for more pronounced premaxillary protrusion in this group relative to closely related outgroup taxa. Within poeciliids, a novel insertion of the second division of the adductor mandibulae (A2) onto the premaxilla has also evolved, which allows this jaw adductor to actively retract the premaxilla during mouth closing. This movement is in contrast with most other teleosts, where the upper jaw is retracted passively via pressure applied by the adduction of the lower jaw. We postulate that this mechanism of premaxillary protrusion mediates the cyprinodontiforms' ability to selectively pick specific food items from the water column, surface or bottom, as a picking-based feeding mechanism requires controlled and coordinated "forceps-like" movements of the upper and lower jaws. This mechanism is further refined in some poeciliids, where direct muscular control of the premaxillae may facilitate picking and/or scraping material from the substrate.
KW - Adductor mandibulae
KW - Cyprinodontiformes
KW - Feeding mechanism
KW - Poeciliidae
KW - Premaxilla
UR - http://www.scopus.com/inward/record.url?scp=50149100334&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=50149100334&partnerID=8YFLogxK
U2 - 10.1016/j.zool.2007.12.002
DO - 10.1016/j.zool.2007.12.002
M3 - Article
C2 - 18640016
AN - SCOPUS:50149100334
SN - 0944-2006
VL - 111
SP - 442
EP - 454
JO - Zoology
JF - Zoology
IS - 6
ER -