Crocodylians evolved some of the most characteristic skulls of the animal kingdom with specializations for semiaquatic and ambush lifestyles, resulting in a feeding apparatus capable of tolerating high biomechanical loads and bite forces and a head with a derived sense of trigeminal‐nerve‐mediated touch. The mandibular symphysis accommodates these specializations being both at the end of a biomechanical lever and an antenna for sensation. Little is known about the anatomy of the crocodylian mandibular symphysis, hampering our understanding of form, function, and evolution of the joint in extant and extinct lineages. We explore mandibular symphysis anatomy of an ontogenetic series of
Living gars are a small clade of seven species that occupy an important position on the actinopterygian phylogenetic tree as members of Holostei, sister‐group to teleosts, and exhibit many plesiomorphic traits used to interpret and reconstruct early osteichthyan feeding mechanisms. Previous studies of gar feeding kinematics have focused on the ram‐based, lateral‐snapping mode of prey capture found in the narrow‐snouted
- PAR ID:
- 10372569
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Journal of Morphology
- Volume:
- 280
- Issue:
- 10
- ISSN:
- 0362-2525
- Page Range / eLocation ID:
- p. 1548-1570
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
ABSTRACT using imaging, histology, and whole mount methods. Complex sutural ligaments emanating about a midline‐fused Meckel's cartilage bridge the symphysis. These tissues organize during days 37–42 ofAlligator mississippiensis in ovo development. However, interdigitations do not manifest until after hatching. These soft tissues leave a hub and spoke‐like bony morphology of the symphyseal plate, which never fuses. Interdigitation morphology varies within the symphysis suggesting differential loading about the joint. Neurovascular canals extend throughout the mandibles to alveoli, integument, and bone adjacent to the symphysis. These features suggest theAlligator mandibular symphysis offers compliance in an otherwise rigid skull. We hypothesize a fused Meckel's cartilage offers stiffness in hatchling mandibles prior to the development of organized sutural ligaments and mineralized bone while offering a scaffold for somatic growth. The porosity of the dentaries due to neurovascular tissues likely allows transmission of sensory and proprioceptive information from the surroundings and the loaded symphysis. Anat Rec, 302:1696–1708, 2019. © 2019 American Association for Anatomy -
Laboratory constraints on feeding behaviours in polymorphic bluegill sunfish ( Lepomis macrochirus )
Abstract Evaluating fish feeding behaviours is imperative to understanding prey resource use in the field. Previous work on fish feeding has taken place almost exclusively in a laboratory setting, which may impose artificial restrictions. Thus, we aimed to evaluate the constraints the captive setting places on fish feeding behaviours.
We recorded polymorphic (littoral and pelagic) bluegill sunfish (
Lepomis macrochirus ) feeding in the laboratory and the field using a high‐speed camera and underwater cameras. Following successful strikes video events, were digitised using ImageJ (laboratory) and Argus (field).Gape velocity, ram velocity, and body deceleration were higher in the field than in captive fish. Significantly greater gape velocity in field fish suggests that these fish feed with greater suction pressure than captive fish. Prey effects were detected, as brine shrimp feeding events were characterised by slower gape and ram velocities and a smaller gape. Feeding events on brine shrimp in the field were similar to feeding events on worms in the laboratory suggesting an artefact of training.
These results indicate that feeding behaviours measured in the laboratory may not be representative of feeding behaviours in the wild. Further consideration of organismal performance and laboratory constraints should be taken in future functional studies.
-
Abstract Phenotypic features define feeding selectivity in planktonic predators and therefore determine energy flow through food webs. In current‐feeding cnidarian hydromedusae, swimming and predation are coupled such that swimming also brings prey into contact with feeding structures. Fluid mechanical disturbances may initiate escape responses by flow‐sensing prey. Previous studies have not considered how fluid signals define the trophic niche of current‐feeding gelatinous predators. We used the hydromedusa
Clytia gregaria to determine (1) how passive (sinking) and active (swimming) feeding behavior affects pre‐encounter responses of prey to the medusae‐induced fluid motion, and (2) how prey responses affect the medusae's ingestion efficiencies. Videography of the predation process showed that passive prey such as invertebrate larvae were ingested during both feeding behaviors, whereas flow‐sensing prey such as copepods escaped the predator's active feeding behavior, but were unable to detect the predator's passive sinking behavior and were ingested (KWX 2= 19.8246, df = 4,p < 0.001). Flow visualizations using particle image velocimetry (PIV) showed fluid deformation values during passive feeding below threshold values that trigger escape responses of copepods. To address whether fluid signals mediate prey capture, we compared fluid signals produced by three hydromedusae with different diets.Aequorea victoria andMitrocoma cellularia produced higher deformation thanC. gregaria (two‐way ANOVA,F 2,52= 5.532,p = 0.007), which explains their previously documented negative selection for flow‐sensing prey like copepods. Through the analysis of hydromedusan feeding behaviors and pre‐encounter prey escapes, we provide evidence that fluid signatures shape the trophic niches of gelatinous predators. -
Abstract Human‐driven land use change can fundamentally alter ecological communities, especially the diversity and abundance of large‐bodied predators. Yet, despite the important roles large‐bodied predators play in structuring communities through feeding, there have been only a few investigations of how the feeding patterns of large‐bodied predators change in human‐dominated landscapes. One group of large‐bodied predators that has been largely overlooked in the context of land use change is the crocodilians. To help fill these gaps, we studied the feeding patterns of juvenile American alligators (
Alligator mississippiensis ) on neighboring barrier islands on the southeast coast of Georgia, USA. Jekyll Island has multiple golf courses and substantial amounts of human activity, while Sapelo Island does not have any golf courses and a much smaller amount of human activity. We found that juvenile alligator populations on both islands ate the same types of prey but in vastly different quantities. Sapelo Island alligators primarily consumed crustaceans while alligators that lived on Jekyll Island's golf courses ate mostly insects/arachnids. Furthermore, the Jekyll Island alligators exhibited a much more generalist feeding pattern (individuals mostly ate the same types of prey in the same quantities) than the more specialized Sapelo Island alligators (diets were more varied across individuals). The most likely explanation for our results is that alligators living on golf courses have different habitat use patterns and have access to different prey communities relative to alligators in more natural habitats. Thus, land use change can strongly alter the feeding patterns of large‐bodied predators and, as a result, may affect their body condition, exposure to human‐made chemicals, and role within ecological communities. -
ABSTRACT Understanding how organismal traits determine performance and, ultimately, fitness is a fundamental goal of evolutionary eco-morphology. However, multiple traits can interact in non-linear and context-dependent ways to affect performance, hindering efforts to place natural populations with respect to performance peaks or valleys. Here, we used an established mechanistic model of suction-feeding performance (SIFF) derived from hydrodynamic principles to estimate a theoretical performance landscape for zooplankton prey capture. This performance space can be used to predict prey capture performance for any combination of six morphological and kinematic trait values. We then mapped in situ high-speed video observations of suction feeding in a natural population of a coral reef zooplanktivore, Chromis viridis, onto the performance space to estimate the population's location with respect to the topography of the performance landscape. Although the kinematics of the natural population closely matched regions of high performance in the landscape, the population was not located on a performance peak. Individuals were furthest from performance peaks on the peak gape, ram speed and mouth opening speed trait axes. Moreover, we found that the trait combinations in the observed population were associated with higher performance than expected by chance, suggesting that these combinations are under selection. Our results provide a framework for assessing whether natural populations occupy performance optima.more » « less