Jaw lever analysis of Hawaiian gobioid stream fishes: A simulation study of morphological diversity and functional performance

Abstract

Differences in feeding behavior and performance among the five native Hawaiian gobioid stream fishes (Sicyopterus stimpsoni, Lentipes concolor, Awaous guamensis, Stenogobius hawaiiensis, and Eleotris sandwicensis) have been proposed based on the skeletal anatomy of their jaws and dietary specialization. However, performance of the feeding apparatus likely depends on the proportions and configurations of the jaw muscles and the arrangement of the jaw skeleton. We used a published mathematical model of muscle function to evaluate potential differences in jaw closing performance and their correlations with morphology among these species. For example, high output force calculated for the adductor mandibulae muscles (A2 and A3) of both A. guamensis and E. sandwicensis matched expectations based on the morphology of these species because these muscles are larger than in the other species. In contrast, Stenogobius hawaiiensis exhibited an alternative morphological strategy for achieving high relative output forces of both A2 and A3, in which the placement and configuration of the muscles conveyed high mechanical advantage despite only moderate cross-sectional areas. These differing anatomical pathways to similar functional performance suggest a pattern of many-to-one mapping of morphology to performance. In addition, a functional differentiation between A2 and A3 was evident for all species, in which A2 was better suited for producing forceful jaw closing and A3 for rapid jaw closing. Thus, the diversity of feeding performance of Hawaiian stream gobies seems to reflect a maintenance of functional breadth through the retention of some primitive traits in combination with novel functional capacities in several species.

Comparative lever analysis and ontogenetic scaling in esocid fishes: Functional demands and constraints in feeding biomechanics

“…According to the skeletal dimension of the jaw and muscle insertion in our simulation, EMAs of the Am‐RM emphasize the force transmission and EMAs of the Am‐S emphasize the velocity transmission in all esocid species. This pattern seems consistent with other teleost fishes (e.g., Westneat, ; Maie et al, ). The EMA of the Am‐EnRM fall between those of the Am‐RM and Am‐S.…”

A biomechanical analysis of prognathous and orthognathous insect head capsules: evidence for a many‐to‐one mapping of form to function

“…This many-to-one mapping of region specific strain ratios to largely similar relative strains of the whole head capsule has been sparsely assessed (Pierce et al, 2008;Stayton, 2011). Most approaches use a combination of shape analysis with different types of lever calculations to estimate force transmissions over a wider specimen sample and correlate force transmissions with shape variation (Alfaro et al, 2004;Maie et al, 2009;Stoessel et al, 2013;Anderson et al, 2014;Collar et al, 2014;Mart ın-Serra et al, 2014;Scales & Butler, 2016;Martinez & Sparks, 2017). Common to these approaches is their use of phylogenetically closely related species, which show variation in a functional subsystem.…”

Evolutionary Novelty versus Exaptation: Oral Kinematics in Feeding versus Climbing in the Waterfall-Climbing Hawaiian Goby Sicyopterus stimpsoni

“…For example, one factor contributing to the greater peak retraction magnitudes of the mandible and hyoid during climbing may be the advancement of the anterior portion of the head up the climbing slope [9]. Linkage mechanics of cranial elements could force retraction of the mandibular and hyoid elements as the whole head narrows during the portion of climbing during which the head advances [40].…”