Supplementary Table 1: Functional morphological traits and biomechanical indices used in the analysis of functional morphology of
23 species of geophagine cichlids and 4 outgroup species from other tribes of Neotropical cichlids. A summary of the measurements
and their relevance is given, with references provided with more detailed descriptions.
Variable
Description
References
Adductor Mandibulae
The mass of AM, the complex of muscles primarily responsible for lower
[1–3]
(AM) Mass
jaw closing in fish, is indicative of the capacity to produce force when
biting.
Sternohyoideus (ST)
The mass of the ST, a major lower jaw opening muscle, is indicative of
Mass
the capacity to produce force during oral jaw opening and buccal
[4–6]
expansion.
Fifth Ceratobranchical
Correlated with the compressive strength in bone and the ability to resist
(CB5) Mass
crushing forces during prey processing.
[7–10]
Quadrate Offset (QO)
Describes patterns of bite occlusion and the distribution of force across
[11,12]
the jaws during biting. In Neotropical cichlids, lower QO are indicative of
even occlusion and force distribution, while higher QO indicate un-even
occlusion and distribution of force (Arbour Pers. Obs; see Fig. S2).
Maximum Upper Jaw
Higher JP may help to better direct suction force or increase attack
Protrusion (JP) Length
velocity and is correlated with the consumption of evasive prey.
Lower Jaw Mechanical Describes the efficiency of force and velocity transmission from the AM
Advantage (MA
(closing) or the ST (opening) to the tip of the lower jaw. Higher MA
closing and MA
indicates efficient force transmission, while lower MA indicates efficient
opening)
velocity transmission during biting or mouth opening respectively.
Oral Jaw Four Bar
The oral jaw four bar KT is the ratio between output rotation of the
Linkage Kinematic
maxilla to input rotation of the lower jaw during oral jaw opening and
[3,13,14]
[15]
[3,6,16–19]
Transmission (KT)
closing and describes a trade off in force and velocity transmission similar
Coefficient
to MA. Higher values of KT indicate efficient velocity transfer, while
lower values indicate efficient force transfer. Oral jaw KT was calculated
with a 30 degree rotation of the lower jaw.
Hyoid Four Bar
Describes the efficiency of force and velocity transmission during hyoid
Linkage Kinematic
depression and buccal expansion as a result of contraction of the epaxials,
Transmission
hypaxials and ST muscles. Hyoid KT was calculated using a 5 degree
Coefficient
rotation of the neurocranium/hyomandibula link and a 10% reduction in
[6,16,17,20]
the length of the sternohyoideus to account for muscle contraction.
Suction Index (SI)
Describes the transfer of force from the epaxial muscles to the buccal
cavity across the post-temporal/supracleithrum joint. To account for the
fact that maximum suction pressure occurs at 67% of buccal expansion
buccal area was multiplied by 0.67. Higher values of suction index
[21–24]
indicate a greater capacity to produce suction force during feeding.
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