Journal Article
Morphological and functional diversity of the mandible in suckermouth armored catfishes (Siluriformes: Loricariidae)
Lujan, N.K. and Armbruster, J.W.
Record Number:
5257
Year:
2012
Journal:
Journal of Morphology
Pages:
24-39
Volume:
273
Abstract:
ABSTRACT We examined the mandibles of 377 individuals
representing 25 species, 12 genera, 5 tribes, and 2
subfamilies of the Loricariidae, a species-rich radiation of
detritivorous–herbivorous neotropical freshwater fishes
distinguished by having a ventral oral disk and jaws specialized
for surface attachment and benthic feeding. Loricariid
mandibles are transversely oriented and bilaterally
independent, each rotating predominantly around its long
axis, although rotational axes likely vary with mandibular
geometry. On each mandible, we measured three traditional
and three novel morphological parameters chosen
primarily for their functional relevance. Five parameters
were linear distances and three of these were analogous to
traditional teleost in- and out-levers for mandibular
adduction. The sixth parameter was insertion area of the
combined adductor mandibulae muscle (AMarea), which
correlated with adductor mandibulae volume across a subset
of taxa and is interpreted as being proportional to
maximum force deliverable to the mandible. Multivariate
analysis revealed distributions of phylogenetically diagnosed
taxonomic groupings in mandibular morphospace
that are consistent with an evolutionary pattern of basal
niche conservatism giving rise to multiple adaptive radiations
within nested clades. Correspondence between mandibular
geometry and function was explored using a 3D
model of spatial relationships among measured parameters,
potential forces, and axes of rotation. By combining
the model with known loricariid jaw kinematics, we developed
explicit hypotheses for how individual parameters
might relate to each other during kinesis. We hypothesize
that the ratio [AMarea/tooth row length2] predicts interspecific
variation in the magnitude of force entering the
mandible per unit of substrate contacted during feeding.
Other newly proposed metrics are hypothesized to predict
variation in aspects of mandibular mechanical advantage
that may be specific to Loricariidae and perhaps shared
with other herbivorous and detritivorous fishes. J. Morphol.
273:24–39, 2012. 2011Wiley Periodicals, Inc.
KEY WORDS: evolutionary novelty; functional
morphology; jaw diversity; jaw mechanics; durophagy;
model
Times Cited:
5