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Evolutionary morphology of the extremely specialized feeding apparatus in seahorses and pipefishes (Syngnathidae)

Heleen Leysen UGent (2011)
abstract
This PhD thesis deals with the evolution of the specialized head morphology in Syngnathidae, a family among the bony fishes that comprises pipefishes, seahorses, seadragons and pipehorses. The feeding apparatus is extremely specialized in this family. All representatives have a tubular snout with small, terminal jaws. Prey intake is very fast, however, suction feeding by means of a long and slender snout also implies hydrodynamic constraints (such as more drag due to suction through a narrow tube and a high moment of inertia caused by rotation of a head with a long snout). This paradox renders the trophic apparatus in Syngnathidae a very interesting research topic. A detailed morphological description of the feeding apparatus of several syngnathid representatives forms the core of this research, with attention to the effect of snout elongation on the musculoskeletal structure of the head. This morphological part reveals a number of structural features that probably are related to pivot feeding (e.g. the interhyal bone with its two articulation heads for the hyoid). The family is characterized by a large morphological variation with regard to snout dimensions. The morphological variation in head shape within the family is quantified by means of a preliminary geometric morphometric analysis, indicating that long-snouted species, which are more specialized, have a reduced intraspecific variation in terms of their head shape. Besides that, the extraordinary performance of the trophic system is studied kinematically and a hypothesized four-bar mechanism is tested, providing clear proof for the linkage between hyoid and neurocranium movements. Finally, a finite element analysis is used to predict the mechanical stress caused by loading of the feeding apparatus during prey intake. The results of this part indicate that the geometry of the bones in the snout (bone thickness, amount of overlap between different bones, etc.) has a clear influence on the stress distribution. Overall, the results of this dissertation highlight that Syngnathidae, with their highly specialized feeding apparatus, unusual development and unequalled performance, establish conclusive proof for the incredible capabilities of natural selection and evolution.
Please use this url to cite or link to this publication:
author
promoter
UGent
organization
year
type
dissertation
publication status
published
subject
keyword
suction feeding, head shape, functinal morphology, mechanical stress
pages
2 vol. (193 + 77) pages
publisher
Ghent University. Faculty of Sciences
place of publication
Ghent, Belgium
defense location
Gent : Faculteit Wetenschappen (K.L. Ledeganckstraat 35, auditorium 5)
defense date
2011-03-11 16:00
language
English
UGent publication?
yes
classification
D1
additional info
dissertation consists of copyrighted material
copyright statement
I have transferred the copyright for this publication to the publisher
id
1196072
handle
http://hdl.handle.net/1854/LU-1196072
date created
2011-03-24 12:11:09
date last changed
2017-01-16 10:38:01
@phdthesis{1196072,
  abstract     = {This PhD thesis deals with the evolution of the specialized head morphology in Syngnathidae, a family among the bony fishes that comprises pipefishes, seahorses, seadragons and pipehorses. The feeding apparatus is extremely specialized in this family. All representatives have a tubular snout with small, terminal jaws. Prey intake is very fast, however, suction feeding by means of a long and slender snout also implies hydrodynamic constraints (such as more drag due to suction through a narrow tube and a high moment of inertia caused by rotation of a head with a long snout). This paradox renders the trophic apparatus in Syngnathidae a very interesting research topic. 
A detailed morphological description of the feeding apparatus of several syngnathid representatives forms the core of this research, with attention to the effect of snout elongation on the musculoskeletal structure of the head. This morphological part reveals a number of structural features that probably are related to pivot feeding (e.g. the interhyal bone with its two articulation heads for the hyoid).
The family is characterized by a large morphological variation with regard to snout dimensions. The morphological variation in head shape within the family is quantified by means of a preliminary geometric morphometric analysis, indicating that long-snouted species, which are more specialized, have a reduced intraspecific variation in terms of their head shape. Besides that, the extraordinary performance of the trophic system is studied kinematically and a hypothesized four-bar mechanism is tested, providing clear proof for the linkage between hyoid and neurocranium movements. Finally, a finite element analysis is used to predict the mechanical stress caused by loading of the feeding apparatus during prey intake. The results of this part indicate that the geometry of the bones in the snout (bone thickness, amount of overlap between different bones, etc.) has a clear influence on the stress distribution.
Overall, the results of this dissertation highlight that Syngnathidae, with their highly specialized feeding apparatus, unusual development and unequalled performance, establish conclusive proof for the incredible capabilities of natural selection and evolution.},
  author       = {Leysen, Heleen},
  keyword      = {suction feeding,head shape,functinal morphology,mechanical stress},
  language     = {eng},
  pages        = {2 vol. (193 + 77)},
  publisher    = {Ghent University. Faculty of Sciences},
  school       = {Ghent University},
  title        = {Evolutionary morphology of the extremely specialized feeding apparatus in seahorses and pipefishes (Syngnathidae)},
  year         = {2011},
}

Chicago
Leysen, Heleen. 2011. “Evolutionary Morphology of the Extremely Specialized Feeding Apparatus in Seahorses and Pipefishes (Syngnathidae)”. Ghent, Belgium: Ghent University. Faculty of Sciences.
APA
Leysen, H. (2011). Evolutionary morphology of the extremely specialized feeding apparatus in seahorses and pipefishes (Syngnathidae). Ghent University. Faculty of Sciences, Ghent, Belgium.
Vancouver
1.
Leysen H. Evolutionary morphology of the extremely specialized feeding apparatus in seahorses and pipefishes (Syngnathidae). [Ghent, Belgium]: Ghent University. Faculty of Sciences; 2011.
MLA
Leysen, Heleen. “Evolutionary Morphology of the Extremely Specialized Feeding Apparatus in Seahorses and Pipefishes (Syngnathidae).” 2011 : n. pag. Print.