Extreme morphological specialization: evolution and design of the feeding apparatus in seahorses and pipefishes (Syngnathidae)

Study Object: 
seahorses and pipefishes from diverse phylogenetic clades and with different types of snout morphology.
Principal Aim: 
investigate to what degree the extreme morphological specialization of the feeding system in syngnathids has constrained its functional capacity.
seserial histological sectioning, micro CT-scanning, graphical 3D reconstructing, dissecting, clearing and staining, biometrics, geometric morphometrics, immunohistochemistry and Finite Element Analysis.
Dr. Heleen Leysen



This research is part of the project "Functional consequences and ecological implications of extreme morphological specialization: design and function of the feeding apparatus in seahorses and pipefishes (Syngnathidae)". The family of Syngnathidae that encompasses the seahorses and pipefishes is roughly characterised by an elongated body and specialized snout. In many species the snout is extremely elongated with a reduced mouth aperture. These features directly constrain the size of prey that can be eaten. Moreover, this design will likely influence the mechanics and hydrodynamics of suction feeding (e.g. frictional forces will come into play) and is possibly associated with a reduced functional flexibility and/or versatility (i.e. the intrinsic capacity to modulate the feeding system in response to differences in prey properties), which may in turn further reduce the ability of these animals to capture prey. 
A detailed morphological study combined with a shape analysis and Finite Element Modelling on several syngnathid species as well as a generalised percomorph outgroup (Gasterosteus aculeatus, three spined stickleback) will help resolving the following problems:

  • What are the structural differences in the musculoskeletal organization of the feeding apparatus of different syngnathid representatives?
  • Does shape variation characterize the different phylogenetic clades and how is this related to the observed snout morphology?
  • How is the pattern of mechanical stress distribution during suction feeding related to different interspecific snout morphologies?
  • Does interspecific snout length affect muscle morphology and physiology?

On the whole this research will contribute to a better understanding of the evolutionary pattern leading to this extreme morphology.