P1.38 Jan. 4 Cranial morphology of Anguilla anguilla: dimorphism or continuous variation between extremes DE SCHEPPER, N; LACEUR, S; ADRIAENS, D*; Ghent University, Belgium; Ghent University, Belgium; Ghent University, Belgium email@example.com
The examination of the head morphology is the central topic of this study as the European eel is found to present a possible dimorphism with narrow-headed and broad-headed specimens. The presence of these different cranial shapes are well known for a long time and are previously studied to some extent, though characterization and quantification of this supposed dimorphism was unsuccessful and clarification of this phenomenon is presently lacking. Differences in diet were postulated as possible causes, where narrow-headed specimens prefer small and soft prey and broad-head ones feed in an increased degree on larger and/or harder prey. However, the presence of true dimorphism is questionable as these shapes may represent extremes of a continuous variety. In the attempt to address the cranial variation, three methodologies are applied: biometry, morphology and morphometry. The results indicate that the cranial variation is due to one continuous range, varying from extreme narrow-headed specimens to extreme broad-headed specimens, rather than due to the presence of two discontinuous morphs. The morphology of the broad-headed individuals, with hypertrophied jaw muscles, fortified neurocranium and suspensorium and robust jaws implies a bite of great strength, which can be applied in a predatory feeding strategy on large and/or hard prey. Preliminary dietary data tend to point to possible relations between the morphological difference and diet as well.