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International Journal of Marine Science 2014, Vol.4, No.33
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5
with the posterior region of the skull, forming with the
next vertebra a link between the two main elements of
the axial skeleton, which is a function that requires a
unique some morphological feature (Videler, 1993).
As the vertebral biometric parameters increased for
the six vertebrae beyond V4-V9, these vertebrae could
be considered like transition vertebrae (Ramzu and
Meunier, 1999).
The posterior middle region (V1-V18) includes the
limit between the truncal and caudal regions (V11)
which corresponds to the haemal arch closing. It is
therefore composed of caudal vertebrae and forms
morphological units. In these regions the increase is
regular until a maximum value before decreasing
progressively.
The ural region comprises of five vertebrae (V18-V23).
It corresponds to the tail and is characterized by a
decrease of the three values of the analyzed
parameters.
As in other teleost fishes (Ramzu et al., 1992), the
substitution of classical anatomical trunco- and caudal
region by more than two regions as in the case of
L.
equulus
, is probably linked to the mechanical
constraints of swimming. Moreover, the antero-posterior
development of the three morphological parameters
studied with the variations of the postcranial and ural
regions on the one hand, and the maximum of the
middle regions on the other, favors this hypothesis.
The common ponyfish is known to present a
thunniform mode of swimming (Breder, 1926,
Lindsey, 1978, Webb, 1978) in which the vast
majority of movement is concentrated in the very rear
of the body and tail. Thunniform swimmers
in which
the vast majority of movement is concentrated in the
very rear of the body and tail
. The fact that the
maximum of the length of the vertebra (VL) occurs
around the vertebrae V17-V19; this can be the
structure response of these vertebrae to the local
presence of maximal mechanical constraints.
Regarding the fourth region, its specific parametrical
variation might express the major role performed by
the caudal vertebrae in the motor process of
swimming. The caudal skeleton responds to the
alternate contraction of the intrinsic muscles on sides
of this region, thus torsion of the caudal peduncle is
created, when they move suddenly toward a prey or
run away from a predator. This result backs those of
Bainbridge (1963) on different species of fishes.
The regionalization in the vertebral column of
L.
equulus
could be developed through the difference in
length of vertebrae in different regions of the vertebral
column which in turn is due to different mechanisms
that regulate growth of vertebrae in each region
(Fjelldal et al., 2005).
The similarity in the value of the aspect ratio of both
abdominal and caudal region obtained in this study
may indicate that the changes in the vertebral length in
abdominal and caudal regions are closely linked
(Ward and Brainerd, 2007).
The morphometric analysis of the vertebral column
has revealed a significant difference between the
variation of the vertebral length, height, width and
vertebral central width studied taken on each vertebra
of
L. equulus
. Therefore, characterization of the
vertebrae is possible on the bases of these parameters.
Acknowledgements
We would also like to thank the Ministry of Fisheries Wealth,
Marine Science and Fisheries Centre, Ministry of Fisheries
Wealth and the directorate of Agriculture and Fisheries
Developmental Fund for giving us the opportunity to work on
the fish samples within the qualitative and quantitative
distribution of marine organisms in Sultanate of Oman and to
provide the appropriate financial support.
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