International Journal of Marine Science, 2017, Vol.7, No.28, 275-283
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2.3 Absence of the pelvic fins
Externally, the deformed fish (Figure 6) showed complete absence of pelvic fins. The area where the pelvic fins
should be present was very soft and there was no indication of presence of any internal bony materials. This
suggests that the pelvic girdle supporting the pelvic fins was completely missing too.
3 Discussion
The present study reports skeletal deformities in three adult specimens of wild teleost fish species in the Turkish
waters.
Skeletal deformities were documented for wild species of fish (Divananch et al., 1996; Jawad et al., 2013; Jawad
and Liu, 2015) and were attributed to both genetic (Ishikawa, 1990) and epigenetic factors (Chatain, 1994;
Fjelldal et al., 2009; Gavaia et al., 2009).
Figure 6 Abnormal specimen of
Sparus aurata
, 224 mm TL showing complete absence of pelvic fins
The specimen of
M. cephalus
suffering scoliosis faced an anterior-posterior (
i.e
. cranial-caudal) compression
along the spine. Structural sign was present in the x-ray of the specimen showing that the normal amphicoelous
(hour-glass) shape of vertebrae was distorted so that vertebral height was reduced on the convex and was greater
on the concave side of curvature. In addition, vertebrae at the middle of the curvature were wedged so that the
length on the concave side of the curve was reduced relative to the convex length. Also, the midline width was
significantly reduced for some vertebrae. Similar changes were observed in
Poecilia reticulata
by Gorman et al.
(2010), who attributed them to either (1) distortion of normal vertebral shape or (2) active remodeling of vertebral
osteoid bone as a consequence of extrinsic forces. The formation of asymmetrical vertebrae demonstrates changes
in growth rate along their growth plates, causing uneven progression in longitudinal growth and consequential
shape distortion in the form of wedging (Mente et al., 1997).
Another evidence for the severity of the case of
M. cephalus
is provided from the depth of the 4 curvatures that
represented by the DC factor calculated. Both B and C curvatures fall in the middle of the vertebral column were
deeper than the other two curvatures a condition indicating the extreme extent of the curvature of the vertebral
column at these points.
The present case of severe pugheadness anomaly in
N. randalli
is different from the other cases of pugheadness
reported from wide range of fish species (AL-Hassan, 1988; Jawad and Hosie, 2007; Macieira and Joyeux, 2007;
Francini-Filho and Amado-Filho, 2013; Jawad et al., 2014), the present case characterizes in having normal both
upper and lower jaw.
It is unknown whether the observed deformity in the specimen of
N. randalli
has reduced its survival potential;
however, the pugheadness individual showed no obvious signs of poor health, so feeding was obviously
unrestricted due the open mouth. Escaping from the predators was also not likely deterred by the observed
abnormality, because the body of the deformed fish was robust.
Unlike the situation in the hatchery, the frequency of pugheadness deformity in wild fish populations is rare
(Bortone, 1971; Riehl and Schmitt, 1984). This is probably due to the fact that the abnormal individuals in the
