International Journal of Aquaculture, 2017, Vol.7, No.7, 51
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Length ratio = Dorsal length of the vertebra / Ventral length of vertebra
Width ratio = Anterior width of the vertebra / Posterior width of the vertebra
Height ratio = Dorsal height of the vertebra / Ventral height of the vertebra
Thickness ratio = Middle line width of the vertebra / Posterior width of the vertebra
Slenderness ratio = Dorsal length of the vertebra / Posterior width of the vertebra
The purposes of the 5 ratio mentioned above are: length ration for wedging along vertebral length; width ration for
wedging along the vertebral width; height ration for distortion of the amphicoelous shape; thickness ration for
mid-centrum thickness; and slenderness ratio for ventral slenderness. All measurements were made by the same
person and instrument in order to increase the precision of measurements and reduce variability introduced by
measurement error.
Table 1 Morphometrics of the abnormal and normal specimens of
Puntius kamalika
collected from
Colombo District,
Sri Lanka
Morphometric characters
DZ 3757 abnormal
DZ 3758 normal
Total length
58.5
72.6
Standard length (mm)
45.2
55.0
Forked length
8.3
8.7
Head length
13.2
15.5
Pre dorsal length
24.0
27.0
Post dorsal length
24.6
32.4
Pre anal length
35.1
40.8
Pre pelvic length
24.0
27.8
Pre pectoral length
13.0
15.2
Caudal peduncle length
7.8
9.2
Body depth
14.3
16.8
The specimens were kept in the ichthyological collection of the Department of Zoology, University of Peradeniya,
Sri Lanka (DZ 3757 abnormal and DZ 3758 normal).
3 Results
Externally, it was possible to observe the anomaly in the body, curved vertebral column at one place (Figure 2).
Internally, all the organs were appeared normal. Caudal region of the vertebral column showed no flexion. The
case of lordosis involves 1
st
– 7
th
caudal vertebrae, with the severe twisting is at the 4
th
caudal vertebra. The
vertebral column starts to bend slightly starting from 12
th
thoracic vertebrae reaching to the lowest point at the
bottom of the curvature at 4
th
caudal vertebra (Figure 3). The DC ratio of the deformed specimen is 0.30, the value
of the lordotic angle is 95˚, and the curvature’s depth is 30 mm.
The five ratios calculated for the 5 ratios appeared to be affected by the position of the vertebra and the curvature
of the vertebral column. Vertebrae 1-3 showed and increased height on the ventral side (0.022-0.026) (Figure 3)
and reduced on the dorsal side (1.229-1.250). The anterior and the posterior parts of the centra of the 4
th
and 5
th
caudal vertebrae were distorted in a way that the anterior and posterior parts of the 4
th
and the 5
th
vertebrae are
raised upward. The 6
th
and 7
th
vertebrae are wedged (1.334-1.356) (have a reduced ventral length relative to their
dorsal length). Vertebrae 2-3 and 7-8 have reduced midline widths (0.023-0.030). Slenderness and thickness were
less in vertebrae 6-8 (0.001-0.003) (Figure 3).
4 Discussions
Without experimental evidence, it is not possible to know the source of the causes of this disorder. Among the
causes that have been given for the case of lordosis are genetic in addition to the nutrition and environmental
factors. Other factors such as egg density, shocks and presence of pollutants of different types and variation in
levels of radiation, salinity, oxygen and light can also considered among those reasons to cause lordosis (Caris and
Rice, 1990). All these factors can happen to the studied specimen.
