International Journal of Marine Science, 2016, Vol.6, No.11, 1-10
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Burrow type called Y shape with double opening (YDO) (Figure 2g) (n = 4) had largest volume (465.42 ± 266.93
cm
3
) with an average burrow opening diameter of 24.54 ± 4.80 mm. The YDO shaped burrows were constructed
by the crabs with mean carapace length of 16.85 ± 5.67mm (n = 2). The burrow was vertical with mean inclination
angle of 90.25 ± 18.02°. The inclination angle of primary arm (90.25 ± 18.02°) was significantly smaller than the
secondary arm (97.05 ± 17.76°; paired t test, t = 2.35, df = 3, p<0.05). The primary and secondary arm of the
burrow joined together in the straight shaft and the straight shaft ended with small chamber at the base. Both the
primary and secondary arms of the burrow opened on the surface and the burrow opening diameter of primary arm
(24.54 ± 4.80 mm) was significantly larger than the secondary arm (19.08 ± 0.89 mm; paired t test, t = 4.31, df = 3,
p<0.05). The total depth of the burrow was 36.22 ± 12.80 cm. Depth of primary arm (16.25 ± 9.25 cm) was
slightly but significantly higher than depth of secondary arm (15.6 ± 9.42 cm; paired t test, t = 2.91, df = 3,
p<0.05). Total mean length of the burrow was 42.1 ± 14.48 cm and the horizontal distance between burrow
openings of both the arms was 13.77 ± 4.34 cm. The chamber situated on the base had length of 6.15 ± 2.14 cm
and width of 4.12 ± 1.55 cm.
U shape burrows (Figure 2e) (n = 3) had mean burrow volume of (399.39 ± 236.42 cm
3
) with an average burrow
opening diameter of 22.47 ± 5.39 mm. The U shaped burrows were constructed by the crabs with mean carapace
length of 14.02 ± 4.52 mm (n = 2). The burrow was vertical with mean inclination angle of 98.00 ± 28.58°. The
inclination angle of primary arm (98.00 ± 28.58°) was larger than the secondary arm (97.33 ± 5.85°; paired t test, t
= 2.91, df = 2, p = 0.48). Both the primary and secondary arms of the burrow opened on the surface and the
burrow opening diameter of primary arm (22.47 ± 5.39 mm) was significantly larger than the secondary arm
(16.86 ± 1.19 mm; paired t test, t = 2.91, df = 2, p<0.01). The total depth of the burrow was 20.26 ± 6.59 cm. The
depth of primary and secondary arm was similar. Total mean length of the burrow was 33.63 ± 8.95 cm and the
horizontal distance between burrow openings of both the arms was 16.52 ± 2.64 cm.
J shape with branch at the base (JBB) (Figure 2b) (n = 12) had mean burrow volume of 386.40 ± 259.94 cm
3
with
an average opening diameter of 18.73 ± 5.40 mm. The burrows were constructed by the crabs with mean carapace
length of 12.37 ± 4.77 mm (n=9). The burrow was vertical in shape with mean inclination angle of 93.16 ± 18.58°
and depth of 21.83 ± 7.82 cm. The main shaft takes turn towards the surface in the form of branch which does not
extend to the surface and ends in the forms of spherical blind end. Second branch is formed from the base of the
main shaft and ends making small chamber at the base. The mean length of the burrow was 25.81 ± 8.09 cm. The
length of branch 1 (11.31 ± 3.19 cm) (Side branch) was significantly higher than the branch 2 (8.07 ± 3.19 cm;
paired t test, t = 1.79, df = 11, p<0.001) (Base branch). The depth of primary arm (14.3 ± 5.45 cm) was
significantly higher than the depth of secondary arm (7.55 ± 2.62 cm; paired t test, t = 1.80, df = 11, p<0.0001).
The inclination angle of primary arm (109.41 ± 20.35°) was significantly higher than the main shaft (paired t test,
t = 1.83, df = 11, p<0.001). In 70 percent burrows, the primary arm faced the seaward orientation. The horizontal
distance between main arm and primary arm was 11.57 ± 5.14 cm.
Bulb shaped (Figure 2c) (n = 6) were the smallest burrow in terms of depth with mean depth of 12.29 ± 3.47 cm.
The burrows were vertical in shape with mean inclination angle of 95.08 ± 17.31° and mean burrow volume of
376.97 ± 240.80 cm
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. The mean burrow opening diameter was 19.07 ± 5.02 mm and they were constructed by the
crabs with mean carapace length of 12.29 ± 3.45 mm (n = 4). In the bulb shape burrows, the burrow opens directly
in a large chamber. The mean length and width of the chamber were 6.43± 1.71 cm and 5.46 ± 1.78 cm,
respectively. The mean total length of the burrow was 23.72 ± 9.37 cm.
The single tube burrow (ST) (Figure 2d) (n =15) had mean volume of 366.22 ± 236.19 cm
3
with mean opening
diameter of 18.14 ± 5.07 mm. The burrows were constructed by the crab having mean carapace length of 11.66 ±
3.69 mm (n =10). The burrow inclined vertically from the surface with the mean inclination angle of 93.11 ±
17.08° and ended with chamber (CL: 3.06 ± 0.59 cm CW: 4.48 ± 0.53 cm) at the base. The mean depth and length
of the burrows were 19.22 ± 7.50 cm and 23.39 ± 8.85 cm, respectively. The mean horizontal distance of the
burrow was 3.13 ± 0.60 cm.
