Morphometric characteristics of two walking crabs, Cardiosoma amatum (Gercarcinidae), Goniopsis pelli (Graspidae) from a mangrove ecosystem in Lagos Nigeria

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Lawal-Are, A. O.
Moruf, R. O.
Akubueze, K. I.
Adewole, O.
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Crabs typically walk sideways because of the articulation of the legs which makes a sidelong gait more efficient. The occurrence, size diameter, growth pattern and allometric condition factor of 233 specimens comprising of 117 for Cardiosoma armatum and 116 for Goniopsis pelii from the mangrove swamps of AbuleAgege Creek, Lagos, Nigeria were investigated using standard morphometric techniques. The size groups 3.5 – 3.9 cm and 6.0 - 6.4 cm occurred most for G. pelii and C. armatum respectively. C. armatum is a bigger species ranging in carapace length from 3.00 to 7.40cm and weighed 91.3g to 183.9g, while the carapace length of G. pelii ranged from 2.50 to 4.90 cm and total weight from 11 g to 37 g. C. armatum occurred more in the mangrove swamp and unimodal distribution was exhibited by both crab species. Total length – weight relationship for both crab species showed negative allometric growth (b < 3). There was a weak correlation between carapace length and total weight of C. armatum but G. pelii exhibited strong significant correlation (r = 0.577, P < 0.01). Although, C. armatum had a higher condition factor (5.4 – 30.2) compared to G. pelii (3.4 – 8.0) but in both species, the highest K-values were recorded for the small size group and decreased with increase in sizes of the crabs.
size composition , growth pattern , condition factor , Land crabs