Comparative Study Of Some Aspects Of Biology Of Three Mangrove Crabs From The Mangrove Wetland Of Lagos Lagoon Nigeria

ABSTRACT

The size composition, growth patter and feeding habit of 395 crab specimens of the hairy mangrove crab - S. huzardii, fiddler crab - U. tangeri and land crab - C. armatum collected from the mangrove swamp of the Lagos Lagoon were examined for six months. The carapace length of S. huzardii ranged from 1.70 cm - 4.60 cm (Carapace width from 1.90 cm - 3.60 cm) whilst that of U. tangeri ranged from 1.10 cm - 3.60 cm (Carapace width from 1.40 cm - 4.20 cm) and C. armation 4.50 cm - 9.50 cm (Carapace width from 4.60 cm - 9.80 cm). The total weight of S .huzardii ranged from 8.10 - 23.50 g, from 2.00 8 - 27.30 g in U. tangeri, and ranged from 39.10 g - 131.80 g in C. armatum. The crabs exhibited allometric growth. The condition factor K ranged from 20.0 - 1.01 cm in S. huzardii, 1.50 -2.76 cm in U. tangeri and 14.0 - 67.8 cm in C. armatum. 44 out of 150 specimens of S. huzardii had empty stomach, 38 out of the 125 specimens of U. tangeri had empty stomach while 26 out the 120 specimens of C. armatum had empty stomach. The stomach content of these three ecological related crustaceans showed S. huzardii fed mainly on diatoms, detritus, protozoa, filamentous algae; V. tangeri fed mainly on detritus, diatoms, protozoa, green algac, plant materials and sand grains; while c. armanum fed mainly phytoplankton, zooplankton, plant materials and sand grains. There was evidence of interspecific competition amongst this group of crustaceans, although each had been able to survive adequately. The sex, ratio in S. huzardii was 1:0.4, 1:0.4 in U. tangeri and I:1.1 in C. armanum.