Abstract
Abstract Background Gall crabs were described 150 years ago, but little is known about their biology, ecology, and taxonomy. Studying the breeding season can facilitate the understanding of the adaptive strategies and reproductive potential of gall crab and its relationship with the environment and other species. Results Growth and reproductive biology of the coral gall crab, Hapalocarcinus marsupialis, were studied at Gulf of Aqaba, Red Sea, Egypt. A total of 209 specimens were collected from different reef depths during 2014. Relationship between carapace width (CW) and total body wet weight (W) was represented as log W = 0.190 + 2.87 log CW. Growth generally shows negative allometric pattern. While the relation between CW and CL is represented by log CL = 0.019 + 1.009 log CW. This relation is linear and shows an isometric regression coefficient. The overall value for “Kn” is varied from 0.8 to 1.24, with an average of 1.11 ± 0.13, and denotes fitness for females. H. marsupialis shows clear sexual dimorphism and has lengthy definite breeding season characterized by carrying eggs throughout the year. The incubated eggs are semi spherical in shape, with diameter ranges according to maturity stages between 10 and 50 μm. The color of incubated eggs is also varied according to the developmental stage. Most females attain sexual maturity between 2.0 and 2.49 mm CW. Juveniles were recorded during year except the months of January and October. Fecundity varied from 10 to 740 eggs, with an average of 230 ± 173 eggs/female, showing linear relation with carapace width. Significant relationship between carapace width and fecundity was represented by log F = 0.22 + 2.39 log CW. Conclusion The present study emphasized the reproductive biology of H. marsupialis and explained the size structure, sexual dimorphism, breeding season, fecundity, size at first maturity, and juvenile’s recruitments in the three selected sites Dahab, Nuweiba and Taba along the Gulf of Aqaba.