Egg incubation and post-embryonic development in the red swamp crayfish Procambarus clarkii from the River Nile, Egypt

Under laboratory conditions, the incubated egg of ovigerous females, P. clarkii were observed during early autumn. Examined incubated eggs have black colors, characterize by spherical shape, averaged 2.143± 0.135mm in diameter before hatching, and have incubation periods varied from 11 to 19 days. After hatching the embryo is completely free, and undergoes several successive closely spaced molts. Stage 1 (Post-embryonic stage I) was characterized by globe-like carapace with uncomplete formation of appendages. The cephalothorax has black, dorsal hump containing the remaining vitellus. Eyes are sessile and rounded. Abdomen is arrow-like, lacking uropods, with naked telson without setae. At 2nd stage, it becomes elongated, with semicircular carapace, has dark pigment pedunculated eyes, covered entirely with red dots, with setose telson. At 3rd stage, it shows beginning of chromatophore pigmentation (with red dots on the whole organism), cephalothorax has almost reached it final anatomy. Stage 4 was characterized by first appearance of alimentary canal accompanied with pigmentation increases over the entire body, with relatively large-well defined telson and uropods. During stage 5th, the fully development eyes or mature eyes were formed; faint greenish colour on whole the body and red dots especially on abdomen were observed, showing independent locomotion far from mother´s abdomen. On the other hand, stages 6-9 have approximately same characters of stage 5, but with relatively developed growth. Stage 10showed the incidence or onset of external sexual dimorphism, characterized by first appearance for males modified pleopods(1st and 2ndpleopodes), and female 4 similar biramus pleopods on abdominal segments.