Fig. 3
From: Small-scale phenotypic differentiation along complex stream gradients in a non-native amphipod
Stages of embryonic development in G. roeselii. a Newly fertilized eggs (stage 1), surrounded by a membranous sac. b Detailed view of eggs at stage 1 with no visible cell cleavage. c Stage 2 is characterized by the formation of large yolk cells through holoblastic cell cleavage. d Embryos at stage 3 show a caudal groove (c.g.). e At stage 4, the embryo’s body is separated into cephalothorax (ce.) and abdomen (ab.). The dorsal organ (d.o.) is visible. Embryos show a comma-like body shape and body appendages start to develop. f Red eye pigmentation (e.p.) and fully developed body appendages are characteristic of developmental stage 5. g Fully developed juveniles with completely developed compound eyes (c.e.) that are still surrounded by the external chorion of the egg indicate developmental stage 6. h Newly hatched juveniles (stage 7) have ruptured and left the chorion