Epidermal cell cycle and region-specific growth during segment development in Artemia.
During larval development in instar IV brine shrimp, segment 1 grew by cell replication and cell differentiation. Cell cycle analysis revealed that the cell cycle was synchronized with the molt cycle. Mitosis occurred late in the instar and S phase began at hr 6 of the following instar. Three populations of cells comprised the dorsal integument. The medial-dorsal region did not grow. Cell enlargement occurred in the dorsal-lateral population while cell replication took place in the lateral population. The limb bud (ventral surface) grew in width by replication in the distal population, and in height by enlargement of the general epidermal cells in the proximal population. Expansion of each region of the integument was proportional to the cell growth in that region. Moreover, both growth processes were dependent on the level of nutrients and were enhanced by diets enriched in polyunsaturated fatty acids. A nutrient-dependent growth control point occurred in the G1 period. The commitment to replication and differentiation occurred by hr 2 of instar IV. The findings show that integumental growth is a result of region-specific cell growth processes which are controlled by nutrients during the G1 period.
Freeman
J A
JA
Department of Biological Sciences, University of South Alabama, Mobile 36688.
D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001156:Artemia / Q000254:growth & development*; D002453:Cell Cycle / Q000502:physiology; D000078404:Epidermal Cells; D005121:Extremities / Q000254:growth & development; D007814:Larva / Q000254:growth & development; D009024:Morphogenesis / Q000502:physiology