Phenotype of larval shell parts synthesized in the presence of NikkomycinZ. a-d. Scanning electron microscopy (SEM) images of shells synthesized by larvae exposed to NikkomycinZ at concentrations of 10 μM. All presented features were not observed in any of the shells extracted from the respective control cultures (0 μM NikkomycinZ). Insets show the respective features as observed frequently by video microscopic (VM) in vivo analyses of 10 μM NikkomycinZ treated cultures. a. Typically, 5 day old shell valves were irregularly wavy edged when larvae were grown in the presence of NikkomycinZ from the 2nd day on. The inset shows the same feature at the age of 8 days in certain shell regions (arrowheads). b. If NikkomycinZ was supplied to cultures from the 8th to the 19th day, the larval shell rims and thus the growth fronts are heavily deformed and appear either stretched or squeezed depending on the shell region. The inset shows that features such as undulated shell rims (dotted lines) were observed also in 8 day old larvae that had been treated for three days with NikkomycinZ. c. Shells of 8 day old larvae (SEM image) and 12 day old larvae (VM image) that were exposed to NikkomycinZ for three and four days, respectively, appear curved (arrowheads) along the hinge line of the provinculum. d. The outer surface of a shell extracted from an 8 day old larva after 3 days of NikkomycinZ treatment revealed local indentations (dotted lines). Note that also the growth lines appear curvaceous (arrowheads). These data suggest that the inhibition of chitin synthase influences the synthesis and biomineralization of larval shells on length scales of 10 μm – 100 μm.