• acari;
  • nematalycidae;
  • Gordialycus;
  • ultrastructure;
  • cuticle;
  • reptation;
  • digestive tract

Nematalycid mites have undergone extreme changes of body shape in adaptating to life in tiny spaces between grains of fine sand. Because of their minute size, the morphology of these organisms can only be reconstructed from ultrathin serial sections. The cuticle forms regular alternating palettes on the surface; such a structure may also function as a plastron. Movement of the body is effected by a continuous secondary muscle layer beneath the epidermis which operates in connection with the cuticular palettes. This movement represents a hitherto unknown mode of reptation, which can be understood as an adaptation to moving among sand particles. The appendages have been reduced to a minute size. The morphology of the digestive tract is described and conclusions are drawn concerning nutrition.