Fig. 16

Frontal histological sections of Zoea IV (Holländer stain). a - cross-section showing the lobes of the digestive gland (DG) opening into the midgut (MG), see Fig. 2c for section plane; b - close-up of the interface of the digestive gland to the midgut (MG). Cell-types of the digestive gland identified include embryonic cells (E), blister like cells (B) and resorptive cells (R). c - section across the posterior lobes of the midgut gland and the anterior part of the hindgut (HG); d - the Y-organ (Y) is located underneath the lateral carapace close to the interface with the branchiostegites (Bst); e - distal part of a digestive gland lobe showing lumen (Lu) surrounded by epithelium composed of E- and F-cells. f - section through a lobe of the digestive gland showing epithelium with R- and B-cells surrounding the lumen (Lu). g - section of the digestive gland more posteriorly than A, the B-, F-, R-, and E-cells are identified. Abbreviations: B – blister like cell, Bst - epithelium of branchiostegite, DG - digestive gland, E - embryonic cell, F - fibrillary cell, H - heart, HG - hindgut, Lu – lumen of digestive gland, MG - midgut, R - resorptive cell, VNC - ventral nerve cord, Y - Y-organ