Fig. 4

Histological observations of hepatopancreas from Chinese mitten crab fed with diet containing histamine after 28 days. a, b Hepatopancreas of control crabs (histamine 0 mg/kg) showing complete structure of different cells in the control; Hepatopancreas exhibited normal star-shaped lumina (L) (asterisk) and intact brush border (red arrow). The four cell types:B cell (white arrowhead), F-cell (black arrowhead), R-cell (black arrow), E-cell (white arrow) were clearly visible. c, d Crabs fed diet containing histamine 1 g/kg, loss of star-shape lumina (asterisk) and brush border (red arrow) damaged and the number of B-cell increased (white arrowhead); e, f crabs fed diet containing histamine 2 g/kg, all cells were highly vacuolized (white arrowhead), haemocytes occurred among the tubules (white arrow). g, h One vacuole were released into the tubule lumen (black arrow), basal lamina were detached from tubule (black arrowhead) and cell boundary was unclear observed