Fig. 21

Diatom genus Pseudo-nitzschia. A. Terminology of cell features including striae, fibulae and central interspace (CIS); cell 150 µm long; B. (LM) Overlapping of cells in chains (arrow); C. (LM) ‘delicatissima’ group bloom from Tasmanian waters; D. (LM) Sigmoid cells of P. multistriata; E. (TEM) Valve structure of P. cuspidata showing CIS (arrow) and single row of square poroids; F. (TEM) Valve fine structure of P. multistriata; G. Rounded cell end of P. lineola; H. Velum structure of heavily silicified P. pungens showing two rows of large poroids; I. (TEM) Pseudo-nitzschia multiseries with three rows of small poroids; J. Velum structure of P. fraudulenta with two rows of large poroids; K. Pseudo-nitzschia calliantha with star-shaped velum covering the poroids; L. Pseudo-nitzschia hasleana with irregular segmented velum covering the pores; M. Pseudo-nitzschia micropora with still smaller poroids (‘micropora’) covering the velum.