30 



Figure 25: Nervous system of the pediveliger of Pecten maximus (1) in the statocyst region 



(from Cragg and Nott, 1977). 

 pg — pedal ganglion; plcc — pleurocerebral connective; pig — pleural ganglion; 

 pipe — pleuropedal connective; plvc — pleurovisceral connective; sc — statocyst canal; 



sn — statocyst nerve. 



Figure 26: Pedal ganglion and statocysts of the pediveliger of Dreissena polymorpha Pall. 



in section (from Meisenheimer, 1901). 



pg — pedal ganglion; sc — statocyst; si — statolith. 



Table 1 : Relative intensity of response of different larval stages of M. edulis to external stimuli* 



(from Bayne, 1976) 



Larval stage 



Light 



Extemal stimuli 



Gravity 



Pressure 



Trochophore 



Veliger 

 Veliconcha** 

 Pediveliger (swimming) 

 Pediveliger (crawling) 



o 



+++ 







o 



* o = no response; (-) = negative response, (+) = positive. 



** According to Bayne, the veliconcha stage corresponds to that of developed veliger with umbo. 



