Temperature and neural development of the Atlantic herring (Clupea harengus L.)

Embryos of Atlantic herring (Clupea harengus L.) from the Buchan (Northern North Sea) stock were incubated from fertilisation until hatching at temperatures of 5, 8, 12, and 15 degrees C. The relative timing of development of the Kolmer-Agduhr (KA) neurons, the posterior lateral line nerve, the motor neurons, and myotubes were determined with respect to somite stage of the embryo. Development of the KA neurons, the lateral line nerve, and the myotubes was similar at all temperatures. In contrast, timing of outgrowth of the motor neuron axons with respect to somite stage was earlier at higher (> or = 12 degrees C) than at lower temperatures (< or = 8 degrees C) although it reached a similar point at all temperatures by the 58-somite stage. Our hypothesis to explain these observations is that delayed motor axon outgrowth in the lower temperature groups is probably due to a delay in a signalling interaction between motor neurons and the somite.