Acomys cahirinus, the spiny mouse, is the only precocial murid. Given the relatively advanced state of neural maturation at birth, this species is therefore of interest for comparative studies of brain and behavioural development. Previous work on this species has indicated that (i) hippocampal thickness (relative to body weight) is greater in adult Acomys than in rats and mice; (ii) the hippocampus appears laminated at birth, unlike that of related altricial species; (iii) the degree of olfactory bulb maturation at birth is greater in Acomys than in gerbils or rats. In the study reported, the distribution of hippocampal mossy fibers of Acomys was compared with that of Rattus norvegicus, in order to extend our earlier findings. In addition, the implied involvement of hippocampal mossy fibers in olfaction suggests a relation to our studies of exploratory behaviour in this species.

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