Images of Whole Dolphin Brains

These plates show labelled images of the brains of two IndoPacific bottlenose dolphins (Tursiops aduncus) from the collection of the South Australian Museum.

Plates 1 and 2 show ventral and dorsal aspects (respectively) of M23356, from a male Tursiops aduncus, collected 4 June 2005, 5.5 km NE Garden island, Angus inlet.  Specimen had originally been preserved in ethanol.  The body length was measured at 2080 mm and the body weighed 113 kg.

Plate 3 shows a midline view of 13.040, from a male Tursiops aduncus collected on 11 April 2013 at West beach St Vincent Gulf, South Australia, and preserved in formalin.  The body length was measured at 1480 mm and the body weighed 38 kg.

The positions of presumptive auditory and visual cortices have been indicated on the surface of the highly folded (gyrified) cerebral cortex (see plates 1 and 2; Berns et al. 2015).  Note the large size of the inferior colliculus (see plate 3), a midbrain auditory centre.  The corpus callosum (plate 3) is very small for the size of the cerebrum, suggesting minimal interhemispheric transfer of information.  The pontine nuclei (plates 1, 3) and cerebellar hemispheres (plates 1, 2) are large, suggesting enlargement of the corticopontocerebellar system.

Acknowledgements

I would like to thank David Stemmer and Catherine Kemper of the South Australian Museum for access to photograph the specimens.

 References

Berns GS, Cook PF, Foxley S, Jbabdi S, Miller KL, Marino L. (2015) Diffusion tensor imaging of dolphin brains reveals direct auditory pathway to temporal lobe. Proc. Royal Soc London B. Biological Sciences. DOI: 10.1098/rspb.2015.1203