Dr. Matthew Mason: Further Information...
University Physiologist Tel: +44 (0)1223 333829, Fax: +44 (0)1223 333840, E-mail: mjm68@cam.ac.uk
Mason, M.J. (2006) Evolution of the middle ear apparatus in talpid moles. Journal of Morphology 267: 678-695.
In this paper, I consider in detail the middle ear morphology of talpid moles, familiar animals in Eurasia and North America. Moles are classified into three groups, based on their middle ear structures. The group 1 moles, which tend to show some above-ground activity, include Neurotrichus, Parascalops and Condylura. Their middle ear structures are the least derived from those of their relatives, shrews and hedgehogs, and include features such as incomplete auditory bullae, "microtype" ossicles and retained tensor tympani muscles. Group 2 moles such as Talpa, Scalopus and Scapanus are highly subterranean: they have complete bullae, "freely mobile" ossicles and have lost their tensor tympani muscles. Group 3 includes only the little-known Asian genera Parascaptor and Scaptochirus, which have hypertrophied ossicles. The diversity of middle ear morphologies within one family allows us better to examine evolutionary pathways: group 2 moles may have evolved better low-frequency hearing associated with increased time spent underground compared to group 1, while group 3 moles, which have evolved ossicular hypertrophy in parallel with golden moles (Chrysochloridae), are interpreted as bone-conduction specialists.
The comparison between talpid mole ears and golden mole middle ears is taken further in Mason (2007).
I remark in this paper that, in fossorial rodents, if a middle ear muscle is lost it is always the stapedius. However, I have subsequently found that the mole-rats Spalax and Eospalax lack the tensor tympani muscle: see Mason et al. (2010) for more information.
To access this paper via the Journal of Morphology website, please click here.
Please contact me if you would like to be sent a reprint copy of this paper.