Internally coupled ears in living mammals.

It is generally held that the right and left middle ears of mammals are acoustically isolated from each other, such that mammals must rely on neural computation to derive sound localisation cues. There are, however, some unusual species in which the middle ear cavities intercommunicate, in which case each ear might be able to act as a pressure-difference receiver. This could improve sound localisation at lower frequencies. The platypus Ornithorhynchus is apparently unique among mammals in that its tympanic cavities are widely open to the pharynx, a morphology resembling that of some non-mammalian tetrapods. The right and left middle ear cavities of certain talpid and golden moles are connected through air passages within the basicranium; one experimental study on Talpa has shown that the middle ears are indeed acoustically coupled by these means. Having a basisphenoid component to the middle ear cavity walls could be an important prerequisite for the development of this form of interaural communication. Little is known about the hearing abilities of platypus, talpid and golden moles, but their audition may well be limited to relatively low frequencies. If so, these mammals could, in principle, benefit from the sound localisation cues available to them through internally coupled ears. Whether or not they actually do remains to be established experimentally.This is the final version of the article. It first appeared from Springer via http://dx.doi.org/10.1007/s00422-015-0675-

Nutrients and eutrophication: introduction

Cultural eutrophication stimulated by anthropogenic-derived nutrients represents one of the most common forms of compromised surface water quality in many developed and developing countries (Schindler 2012). In fresh water, both nitrogen (N) and phosphorus (P) can potentially contribute to eutrophication (Carpenter et al. 1998). In lakes it is more common that excessive P inputs are the primary cause of eutrophication (Schindler 1977) although both global (Elser et al. 2007) and national surveys (Abell et al. 2011a) have increasingly highlighted excessive N inputs as an equal or more important cause. Debate on the relative roles of N and P limitation of lake phytoplankton is highly contentious, with a P-limitation paradigm (Schindler et al. 2008) challenged by those who contend that both P and N control are key elements of eutrophication management in freshwater systems (e.g. Conley et al. 2009; Scott and McCarthy 2010). Eutrophication of temperate estuaries and coastal waters is also common, but in contrast to fresh water, N is more commonly the controlling nutrient (Carpenter et al. 1998)