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Mora and colleagues show that ongoing greenhouse gas emissions are likely to have a considerable effect on several biogeochemical properties of the world's oceans, with potentially serious consequences for biodiversity and human welfare.

Investigations of the development of auditory form and function have, with a few exceptions, thus far been largely restricted to birds and mammals, making it difficult to postulate evolutionary hypotheses. Teleost fishes represent useful models for developmental investigations of the auditory system due to their often extensive period of posthatching development and the diversity of auditory specializations in this group. Using the auditory brainstem response and morphological techniques we investigated the development of auditory form and function in zebrafish (Danio rerio) ranging in size from 10 to 45 mm total length. We found no difference in auditory sensitivity, response latency, or response amplitude with development, but we did find an expansion of maximum detectable frequency from 200 Hz at 10 mm to 4000 Hz at 45 mm TL. The expansion of frequency range coincided with the development of Weberian ossicles in zebrafish, suggesting that changes in hearing ability in this species are driven more by development of auxiliary specializations than by the ear itself. We propose a model for the development of zebrafish hearing wherein the Weberian ossicles gradually increase the range of frequencies available to the inner ear, much as middle ear development increases frequency range in mammals.

Populations of many species are dramatically declining worldwide, but the causal mechanism remains debated among different human-related threats. Coping with this uncertainty is critical to several issues about the conservation and future of biodiversity, but remains challenging due to difficulties associated with the experimental manipulation and /or isolation of the effects of such threats under field conditions. Using controlled microcosm populations, we quantified the individual and combined effects of environmental warming, overexploitation and habitat fragmentation on population persistence. Individually, each of these threats produced similar and significant population declines, which were accelerated to different degrees depending upon particular interactions. The interaction between habitat fragmentation and harvesting generated an additive decline in population size. However, both of these threats reduced population resistance causing synergistic declines in populations also facing environmental warming. Declines in population size were up to 50 times faster when all threats acted together. These results indicate that species may be facing risks of extinction higher than those anticipated from single threat analyses and suggest that all threats should be mitigated simultaneously, if current biodiversity declines are to be reversed.

SUMMARYIt has recently been shown that a few fish species, including American shad(Alosa sapidissima; Clupeiformes), are able to detect sound up to 180 kHz, an ability not found in most other fishes. Initially, it was proposed that ultrasound detection in shad involves the auditory bullae, swim bladder extensions found in all members of the Clupeiformes. However, while all clupeiformes have bullae, not all can detect ultrasound. Thus, the bullae alone are not sufficient to explain ultrasound detection. In this study, we used a developmental approach to determine when ultrasound detection begins and how the ability to detect ultrasound changes with ontogeny in American shad. We then compared changes in auditory function with morphological development to identify structures that are potentially responsible for ultrasound detection. We found that the auditory bullae and all three auditory end organs are present well before fish show ultrasound detection behaviourally and we suggest that an additional specialization in the utricle(one of the auditory end organs) forms coincident with the onset of ultrasound detection. We further show that this utricular specialization is found in two clupeiform species that can detect ultrasound but not in two clupeiform species not capable of ultrasound detection. Thus, it appears that ultrasound-detecting clupeiformes have undergone structural modification of the utricle that allows detection of ultrasonic stimulation.

Costello et al. (Review, 25 January 2013, p. 413) challenged the common view that many species are disappearing before being described. We suggest that their conclusion is overly optimistic because of a limited selection and interpretation of available evidence that tends to overestimate rates of species description and underestimate the number of species on Earth and their current extinction rate.

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Many species of fish use auditory cues as part of their reproductive repertoire but intended receivers must be able to localize sounds to make full use of this information. Specialized couplings between the ear and swim bladder are thought to be critical for acoustic localization, yet species without specialized connections use acoustic cues in reproductive displays. In an attempt to better understand mechanisms of acoustic localization, we used the round goby (Neogobius melanostomus), a hearing generalist, to assess responses to calls in the lab and field. The call used for playback was recorded in the field from an actively displaying male round goby and consisted of a series of low frequency pulses. In the field, playback of the call resulted in a significant enhancement of approaches toward, and entries into, an experimental arena as compared to when the sound was off. There was no effect on the amount of time spent near the speaker however. In the lab, males and females responded actively when calls were played and females showed a significant attraction to the playing speaker. Responses were highly directional with little angular deviation, suggesting true localization to the sound source. While the sensory mechanisms allowing round gobies to selectively respond to conspecific vocalizations remain unknown, it is clear that they do show highly directional responses to acoustic cues in both laboratory and field settings.