Porosity Controls Spread of Excitation in Tectorial Membrane Traveling Waves

Cochlear frequency selectivity plays a key role in our ability to understand speech, and is widely believed to be associated with cochlear amplification. However, genetic studies targeting the tectorial membrane (TM) have demonstrated both sharper and broader tuning with no obvious changes in hair bundle or somatic motility mechanisms. For example, cochlear tuning of Tectb[superscript –/–] mice is significantly sharper than that of Tecta[superscript Y1870C/+] mice, even though TM stiffnesses are similarly reduced relative to wild-type TMs. Here we show that differences in TM viscosity can account for these differences in tuning. In the basal cochlear turn, nanoscale pores of Tecta[superscript Y1870C/+] TMs are significantly larger than those of Tectb[superscript –/–] TMs. The larger pore size reduces shear viscosity (by ∼70%), thereby reducing traveling wave speed and increasing spread of excitation. These results demonstrate the previously unrecognized importance of TM porosity in cochlear and neural tuning.National Institutes of Health (U.S.) (Grant R01-DC00238)National Science Foundation (U.S.). Graduate Research Fellowship Program (Grant 1122374)National Institutes of Health (U.S.) (Training Grant

\u3ci\u3eScaphanocephalus\u3c/i\u3e-Associated Dermatitis as the Basis for Black Spot Disease in Acanthuridae of St. Kitts, West Indies

Acanthurus spp. of St. Kitts and other Caribbean islands, including ocean surgeonfish A. bahianus, doctorfish A. chirurgus, and blue tang A. coeruleus, frequently show multifocal cutaneous pigmentation. Initial reports from the Leeward Antilles raised suspicion of a parasitic etiology. The aim of this study was to quantify the prevalence of the disease in St. Kitts’ Acanthuridae and describe its pathology and etiology. Visual surveys demonstrated consistently high adjusted mean prevalence at 3 shallow reefs in St. Kitts in 2017 (38.9%, 95% CI: 33.8−43.9) and 2018 (51.5%; 95% CI: 46.2−56.9). There were no differences in prevalence across species or reefs, but juvenile fish were less commonly affected than adults. A total of 29 dermatopathy-affected acanthurids were sampled by spearfishing for comprehensive postmortem examination. Digenean metacercariae were dissected from \u3c1 mm cysts within pigmented lesions. Using partial 28S rDNA sequence data they were classified as Family Heterophyidae, members of which are commonly implicated in black spot disease of other fishes. Morphological features of the parasite were most typical of Scaphanocephalus spp. (Creplin, 1842), and 2 genetic profiles were obtained suggesting more than 1 digenean species. Histologically, pigmented lesions had mild chronic perivascular dermatitis and increased melanophores and melanin density, often centered on encysted digenean metacercariae. In 1 affected A. chirurgus, similar metacercariae were histologically identified in skeletal and cardiac muscle. Further research is needed to clarify impact on host fitness, establish the number of heterophyid digenean species that cause black spots on Caribbean fishes and to determine the intermediate and definitive host species

Col11a2 Deletion Reveals the Molecular Basis for Tectorial Membrane Mechanical Anisotropy

The tectorial membrane (TM) has a significantly larger stiffness in the radial direction than other directions, a prominent mechanical anisotropy that is believed to be critical for the proper functioning of the cochlea. To determine the molecular basis of this anisotropy, we measured material properties of TMs from mice with a targeted deletion of Col11a2, which encodes for collagen XI. In light micrographs, the density of TM radial collagen fibers was lower in Col11a2 –/– mice than wild-types. Tone-evoked distortion product otoacoustic emission and auditory brainstem response measurements in Col11a2 –/– mice were reduced by 30–50 dB independent of frequency as compared with wild-types, showing that the sensitivity loss is cochlear in origin. Stress-strain measurements made using osmotic pressure revealed no significant dependence of TM bulk compressibility on the presence of collagen XI. Charge measurements made by placing the TM as an electrical conduit between two baths revealed no change in the density of charge affixed to the TM matrix in Col11a2 –/– mice. Measurements of mechanical shear impedance revealed a 5.5 ± 0.8 dB decrease in radial shear impedance and a 3.3 ± 0.3 dB decrease in longitudinal shear impedance resulting from the Col11a2 deletion. The ratio of radial to longitudinal shear impedance fell from 1.8 ± 0.7 for TMs from wild-type mice to 1.0 ± 0.1 for those from Col11a2 –/– mice. These results show that the organization of collagen into radial fibrils is responsible for the mechanical anisotropy of the TM. This anisotropy can be attributed to increased mechanical coupling provided by the collagen fibrils. Mechanisms by which changes in TM material properties may contribute to the threshold elevation in Col11a2 –/– mice are discussed.National Institutes of Health (U.S.) (Grant R01-DC00238

Garden varieties: how attractive are recommended garden plants to butterflies?

One way the public can engage in insect conservation is through wildlife gardening, including the growing of insect-friendly flowers as sources of nectar. However, plant varieties differ in the types of insects they attract. To determine which garden plants attracted which butterflies, we counted butterflies nectaring on 11 varieties of summer-flowering garden plants in a rural garden in East Sussex, UK. These plants were all from a list of 100 varieties considered attractive to British butterflies, and included the five varieties specifically listed by the UK charity Butterfly Conservation as best for summer nectar. A total of 2659 flower visits from 14 butterfly and one moth species were observed. We performed a principal components analysis which showed contrasting patterns between the species attracted to Origanum vulgare and Buddleia davidii. The “butterfly bush” Buddleia attracted many nymphalines, such as the peacock, Inachis io, but very few satyrines such as the gatekeeper, Pyronia tithonus, which mostly visited Origanum. Eupatorium cannibinum had the highest Simpson’s Diversity score of 0.75, while Buddleia and Origanum were lower, scoring 0.66 and 0.50 respectively. No one plant was good at attracting all observed butterfly species, as each attracted only a subset of the butterfly community. We conclude that to create a butterfly-friendly garden, a variety of plant species are required as nectar sources for butterflies. Furthermore, garden plant recommendations can probably benefit from being more precise as to the species of butterfly they attract

Robust statistical properties of the size of large burst events in AE

Geomagnetic indices provide a comprehensive data set with which to quantify space climate, that is, how the statistical likelihood of activity varies with the solar cycle. We characterize space climate by the AE index burst distribution. Burst sizes are constructed by thresholding the AE time series; a burst is the sum of the excess in the time series for each time interval over which the threshold is exceeded. The distribution of burst sizes is two component with a crossover in behavior at thresholds ≈1000 nT. Above this threshold, we find a range over which the mean burst size varies weakly with threshold for both solar maxima and minima. The burst size distribution of the largest events is exponential. The relative likelihood of these large events varies from one solar maximum and minimum to the next. Given the relative overall activity of a solar maximum/minimum, these results constrain the likelihood of extreme events of a given size

Robust statistical properties of the size of large burst events in AE

Geomagnetic indices provide a comprehensive data set with which to quantify space climate, that is, how the statistical likelihood of activity varies with the solar cycle. We characterize space climate by the AE index burst distribution. Burst sizes are constructed by thresholding the AE time series; a burst is the sum of the excess in the time series for each time interval over which the threshold is exceeded. The distribution of burst sizes is two component with a crossover in behavior at thresholds ≈1000 nT. Above this threshold, we find a range over which the mean burst size varies weakly with threshold for both solar maxima and minima. The burst size distribution of the largest events is exponential. The relative likelihood of these large events varies from one solar maximum and minimum to the next. Given the relative overall activity of a solar maximum/minimum, these results constrain the likelihood of extreme events of a given size