Diversity in sound pressure levels and estimated active space of resident killer whale vocalizations

Author Posting. © The Author, 2005. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Journal of Comparative Physiology A: Sensory, Neural, and Behavioral Physiology 192 (2006): 449-459, doi:10.1007/s00359-005-0085-2.Signal source intensity and detection range, which integrates source intensity with propagation loss, background noise and receiver hearing abilities, are important characteristics of communication signals. Apparent source levels were calculated for 819 pulsed calls and 24 whistles produced by free-ranging resident killer whales by triangulating the angles-of-arrival of sounds on two beamforming arrays towed in series. Levels in the 1-20 kHz band ranged from 131-168 dB re 1μPa @1m, with differences in the means of different sound classes (whistles: 140.2 ± 4.1 dB; variable calls: 146.6 ± 6.6 dB; stereotyped calls: 152.6 ± 5.9 dB), and among stereotyped call types. Repertoire diversity carried through to estimates of active space, with “long-range” stereotyped calls all containing overlapping, independently-modulated high-frequency components (mean estimated active space of 10-16km in sea state zero) and “short-range” sounds (5-9 km) included all stereotyped calls without a high-frequency component, whistles, and variable calls. Short-range sounds are reported to be more common during social and resting behaviors, while long-range stereotyped calls predominate in dispersed travel and foraging behaviors. These results suggest that variability in sound pressure levels may reflect diverse social and ecological functions of the acoustic repertoire of killer whales.Funding was provided by WHOI’s Ocean Ventures Fund and Rinehart Coastal Research Center and a Royal Society fellowship

Decoupling chemical and mechanical signaling in colorectal cancer cell migration

Abstract Colorectal cancer metastasis is governed by a variety of chemical and mechanical signaling that are largely influenced by cancer-associated fibroblasts (CAFs) in the tumor microenvironment. Here, we deconvolute the chemical from mechanical signaling in the case of the colon cancer cell line HCT-116 and CAFs. We examined three chemoattractants (CXCL12, TGF-β, and activin A) which allegedly are secreted by CAFs and induce HCT-116 cell migration. None of the chemoattractants tested resulted in enhanced migration of HCT-116 in a 2D transwell assay, at low cell density. Similarly, CAF-conditioned media also did not lead to enhanced HCT-116 migration, while CAFs co-cultured in the transwell assay did lead to increased HCT-116 migration. This result suggests that either high cell densities are required for chemotaxis, and/or a reciprocal two-way signaling network between CAFs and HCT-116 is necessary to induce chemotaxis. Surprisingly, we find that HCT-116 cells exhibit enhanced migration along the axis of mechanical stress in a 3D collagen matrix, at very high cell densities. This migration is independent of whether the strain is induced mechanically or by CAFs. By comparing purely mechanical and purely chemical migration to a 3D co-culture of CAFs and HCT-116 containing both chemical and mechanical cues, it is concluded that HCT-116 migration is dominated by mechanical signaling, while chemical cues are less influential