Mechanoreception, a possible mechanism for food fall detection in deep-sea scavengers

There is strong evidence in the literature that energy supply for deep-sea scavengers is largely restricted to food falls of dead vertebrates such as fish and mammals. The problem for any scavenger inhabiting the seafloor is the unpredictability both in space and time of food fall events. It is generally accepted that chemoreception is one of the major means by which marine organisms detect food sources. Another major source of potential information, however, may come from hydroacoustic stimuli, which have long-range penetration. Such hydroacoustic stimuli will either arise when a large carcass hits and impacts the seafloor or during food consumption of scavengers producing feeding noises. The intensity and transmission characteristics depend upon sediment properties, size, weight and composition of the carcass as well as on size and mouthpart morphology of feeding individuals. In this study the relevance of hydroacoustic stimuli for food fall detection has been investigated in the pandalid shrimp Pandalus borealis Kroyer, 1838. The sensitivity of P. borealis to particle displacement amplitude was found to be close to values measured in other crustaceans. Based on 228 single experiments carried out with five specimens, our results indicate that low-frequency noises may be helpful in detecting food fall events but only in the near-field. In this paper we suggest that the impact of a sinking carcass at the seafloor is a likely source producing elastic waves at the water-seafloor interface. Based on both empirical findings and general theoretical calculations of elastic waves originating from a sinking object hitting the seafloor we conclude that such micro seismic events may allow resting scavengers even several hundred metres away to detect a food source. (C) 2001 Elsevier Science Ltd. All rights reserved.