Experiments with the behaviour of the bivalves Montacuta substriata and M. ferruginosa, 'commensals' with spatangoids
Gage, J. (1966) Experiments with the behaviour of the bivalves Montacuta substriata and M. ferruginosa, 'commensals' with spatangoids. Journal of the Marine Biological Association of the United Kingdom, 46 (1). pp. 71-88.
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The behaviour involved in the maintenance of the 'commensal' associatIons of Montacuta substriata and M. ferruginosa with spatangoids was investigated experimentally. Both species are highly mobile when isolated from the' host', and this activity was recorded through their mucous trails on glass plates, and photographically with a repetitive electronic flash system. Their responses were analysed mainly in a trough apparatus with a slow flow of water. The behaviour was resolved into responses to factors normally present in their environment. These included both gravity and water currents and a chemical influence from the' host' spatangoid. M. substriata showed a marked negative geotaxis, while M. ferruginosa showed a similar response but of opposite sign. Pedal activity was stimulated as a kinesis to an unknown chemical 'attractant' from the urchin. The bivalves showed no specificity in this response since it was shown by both species to any of the spatangoids tested, regardless of the urchin species from which they were taken. A rheotaxis to the water currents derived from the burrowed spatangoid probably functions in providing a directional component to the chemo-kinesis. Together with the gravity reactions, the role of these responses in nature, in maintaining their associations with the 'host', and in reassociating with different individuals, is discussed. Some of the possible causes of the apparent absence of, first, the smallest M. ferruginosa with the deep-burrowing sand urchin Echinocardium cordatum, and, secondly, of large individuals with spatangoids burrowing in shell gravel are discussed.
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