Diet, movement, and covering behavior of the sea urchin Toxopneustes roseus in rhodolith beds in the Gulf of California, México |
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Authors: | D W James |
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Institution: | (1) Moss Landing Marine Laboratories, P.O. Box 450, Moss Landing, CA 95039, USA Fax: +1-619-225-0340, US |
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Abstract: | The density, diet, movement, and covering behavior of Toxopneustes roseus (Agassiz) were investigated in rhodolith beds in the Gulf of California. Densities varied from a mean of 0.4 to 1.8/20 m2 with most urchins occurring in aggregations. Spatial patterns of urchins varied with depth, with greatest abundance at intermediate
depths (7.5–9.4 m) in the middle of the rhodolith bed. Urchins ate rhodoliths and nongeniculate coralline algal crusts almost
exclusively, despite the availability of other algae. The mean amounts ingested were 3.87 and 7.96 g carbonate/individual
per day. Even when food was abundant, animals were highly mobile, moving an average of 6.6–11.7 cm/h depending on site and
time of day. Diel movement may be a behavioral adaptation to avoid surge, which is greatest during the day. Covering behavior
may also be related to surge, as the ratio of covering material:body weight and the percent cover of material held were highest
at the site with the most surge. While an urchin consumed rhodoliths, its movement spread the grazing impact over large areas.
Bioturbation resulting from urchin feeding, movement, and covering activity probably benefits the rhodoliths by turning them,
which maintains rhodolith integrity, prevents fouling, and contributes to bed persistence.
Received: 22 February 1999 / Accepted: 3 July 2000 |
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