Parrotfish predation on cryptic sponges of Caribbean coral reefs |
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Authors: | J L Wulff |
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Institution: | (1) Smithsonian Tropical Research Institute, Apartado 2072, Balboa, Republica de Panama, PA |
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Abstract: | Some sponge species that live in crevices in the reef frame appear to be restricted to their cryptic habitat by predation.
When cryptic sponges were excavated, on Guigalotupo reef, San Blas, Panama, exposing them to potential predators, they were
eaten by fishes that are generally considered to be herbivores, primarily parrotfishes of the genus Sparisoma: S.aurofrenatum (Cuvier & Valenciennes), S.viride (Bonnaterre), and S.chrysopterum (Bloch & Schneider). Of the 9150 bites observed to be taken by these species during paired (i.e., with sponges versus without
sponges) trials conducted in defined feeding areas during 1986, 1987, and 1988, 72% (i.e. 6581 bites) were on cryptic sponges,
even though these were only offered during half of the total observation time and never constituted more than 7% of the cover
of the feeding observation areas. Individual parrotfish returned over and over to take bites of the exposed cryptic sponges
until they were entirely consumed. They vigorously chased each other away from the sponges, but exhibited no such defense
of their usual algal foods. A total of 18 sponge species were tested. Of the cryptic and semi-cryptic sponge species tested,
only one of six was rejected by the parrotfish. Two of these six sponge species were consistently consumed entirely, and two
were consumed entirely whenever their surfaces were sliced off with a razor blade, demonstrating that these sponges concentrate
defenses against predators in their surfaces. One semi-cryptic species and one semi-exposed species were fed upon, but not
entirely consumed. By contrast, 11 of 12 of the exposed and semi-exposed species were rejected. Cryptic sponges grew out of
their cavities in the reef only when protected by seasonally thick mats of macroalgae or by cages that excluded fish.
Received: 10 January 1997 / Accepted: 4 February 1997 |
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