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Vol. 41 No. 1, 2002
Post-settlement Diet Shift of Chlorurus sordidus and Scarus schlegeli (Pisces: Scaridae)
Li-Shu Chen
Department of Marine Biology, James Cook University, Townsville QLD 4811, Australia
Li-Shu Chen (2002) Ontogenetic changes in the development of feeding structures and feeding habits of juvenile parrotfishes Chlorurus sordidus and Scarus schlegeli
(Family: Scaridae) were examined at Lizard Island on the northern Great
Barrier Reef, Australia. A shift from omnivorous feeding to feeding on
plant materials was observed, and this occurred over the size range of
15-30 mm TL. Ontogenetic changes were observed in teeth as well as in
gut coiling patterns. Individual teeth were present in newly settled
scarids (10 mm TL) but were totally lost when size increased to 26 mm
TL. The change in gut coiling patterns occurred mainly in the
mid-intestine, from being non-constricted to having a constricted ilial
wall. The tracts also changed from 1 sinistral loop to 2 loops by the
end of the observation period. The difference in gut length between the
2 species was caused by the different coiling patterns. Small
individuals (15 mm TL) of both species were omnivorous with diets
dominated by crustaceans and foraminifera. Significant increases in the
amounts of algal material and sediment taken were seen as fish grew.
With respect to microhabitat utilization, both species fed mainly on
dead coral and rocky substratum. Algae, with their associated high
density of crustaceans, were used by both species as a feeding
substratum when individuals were small (TL < 20 mm). Dietary changes
of post-settled C. sordidus and S. schlegeli were directly related to morphological changes in the alimentary tract rather than the differences of habitat utilization.
Key words: Digestive system, Parrotfish, Feeding habitats, Functional morphology, Foraging.
*Correspondence:
*Current address: National Museum of Marine Science and Technology -
Preparatory Office, PO Box 7-202, Keelung 202, Taiwan. Tel:
886-2-24631841 ext. 301 Fax: 886-2-24627716 E-mail:
Lschen@mail.ntou.edu.tw
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