Comp. Biochem. Physiol.,
1975,
Vol.
52B, pp. 339
to 340. Per#amon Press. Printed in Great Britain
SHORT C O M M U N I C A T I O N WAX DIGESTION IN A CROWN-OF-THORNS STARFISH A . A . BENSON, J. S. P A T T O N , A N D C . E . F I E L D
Scripps Institution of Oceanography, La Jolla, CA 92037, U.S.A. (Received 2 July 1974) Abstract--Digestive enzymes of Acanthaster ellisii are exceptionally effective in hydrolyzing a wax ester, cetyl palmitate, the major energy reserve of reef corals.
INTRODUCTION
RESULTS AND DISCUSSION
Wax ester lipase activity of Acanthaster ellisii tissue was exceptionally active and differed remarkably from mammalian pancreatic lipase specificity. Other starfish species investigated failed to hydrolyze wax ester. Lipases have been reported in Asteroidae but their activities and importance are considered equivocal (Ferguson, 1969; Allen & Giese, 1966). Apparently Acanthaster is unique among starfish in its ability to utilize wax ester. Further, the rates of wax ester hydrolysis relative to those for triglyceride are greater with the Acanthaster lipase than they are for pyloric cecum and biliary lipases of the anchovy and sardine, fishes which are adapted to copepod diets rich in wax esters. Cetyl palmitate is produced by corals and stored as a major energy reserve. It accumulates in such large amounts that crude extracts of corals can crystallize directly when they are concentrated (Lester & Bergmann, 1941; Benson & Muscatine, 1974). Acanthaster has the digestive enzymes necessary to utilize this wax ester and, together with its proteolytic activities completely denudes the coral of its living tissue, leaving the calcareous skeleton to be destroyed by boring organisms and storms.
THE FEEDING habits of the Crown-of-Thorns starfish, Acanthaster planci, a voracious predator of Indo-Pacific reef corals (Endean, 1973) indicate that the major part of its energy supply is derived from coral tissues. This diet includes several unusual components, the metabolism of which may indicate dietary preferences and requirements of this starfish. We have found that the abundant coral wax ester, cetyl palmitate (C15H31CH2-O-CO-C15H31) was readily hydrolyzed by digestive organ tissue of Acanthaster ellisii (Barham et al., 1973), a tropical Eastern Pacific relative of A. planci which also feeds primarily on reef coral. MATERIALS AND METHODS
Pyloric cecum tissue (200 mg) of A. ellisii (Bahia de Los Frailes, Baja California, Mexico) was homogenized with 10/tCi cetyl 14C-palmitate suspended in 50mg egg yolk and incubated at room temperature. Samples taken at 0.3 and 2.0 hr were heated briefly with ethanol and the extent of hydrolysis was determined by extraction and assay of freed 14C-palmitic acid. The labeled ester was 10~o hydrolyzed in 20 min and 60~o hydrolyzed in 2 hr. In similar experiments homogenates and acetone powders of A. ellisii were shaken 30 min with 14C-triolein and oleyl 3H-oleate in 0-05 M Tris pH 7.0 buffer containing 0.1 M sodium chloride and 0.02 M calcium chloride in capped vials at 15,000 osc/ min. Positional specificity of triglyceride hydrolysis was determined using rac-l-palmityl-2-oleyl-3-stearyl glycerol. Liberated fatty acids were assayed by gas chromatography. Hydrolyses of the wax esters and triglyceride are recorded in Table 1.
Acknowledgements--This work was supported by National Science Foundation grants GB 24834 and GD 41402 and initiated aboard R/V Dolphin of this Institution. The authors are indebted to Dr. J. C. Nevenzel for preparation of labeled wax esters and for valuable advice.
Table 1. Relative activities and specificities of wax and triglyceride lipases from Acanthaster ellisii, three other starfish, and vertebrate sources
Lipasesource Acanthaster eUisii Pisaster ochraceus Astropectin armatu~ Patiria miniata
Anchovy bile Mackerel intestinal fluid Hog pancreatic lipase
15 min
Wax ester !!;, hydrolysis 30 min
15
2 hr 60
Triglyceride positional I'~,hydrolysis 1 2 3 46
18
36
0 0 0
--
30 30 5
46
24
30
51
tr
49
Ratio wax ester: triglyeeride 1,3 -----
0.82 0.22 0.05
Substrates were oleyl 3H-oleate, 14C-triolein, and, in the initial A. ellisii experiment, cetyl ~C-palmitate. Positional specifcity of triglyceride hydrolysis was determined using gas chromatographic analyses of the fatty acids freed from rac-1pamityl-2-oleyl-3-stearyl-glycerol. 339
340
A.A. BENSON, J. S. PATTON, AND C. E. FIELD REFERENCES
ALLEN W. V. & GIESEA. C. (1966)An in vitro study of lipogenesis in the sea star, Pisaster ochraceus. Comp. Biochem. Physiol. 17, 23 38. BARHAM E. G.. GowI)Y R. W. • WOEFSON F. H. (1973) Acamhaster (Echinodermata; Asteroidea) in the Gulf of California. U.S. National Marine Fisheries Service. Fish. Bull. 71,927-942. BF.NSONA. A. & MUSCATINEL. (1974) Wax in coral mucus: Energy transfer flom corals to reef fishes. Li,mol. and Oceano~l 19. 81(~814. ENDEAN R. (1973) Population explosions of Aeanthaster planci and associated destruction of hermatypic corals in
the Indo-West Pacific region. In Biology and Geology of Coral Reefs. (Edited by Jones O. A. & Endean R.) Vol. 1I, pp. 389 438. Academic Press, New York, London. FERGUSON J. C. (1969) Feeding, digestion, and nutrition in Echinodermata. In Chemical Zoology. (Edited by Florkin M. & Scheer B. T.) Vol. III, pp. 71 100. Academic Press, New York, London. LESTER D. & BERGMANN W. (1941) Contributions to the study of marine products. VI. The occurrence of cetyl palmitate in corals. J. Org. Chem. 6, 120-122.
Key Word Index--Wax ester; cetyl palmitate; Acanthaster; Crown-of-Thorns starfish; asteroids; digestion.
1975,
Vol.
52B, pp. 339
to 340. Per#amon Press. Printed in Great Britain
SHORT C O M M U N I C A T I O N WAX DIGESTION IN A CROWN-OF-THORNS STARFISH A . A . BENSON, J. S. P A T T O N , A N D C . E . F I E L D
Scripps Institution of Oceanography, La Jolla, CA 92037, U.S.A. (Received 2 July 1974) Abstract--Digestive enzymes of Acanthaster ellisii are exceptionally effective in hydrolyzing a wax ester, cetyl palmitate, the major energy reserve of reef corals.
INTRODUCTION
RESULTS AND DISCUSSION
Wax ester lipase activity of Acanthaster ellisii tissue was exceptionally active and differed remarkably from mammalian pancreatic lipase specificity. Other starfish species investigated failed to hydrolyze wax ester. Lipases have been reported in Asteroidae but their activities and importance are considered equivocal (Ferguson, 1969; Allen & Giese, 1966). Apparently Acanthaster is unique among starfish in its ability to utilize wax ester. Further, the rates of wax ester hydrolysis relative to those for triglyceride are greater with the Acanthaster lipase than they are for pyloric cecum and biliary lipases of the anchovy and sardine, fishes which are adapted to copepod diets rich in wax esters. Cetyl palmitate is produced by corals and stored as a major energy reserve. It accumulates in such large amounts that crude extracts of corals can crystallize directly when they are concentrated (Lester & Bergmann, 1941; Benson & Muscatine, 1974). Acanthaster has the digestive enzymes necessary to utilize this wax ester and, together with its proteolytic activities completely denudes the coral of its living tissue, leaving the calcareous skeleton to be destroyed by boring organisms and storms.
THE FEEDING habits of the Crown-of-Thorns starfish, Acanthaster planci, a voracious predator of Indo-Pacific reef corals (Endean, 1973) indicate that the major part of its energy supply is derived from coral tissues. This diet includes several unusual components, the metabolism of which may indicate dietary preferences and requirements of this starfish. We have found that the abundant coral wax ester, cetyl palmitate (C15H31CH2-O-CO-C15H31) was readily hydrolyzed by digestive organ tissue of Acanthaster ellisii (Barham et al., 1973), a tropical Eastern Pacific relative of A. planci which also feeds primarily on reef coral. MATERIALS AND METHODS
Pyloric cecum tissue (200 mg) of A. ellisii (Bahia de Los Frailes, Baja California, Mexico) was homogenized with 10/tCi cetyl 14C-palmitate suspended in 50mg egg yolk and incubated at room temperature. Samples taken at 0.3 and 2.0 hr were heated briefly with ethanol and the extent of hydrolysis was determined by extraction and assay of freed 14C-palmitic acid. The labeled ester was 10~o hydrolyzed in 20 min and 60~o hydrolyzed in 2 hr. In similar experiments homogenates and acetone powders of A. ellisii were shaken 30 min with 14C-triolein and oleyl 3H-oleate in 0-05 M Tris pH 7.0 buffer containing 0.1 M sodium chloride and 0.02 M calcium chloride in capped vials at 15,000 osc/ min. Positional specificity of triglyceride hydrolysis was determined using rac-l-palmityl-2-oleyl-3-stearyl glycerol. Liberated fatty acids were assayed by gas chromatography. Hydrolyses of the wax esters and triglyceride are recorded in Table 1.
Acknowledgements--This work was supported by National Science Foundation grants GB 24834 and GD 41402 and initiated aboard R/V Dolphin of this Institution. The authors are indebted to Dr. J. C. Nevenzel for preparation of labeled wax esters and for valuable advice.
Table 1. Relative activities and specificities of wax and triglyceride lipases from Acanthaster ellisii, three other starfish, and vertebrate sources
Lipasesource Acanthaster eUisii Pisaster ochraceus Astropectin armatu~ Patiria miniata
Anchovy bile Mackerel intestinal fluid Hog pancreatic lipase
15 min
Wax ester !!;, hydrolysis 30 min
15
2 hr 60
Triglyceride positional I'~,hydrolysis 1 2 3 46
18
36
0 0 0
--
30 30 5
46
24
30
51
tr
49
Ratio wax ester: triglyeeride 1,3 -----
0.82 0.22 0.05
Substrates were oleyl 3H-oleate, 14C-triolein, and, in the initial A. ellisii experiment, cetyl ~C-palmitate. Positional specifcity of triglyceride hydrolysis was determined using gas chromatographic analyses of the fatty acids freed from rac-1pamityl-2-oleyl-3-stearyl-glycerol. 339
340
A.A. BENSON, J. S. PATTON, AND C. E. FIELD REFERENCES
ALLEN W. V. & GIESEA. C. (1966)An in vitro study of lipogenesis in the sea star, Pisaster ochraceus. Comp. Biochem. Physiol. 17, 23 38. BARHAM E. G.. GowI)Y R. W. • WOEFSON F. H. (1973) Acamhaster (Echinodermata; Asteroidea) in the Gulf of California. U.S. National Marine Fisheries Service. Fish. Bull. 71,927-942. BF.NSONA. A. & MUSCATINEL. (1974) Wax in coral mucus: Energy transfer flom corals to reef fishes. Li,mol. and Oceano~l 19. 81(~814. ENDEAN R. (1973) Population explosions of Aeanthaster planci and associated destruction of hermatypic corals in
the Indo-West Pacific region. In Biology and Geology of Coral Reefs. (Edited by Jones O. A. & Endean R.) Vol. 1I, pp. 389 438. Academic Press, New York, London. FERGUSON J. C. (1969) Feeding, digestion, and nutrition in Echinodermata. In Chemical Zoology. (Edited by Florkin M. & Scheer B. T.) Vol. III, pp. 71 100. Academic Press, New York, London. LESTER D. & BERGMANN W. (1941) Contributions to the study of marine products. VI. The occurrence of cetyl palmitate in corals. J. Org. Chem. 6, 120-122.
Key Word Index--Wax ester; cetyl palmitate; Acanthaster; Crown-of-Thorns starfish; asteroids; digestion.
