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First published online August 8, 2003

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Hepoxilins and trioxilins in barnacles: an analysis of their potential roles in egg hatching and larval settlement

Claire L. Vogan¹, Ben H. Maskrey¹, Graham W. Taylor², Sheelagh Henry³, Cecil R. Pace-Asciak⁴, Anthony S. Clare³ and Andrew F. Rowley^1,*

¹ School of Biological Sciences, University of Wales Swansea, Singleton Park, Swansea, SA2 8PP, UK
² Proteomics Section, Imperial College, Faculty of Medicine, London, W12 ONN, UK
³ School of Marine Science and Technology, University of Newcastle upon Tyne, Newcastle upon Tyne, NE1 7RU, UK
⁴ Program in Integrative Biology, Research Institute, The Hospital for Sick Children, 555-University Avenue, Toronto and the Department of Pharmacology, University of Toronto, Toronto, Ontario M5G 1X8, Canada

View larger version (12K): [in a new window]   Fig. 1. The biosynthesis of hepoxilin A3 and its hydrolysis to trioxilin A3 from arachidonic acid, as reported by Pace-Asciak et al. (1983) in mammalian cells. 12-HPETE, 12-hydroperoxy-5,8,10,13-eicosatetraenoic acid; hepoxilin A3, 8-hydroxy-11,12-epoxy-5,9,14-eicosatrienoic acid; trioxilin A3, 8,11,12-trihydroxy-5,9,14-eicosatrienoic acid.

View larger version (22K): [in a new window]   Fig. 2. Ionophore challenge of E. modestus generates a number of A200 UV-absorbing species, as shown by the HPLC UV profile (A, top panel). Online analysis by negative ion electrospray mass spectrometry (A, bottom panel) highlights the presence of a species eluting at 16 min, which generates an intense M-H– ion at m/z 351 (inset). (B) The electron impact mass spectrum of the O-trimethylsilyl ether methyl ester derivative confirms the identity as trioxilin A4.

View larger version (22K): [in a new window]   Fig. 3. (A) Unsettled cypris larvae and (B) a recently settled juvenile, as observed in the settlement assays. Scale bars, 0.5 mm. (C) Percentage of settled B. amphitrite larvae when exposed to B. amphitrite larval extract (equivalent to products from 1000 cyprids well–1) and B. amphitrite adult extract (equivalent to products from 0.5 adults well–1). Effect of varying concentrations of (D) hepoxilin A3 and (E) PBT-3 on the percentage of larval settlement. Values represent arithmetic means + 1 S.E.M., for 10 day-0 cyprids after 48 h (N=3–19). Significant differences *P<0.05 from the methanol controls (open bars).

View larger version (100K): [in a new window]   Fig. 4. (A,B) Elminius modestus larval egg mass pre-hatching and (C,D)5 min after the addition of crude hatching factor. Note the change in the appearance of individual nauplii larvae pre(B) and post(D) hatching. Scale bars are 1 mm and 200 µm for A,B and C,D, respectively.

View larger version (16K): [in a new window]   Fig. 5. Percentage of hatched larvae from Elminius modestus egg masses when exposed to varying concentrations of (A) trioxilin A3 (B) hepoxilin A3 and (C) PBT-3. Open bars indicate each test compound and filled bars indicate the levels of hatching when the partner egg mass was exposed to the ethanol control. Values represent arithmetic means + 1 S.E.M. (N=3–6 for each of the concentrations tested). Asterisks indicate significant differences from ethanol controls at *P<0.05 and **P<0.01.