External chemical signals provide a mechanism for broadcast-spawning scleractinian corals to recognise suitable substrata for larval settlement and metamorphosis. These morphogens can be extracted from crustose coralline algae (CCA) and the skeletons of some coral species, however the precise origin of the chemical inducers has not yet been conclusively demonstrated. Microorganisms have been reported to induce metamorphosis in various species of echinoderms, molluscs, polychaetes and cnidarians. We report that Strain A3, a species of Pseudoalteromonas isolated from the CCA Hydrolithon onkodes (Heydrich), was able to induce significant levels (up to 51.5% ± 5.8 SE) of metamorphosis of Acropora willisae Veron & Wallace, 1984 and A. millepora (Ehrenberg, 1834) larvae in laboratory assays. This experiment was repeated daily over 4 d, and the spat developed normally into juvenile polyps in flow-through aquaria. Approximately the same number of larvae underwent partial metamorphosis, forming flattened discs that were not attached to the substrata. Larvae underwent full settlement, attachment and metamorphosis only in the presence of Pseudoalteromonas A3 plus inert chips of the coral skeleton Porites sp., indicating that the calcareous matrix may play a role in the synthesis of inducers from Pseudoalteromonas Strain A3. This discovery provides evidence for a widening range of morphogenic sources and demonstrates the role that microorganisms may play in fine-scale coral recruitment. In addition, the synthesis of chemical inducers by Pseudoalteromonas Strain A3 may have biotechnological applications for reef re-seeding. KEY WORDS: Coral · Metamorphosis · Settlement · BacteriaResale or republication not permitted without written consent of the publisher
Toxic freshwater cyanobacteria can contaminate water supplies and adversely effect humans, agricultural livestock, and wildlife. Toxicity is strain-specific so morphological observations alone cannot predict the hazard level. Two microtiter plate based bioassays have emerged for measuring saxitoxin (STX) and its derivatives, commonly found in the freshwater cyanobacteria Anabaena and Aphanizomenon. They use radioactively labeled STX binding by sodium channels, STX's pharmacological target, or an unrelated protein, saxiphilin. These bioassays were challenged with extracts of toxic and nontoxic strains of Anabaena circinalis, and the results were compared with HPLC analysis. Both radioreceptor assays had detection limits of 2 microg STX equivalents (STXeq)/L, which is belowthe concentration proposed for a health alert, namely 3 microg STXeq/L. In all cases, statistically significant correlations existed between all toxicity measurements of the same extracts with the methods used herein. Sodium channel and saxiphilin assays however predicted less toxicity relative to HPLC analysis. The only exception to this was the equivalency observed between saxiphilin measurement and HPLC quantitation corrected for mammalian toxicity. Saxiphilin assay predicted toxicity in one strain was 3 orders of magnitude more than by sodium channel assay, and no STX was detected by HPLC. Lack of acetylcholinesterase inhibition showed this bioactivity was not anatoxin-a(S), a toxin also produced by this A. circinalis with some resemblance to the region of STX bound by saxiphilin. Presence of anatoxin-a(S) was predicted for another strain by this same acetylcholinesterase assay that, if confirmed by chemical analysis, would be the first report of anatoxin-a(S) in an Australian cyanobacterium.
The wool fibre contains a fatty acid component which can only be liberated from the fibre by treatment with alcoholic alkali solutions. The major fatty acid from this component has been isolated in quantity and purified. Using GC/MS and NMR, the fatty acid was identified as 18-methyleicosanoic acid. The results obtained from transesterification experiments suggest that the fatty acid is covalently bound to the fibre protein by an ester linkage.
Climate change impacts and light attenuation from suspended sediments, due to runoff, natural resuspension or dredging, can both impede the replenishment of coral populations. Here we tested the independent and combined impacts of climate change (current temperature and dissolved CO2, and 2 future climate scenarios) and a 1 mo long light attenuation period at 5 different light levels (0.1 to 4 mol photons m-2 d-1) on early Acropora millepora recruits. Additionally, we evaluated whether the effects were age dependent by comparing responses of recruits that were 1 mo old (‘early attenuation’) vs. 2 mo old (‘late attenuation’). Recruit survival, size and Symbiodiniaceae densities increased slightly under moderate future climate conditions (current temperature +0.44°C, 692 ppm pCO2), but decreased under a more severe climate scenario (+0.94°C, 985 ppm pCO2). Light attenuation significantly decreased recruit survival, size and Symbiodiniaceae densities only for recruits exposed to the late attenuation, suggesting an increasing reliance on photosynthesis as recruits age. Under the more severe climate scenario tested, recruit survival was diminished by both climate change (≤18 ± 4% [SE] in the early attenuation) and light limitation (≤32 ± 6% in the late attenuation) compared with controls. However, there was no interaction between future climate scenarios and light attenuation, indicating that these effects were additive. This study demonstrates the potential effects of light limitation and future climate conditions on coral recruitment success and highlights the need to manage the timing of sediment-generating activities near reefs to optimise light availability for several months post settlement.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.