chlorophyll-a and Starvation

Sacoglossan sea slugs are the only metazoans known to perform functional kleptoplasty, the sequestration and retention of functional chloroplasts within their digestive gland cells. Remarkably, a few species with this ability can survive starvation periods of 3-12 months likely due to their stolen chloroplasts. There are no reports of kleptoplast transfer from mother slug to either eggs or juveniles, demonstrating that each animal must independently acquire its kleptoplasts and develop the ability to maintain them within its digestive gland. We present here an investigation into the development of functional kleptoplasty in a long-term kleptoplast retaining species, Elysia timida. Laboratory-reared juvenile slugs of different post-metamorphic ages were placed in starvation and compared to 5 known short-term retaining slug species and 5 non-retaining slug species. The subsequent results indicate that functional kleptoplasty is not performed by E. timida until after 15 days post-metamorphosis and that by 25 days, these animals outlive many of the short-term retention species. Digestive activity was also monitored using lysosomal abundance as an indicator, revealing different patterns in starving juveniles versus adults. Starved juveniles were reintroduced to food to determine any differences in digestive activity when starvation ends, resulting in an increase in the number of kleptoplasts, but no overall change in lysosomal activity. By revealing some of the changes that occur during early development in these animals, which begin as non-kleptoplast-retaining and grow into long-term retaining slugs, this investigation provides a basis for future inquiries into the origin and development of this remarkable ability.

Topics: Animals; Chlorophyll; Chlorophyll A; Chloroplasts; Digestion; Feeding Behavior; Fluorometry; Gastropoda; Longevity; Lysosomes; Metamorphosis, Biological; Microscopy, Confocal; Species Specificity; Specimen Handling; Starvation; Time Factors

High density populations of the crown-of-thorns seastar, Acanthaster planci, are a major contributor to the decline of coral reefs, however the causes behind periodic outbreaks of this species are not understood. The enhanced nutrients hypothesis posits that pulses of enhanced larval food in eutrophic waters facilitate metamorphic success with a flow-on effect for population growth. The larval resilience hypothesis suggests that A. planci larvae naturally thrive in tropical oligotrophic waters. Both hypotheses remain to be tested empirically. We raised A. planci larvae in a range of food regimes from starvation (no food) to satiation (excess food). Algal cell concentration and chlorophyll levels were used to reflect phytoplankton conditions in nature for oligotrophic waters (0-100 cells ml(-1); 0-0.01 μg chl a L(-1)), natural background levels of nutrients on the Great Barrier Reef (GBR) (1,000-10,000 cells ml(-1); 0.1-1.0 μg chl a L(-1)), and enhanced eutrophic conditions following runoff events (100,000 cells ml(-1); 10 μg chl a L(-1)). We determine how these food levels affected larval growth and survival, and the metamorphic link between larval experience and juvenile quality (size) in experiments where food ration per larvae was carefully controlled. Phytoplankton levels of 1 μg chl a L(-1), close to background levels for some reefs on the GBR and following flood events, were optimal for larval success. Development was less successful above and below this food treatment. Enhanced larval performance at 1 μg chl a L(-1) provides empirical support for the enhanced nutrients hypothesis, but up to a limit, and emphasizes the need for appropriate mitigation strategies to reduce eutrophication and the consequent risk of A. planci outbreaks.

Topics: Animal Feed; Animals; Chlorophyll; Chlorophyll A; Coral Reefs; Larva; Metamorphosis, Biological; Satiation; Starfish; Starvation; Survival Analysis

Kleptoplasty is a particularly remarkable type of symbiosis, consisting of the presence of functional chloroplasts in the tissues of a host of another species. One of the most well-studied types of kleptoplasty is the association between sacoglossan molluscs (sea slugs) and algal chloroplasts. After ingestion, the chloroplasts remain photosynthetically functional and provide photosynthates to the host, therefore named as "solar-powered" sea slugs. This study evaluated the use of two optical methods, spectral reflectance analysis and in vivo Chl fluorescence, as measured by pulse amplitude modulated (PAM) fluorometry, for the in vivo quantification of kleptoplastic chlorophyll (Chl) a content in the sacoglossan Elysia viridis (Montagu, 1804) bearing chloroplasts of the macroalgae Codium tomentosum var. mucronatum (G. Hamel) Ardré. The Chl a content of E. viridis specimens was compared to a number of reflectance-based indices and to the dark-level fluorescence, F(o). Most reflectance-based indices varied linearly with the symbiosis Chl a content over the whole range of pigment content variation. Most significant correlations (P < 0.001) were found between indices using as reference the reflectance at 750 nm, with the proportion of pigment content explained by the indices varying between 63.5% and 85.9%. F(o) varied linearly with the Chl a content only for low pigment levels (below 4-6 microg Chl a per individual), above which it followed a saturation-like pattern. The use of optical methods was illustrated by monitoring the changes in Chl a content of specimens during periods of starvation and subsequent recovery. The results of this study suggest that, if basic requirements of signal detection and reproducible measuring geometry are verified, these optical methods may be readily applied to other photosynthetic symbioses.

Topics: Absorption; Animals; Chlorophyll; Chlorophyll A; Chlorophyta; Eating; Fluorometry; Gastropoda; Light; Light-Harvesting Protein Complexes; Optical Phenomena; Photosynthesis; Pigments, Biological; Solar Energy; Spectrometry, Fluorescence; Starvation; Symbiosis

In response to iron deficiency, cyanobacteria synthesize the iron stress-induced chlorophyll binding protein IsiA. This protein protects cyanobacterial cells against iron stress. It has been proposed that the protective role of IsiA is related to a blue light-induced nonphotochemical fluorescence quenching (NPQ) mechanism. In iron-replete cyanobacterial cell cultures, strong blue light is known to induce a mechanism that dissipates excess absorbed energy in the phycobilisome, the extramembranal antenna of cyanobacteria. In this photoprotective mechanism, the soluble Orange Carotenoid Protein (OCP) plays an essential role. Here, we demonstrate that in iron-starved cells, blue light is unable to quench fluorescence in the absence of the phycobilisomes or the OCP. By contrast, the absence of IsiA does not affect the induction of fluorescence quenching or its recovery. We conclude that in cyanobacteria grown under iron starvation conditions, the blue light-induced nonphotochemical quenching involves the phycobilisome OCP-related energy dissipation mechanism and not IsiA. IsiA, however, does seem to protect the cells from the stress generated by iron starvation, initially by increasing the size of the photosystem I antenna. Subsequently, the IsiA converts the excess energy absorbed by the phycobilisomes into heat through a mechanism different from the dynamic and reversible light-induced NPQ processes.

Topics: Bacterial Proteins; Chlorophyll; Energy Metabolism; Iron Deficiencies; Light; Light-Harvesting Protein Complexes; Photosystem II Protein Complex; Phycobilisomes; Spectrometry, Fluorescence; Starvation; Synechocystis

Topics: Carotenoids; Chlorophyll; Cyanobacteria; Nitrates; Phycocyanin; Pigments, Biological; Spectrometry, Fluorescence; Spectrum Analysis, Raman; Starvation

Topics: Animal Nutritional Physiological Phenomena; Animals; Carbon Radioisotopes; Carotenoids; Chlorophyll; Chloroplasts; Chromatography, Paper; Chromatography, Thin Layer; Diglycerides; Esterases; Fatty Acids, Nonesterified; Galactose; Glycolipids; Hydrolysis; Lipid Metabolism; Lipids; Lutein; Magnesium; Male; Pigments, Biological; Poaceae; Rumen; Sheep; Starvation