A large literature documents that betaines play significant roles in protecting photosynthesis in the face of multiple stresses, including heat and photon stresses, in terrestrial plants and free-living algae. Betaines therefore can be expected to defend against photosystem stresses (e.g. photoinhibition and bleaching) in reef-building corals and tridacnid clams (both symbiotic with algae) in addition to functioning as osmolytes employed in osmotic stress defense. Nonetheless, the presence of betaines has just started to be studied in corals and has never before been investigated in tridacnids. The present research demonstrates the following. (1) Betaines, especially aminovaleric acid betaine and glycine betaine (GlyB), are abundant metabolites in all 4 major tissues of 5 tridacnid species studied. (2) Pacific corals have at least 9 betaines rather than only 1 as previously reported. (3) In regards to concentrations of betaines in Pacific corals, GlyB and proline betaine (ProB) typically dominate. Taxa differ in betaine profiles, however, including that Acropora spp. are exceptionally low in total betaines and Porites spp. have (in addition to GlyB and ProB) relatively high concentrations of alanine betaine, hydroxyproline betaine, and taurine betaine. (4) Genus-specific betaine profiles in corals may well be consistent across the Pacific basin. (5) During a year of laboratory acclimatization, coral species studied declined in bulk skeletal density and underwent both increases and decreases in betaine concentrations.
Documentation of how interactions among members of different stream communities [e.g., microbial communities and aquatic insect taxa exhibiting different feeding strategies (FS)] collectively influence the growth, survival, and recruitment of stream fishes is limited. Considerable spatial overlap exists between early life stages of stream fishes, including species of conservation concern like lake sturgeon (Acipenser fulvescens), and aquatic insects and microbial taxa that abundantly occupy substrates on which spawning occurs. Habitat overlap suggests that species interactions across trophic levels may be common, but outcomes of these interactions are poorly understood. We conducted an experiment where lake sturgeon eggs were fertilized and incubated in the presence of individuals from one of four aquatic insect FS taxa including predators, facultative and obligate-scrapers, collector-filterers/facultative predators, and a control (no insects). We quantified and compared the effects of different insect taxa on the taxonomic composition and relative abundance of egg surface bacterial and lower eukaryotic communities, egg size, incubation time to hatch, free embryo body size (total length) at hatch, yolk-sac area, (a measure of resource utilization), and percent survival to hatch. Mean egg size varied significantly among insect treatments. Eggs exposed to predators had a lower mean percent survival to hatch. Eggs exposed to predators had significantly shorter incubation periods. At hatch, free embryos exposed to predators had significantly smaller yolk sacs and total length. Multivariate analyses revealed that egg bacterial and lower eukaryotic surface community composition varied significantly among insect treatments and between time periods (1 vs 4 days post-fertilization). Quantitative PCR documented significant differences in bacterial 16S copy number, and thus abundance on egg surfaces varied across insect treatments. Results indicate that lethal and non-lethal effects associated with interactions between lake sturgeon eggs and free embryos and aquatic insects, particularly predators, contributed to lake sturgeon trait variability that may affect population levels of recruitment.
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