Bioirrigation in Marine Sediments

Bioirrigation refers to the enhanced transport of solutes across the sediment-water interface induced by the activities of bottom-dwelling organisms. This chapter provides an overview of what bioirrigation is, how it is induced, and how it affects processes in marine sediments. After discussing some well documented effects of bioirrigation such as the enhanced cycling of organic matter, nutrients, metals and pollutants, this article also touches upon phenomena that were uncovered more recently and deserve further attention, including rapid redox oscillations, bioadvection, and biohydraulic sediment cracking. Last but not least, some of the key methods used to study bioirrigation are presented, with special emphasis on imaging techniques that allow measurements with high spatial and temporal resolution. The chapter includes a number of graphics and videos that illustrate the highly dynamic and heterogeneous nature of bioirrigated sediments

Bioirrigation in Marine Sediments

Bioirrigation refers to the enhanced transport of solutes across the sediment-water interface induced by the activities of bottom-dwelling organisms. This chapter provides an overview of what bioirrigation is, how it is induced, and how it affects processes in marine sediments. After discussing some well documented effects of bioirrigation such as the enhanced cycling of organic matter, nutrients, metals and pollutants, this article also touches upon phenomena that were uncovered more recently and deserve further attention, including rapid redox oscillations, bioadvection, and biohydraulic sediment cracking. Last but not least, some of the key methods used to study bioirrigation are presented, with special emphasis on imaging techniques that allow measurements with high spatial and temporal resolution. The chapter includes a number of graphics and videos that illustrate the highly dynamic and heterogeneous nature of bioirrigated sediments

Postsynaptic expression of an epidermal growth factor receptor regulates cholinergic synapse formation between identified molluscan neurons

Epidermal growth factor (EGF) family members are conserved in both vertebrates and invertebrates. Recent studies suggest that EGF ligands in invertebrates may have neurotrophic actions that possibly compensate for the apparent absence of neurotrophins in these species. In this study, we have cloned an EGF receptor from the mollusk Lymnaea stagnalis (L-EGFR), and shown that L-EGFR is the receptor for a previously identified EGF-like peptide in Lymnaea, named Lymnaea EGF (L-EGF). Knock-down of L-EGFR expression prevented L-EGF-induced excitatory synapse formation between identified cholinergic neuron visceral dorsal 4 (VD4) and its postsynaptic partner left pedal dorsal 1 (LPeD1). Moreover, knock-down of L-EGFR also prevented synapse formation induced by Lymnaea brain conditioned medium, suggesting that L-EGF is the most important, if not the only, brain-derived factor that promotes excitatory cholinergic synapse formation in Lymnaea. Thus, our data establish canonical EGF/EGFR signaling as an important synaptotrophic mechanism in invertebrates. © The Authors (2008)