DFG funded Emmy Noether Projekt

“Black box larval physiology: mechanisms of nutrient acquisition and energetics of invertebrate larvae in a changing ocean

(illustration and copy right by Meike Stumpp)

What is the project about?

Benthic invertebrates such as mussels, corals, and echinoderms are important ecosystem engineers in marine systems with economic and cultural importance for humans. The vast majority of benthic invertebrates reproduces via a planktonic, feeding larval stage that drive the species dispersal and genetic flow between populations. Larval stages can experience long periods in the plankton ranging from a few days to several months accompanied with strong variations in abiotic (temperature, pH, oxygen), and biotic (food/predator abundance) environmental conditions. Sufficient energy acquisition to guarantee fast development and metamorphosis under fluctuating conditions is key for the survival of larval stages. This must have led to the evolution of efficient feeding and digestion strategies that strongly contribute to a larva’s settlement success leading to survival of populations and species. The goal of the project is to identify and characterize the key components of the digestive processes and energetics of these part-time inhabitants of the open ocean. My team and I would like to investigate the molecular and protein-biochemical foundation of digestive processes in the sea urchin larva as model system using enzyme kinetics, transcriptomics, proteomics, and functional genomic approaches. In order to understand the impact of the environment on these processes, the second part aims at performing physiological measurements on live animals and tissues (e.g. metabolic rates and digestive processes) under climate change relevant conditions. In the third project part I would like to verify whether the observed general principles in digestion and energy allocation can be transferred from the sea urchin larva as model system to representatives of other phylogenetic groups such as Polychaeta or Phoronida larvae, making larger predictions on larval biology possible. This project will provide important, new information about larval physiology, and ecology, and will advance our current knowledge regarding the evolution of digestive processes in metazoans. Furthermore, the generated information will contribute to understanding, which physiological processes in marine larvae are challenged by climate change. (link to DFG website)

Figure: Visual abstract of the larval black box project. (A) Life cycle of the sea urchin as example for a benthic invertebrate with an indirect development via a feeding, primary larvae. Feeding and efficient digestion of the pelagic, larval stage determines successful development to the juvenile and thus population recruitment success. (B) Illustration of a sea urchin larva basic morphology (lateral view) with a tripartite digestive tract. The sea urchin larva will be used as model organism for objectives 1 and 2. Food (natural or artificial) is swallowed into the midgut (mg) and digested. Substrates on microbeads develop a fluorescent signal depending on enzyme activity. Objective 1 aims at identifying digestion processes at the molecular and organismic level. Objective 2 will focus on larval and digestive system energetics and quantify the environmental influence on selected digestive processes. Objective 3 aims at comparing key digestive and energetic mechanisms in species along the phylogenetic tree to find common principles in primary larvae (pictures i to v). Photographs i, iii and iv were adopted and modified from Larink & Westheide (2006), photograph ii from Nielsen (2018), and photograph v from Lin et al. (2016). Scale bars 100 µm each. Abbreviations: anus (a), body cavity (bc), forgut (fg), hindgut (hg), midgut (mg), mouth (m), skeleton (s).

References:

Larink, O. & Westheide, W.: Coastal plankton - photo guide for European Seas. (Dr. Friedrich Pfeil Verlag, 2006)

Nielsen, C.: Origin and diversity of marine larvae. in Evolutionary ecology of marine invertebrate larvae (eds. Carrier, T. J., Reitzel, A. M. & Heyland, A.) 1–15 (Oxford University Press, 2018)

Lin, C. Y., Tung, C. H., Yu, J. K. & Su, Y. H.: Reproductive periodicity, spawning induction, and larval metamorphosis of the hemichordate acorn worm Ptychodera flava. J. Exp. Zool. Part B Mol. Dev. Evol.326, 47–60 (2016)