Evolutionary Ecology of Marine Invertebrate Larvae

For more than a century, evolutionary biologists, ecologists, and oceanographers alike have been intellectually stimulated by marine invertebrate larval forms. In 1995, Ecology of Marine Invertebrate Larvae, edited by the late Dr. Larry McEdward, captured the fundamental phenomenon and tremendous diversity of reproductive, biological, and oceanographic aspects of larval ecology. Now, more than twenty years later, this current edited volume provides an update to many of the original 13 chapters, while also reviewing several braches of larval ecology and evolution that have developed since. In Evolutionary Ecology of Marine Invertebrate Larvae, authors review the origins of marine invertebrate larvae and the developmental mechanisms and ecological factors that may generate this great diversity, and how these microscopic organisms feed, develop, and behave in the pelagic environment. Whether actively swimming in the coastal seas or the deep abyss, larvae are often in motion and must settle on the seafloor; however, if delayed, they are susceptible to a multitude of consequences later in life. Now, in an age of change, larvae face a warmer, more acidic, and more toxic ocean than ever before. Responses to these stressors plus many other facets of larval biology can be broadly profiled, thanks to current technological advances. This edited volume provides a major synthesis of an important interdisciplinary field. It aims to foster stimulating discussions centered on the evolution and ecology of marine invertebrate larvae.

The diverse phenotypes exhibited by marine invertebrate larvae are the result of complex gene-environment interactions. Recently, technological advances in molecular biology have enabled large-scale -omics approaches, which can provide a global overview of the molecular mechanisms that shape the larval genotype-phenotype landscape. -omics approaches are facilitating our understanding of larval development and life history evolution, larval response to environmental stress, the larval microbiome, larval physiology and feeding, and larval behavior. These large-scale molecular approaches are even more effective when combined with large-scale environmental monitoring and phenotypic measurements. Current -omics approaches to studying larvae can be improved by the addition of functional genetic analyses and the reporting of natural variation in gene expression between individuals and populations. Systems-level approaches that combine multiple -omics techniques will allow us to explore in fine detail the interactions of environmental and genotypic influences on larval phenotype.


Ocean warming and acidification are major climate change stressors for marine invertebrate larvae, and their impacts differ between habitats and regions. In many regions species with pelagic propagules are on the move, exhibiting poleward trends as temperatures rise and ocean currents change. Larval sensitivity to warming varies among species, influencing their invasive potential. Broadly distributed species with wide developmental thermotolerances appear best able to avail of the new opportunities provided by warming. Ocean acidification is a multi-stressor in itself and the impacts of its covarying stressors differ among taxa. Increased pCO2 is the key stressor impairing calcification in echinoid larvae while decreased mineral saturation is more important for calcification in bivalve larvae. Non-feeding, non-calcifying larvae appear more resilient to warming and acidification. Some species may be able to persist through acclimatization/adaptation to produce resilient offspring. Understanding the capacity for adaptation/acclimatization across generations is important to predicting the future species composition of marine communities.


We provide a conceptual framework for studies of the developmental and evolutionary ecology of marine invertebrate larvae and illustrate how contributions to this volume demonstrate both past achievements and the future fecundity of this research program. Our conceptual framework is anchored in the idea of model life histories, which is a category of investigation similar to but distinct from model organisms or model clades. Marine invertebrate larvae constitute a coherent, structured research program as model life histories that represent developmental, ecological, and evolutionary processes in different ways. They facilitate interdisciplinary investigation that integrates different approaches to diverse research questions about developmental mechanisms, evolutionary history, and adaptation, as well as providing a window on alterations of the marine environment due to anthropogenic climate change. Success in studies of model life histories provides a strong case for sustained professional, institutional, and financial support to carry these endeavors forward.


2020 ◽  
Vol 643 ◽  
pp. 87-97
Author(s):  
K Meyer-Kaiser

Larval dispersal is a critical step in the life-histories of sessile benthic invertebrates. There is a growing body of research showing plasticity in marine invertebrate larvae, but the causes and ranges of intraspecific variation in larvae are not completely understood. In this study, field-based collections of Crepidula fornicata larvae in 2017 motivated a laboratory experiment on carryover effects in 2019. Experimental conditions that approximated environmental conditions experienced by mothers in the field were used to test whether seasonal environmental variations during brooding could lead to differences in larval size and the time to develop to competency. Mothers were kept in 2 different temperature and feeding treatments during brooding, but larvae were cultured in a common garden. Larvae that were brooded at spring temperatures (~13°C) took longer to develop to competency in the common garden and grew larger before becoming competent than larvae brooded at warmer summer temperatures (~21°C). There was no effect of maternal feeding (fed or not fed) on time to develop to competency or larval size. Thus, C. fornicata larvae released earlier in the year are likely to spend longer periods in the water column. They may disperse farther and grow to larger size before settlement. C. fornicata is a model species for larval biology. The results of this study can be used to inform biophysical modelling efforts and refine predictions of connectivity or species range shifts in a changing climate.


2017 ◽  
Author(s):  
Tyler J. Carrier ◽  
Jason Macrander ◽  
Adam M. Reitzel

AbstractThe feeding environment for planktotrophic larvae has a major impact on development and progression towards competency for metamorphosis. High phytoplankton environments that promote growth often have a greater microbial load and incidence of pathogenic microbes, while areas with lower food availability have a lower number of potential pathogens. Trade-offs between metabolic processes associated with growth and immune functionality have been described throughout the animal kingdom and may influence the life-history evolution of marine invertebrate planktotrophic larvae in these environments. Namely, to avoid potential incidences of microbial-mediated mortality and/or dysbiosis, larvae should regulate time spent between these two feeding environments. We describe here transcriptomic and microbiome data that supports this trade-off in larvae, where larvae in a well-fed environment upregulate genes associated with metabolism and may regularly enter a state of dysbiosis, resulting in mortality. To address the hypothesis that the environmental microbiota is a selective force on if, where, and when planktotrophic larvae should feed, we present a strategy for determining the specific interactions of larvae and microbes at a scale representative of their larger pelagic environment.


The functional properties of marine invertebrate larvae represent the sum of the physiological activities of the individual, the interdependence among cells making up the whole, and the correct positioning of cells within the larval body. This chapter examines physiological aspects of nutrient acquisition, digestion, assimilation, and distribution within invertebrate larvae from an organismic and comparative perspective. Growth and development of larvae obviously require the acquisition of “food.” Yet the mechanisms where particulate or dissolved organic materials are converted into biomass and promote development of larvae differ and are variably known among groups. Differences in the physiology of the digestive system (secreted enzymes, gut transit time, and assimilation) within and among feeding larvae suggest the possibility of an underappreciated plasticity of digestive physiology. How the ingestion of seawater by and the existence of a circulatory system within larvae contribute to larval growth and development represent important topics for future research.


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