Social organization in trematode parasitic flatworms

As in the most complex animal societies, trematodes (parasitic flatworms) live in colonies characterized by a high degree of cooperative organization. My research started with the unexpected observation that several trematode species have a reproductive division of labor with morphologically and behaviorally distinct reproductive and non-reproductive castes. The non-reproductive individuals are smaller but have relatively large mouthparts. They are more active than their reproductive counterparts and disproportionately common in areas of the host where invasions by other trematodes occur. Finally, only non-reproductive individuals readily attack enemies with their mouths. Thus, it is clear that one major role of these individuals is to defend the colony from enemy trematode invaders; they are soldiers. The initial discovery was followed by reports revealing the existence of soldiers in five additional trematode species and by research examining the adaptive significance of soldiers. However, descriptions of colony structure were restricted to a single trematode superfamily (Echinostomatoidea), and knowledge of colony demography and caste function was limited to snapshots of the condition of mature colonies. My doctoral dissertation has laid the foundation to explore the evolution of this remarkable social organization in trematodes, as well as the mechanisms regulating it.Here I quantify morphology, distribution, and behavior of parasites from both establishing and fully developed colonies of sixteen species of trematodes that infect the California horn snail. While showing that eight additional species have a soldier caste, including four species from a new superfamily, I expand the phylogenetic range for which trematode sociality has been examined. I identify patterns underlying colony structure for trematode species that lack a soldier caste and establish discrete criteria to recognize colonies with and without soldiers. Finally, I develop an in vitro system for cultivation of marine trematodes that includes co-culture with Biomphalaria glabrata embryonic (Bge) cell line and media with Bge-released factors. The results presented here highlight the promise of these methods to address questions regarding trematode sociality, interspecific interactions, development and caste differentiation. Trematode colonies are readily replicated, can be maintained in large numbers, and are amenable to in vitro studies. Hence, they provide many advantages as model systems to pursue experimental and comparative research probing general principles underlying the ecology and evolution of sociality. Furthermore, there are more than 20,000 species of trematodes worldwide. They cover a wide range of environmental and life history diversity and are both ecologically and medically important. Thus, understanding the mechanisms that shape trematode communities can have substantial public health, veterinary and wildlife disease applications

OAysters: Acidification effects on susceptibility of Crassostrea gigas larvae to infection by Vibrio tubiashii

In recent years, the oyster Crassostrea gigas has been subject to recurrent outbreaks of vibriosis. The bacteria Vibrio tubiashii induces acute mortality in the veliger larval stage, with severe repercussions for aquaculture and recruitment. The disease is known to be correlated with environmental factors such as temperature and salinity. In our study, we sought to examine the relationship between a rapidly changing environmental factor, ocean acidification, and pathogenicity using a series of larval inoculations at two different carbon dioxide concentration, bacterial strains, larval ages, and bacterial dilutions. Our results of mortality and LD50 indicate that some strains of V. tubiashii may be less pathogenic under acidified conditions and these findings warrant more investigation

Ten strategies for a successful transition to remote learning: Lessons learned with a flipped course.

Transitioning from in-person to remote learning can present challenges for both the instructional team and the students. Here, we use our course "Biodiversity in the Age of Humans" to describe how we adapted tools and strategies designed for a flipped classroom to a remote learning format. Using anonymous survey data collected from students who attended the course either in-person (2019) or remotely (2020), we quantify student expectations and experiences and compare these between years. We summarize our experience and provide ten "tips" or recommendations for a transition to remote learning, which we divide into three categories: (a) precourse instructor preparation; (b) outside of class use of online materials; and (c) during class student engagement. The survey results indicated no negative impact on student learning during the remote course compared to in-person instruction. We found that communicating with students and assessing specific needs, such as access to technology, and being flexible with the structure of the course, simplified the transition to remote instruction. We also found that short, pre-recorded videos that introduce subject materials were among the most valuable elements for student learning. We hope that instructors of undergraduate ecology and evolution courses can use these recommendations to help establish inclusive online learning communities that empower students to acquire conceptual knowledge and develop scientific inquiry and literacy skills

Development of Genomic Resources for a thraustochytrid Pathogen and Investigation of Temperature Influences on Gene Expression

Understanding how environmental changes influence the pathogenicity and virulence of infectious agents is critical for predicting epidemiological patterns of disease. Thraustochytrids, part of the larger taxonomic class Labyrinthulomycetes, contain several highly pathogenic species, including the hard clam pathogen quahog parasite unknown (QPX). QPX has been associated with large-scale mortality events along the northeastern coast of North America. Growth and physiology of QPX is temperature-dependent, and changes in local temperature profiles influence pathogenicity. In this study we characterize the partial genome of QPX and examine the influence of temperature on gene expression. Genes involved in several biological processes are differentially expressed upon temperature change, including those associated with altered growth and metabolism and virulence. The genomic and transcriptomic resources developed in this study provide a foundation for better understanding virulence, pathogenicity and life history of thraustochytrid pathogens.</p

Development of genomic resources for a thraustochytrid pathogen and investigation of temperature influences on gene expression.

Understanding how environmental changes influence the pathogenicity and virulence of infectious agents is critical for predicting epidemiological patterns of disease. Thraustochytrids, part of the larger taxonomic class Labyrinthulomycetes, contain several highly pathogenic species, including the hard clam pathogen quahog parasite unknown (QPX). QPX has been associated with large-scale mortality events along the northeastern coast of North America. Growth and physiology of QPX is temperature-dependent, and changes in local temperature profiles influence pathogenicity. In this study we characterize the partial genome of QPX and examine the influence of temperature on gene expression. Genes involved in several biological processes are differentially expressed upon temperature change, including those associated with altered growth and metabolism and virulence. The genomic and transcriptomic resources developed in this study provide a foundation for better understanding virulence, pathogenicity and life history of thraustochytrid pathogens

Average number of SNPs per kilobase pair in 152 contigs associated with GO Slim biological processes.

<p>Bar heights represent the average SNP rate per kilobase pair for select GO Slim biological processes. Color intensity of the bars indicates number of contigs for each GO Slim term.</p

Relative gene expression levels (RPKM) between QPX10 and QPX21 libraries.

<p>Each circle represents a single contig, with blue circles indicating those contigs that are differentially expressed. The diagonal line represents equal expression between the two libraries.</p

Classification of annotated QPX contigs based on Gene Ontology.

<p>Representation of (a) biological processes, (b) molecular function, and (c) cellular components from Gene Ontology Slim terms based on Swiss-Prot gene annotations. The gene ontology categories ‘other biological processes functions’ (a), ‘other molecular functions’ (b), and ‘other cellular components’ (c) were excluded from these graphs.</p