Billie J. Swalla is the Director of Friday Harbor Laboratories in the College of the Environment and also Professor of Biology in the College of Arts and Sciences at the University of Washington. She is an expert in Invertebrate Development and Marine Genomics. She moved to the University of Washington from Penn State University in 1999 in order to work on the diversity of marine invertebrates that inhabit Puget Sound and the Salish Sea. Professor Swalla began her career at the University of Iowa, working on cartilage and muscle differentiation and limb patterning in chicken embryos with Professor Michael Solursh for her M.S. and Ph.D. A summer taking Embryology at the Marine Biological Laboratory in 1983 changed her life and she moved to Postdoctoral studies with Professor William R. Jeffery at the University of Texas at Austin and Bodega Marine Lab at the University of California at Davis. During Postdoctoral research made possible grant from the American Association of University Women, Billie became interested in the role that gender, race and cultures play in science and society. The Swalla lab uses transcriptomics and genomics to investigate the evolution of animal body plans by comparing gene expression between different animal embryos. Specific interests are the Evolution and Development of ctenophores, tunicates and hemichordates. Supervisors: Professor Michael Solursh and Professor William R. Jeffery
This paper examines the differentiation of somites from stage-16 or -17 chick embryos cultured wi... more This paper examines the differentiation of somites from stage-16 or -17 chick embryos cultured with or without notochord in explant cultures. Histological sections of the cultures were stained with a trichrome stain to identify the different kinds of connective tissues formed. Both anterior and posterior (epithelial) somites made muscle, cartilage and loose connective tissue in explant culture. The extent of cartilage differentiation was enhanced by the presence of the notochord, confirming earlier studies. The presence of 1 mM-dibutyryl cAMP in the culture medium increased the amount of muscle found in the explants but by histological criteria did not inhibit chondrogenesis, contrary to earlier reports. The addition of quail ectoderm to the explants stimulated loose connective tissue to form directly beneath it, suggesting for the first time a role of the ectoderm in dermatome differentiation. These results suggest that the epithelial somite has the capacity to differentiate into a...
This paper examines the differentiation of somites from stage-16 or -17 chick embryos cultured wi... more This paper examines the differentiation of somites from stage-16 or -17 chick embryos cultured with or without notochord in explant cultures. Histological sections of the cultures were stained with a trichrome stain to identify the different kinds of connective tissues formed. Both anterior and posterior (epithelial) somites made muscle, cartilage and loose connective tissue in explant culture. The extent of cartilage differentiation was enhanced by the presence of the notochord, confirming earlier studies. The presence of 1 mM-dibutyryl cAMP in the culture medium increased the amount of muscle found in the explants but by histological criteria did not inhibit chondrogenesis, contrary to earlier reports. The addition of quail ectoderm to the explants stimulated loose connective tissue to form directly beneath it, suggesting for the first time a role of the ectoderm in dermatome differentiation. These results suggest that the epithelial somite has the capacity to differentiate into a...
This paper examines the differentiation of somites from stage-16 or -17 chick embryos cultured wi... more This paper examines the differentiation of somites from stage-16 or -17 chick embryos cultured with or without notochord in explant cultures. Histological sections of the cultures were stained with a trichrome stain to identify the different kinds of connective tissues formed. Both anterior and posterior (epithelial) somites made muscle, cartilage and loose connective tissue in explant culture. The extent of cartilage differentiation was enhanced by the presence of the notochord, confirming earlier studies. The presence of 1 mM-dibutyryl cAMP in the culture medium increased the amount of muscle found in the explants but by histological criteria did not inhibit chondrogenesis, contrary to earlier reports. The addition of quail ectoderm to the explants stimulated loose connective tissue to form directly beneath it, suggesting for the first time a role of the ectoderm in dermatome differentiation. These results suggest that the epithelial somite has the capacity to differentiate into a...
In many taxa, germline precursors segregate from somatic lineages during embryonic development an... more In many taxa, germline precursors segregate from somatic lineages during embryonic development and are irreversibly committed to gametogenesis. However, in animals that can propagate asexually, germline precursors can originate in adults. Botryllus schlosseri is a colonial ascidian that grows by asexual reproduction, and on a weekly basis regenerates all somatic and germline tissues. Embryonic development in solitary ascidians is the classic example of determinative specification, and we are interested in both the origins and the persistence of stem cells responsible for asexual development in colonial ascidians. In this study, we characterized vasa as a putative marker of germline precursors. We found that maternally deposited vasa mRNA segregates early in development to a posterior lineage of cells, suggesting that germline formation is determinative in colonial ascidians. In adults, vasa expression was observed in the gonads, as well as in a population of mobile cells scattered throughout the open circulatory system, consistent with previous transplantation/reconstitution results. vasa expression was dynamic during asexual development in both fertile and infertile adults, and was also enriched in a population of stem cells. Germline precursors in juveniles could contribute to gamete formation immediately upon transplantation into fertile adults, thus vasa expression is correlated with the potential for gamete formation, which suggests that it is a marker for embryonically specified, long-lived germline progenitors. Transient vasa knockdown did not have obvious effects on germline or somatic development in adult colonies, although it did result in a profound heterochrony, suggesting that vasa might play a homeostatic role in asexual development.
Summary
Background
The question of how many marine species exist is important because it provide... more Summary Background
The question of how many marine species exist is important because it provides a metric for how much we do and do not know about life in the oceans. We have compiled the first register of the marine species of the world and used this baseline to estimate how many more species, partitioned among all major eukaryotic groups, may be discovered.
Results
There are ∼226,000 eukaryotic marine species described. More species were described in the past decade (∼20,000) than in any previous one. The number of authors describing new species has been increasing at a faster rate than the number of new species described in the past six decades. We report that there are ∼170,000 synonyms, that 58,000–72,000 species are collected but not yet described, and that 482,000–741,000 more species have yet to be sampled. Molecular methods may add tens of thousands of cryptic species. Thus, there may be 0.7–1.0 million marine species. Past rates of description of new species indicate there may be 0.5 ± 0.2 million marine species. On average 37% (median 31%) of species in over 100 recent field studies around the world might be new to science.
Conclusions
Currently, between one-third and two-thirds of marine species may be undescribed, and previous estimates of there being well over one million marine species appear highly unlikely. More species than ever before are being described annually by an increasing number of authors. If the current trend continues, most species will be discovered this century.
Highlights
► ∼226,000 described eukaryotic marine species are accepted and ∼170,000 are not ► Experts and statistics predict that fewer than one million marine species exist ► 70,000 species may already be in specimen collections, waiting to be described ► Most of marine life may be discovered this century
Journal of experimental zoology. Part B, Molecular and developmental evolution, 2013
Understanding the evolutionary history of deuterostomes requires elucidating the phylogenetic int... more Understanding the evolutionary history of deuterostomes requires elucidating the phylogenetic interrelationships amongst the constituent taxa. Although the monophyly and interrelationships among the three principal groups-the chordates, the echinoderms, and the hemichordates-are well established, as are the internal relationships among the echinoderm and chordate taxa, the interrelationships among the principal groups of hemichordates-the harrimaniid enteropneusts, the ptychoderid enteropneusts, and the pterobranchs-remain unresolved. Depending on the study some find enteropneusts paraphyletic with pterobranchs (e.g., Cephalodiscus) more closely related to the harrimaniid enteropneusts (e.g., Saccoglossus) than either are to the ptychoderid enteropneusts (e.g., Ptychodera), whereas other studies support a monophyletic Enteropneusta. To try and resolve between these two competing hypotheses, we turned to microRNAs, small ∼22 nt non-coding RNA genes that have been shown to shed insigh...
Ascidians belong to the tunicates, the sister group of vertebrates and are recognized model organ... more Ascidians belong to the tunicates, the sister group of vertebrates and are recognized model organisms in the field of embryonic development, regeneration and stem cells. ANISEED is the main information system in the field of ascidian developmental biology. This article reports the development of the system since its initial publication in 2010. Over the past five years, we refactored the system from an initial custom schema to an extended version of the Chado schema and redesigned all user and back end interfaces. This new architecture was used to improve and enrich the description of Ciona intestinalis embryonic development, based on an improved genome assembly and gene model set, refined functional gene annotation, and anatomical ontologies, and a new collection of full ORF cDNAs. The genomes of nine ascidian species have been sequenced since the release of the C. intestinalis genome. In ANISEED 2015, all nine new ascidian species can be explored via dedicated genome browsers, and searched by Blast. In addition, ANISEED provides full functional gene annotation, anatomical ontologies and some gene expression data for the six species with highest quality genomes. ANISEED is publicly available at: http://www.aniseed.cnrs.fr.
This paper examines the differentiation of somites from stage-16 or -17 chick embryos cultured wi... more This paper examines the differentiation of somites from stage-16 or -17 chick embryos cultured with or without notochord in explant cultures. Histological sections of the cultures were stained with a trichrome stain to identify the different kinds of connective tissues formed. Both anterior and posterior (epithelial) somites made muscle, cartilage and loose connective tissue in explant culture. The extent of cartilage differentiation was enhanced by the presence of the notochord, confirming earlier studies. The presence of 1 mM-dibutyryl cAMP in the culture medium increased the amount of muscle found in the explants but by histological criteria did not inhibit chondrogenesis, contrary to earlier reports. The addition of quail ectoderm to the explants stimulated loose connective tissue to form directly beneath it, suggesting for the first time a role of the ectoderm in dermatome differentiation. These results suggest that the epithelial somite has the capacity to differentiate into a...
This paper examines the differentiation of somites from stage-16 or -17 chick embryos cultured wi... more This paper examines the differentiation of somites from stage-16 or -17 chick embryos cultured with or without notochord in explant cultures. Histological sections of the cultures were stained with a trichrome stain to identify the different kinds of connective tissues formed. Both anterior and posterior (epithelial) somites made muscle, cartilage and loose connective tissue in explant culture. The extent of cartilage differentiation was enhanced by the presence of the notochord, confirming earlier studies. The presence of 1 mM-dibutyryl cAMP in the culture medium increased the amount of muscle found in the explants but by histological criteria did not inhibit chondrogenesis, contrary to earlier reports. The addition of quail ectoderm to the explants stimulated loose connective tissue to form directly beneath it, suggesting for the first time a role of the ectoderm in dermatome differentiation. These results suggest that the epithelial somite has the capacity to differentiate into a...
This paper examines the differentiation of somites from stage-16 or -17 chick embryos cultured wi... more This paper examines the differentiation of somites from stage-16 or -17 chick embryos cultured with or without notochord in explant cultures. Histological sections of the cultures were stained with a trichrome stain to identify the different kinds of connective tissues formed. Both anterior and posterior (epithelial) somites made muscle, cartilage and loose connective tissue in explant culture. The extent of cartilage differentiation was enhanced by the presence of the notochord, confirming earlier studies. The presence of 1 mM-dibutyryl cAMP in the culture medium increased the amount of muscle found in the explants but by histological criteria did not inhibit chondrogenesis, contrary to earlier reports. The addition of quail ectoderm to the explants stimulated loose connective tissue to form directly beneath it, suggesting for the first time a role of the ectoderm in dermatome differentiation. These results suggest that the epithelial somite has the capacity to differentiate into a...
In many taxa, germline precursors segregate from somatic lineages during embryonic development an... more In many taxa, germline precursors segregate from somatic lineages during embryonic development and are irreversibly committed to gametogenesis. However, in animals that can propagate asexually, germline precursors can originate in adults. Botryllus schlosseri is a colonial ascidian that grows by asexual reproduction, and on a weekly basis regenerates all somatic and germline tissues. Embryonic development in solitary ascidians is the classic example of determinative specification, and we are interested in both the origins and the persistence of stem cells responsible for asexual development in colonial ascidians. In this study, we characterized vasa as a putative marker of germline precursors. We found that maternally deposited vasa mRNA segregates early in development to a posterior lineage of cells, suggesting that germline formation is determinative in colonial ascidians. In adults, vasa expression was observed in the gonads, as well as in a population of mobile cells scattered throughout the open circulatory system, consistent with previous transplantation/reconstitution results. vasa expression was dynamic during asexual development in both fertile and infertile adults, and was also enriched in a population of stem cells. Germline precursors in juveniles could contribute to gamete formation immediately upon transplantation into fertile adults, thus vasa expression is correlated with the potential for gamete formation, which suggests that it is a marker for embryonically specified, long-lived germline progenitors. Transient vasa knockdown did not have obvious effects on germline or somatic development in adult colonies, although it did result in a profound heterochrony, suggesting that vasa might play a homeostatic role in asexual development.
Summary
Background
The question of how many marine species exist is important because it provide... more Summary Background
The question of how many marine species exist is important because it provides a metric for how much we do and do not know about life in the oceans. We have compiled the first register of the marine species of the world and used this baseline to estimate how many more species, partitioned among all major eukaryotic groups, may be discovered.
Results
There are ∼226,000 eukaryotic marine species described. More species were described in the past decade (∼20,000) than in any previous one. The number of authors describing new species has been increasing at a faster rate than the number of new species described in the past six decades. We report that there are ∼170,000 synonyms, that 58,000–72,000 species are collected but not yet described, and that 482,000–741,000 more species have yet to be sampled. Molecular methods may add tens of thousands of cryptic species. Thus, there may be 0.7–1.0 million marine species. Past rates of description of new species indicate there may be 0.5 ± 0.2 million marine species. On average 37% (median 31%) of species in over 100 recent field studies around the world might be new to science.
Conclusions
Currently, between one-third and two-thirds of marine species may be undescribed, and previous estimates of there being well over one million marine species appear highly unlikely. More species than ever before are being described annually by an increasing number of authors. If the current trend continues, most species will be discovered this century.
Highlights
► ∼226,000 described eukaryotic marine species are accepted and ∼170,000 are not ► Experts and statistics predict that fewer than one million marine species exist ► 70,000 species may already be in specimen collections, waiting to be described ► Most of marine life may be discovered this century
Journal of experimental zoology. Part B, Molecular and developmental evolution, 2013
Understanding the evolutionary history of deuterostomes requires elucidating the phylogenetic int... more Understanding the evolutionary history of deuterostomes requires elucidating the phylogenetic interrelationships amongst the constituent taxa. Although the monophyly and interrelationships among the three principal groups-the chordates, the echinoderms, and the hemichordates-are well established, as are the internal relationships among the echinoderm and chordate taxa, the interrelationships among the principal groups of hemichordates-the harrimaniid enteropneusts, the ptychoderid enteropneusts, and the pterobranchs-remain unresolved. Depending on the study some find enteropneusts paraphyletic with pterobranchs (e.g., Cephalodiscus) more closely related to the harrimaniid enteropneusts (e.g., Saccoglossus) than either are to the ptychoderid enteropneusts (e.g., Ptychodera), whereas other studies support a monophyletic Enteropneusta. To try and resolve between these two competing hypotheses, we turned to microRNAs, small ∼22 nt non-coding RNA genes that have been shown to shed insigh...
Ascidians belong to the tunicates, the sister group of vertebrates and are recognized model organ... more Ascidians belong to the tunicates, the sister group of vertebrates and are recognized model organisms in the field of embryonic development, regeneration and stem cells. ANISEED is the main information system in the field of ascidian developmental biology. This article reports the development of the system since its initial publication in 2010. Over the past five years, we refactored the system from an initial custom schema to an extended version of the Chado schema and redesigned all user and back end interfaces. This new architecture was used to improve and enrich the description of Ciona intestinalis embryonic development, based on an improved genome assembly and gene model set, refined functional gene annotation, and anatomical ontologies, and a new collection of full ORF cDNAs. The genomes of nine ascidian species have been sequenced since the release of the C. intestinalis genome. In ANISEED 2015, all nine new ascidian species can be explored via dedicated genome browsers, and searched by Blast. In addition, ANISEED provides full functional gene annotation, anatomical ontologies and some gene expression data for the six species with highest quality genomes. ANISEED is publicly available at: http://www.aniseed.cnrs.fr.
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Papers by Billie Swalla
Background
The question of how many marine species exist is important because it provides a metric for how much we do and do not know about life in the oceans. We have compiled the first register of the marine species of the world and used this baseline to estimate how many more species, partitioned among all major eukaryotic groups, may be discovered.
Results
There are ∼226,000 eukaryotic marine species described. More species were described in the past decade (∼20,000) than in any previous one. The number of authors describing new species has been increasing at a faster rate than the number of new species described in the past six decades. We report that there are ∼170,000 synonyms, that 58,000–72,000 species are collected but not yet described, and that 482,000–741,000 more species have yet to be sampled. Molecular methods may add tens of thousands of cryptic species. Thus, there may be 0.7–1.0 million marine species. Past rates of description of new species indicate there may be 0.5 ± 0.2 million marine species. On average 37% (median 31%) of species in over 100 recent field studies around the world might be new to science.
Conclusions
Currently, between one-third and two-thirds of marine species may be undescribed, and previous estimates of there being well over one million marine species appear highly unlikely. More species than ever before are being described annually by an increasing number of authors. If the current trend continues, most species will be discovered this century.
Highlights
► ∼226,000 described eukaryotic marine species are accepted and ∼170,000 are not ► Experts and statistics predict that fewer than one million marine species exist ► 70,000 species may already be in specimen collections, waiting to be described ► Most of marine life may be discovered this century
Background
The question of how many marine species exist is important because it provides a metric for how much we do and do not know about life in the oceans. We have compiled the first register of the marine species of the world and used this baseline to estimate how many more species, partitioned among all major eukaryotic groups, may be discovered.
Results
There are ∼226,000 eukaryotic marine species described. More species were described in the past decade (∼20,000) than in any previous one. The number of authors describing new species has been increasing at a faster rate than the number of new species described in the past six decades. We report that there are ∼170,000 synonyms, that 58,000–72,000 species are collected but not yet described, and that 482,000–741,000 more species have yet to be sampled. Molecular methods may add tens of thousands of cryptic species. Thus, there may be 0.7–1.0 million marine species. Past rates of description of new species indicate there may be 0.5 ± 0.2 million marine species. On average 37% (median 31%) of species in over 100 recent field studies around the world might be new to science.
Conclusions
Currently, between one-third and two-thirds of marine species may be undescribed, and previous estimates of there being well over one million marine species appear highly unlikely. More species than ever before are being described annually by an increasing number of authors. If the current trend continues, most species will be discovered this century.
Highlights
► ∼226,000 described eukaryotic marine species are accepted and ∼170,000 are not ► Experts and statistics predict that fewer than one million marine species exist ► 70,000 species may already be in specimen collections, waiting to be described ► Most of marine life may be discovered this century