BackgroundRetraction is among the most important basic behaviors of anthozoan Cnidaria polyps and is achieved through the coordinated contraction of at least six different muscle groups. Across the Anthozoa, these muscles range from unrecognizable atrophies to massive hypertrophies, producing a wide diversity of retraction abilities and functional morphologies. The marginal musculature is often the single largest component of the retraction mechanism and is composed of a diversity of muscular, attachment, and structural features. Although the arrangements of these features have defined the higher taxonomy of Zoanthidea for more than 100 years, a decade of inferring phylogenies from nucleotide sequences has demonstrated fundamental misconceptions of their evolution.ResultsHere we expand the diversity of known marginal muscle forms from two to at least ten basic states and reconstruct the evolution of its functional morphology across the most comprehensive molecular phylogeny available. We demonstrate that the evolution of these forms follows a series of transitions that are much more complex than previously hypothesized and converge on similar forms multiple times. Evolution of the marginal musculature and its attachment and support structures are partially scaled according to variation in polyp and muscle size, but also vary through evolutionary allometry.ConclusionsAlthough the retraction mechanisms are diverse and their evolutionary histories complex, their morphologies are largely reflective of the evolutionary relationships among Zoanthidea higher taxa and may offer a key feature for integrative systematics. The convergence on similar forms across multiple linages of Zoanthidea mirrors the evolution of the marginal musculature in another anthozoan order (Actiniaria). The marginal musculature varies through evolutionary allometry of functional morphologies in response to requirements for additional force and resistance, and the specific ecological and symbiotic functions of individual taxa.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-015-0406-1) contains supplementary material, which is available to authorized users.

Understanding the connections between scientific inquiry and digital literacy in informal learning environments is essential to furthering students' critical thinking and technology skills. The Habitat Tracker project combines a standards-based curriculum focused on the nature of science with an integrated system of online and mobile computing technologies designed to help students learn about and participate in scientific inquiry in formal classroom settings and informal learning environments such as science museums or wildlife centers. This research documents the digital literacy skills elementary students used while participating in the Habitat Tracker project, exploring the connections between the scientific inquiry practices they developed and the digital literacy skills they employed as they engaged with the Habitat Tracker curriculum. The results of this research have implications for researchers and practitioners interested in fostering both the scientific inquiry practices and digital literacy skills of elementary students in formal and informal learning environments.

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Computing fields are foundational to most STEM disciplines and the only STEM discipline to show a consistent decline in women's representation since 1990, making it an important field for STEM educators to study. The explanation for the underrepresentation of women and girls in computing is twofold: a sense that they do not fit within the stereotypes associated with computing and a lack of access to computer games and technologies beginning at an early age (Richard, 2016). Informal coding education programs are uniquely situated to counter these hurdles because they can offer additional resources and time for engagement in specially designed activities developed around best practices to improve girls coding identities (National Research Council [NRC], 2009). We draw upon research by Calabrese Barton et al. (2013) and Carlone and Johnson's (2007) research as a lens by which to examine girls' coding identity work in an informal coding education setting—a concept not currently defined in the science education research literature. In this paper, we describe the coding identity trajectories of three middle school girls who participated in a coding camp: Lilly, Victoria, and Beth. Our results provide a conceptual framework that will guide future research on coding identity that better encompasses the role of recognition by educators and peers on youth's coding identity development. This framework can be used to guide broader science education identity research, particularly as it applies to informal STEM education settings that work to engage students, especially girls, across the STEM spectrum.

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