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The mechanics of ventilation in elasmobranchs have been described as a two-pump system which is dependent on the generation of differential pressures between the orobranchial and parabranchial cavities. However, this general model does not take into account sources of variation in parabranchial form and function. For example, the relative pressures that drive flow in each parabranchial chamber during ventilation remain largely unexplored. To address this gap, parabranchial pressures were collected from the Pacific spiny dogfish (Squalus suckleyi, n = 12) during routine ventilation using transducers inserted into parabranchial chambers 2, 3, and 5, numbered anteriorly to posteriorly. Pressure amplitudes collected from the three chambers displayed an attenuation of pressure amplitudes posteriorly, as well as differential, modular use of parabranchial chamber five. These observations have implications for the functioning of the ventilatory pump and indicate distinct ventilatory modes, leading us to propose a new model to describe ventilation in Squalus suckleyi. 

Evolutionary innovations are scattered throughout the tree of life, and have allowed the organisms that possess them to occupy novel adaptive zones. While the impacts of these innovations are well documented, much less is known about how these innovations arise in the first place. Patterns of covariation among traits across macroevolutionary time can offer insights into the generation of innovation. However, to date, there is no consensus on the role that trait covariation plays in this process. The evolution of cranial asymmetry in flatfishes (Pleuronectiformes) from within Carangaria was a rapid evolutionary innovation that preceded the colonization of benthic aquatic habitats by this clade, and resulted in one of the most bizarre body plans observed among extant vertebrates. Here, we use three-dimensional geometric morphometrics and a phylogenetic comparative toolkit to reconstruct the evolution of skull shape in carangarians, and quantify patterns of integration and modularity across the skull. We find that the evolution of asymmetry in flatfishes was a rapid process, resulting in the colonization of novel trait space, that was aided by strong integration that coordinated shape changes across the skull. Our findings suggest that integration plays a major role in the evolution of innovation by synchronizing responses to selective pressures across the organism. 

Abstract Convergent evolution is at the forefront of many form-function studies. There are many examples of multiple independent lineages evolving a similar morphology in response to similar functional demands, providing a framework for testing hypotheses of form-function evolution. However, there are numerous clades with underappreciated convergence, in which there is a perceived homogeneity in morphology. In these groups, it can be difficult to investigate causal relationships of form and function (e.g., diet influencing the evolution of jaw morphology) without the ability to disentangle phylogenetic signal from convergence. Leuciscids (Cypriniformes: Leuciscidae; formerly nested within Cyprinidae) are a species-rich clade of fishes that have diversified to occupy nearly every freshwater trophic niche, yet are considered to have relatively low morphological diversity relative to other large freshwater clades. Within the North American leuciscids, many genera contain at least one herbivore, insectivore, and larvaphage. We created 3D models from micro-computed tomography scans of 165 leuciscid species to measure functionally relevant traits within the pharyngeal jaws of these fishes. Using a published phylogeny, we tested these metrics for evolutionary integration, phylogenetic signal, and correlation with diet. Measurements of the pharyngeal jaws, muscle attachment areas, and teeth showed strong positive evolutionary correlation with each other and negative evolutionary correlation with measurements of the inter-ceratobranchial ligament (ICB ligament). Using diet data from published literature, we found extensive dietary convergence within Leuciscidae. The most common transitions we found were between herbivorous and invertivorous taxa and between insectivore types (aquatic vs. terrestrial). We document a trade-off in which herbivorous leuciscids have large teeth, short ICB ligaments, and large muscle attachment areas, whereas insectivorous leuciscids showed the opposite pattern. Inverse patterns of morphological integration between the ICB ligament the rest of the pharyngeal jaw correspond this dietary trade-off, which indicates that coordinated evolution of morphological traits contributes to functional diversity in this clade. However, these patterns only emerge in the context of phylogeny, meaning that the pharyngeal jaws of North American leuciscids converge by similar means (structural changes in response to dietary demands), but not necessarily to similar ends (absolute phenotype). 

The COVID-19 pandemic shut down undergraduate research programs across the United States. A group of 23 colleges, universities, and research institutes hosted remote undergraduate research programs in the life sciences during Summer 2020. Given the unprecedented offering of remote programs, we carried out a study to describe and evaluate them. Using structured templates, we documented how programs were designed and implemented, including who participated. Through focus groups and surveys, we identified programmatic strengths and shortcomings as well as recommendations for improvements from students’ perspectives. Strengths included the quality of mentorship, opportunities for learning and professional development, and a feeling of connection with a larger community. Weaknesses included limited cohort building, challenges with insufficient structure, and issues with technology. Although all programs had one or more activities related to diversity, equity, inclusion, and justice, these topics were largely absent from student reports even though programs coincided with a peak in national consciousness about racial inequities and structural racism. Our results provide evidence for designing remote Research Experiences for Undergraduates (REUs) that are experienced favorably by students. Our results also indicate that remote REUs are sufficiently positive to further investigate their affordances and constraints, including the potential to scale up offerings, with minimal concern about disenfranchising students.