A New Molecular Phylogeny of Salps (Tunicata: Thalicea: Salpida) and the Evolutionary History of Their Colonial Architecture.

Salps are marine pelagic tunicates with a complex life cycle, including a solitary and colonial stage composed of asexually budded individuals. These colonies develop into species-specific architectures with distinct zooid orientations, including transversal, oblique, linear, helical, and bipinnate chains, as well as whorls and clusters. The evolutionary history of salp colony architecture has remained obscured due to the lack of an ontology to characterize architectures, as well as a lack of phylogenetic taxon sampling and resolution of critical nodes. We (1) collected and sequenced eight species of salps that had never been sequenced before, (2) inferred the phylogenetic relationships among salps, and (3) reconstructed the evolutionary history of salp colony architecture. We collected salp specimens via offshore SCUBA diving, dissected tissue samples, extracted their DNA, amplified their 18S gene, and sequenced them using Sanger technology. We inferred the phylogeny of Salpida based on 18S using both Maximum Likelihood and Bayesian approaches. Using this phylogeny, we reconstructed the ancestral states of colony architecture using a Bayesian ordered Markov model informed by the presence and absence of specific developmental mechanisms that lead to each architecture. We find that the ancestral salp architecture is either oblique or linear, with every other state being derived. Moreover, linear chains have evolved independently at least three times. While transversal chains are developmentally basal and hypothesized to be ancestral, our phylogenetic topology and reconstructions strongly indicate that they are evolutionarily derived through the loss of zooid torsion. These traits are likely critical to multijet locomotory performance and evolving under natural selection. Our work showcases the need to study the broader diversity of salp species to gain a comprehensive understanding of their organismal biology, evolutionary history, and ecological roles in pelagic ecosystems.

Spanish Abstract Las salpas son tunicados pelágicos marinos con un ciclo vital complejo que incluye una fase solitaria y una colonial, compuesta de individuos gemados asexualmente. Al desarrollarse, estas colonias forman arquitecturas diferentes según la especie con orientaciones distintivas de los zooides. Estas arquitecturas incluyen las cadenas transversales, las oblícuas, las lineales, las solenoides, y también las formas de rueda y conglómero. La historia evolutiva de la arquitectura colonial de las salpas ha permanecido en la sombras debido a la falta de un ontología para caracterizar estas arquitecturas, además de por falta de representación taxonómica y resolución de nodos críticos en la filogenia. Hemos (1) muestreado y secuenciado ocho especies de salpa que nunca antes habían sido secuenciadas, (2) hemos inferido las relaciones filogenéticas entre salpas, y (3) reconstruido la historia evolutiva de la arquitectura colonial en salpas. Hemos obtenido especímenes de salpas mediante buceo con escafandra en alta mar, diseccionado muestras de tejido, extraído el ADN, amplificado y secuenciado el gen ribosomal 18S mediante tecnología Sanger. Hemos inferido la filogenia del orden Salpida en base al gen 18S utilizando tanto Máxima Verosimilitud como métodos Bayesianos. Utilizando esta filogenia, hemos reconstruido los estados ancestrales de la arquitectura colonial mediante un modelo Bayesiano Markov ordinal informado por la presencia y ausencia de mecanismos ontogenéticos que derivan en cada arquitectura. Hallamos que la arquitectura ancestral en las salpas fue o bien oblícua o lineal, con todos los demás estados derivados. Además, las cadenas lineales han evolucionado de forma independiente por lo menos tres veces. Las cadenas transversales son el estado basal en el desarrollo y han sido hipotetizadas como el estado ancestral. Sin embargo, nuestra topología filogenética y reconstrucciones indican firmemente que son en realidad derivadas a través de la pérdida del mecanismo de torsion de los zooides. Es probable que estos rasgos morfológicos sean críticos para la eficiencia locomotora de la propulsión multi-chorro y por tanto hayan evolucionado bajo el efecto de la selección natural. Nuestro trabajo demuestra la necesidad de estudiar la amplia diversidad de especies en las salpas para obtener una comprensión integral de su biología organísmica, historia evolutiva, y roles ecológicos en los ecosistemas pelágicos.

Ink Release and Swimming Behavior in the Oceanic Ctenophore Eurhamphaea vexilligera.

Of the more than 150 ctenophore species, the oceanic ctenophore Eurhamphaea vexilligera is notable for its bright orange-yellow ink, secreted from numerous small vesicles that line its substomodeal comb rows. To date, in situ observations by scuba divers have proved the most fruitful method of observing these animals' natural behavior. We present the results of one such contemporary scuba-based observation of E. vexilligera, conducted in the Gulf Stream waters off the coast of Florida, using high-resolution photography and video. Utilizing underwater camera systems purpose built for filming gelatinous zooplankton, we observed E. vexilligera ink release and swimming behavior in situ. From these data, we describe the timeline and mechanics of E. vexilligera ink release in detail, as well as the animal's different swimming behaviors and resulting ink dispersal patterns. We also describe a rolling swimming behavior, accompanied and possibly facilitated by a characteristic change in overall body shape. These observations provide further insight into the behavioral ecology of this distinctive ctenophore and may serve as the foundation for future kinematic studies.

Pulmonary infection during the acute respiratory distress syndrome.

Pulmonary infection is thought to be a common complication of ARDS. We undertook this prospective study to determine the incidence of pulmonary infection in patients with ARDS, and to evaluate the impact of nosocomial pneumonia on severity of ARDS and on survival. Two hundred one bronchoscopies were performed in 105 patients with ARDS with retrieval of distal airway secretions by bronchoalveolar lavage (BAL) and protected specimen brush (PSB). Whenever possible, bronchoscopy was performed at predetermined times: Day 3, Day 7, Day 14, and Day 21 after the onset of ARDS. The majority of patients were receiving antibiotics at the time of study. Changes in bacterial flora over time were determined by quantitative cultures of BAL and PSB. Bacterial growth was common, but usually at small concentrations. Only 16 patients met quantitative culture criteria for pneumonia (PSB > or = 10(3) cfu/ml or BAL > or = 10(4) cfu/ml). Correlation was poor between clinical evidence of pneumonia and pneumonia by quantitative culture criteria: clinical criteria had a very low sensitivity (24%) for predicting positive quantitative culture results, and a low specificity (77%) for predicting negative quantitative culture results. There was no correlation between total colony counts on BAL or PSB and severity of ARDS as judged by Pao2/FIo2 ratios, days receiving ventilation, or compliance. Furthermore, there was no correlation between bacterial growth and survival. We conclude that pneumonia defined by quantitative bacteriology is uncommon in ARDS. The potentially confounding role of broad-spectrum antibiotics should be studied further.