First study of food webs in a large glacial river: the trophic role of invasive trout

El objetivo de este estudio fue determinar la estructura trófica de un gran río de la Patagonia en dos secciones (río arriba y medio) y evaluar la superposición isotópica entre especies nativas e introducidas. Utilizamos análisis de isótopos estables δ15N y δ13C y contenido estomacal. La sección río arriba tuvo una estructura de trama trófica más compleja, con mayor riqueza de macroinvertebrados y peces respecto de la sección media. Los recursos basales dominantes río arriba fueron las algas filamentosas. En esta área, la trucha de lago tuvo la posición trófica más alta entre los peces, aunque, las especies de peces más abundantes fueron las truchas arcoiris. Dependiendo del estadio, la trucha arcoiris cambió su rol de presa a competidor/depredador. En la sección media del río, la base de la trama trófica estuvo dominada por materia orgánica particulada gruesa y la trucha arcoíris adulta fue el depredador tope. Los valores isotópicos variaron entre zonas para invertebrados y peces. Las dos especies nativas e invasoras más abundantes, Puyen y trucha arcoiris, mostraron una separación isotópica en la sección media, pero no en secciones de río arriba. La presencia de peces invasores que ocupan una posición tope en los niveles tróficos puede tener un impacto significativo sobre las poblaciones de peces nativos de gran importancia ecológica en la regiónThe aim of this study was to determine the food webs structure of a large Patagonian river in two river sections (Upstream and Midstream) and to evaluate isotopic overlap between native and introduced species. We used stable isotope analyses of δ15N and δ13C and stomach content. The Upstream section had a more complex food webs structure with a greater richness of macroinvertebrates and fish species than Midstream. Upstream basal resources were dominated by filamentous algae. Lake Trout were found to have a higher trophic position than all other fish species in that area although, the most abundant fish species, were Rainbow Trout. Depending on the life stage, Rainbow Trout shifted from prey to competitor/predator. In the Midstream section, the base of the food webs was dominated by coarse particulate organic matter, and adult Rainbow Trout had the highest trophic level. Isotopic values changed among macroinvertebrates and fish for both areas. The two most abundant native and invasive species — Puyen and Rainbow Trout — showed an isotopic separation in Midstream but did not in Upstream areas. The presence of invasive fish that occupy top trophic levels can have a significant impact on native fish populations that have great ecological importance in the region.Fil: Tagliaferro, Marina Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Kelly, Sean P.. Universidad de Puerto Rico; Puerto RicoFil: Pascual, Miguel Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico para el Estudio de los Ecosistemas Continentales; Argentin

Prey capture by the cosmopolitan hydromedusae, Obelia spp., in the viscous regime

Author Posting. © Association for the Sciences of Limnology and Oceanography, 2016. This article is posted here by permission of Association for the Sciences of Limnology and Oceanography for personal use, not for redistribution. The definitive version was published in Limnology and Oceanography 61 (2016): 2309–2317, doi:10.1002/lno.10390.Obelia spp. are cnidarian hydromedusae with a cosmopolitan distribution but very little is known about their feeding. The small size of Obelia (bell diameter ∼ 1 mm, tentacle width ∼ 0.05 mm) suggests that feeding occurs in a viscous regime characterized by thick boundary layers. During feeding observations with a natural prey assemblage the majority of prey were captured at the tentacle tips during the contraction phase. Swimming kinematics from high speed videography confirmed that swimming was a low Re number process (Re < 50) and showed that maximum tentacle velocities occurred at the tentacle tips midway through a bell contraction. Flow visualizations from particle image velocimetry demonstrated that fluid motion between the tentacles was limited and that velocities were highest at the tentacle tips, leading to a thinning of boundary layer in this region. The highest nematocyst densities were observed in this same region of the tentacle tips. Taken together, the body kinematics, flow visualizations and nematocyst distributions of Obelia explain how these predators are able to shed viscous boundary layers to effectively capture microplanktonic prey. Our findings help explain how other small feeding-current medusae whose feeding interactions are governed by viscosity are able to successfully forage.National Science Foundation Grant Numbers: OCE- 1155084, DBI- 1455471, OCE- 1536672, OCE- 153668

Tales from the crypt: a parasitoid manipulates the behaviour of its parasite host

There are many examples of apparent manipulation of host phenotype by parasites, yet few examples of hypermanipulation—where a phenotype-manipulating parasite is itself manipulated by a parasite. Moreover, few studies confirm manipulation is occurring by quantifying whether the host's changed phenotype increases parasite fitness. Here we describe a novel case of hypermanipulation, in which the crypt gall wasp Bassettia pallida (a phenotypic manipulator of its tree host) is manipulated by the parasitoid crypt-keeper wasp Euderus set, and show that the host's changed behaviour increases parasitoid fitness. Bassettia pallida parasitizes sand live oaks and induces the formation of a ‘crypt’ within developing stems. When parasitized by E. set, B. pallida adults excavate an emergence hole in the crypt wall, plug the hole with their head and die. We show experimentally that this phenomenon benefits E. set, as E. set that need to excavate an emergence hole themselves are about three times more likely to die trapped in the crypt. In addition, we discuss museum and field data to explore the distribution of the crypt-keeping phenomena

Maneuvering performance in the colonial siphonophore, Nanomia bijuga

© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Sutherland, K. R., Gemmell, B. J., Colin, S. P., & Costello, J. H. Maneuvering performance in the colonial siphonophore, Nanomia bijuga. Biomimetics, 4(3), (2019): 62, doi:10.3390/biomimetics4030062.The colonial cnidarian, Nanomia bijuga, is highly proficient at moving in three-dimensional space through forward swimming, reverse swimming and turning. We used high speed videography, particle tracking, and particle image velocimetry (PIV) with frame rates up to 6400 s−1 to study the kinematics and fluid mechanics of N. bijuga during turning and reversing. N. bijuga achieved turns with high maneuverability (mean length–specific turning radius, R/L = 0.15 ± 0.10) and agility (mean angular velocity, ω = 104 ± 41 deg. s−1). The maximum angular velocity of N. bijuga, 215 deg. s−1, exceeded that of many vertebrates with more complex body forms and neurocircuitry. Through the combination of rapid nectophore contraction and velum modulation, N. bijuga generated high speed, narrow jets (maximum = 1063 ± 176 mm s−1; 295 nectophore lengths s−1) and thrust vectoring, which enabled high speed reverse swimming (maximum = 134 ± 28 mm s−1; 37 nectophore lengths s−1) that matched previously reported forward swimming speeds. A 1:1 ratio of forward to reverse swimming speed has not been recorded in other swimming organisms. Taken together, the colonial architecture, simple neurocircuitry, and tightly controlled pulsed jets by N. bijuga allow for a diverse repertoire of movements. Considering the further advantages of scalability and redundancy in colonies, N. bijuga is a model system for informing underwater propulsion and navigation of complex environments.This research was funded by the National Science Foundation (NSF) 1829932 and 173764 to K.R.S., NSF 1830015, 1536672, 1511721 to J.H.C., 1455440, 1536688, 1829913 to S.P.C., NSF 1511996 to B.J.G

Ink release and swimming behavior in the oceanic Ctenophore Eurhamphaea vexilligera

Author Posting. © University of Chicago, 2020. This article is posted here by permission of University of Chicago for personal use, not for redistribution. The definitive version was published in Biological Bulletin 238(3), (2020): 206-213. doi:10.1086/709504.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.This work was funded by National Science Foundation awards OCE-1829945 to BJG, OCE-1829932 to KRS, OCE-1829913 to SPC, and OCE-1830015 to JHC. We thank the captain and crew of Calypso Dive Charters’ Miss Jackie for their assistance and field expertise, as well as two anonymous reviewers, whose insightful comments have improved the quality of the manuscript

The high-cost, type 2 diabetes mellitus patient: an analysis of managed care administrative data

BACKGROUND: Type 2 diabetes mellitus (T2DM) affects 25.8 million individuals in the United States and exerts a substantial economic burden on patients, health care systems, and society. Few studies have categorized costs and resource use at the patient level. The goals of this study were to assess predictors of being a high-cost (HC) patient and compare HC T2DM patients with not high-cost (NHC) T2DM patients. METHODS: Using managed care administrative claims data, patients with two or more T2DM diagnoses between 2005 and 2010 were selected. Patients were followed for 1 year after their first observed T2DM diagnosis; patients not continuously enrolled during this period were excluded from the study. Study measures included annual health care expenditures by component (i.e., inpatient, outpatient, pharmacy, total). Patients accruing total costs in the top 10% of the overall cost distribution (i.e., patients with costs > $20,528) were classified as HC a priori; all other patients were considered NHC. To assess predictors of being HC, a logistic regression model was estimated, accounting for demographics; underlying comorbidity burden (using the Charlson Comorbidity Index [CCI] score); diagnoses of renal impairment, obesity, or hypertension; and receipt of insulin, oral antidiabetics only, or no antidiabetics. RESULTS: A total of 1,720,041 patients met the inclusion criteria; 172,004 were HC. The mean (SD) CCI score for HC patients was 4.3 (3.0) versus 2.1 (1.7) for NHC patients. Mean (SD; upper 95$56,468 ($65,604;$56,778-$56,157) among HC patients and$4,674 ($4,504;$4,695-$4,652) among NHC patients. Inpatient care and pharmacy costs were higher for HC patients than for NHC patients. The strongest predictor of being an HC patient was having a CCI score of 2 or greater (odds ratio [OR] = 4.896), followed by a diagnosis of obesity (OR = 2.106), renal impairment (OR = 2.368), and insulin use (OR = 2.098). CONCLUSIONS: High-cost T2DM patients accrue approximately$52,000 more in total annual health care costs than not high-cost T2DM patients. Patients were significantly more likely to be high-cost if they had comorbid conditions, a diagnosis of obesity, or used insulin

Beyond a warming fingerprint: individualistic biogeographic responses to heterogeneous climate change in California.

Understanding recent biogeographic responses to climate change is fundamental for improving our predictions of likely future responses and guiding conservation planning at both local and global scales. Studies of observed biogeographic responses to 20th century climate change have principally examined effects related to ubiquitous increases in temperature - collectively termed a warming fingerprint. Although the importance of changes in other aspects of climate - particularly precipitation and water availability - is widely acknowledged from a theoretical standpoint and supported by paleontological evidence, we lack a practical understanding of how these changes interact with temperature to drive biogeographic responses. Further complicating matters, differences in life history and ecological attributes may lead species to respond differently to the same changes in climate. Here, we examine whether recent biogeographic patterns across California are consistent with a warming fingerprint. We describe how various components of climate have changed regionally in California during the 20th century and review empirical evidence of biogeographic responses to these changes, particularly elevational range shifts. Many responses to climate change do not appear to be consistent with a warming fingerprint, with downslope shifts in elevation being as common as upslope shifts across a number of taxa and many demographic and community responses being inconsistent with upslope shifts. We identify a number of potential direct and indirect mechanisms for these responses, including the influence of aspects of climate change other than temperature (e.g., the shifting seasonal balance of energy and water availability), differences in each taxon's sensitivity to climate change, trophic interactions, and land-use change. Finally, we highlight the need to move beyond a warming fingerprint in studies of biogeographic responses by considering a more multifaceted view of climate, emphasizing local-scale effects, and including a priori knowledge of relevant natural history for the taxa and regions under study

The role of suction thrust in the metachronal paddles of swimming invertebrates

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Colin, S. P., Costello, J. H., Sutherland, K. R., Gemmell, B. J., Dabiri, J. O., & Du Clos, K. T. The role of suction thrust in the metachronal paddles of swimming invertebrates. Scientific Reports, 10(1), (2020): 17790, doi:10.1038/s41598-020-74745-y.An abundance of swimming animals have converged upon a common swimming strategy using multiple propulsors coordinated as metachronal waves. The shared kinematics suggest that even morphologically and systematically diverse animals use similar fluid dynamic relationships to generate swimming thrust. We quantified the kinematics and hydrodynamics of a diverse group of small swimming animals who use multiple propulsors, e.g. limbs or ctenes, which move with antiplectic metachronal waves to generate thrust. Here we show that even at these relatively small scales the bending movements of limbs and ctenes conform to the patterns observed for much larger swimming animals. We show that, like other swimming animals, the propulsors of these metachronal swimmers rely on generating negative pressure along their surfaces to generate forward thrust (i.e., suction thrust). Relying on negative pressure, as opposed to high pushing pressure, facilitates metachronal waves and enables these swimmers to exploit readily produced hydrodynamic structures. Understanding the role of negative pressure fields in metachronal swimmers may provide clues about the hydrodynamic traits shared by swimming and flying animals.This work was funded by National Science Foundation (NSF OCE 1829913 to SPC), the Alfred P. Sloan Foundation (to BJG) and the Gordon and Betty Moore Foundation (8835 to KRS). The work was also supported by the Roger Williams Foundation to Promote Scholarship and Teaching