Intraspecific comparison of California sea lion (Zalophus californianus) diet assessed using fecal and stable isotope analyses

The diet of juvenile and adult female California sea lions (Zalophus californianus (Lesson, 1828)) at San Miguel Island, California, was estimated and compared using fecal and stable isotope analyses to determine dietary differences by age. Fecal samples were collected during 2002-2006 and prey hard parts were identified. Stable carbon (d13C) and nitrogen (d15N) isotope values were determined from plasma and fur obtained from yearlings, 2- to 3-yr old juveniles, and adult females during 2005 and 2006. Juveniles ate more than 15 prey taxa, whereas adult females consumed more than 33 prey taxa. Relative importance of prey was determined using percent requency of occurrence (%FO). Engraulis mordax (Girard, 1854), Sardinops sagax Jenyns, 1842), Merluccius productus (Ayres, 1855), Sebastes spp. (Cuvier, 1829), and Loligo opalescens (Berry, 1911) were the most frequently occurring (%FO > 10%) prey in the fecal samples of both juvenile and adult female sea lions, although their mportance varied between age groups. Only yearlings had significantly different isotopic values than older conspecifics, indicating that older juveniles were feeding at a similar trophic level, and in similar habitats, as adult females. Whereas each method had biases and uncertainties, combining the two methods provided a better understanding of the diet of California sea lions and intraspecific differences

Variation in δ13C and δ15N values of mothers and their calves across southern right whale nursery grounds: the effects of nutritional stress?

Southern right whales (SRW) are capital breeders that use stored energy reserves to sustain themselves and their calves on nursery areas. With successful calving events declining in some SRW populations, it has been hypothesized that nutritional stress in adult females causes reproductive failure or death of calves shortly after birth. Here we compared offsets in carbon and nitrogen isotope values of mothers and their offspring (∆13 Ccalf-cow and ∆15 Ncalf-cow) among three SRW populations. SRW from Aotearoa New Zealand, with high population growth rates and body conditions scores, have negative ∆13Ccalf-cow suggesting calves are utilizing 13 C-depleted lipid carbon in milk to fuel the synthesis of nonessential amino acids used to build new tissues and rapidly grow. In contrast, a significantly positive ∆13 Ccalf-cow offset previously reported for SRW from Argentina during a mass die-off event was hypothesized to be due to calves consuming milk with low lipid content. Patterns in ∆15 Ncalf-cow were more difficult to interpret and highlight the complexity in nitrogen transfer between mother and offspring. When combined with similar data collected from Brazil and during a low mortality year in Argentina, we hypothesize this approach provides a way to retrospectively compare nutritional condition of breeding adult female SRW across nursery areas

An international standardized magnetic resonance imaging protocol for diagnosis and follow-up of patients with multiple sclerosis

Standardized magnetic resonance imaging (MRI) protocols are important for the diagnosis and monitoring of patients with multiple sclerosis (MS). The Consortium of Multiple Sclerosis Centers (CMSC) convened an international panel of MRI experts to review and update the current guidelines. The objective was to update the standardized MRI protocol and clinical guidelines for diagnosis and follow-up of MS and develop strategies for advocacy, dissemination, and implementation. Conference attendees included neurologists, radiologists, technologists, and imaging scientists with expertise in MS. Representatives from the CMSC, Magnetic Resonance Imaging in MS (MAGNIMS), North American Imaging in Multiple Sclerosis Cooperative, US Department of Veteran Affairs, National Multiple Sclerosis Society, Multiple Sclerosis Association of America, MRI manufacturers, and commercial image analysis companies were present. Before the meeting, CMSC members were surveyed about standardized MRI protocols, gadolinium use, need for diffusion-weighted imaging, and the central vein sign. The panel worked to make the CMSC and MAGNIMS MRI protocols similar so that the updated guidelines could ultimately be accepted by international consensus. Advocacy efforts will promote the importance of standardized MS MRI protocols. Dissemination will include publications, meeting abstracts, educational programming, webinars, “meet the expert” teleconferences, and examination cards. Implementation will require comprehensive and coordinated efforts to make the protocol easy to access and use. The ultimate vision, and goal, is for the guidelines to be universally useful, usable, and used as the standard of care for patients with MS

Constraining the Progenitor System of the Type Ia Supernova 2021aefx

We present high-cadence optical and ultraviolet light curves of the normal Type Ia supernova (SN) 2021aefx, which shows an early bump during the first two days of observation. This bump may be a signature of interaction between the exploding white dwarf and a nondegenerate binary companion, or it may be intrinsic to the white dwarf explosion mechanism. In the case of the former, the short duration of the bump implies a relatively compact main-sequence companion star, although this conclusion is viewing-angle dependent. Our best-fit companion-shocking and double-detonation models both overpredict the UV luminosity during the bump, and existing nickel-shell models do not match the strength and timescale of the bump. We also present nebular spectra of SN 2021aefx, which do not show the hydrogen or helium emission expected from a nondegenerate companion, as well as a radio nondetection that rules out all symbiotic progenitor systems and most accretion disk winds. Our analysis places strong but conflicting constraints on the progenitor of SN 2021aefx; no current model can explain all of our observations. © 2022. The Author(s). Published by the American Astronomical Society.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]