Evolution of the C4 photosynthetic pathway: events at the cellular and molecular levels

The biochemistry and leaf anatomy of plants using C₄ photosynthesis promote the concentration of atmospheric CO₂ in leaf tissue that leads to improvements in growth and yield of C₄ plants over C₃ species in hot, dry, high light, and/or saline environments. C₄ plants like maize and sugarcane are significant food, fodder, and bioenergy crops. The C₄ photosynthetic pathway is an excellent example of convergent evolution, having evolved in multiple independent lineages of land plants from ancestors employing C₃ photosynthesis. In addition to C₃ and C₄ species, some plant lineages contain closely related C₃–C₄ intermediate species that demonstrate leaf anatomical, biochemical, and physiological characteristics between those of C₃ plants and species using C₄ photosynthesis. These groups of plants have been extremely useful in dissecting the modifications to leaf anatomy and molecular biology, which led to the evolution of C₄ photosynthesis. It is now clear that great variation exists in C₄ leaf anatomy, and diverse molecular mechanisms underlie C₄ biochemistry and physiology. However, all these different paths have led to the same destination—the expression of a C₄ CO₂ concentrating mechanism. Further identification of C₄ leaf anatomical traits and molecular biological components, and understanding how they are controlled and assembled will not only allow for additional insights into evolutionary convergence, but also contribute to sustainable food and bioenergy production strategies.     

Focus: Preventive Medicine: 2020 Evaluation of Portable Vision Screening Instruments

Amblyopia is the most common cause of preventable visual impairment in children and occurs as a result of unilateral or bilateral impairment in best-corrected visual acuity. Early diagnosis and proper treatment are crucial to prevent poor visual outcomes in adulthood. Advances in technology have provided more objective diagnostic tools, which can now be used by a wide range of healthcare providers. Here, we highlight tools that have gained popularity in the past two decades and compare clinically relevant parameters to guide primary care providers seeking to incorporate instrumental vision screening in pediatric patient care.     

Stejneger's beaked whale strandings in Alaska, 1995–2020

Presented here is the first comprehensive and updated compilation of history, distribution, and findings of Stejneger's beaked whales (Mesoplodon stejnegeri) in Alaska. Stejneger's beaked whales are a poorly understood, elusive, deep-diving cetacean species found in the North Pacific Ocean. Since Stejneger's beaked whale strandings data in Alaska through 1994 were last published, 35 additional strandings have been documented. Twenty-seven animals stranded in the Aleutian Islands, seven stranded in Southcentral Alaska, and one animal stranded on St. Lawrence Island. Twenty-two carcasses were necropsied, but only four were fresh. Seventeen of the 22 died during mass stranding events and cause of death could not be definitively determined. Barotrauma was suspected in three cases and infectious disease possibly complicated by barotrauma occurred in two cases. We documented an expansion of strandings into the northern Bering Sea, characterized a sex bias, examined stomach contents that included macroplastic, and identified parasites not previously associated with Stejneger's beaked whales. Also included are data on the largest known mass stranding of Stejneger's beaked whales, which occurred on Adak Island in 2018. The history, distribution, and findings presented here are central to further our understanding of this species.     

Genetic evidence for seasonal consumption of monkfish (Lophius spp.) and salmonids (Salmo spp.) by gray seals

Recoveries of gray seal (Halichoerus grypus) populations across their eastern Atlantic distribution have led to a steady increase in seal-fishery interactions. Fishers have estimated depredation of salmonids (Salmo spp.) and monkfish (Lophius spp.) as high as 40% and 59% respectively in Ireland. However, empirical evidence for the consumption of these species has been extremely limited due to diagnostic hard part remains not being found in scats or stomach samples. We applied species-specific primers and tested for the presence of monkfish and salmonids in gray seal diet genetically using quantitative polymerase chain reaction (qPCR) on scats. Monkfish occurred in 29.7% of sampled scats, while salmonids occurred in 12.7%. Seasonal and regional variability in occurrence were noted for both species, likely related to the migratory behavior of the prey species and proximity of seal haul-outs to aquaculture sites. Traditional hard part analysis of scats, including scats that tested positive for monkfish and salmonid DNA, failed to find any evidence of either species. This study provides important empirical evidence for the consumption of these species in Ireland that can inform management.