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1. Effects of environmentally relevant concentrations of microplastic fibers on Pacific mole crab ( Emerita analoga ) mortality and reproduction

   https://doi.org/10.1002/lol2.10137  

   Horn, Dorothy A. ; Granek, Elise F. ; Steele, Clare L. ( December 2019 , Limnology and Oceanography Letters)

   Microplastics are ubiquitous in marine systems; however, knowledge of the effects of these particles on marine fauna is limited. Ocean‐borne plastic debris accumulates in littoral ecosystems worldwide, and invertebrate infauna inhabiting these systems can ingest small plastic particles and fibers, mistaking them for food. We examined the effect of microplastic fibers on physiological and reproductive outcomes in a nearshore organism by exposing Pacific mole crabs (Emerita analoga) to environmentally relevant concentrations of microsized polypropylene rope fibers. We compared adult gravid female crab mortality, reproductive success, and embryonic developmental rates between microfiber‐exposed and control crabs. Pacific mole crabs exposed to polypropylene rope had increased adult crab mortality, and decreased retention of egg clutches, causing variability in embryonic development rates. These effects of microplastic ingestion on a nearshore prey species have implications for predators such as surf perf and shore birds, as plastic use, and resultant microplastic presence in nearshore environments increases. Microplastics are ubiquitous in marine and sandy beach environments, posing a significant threat to the marine organisms that reside therein. The most predominant classification of microplastics found have been microfibers. Although a number of biological effects of microplastics have been measured, with documented effects on growth, little research has examined how microplastic fibers affect reproductive output and subsequent development of offspring. We examined the effects of exposure to microfibers on adult mortality, reproductive output, and embryonic development of the filter feeding Pacific mole crab (E. analoga), a dominant infaunal organism on sandy beaches. We demonstrate the effects of microplastic ingestion on mole crab mortality and embryonic development, filling a gap in the current knowledge on the impact of microplastics.

    

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2. Juvenile Albacore tuna ( Thunnus alalunga ) foraging ecology varies with environmental conditions in the California Current Large Marine Ecosystem

   https://doi.org/10.1111/fog.12638  

   Nickels, Catherine F. ; Portner, Elan J. ; Snodgrass, Owyn ; Muhling, Barbara ; Dewar, Heidi ( September 2023 , Fisheries Oceanography)

   Juvenile North Pacific Albacore tuna (Thunnus alalunga) support commercial and recreational fisheries in the California Current Large Marine Ecosystem (CCLME), where they forage during summer and fall. The distributions of the commercial and recreational fisheries and estimates of forage availability have varied substantially over the past century. Time‐series quantifying Albacore diet can help link forage composition to variability in Albacore abundance and distribution and, consequently, their availability to fishers. Previous diet studies in the CCLME are of relatively short duration, and long‐term variability in Albacore diet remains poorly understood. We describe the diets of juvenile Albacore from three regions in the CCLME from 2007 to 2019 and use classification and regression tree analysis to explore environmental drivers of variability. Important prey include Northern Anchovy (Engraulis mordax), rockfishes (Sebastesspp.), Boreal Clubhook Squid (Onychoteuthis borealijaponica), euphausiids (Order: Euphausiidae), and amphipods (Order: Amphipoda), each contributing >5% mean proportional abundance. Most prey items were short lived species or young‐of‐the‐year smaller than 10 cm. Diet variability was related to environmental conditions over the first 6 months of the year (PDO, sea surface temperature, and NPGO) and conditions concurrent with Albacore capture (region and surface nitrate flux). We describe foraging flexibility over regional and annual scales associated with these environmental influences. Continuous, long‐term studies offer the opportunity to identify flexibility in Albacore foraging behavior and begin to make a predictive link between environmental conditions early in the year and Albacore foraging during summer and fall.

    

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3. Tomato locule number and fruit size controlled by natural alleles of lc and fas

   https://doi.org/10.1002/pld3.142  

   Chu, Yi‐Hsuan ; Jang, Jyan‐Chyun ; Huang, Zejun ; van der Knaap, Esther ( July 2019 , Plant Direct)

   Improving yield by increasing the size of produce is an important selection criterion during the domestication of fruit and vegetable crops. Genes controlling meristem organization and organ formation work in concert to regulate the size of reproductive organs. In tomato,lcandfascontrol locule number, which often leads to enlarged fruits compared to the wild progenitors.LCis encoded by the tomato ortholog ofWUSCHEL(WUS), whereasFASis encoded by the tomato ortholog ofCLAVATA3 (CLV3). The critical role of theWUS‐CLV3 feedback loop in meristem organization has been demonstrated in several plant species. We show that mutant alleles for both loci in tomato led to an expansion of theSlWUSexpression domain in young floral buds 2–3 days after initiation. Single and double mutant alleles oflcandfasmaintain higherSlWUSexpression during the development of the carpel primordia in the floral bud. This augmentation and altered spatial expression ofSlWUSprovided a mechanistic basis for the formation of multilocular and large fruits. Our results indicated thatlcandfasare gain‐of‐function and partially loss‐of‐function alleles, respectively, while both mutations positively affect the size of tomato floral meristems. In addition, expression profiling showed thatlcandfasaffected the expression of several genes in biological processes including those involved in meristem/flower development, patterning, microtubule binding activity, and sterol biosynthesis. Several differentially expressed genes co‐expressed withSlWUShave been identified, and they are enriched for functions in meristem regulation. Our results provide new insights into the transcriptional regulation of genes that modulate meristem maintenance and floral organ determinacy in tomato.

    

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4. Effects of predation pressure and prey density on short‐term indirect interactions between two prey species that share a common predator

   https://doi.org/10.1111/een.12855  

   Emery, Sara E. ; Mills, Nicholas J. ( March 2020 , Ecological Entomology)

   1. Generalist predators are important contributors to reliable conservation biological control. Indirect interactions between prey species that share a common generalist predator can influence both community dynamics and the efficacy of biological control.

   2. Laboratory cage experiments investigated the impact of the combined consumptive and non‐consumptive effects of predation by adultHippodamia convergensas a shared predator on the population growth and relative abundance ofAcyrthosiphon pisumandAphis gossypiias prey species. Predation pressure and prey density were varied.

   3. At low predation pressure the indirect interaction between aphid species was asymmetrical with a proportionally greater negative impact of predation onA. gossypiithan onA. pisum. At intermediate predation pressure, the indirect interaction became symmetrical. At high predation pressure and higher levels of prey density, it was asymmetrical with greater negative impact onA. pisum, often driven to local extinction whileA. gossypiipopulations persisted.

   4. A linear mixed‐effects model including early population growth of both aphid species and predation pressure explained 96% and 92% of the variation in the population growth ofA. pisumandA. gossypii, respectively, over an 8‐day period. The overall effect of shared predation on the indirect interaction between the two aphid species is best described as apparent commensalism, whereA. pisumbenefited from early population growth ofA. gossypii, whileA. gossypiiwas unaffected by early population growth ofA. pisum. Considering these indirect interactions is important for conservation biological control efforts to be successful.

    

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5. Killing them softly: Ontogeny of jaw mechanics and stiffness in mollusk‐feeding freshwater stingrays

   https://doi.org/10.1002/jmor.20984  

   Rutledge, Kelsi M. ; Summers, Adam P. ; Kolmann, Matthew A. ( April 2019 , Journal of Morphology)

   Durophagous predators consume hard‐shelled prey such as bivalves, gastropods, and large crustaceans, typically by crushing the mineralized exoskeleton. This is costly from the point of view of the bite forces involved, handling times, and the stresses inflicted on the predator's skeleton. It is not uncommon for durophagous taxa to display an ontogenetic shift from softer to harder prey items, implying that it is relatively difficult for smaller animals to consume shelled prey. Batoid fishes (rays, skates, sawfishes, and guitarfishes) have independently evolved durophagy multiple times, despite the challenges associated with crushing prey harder than their own cartilaginous skeleton.Potamotrygon leopoldiis a durophagous freshwater ray endemic to the Xingu River in Brazil, with a jaw morphology superficially similar to its distant durophagous marine relatives, eagle rays (e.g.,Aetomylaeus, Aetobatus). We used second moment of area as a proxy for the ability to resist bending and analyzed the arrangement of the mineralized skeleton of the jaw ofP. leopoldiover ontogeny using data from computed tomography (CT) scans. The jaws ofP. leopoldido not resist bending nearly as well as other durophagous elasmobranchs, and the jaws are stiffest nearest the joints rather than beneath the dentition. While second moment has similar material distribution over ontogeny, mineralization of the jaws under the teeth increases with age. Neonate rays have low jaw stiffness and poor mineralization, suggesting thatP. leopoldimay not feed on hard‐shelled prey early in life. These differences in the shape, stiffness and mineralization of the jaws ofP. leopoldicompared to its durophagous relatives show there are several solutions to the problem of crushing shelled prey with a compliant skeleton.

    

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