Occurrence of microbodies in chloromonadophycean algae

Microbody-like organelles occur in the cytoplasm of two chloromonadophycean algae,Vacuolaria virescens Cienkowsky andGonyostomum semen Diesing. Microbodies ofVacuolaria andGonyostomum have a granular matrix which lacks a crystalloid core; they are often present in close association with elements of the endoplasmic reticulum. The occurrence of microbodies in other algae is briefly reviewed.     

Remembering the good and the bad: memory-based mediation of the food–safety trade-off in dynamic landscapes

Predator–prey interactions are central to fitness as animals simultaneously avoid death and consume resources to ensure growth and reproduction. Along with direct effects, predators can also exert strong non-consumptive effects. For example, prey shift habitat use in the presence of predators, a potentially learned behavior. The impact of cognition on movement and predator interactions is largely unexplored despite evidence of learned responses to predation threat. We explore how learning and spatial memory influence predator–prey dynamics by introducing predators into a memory-driven movement modeling framework. To model various aspects of risk, we vary predator behavior: their persistence and spatial correlation with the prey’s resources. Memory outperforms simpler movement processes most in patchy environments with more predictable predators that are more easily avoided once learned. In these cases, memory aids foragers in managing the food–safety trade-off. For example, particular parameterizations of the predation memory reduce encounters while maintaining consumption. We found that non-consumptive effects are highest in landscapes of concentrated, patchy resources. These effects are intensified when predators are highly correlated with the forager’s resources. Smooth landscapes provide more opportunities for foragers to simultaneously consume resources and avoid predators. Predators are able to effectively guard all resources in very patchy landscapes. These non-consumptive effects are also seen with the shift away from the best quality habitat compared to foraging in a predator-free environment.     

Manipulation of the seagrass-associated microbiome reduces disease severity

Host-associated microbes influence host health and function and can be a first line of defence against infections. While research increasingly shows that terrestrial plant microbiomes contribute to bacterial, fungal, and oomycete disease resistance, no comparable experimental work has investigated marine plant microbiomes or more diverse disease agents. We test the hypothesis that the eelgrass (Zostera marina) leaf microbiome increases resistance to seagrass wasting disease. From field eelgrass with paired diseased and asymptomatic tissue, 16S rRNA gene amplicon sequencing revealed that bacterial composition and richness varied markedly between diseased and asymptomatic tissue in one of the two years. This suggests that the influence of disease on eelgrass microbial communities may vary with environmental conditions. We next experimentally reduced the eelgrass microbiome with antibiotics and bleach, then inoculated plants with Labyrinthula zosterae, the causative agent of wasting disease. We detected significantly higher disease severity in eelgrass with a native microbiome than an experimentally reduced microbiome. Our results over multiple experiments do not support a protective role of the eelgrass microbiome against L. zosterae. Further studies of these marine host–microbe–pathogen relationships may continue to show new relationships between plant microbiomes and diseases.     

Identification and characterization of a novel amphioxus dopamine D1-like receptor

Dopamine receptors function to control many aspects of motor control and other forms of behaviour in both vertebrates and invertebrates. They can be divided into two main groups (D₁ and D₂) based on sequence similarity, ligand affinity and effector coupling. However, little is known about the pharmacology and functionality of dopamine receptors in the deuterostomian invertebrates, such as the cephalochordate amphioxus ( Branchiostoma floridae) which has recently been placed as the most basal of all the chordates. A bioinformatic study shows that amphioxus has at least three dopamine D₁-like receptor sequences. One of these receptors, AmphiD₁/β, was found to have high levels of sequence similarity to both vertebrate D₁ receptors and to β-adrenergic receptors. Here, we report on the cloning of AmphiD₁/β from an adult amphioxus cDNA library, and its pharmacological characterization subsequent to its expression in both mammalian cell lines and Xenopus oocytes. It was found that AmphiD₁/β has a similar pharmacology to vertebrate D₁ receptors, including responding to benzodiazepine ligands. The pharmacology of the receptor exhibits 'agonist-specific coupling' depending upon the second messenger pathway to which it is linked. Moreover, no pharmacological characteristics were observed to suggest that AmphiD₁/β may be an amphioxus orthologue of vertebrate β-adrenergic receptors.