Nitrogen isotope variability of macroalgae from a small fishing village, Staithes Harbour, Yorkshire, UK.

Macroalgal nitrogen isotope analysis (δ15N) is a reliable method for the identification of nitrogen pollutant sources. Understanding δ15N geospatial variation within small bays and/or harbour environments can help identify point sources of nitrogen pollution. This study sampled over 300 Fucus vesiculosus and Ulva sp. specimens in September 2022 and May 2023 from Staithes Harbour, North Yorkshire, England. δ15N values for Staithes Beck were elevated when compared to sites in Staithes Harbour and the North Sea: this is attributed to sewage effluent and/or agricultural manure. Few sites within Staithes Harbour were significantly different from one another in terms of δ15N, suggesting a relatively homogenous nitrogen isotope record of the harbour. Simple harbour environments like Staithes may be relatively well mixed, and thus, sampling one harbour site may be enough to represent the entire harbour. Of course, more complex harbours may require more sample locations to ascertain point sources and mixing in the harbour.

Understanding hormonal crosstalk in Arabidopsis root development via emulation and history matching.

A major challenge in plant developmental biology is to understand how plant growth is coordinated by interacting hormones and genes. To meet this challenge, it is important to not only use experimental data, but also formulate a mathematical model. For the mathematical model to best describe the true biological system, it is necessary to understand the parameter space of the model, along with the links between the model, the parameter space and experimental observations. We develop sequential history matching methodology, using Bayesian emulation, to gain substantial insight into biological model parameter spaces. This is achieved by finding sets of acceptable parameters in accordance with successive sets of physical observations. These methods are then applied to a complex hormonal crosstalk model for Arabidopsis root growth. In this application, we demonstrate how an initial set of 22 observed trends reduce the volume of the set of acceptable inputs to a proportion of 6.1 × 10-7 of the original space. Additional sets of biologically relevant experimental data, each of size 5, reduce the size of this space by a further three and two orders of magnitude respectively. Hence, we provide insight into the constraints placed upon the model structure by, and the biological consequences of, measuring subsets of observations.

Nucleus Isthmi Is Required to Sustain Target Pursuit during Visually Guided Prey-Catching.

Animals must frequently perform a sequence of behaviors to achieve a specific goal. However, the neural mechanisms that promote the continuation and completion of such action sequences are not well understood. Here, we characterize the anatomy, physiology, and function of the nucleus isthmi (NI), a cholinergic nucleus thought to modulate tectal-dependent, goal-directed behaviors. We find that the larval zebrafish NI establishes reciprocal connectivity with the optic tectum and identify two distinct types of isthmic projection neuron that either connect ipsilaterally to retinorecipient laminae of the tectum and pretectum or bilaterally to both tectal hemispheres. Laser ablation of NI caused highly specific deficits in tectally mediated loom-avoidance and prey-catching behavior. In the context of hunting, NI ablation did not affect prey detection or hunting initiation but resulted in larvae failing to sustain prey-tracking sequences and aborting their hunting routines. Moreover, calcium imaging revealed elevated neural activity in NI following onset of hunting behavior. We propose a model in which NI provides state-dependent feedback facilitation to the optic tectum and pretectum to potentiate neural activity and increase the probability of consecutive prey-tracking maneuvers during hunting sequences.