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Biology subjects

Nicosia, A.

Publications and source records attributed to Nicosia, A..

6 recordsLinked to original sources

Sequential predictive e-diagnostics for hidden Markov models of animal movement

Hidden Markov models are standard for inferring behavioural states from animal movement data, but checking whether a fitted latent-state model predicts held-out movement well remains difficult. We develop sequential predictive e-diagnostics that evaluate a fitted movement HMM as a generator of validation trajectories. Each diagnostic specifies a predictable alternative density, and its ratio to the fitted models observable one-step predictive density defines an e-value increment. The denominator is obtained by filtering over latent states, not by conditioning on a decoded path. Under a fixed train/validation protocol, the cumulative product is an e-process, giving anytime-valid thresholds under optional stopping and predictable switching. The construction extends to weighted and state-localized evidence, feature-level circular-linear checks, and blockwise summaries. Controlled simulations show calibration under the fitted-generator null and sensitivity to targeted misspecifications. A leave-one-animal-out elk case study illustrates pooled, individual-specific and state-localized predictive model criticism in a standard movement-HMM workflow.

ecology↗

Behavioural state inference from movement and environmental data using Markovian step selection functions

O_LIMovement paths reflect temporal shifts in behavioural states, typically driven by internal and external drivers. However, the inherently multiphasic nature of these trajectories is frequently overlooked in empirical studies, an oversight that can hinder progress in our understanding of movement ecology. While Hidden Markov Models (HMMs) can successfully identify latent states--such as foraging or travelling--they face significant challenges, particularly in determining the appropriate number of states and in interpreting their ecological relevance in the context of both movement patterns and environmental covariates. C_LIO_LIWe present a framework based on Hidden Markov Models with Step Selection Functions (HMM-SSFs) that identifies behavioural states, represented by ecologically meaningful labels linked to explicit hypotheses about animal movement, that best explain observed movement patterns. The framework imposes interpretable conditions and diagnostic criteria on the post-identified behavioural states to ensure ecological coherence. It is grounded in the evaluation of biologically motivated scenarios rather than purely data-driven partitioning. The framework proceeds in two main steps: first, movement-based states are identified using movement-derived covariates only; second, these states are refined by incorporating environmental predictors, such as habitat structure or species interactions (e.g., predator-prey dynamics). This sequential integration enables the detection of ecological responses that are conditional on behavioural context. C_LIO_LISimulations show that the framework effectively recovers behavioural states across most conditions. State decoding accuracy was notably higher when control locations were drawn from an exponential-family distribution, compared to a uniform one. The exponential-family approach improved state separation and reduced mislabelling, especially when few control locations are generated. However, low state persistence--particularly in Encamped behaviours--resulted in an overestimation of the number of states. These findings underscore the influence of transition probabilities on behavioural labelling. Finally, we applied our framework to zebra (Equus quagga) movement data by combining movement predictors with changes in direction toward the nearest preferred habitat. This enabled us to distinguish between habitat-dependent and habitat-independent travelling behaviours, as well as to identify spatially finer-scale such as encamped state. C_LIO_LIThe proposed framework balances complexity and biological interpretability by using basic movement metrics to identify the behavioural states and their sequence that best explain multiphasic movement paths, together with environmental factors directing movement in each state. Unlike traditional methods that predefine the number of states, the framework estimates both state number and labels, offering a flexible and ecologically meaningful approach for behavioural inference. C_LI

animal behavior and cognition↗

Marine bacterial enrichment in the sea surface microlayer, and surface taxa aerosolization potential in the Western Mediterranean Sea

The sea surface microlayer (SSML) is critical to air-sea exchanges of gases and primary aerosols. However, despite the extent of this boundary layer, little is known about its specific bacterial community (bacterioneuston) and how it may affect ocean-atmosphere exchanges. Here, we studied the bacterial community composition in the surface waters of three different basins of the Western Mediterranean Sea and assessed the selective air-sea transfer of marine bacteria through experimental nascent sea spray aerosol production in a 10 L tank with plunging jets. In situ, the bacterioneuston harbored basin-specific enriched taxa and followed a similar spatial pattern as the underlying bacterioplankton community. Aerosolization potential showed that sea spray taxa might be recruited from both the underlying water and the SSML, and that taxa enriched in the bacterioneuston were not always aerosolized. Our results suggest that the Mediterranean nutrient gradient, as well as pulse events such as dust deposition, affect the distribution of the bacterial community at the ocean-atmosphere interface, which may impact biogeochemical processes, climate regulation and bacterial dispersal through aerosolization.

ecology↗

Microalgae as a novel biofactory for biocompatible and bioactive extracellular vesicles

Nanoalgosomes are extracellular vesicles (EVs) released by microalgal cells that can mediate intercellular and cross-kingdom communication. In the present study, starting from the optimized nanoalgosome manufacturing from cultures of marine microalgae, we evaluated their innate biological properties in preclinical models. Our investigation of nanoalgosome biocompatibility included toxicological analyses, starting from studies on the invertebrate model organism Caenorhabditis elegans, proceeding to hematological and immunological evaluations in mice and immune-compatibility ex vivo. Nanoalgosome biodistribution was evaluated in mice with accurate space-time resolution, and in C. elegans at cellular and subcellular levels. Further examination highlighted the antioxidant and anti-inflammatory bioactivities of nanoalgosomes. This holistic approach to nanoalgosome functional characterization showcases that nanoalgosomes are innate effectors and potential drug delivery system for novel cosmetic formulations and EV-based therapies.

cell biology↗

Improved memory CD8 T cell response to delayed vaccine boost is associated with a distinct molecular signature.

Although the prime/boost interval can impact vaccine responses, the criteria for deciding its time length are poorly defined. To address this, we examined CD8 T cell responsiveness to boost in a BALB/c mouse model of intramuscular (i.m.) vaccination by priming with HIV-1 gag-encoding Chimpanzee adenovector, and boosting with HIV-1 gag-encoding Modified Vaccinia virus Ankara. We found that boost was more effective at day(d)100 than at d30 post-prime, as evaluated at d45 post-boost by multi-lymphoid organ assessment of gag-specific CD8 T cell frequency, CD62L-expression (as a guide to memory status) and in vivo killing. RNA-sequencing of splenic gag-primed CD8 T cells at d100 revealed a quiescent, but highly responsive signature, that trended toward a central memory (CD62L+) phenotype. Interestingly, gag-specific CD8 T cell frequency selectively diminished in the blood at d100, relative to the spleen, lymph nodes and bone marrow. These results move forward the rational design of prime/boost intervals.

immunology↗

A previously missed population of antigen-specific CD8 T cells divides in the blood after vaccination

Although clonal expansion is a hallmark of adaptive immunity, the location(s) where antigen-responding T cells enter cell cycle and complete it have been poorly explored. This lack of knowledge stems partially from the limited experimental approaches available. By using Ki67 plus DNA staining and a novel data analysis technique, we distinguished antigen-specific CD8 T cells in G0, in G1, and in S-G2-M phases after intramuscular vaccination of BALB/c mice with antigen-expressing viral vectors. We discovered an entire population of cycling cells that are usually missed. This \"extra\" population was present early after vaccination in lymph nodes, spleen and, surprisingly, also in the blood, which is not expected to be a site for mitosis of normal non-leukemic cells. These results have implications for previous and future immunological studies in animal models, and potentially in humans. They might also inspire hematologists to seek for other missed populations of dividing cells in blood.

immunology↗