Photophysiological cycles in Arctic krill are entrained by weak midday twilight during the Polar Night

Modeling climate change effects on some biochemical parameters in horse

Changes in the global climate pose a severe threat to human and animal welfare and productivity. Total proteins (TP), globulins (GLOB), albumins (ALB), alkaline phosphatase (ALP), creatine kinase (CK), lactate dehydrogenase (LDH), aspartate aminotransferase (AST), blood urea nitrogen (BUN), γ-glutamyl transferase (GGT), and creatinine (CREA) were evaluated during a three-year monitoring period (2021-23) on 16 Thoroughbred retired mares from the regional Golkoy Breeding Farm in Kastamonu- Turkey. The following thermal and hygrometric parameters were gathered: ambient temperature (AT), relative humidity (RH) and ventilation (VT), and the Temperature-Humidity Index (THI) was then calculated. Blood samples were collected on the first of each month from January 2021 to December 2023 and the obtained serum was used for the analysis, variations in environmental parameters were correlated to changes in biochemical profile. Two-way for repeated measure ANOVA showed a significant effect of month for AT (<0.0001), RH (<0.0001), and THI (<0.0001), and on TP (p < 0.001), GLOB (p < 0.001), ALB (p < 0.0001), ALP (p < 0.01), CK (p < 0.01), LDH (p < 0.001), AST (p < 0.0001), BUN (p < 0.0001), GGT (p < 0.0001), and CREA (p < 0.0001). ALP, CK, LDH, AST, and BUN values increased during the hottest periods, while GGT showed decreasing values during the summer. CREA showed positive correlation with AT, and LDH and CREA exhibited negative correlation with RH. These results may be useful for the monitoring of horses' physiological conditions as a result of climate change.

Vision guides the twilight search for oviposition sites of the Asian tiger mosquito, Aedes albopictus

BACKGROUND

Oviposition site selection is an important component of vector mosquito reproductive biology. The Asian Tiger mosquito, Aedes albopictus, is a major and important vector of arboviruses including Dengue. Previous studies documented the preference of gravid females for small, dark-colored water containers as oviposition sites, which they sought during the twilight period (dusk) of their locomotor activity. Vision plays an important role in this behavior, and factors such as the shape, size, and color of the container, light intensity, polarization, spectrum, and other visual cues guide the search for suitable oviposition sites, but the mechanistic factors driving this behavior are unclear.

METHODOLOGY/PRINCIPAL FINDINGS

We blindfolded adult female compound eyes and observed the effects of a lack of vision on the ability to discriminate and utilize preferred oviposition sites. Furthermore, the transcriptomes of blindfolded mosquitoes were screened to identify genes with vision-sensitive expression profiles and gene-editing was used to create non-functional mutations in two of them, rhodopsin-like (mutation designated 'rho-l△807') and kynurenine hydroxylase (mutation designated 'khw'). Behavioral tests of both mutant and control strains revealed that the rho-l△807 mutant mosquitoes had a significant decrease in their ability to search for preferred oviposition sites that correlated with a reduced ability to recognize long-wavelength red light. The khw mutant mosquitoes also had a reduced ability to identify preferred oviposition sites that correlated with reductions in their ability to respond to variations in daily brightness and their ability to discriminate among different color options of the containers and background monochromatic light.

CONCLUSIONS/SIGNIFICANCE

This study underscores the importance of visual cues in the oviposition site selection behavior of adult female Ae. albopictus. We demonstrate that wild-type rho-l and kh gene products play a crucial role in this behavior, as mutants exhibit altered sensitivity or recognition of light intensity and substrate colors.

Ecological genomics in the Northern krill uncovers loci for local adaptation across ocean basins

Krill are vital as food for many marine animals but also impacted by global warming. To learn how they and other zooplankton may adapt to a warmer world we studied local adaptation in the widespread Northern krill (Meganyctiphanes norvegica). We assemble and characterize its large genome and compare genome-scale variation among 74 specimens from the colder Atlantic Ocean and warmer Mediterranean Sea. The 19 Gb genome likely evolved through proliferation of retrotransposons, now targeted for inactivation by extensive DNA methylation, and contains many duplicated genes associated with molting and vision. Analysis of 760 million SNPs indicates extensive homogenizing gene-flow among populations. Nevertheless, we detect signatures of adaptive divergence across hundreds of genes, implicated in photoreception, circadian regulation, reproduction and thermal tolerance, indicating polygenic adaptation to light and temperature. The top gene candidate for ecological adaptation was nrf-6, a lipid transporter with a Mediterranean variant that may contribute to early spring reproduction. Such variation could become increasingly important for fitness in Atlantic stocks. Our study underscores the widespread but uneven distribution of adaptive variation, necessitating characterization of genetic variation among natural zooplankton populations to understand their adaptive potential, predict risks and support ocean conservation in the face of climate change.

Development and calibration of a high dynamic range and autonomous ocean-light instrument to measure sub-surface profiles in ice-covered waters

The optical chain and logger (OptiCAL) is an autonomous ice-tethered observatory equipped with multiple light sensors for mapping the variation of light with depth. We describe the instrument and present an ensemble calibration for downwelling irradiance E P A R in [µm o l m -2 s -1]. Results from a long-term deployment in the Arctic Ocean demonstrate that the OptiCAL can cover the high dynamic range of under-ice light levels from July to November and produce realistic values in terms of magnitude when compared to modeled surface irradiance. Transient features of raised light levels at specific depths associated with nearby leads in the ice underline the importance of depth-resolved light measurements.

Spectral and RGB analysis of the light climate and its ecological impacts using an all-sky camera system in the Arctic

The ArcLight observatory provides an hourly continuous time series of all-sky images providing light climate data (intensity, spectral composition, and photoperiod) from the Arctic (Svalbard at 79°N). Until recently, no complete annual time series of light climate relevant for biological processes has been provided from the high Arctic because of insufficient sensitivity of commercial light sensors during the Polar Night. The ArcLight set up is unique, as it provides both all-sky images and the corresponding integrated spectral irradiance in the visible part of the solar electromagnetic spectrum (E P A R ). Here we present a further development providing hourly diel-annual dynamics from 2020 of the irradiance partitioned into the red, green, and blue parts of the solar spectrum and illustrate their relation to weather conditions, and sun and moon trajectories. We show that there is variation between the RGB proportions of irradiance throughout the year, with the blue part of the spectrum showing the greatest variation, which is dependent on weather conditions (i.e., cloud cover). We further provide an example of the biological impact of these spectral variations in the light climate using in vivo Chl a-specific absorption coefficients of diatoms (mean of six low light acclimated northern-Arctic bloom-forming species) to model total algal light absorption (AQ t o t a l ) and the corresponding fraction of quanta used by Photosystem II (AQPSII) (O 2 production) in RGB bands and the potential impacts on the photoreceptor response, suggesting periods where repair and maintenance functions dominate activity in the absence of appreciable levels of red or green light. The method used here can be applied to light climate data and spectral response data worldwide to give localized ecological models of AQ.

Evidence of separate influence of moon and sun on light synchronization of mussel's daily rhythm during the polar night

Marine organisms living at high latitudes are faced with a light climate that undergoes drastic annual changes, especially during the polar night (PN) when the sun remains below the horizon for months. This raises the question of a possible synchronization and entrainment of biological rhythms under the governance of light at very low intensities. We analyzed the rhythms of the mussel Mytilus sp. during PN. We show that (1) mussels expressed a rhythmic behavior during PN; (2) a monthly moonlight rhythm was expressed; (3) a daily rhythm was expressed and influenced by both sunlight and moonlight; and (4) depending on the different times of PN and moon cycle characteristics, we were able to discriminate whether the moon or the sun synchronize the daily rhythm. Our findings fuel the idea that the capability of moonlight to synchronize daily rhythms when sunlight is not sufficient would be a crucial advantage during PN.

Rhythms and Clocks in Marine Organisms

The regular movements of waves and tides are obvious representations of the oceans' rhythmicity. But the rhythms of marine life span across ecological niches and timescales, including short (in the range of hours) and long (in the range of days and months) periods. These rhythms regulate the physiology and behavior of individuals, as well as their interactions with each other and with the environment. This review highlights examples of rhythmicity in marine animals and algae that represent important groups of marine life across different habitats. The examples cover ecologically highly relevant species and a growing number of laboratory model systems that are used to disentangle key mechanistic principles. The review introduces fundamental concepts of chronobiology, such as the distinction between rhythmic and endogenous oscillator-driven processes. It also addresses the relevance of studying diverse rhythms and oscillators, as well as their interconnection, for making better predictions of how species will respond to environmental perturbations, including climate change. As the review aims to address scientists from the diverse fields of marine biology, ecology, and molecular chronobiology, all of which have their own scientific terms, we provide definitions of key terms throughout the article.

Animal behavior is central in shaping the realized diel light niche

Animal behavior in space and time is structured by the perceived day/night cycle. However, this is modified by the animals’ own movement within its habitat, creating a realized diel light niche (RDLN). To understand the RDLN, we investigated the light as experienced by zooplankton undergoing synchronized diel vertical migration (DVM) in an Arctic fjord around the spring equinox. We reveal a highly dampened light cycle with diel changes being about two orders of magnitude smaller compared to the surface or a static depth. The RDLN is further characterized by unique wavelength-specific irradiance cycles. We discuss the relevance of RDLNs for animal adaptations and interactions, as well as implications for circadian clock entrainment in the wild and laboratory.