Niche overlap of benthic macrofauna in a tropical estuary: diurnal variation

The complexity of estuaries allows for the establishment of diverse communities composed of species with different survival strategies. The vertical migration of animals in the sediment is linked to competition, escape from predators and adaptations to diurnal physio-chemical changes related to variations in water levels. The present study aimed to evaluate niche overlap and amplitude, as well as the composition and structure, of communities of polychaetes and molluscs between sediment aliquots during the day and at night. Data sampling was performed in the Tubarão River estuary. The highest individual occurrence was registered during the diurnal period. Communities of polychaetes varied significantly between sediment aliquots during the day and at night, while molluscs did not show diurnal variation. Niche overlap results for polychaetes showed higher values between aliquots during the night, while molluscs showed greater overlap during the day. This indicates that polychaetes and molluscs have different mechanisms of coexistence. This may be related to different attributes of species allowing for the division of resources among individuals. Examination of niche overlap provides insights into coexistence of mechanisms within benthic macroinvertebrate communities.

Diel variation of aquatic insect drift in streams of Southern Brazil

Some organisms, such as aquatic insects, are transported from the upstream to downstream region of streams through a process called drift. This process occurs in passive and active ways and can be variable throughout the day, mainly between the nocturnal and diurnal periods. Here, we evaluate the periodicity of the drift of aquatic insects in two streams of the Middle Iguaçu basin, southern region of Brazil. We predicted that the drift of aquatic insects brings the highest richness, diversity and abundance during the nocturnal period, compared to the diurnal period. In addition, we expected that the composition of species is different between these periods. In each stream, aquatic insect sampling was carried out 10 times, for 24 hours, using drift nets. A total of 2,114 aquatic insect specimens were recorded, distributed in 26 families. Of these families, 20 were recorded during the diurnal period and 24 during the nocturnal period. Our results showed an increase in the diversity and abundance of aquatic insect drift in the nocturnal period. However, only abundance was significantly different between the periods. We attribute the higher abundance in nocturnal drift possibly to biological interactions. Thus, nocturnal drift can be a strategy of some aquatic insects to avoid visual predation by other invertebrates and/or vertebrates, in Neotropical streams. We highlight the importance of our study, because it can be used for comparison in surveys of lotic environments that have been impacted by human activity (e.g. by dam construction), which can alter the water flow, and consequently the pattern of insect drift.

Experimental investigation on a novel composite salt-gradient solar pond with East-West side reflector

A salt gradient solar pond acts as an eco-friendly and cost-efficient device for storing thermal energy storage. It is crucial to enrich the efficiency of the salt gradient solar pond to boost its thermal energy storage.This current study investigates the hexagonal composite salinity gradient solar pond (HCSGSP) augmented with a dual inclined reflector and triple-layer transparent cover. A micro solar pond having a hexagonal cross-section was fabricated and experimented at Coimbatore, India having a datum and surface area of 1 m and 0.679 m2 respectively. The novel usage of composite salt (Sodium chloride 30%, Magnesium chloride 10%, and Potassium chloride 60%) led to the enhancement of the daily average ponds' temperature. The pond's upper portion was packed with a triple layer glazed cover which shows an uplift of thermal energy and the pond is provided with inclined reflectors made of plywood fixed with mirrors on the east west direction. The purpose of the mirrors is to increase the solar radiation intensity during the diurnal period and also it acts as an insulator which minimizes the heat losses during the nocturnal period.The maximum thermal efficiencies of the top convective, middle non-convective, and bottom convective layers of reformed solar pond were measured to be 23.44%, 30.68%, and 35.63% respectively whereas they were 1.32%, 12.32%, and 23.44% respectively in case of conventional pond.

No support for relatedness and kin selection to explain high rates of conspecific brood parasitism in colonial Red-breasted Mergansers

Conspecific brood parasitism (CBP) has been observed in approximately half of all species of waterfowl, a philopatric group in which breeding females are frequently locally related. It has been suggested that kin selection can facilitate the evolution of CBP in waterfowl via fitness benefits for the host and parasite. One model demonstrates that discrimination of related and unrelated parasites by the host must be sufficient for kinship to promote CBP, provided that costs of brood parasitism to host fitness are sufficiently low. We parameterized the model using demographic data and behavioural observations from a population of colonial Red-breasted Mergansers (Mergus serrator (Linnaeus, 1758)) in which 47% of nests were parasitized by conspecifics. The costs of 1-3 foreign eggs to host hatching success were generally small (decline of 1.8% per additional egg). Nevertheless, model outputs revealed that brood parasites maximize their inclusive fitness by avoiding nests of relatives, primarily because of constraints on a host’s ability to detect parasites at the nest. Indeed, hosts spent <8% of the diurnal period at the nest during egg laying, a period when parasite activity is greatest. It is thus highly unlikely that relatedness and kin selection promote brood parasitism in this population.

Vegetation Height and Diurnal Period Influenced the Landscape-Use Pattern of Small Ruminants in Woodlands around Summer

Despite the huge potential of using woodlands for small ruminant grazing in the southeast US, unmanaged understory shrubs grown beyond animals’ access minimize the utilization of such vegetation. This study aimed to determine the effect of vegetation height and diurnal period on the behavior and distribution patterns of goats and sheep in woodlands around summer. The study was conducted in six woodland plots (0.4 ha each) comprising southern pines and non-pine (non-target) plant species. Non-pine plants in each study plot were assigned to four treatments: cut to 0 m, 0.9 m, or 1.5 m from the ground level or left uncut (control). Cut plant stubs were allowed to regrow to full canopy before stocking animals. Eight Kiko wethers and five Katahdin rams were rotationally stocked in separate plots, and their diurnal (dawn–dusk) behaviors and distribution patterns were monitored when they were in each plot (three plots per animal species) around the summer of 2018. Animal behavior data were analyzed using the general linear model (GLM) procedure with multivariate analysis of variance (MANOVA) in SAS, while animal distribution pattern and weather data were analyzed in SAS using a GLM procedure and the distribution evenness index (DEI) using the Kruskal–Wallis rank-sum test in R. Level of significance was set at 5%. Both animal species visited the control area the least. Wethers browsed predominantly in areas where non-pine plants were cut to 0.9 m from the ground level, and rams grazed mostly in areas where non-pine plants were cut to the ground level, mostly during the post-midday period. Browsing was the dominant feeding behavior of wethers (39% browsing vs. 4% grazing), while rams’ feeding behavior was dominated with grazing (24% grazing vs. 12% browsing). Lying was a predominant diurnal behavior in both wethers (46%) and rams (35%), mostly during the midday period. Wethers had a higher value for DEI than rams during the morning and post-midday periods. This study established that (1) the utilization of woodland understory foliage by small ruminants can be increased by lowering plant height, and (2) both vegetation characteristics and diurnal period are important factors for influencing small ruminants’ behavior while stocked in woodlands around summer.

Evaluating the effect of four unknown parameters included in a latitudinal energy balance model on the habitability of exoplanets

Among different models for determining the habitable zone (HZ) around a star, a Latitudinal Energy Balance Model (LEBM) is very beneficial due to its parametricity which keeps a good balance between complexity and simulation time. This flexibility makes the LEBM an excellent tool to assess the impact of some key physical parameters on the temperature and the habitability of a planet. Among different physical parameters, some of them, up until now, cannot be determined by any method such as the planet’s spin obliquity, diurnal period, ocean-land ratio, and pressure level. Here we apply this model to study the effect of these unknown parameters on the habitability of three exoplanets located in the inner, outer, and middle of their optimistic HZ. Among the examined parameters, the impact of pressure is more straightforward. It has a nearly direct relation with temperature and also with the habitability in the case of a cold planet. The effect of other parameters is discussed with details. To quantify the impact of all these unknown parameters we utilize a statistical interface which provides us with the conditional probability on habitability status of each planet.

10 Behavior and Landscape-Use Pattern of Small Ruminants Co-grazed in Woodlands with different Vegetation Characteristics

Woodland is the major landcover in Alabama (69%) and other states of the Southeast (≈60%). The understory vegetation present in woodlands can be a great feed resource for small ruminants when woodland grazing is practiced well, for which the understanding of animals’ landscape-use pattern is important. The study objective was to determine the diurnal behavior and landscape-use pattern of Kiko wethers and Katahdin rams co-stocked in woodlands. Eight Kiko wethers (77±2.5 kg. LW) and five Katahdin rams (92±4.6 kg. LW) were co-stocked rotationally in three woodland plots (0.4-ha. each) during May–August 2019 in Atkins Agroforestry Research and Demonstration site, Tuskegee University, Tuskegee, Alabama. Each study plot contained four treatments, where the average canopy height were 0.82 m, 1.34 m, 1.67 m and 1.73 m. The diurnal behavior (grazing, browsing, loafing, lying) and landscape-use pattern of animals were monitored from dawn to dusk when they were in each study plot at each rotation. Diurnal period was categorized into morning (dawn–11:00 am), midday (11:00 am–3:00 pm), and post-midday (3:00 pm–dusk) for the analysis and diurnal behavior and distribution pattern of animals were analyzed in SAS 9.4, GLM procedure with MANOVA option. Animal species differed in their feeding behavior (P &lt; 0.0001), with wethers mostly browsing and rams grazing. Significant interaction effects of animal species and diurnal period occurred on all behavior categories, except loafing and lying (P &lt; 0.0001). Wethers spent less time grazing (84–88%), but more time browsing (90%) during morning and post-midday vs. rams. Animals were actively feeding when the weather was nice and cool, and resting when it was hot. Feeding behavior was dominant during the post-midday period (3 PM–dusk) and lying during midday (11 AM–3 PM). The specific behavior and landscape-use pattern observed in this study can be useful to design and utilize woodland resources more efficiently.

Daily temperature variations at the subsurface combined with water level records in Ajameti, Georgia

High resolution temperatures at the subsurface down to 250 m and water level measurements were carried out in a borehole at Ajameti, Georgia. In both cases daily variations were analyzed for time periods of February/March 2018 and April 2018. Their frequency spectra demonstrate that the diurnal and semi-diurnal variations are generated by earth tides. The enhanced amplitude of the diurnal period at depth of 100 m coincides with the growth phase of vegetation. Frequent rainfall did not affect the temperature at 100 m or deeper but raises the water level. Daily surface temperature variations relate to the temperature variation at the subsurface during the growth phase of vegetation in April and down to 175 m. No relation is detected in records obtained during February/March and at 250 m in both cases. Vertical shift of the water column results from the prevailing temperature gradient and the temperature fluctuation. The estimated water flow yields an amplitude of 0.1 m at 250 m but increases continuously to 0.16 m at 100 m. However, the water level variation reaches only 0.03 m at the surface. It is likely that the free surface of the water level has an additional degree of freedom which causes the lower magnitude of fluctuation.

Feeding Rapidly Alters Microbiome Composition and Gene Transcription in the Clownfish Gut

ABSTRACTDiet is a major determinant of intestinal microbiome composition. While studies have evaluated microbiome responses to diet variation, less is understood about how the act of feeding influences the microbiome, independent of diet type. Here, we use the clownfishPremnas biaculeatus, a species reared commonly in ornamental marine aquaculture, to test how the diversity, predicted gene content, and gene transcription of the microbiome vary over a 2-day diurnal period with a single daily feeding event. This study used fish fed four times daily, once daily, or every 3 days prior to the diurnal period, allowing us also to test how feeding frequency affected microbiome diversity. The amount of time between feedings had no effect on baseline diversity of the microbiome. In contrast, the act of feeding itself caused a significant short-term change in the microbiome, with microbiome diversity, predicted gene content, and gene transcription varying significantly between time points immediately before and 1.5 hours postfeeding. Variation was driven by abundance shifts involving exact sequence variants (ESVs), with one ESV identified asPhotobacteriumsp. increasing from <0.5% of sequences immediately prefeeding to 34% at 1.5 h postfeeding. Other ESVs from a range of microbial groups also increased dramatically after feeding, with the majority also detected in the food. One ESV identified asClostridium perfringensrepresented up to 55% of sequences but did not vary significantly over the diurnal period and was not detected in the food. Postfeeding samples were enriched in transcripts and predicted genes for social interactions, cell motility, and coping with foreign DNA, whereas time points farther from feeding were enriched in genes of diverse catabolic and biosynthetic functions. These results confirm feeding as a significant destabilizing force in clownfish intestinal microbiomes, likely due to both input of cells attached to food and stimulation of resident microbes. Microbes such asPhotobacteriummay episodically transition from environmental reservoirs to growth in the gut, likely in association with food particles. This transition may be facilitated by functions for navigating a new environment and interacting with neighboring microbes and host cells. Other taxa, such asClostridium, are comparatively stable intestinal members and less likely to be affected by passing food. Conclusions about microbiome ecology may therefore differ based on when samples were collected relative to the last feeding.IMPORTANCEDespite extensive study of intestinal microbiome diversity and the role of diet type in structuring gut microbial communities, we know very little about short-term changes in the intestinal microbiome as a result of feeding alone. Sampling microbiomes over a feeding cycle will allow us to differentiate opportunistic, feeding-responsive microbes from resident, potentially commensal members of the gut community. Also, since feeding has the potential to alter microbiome structure, sampling at different points relative to the last feeding event will likely yield different conclusions about microbiome composition and function. This variation should be addressed in comparative microbiome studies. Our study contributes to knowledge of short-term changes in the gut microbiome associated with feeding events.