title: PeerJ description: Articles published in PeerJ link: https://peerj.com/articles/index.rss3?journal=peerj&page=143 creator: info@peerj.com PeerJ errorsTo: info@peerj.com PeerJ language: en title: Three new species of the family Idyanthidae (Copepoda, Harpacticoida) from sublittoral zones around the Korean Peninsula link: https://peerj.com/articles/18767 last-modified: 2025-01-16 description: There are few taxonomic studies of the harpacticoid family Idyanthidae Lang, 1944 in the Pacific Ocean. As a first report of the family in this region, one species of the monotypic genus Idyellopsis Lang, 1948 and two species of the genus Idyella Sars, 1905 are described from sublittoral habitats around the Korean Peninsula. Idyellopsis orientalis sp. nov. is distinguished from the type and only species of the genus, Idyellopsis typica Lang, 1948, in the length:width ratio of the body and genital double-somite, length of caudal seta I, and structure of the female P5 baseoendopod. Idyella dolichi sp. nov. and Idyella exochos sp. nov. share the armature of the female P5 exopod with four setae with Idyella exigua Sars, 1905, Idyella major Sars, 1920, and Idyella pallidula Sars, 1905. However, the two new species differ from the three European species in the armature of the terminal segment of the P1 endopod and female P5 baseoendopod, and in the shape of the genital double-somite. The male of Idyella dolichi sp. nov. also has two distinct features: the distal two segments of the P2 endopod are completely fused, and the third segment of the antennule has a prominent outer projection. The geographical distribution of Idyellopsis and Idyella is extended by the discovery of three new species in Korean waters. We also discuss a possible phylogenetic relationship among members of family Idyanthidae at genus level. creator: Jong Guk Kim creator: Kyuhee Cho creator: Jimin Lee uri: https://doi.org/10.7717/peerj.18767 license: https://creativecommons.org/licenses/by-nc/4.0 rights: © 2025 Kim et al. title: Nitrogen fertilizer application for improving the biomass, quality, and nitrogen fixation of alfalfa (Medicago sativa L.) at different growth stages in a saline‒alkali soil link: https://peerj.com/articles/18796 last-modified: 2025-01-16 description: BackgroundThe application of nitrogen (N) fertilizer to alfalfa (Medicago sativa L.) has received little attention due to the ability of this plant to fix N. However, N deficiency stress is often observed in marginal lands of China, especially in saline–alkali soils. Thus, this study aimed to assess the response of alfalfa yield, quality, N fixation, and soil N concentration to N fertilizer application at different stages in saline–alkali soil of Inner Mongolia. A 2-year (2020 and 2021) field experiment with five N fertilizer application rates, namely, 0 (N0), 20 (N20), 60 (N60), 120 (N120) and 180 (N180) kg N ha−1, was conducted in Inner Mongolia.ResultsThe results showed that N fertilizer application of 180 kg ha−1 significantly increased the total alfalfa yield by 29%–32% by improving the stem‒leaf ratio; however, it didn’t lead to a further increase in alfalfa quality. N fertilizer applications of 60 and 120 kg ha−1 significantly improved the crude protein by 10.6%–22.7% and reduced the acid or neutral detergent fiber by 10.0%–18.7% in vegetative and bud stages, respectively, by improving the leaf N concentration. Furthermore, the fraction of N derived from the atmosphere reached 68.6%, with a significant increase in the corresponding amount of N fixed in N60. Soil NO3−-N concentrations significantly increased by 24.1%–33.3%, and NH4+-N concentrations increased by 1 to 3 times when N fertilizer application exceeded 120 kg N ha−1 compared with that in N0.ConclusionsOverall, this study revealed the essential role of N fertilizer application at low rates in alfalfa production, as this practice not only increases alfalfa yield but also improves N fixation in saline‒alkali soil. However, it did not result in further improvement in alfalfa quality at the early flowering stage. The findings provides valuable guidance for N fertilizer application in alfalfa production on saline‒alkali soils. creator: Weifan Wan creator: Qian Liu creator: Ke Li creator: Kun Zhao creator: Fei Qi creator: Yuanshuo Li creator: Zhi Sun creator: Haigang Li uri: https://doi.org/10.7717/peerj.18796 license: https://creativecommons.org/licenses/by/4.0/ rights: © 2025 Wan et al. title: Association between phase angle, body mass index and insulin resistance in patients with type 2 diabetes mellitus: a cross-sectional study link: https://peerj.com/articles/18815 last-modified: 2025-01-16 description: Background: The purpose of this analysis was to investigate the associations between phase angle (PhA), body mass index (BMI) and insulin resistance (IR) in patients with type 2 diabetes mellitus (T2DM).Methods: The retrospective cross-sectional study included 200 T2DM patients treated during 2018 to 2019 in Zhongda Hospital Southeast University. PhA and other body composition indicators were measured by bioelectrical impedance analysis (BIA). Subjects were classified into four groups based on body composition: low phase angle and low body mass index (LPLB), low phase angle and high body mass index (LPHB), high phase angle and low body mass index (HPLB) and high phase angle and high body mass index (HPHB).Results: Overall, in the unadjusted model and minor, all adjusted models (unadjusted model, models 1–4), homeostasis model assessment of insulin resistance (HOMA-IR) was higher in the LPHB group than in the LPLB group (P = 0.034). In the unadjusted model, Model 1 (adjustment for age), Model 2 (adjust for age+duration), Model 3 (adjust for age+duration+sex+UA+TG+TC) and Model 4 (adjust for age+duration+sex+UA+TG+TC+HDL+HbA1c), the adjusted ORs for participants were 4.4 (95% CI [1.72–11.24]), 4.41 (95% CI [1.73–11.27]), 4.75 (95% CI [1.83–12.32]), 2.93 (95% CI [1.04–8.23]) and 3.1 (95% CI [1.09–8.86]) respectively, compared to LPHB group.Conclusions: T2DM patients with the body composition of low phase angle and high body mass index exhibited the most severe degree and the highest risk of insulin resistance. creator: Yezi Hu creator: Hui Jin uri: https://doi.org/10.7717/peerj.18815 license: https://creativecommons.org/licenses/by/4.0/ rights: © 2025 Hu and Jin title: Optimization and action mechanism of pollutant removal performance of unsaturated vertical flow constructed wetland (UVFCW) driven by substained-release carbon source link: https://peerj.com/articles/18819 last-modified: 2025-01-16 description: Constructed wetland (CW) technology has attracted much attention due to its economical and environmentally friendly features. The low dissolved oxygen (DO) and low carbon/nitrogen (C/N) ratio in the wetland influent water affect the treatment performance of CW, resulting in a decrease in the removal efficiency of ammonia nitrogen (NH4+-N) and nitrate nitrogen (NO3−-N). In order to address this problem, this study optimized the pollutants removal performance of unsaturated vertical flow constructed wetland (UVFCW) by adding sustained-release carbon sources (corn cobs + polybutylene adipate terephthalate (PBAT)). The results showed that the sustained-release of carbon source increased the carbon source in UVFCW, thus increasing the abundance and activity of denitrifying microorganisms and enhancing the denitrification reaction, ultimately improving the removal of NO3−-N, with its removal efficiency reaching up to 95.50%. The placement method of sustained-release carbon source mainly affected the distribution of carbon source and DO in water body, thus influencing the relative abundance of microorganisms, finally affecting the removal of pollutants. Among them, the removal efficiency of total nitrogen (TN), NO3−-N, and total phosphorus (TP), and the relative abundance of denitrifying microorganisms in the CWR-Cu (uniform placement of sustained-release carbon source) were significantly higher than those in the CWR-Ca (centralized placement above) and CWR-Cb (centralized placement below) (p < 0.05). The surface C:O (carbon:oxygen) ratio of sustained-release carbon source after water treatment showed a decreasing trend, and CWR-Cu exhibited the greatest decrease in C:O ratio. In summary, CWR-Cu achieved the highest utilization of the carbon source and produced the largest number of heterotrophic microorganisms. This study reveals that CWR-Cu is a structural process for the efficient removal of nitrogen and phosphorus pollutants, and our findings provide theoretical basis and technical support for actual projects. creator: Yuechang Wang creator: Lin-Lan Zhuang creator: Shuang Liu creator: Yuanjun Su creator: Zhen Hu creator: Jian Zhang creator: Xiaoping Wang creator: Shaoming Cui creator: Gang Peng creator: Shuting Xie uri: https://doi.org/10.7717/peerj.18819 license: https://creativecommons.org/licenses/by/4.0/ rights: © 2025 Wang et al. title: Composition of soil fungal communities and microbial activity along an elevational gradient in Mt. Jiri, Republic of Korea link: https://peerj.com/articles/18762 last-modified: 2025-01-15 description: Approximately 64% of the Republic of Korea comprises mountainous areas, which as cold and high-altitude regions are gravely affected by climate change. Within the mountainous and the alpine-subalpine ecosystems, microbial communities play a pivotal role in biogeochemical cycling and partly regulate climate change through such cycles. We investigated the composition and function of microbial communities, with a focus on fungal communities, in Republic of Korea’s second tallest mountain, Mt. Jiri, along a four-point-altitude gradient: 600-, 1,000-, 1,200-, and 1,400-m. Soil pH and elevation were negatively correlated, with soils becoming more acidic at higher altitude. Of the five soil enzyme activities analyzed, cellobiohydrolase, β-1,4-glucosidase, and β-1,4-xylosidase activity showed differences among the elevation levels, with lower activity at 600 m than that at 1,400 m. Soil microbial biomass correlated positively with increasing elevation and soil water content. The decrease in β-1,4-N-acetylglucosaminidase suggests a reduction in fungal biomass with increasing altitude, while factors other than elevation may influence the increase in activity of the cellobiohydrolase, β-1,4-glucosidase and β-1,4-xylosidase. Fungal alpha diversity did not exhibit an elevational trend, whereas beta diversity formed two clusters (600–1,000 m and 1,200–1,400 m). Community composition was similar among the elevations, with Basidiomycota being the most predominant phylum, followed by Ascomycota. Conversely, among the fungal communities at 1,000 m, Ascomycota was the most dominant, possibly due to increased pathotroph percentage. Elevational gradients induce changes in soil properties, vegetation, and climate factors such as temperature and precipitation, all of which impact soil microbial communities and altogether create a mutually reinforcing system. Hence, inspection of elevation-based microbial communities can aid in inferring ecosystem properties, specifically those related to nutrient cycling, and can partly help assess the oncoming direct and indirect effects of climate change. creator: Ana Mitcov creator: Daegeun Ko creator: Kwanyoung Ko creator: Jaeho Kim creator: Neung-Hwan Oh creator: Hyun Seok Kim creator: Hyeyeong Choe creator: Haegeun Chung uri: https://doi.org/10.7717/peerj.18762 license: https://creativecommons.org/licenses/by/4.0/ rights: © 2025 Mitcov et al. title: The impact of side and top arm techniques during the backstroke breakout phase on 15-meter swimming performance link: https://peerj.com/articles/18838 last-modified: 2025-01-15 description: BackgroundResearch on the swimming starts and turns in professional swimming has become increasingly refined. The breakout phase is a crucial transition from point between underwater and above-water movements. The side arm technique is commonly used during the backstroke breakout phase. However, some swimmers have also achieved good performance using the top arm technique. The impact of the two techniques during the backstroke breakout phase is yet to be explored.PurposeTo compare the velocity and key angles differences between the side arm and top arm techniques and analyze their effect on the first 15-m performance after push-off.MethodsThe subjects were 16 high-level swimmers: eight males (20.4 ± 1.6 yr) and eight females (20.9 ± 1.7 yr). Of these, 14 were backstrokers or had individual medley as their primary event. The best performances in the history of the sport’s level World Aquatics Points are 682.1 ± 59.0 and 729.3 ± 41.5 for males and females, respectively. A within-subject design was used to test both the side arm and top arm techniques. Four underwater cameras were used to capture two-dimensional data from two perspectives, focusing on the breakout phase. A two-way ANOVA used to compare segment velocity, angles, and 15-m performance between the two genders and breakout techniques. Pearson’s correlation analysis was used to explore the relationship between segment velocity and 15-m performance, and hierarchical regression was employed to investigate the impact of breakout velocity on the 15-m performance.ResultsBoth male and female swimmers exhibited a significantly faster top arm velocities of (1.72 ± 0.20 and 1.47 ± 0.16 m/s, respectively) compared to the side arm velocities (1.51 ± 0.23 and 1.29 ± 0.19 m/s, respectively) during the breakout phase. Additionally, significant differences were found between the two genders (F = 11.189, p = 0.002, η2 = 0.286) and breakout techniques (F = 8.014, p = 0.008, η2 = 0.223), with no interaction effect (F = 0.037, p = 0.849, η2 = 0.001). Furthermore, both male (R = −0.447, p = 0.109) and female (R = −0.555, p = 0.017) swimmers showed a moderate positive correlation between breakout velocity and 15-m performance, and the regression model indicated a significant impact on the 15-m performance.ConclusionThe top arm technique during backstroke may offer a velocity advantage over the traditional side arm technique during the breakout phase, influencing 15-m performance. However, considering the short duration of the breakout phase, this advantage and its impact may need to be considered in conjunction with the smoothness of the transition to the subsequent phases. creator: Zhenyu Jin creator: Yuhang Zhou creator: Dapeng Wang creator: Yuhong Wen uri: https://doi.org/10.7717/peerj.18838 license: https://creativecommons.org/licenses/by/4.0/ rights: © 2025 Jin et al. title: Demography and homing behavior in the poorly-known Philippine flat-headed frog Barbourula busuangensis (Anura: Bombinatoridae) link: https://peerj.com/articles/18694 last-modified: 2025-01-14 description: The flat-headed frog, Barbourula busuangensis, is a poorly known, riverine species, endemic to the province of Palawan in the Philippines. We applied capture-mark-recapture (CMR) methods to follow individuals at two sites (Malbato and San Rafael) in the island of Busuanga over 10 months in 2022–2023. We used passive internal transponders (PITs) to mark adult and subadults and single-colored visual internal elastomers (VIEs) for cohorts of juveniles. From a total of 196 frogs PIT-tagged in Malbato and 144 in San Rafael, we obtained overall recapture rates of 49% and 60% respectively. We used the POPAN formulation in MARK software to estimate abundance, survival, movement, and age-class demographics. Our best model estimated an average population size of 268 frogs at Malbato and 232 at San Rafael, and constant survival probabilities (mean ≥ 0.97) at both sites. When adding age classes to the model, abundance of adults was always higher than that of subadults producing an age structure dominated by adults at both sites. Growth rates decreased significantly with body size, being higher in juveniles (1.51 mm/month) and subadults (1.56 mm/month) than in adult frogs (0.60 mm/month). At these growth rates frogs may reach adulthood at 2.5 years, with the oldest individuals likely being over 11 years old. CMR data confirmed site fidelity, and translocation experiments revealed that frogs have the ability to home when displaced 10–50 m upstream and downstream from their original capture site. This is the first long-term study of B. busuangensis using robust field and analysis methods. Our data suggest that B. busuangensis is stable at present in Busuanga, with long-lived adults and dispersing subadults. We expect that these data may serve as baseline of current population abundance, age structure and growth rates which are factors that tend to be affected when species are threatened. In this way it may help researchers and conservation practitioners detect potential changes that may occur as this species confronts the challenges of the Anthropocene. creator: Marta Miñarro creator: Patricia Burrowes creator: Claudia Lansac creator: Gregorio Sánchez-Montes creator: Leticia E. Afuang creator: Ignacio De la Riva uri: https://doi.org/10.7717/peerj.18694 license: https://creativecommons.org/licenses/by/4.0/ rights: © 2025 Miñarro et al. title: Acaricidal and insecticidal activities of entomopathogenic nematodes combined with rosemary essential oil and bacterium-synthesized silver nanoparticles against camel tick, Hyalomma dromedarii and wax moth, Galleria mellonella link: https://peerj.com/articles/18782 last-modified: 2025-01-14 description: An innovative approach to ticks and insect pests management is necessary to mitigate the challenges posed by the indiscriminate use of chemical pesticides, which can lead to resistance development and environmental pollution. Despite their great potential, biological control agents have significant manufacturing, application, and stability limitations. Currently, using phytochemicals, biosynthesized nanoparticles, and bioagents to get rid of arthropods might be a good alternative that would make farmers less worried about residues and resistance. The present investigation was carried out to determine for the first time the in vitro acaricidal and insecticidal efficacies of endogenous two entomopathogenic nematodes (EPNs), Heterorhabditis indica and Steinernema sp. combined with either Proteus mirabilis-synthesized silver nanoparticles or Rosmarinus officinalis essential oil against the camel tick, Hyalomma dromedarii larvae and females, and greater wax moth, Galleria mellonella larvae as well. We also determined the potential effects of these treatments on the biological characteristics of H. dromedarii’s engorged females. We further investigated R. officinalis essential oil (EO) profiling and nanoparticle (AgNPs) characterization. All the evaluated combinations demonstrated synergistic effects on the larvae of G. mellonella and H. dromedarii, as well as on engorged females. When H. indica was mixed with EO or AgNPs, it worked well than when Steinernema sp. was mixed with EO or AgNPs. This was shown by the highest number of tick and insect mortalities and the lowest lethal concentration (LC50) values. One day after G. mellonella was exposed to H. indica (1,000 infective juveniles (IJs)) together with EO at 60 or 40 mg/mL, all tested individuals died. We obtained the same results when H. dromedarii females exposed to the same level of EPN with 60 mg/mL EO, and when H. dromedarii larvae treated with H. indica at 500 IJs + EO at 25 mg/mL. Treatments altered all biological parameters of engorged females, revealing extremely noticeable differences between the treated and untreated groups. Gas chromatography–mass spectrometry (GC-MS) analysis identified a total of 28 compounds in the R. officinalis EO. Visual observation showed a color change from yellow to dark brown for AgNPs biosynthesized from P. mirabilis; the transmission electron microscopy (TEM) image and ultraviolet–visible (UV-Vis) spectrum showed well-dispersed particles with a diameter of 5–45 nm; and the greatest surface plasmon peaked at 320 nm. The results demonstrated the high efficacy of combining EPN, H. indica, with EO to control tick and insect pests. This is due to its acaricidal activity on different stages of H. dromedarii, including larvae and engorged females, and its larvicidal effect on G. mellonella. creator: Bander Albogami creator: Hadeer Darwish creator: Akram Alghamdi creator: Ahmed BahaaEldin Darwish creator: Wafa Mohammed Al-Otaibi creator: Mohamed A. Osman creator: Zamzam M. Al Dhafar creator: Abeer Mousa Alkhaibari creator: Abadi M. Mashlawi creator: Fadi Baakdah creator: Ahmed Noureldeen uri: https://doi.org/10.7717/peerj.18782 license: https://creativecommons.org/licenses/by/4.0/ rights: © 2025 Albogami et al. title: Benchmarking of a time-saving and scalable protocol for the extraction of DNA from diverse viromes link: https://peerj.com/articles/18785 last-modified: 2025-01-14 description: The virome, composed of viruses inhabiting diverse ecosystems, significantly influences microbial community dynamics and host health. The phenol-chloroform DNA extraction protocol for viromes, though effective, is time-intensive and requires the use of multiple toxic chemicals. This study introduces a streamlined, scalable protocol for DNA extraction using a commercially-available kit as an alternative, assessing its performance against the phenol-chloroform method across human fecal, mouse fecal, and soil samples. No significant differences in virome diversity or community composition were seen between methods. Most viral operational taxonomic units (vOTUs) were common to both methods, with only a small percentage unique to either approach. Alpha- and beta-diversity analyses showed no significant impact of the extraction method on virome composition, confirming the kit’s efficacy and versatility on sample types beyond those officially supported by the manufacturer. While the kit approach offers benefits like reduced toxicity and increased throughput, it has limitations such as higher costs and potential issues reliably capturing low-abundance taxa. This protocol provides a viable option for large-scale virome studies, although the phenol-chloroform approach may still be preferable for specific sample types. creator: Michael Shamash creator: Saniya Kapoor creator: Corinne F. Maurice uri: https://doi.org/10.7717/peerj.18785 license: https://creativecommons.org/licenses/by/4.0/ rights: © 2025 Shamash et al. title: Do goats recognise humans cross-modally? link: https://peerj.com/articles/18786 last-modified: 2025-01-14 description: Recognition plays a key role in the social lives of gregarious species, enabling animals to distinguish among social partners and tailor their behaviour accordingly. As domesticated animals regularly interact with humans, as well as members of their own species, we might expect mechanisms used to discriminate between conspecifics to also apply to humans. Given that goats can combine visual and vocal cues to recognise one another, we investigated whether this cross-modal recognition extends to discriminating among familiar humans. We presented 26 goats (17 males and nine females) with facial photographs of familiar people and two repeated playbacks of a voice, either congruent (from the same person) or incongruent with that photograph (from a different person). When cues were incongruent, violating their expectations, we expected goats to show changes in physiological parameters and moreover, respond faster and for longer after playbacks. Accordingly, heart rate decreased as the playback sequence progressed, but only when the face and voice presented were incongruent. Heart rate variability was also affected by congruency, but we were unable to determine precisely where differences lay. However, goats showed no changes in time taken to respond, or how long they responded for (our primary variables of interest). We also found evidence to suggest that shifts in cardiac responses may not have been robust. Although our findings could imply that goats had successfully perceived differences in congruency between the visual and vocal identity information presented, further evidence is needed to determine whether they are capable of cross-modal recognition of humans. creator: Marianne A. Mason creator: Stuart Semple creator: Harry H. Marshall creator: Alan G. McElligott uri: https://doi.org/10.7717/peerj.18786 license: https://creativecommons.org/licenses/by/4.0/ rights: ©2025 Mason et al.