Body size and temperature effects on standard metabolic rate for determining metabolic scope for activity of the polychaete Hediste (Nereis) diversicolor
Considering the ecological importance and potential value of Hediste diversicolor, a better understanding of its metabolic rate and potential growth rates is required. The aims of this study are: (i) to describe key biometric relationships; (ii) to test the effects of temperature and body size on standard metabolic rate (as measure by oxygen consumption) to determine critical parameters, namely Arrhenius temperature (TA), allometric coefficient (b) and reaction rate; and (iii) to determine the metabolic scope for activity (MSA) of H. diversicolor for further comparison with published specific growth rates. Individuals were collected in a Mediterranean lagoon (France). After 10 days of acclimatization, 7 days at a fixed temperature and 24 h of fasting, resting oxygen consumption rates (VO2) were individually measured in the dark at four different temperatures (11, 17, 22 and 27 °C) in worms weighing from 4 to 94 mgDW (n = 27 per temperature). Results showed that DW and L3 were the most accurate measurements of weight and length, respectively, among all the metrics tested. Conversion of WW (mg), DW (mg) and L3 (mm) were quantified with the following equations: DW = 0.15 × WW, L3 = 0.025 × TL(mm) + 1.44 and DW = 0.8 × L33.68. Using an equation based on temperature and allometric effects, the allometric coefficient (b) was estimated at 0.8 for DW and at 2.83 for L3. The reaction rate (VO2) equaled to 12.33 µmol gDW−1 h−1 and 0.05 µmol mm L3−1 h−1 at the reference temperature (20 °C, 293.15 K). Arrhenius temperature (TA) was 5,707 and 5,664 K (for DW and L3, respectively). Metabolic scope for activity ranged from 120.1 to 627.6 J gDW−1 d−1. Predicted maximum growth rate increased with temperature, with expected values of 7–10% in the range of 15–20 °C. MSA was then used to evaluate specific growth rates (SGR) in several experiments. This paper may be used as a reference and could have interesting applications in the fields of aquaculture, ecology and biogeochemical processes.
Galasso et al. (2018) Body size and temperature effects on standard metabolic rate for determining metabolic scope for activity of the polychaete Hediste (Nereis) diversicolor. PeerJ 6:e5675 https://doi.org/10.7717/peerj.5675
Egg perivitelline fluid of the invasive snail Pomacea canaliculata affects mice gastrointestinal function and morphology
Background Species beloging to the genus Pomacea (Ampullariidae), often referred as apple snails, are freshwater, amphibious snails native to South, Central and North America. Some species such as P. canaliculata have become a driver of ecosystem changes in wetlands and an important rice and taro pest after its introduction to Asia and other parts of the world. Females deposit colored egg clutches above the waterline, a reproductive strategy that exposes the eggs to harsh conditions and terrestrial predation. However, eggs have no reported predators in their native range, probably because of the acquisition of unparalleled biochemical defenses provided by a set of proteins (perivitellins) that nourish embryos and protect them from predators and abiotic factors. Notably, ingestion of egg perivitelline fluid (PVF) decreases rat growth rate and alters their gastrointestinal morphology. The aim of the study is to determine the effect of apple snail egg PVF on mice gut digestive activity, morphology and nutrient absorption. Methods Carbohydrate digestion by intestinal disaccharidases (sucrase-isomaltase and maltase-glucoamylase) was evaluated ex vivo in mice gavaged with 1 or 4 doses of PVF. Changes in gut morphological and absorptive surface were measured. In addition, alteration on nutrient absorption rates, transport pathways and intestinal permeability was evaluated by luminal perfusions of small intestine with radiolabeled L-proline (absorbed by paracellular and transcellular pathways) and L-arabinose (absorbed exclusively by paracellular pathway). Results Perivitelline fluid affected mice displayed significant morphological changes in the small intestine epithelium inducing the appearance of shorter and wider villi as well as fused villi. This resulted in a diminished absorptive surface, notably in the proximal portion. Likewise, the activity of disaccharidases diminished in the proximal portion of the intestine. Total absorption of L-proline increased in treated mice in a dose-dependent manner. There were no differences neither in the ratio of paracellular-to-transcellular absorption of L-proline nor in gut permeability as revealed by the clearance of L-arabinose. Discussion Oral administration of apple snail PVF to mice adversely alters gut morphophysiology by reducing the intestinal absorptive surface, affecting enzymes of sugar metabolism and increasing the absorption rate of nutrients without affecting the relative contribution of the absorption pathways or gut permeability. These results further support the role of PVF in passive anti-predator defenses in Pomacea snail eggs that target the digestive system.
Giglio et al. (2018) Egg perivitelline fluid of the invasive snail Pomacea canaliculata affects mice gastrointestinal function and morphology. PeerJ 6:e5314 https://doi.org/10.7717/peerj.5314
Using accelerometers to develop time-energy budgets of wild fur seals from captive surrogates
Background Accurate time-energy budgets summarise an animal’s energy expenditure in a given environment, and are potentially a sensitive indicator of how an animal responds to changing resources. Deriving accurate time-energy budgets requires an estimate of time spent in different activities and of the energetic cost of that activity. Bio-loggers (e.g., accelerometers) may provide a solution for monitoring animals such as fur seals that make long-duration foraging trips. Using low resolution to record behaviour may aid in the transmission of data, negating the need to recover the device. Methods This study used controlled captive experiments and previous energetic research to derive time-energy budgets of juvenile Australian fur seals (Arctocephalus pusillus) equipped with tri-axial accelerometers. First, captive fur seals and sea lions were equipped with accelerometers recording at high (20 Hz) and low (1 Hz) resolutions, and their behaviour recorded. Using this data, machine learning models were trained to recognise four states—foraging, grooming, travelling and resting. Next, the energetic cost of each behaviour, as a function of location (land or water), season and digestive state (pre- or post-prandial) was estimated. Then, diving and movement data were collected from nine wild juvenile fur seals wearing accelerometers recording at high- and low- resolutions. Models developed from captive seals were applied to accelerometry data from wild juvenile Australian fur seals and, finally, their time-energy budgets were reconstructed. Results Behaviour classification models built with low resolution (1 Hz) data correctly classified captive seal behaviours with very high accuracy (up to 90%) and recorded without interruption. Therefore, time-energy budgets of wild fur seals were constructed with these data. The reconstructed time-energy budgets revealed that juvenile fur seals expended the same amount of energy as adults of similar species. No significant differences in daily energy expenditure (DEE) were found across sex or season (winter or summer), but fur seals rested more when their energy expenditure was expected to be higher. Juvenile fur seals used behavioural compensatory techniques to conserve energy during activities that were expected to have high energetic outputs (such as diving). Discussion As low resolution accelerometry (1 Hz) was able to classify behaviour with very high accuracy, future studies may be able to transmit more data at a lower rate, reducing the need for tag recovery. Reconstructed time-energy budgets demonstrated that juvenile fur seals appear to expend the same amount of energy as their adult counterparts. Through pairing estimates of energy expenditure with behaviour this study demonstrates the potential to understand how fur seals expend energy, and where and how behavioural compensations are made to retain constant energy expenditure over a short (dive) and long (season) period.
Ladds et al. (2018) Using accelerometers to develop time-energy budgets of wild fur seals from captive surrogates. PeerJ 6:e5814 https://doi.org/10.7717/peerj.5814
Size-dependent functional response of Xenopus laevis feeding on mosquito larvae
Predators can play an important role in regulating prey abundance and diversity, determining food web structure and function, and contributing to important ecosystem services, including the regulation of agricultural pests and disease vectors. Thus, the ability to predict predator impact on prey is an important goal in ecology. Often, predators of the same species are assumed to be functionally equivalent, despite considerable individual variation in predator traits known to be important for shaping predator–prey interactions, like body size. This assumption may greatly oversimplify our understanding of within-species functional diversity and undermine our ability to predict predator effects on prey. Here, we examine the degree to which predator–prey interactions are functionally homogenous across a natural range of predator body sizes. Specifically, we quantify the size-dependence of the functional response of African clawed frogs (Xenopus laevis) preying on mosquito larvae (Culex pipiens). Three size classes of predators, small (15–30 mm snout-vent length), medium (50–60 mm) and large (105–120 mm), were presented with five densities of prey to determine functional response type and to estimate search efficiency and handling time parameters generated from the models. The results of mesocosm experiments showed that type of functional response of X. laevis changed with size: small predators exhibited a Type II response, while medium and large predators exhibited Type III responses. Functional response data showed an inversely proportional relationship between predator attack rate and predator size. Small and medium predators had highest and lowest handling time, respectively. The change in functional response with the size of predator suggests that predators with overlapping cohorts may have a dynamic impact on prey populations. Therefore, predicting the functional response of a single size-matched predator in an experiment may misrepresent the predator’s potential impact on a prey population.
Thorp et al. (2018) Size-dependent functional response of Xenopus laevis feeding on mosquito larvae. PeerJ 6:e5813 https://doi.org/10.7717/peerj.5813
Three, two, one! Revision of the long-bodied sphaerodorids (Sphaerodoridae, Annelida) and synonymization of Ephesiella, Ephesiopsis and Sphaerodorum
Background Long-bodied sphaerodorids (Annelida, Sphaerodoridae) is the common name for members of the three closely and morphologically homogenous currently accepted genera of benthic marine bristle worms: Ephesiella, Ephesiopsis and Sphaerodorum. Members of this group share the presence of two dorsal and longitudinal rows of macrotubercles with terminal papillae, and two longitudinal rows of microtubercles, features that are unique among sphaerodorids. Genera are distinguished by the chaetae morphology. Members of Ephesiella are characterised by having compound chaetae (except, sometimes, simple chaetae in the first chaetigers), Sphaerodorum bear only simple chaetae, and Ephesiopsis have both compound and simple chaetae in all parapodia. Methods Mitochondrial (partial COI and 16S rDNA) and nuclear (partial 18S rDNA and 28S rDNA) sequence data of long-bodied sphaerodorids with compound and simple chaetae, and an outgroup of additional seven sphaerodorid species were analysed separately and in combination using Bayesian inference (BA), and Maximum Likelihood (ML) methods. Long-bodied sphaerodorids from around the world (including type specimens) were examined under a range of optical equipment in order to evaluate putative generic and specific diagnostic features, in addition to intraspecific variability. Results Phylogenetic analyses of mitochondrial and nuclear DNA sequences of specimens identified as Ephesiella and Sphaerodorum, based on chaeta morphology, were performed. Sphaerodorum and Ephesiella were recovered as paraphyletic and nested within each other. Revision of current nominal species diagnostic features are performed and discussed. Discussion Results contradict current generic definitions. Recovery of paraphyletic compound and simple chaetae clades urge the synonymization of these two genera of long-bodied sphaerodorids. Morphological data also suggest the synonymization of Ephesiopsis.
Capa et al. (2018) Three, two, one! Revision of the long-bodied sphaerodorids (Sphaerodoridae, Annelida) and synonymization of Ephesiella, Ephesiopsis and Sphaerodorum. PeerJ 6:e5783 https://doi.org/10.7717/peerj.5783
Evolution of African barbs from the Lake Victoria drainage system, Kenya
The Lake Victoria drainage basin (LVD) in Kenya is home to ten nominal species of small barbs (Enteromius) and one of large barbs (Labeobarbus altianalis). A recent molecular study genetically characterized small barbs in this region and found evidence of introgression between certain species, complicating the taxonomy and species identification of these fishes. This study aimed to extend our understanding on the evolution of these fishes by: (1) determining whether putatively pure individuals of Enteromius cercops are found in the Kenyan LVD, as the previous study only found hybrid individuals of this species in this region; (2) testing the sister relationship between Enteromius profundus, endemic to Lake Victoria, and Enteromius radiatus, also found in Lake Victoria, which had been previously synonymized; (3) examining the phylogenetic relationships of small barbs of the Kenyan LVD with those reported from other ichthyological provinces of Africa; and (4) examining the phylogenetic relationships of Labeobarbus altianalis with other Labeobarbus species. To this end, we obtained mitochondrial Cytochrome b and nuclear Growth Hormone (GH) intron 2 gene sequences of nine Enteromius species from the LVD in Kenya, as well as cytochrome b sequences for L. altianalis. We conducted Maximum likelihood and Bayesian phylogenetic analyses to establish their evolutionary relationships in relation to many other barbs specimens from Africa. Phylogenetic analyses did not reveal instances of hybridization/introgression among the individuals sequenced by us. A sister relationship between E. profundus and E. radiatus was not found. This latter species shows instead a sister relationship with a lineage comprised of two species from West Africa. Other sister relationships between taxa from the East coast and other ecoregions from Africa are observed, suggesting that past drainage connections and vicariant events contributed to the diversification of Enteromius. Finally, only a single haplotype was recovered among the L. altianalis individuals examined, which is most similar to a specimen from Lake Edward in Uganda.
Ndeda et al. (2018) Evolution of African barbs from the Lake Victoria drainage system, Kenya. PeerJ 6:e5762 https://doi.org/10.7717/peerj.5762
Spatial analyses of threats to ecosystem service hotspots in Greater Durban, South Africa
Background Population growth at all scales and rapid rates of urbanization, particularly in the global South, are placing increasing pressure on ecosystems and their ability to provide services essential for human well-being. The spatial consideration of threats to ecosystem services related to changes in land use is necessary in order to avoid undue impacts on society due to the loss or reduced supply of ecosystem services. This study assesses the potential threats of land use change from strategic and local development proposals to ecosystem services in the city of Durban. Methods We analysed the spatial relationship between five categories of ecosystem service hotspots (carbon storage, water yield, sediment retention, nutrient retention and flood attenuation) and urban land use change related to selected strategic planning proposals, development proposals and sand-mining applications in Durban, South Africa (eThekwini Municipality) with a view to determining the consequences for progress towards a more sustainable development path in the city. We identified the potential levels of threat related to habitat destruction or transformation for the five categories of ecosystem services and a subset of 13 ecosystem service hotspots, using GIS spatial analysis tools. Results The results show that on average, should Durban’s strategic development plans be realised, approximately 42% loss of ecosystem service hotspots is expected in the two municipal town-planning regions assessed. With respect to development applications between 2009 and 2012, approximately 36% of all environmental impact assessments and 84% of sand mining applications occurred within ecosystem service hotspots within Durban. Discussion The findings highlight the tension between short-term development pressures and longer-term sustainability goals and confirm that current planning and development proposals pose a threat to ecosystems and their ability to deliver services that support human well-being in Durban. We suggest practical solutions to include ecosystem services into local government decision-making.
Spatial and Geographic Information Science
Davids et al. (2018) Spatial analyses of threats to ecosystem service hotspots in Greater Durban, South Africa. PeerJ 6:e5723 https://doi.org/10.7717/peerj.5723
Inhibitory effect of microalgae and cyanobacteria extracts on influenza virus replication and neuraminidase activity
Background The influenza virus can cause seasonal infections with mild to severe symptoms, circulating worldwide, and it can affect people in any age group. Therefore, this infection is a serious public health problem that causes severe illness and death in high-risk populations. Every year, 0.5% of the world’s population is infected by this pathogen. This percentage can increase up to ten times during pandemics. Influenza vaccination is the most effective way to prevent disease. In addition, anti-influenza drugs are essential for prophylactic and therapeutic interventions. The oseltamivir (OST, a neuraminidase inhibitor) is the primary antiviral used in clinics during outbreaks. However, OST resistant viruses may emerge naturally or due to antiviral pressure, with a prevalence of 1–2% worldwide. Thus, the search for new anti-influenza drugs is extremely important. Currently, several groups have been developing studies describing the biotechnological potential of microalgae and cyanobacteria, including antiviral activity of their extracts. In Brazil, this potential is poorly known and explored. Methods With the aim of increasing the knowledge on this topic, 38 extracts from microalgae and cyanobacteria isolated from marine and freshwater biomes in Brazil were tested against: cellular toxicity; OST-sensitive and resistant influenza replications; and neuraminidase activity. Results For this purpose, Madin-Darby Canine Kidney (MDCK)-infected cells were treated with 200 μg/mL of each extract. A total of 17 extracts (45%) inhibited influenza A replication, with seven of them resulting in more than 80% inhibition. Moreover, functional assays performed with viral neuraminidase revealed two extracts (from Leptolyngbya sp. and Chlorellaceae) with IC50 mean < 210 μg/mL for influenza A and B, and also OST-sensitive and resistant strains. Furthermore, MDCK cells exposed to 1 mg/mL of all the extracts showed viability higher than 80%. Discussion Our results suggest that extracts of microalgae and cyanobacteria have promising anti-influenza properties. Further chemical investigation should be conducted to isolate the active compounds for the development of new anti-influenza drugs. The data generated contribute to the knowledge of the biotechnological potential of Brazilian biomes that are still little explored for this purpose.
Silva et al. (2018) Inhibitory effect of microalgae and cyanobacteria extracts on influenza virus replication and neuraminidase activity. PeerJ 6:e5716 https://doi.org/10.7717/peerj.5716
Impact of organic and inorganic fertilizers on the yield and quality of silage corn intercropped with soybean
Background Corn silage is an important feed for intense ruminant production, but the growth of corn relies heavily on the use of chemical fertilizers. Sustainable crop production requires careful management of all nutrient sources available on a farm, particularly in corn-based cropping systems. Methods Experiments were conducted to determine the appropriate technique of corn-legume intercropping in conjunction with the supplemental use of chemical fertilizers, organic manure, and biofertilizers (BFs). Acetylene reduction assays (ARAs) were also performed on corn and soybean roots. Results Combining chemical fertilizers with chicken manure (CM) in a 50:50 ratio and applying 50% NPK+50% CM+BF produced fresh forage and dry matter (DM) yields that were similar to those produced in the 100% nitrogen (N), phosphorus (P), potassium (K) treatment. Among the lone fertilizer treatments, the inorganic fertilizer (100% NPK) treatment produced the highest DM yield (13.86 t/ha) of forage and outyielded the 100% CM (9.74 t/ha) treatment. However, when CM was combined with NPK, the resulting DM yield of forage (13.86 t/ha) was the same as that resulting from 100% NPK (13.68 t/ha). Compared with CM applications alone, combinations of NPK and CM applications resulted in increased plant height, crop growth rates (CGRs) and leaf area index (LAI), but the values of these parameters were similar to those resulting from 100% NPK application. Fertilizers in which the ratio was 50% CM+50% NPK or 50% CM+50% NPK+BF resulted in protein yields that were similar to those resulting from conventional fertilizers. Similarly, the CP content did not significantly differ between applications of the 100% NPK and 50% CM+50% NPK fertilizers. The use of BFs had no significant impact on improving either the yield or quality of forage fertilized with inorganic or organic fertilizer. Lactic acid responded differently to different fertilizer applications and was significantly higher in the fertilized plots than in the unfertilized plots. Compared with treatments of lone chemical and lone organic manure fertilizers, treatments involving applications of BF and a combination of BF and NPK or CM resulted in higher ARA values. Discussion There is no simple and easy approach to increase biological nitrogen fixation (BNF) in grain legumes grown as part of a cropping system under realistic farm field conditions. Overall, evidence recorded from this study proves that, compared with corn monocrops combined with CM and chemical fertilizers, corn-soybean intercrops could increase forage yields and quality, produce higher total protein yields, and reduce the need for protein supplements and chemical fertilizers.
Baghdadi et al. (2018) Impact of organic and inorganic fertilizers on the yield and quality of silage corn intercropped with soybean. PeerJ 6:e5280 https://doi.org/10.7717/peerj.5280
Estimation of antimicrobial activities and fatty acid composition of actinobacteria isolated from water surface of underground lakes from Badzheyskaya and Okhotnichya caves in Siberia
Extreme and unusual ecosystems such as isolated ancient caves are considered as potential tools for the discovery of novel natural products with biological activities. Actinobacteria that inhabit these unusual ecosystems are examined as a promising source for the development of new drugs. In this study we focused on the preliminary estimation of fatty acid composition and antibacterial properties of culturable actinobacteria isolated from water surface of underground lakes located in Badzheyskaya and Okhotnichya caves in Siberia. Here we present isolation of 17 strains of actinobacteria that belong to the Streptomyces, Nocardia and Nocardiopsis genera. Using assays for antibacterial and antifungal activities, we found that a number of strains belonging to the genus Streptomyces isolated from Badzheyskaya cave demonstrated inhibition activity against bacteria and fungi. It was shown that representatives of the genera Nocardia and Nocardiopsis isolated from Okhotnichya cave did not demonstrate any tested antibiotic properties. However, despite the lack of antimicrobial and fungicidal activity of Nocardia extracts, those strains are specific in terms of their fatty acid spectrum. When assessing fatty acid profile, we found that polyunsaturated fatty acids were quantitatively dominant in extracts of Nocardia sp. and Streptomyces sp. grown in different media. Saturated fatty acids were the second most abundant type in the fatty acid profile. It was due to palmitic acid. Also, a few monounsaturated fatty acids were detected. The obtained materials can become a basis for development of approaches to use bacteria isolated from caves as a biological sources of bioactive compounds to create medical and veterinary drugs.
Voytsekhovskaya et al. (2018) Estimation of antimicrobial activities and fatty acid composition of actinobacteria isolated from water surface of underground lakes from Badzheyskaya and Okhotnichya caves in Siberia. PeerJ 6:e5832 https://doi.org/10.7717/peerj.5832