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A long-lived, estuarine-resident fish species selects its macroinvertebrate food source based on certain prey and predator traits
No full textThis study has explored the extent to which the predominant faunal component of the diet (benthic macroinvertebrates) of the large, long-lived estuarine-resident Acanthopagrus butcheri is related to particular prey and predator traits. Focus is placed on the location (infaunal vs epifaunal) and species size category (small vs medium vs large) of the prey and feeding behaviour of A. butcheri. Data on the benthic macroinvertebrates in the stomach contents of A. butcheri in a microtidal estuary (Swan-Canning, Western Australia) are compared with those of macroinvertebrates sampled in the benthos at the same sites and times in eight consecutive seasons using an Ekman grab. The eight most abundant small macroinvertebrate species in the benthic samples were infaunal and, apart from the bivalve Arthritica semen that was ingested by only a few fish, were not fed on by A. butcheri. In contrast, the three most abundant medium and large-sized species in the benthos, the epifaunal bivalves Xenostrobus securis and Fluviolanatus subtortus and infaunal nereidid polychaete Simplisetia aequisetis, were preyed on substantially, with the first ingested by 54% of A. butcheri and contributing over 51% to dietary volume. Although the eunicid polychaete Marphysa sanguinea occurred in only 7% of benthic samples and contributed <0.1% to abundance, this large infaunal species ranked second in contribution to dietary volume (12%). This species and S. aequisetis were preyed on when they emerged in part or wholly above the substrata. The above results imply that, in terms of prey, A. butcheri selects predominantly medium and large epifaunal macroinvertebrate species and those medium to large infaunal polychaetes which, at times, move out of the substrata. This reflects non-emergent infauna being present in essentially all benthic samples and contributing 66% to total abundance, whereas this group was found in only 8% of stomach samples of A. butcheri and contributed only 2% to dietary volume. In contrast, emergent infauna and epifauna contributed 12 and 22%, respectively, to abundance in the benthos, but as much as 22 and 75%, respectively, to the diets of A. butcheri. It is concluded that the marked selectivity of A. butcheri for prey was related to certain prey and predator traits, i.e. size category of prey species, and prey located above the substrata, either permanently or at frequent intervals, and to visual acuity and a fast-swimming angled attack by the predator
Hierarchically structured LaFeO3 with hollow core and porous shell as efficient sensing material for ethanol detection
No full textHollow LaFeO3 (LFO-HS) was synthesized by a facile hydrothermal method with the use of cetyltrimethylammonium bromide. Its structural, morphological, microstructural and textual characterizations were performed using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and nitrogen adsorption-desorption analysis. The gas-sensing performance of LFO-HS sensor was studied towards different gases, including ammonia (NH3), ethanol (C2H5OH), acetone (CH3COCH3), and liquefied petroleum gas (LPG). The LFO-HS sensor exhibited p-type gas sensing behavior and enhanced sensing performance towards ethanol gas as compared with bulk LaFeO3 sensor. A rapid, high, and stable response was seen at 300 °C. Meanwhile, a linear response and low limit of detection (1 ppb) to ethanol was observed. After the investigation on sensitivity to different reducing gases, our results revealed that the LFO-HS sensor exhibited good selectivity to ethanol and suggested it being a promising sensor candidate for future practical use in trace ethanol detection
Does the need to drink influence nest site selection in a wide-ranging threatened cockatoo?
No full textConserving wide-ranging species is challenging and requires an understanding of resource selection at multiple spatial scales, including how functional resources interact. Understanding this interaction is likely to be particularly important if resources are rare, such as tree hollows, or likely to change into the future under climate change, such as water availability and distribution. We examined nest selection by Karak (Calyptorhynchus banksii naso), a threatened obligate tree hollow nester endemic to south-western Australia, globally one of the regions most affected by climate change. We aimed to identify factors influencing nest hollow selection at multiple spatial scales including interactions between functional resources. We found that nest selection occurred primarily at the hollow scale, with deeper, higher hollows selected, and at the landscape scale, with hollows closer to ephemeral and permanent drink sites selected. The preference for specific types of hollows indicated that suitable hollows are likely to be scarce in the landscape and that management prescriptions need to be developed to maintain the supply of suitable hollows. Maintenance of drink sites in an area experiencing significant declines in rainfall will require more novel management prescriptions, which could potentially include the provision of artificial drink sites. Overall, our study demonstrated the importance of understanding interactions between functional resources at large spatial scales for the effective conservation of wide-ranging species
Growth estimates of young‐of‐the‐year broadnose sevengill shark, Notorynchus cepedianus , a top predator with poorly calcified vertebrae
No full textThe broadnose sevengill shark, Notorynchus cepedianus (Péron, 1807), is a large marine top predator in temperate coastal ecosystems. Some aspects of its life history have been determined, but its growth pattern is yet to be fully understood. The authors used a multi-modelling approach and a sensitivity test to estimate growth parameters from young-of-year (YOY) length data collected off San Antonio Cape (SAC), Argentina, a critical habitat in the Southwest Atlantic Coastal Zone (SACZ). The best selected model, a sex-combined logistic growth model, estimated an asymptotic length (L∞) of 92.58 cm TL (95% C.I.: 86.48–105.89 cm), a growth coefficient (K) of 0.006818 days −1 (95% C.I.: 0.004948–0.008777) and a size at birth (L0) of 40.73 cm. The predicted annual growth (i.e., L1 – L0) was 43.2 cm TL. Males had smaller L0, higher K and achieved larger sizes after 1 year. The YOY in SAC attained a larger L1 and grew faster than their Australian and South African wild counterparts. The consistent year-round presence of YOY in the SAC highlights the importance of this area as a pupping ground and potential nursery for N. cepedianus; this has direct implications for the allocation of research and management effort for the conservation of this species in the Southwest Atlantic
Dietary gamma-aminobutyric acid supplementation does not mitigate stress responses in weaner pigs given adrenocorticotropic hormone and experimentally infected with enterotoxigenic Escherichia coli
No full textGamma-aminobutyric acid (GABA) is a non-protein amino acid, a major inhibitory neurotransmitter in the central nervous system that stimulates feed intake and inhibits the hypothalamic-pituitary-adrenal (HPA) axis. We hypothesised that: (1) GABA supplementation in the diet would reduce markers of the stress response in weaned pigs injected with adrenocorticotropic hormone (ACTH) and inoculated with enterotoxigenic Escherichia coli (ETEC); and (2) this reduction in stress responses would improve performance after weaning. A total of 96 newly-weaned male pigs (Large White x Landrace) were stratified into a two by four factorial arrangement with respective factors being (i) with/without ACTH injection and ETEC infection (challenge versus non-challenge) and (ii) four dietary GABA levels (0, 60, 80, 100 mg/kg). On days 8 and 9 after weaning, piglets were orally inoculated with ETEC (0.8 ml via two gelatinized capsules; serotype O149; F4) as well as being given 5 IU ACTH intramuscularly (IM), which occurred an hour before ETEC inoculation. Pigs in the non-challenged group were given IM 0.2 mL of sterile saline and sham infected with two capsules of PBS. Faecal consistency scores were recorded daily, pigs and feed were weighed weekly to determine performance and blood samples were collected at days 6, 9 and 14. GABA supplementation did not reduce plasma cortisol. However challenged pigs had higher levels compared to the non-challenge group at day 9 (P = 0.001). Performance was not influenced by GABA supplementation (P > 0.05). Between days 8–14, 54.3% of pigs in the challenge group developed diarrhoea compared to 5.6% in the non-challenged group (P = 0.001). These data indicate that eliciting both an ETEC infection challenge and an acute stress response after weaning initiated an endocrine stress response. The use of GABA in feed did not reduce this stress response, reduce diarrhoea or improve production performance
Ecoregional and temporal dynamics of dugong habitat use in a complex coral reef lagoon ecosystem
Get PDFMobile marine species display complex and nonstationary habitat use patterns that require understanding to design effective management measures. In this study, the spatio-temporal habitat use dynamics of the vulnerable dugong (Dugong dugon) were modelled from 16 satellite-tagged individuals in the coral reef lagoonal ecosystems of New Caledonia, South Pacific. Dugong residence time was calculated along the interpolated tracks (9371 hourly positions) to estimate intensity of use in three contrasting ecoregions, previously identified through hierarchical clustering of lagoon topographic characteristics. Across ecoregions, differences were identified in dugong spatial intensity of use of shallow waters, deeper lagoon waters and the fore-reef shelf outside the barrier reef. Maps of dugong intensity of use were predicted from these ecological relationships and validated with spatial density estimates derived from aerial surveys conducted for population assessment. While high correlation was found between the two datasets, our study extended the spatial patterns of dugong distribution obtained from aerial surveys across the diel cycle, especially in shallow waters preferentially used by dugongs at night/dusk during high tide. This study has important implications for dugong conservation and illustrates the potential benefits of satellite tracking and dynamic habitat use modelling to inform spatial management of elusive and mobile marine mammals
Low quantities of marine debris at the northern Ningaloo Marine Park, Western Australia, influenced by visitation and accessibility
No full textMarine debris (MD) is a serious environmental concern globally. Yet, few studies have reported on MD in sanctuary zones of the Indian Ocean. Consequently, coastal transects were conducted to determine MD quantity, composition and distribution at northern Ningaloo Marine Park, Western Australia. Debris density ranged between 0.004 and 0.02 items m−2 with the greatest density near Exmouth township. Composition was predominantly plastic (61%) with fishing-related items (25.5%) and plastic fragments/remnants (16%) the most numerous overall. Land-based and general sourced MD accounted for 88% of all debris. Debris levels were significantly lower at sites with higher visitation and increased distance from access points. There was no significant difference between sanctuary and non-sanctuary zones. Although not immune to MD, this study suggests its remote location, environmental awareness and management strategies implemented at Ningaloo Marine Park may be key to its low MD levels
A review of the molecular epidemiology of Cryptosporidium spp. and Giardia duodenalis in the Middle East and North Africa (MENA) region
Get PDFCryptosporidium spp. and Giardia duodenalis are important protozoan parasites which are associated with diarrheal diseases in humans and animals worldwide. Relatively little is known about the molecular epidemiology of Cryptosporidium spp. and Giardia duodenalis in the Middle East Countries and North Africa (MENA region). Therefore, this review aimed to inspect published genotyping and subtyping studies on Cryptosporidium spp. and Giardia duodenalis in the MENA region. These studies indicate that both anthroponotic and zoonotic transmission of Cryptosporidium occurs with the predominance of zoonotic transmission in most countries. Seven Cryptosporidium species were identified in humans (C. parvum, C. hominis, Cryptosporidium meleagridis, C. felis, Cryptosporidium muris, C. canis and C. bovis), with C. parvum by far being the most prevalent species (reported in 95.4% of the retrieved studies). Among C. parvum gp60 subtype families, IIa and IId predominated, suggesting potential zoonotic transmission. However, in four MENA countries (Lebanon, Israel, Egypt and Tunisia), C. hominis was the predominant species with five subtype families reported including Ia, Ib, Id, If and Ie, all of which are usually anthroponotically transmitted between humans. In animals, the majority of studies were conducted mainly on livestock and poultry, 15 species were identified (C. parvum, C. hominis, C. muris, Cryptosporidium cuniculus, C. andersoni, C. bovis, C. meleagridis, C. baileyi, C. erinacei, C. ryanae, C. felis, C. suis, Cryptosporidium galli, C. xiaoi and C. ubiquitum) with C. parvum (IIa and IId subtypes) the dominant species in livestock and C. meleagridis and C. baileyi the dominant species in poultry. With G. duodenalis, five assemblages (A, B, C, E and F) were identified in humans and six (A, B, C, E, D and F) in animals in MENA countries with assemblages A and B commonly reported in humans, and assemblages A and E dominant in livestock. This review also identified a major knowledge gap in the lack of Cryptosporidium spp. and Giardia duodenalis typing studies in water and food sources in the MENA region. Of the few studies conducted on water sources (including drinking and tap water), ten Cryptosporidium species and four genotypes were identified, highlighting the potential role of water as the major route of Cryptosporidium spp. transmission in the region. In addition, three G. duodenalis assemblages (A, B and E) were detected in different water sources with AI, AII and BIV being the main sub-assemblages reported. More research is required in order to better understand the molecular diversity and transmission dynamics of Cryptsporidum spp. and Giardia duodenalis in humans, animals, water and food sources in MENA region
Enhancement of thermal and mechanical stabilities of silicon doped titanium nitride coating by manipulation of sputtering conditions
Get PDFThis study investigates the influence of substrate (AISI M42 tool steel) bias voltage (from −30 to −80 V), on the mechanical properties of magnetron sputtered TiSiN coating derived from Ti and Si targets. Thermal stability, microstructure (crystallite size, microstrain, lattice constant), morphology and mechanical (hardness, Young's modulus, residual stresses) properties, of the deposited TiSiN coatings, were investigated with synchrotron powered X-ray diffraction (SR-XRD), X-ray photoelectron spectroscopy, field emission scanning electron microscopy, and nanoindentation techniques. Rietveld analysis, of the in-situ SR-XRD, in the temperature range of 25–800 °C, demonstrated cubic TiN form in (Ti,Si)N solid solutions, with TiO2 and Ti2O3 identified at lower bias voltages. Density functional theory supplemented the experimental results.
Increase in the bias voltage resulted in: (i) a decrease in Si content, (ii) significant smoothening of surface morphology, (iii) change in the phase composition and microstructure, (iv) improved oxidation resistance and thermal oxidation threshold, and (v) hardness and Young's modulus of the coatings increased up to 50% to 33 GPa and 450 GPa, respectively
