Small Organisms Research Articles

Mechanisms underlying the epipelagic ecosystem response to ENSO in the equatorial Pacific ocean

The El Niño/Southern Oscillation is known to strongly impact marine ecosystems and fisheries. In particular, El Niño years are characterized, among other things, by a decrease in tuna catches in the western Pacific and an increase in the central Pacific, whereas these catches accumulate in the far western Pacific during La Niña conditions. However, the processes driving this zonal shift in the tuna catch (changing habitat conditions, currents or food availability) remain unclear. Here, we use an hindcast simulation from the mechanistic ecosystem model APECOSM that reasonably reproduces the observed zonal shift of the epipelagic community in response to ENSO to understand the mechanisms underlying this shift.Although the response of modeled epipelagic communities to El Niño is relatively similar for the different size classes studied, the processes responsible for these changes vary considerably by organism size. One of the major results of our analysis is the critical role of eastward passive transport by El Niño-related surface current anomalies for all size classes. While the effects of passive transport dominate the effects of growth and predation changes for large organisms, this is not the case for intermediate-sized organisms in the western Pacific, where the decrease in biomass is first explained by increased predation and then decreased foraging success. For small organisms, changes in growth rate, induced by the influence of temperature on fish physiology, is an important process that reinforces the biomass increase induced by passive horizontal transport in the eastern Pacific and the biomass decrease induced by increased predation by intermediate-sized organisms near the dateline. Finally, contrary to what is often assumed, our model shows that active habitat-based movements are not required to explain the westward biomass shifts that are observed during ENSO.This study illustrates the relevance of using a mechanistic ecosystem model to disentangle the role of the different processes controlling biomass changes. It highlights the essential dynamic role of ocean currents in shaping the response of marine communities to climate variability and its interaction with biological (e.g. growth) and ecological (e.g. foraging and predation) processes, whose relative importance varies with organisms’ size and contribute to modify the community structure.

Winners and Losers of Atlantification: The Degree of Ocean Warming Affects the Structure of Arctic Microbial Communities.

Arctic microbial communities (i.e., protists and bacteria) are increasingly subjected to an intrusion of new species via Atlantification and an uncertain degree of ocean warming. As species differ in adaptive traits, these oceanic conditions may lead to compositional changes with functional implications for the ecosystem. In June 2021, we incubated water from the western Fram Strait at three temperatures (2 °C, 6 °C, and 9 °C), mimicking the current and potential future properties of the Arctic Ocean. Our results show that increasing the temperature to 6 °C only minorly affects the community, while an increase to 9 °C significantly lowers the diversity and shifts the composition. A higher relative abundance of large hetero- and mixotrophic protists was observed at 2 °C and 6 °C compared to a higher abundance of intermediate-sized temperate diatoms at 9 °C. The compositional differences at 9 °C led to a higher chlorophyll a:POC ratio, but the C:N ratio remained similar. Our results contradict the common assumption that smaller organisms and heterotrophs are favored under warming and strongly indicate a thermal limit between 6 °C and 9 °C for many Arctic species. Consequently, the magnitude of temperature increase is a crucial factor for microbial community reorganization and the ensuing ecological consequences in the future Arctic Ocean.

New insights into the diversity of cryptobenthic Cirripectes blennies in the Mascarene Archipelago sampled using Autonomous Reef Monitoring Structures (ARMS).

Autonomous Reef Monitoring Structures (ARMS) are artificial mini-reefs designed for standardized sampling of sessile and small motile cryptobenthic organisms. ARMS are also effective for collecting small cryptobenthic fishes, such as the combtooth blennies of the genus Cirripectes. Recent studies discovered several Cirripectes species endemic to islands or archipelagos, in spite of the generally broad distributions of tropical and subtropical blennies. Thus, to evaluate the diversity and distribution of Cirripectes species in the Mascarene Archipelago, a little-studied region but an important biodiversity hotspot, complete mitochondrial genomes, and nuclear rhodopsin genes were sequenced for 39 specimens collected with ARMS deployed on outer reef slopes at Reunion and Rodrigues islands. Mitochondrial COI sequences were analyzed to integrate these specimens within the largest dataset of publicly available sequences. Three species were found in the Mascarene Archipelago, Cirripectes castaneus, Cirripectes randalli, and Cirripectes stigmaticus. C.castaneus and C.stigmaticus both have an Indo-Pacific distribution with several haplotypes shared among distant localities. In agreement with the literature, C.randalli shows a small-range endemism restricted to the Mascarenes. We confirmed the presence of C.castaneus, C.randalli, and C.stigmaticus in Rodrigues, and the presence of C.stigmaticus in Reunion. This study contributes to filling the gaps in taxonomic and molecular knowledge of the reef cryptobiome in the South-West Indian Ocean, and provides the first complete mitogenomes for the genus, a crucial step for future molecular-based inventories (e.g., eDNA).

Including filter-feeding gelatinous macrozooplankton in a global marine biogeochemical model: model–data comparison and impact on the ocean carbon cycle

Abstract. Filter-feeding gelatinous macrozooplankton (FFGM), namely salps, pyrosomes and doliolids, are increasingly recognized as an essential component of the marine ecosystem. Unlike crustacean zooplankton (e.g., copepods) that feed on prey that are an order of magnitude smaller, filter feeding allows FFGM to have access to a wider range of organisms, with predator-over-prey size ratios as high as 105:1. In addition, most FFGM produce carcasses and/or fecal pellets that sink 10 times faster than those of copepods. This implies a rapid and efficient export of organic matter to depth. Even if these organisms represent < 5 % of the overall planktonic biomass, their associated organic matter flux could be substantial. Here we present a first estimate of the influence of FFGM on the export of particulate organic matter to the deep ocean based on the marine biogeochemical model NEMO-PISCES (Nucleus for European Modelling of the Ocean, Pelagic Interaction Scheme for Carbon and Ecosystem Studies). In this new version of PISCES, two processes characterize FFGM: the preference for small organisms due to filter feeding and the rapid sinking of carcasses and fecal pellets. To evaluate our simulated FFGM distribution, we compiled FFGM abundance observations into a monthly biomass climatology using a taxon-specific biomass–abundance conversion. Model–observation comparison supports the model's ability to quantify the global and large-scale patterns of FFGM biomass distribution but reveals an urgent need to better understand the factors triggering the boom-and-bust FFGM dynamics before we can reproduce the observed spatio-temporal variability of FFGM. FFGM substantially contribute to carbon export at depth (0.4 Pg C yr−1 at 1000 m), particularly in low-productivity regions (up to 40 % of organic carbon export at 1000 m), where they dominate macrozooplankton biomass by a factor of 2. The FFGM-induced export increases in importance with depth, with a simulated transfer efficiency close to 1.

Diversity of Aquatic Beetles (Dytiscidae) along the Altitudinal Gradient and its Relationship with Physico-Chemical Parameters of Water at Tashiding, Tsendagang and Gozhi Gewogs, Dagana, Bhutan

Dytiscidae plays a vital role in the ecosystem; purifies water and serv es as the prey on many organisms. This family of aquatic beetles as predators feeds on small organisms. They are sensitive to environmental changes, it is used as a biodiversity indicator and also a tool for conservation assessment. This study assessed the diversity of Dytiscidae in relation to physico-chemical parameters of water using stratified random sampling at three Geogs in Dagana. Furthermore, the relationship of Dytiscid diversity and taxon richness with the physico-chemical parameters of the lentic and the lotic water bodies along the altitudinal gradient were determined and collected specimens. The total 664 individuals were collected in which five subfamilies of Dytiscidae, 12 genera and 17 species were identified. Pearson’s correlation showed moderately negative correlation between the species diversity and taxon richness based on altitude and pH (p < 0.05). Temperature had moderate positive correlation with species diversity of Dytiscidae. Canonical correspondence analysis (CCA) showed temperature had an effective determining factor for distribution of Dytiscidae. Kruskal Wallis test among different habitats and altitudinal strata showed significant difference in Dytiscids diversity and taxon richness (p < 0.05). The diversity and richness showed a decreasing trend when the altitude increased. The highest diversity was found in marshy area (H = 2.36) and second altitude stratum (800 – 1200 masl) (H = 2.07) in the current study area. Therefore, the best conservation strategy of Dytiscidae could be to protect these areas before they are degraded.

Giant Jurassic dragon lacewing larvae with lacustrine palaeoecology represent the oldest fossil record of larval neuropterans.

Neuropterans seem to be less specious among holometabolans, while they are in fact the relicts of a diverse group from the Mesozoic era. Their early radiation resulted in great family level morphological heterogeneity of extant neuropterans, especially of their larvae. The earliest previously reported fossil larvae of this group were from the Early Cretaceous, where they already showed high taxonomic diversity and an extremely wide range of variations in morphotypes. In this work, the earliest record of the larva of the neuropteran Palaeoneurorthus baii gen. et sp. nov. from the Middle Jurassic Daohugou Beds of China is described. The larvae, which have large and elongated bodies, straight stylets with curved apices, an extremely elongated cervix and an extended anterior lobe of pronotum, are placed in Nevrorthidae. The elongated cervix is probably a specialized adaptation for hunting small organisms. The palaeoenvironment of these larvae indicates that larvae of Nevrorthidae have exhibited stable aquatic ecology since the Middle Jurassic, and underwent a possible shift from lakes to more lotic yet constricted modern mountain rivulet habitats over time.

An Easy-to-Use Histological Technique for Small Biological Samples of Senegalese Sole Larvae

Histological techniques are a traditional and essential tool for adequately comprehending cellular morphology and physiology in several scientific fields, including ecotoxicological studies. Although bioassays generally recommend using small test organisms, based on advantages such as low maintenance costs and the possibility of a higher number of replicates, the histological process of such organisms is still challenging due to the difficulty of handling them. The present study proposes an accessible protocol for performing the histology of a biological sample of 8 mm maximum length and using histopathological biomarkers in Senegal sole larvae for ecotoxicological tests. Eight-day old larvae of Solea senegalensis obtained from breeders’ natural spawns in cultivation conditions were submitted to histological processing by an adjusted protocol comprising fixation, agarose array pre-embedding, dehydration, paraffin embedding, slides’ preparation, and image analysis by light optical microscope coupled to a digital camera. Low-cost and easy-to-use alternatives were applied in the technique execution. The histological steps were detailed, and S. senegalensis morphological features were presented. This can be considered valuable background information for ecotoxicological studies where changes in cell morphology and physiology are expected.

Edaphic diversity of cunaxid mites (Acari: Prostigmata) in different tree formations from northern region of Rio Grande Do Sul State, Brazil

Areas of natural vegetation can favor biodiversity since they have a higher number of native plants and less impact of human activities compared to areas with agricultural crops. Orange and pine forestry stand out among the important monoculture crops for Brazilian agribusiness. In the orange crop, agrochemicals are used to control pests; in pine, there is no need to apply agrochemicals as often, however, biodiversity can be impacted by allelopathic effects of the plant. There are some mite families associated with these environments; among them the cunaxid mites present are associated with both the soil and the litter, feeding on springtails, nematodes and other small organisms. The objective of this study was to evaluate the cunaxid diversity associated with Natural Vegetation (NV), Pine Forestry (PF) and Orange Cultivation (OC) in the municipalities of Mormaço and Soledade, state of Rio Grande do Sul, Brazil. Three litter and soil collections were carried out at 12 random sampling points, in previously demarcated areas within each environment. In total, 330 cunaxids were collected, 57.6% in NV, 32.7% in OC and 9.7% in PF. Among the species found, Coleoscirus tuberculatus Den Heyer, Cunaxa n. sp., Neobonzia n. sp. and Pulaeus quadrisolenidius Castro & Den Heyer were exclusively associated with NV, while Rubroscirus sp. only with OF and Dactiloscirus sp. with OC. The most abundant species was Neocunaxoides ovatus Lin, Zhang & Ji, with 130 specimens and the rarest was Neobonzia n. sp., with only one specimen.

222 nm far-UVC efficiently introduces nerve damage in Caenorhabditis elegans.

Far-ultraviolet radiation C light (far-UVC; 222 nm wavelength) has received attention as a safer light for killing pathogenic bacteria and viruses, as no or little DNA damage is observed after irradiation in mammalian skin models. Far-UVC does not penetrate deeply into tissues; therefore, it cannot reach the underlying critical basal cells. However, it was unclear whether far-UVC (222-UVC) irradiation could cause more biological damage at shallower depths than the 254 nm UVC irradiation (254-UVC), which penetrates more deeply. This study investigated the biological effects of 222- and 254-UVC on the small and transparent model organism Caenorhabditis elegans. At the same energy level of irradiation, 222-UVC introduced slightly less cyclobutane pyrimidine dimer damage to naked DNA in solution than 254-UVC. The survival of eggs laid during 0-4 h after irradiation showed a marked decrease with 254-UVC but not 222-UVC. In addition, defect of chromosomal condensation was observed in a full-grown oocyte by 254-UVC irradiation. In contrast, 222-UVC had a significant effect on the loss of motility of C. elegans. The sensory nervous system, which includes dopamine CEP and PVD neurons on the body surface, was severely damaged by 222-UVC, but not by the same dose of 254-UVC. Interestingly, increasing 254-UVC irradiation by about 10-fold causes similar damage to CEP neurons. These results suggest that 222-UVC is less penetrating, so energy transfer occurs more effectively in tissues near the surface, causing more severe damage than 254-UVC.

What Lies Inside a Dead Coral: Diversity of Reef-Associated Cryptic Crustacean (Crabs: Anomura and Brachyura) from Different Habitat Characteristics in Tidung Islands, Indonesia

Highlight Research The very first attempt to investigated and revealing biodiversity of crustacean crab in coral reef ecosystem at Tidung Island, Indonesia Conservation area (Tidung Kecil) has more abundant crab species than tourism area (Tidung Besar). A microhabitat that suffers anthropogenic pressure may alter the composition of crustacean biodiversity, especially in crab group. Different characteristics and complexity of coral habitat affect the dynamics of cryptic crustacean communities Abstract Recent studies have been widely carried out on the important role and ecological function of coral reefs. However, little attention has been given to small and cryptic crustaceans organisms living within different microhabitat in dead corals. This study aimed to reveal the diversity of crustaceans that inhabit dead corals in Tidung Islands, Indonesia. A total of 134 individuals from 41 species in 13 families were recorded within eight dead corals taken from two different sites. Furthermore, the species identified from Tidung Kecil were significantly different and more diverse than Tidung Besar. It was suggested that differences in anthropogenic pressure between Tidung Besar and Kecil might have an important role in the spread of crab crustaceans’ organisms. Xanthidae from infraorder Brachyura were observed to be the most dominant family, while Galatheidae and Porcellanidae from infraorder Anomura spread almost equally in both sites. Additionally, Psaumis cavipes and Chlorodiella nigra were species with the largest contribution of crab crustaceans’ communities in the death of coral’s ecosystem in the Tidung Islands. This result indicated that dead corals might play a key role in supporting and providing a habitat for crustacean cryptic.

Seasonal difference in soil health indicators mediating multidiversity-multifunctionality relationship depends on body size of soil organisms: Evidence from rubber plantation agroforestry system

Soil health is the foundation for the maintenance of ecosystem stability and multifunctionality. It is necessary to identify the key indicators of soil health that indicate ecosystem multifunctionality against anthropogenic disturbances such as land use change. Many studies have shown the pivotal role of soil biodiversity in maintaining ecosystem multifunctionality. However, the key role of soil multidiversity (including different body size soil organisms across multitrophic levels) in affecting ecosystem functions is poorly understood. We have implemented a multitrophic perspective to study soil multidiversity by including bacteria, fungi, nematodes (5 feeding types), and arthropods (thripidae, poduridae, and others). Here we show that a multitrophic approach for soil biodiversity assessment is important to highlight trophic interactions and their subsequent effects on the soil multidiversity-ecosystem multifunctionality (MEF) relationship. We postulate that soil multidiversity promotes soil health and thus drives the MEF relationship. We assessed soil multidiversity, 11 variables for ecosystem functions, and ecological network stability (reflected by co-occurrence network patterns) in rubber plantations differing in land-use intensity represented by monoculture (MRP), high (RHD) and low (RLD) diversity of other plant species. We also included tropical rainforest (TRF) as a reference system to compare our results. Results showed that soil multidiversity, multifunctionality, and soil network stability significantly improved in RHD as compared to MRP. Soil multidiversity rather than single diversity component had strong positive effects on multifunctionality. More specifically, we found that the relationship between soil multidiversity and multifunctionality was seasonally dependent on the soil attributes and the body size of soil organisms. We observed a negative correlation between large body size organisms and soil nutrients content in the dry season while a positive correlation between small body size soil organisms and enzymatic activities in the rain season. Particularly, we emphasized the role of soil multidiversity in enhancing ecosystem multifunctionality and stability via its prominent impacts on soil health. Our study elucidates that accurate identification of soil health indicators is an important approach to imply remedial management strategies to maintain soil health and MEF relationship in managed ecosystems such as rubber plantations.

Rotifers of Inter-Forest Springs

Springs are often considered as “hotspots” of aquatic biodiversity. However, small organisms, such as rotifers, substantially contribute to secondary production, but they are rarely investigated in springs. We surveyed the rotifer fauna of 47 springs in the Knyszyn Forest (north-eastern Poland) in summer and autumn 2014–2015. We hypothesized that stream communities of Rotifera may be specific to this habitat. Rotifer samples were taken using a Plexiglas tube in the spring current. Concurrently, water temperature, pH, conductivity, water redox potential and phosphorus and nitrogen concentrations were determined. The springs did not differ statistically in water quality and were stable regarding their temperature and conductivity. Rotifer densities and mean number of monogonont species were very low both in summer and autumn. Nevertheless, the total number of species recorded in all springs was relatively high and accounted for 101 in total. Although strongly differentiated, the rotifer fauna contained a set of several species common to most of the springs. Most of the recorded species are eurytopic and widely spread in water ecosystems. Only the concentration of magnesium and chloride ions had an impact on Monogononta numbers.

Lab and field evaluation of tagging methods for the use of acoustic telemetry to observe sea urchin movement behaviour at ecologically relevant spatio-temporal scales

BackgroundAcoustic telemetry allows detailed observations of the movement behaviour of many species and as tags get smaller, smaller organisms may be tagged. The number of studies using acoustic telemetry to evaluate marine invertebrate movement is growing, but novel attachment methods include unknowns about the effects of tagging procedures on individual survival and behaviour. This study compared methods of tag attachment on green sea urchins (Strongylocentrotus droebachiensis) to determine the feasibility of using acoustic transmitters to track echinoid movement. Four tagging methods were compared in the lab and tag retention, urchin condition, and survival analysed. Two tagging methods (Dyneema® fishing line and T-bar tags) were evaluated in the field using an existing acoustic telemetry array. Urchins were tagged and the study area revisited one week and 2 months post-release by scuba divers to estimate movement and tag retention.ResultsThe best methods in the lab, with high tag retention, survival, and minimal effects on urchin condition, were fishing line methods. T-bar tags, although showing high tag retention, caused significant mortality and had deleterious long-term effects on urchin condition and behaviour. After 2 months in the field, as in the lab, fishing line was a more effective tagging method. Urchins tagged with fishing line showed increased estimates of space occupancy compared to T-bar-tagged urchins and a single fishing-line tagged individual was found by divers in good health after 80 days. Combined, these laboratory and field results demonstrate the feasibility of using acoustic telemetry to observe urchin movement.ConclusionsResults strongly suggest that surgical attachment methods that minimize injuries at the attachment site should be prioritized for echinoid tagging studies. Together, lab and field tests indicate that acoustic telemetry is a promising method to examine marine echinoid movement over ecologically relevant spatial and temporal scales.

Motion in Stratified Fluids

Density stratification due to temperature or salinity variations greatly influences the flow around and the sedimentation of objects such as particles, drops, bubbles, and small organisms in the atmosphere, oceans, and lakes. Density stratification hampers the vertical flow and substantially affects the sedimentation of an isolated object, the hydrodynamic interactions between a pair of objects, and the collective behavior of suspensions in various ways, depending on the relative magnitude of stratification, inertia (advection), and viscous (diffusion) effects. This review discusses these effects and their hydrodynamic mechanisms in some commonly observed fluid–particle transport phenomena in oceans and the atmosphere. Physical understanding of these mechanisms can help us better model these phenomena and, hence, predict their geophysical, engineering, ecological, and environmental implications.

Individual identification of inbred medaka based on characteristic melanophore spot patterns on the head

With disease progression, individual differences appear, even in an animal disease model with genetic homogeneity. Therefore, non-invasive long term observation and individual identification is desirable for late-onset diseases. To this end, the natural markings used in ecological studies are preferable to the external invasive markings used in animal husbandry and fisheries management. Here, we propose using the distribution pattern of melanophore spots on the head of an inbred strain of medaka, a small fish model organism with monotonous pigmentation, as biometric identifier. Long term and variation analyses show different patterns whose characteristics can be attributed to individual animals. These findings were also valid in a non-inbred medaka strain and will help individual follow-up of late-onset disease medaka models for the elucidation of the pathogenesis and drug discovery.

Assessment of a new olfactometer for study of sensory ecology in small aquatic organisms

AbstractAll aquatic organisms rely on chemical stimuli at some point during their life cycles. These stimuli are typically associated with essential functions such as food‐, mate‐, or habitat‐finding, or predator avoidance. Historically, research on sensory ecology and behavior of aquatic organisms has been conducted using two‐channel choice flumes, which have many limitations when utilized on small organisms. Here, we describe functional features and results of pilot tests of an aquatic olfactometer, adapted from olfactometers used in studies on terrestrial arthropods, which eliminates these limitations. The initial implementation of this olfactometer is described. The structural integrity, hydrodynamics, and basic function of the olfactometer were tested and verified. The ability to clearly record the movements of a small organism within was also tested. Our experiments verify that the flow rate of water within the choice arena was accurate, water behaved as theorized in prior modeling, and chemical concentrations within each “zone” were distributed as expected based on computer simulations. We further show that video data could be obtained and analyzed using Ethovision XT to provide large amounts of raw data, including position, velocity, and acceleration, which can be used to investigate many potential questions associated with behavior. This olfactometer has the potential to become the new standard for research on chemotaxis and chemical ecology of small aquatic organisms.

Evaluating Dermal Bone as a Novel Source of Endocrine Information in Ninespine and Threespine Stickleback Fish.

Monitoring the physiology of small aquatic and marine teleost fish presents challenges. Blood samples, often the first choice for endocrinologists, can be difficult or even impossible to obtain and alternative matrices currently used for hormone analyses do not occur in fishes (e.g., hair, feathers etc.) or are not easily collected from small aquatic organisms (e.g., urine and feces). Some teleosts, however, have enlarged bony dermal elements that possibly accumulate and store steroid hormones in physiological relevant concentrations. Both threespine stickleback (Gasterosteus aculeatus) and ninespine stickleback (Pungitius pungitius) have a series of external, lateral bony plates, dorsal spines, and a pair of pelvic spines attached to the pelvic girdle. We investigated if cortisol, the primary circulating glucocorticoid in teleosts, could be extracted from stickleback dermal bone and quantified using a commercially available enzyme immunoassay (EIA). We successfully validated a cortisol EIA for dermal bone extracts, determined that cortisol was detectable in both species, and found that dermal bone cortisol levels significantly correlated with cortisol levels in whole body homogenate. Ninespine stickleback had significantly higher dermal bone cortisol concentrations than threespine stickleback and female threespine stickleback tended to have over twice the mean dermal bone cortisol concentration than males. Because both stickleback species are widely used for ecotoxicological studies, using dermal bone as a source of endocrine information, while leaving the body for contaminant, genomic, histological, and stable isotope analyses, could be a powerful and parsimonious tool. Further investigation and physiological validations are necessary to fully understand the utility of this new sample matrix.

Karakteristik Burung dalam Perspektif Al-Qur’an dan Sains

Birds are the animals most frequently mentioned in the Qur’an. However, the birds in the Qur’an have never been studied using a comprehensive scientific approach. This research is expected to be able to add insight and knowledge to Indonesian scholars about the integration of the theme of birds in the Qur’an and science. This study uses a thematic method based on library research by tracing verses about birds in the Qur’an. These verses are then studied using the method of scientific exegesis in which the sources are contemporary commentary books. Then these verses can be integrated with science. Based on the research conducted by the author, the characteristics of birds in the Qur’an can be detailed as follows: First; movement of birds in the air. For thousands of years before, the Qur’an has explained the patterns of bird movement that have been revealed by science today. Second; the behavior of crows and their benefits to humans. Crows have intelligence that is beneficial to human life. Third; nutritional content in salwa birds. The nutritional value of salwa birds can nourish the human body. Fourth; the behavior of the birds bombarding Abraha’s troops. Based on the opinion of contemporary scholars, these birds are interpreted as small organisms that cause various diseases. This organism then develops into a lethal weapon of mass murder, which is popularly known as bioterrorism.

Ontogenetic shifts in feeding habits of orangemouth weakfish (Cynoscion xanthulus): From estuarine benthic feeder to marine nektivore top predator

AbstractOrangemouth weakfish is a highly important commercial and game fish species in the Tropical Eastern Pacific. However, studies assessing changes in its trophic ecology relevant to size, habitat (estuarine or marine), sex, and season are non‐existent. We assessed its feeding habits and trophic position (TP) according to the aforementioned factors. Its dietary breadth was composed of 33 types of prey. The feeding habits and isotopic values (δ15N and δ13C) registered differences between sizes and habitat, indicating ontogenetic changes in habitat as well as TP, as small organisms (TP 3.1) inhabited the estuarine area, feeding on benthic and demersal organisms, whilst large individuals (TP 4.1) were found in the marine environment, preying on nektonic fauna. No differences were found according to sex or season. The isotopic niche showed that the different sizes of this species are generalist consumers with a clear separation between them and between habitats, as estuarine juvenile and preadult organisms have a larger isotopic niche than adult marine organisms, being an opportunist tertiary estuarine consumers during their early stages, and a top marine predator during the adult phase.

Noninvasive micro-test technology: monitoring ion and molecular flow in plants.

Noninvasive micro-test technology (NMT) is a novel technology to investigate the influx and/or efflux rate, direction, and concentration of selected ions and molecules in a microenvironment surrounding living cells or intact organisms. NMT measures and records the spatial electric potential differences in liquid media-surrounded living cells, tissues, and small organisms. Measurements are taken by a vibrating selective and/or specific flux sensor, combined with computerized algorithm to reveal ionic or molecular exchanges in the microenvironment with high sensitivity.