Lower Invertebrates Research Articles

Forecasting sea otter recolonization: insights from isotopic analysis of modern and zooarchaeological populations.

Retrospective datasets offer essential context for conservation by revealing species' ecological roles before industrial-era human impacts. We analysed isotopic compositions of pre-industrial and modern sea otters (Enhydra lutris) to reconstruct pre-extirpation ecology and offer insights for management. Our study focuses on southeast Alaska (SEAK), where sea otters are recolonizing, and northern Oregon, where translocations are being considered. We measured bulk bone collagen δ13C and δ15N values and essential amino acid δ13C values of extirpated sea otters from archaeological contexts, and bulk isotopic values from vibrissae of modern SEAK sea otters. We compare these results with published isotopic data of potential prey and additional archaeological datasets. In SEAK, our data show pre-industrial sea otter populations consumed infaunal bivalves and used soft-sediment (33%) and kelp forest habitats (67%), with sub-regional variation. We anticipate current populations will expand into this historical niche, and conflict with regional traditional/subsistence bivalve fisheries will persist. In northern Oregon, isotopic data from extirpated sea otters indicate past consumption of low trophic level invertebrates and a stronger reliance on kelp forests (88%) rather than soft-sediment habitats, highlighting the importance of kelp forests for future translocations. Our work exemplifies the value of historical ecology in informing conservation strategies for recovering species.

Does Differential Habitat Selection Facilitate Coexistence Between Badgers and Hedgehogs?

Predicting the spatial and temporal responses of species exhibiting intraguild predation (IGP) relationships is difficult due to variation in potential interactions and environmental context. Eurasian badgers (Meles meles) are intraguild predators of European hedgehogs (Erinaceus europaeus) and are implicated in their population decline via both direct predation and competition for shared food resources. Previous studies have shown spatial separation between these species and attributed this to hedgehogs experiencing a 'landscape of fear', but little is known about the potential role of differential habitat use. We estimated the density and occupancy of both species at 22 rural study sites in England and Wales, to explore whether food availability, habitat or the presence of badgers, explained hedgehog distributions. Hedgehog density varied significantly across major rural land uses, whereas badger density did not. Although both species coexisted at a regional (1 km2) scale, occupancy modelling showed spatial segregation at a finer (individual camera trap) scale, associated with differential habitat use. In contrast to badgers, hedgehogs were recorded near buildings, and in areas supporting lower invertebrate biomass. This is in agreement with IGP theory, whereby IG-prey may occupy suboptimal habitat to avoid predation; however, hedgehog habitat use did not vary relative to the presence of badgers. Badger and hedgehog temporal activity showed no evidence of separation. Although these findings are consistent with hedgehogs avoiding badgers via a landscape of fear, they are also indicative of differential habitat use, highlighting the need for more holistic studies considering variation in habitat selection and food availability when investigating intraguild relationships. Future studies exploring alternative hypotheses for urban habitat selection by hedgehogs are needed to better understand how possible spatial niche partitioning may support their coexistence with badgers in some areas.

Exosome-mediated viral nucleic acid presentation in a crustacean expounds innate immunity from a novel perspective.

Our study revealed that the components of DNA virus could be packaged and transmitted through the exosomes of lower invertebrates, which strongly demonstrated the diversity of exosome-mediated viral immunity and its universality in animals. Furthermore, we elucidated the mechanism of apoptotic signal transduction between cells from the perspective of exosomes and revealed a novel strategy for the host to cope with viral infection.

Behavioural, Teratogenic and Genotoxic Effects of Antibacterial Compounds, Triclocarban and Triclosan, in Hydra vulgaris.

Triclocarban (TCC) and triclosan (TCS) are antibacterial compounds used in household, veterinary, industrial and personal care products, which are known to be environmental pollutants and also toxic to organisms. The toxicological effects of these antibacterial chemicals on higher organisms have been studied in detail. But in lower invertebrates like hydra, it is still rare and yet to be explored. In this study, the toxicological effects of these two antibacterial compounds in Hydra vulgaris was performed to clearly understand the organismal, developmental, molecular and behavioural changes. Both TCC and TCS are toxic with respective LC50 values of 0.09 and 0.25 mg/L, whereas TCC is comparatively more toxic than TCS. The structural damage of battery cell complexes (BCCs) on the tentacles was observed and ultimately made prey capturing difficult. It was evident that TCC and TCS exposure caused developmental toxicity by affecting reproduction and regeneration in H. vulgaris at higher sublethal doses (0.045 and 0.125 mg/L, respectively). TCC and TCS also caused DNA damage resulting in apoptosis. This study further reveals that these two antibacterial compounds are teratogenic and genotoxic in the organisms.

Living under Arctic kelp forests: linking soft-bottom communities to kelp cover in the Canadian Arctic

Kelp forests are dominant habitats along Canadian Arctic coastlines. While their extent and productivity are expected to change dramatically due to global warming, their role in supporting Arctic coastal biodiversity remains poorly explored. Leveraging an extensive data set encompassing core samples, video transects, and environmental data, this study explores the patterns and drivers of benthic diversity, particularly focusing on kelp cover, across 4 Eastern Canadian Arctic regions. We show that the widespread soft bottoms in many subtidal coastal Arctic areas are associated with high densities of the kelp Saccharina latissima, often growing in mixed stands with Laminaria solidungula and Alaria esculenta. These kelps enhance the diversity of invertebrate communities thriving in the sediment below, increasing densities in specific groups and promoting subsurface feeding activity. Interregional comparisons indicate that high turbidity conditions typically lead to low macroalgal cover and low invertebrate richness, whereas extensive sea ice cover can favor high macroalgal abundance and unique diverse communities. Conditions of intermediate open-water duration and high water clarity support tall kelp forests, hosting approximately 70% of local rare taxa. Based on these surveys, we provide a list of Arctic invertebrate taxa according to their level of selectivity for kelp forests as habitats. Despite variation among regions, kelp forests enhance biodiversity and drive unique benthic communities in the Canadian Arctic. Due to their ecological significance and potential vulnerability, we recommend efforts to integrate kelp forests into marine protected areas and minimize human-induced damaging activities within or near these habitats.

Changes of bacterial communities and bile acid metabolism reveal the potential “intestine-hepatopancreas axis” in shrimp

The interaction between the gut and the liver plays a significant role in individual health and diseases. Mounting evidence supports that bile acids are important metabolites in the bidirectional communication between the gut and the liver. Most of the current studies on the “gut-liver axis” have focused on higher vertebrates, however, few was reported on lower invertebrates such as shrimp with an open circulatory system. Here, microbiomic and metabolomic analyses were conducted to investigate the bacterial composition and bile acid metabolism in intestine, hemolymph and hepatopancreas of Penaeus vannamei fed diets supplemented with octanoic acid and oleic acid. After six days of feeding, the bacterial composition in intestine, hemolymph and hepatopancreas changed at different stages, with significant increases in the relative abundance of several genera such as Pseudomonas and Rheinheimera in intestine and hepatopancreas. Notably, there was a more similar bacterial composition in intestine and hepatopancreas at the genus level, which indicated the close communication between shrimp intestine and hepatopancreas. Meanwhile, higher content of some bile acids such as lithocholic acid (LCA) and α-muricholic acid (α-MCA) in intestine and lower content of some bile acids such as taurohyocholic acids (THCA) and isolithocholic acid (IsoLCA) in hepatopancreas were detected. Furthermore, Spearman correlation analysis revealed a significant correlation between bacterial composition and bile acid metabolism in intestine and hepatopancreas. The microbial source tracking analysis showed that there was a high proportion of intestine and hepatopancreas bacterial community as the source of each other. Collectively, these results showed a strong crosstalk between shrimp intestine and hepatopancreas, which suggests a unique potential “intestine-hepatopancreas axis” in lower invertebrate shrimp with an open circulatory system. Our finding contributed to the understanding of the interplay between shrimp intestine and hepatopancreas in the view of microecology and provided new ideas for shrimp farming and disease control.

Moonlight-driven biological choruses in Hawaiian coral reefs.

Sounds from fish and invertebrates in coral reefs can create persistent cacophonies that can be recorded for ecosystem monitoring, including during nighttime hours where visual surveys are typically not feasible. Here we use soundscape measurements in Hawaii to demonstrate that multiple coral reef communities are rapidly responsive to shifts in nighttime ambient light, with sustained changes in biological sound between moonrise and moonset. High frequency pulse train sounds from fish (0.5-1.5 kHz) are found to increase during moonlight hours, while low frequency fish vocalizations (0.1-0.3 kHz) and invertebrate sounds (2-20 kHz) are found to decrease during moonlight hours. These discoveries suggest that the rising and setting of the moon triggers regular shifts in coral reef ecosystem interactions. Future acoustic monitoring of reef health may be improved by comparing soundscapes during moonlight and non-moonlight hours, which may provide early indicators of shifts in the relative abundance of separate reef communities.

Glaciers, snow, and rain: Water source influences invertebrate community structure and secondary production across a hydrologically diverse subarctic landscape

AbstractThe melting cryosphere adds heterogeneity to the abiotic and biotic characteristics of many high latitude and montane rivers. However, climate change threatens the cryosphere's persistence in many regions. While existing research has explored the impacts of cryospheric loss on the diversity and structure of freshwater communities, implications for functional traits of communities, such as production of aquatic invertebrates, remain unresolved. Here, we quantified aquatic invertebrate community structure and secondary production in southeast Alaska (USA) streams that represent a meltwater to non‐meltwater gradient, including streams fed primarily by: (1) glacier‐melt, (2) snowmelt, (3) rainfall, and (4) a combination of these sources. We found alpha diversity was highest in the snow‐fed stream and lowest in the glacier‐fed stream. Annual secondary production was also lowest in the glacier‐fed stream (0.56 g ash‐free dry mass m−2), but 2–5 times higher in the other stream types primarily due to greater production of shared taxa that were found in all streams. However, despite low invertebrate diversity and productivity, the glacier‐fed stream hosted distinct species assemblages associated with unique cycles of stream flow, water temperature, turbidity, and nutrient concentrations, which contributed to higher beta diversity between streams. Our findings suggest that the loss of glacier‐melt contributions to rivers may result in increased freshwater invertebrate production but reduced beta diversity, which could have implications for community stability and the capacity of landscapes to support higher‐level consumers, including fishes.

Invasion of farmland hedgerows by non-native small mammals is associated with lower soil surface invertebrate diversity, abundance, body size and biomass

Small mammals in farmland hedgerows feed on soil surface invertebrates with non-native invasive species potentially affecting prey species and populations. We investigated terrestrial invertebrates using pitfall traps and leaf litter samples across four zones of invasion in Ireland: (1) native species only (wood mouse Apodemus sylvaticus and pygmy shrew Sorex minutus), (2) natives plus the non-native bank vole (Myodes glareolus), (3) natives plus the non-native greater white-toothed shrew (Crocidura russula) and (4) natives plus both. After accounting for regional and local environmental variation, small mammal invasion was associated with lower invertebrate species richness (9–39% lower than uninvaded zones), reduced abundance (18–56% lower), shorter arthropod body length (24–52% shorter) and lower arthropod biomass (63–89% lower). Negative effects were observed on a wide range of disparate functional groups spanning phytophagous, detritivorus, zoophagous and omnivorous taxa including: the Staphylinidae, Carabidae and Coleoptera larvae, Isopoda, Diplopoda, Diptera, Hymenoptera, Pulmonata and Acari. The greater white-toothed shrew had greater negative effects than the bank vole with presence of both having greater effects than either alone though the majority of their combined effects were largely attributable to the former. The bank vole may mitigate some of the negative effects of the greater white-toothed shrew on invertebrate abundance perhaps indicating of some form of trophic interaction. Predation of detritivores and large invertebrate predators may impact farmland ecosystem service delivery i.e. nutrient cycling and pest biocontrol. Hedgerow biodiversity loss may induce indirect trophic cascades negatively impacting other taxa including farmland birds.

CircMETTL7A enhances Toll pathway-mediated innate immunity and antibacterial activity in V. splendidus-challenged Apostichopus japonicus by reducing miR-137 function

Circular RNA (circRNA) is an endogenous noncoding RNA subgroup with covalently closed rings that are widely expressed. Over the past few years, growing data confirmed that circRNAs function as significant regulators involved in numerous biological processes. However, the biological functions and underlying immune mechanism of circRNAs upon bacterial infection in lower invertebrates are further unclarified. Here, we discovered a circRNA derived from the methyltransferase-like protein 7A (METTL7A) gene, named circMETTL7A, which is closely bound up with an antibacterial response in Apostichopus japonicus. The results indicated that circMETTL7A displayed a significant ability in host antibacterial immunity and inhibition of the pathogenic Vibrio splendidus invasion. Our results also identified a microRNA, miR-137, which could suppress the host antibacterial responses and enhance V. splendidus invasion by targeting A. japonicus Toll (AjToll). Moreover, we detected that the antibacterial effects and AjToll protein levels inhibited due to circMETTL7A knockdown can be reversed by supplementing with miR-137 inhibitors. Mechanically, our results presented that circMETTL7A acts as a ceRNA of AjToll by sponging miR-137, leading to initiation of the NF-κB pathway, and thus boosting the antibacterial immunity in A. japonicus. Our results provide new insights for understanding circRNA functions upon bacterial infection in echinoderms and enrich the data for disease prevention in A. japonicus breeding.

Diets of invasive channel catfish are subsidized by invasive riparian trees

AbstractRussian olive (Elaeagnus angustifolia) is an invasive, fruit‐bearing riparian tree that dominates riparian zones of the San Juan River in the southwestern United States. Previous research in this river suggests olive fruit is common in diets of invasive channel catfish (Ictalurus punctatus), but its energetic importance is unknown (i.e. critical for catfish fitness vs. incidental consumption). We assessed Russian olive consumption in channel catfish diets bimonthly for 1 year, hypothesizing that olive consumption would be greatest during periods of high olive availability and low benthic aquatic invertebrate availability. We found that catfish consumed olive fruit throughout the year and that olive comprised up to 44% of total stomach contents by mass, with peaks in spring and fall. Regression models revealed the presence and mass of olive fruit in catfish stomachs were positively associated with catfish total length, with a significant interaction between water temperature and river discharge. Catfish were more likely to consume olive fruit during higher flows, regardless of temperature and at low discharge with higher temperature. Contrary to our hypothesis, neither olive nor benthic invertebrate availability were associated with olive presence in channel catfish diets. Nutrition analysis indicated that olive alone was a low‐quality diet item but has the potential to provide a reliable energy source. We used seasonal data to estimate the energetic contribution of olive fruit to catfish populations using a bioenergetic model, which estimated that olive fruit accounted for 35.6% of energy (Joules) consumed by catfish populations and satisfied 38% of their metabolic demand. Our results suggest that Russian olive fruit is a significant subsidy to channel catfish in the San Juan River. However, more research is needed to determine the indirect effects of this interaction on native fishes and ecosystem function.

Grasslands of cleared woodlands have lower invertebrate diversity and different assemblages to remnant woodlands in grazed landscapes of eastern Australia

Clearing of woodlands is used by graziers to promote pasture production, even though understanding of impacts of clearing on native fauna is lacking. We evaluate impacts of clearing on biodiversity by comparing invertebrates associated with ground-layer vegetation of cleared woodlands (grasslands) to that of nearby uncleared woodlands. Two replicates of grasslands consisting of pastures dominated by introduced grasses were compared with two woodlands at each of four locations. The adjacent riparian forest to each grassland and woodland site allowed evaluation of the effect of woodland clearing on the adjacent riparian zone. All habitats were grazed. Invertebrates of ground-layer vegetation were sampled using three suction subsamples of 1m2 at each site. Grasslands had significantly lower order richness and abundance of herbivores, pollinators and macroinvertebrates (food for birds) than the woodlands, whereas the riparian forests closely resembled each other in all metrics. Invertebrate assemblages of grasslands also differed significantly from those of the woodlands. BEST analysis showed that groundcover and leaf-litter percentage cover correlated strongest with invertebrate composition. This study has demonstrated that grazing management relying on clearing of fertile grassy woodlands of the rangelands of Central Queensland alters invertebrate diversity and assemblage. Thus, tree clearing not only leads to biodiversity losses in the canopy layer, but also in the ground-layer vegetation.Implications for insect conservationPastoralists have the capacity to improve outcomes for invertebrate biodiversity by maintaining groundcover (ground-layer vegetation and litter cover) above 80%, by encouraging native pastures over introduced species such as Buffel Grass and by retaining native woodlands.

Impact of land use on water quality and invertebrate assemblages in Indonesian streams

Catchment land use of streams can cause deterioration of the stream ecosystems. Studies on the impact of land use on water quality and invertebrate assemblages in tropical streams are currently less common than studies in temperate regions. In the current study, we conducted a field survey on stream invertebrates and habitat characteristics in 23 streams with different land use conditions in Yogyakarta Province, Java Island, Indonesia. Relationships among catchment characteristics, habitat characteristics, and invertebrate assemblages were analyzed to elucidate the importance of land use and water quality in determining invertebrate assemblages. The analyses, using generalized linear models, showed that the relative area of urban land use of the catchment was strongly and positively related to the nutrient concentration of stream water and negatively related to the taxonomic richness of whole invertebrate assemblages and intolerant taxa. Furthermore, the richness metrics were low in streams with high nutrient concentrations, particularly PO4-P. The biplot of nonmetric multidimensional scaling showed that there was a gradient in community structure along the tolerance to water pollution that occurred in urban streams. These results collectively suggest that urban land use, not agricultural use, seemed to be a predominant factor causing nutrient enrichment in stream water and low invertebrate diversity through the exclusion of intolerant taxa in Indonesian streams whose catchments are exposed to rapid urbanization. We suggest that the impact of agricultural wastewater on stream water quality is concealed by the strong impact of urbanization when we consider that farming methods are, in general, not intensive in Indonesia, and that advanced wastewater treatment systems have not been widely introduced. Our results strongly support the development of sewage treatment as an effective solution for restoring tropical stream ecosystems.

The m6A Reader YTHDF2 Modulates Antiviral and Antibacterial Activity by Suppressing METTL3 Methylation-Modified STING in Fish.

At present, N6-methyladenosine (m6A) modification has been proven to participate in a wide range of gene expression regulation, such as stability, translation, splicing, and output, among others, which has attracted much attention. Unlike mammals, however, the role of m6A in innate immunity of lower invertebrates has not yet been studied. In this study, we found that the total m6A level of Miichthys miiuy increased during Siniperca chuatsi rhabdovirus and Vibrio anguillarum infection, suggesting that m6A may play an important role in the immune process against pathogens in fish. In addition, our study shows that stimulator of IFN genes (STING) plays a dual immune function against viruses and bacteria in fish, and through degrading STING by identifying its m6A methylation site modified by methyltransferase-like 3 (METTL3), YTH domain family 2 (YTHDF2) can weaken the IRF3 and NF-κB-driven signaling pathway, thus weakening the innate immunity and promoting the infection of Siniperca chuatsi rhabdovirus and V. anguillarum to the M. miiuy. Although there have been reports on m6A modification of STING in mammals, it is still unclear whether there is also m6A modification in lower vertebrates, especially in fish. Therefore, our study provides a reference for filling the gap of m6A modification between fish and mammals.

CircRNA1149 from Apostichopus japonicus suppresses coelomocyte apoptosis act as miR-92a sponge to regulate Bax expression in response to Vibrio splendidus infection

Circular RNAs (circRNAs) are a class of widespread and diverse covalently closed circular endogenous RNAs that play pivotal roles in mediating immune regulation in mammals. However, the function and regulatory mechanisms of circRNAs in lower invertebrates are still far unidentified. In this study, we discovered a circRNA derived from AJAPscaffold1149: 133758|203,802 of Apostichopus japonicus genome, termed circRNA1149 (circ1149), that is closely related to the occurrence of skin ulcer syndrome (SUS) in sea cucumber A. japonicus. Results revealed that circ1149 plays a significant role in pathogen Vibrio splendidus-induced coelomocyte apoptosis in sea cucumbers. Our study also found a microRNA miR-92a, which could promote coelomocyte apoptosis caused by V. splendidus via targeting Bcl-2-associated X protein (Bax). And, Bax is the first identified pro-apoptotic member of the Bcl-2 protein family. Moreover, we detected that the increased coelomocyte apoptosis level and Bax protein level by circ1149 silencing in response to pathogen infection could be partly recovered by miR-92a inhibitors in vivo and in vitro. Our data indicated that circ1149 functions as a competing endogenous RNA (ceRNA) of Bax by competing for adsorbing miR-92a, thereby suppressing the coelomocyte apoptosis levels induced by V. splendidus. The overall results of this study suggested that circ1149 plays a crucial role in regulating the innate immune response of sea cucumbers, and provides a new insight for understanding the functions of circRNAs in lower invertebrates in response to bacterial infection.

Plant mating system dynamics in restoration: a comparison of restoration and remnant populations ofHakea laurina(Proteaceae)

Ecological restoration is addressing the challenge of biodiversity conservation in landscapes where native vegetation has been extensively cleared. Reestablishing ecological interactions that support self‐sustainable populations plays an essential role in restoration efforts. For animal‐pollinated plant species, comparing mating system dynamics within restoration populations with natural remnant populations can inform the progress of restoration activities. We assessed mating system parameters, seed weight, invertebrate floral visitors, and genetic diversity for two restoration populations and two native reference remnant populations of the animal‐pollinated, woody shrub/tree,Hakea laurina(Proteaceae) in the Southwest Australian Floristic Region. There was no difference in outcrossing rates between the two sites (restoration and reference populations combined) or treatments (sites combined). However, one restoration population showed significantly lower outcrossing that was correlated with reduced seed weight, greater inbreeding, and significantly lower invertebrate richness and abundance compared to its nearby remnant population. In contrast, in the other restoration population, all measures were comparable to the reference remnant population. Local genetic diversity available in remnant populations was captured in both restoration populations. Limitations to pollinator services may be affecting mating patterns and potentially population fitness, in a younger restoration population with reduced proximity to remnant vegetation, which has a tall coplanted overstorey species and spatially aggregated individuals. We highlight these aspects of restoration populations as important areas of ongoing research that will impact the reestablishment of ecological interactions, and the assessment of mating system dynamics as a valuable tool to inform the current progress of restoration activities.

Metabolism of the aquatic pollutant diclofenac in the Lymnaea stagnalis freshwater gastropod.

The metabolism of organic contaminants in Lymnaea stagnalis freshwater gastropod remains unknown. Yet, pharmaceuticals-like the NSAID diclofenac-are continuously released in the aquatic environment, thereby representing a risk to aquatic organisms. In addition, lower invertebrates may be affected by this pollution since they are likely to bioaccumulate contaminants. The metabolism of pharmaceuticals in L. stagnalis requires further investigation to understand their detoxification mechanisms and characterized the risk posed by contaminant exposure in this species. In this study, a non-targeted strategy using liquid chromatography combined with high-resolution mass spectrometry was applied to highlight metabolites formed in L. stagnalis freshwater snails exposed to 300µg/L diclofenac for 3 and 7days. Nineteen metabolites were revealed by this approach, 12 of which were observed for the first time in an aquatic organism exposed to diclofenac. Phase I metabolism involved hydroxylation, with detection of 3'-, 4'-, and 5-hydroxydiclofenac and three dihydroxylated metabolites, as well as cyclization, oxidative decarboxylation, and dehydrogenation, while phase II metabolism consisted of glucose and sulfate conjugation. Among these reactions, the two main DCF detoxification pathways detected in L. stagnalis were hydroxylation (phase I) and glucosidation (phase II).

The occurrence and feeding of a critically endangered shark species, Oxynotus centrina in the Sea of Marmara.

The angular roughshark, Oxynotus centrina (Linnaeus, 1758), is a rarely encountered deep-sea demersal shark species. It is listed as "Critically Endangered" in the IUCN's regional assessment for the Mediterranean. Like other sharks and rays, the angular roughshark is subject to by-catch in demersal trawl and longline fisheries. This study contributes new knowledge on (a) its occurrence, size and sex information; and (b) its feeding ecology in the Sea of Marmara. Data were collected on total length (TL), total weight (TW) and sex from unpublished research survey reports performed intermittently from 1994 to 2020. According to the data, O. centrina was mainly recorded from the muddy sand bottom type in the southwest region of the Marmara Sea, which has higher biodiversity of macrobenthic species than other regions. Different methodological approaches were conducted to understand its feeding, such as DNA metabarcoding and isotope analysis to identify its prey spectra and assign a trophic level. Sampled specimens were full of liquid in their stomachs without any discernible visually identifiable prey items. The metabarcoding analyses were also unsuccessful in identifying any prey items. Trophic position calculation based on nitrogen isotope in muscles highlighted that O. centrina has the highest trophic position compared to the other sharks and rays in the Sea of Marmara. Although it was found mainly feeding on polychaetes and sipunculids species from previous studies, the δ15 N values made the authors cautious about the possibility of this species feeding on low trophic-level benthic invertebrates. Because the authors could not observe the presence of shark vitellus in the stomachs and could not succeed in DNA identification for prey, this study highlights high δ15 N values similar to top predators for O. centrina. The authors conclude that this species strategically feeds mainly on shark eggs to fulfil its nutritional requirements with minimum energy expenditure in line with its slow-moving behaviour and mouth morphology.

Automated Cardiac Chamber Size and Cardiac Physiology Measurement in Water Fleas by U-Net and Mask RCNN Convolutional Networks.

Simple SummaryWith the rapid development of technology, artificial intelligent become a major breakthrough that can help human with laborious job. Previously cardiac imaging in Daphnia was also suffer from laborious and tedious process to extract some information from it. Thus the aim of this study was to develop a simple artificial intelligent based method to help anyone in this field to perform analysis in fast, reliable, and less tedious manner. In this study, we compare U-Net and Mask RCNN and found out that Mask RCNN was perform better than U-Net in cardiac chamber area estimation. From this data, several parameter like heart rhythm, stroke volume, ejection fraction, fractional shortening, and cardiac output can be extracted. The validation was done by comparing the normal and Roundup exposed group and it show that Roundup can increase the stroke volume, cardiac output, and the shortening fraction of Daphnia magna.Water fleas are an important lower invertebrate model that are usually used for ecotoxicity studies. Contrary to mammals, the heart of a water flea has a single chamber, which is relatively big in size and with fast-beating properties. Previous cardiac chamber volume measurement methods are primarily based on ImageJ manual counting at systolic and diastolic phases which suffer from low efficiency, high variation, and tedious operation. This study provides an automated and robust pipeline for cardiac chamber size estimation by a deep learning approach. Image segmentation analysis was performed using U-Net and Mask RCNN convolutional networks on several different species of water fleas such as Moina sp., Daphnia magna, and Daphnia pulex. The results show that Mask RCNN performs better than U-Net at the segmentation of water fleas’ heart chamber in every parameter tested. The predictive model generated by Mask RCNN was further analyzed with the Cv2.fitEllipse function in OpenCV to perform a cardiac physiology assessment of Daphnia magna after challenging with the herbicide of Roundup. Significant increase in normalized stroke volume, cardiac output, and the shortening fraction was observed after Roundup exposure which suggests the possibility of heart chamber alteration after roundup exposure. Overall, the predictive Mask RCNN model established in this study provides a convenient and robust approach for cardiac chamber size and cardiac physiology measurement in water fleas for the first time. This innovative tool can offer many benefits to other research using water fleas for ecotoxicity studies.

Molecular cloning and functional characterization of KCNQ1 in shell biomineralisation of pearl oyster Pinctada fucata martensii

KCNQ1, a voltage-gated potassium ion channel, plays an important role in various physiological processes, including osteoblast differentiation in higher animals. However, its function in lower invertebrates such as marine shellfish remains poorly understood. Pearl oysters, such as P. fucata martensii, are ideal for studying biomineralisation. In this study, a full-length cDNA of KCNQ1 from P. fucata martensii (PfKCNQ1) was obtained, and its function in shell formation was investigated. The full-length 3945 bp cDNA of PfKCNQ1 included an open reading frame (ORF) of 1944 bp encoding a polypeptide of 647 amino acids. Multiple sequence alignment revealed high homology with KCNQ1 from other species, with six transmembrane domains (S1 − S6) and a pore (P) region. Expression pattern analysis showed that PfKCNQ1 was expressed in all tested tissues, with highest expression in mantle and heart, and shell notching induced PfKCNQ1 expression. Silencing PfKCNQ1 expression inhibited PfKCNQ1 expression and downregulated four biomineralisation-related genes (Shematrin, Pif80, N16 and MSI60). Disordered crystals or “hollows” were visible in the shell ultrastructure by scanning electron microscopy following PfKCNQ1 knockdown. The results suggested that PfKCNQ1 may participate in or regulate biomineralisation and shell formation in pearl oyster.