Differentiation Of Species Research Articles

Rapid species differentiation and typing of Acinetobacter baumannii

Acinetobacter (A.) baumannii has emerged as a difficult-to-treat nosocomial bacterial human pathogen. A. baumannii is to be dealt with under the “One Health” approach, and its surveillance in human, animal, and environmental settings assumes paramount importance in understanding its plausible transmission dynamics. Accurate identification of A. baumannii, its clonal complexes, and sequence types is important for understanding the epidemiological distribution, evolutionary relationships, and transmission dynamics. A wide range of genotyping techniques are applied for the differentiation of the Acinetobacter calcoaceticus-baumannii (ACB) complex. However, there is no single straight-forward genotype method applied for rapid assays. Currently, two multilocus sequence typing (MLST) Oxford and Pasture schemes exist; though considered a gold standard for sequence typing, harmonizing the schemes is not a straightforward process. The whole genome sequencing-based core-genome multilocus sequence typing (cgMLST) and core single nucleotide polymorphism (cgSNP) are robust and precise sequence typing; however, they are expensive, depending on the quality of sequencing and demand a higher level of computational skills. In the past decade, matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) based species identification has been successfully employed for rapid discrimination of the ACB complex. MALDI typing is rapid, easier, cheaper, and as reliable as molecular methods. Strain level A. baumannii identification confidence improved upon augmentation of existing databases with in-house reference spectra of well-defined isolates. The application of artificial intelligence and machine learning might be useful in clonal sequence types (ST)-level identification. The genus Acinetobacter’s taxonomic classification is evolving, and newer STs are being described; hence, the establishment of a central repository of A. baumannii reference spectra will help in harmonizing across the laboratories and help in the global level surveillance program on A. baumannii in “One Health” perspective. This review sheds light on the challenges related to techniques employed for the identification of Acinetobacter and the potential application and future perspectives of MALDI-TOF MS.

The genus Polistes Latreille, 1802 (Hymenoptera: Vespidae) of Brazil: morphological diagnoses, identification key, and geographical distribution

Polistes Latreille, 1802 is a genus with cosmopolitan distribution, with 238 species in the world, 94 in the New World. Brazil has 43 species but there is not a complete understanding of the distribution of these species in the country, making it difficult to estimate the diversity of the genus for each region. Species descriptions in Polistes are typically short, and some diagnostic characteristics are subtle, making it difficult to identify and differentiate species of Polistes. To facilitate the identification and differentiation of species, standardized diagnoses, illustrations, geographic distribution, and a dichotomous key are proposed for all Polistes species occurring in Brazil.

Integrated Histological and Molecular Analysis of Filarial Species and Associated Wolbachia Endosymbionts in Human Filariasis Cases Presenting Atypically in Thailand.

Atypical presentations of filariasis have posed diagnostic challenges due to the complexity of identifying the causative species and the difficulties in both diagnosis and treatment. In this study, we present the integrative histological and molecular analysis of seven atypical filariasis cases observed in regions of nonendemicity of Thailand. All filariasis cases were initially diagnosed based on histological findings. To confirm the causative species, molecular characterization based on both filarial mitochondrial (mt 12S rRNA and COI genes) and nuclear ITS1 markers was performed, together with the identification of associated Wolbachia bacterial endosymbionts. Among the cases studied, Brugia pahangi (N = 3), Brugia malayi (N = 1), Dirofilaria sp. "hongkongensis" (N = 2), and a suspected novel filarial species genetically related to Pelecitus copsychi (N = 1) were identified. By targeting the 16S rRNA gene, Wolbachia was also molecularly amplified in two cases of infection with Dirofilaria sp. "hongkongensis." Phylogenetic analysis further revealed that the detected Wolbachia could be classified into supergroups C and F, indicating the high genetic diversity of this endosymbiont in Dirofilaria sp. "hongkongensis." Furthermore, this study demonstrates the consistency between histological findings and species identification based on mitochondrial loci rather than on the nuclear ITS1. This suggests the utility of mitochondrial markers, particularly COI, as a highly sensitive and reliable diagnostic tool for the detection and differentiation of filarial species in clinical specimens. Precise identification of the causative species will facilitate accurate diagnosis and treatment and is also essential for the development of epidemiological and preventive strategies for filariasis.

Genetic structure of populations of Salvia ceratophylloides endemic to southern Calabria (southern Italy)

Assessing the degree of genetic diversity and differentiation of rare or endangered endemic species is essential to evaluate the conservation status of populations and successively implement appropriate conservation strategies. We investigated the population structure of Salvia ceratophylloides Ard., a scapose hemicryptophyte endemic to Calabria (southern Italy), both to answer questions about its genetic structure and to determine whether the actual population size has undergone significant demographic changes in the near past. The data obtained from the census showed that the populations are characterised by a greater number of adult individuals than juveniles and are on declining. The genetic analysis carried out on 99 individuals from four populations of the species under study, shows a mean expected heterozygosity value of 0.50 and an overall differentiation value of 0.083. The population structure shows that the four studied populations are distinct genetic units, genetically linked to four different ancestral gene pools. Bayesian analysis based on ABC models indicates that the present populations underwent a significant reduction in size in the past. This corresponds to the demographic decline at the end of the 19th century, which according to the literature, was due to the strong anthropic pressure (agriculture, grazing, fire and plantations) of Reggio Calabria suburbs. We can therefore conclude that populations are not affected by inbreeding and low genetic diversity and that there is no immediate danger of genetic erosion, and that the problems associated with population decline, past and present, are exclusively due to anthropogenic causes.

Internal transcribed spacer as effective molecular marker for the detection of natural hybridization between the bivalves Pinna nobilis and Pinna rudis.

The Pinna nobilis, a Mediterranean mollusc, has suffered population declines due to a massive mortality event associated with various factors including the parasite Haplosporidium pinnae. Some populations show resilience, possibly due to local environmental conditions. In this study, a molecular multiplex PCR method was developed using species-specific primers targeting Internal Transcribed Spacer (ITS) regions of P. nobilis and P. rudis, allowing accurate species identification and hybrid detection. Samples from Mediterranean areas were analysed, including putative hybrids and individuals from five other bivalve species. DNA was isolated, ITS regions were amplified and sequenced, and phylogenetic analyses confirmed species differentiation and primer specificity. The multiplex-PCR successfully identified P. nobilis, P. rudis, and their hybrids based on distinct amplicon patterns. This study highlights the value of molecular tools in species conservation, especially for monitoring and managing hybridization, supporting effective biodiversity conservation strategies.

Species divergence and environmental adaptation of Picea asperata complex at the whole genome level.

To study the interspecific differentiation characteristics of species originating from recent radiation, the genotyping-by-sequencing (GBS) technique was used to explore the kinship, population structure, gene flow, genetic variability, genotype-environment association and selective sweeps of Picea asperata complex with similar phenotypes from a genome-wide perspective. The following results were obtained: 14 populations of P. asperata complex could be divided into 5 clades; P. wilsonii and P. neoveitchii diverged earlier and were more distantly related to the remaining 6 spruce species. Various geological events have promoted the species differentiation of P. asperata complex. There were four instances of gene flow among P. koraiensis, P. meyeri, P. asperata, P. crassifolia and P. mongolica. The population of P. mongolica had the highest level of nucleotide diversity, and P. neoveitchii may have experienced a bottleneck recently. Genotype-environment association found that a total of 20,808 genes were related to the environmental variables, which enhanced the adaptability of spruce in different environments. Genes that were selectively swept in the P. asperata complex were primarily associated with plant stress resistance. Among them were some genes involved in plant growth and development, heat stress, circadian rhythms and flowering. In addition to the commonly selected genes, different spruce species also displayed unique genes subjected to selective sweeps that improved their adaptability to different habitats. Understanding the interspecific gene flow and adaptive evolution of Picea species is beneficial to further understanding the species relationships of spruce and can provide a basis for studying spruce introgression and functional genomics.

Use of tuf gene sequencing for Identification of Lactococci isolated from diseased rainbow trout (Oncorhynchus mykiss)

Lactococcosis is a bacterial infection that is characterized by the appearance of septicemia in fish. Traditionally, the identification of causes of disease outbreaks in aquaculture poses a major challenge due to their comparable characteristics. In this study, simple PCR and sequencing based on the tuf gene were developed to identify isolates belonging to the Streptococcaceae family. The outbreaks of lactococcosis in rainbow trout have been mainly associated with Lactococcus garvieae, but the emergence of closely related species, Lactococcus petauri and Lactococcus formosensis pose a challenge in accurate identification. The study aimed to identify Gram-positive catalase-negative cocci and differentiate between Lactococcosis-causing bacteria (LCB) in rainbow trout isolates associated with lactococcosis outbreaks in Iran. Seventy-five Gram-positive cocci strains from diseased rainbow trout were tested using a PCR and sequencing method targeting the tuf gene. Sequence and phylogenetic analyses were conducted to distinguish between closely related Lactococcus species. The PCR results revealed a successful amplification with tuf gene primers for all strains, allowing species identification. The sequence analysis showed that all 29 isolates initially identified as L.garvieae were 100% identical to L.petauri, indicating a previous misclassification. This work is the first report by L.petauri of Iran. Analysis of tuf gene sequences revealed different patterns of single nucleotide polymorphism (SNP) for accurate species differentiation and phylogenetic analysis confirmed different clusters for LCB. The study highlights the misidentification of L.petauri as L.garvieae in lactococcosis outbreaks and the importance of accurate species differentiation in disease management. The tuf gene sequencing method shows promise for practical, cost-effective, and accurate differentiation of closely related streptococcal species in aquaculture. These findings strongly indicate the need to re-evaluate the initial identification of isolates from fish with lactococcisis. The findings of this study also suggest that the tuf gene sequencing, established in this research for its practicality and cost-efficiency, could potentially be integrated into routine diagnostic procedures for Gram-positive, catalase-negative cocci associated with outbreaks of infections in aquatic animals; however, further experimental works are warranted.

Exploring the interspecific relationships among Dendrobium species via electrochemical fingerprinting techniques

This study investigated the interspecific relationships among 29 Dendrobium species using electrochemical fingerprinting techniques. Differential pulse voltammetry was employed to record species-specific electrochemical profiles in both phosphate buffer solution (PBS) and acetic acid buffer solution (ABS). Distinct voltammetric patterns were observed for each species, with ABS yielding higher peak currents compared to PBS. On average, peak currents in ABS were 37.2 % ± 5.8 % higher than in PBS across all species. For example, D. nobile showed a peak current of 12.3 μA in ABS compared to 8.9 μA in PBS, a 38.2 % increase. Normalized two-dimensional plots of the electrochemical fingerprints served as unique signatures for species differentiation. Cluster analysis of the electrochemical data revealed phylogenetic relationships largely consistent with previous molecular studies, while also highlighting novel groupings. For instance, D. parishii and D. pulchellum formed separate branches, indicating distant relationships with other species. Common species such as D. officinale, D. nobile, D. primulinum, and D. loddigesii clustered together, confirming their close relationships. Interestingly, species from Sect. Dendrobium showed mixed clustering with species from four other sections, reflecting the genus's complex evolutionary history. While some inconsistencies with previous molecular phylogenetic studies were noted, such as the distant relationship between D. parishii and D. anosmum, the overall congruence between electrochemical and molecular data validates the potential of this approach. This study demonstrates that electrochemical fingerprinting, combined with appropriate data analysis techniques, can provide valuable insights into the taxonomic relationships and chemical diversity of Dendrobium species, offering a complementary tool to traditional morphological and molecular methods for plant systematics and conservation efforts.

Development of Leptolyngbya sp. BL0902 into a model organism for synthetic biological research in filamentous cyanobacteria.

Cyanobacteria have great potential in CO2-based bio-manufacturing and synthetic biological studies. The filamentous cyanobacterium, Leptolyngbya sp. strain BL0902, is comparable to Arthrospira (Spirulina) platensis in commercial-scale cultivation while proving to be more genetically tractable. Here, we report the analyses of the whole genome sequence, gene inactivation/overexpression in the chromosome and deletion of non-essential chromosomal regions in this strain. The genetic manipulations were performed via homologous double recombination using either an antibiotic resistance marker or the CRISPR/Cpf1 editing system for positive selection. A desD-overexpressing strain produced γ-linolenic acid in an open raceway photobioreactor with the productivity of 0.36 g·m-2·d-1. Deletion mutants of predicted patX and hetR, two genes with opposite effects on cell differentiation in heterocyst-forming species, were used to demonstrate an analysis of the relationship between regulatory genes in the non-heterocystous species. Furthermore, a 50.8-kb chromosomal region was successfully deleted in BL0902 with the Cpf1 system. These results supported that BL0902 can be developed into a stable photosynthetic cell factory for synthesizing high value-added products, or used as a model strain for investigating the functions of genes that are unique to filamentous cyanobacteria, and could be systematically modified into a genome-streamlined chassis for synthetic biological purposes.

Investigating the relative role of dispersal and demographic traits in predictive phylogeography

Many studies suggest that aside from environmental variables, such as topography and climate, species‐specific ecological traits are relevant to explain the geographic distribution of intraspecific genetic lineages. Here, we investigated whether and to what extent incorporating such traits systematically improves the accuracy of random forest models in predicting genetic differentiation among pairs of localities. We leveraged available ecological datasets for birds and tested the inclusion of two categories of ecological traits: dispersal‐related traits (i.e. morphology and foraging ecology) and demographic traits (such as species survival rate and generation length). We estimated genetic differentiation from published mitochondrial DNA sequences for 28 species of birds (1578 total genetic samples, 391 localities) in the Atlantic Forest of South America. Aside from the aforementioned ecological traits, we included geographic, topographic and climatic distances between localities as environmental predictors. We then created models using all available data to evaluate model uncertainty both across space and across the different categories of predictors. Finally, we investigated model uncertainty in predicting genetic differentiation individually for each species (a common challenge in conservation biology). Our results show that while environmental conditions are the most important predictors of genetic differentiation, model accuracy largely increases with the addition of ecological traits. Additionally, the inclusion of dispersal traits improves model accuracy to a larger extent than the inclusion of demographic traits. Similar results are observed in models for individual species, although model accuracy is highly variable. We conclude that ecological traits improve predictive models of genetic differentiation, refining our ability to predict phylogeographic patterns from existing data. Additionally, demographic traits may not be as informative as previously hypothesized. Finally, prediction of genetic differentiation for species with conservation concerns may require further careful assessment of the environmental and ecological variation within the species range.

Reclassification of type strains of Rhizobium indigoferae and Sinorhizobium kummerowiae into the species Rhizobium leguminosarum and Sinorhizobium meliloti, respectively.

The species Rhizobium indigoferae and Sinorhizobium kummerowiae were isolated from legume nodules and the 16S rRNA sequences of their respective type strains, CCBAU 71042T and CCBAU 71714T, were highly divergent from those of the other species of the genera Rhizobium and Sinorhizobium, respectively. However, the 16S rRNA gene sequences obtained for strains CCBAU 71042T and CCBAU 71714T several years after description, were different from the original ones, showing 100 % similarity to the type strains of Rhizobium leguminosarum and Sinorhizobium meliloti, respectively. Phylogenetic analyses of two housekeeping genes, recA and atpD, confirmed the high phylogenetic closeness of strains CCBAU 71042T and CCBAU 71714T to the respective type strains of R. leguminosarum and S. meliloti. In the present work, we compared the genomes of the type strains of R. indigoferae and S. kummerowiae available in several culture collections with those of the respective type strains of R. leguminosarum and S. meliloti, some of them obtained in this study. The calculated average nucleotide identity-blast and digital DNA-DNA hybridization values in both cases were higher than those recommended for species differentiation, supporting the proposal for the reclassification of the type strains of R. indigoferae and S. kummerowiae into the species R. leguminosarum and S. meliloti, respectively.

Biased gene introgression and adaptation in the face of chloroplast capture in Aquilegia amurensis.

Chloroplast capture, a phenomenon that can occur through interspecific hybridization and introgression, is frequently invoked to explain cytonuclear discordance in plants. However, relatively few studies have documented the mechanisms of cytonuclear coevolution and its potential for driving species differentiation and possible functional differences in the context of chloroplast capture. To address this crucial question, we chose the Aquilegia genus, which is known for having minimal sterility among species, and inferred that A. amurensis captured the plastome of A. parviflora based on cytonuclear discordance and gene flow between the two species. We focused on the introgression region and its differentiation from corresponding regions in closely related species, especially its composition in a chloroplast capture scenario. We found that nuclear genes encoding cytonuclear enzyme complexes (CECs; i.e., organelle-targeted genes) of chloroplast donor species were selectively retained and displaced the original CEC genes in chloroplast-receiving species due to cytonuclear interactions during introgression. Notably, the intrinsic correlation of CEC introgression was a greater degree of evolutionary distance for these CECs between A. amurensis and A. parviflora. Terpene synthase activity genes (GO: 0010333) were overrepresented among the introgressed genes, and more than 30% of these genes were CEC genes. These findings support our observations that floral terpene release pattern is similar between A. amurensis and A. parviflora compared with A. japonica. Our study clarifies the mechanisms of cytonuclear coevolution, species differentiation and functional differences in the context of chloroplast capture and highlights the potential role of chloroplast capture in adaptation.

Near-infrared spectroscopy and multivariate analysis as effective, fast, and cost-effective methods to discriminate Candida auris from Candida haemulonii.

Candida auris and Candida haemulonii are two emerging opportunistic pathogens that have caused an increase in clinical cases in the recent years worldwide. The differentiation of some Candida species is highly laborious, difficult, costly, and time-consuming depending on the similarity between the species. Thus, this study aimed to develop a new, faster, and less expensive methodology for differentiating between C. auris and C. haemulonii based on near-infrared (NIR) spectroscopy and multivariate analysis. C. auris CBS10913 and C. haemulonii CH02 were separated in 15 plates per species, and three isolated colonies of each plate were selected for Fourier transform near-infrared (FT-NIR) analysis, totaling 90 spectra. Subsequently, principal component analysis (PCA) and variable selection algorithms, including the successive projections algorithm (SPA) and genetic algorithm (GA) coupled with linear discriminant analysis (LDA), were employed to discern distinctive patterns among the samples. The use of PCA, SPA, and GA algorithms associated with LDA achieved 100% sensitivity and specificity for the discriminations. The SPA-LDA and GA-LDA algorithms were essential in selecting the variables (infrared wavelengths) of most importance for the models, which could be attributed to binding of cell wall structures such as polysaccharides, peptides, proteins, or molecules resulting from yeasts' metabolism. These results show the high potential of combined FT-NIR and multivariate analysis techniques for the classification of Candida-like fungi, which can contribute to faster and more effective diagnosis and treatment of patients affected by these microorganisms.

Light-driven incubation of Fusarium species and near-infrared spectroscopy for an early in vitro identification of Fusarium circinatum

This study explores the application of near-infrared (NIR) spectroscopy coupled with multivariate techniques for the rapid and accurate identification of four Fusarium species, with emphasis on the detection of Fusarium circinatum, the causative agent of “Pitch canker” disease in forests, cultured in vitro under distinct light conditions. The impact of two different incubation conditions, near-ultraviolet (NUV) and warm light, on the spectral characteristics of cultures was used as a strategy to improve the early fungal detection using spectroscopy. Spectral data were acquired using a portable NIR spectrometer at 48, 72, and 96 h post-cultivation from various zones of mycelial growth. The results showed distinct spectral profiles among Fusarium species, with notable variations depending on incubation light conditions and growth zones. NUV light conditions significantly improved species differentiation, especially in the central and middle zones of mycelial growth at 72 h post-cultivation (hpc). Partial least squares − discriminant analysis (PLS-DA) model under NUV light conditions provided the best identification strategy, achieving correct classification rates over 97% for all four species from 72 hpc and 82.5% of correct classification of F. circinatum. These findings demonstrate the effectiveness of the NIRS methodology supported with multivariate techniques and combined with optimization of light conditions and mycelial growth zone of cultures, for the early and rapid detection of Fusarium species in culture media, with potential implications for plant pathology diagnostics and disease management strategies.

Mitochondrial Genome Characteristics Reveal Evolution of Acanthopsetta nadeshnyi (Jordan and Starks, 1904) and Phylogenetic Relationships.

In the present study, the mitochondrial genomic characteristics of Acanthopsetta nadeshnyi have been reported and have depicted the phylogenetic relationship among Pleuronectidae. Combined with a comparative analysis of 13 PCGs, the TN93 model was used to review the neutral evolution and habitat evolution catalysis of the mitogenome to verify the distancing and purification selectivity of the mitogenome in Pleuronectidae. At the same time, a species differentiation and classification model based on mitogenome analysis data was established. This study is expected to provide a new perspective on the phylogenetic relationship and taxonomic status of A. nadeshnyi and lay a foundation for further exploration of environmental and biological evolutionary mechanisms.

Conservation genomics of the wild pumpkin Cucurbita radicans in Central Mexico: The influence of a changing environment on the genetic diversity and differentiation of a rare species

The genetic diversity found in natural populations is the result of the evolutionary forces in response to historical and contemporary factors. The environmental characteristics and geological history of Mexico promoted the evolution and diversification of plant species, including wild relatives of crops such as the wild pumpkins (Cucurbita). Wild pumpkin species are found in a variety of habitats, evidencing their capability to adapt to different environments. Despite the potential value of wild Cucurbita as a genetic reservoir for crops, there is a lack of studies on their genetic diversity. Cucurbita radicans is an endangered species threatened by habitat destruction leading to low densities in small and isolated populations. Here, we analyze Genotype by Sequencing genomic data of the wild pumpkin C. radicans to evaluate the influence of factors like isolation, demographic history, and the environment shaping the amount and distribution of its genetic variation. We analyzed 91 individuals from 14 localities along its reported distribution. We obtained 5,107 SNPs and found medium-high levels of genetic diversity and genetic structure distributed in four main geographic areas with different environmental conditions. Moreover, we found signals of demographic growth related to historical climatic shifts. Outlier loci analysis showed significant association with the environment, principally with precipitation variables. Also, the outlier loci displayed differential changes in their frequencies in response to future global climate change scenarios. Using the results of genetic structure, outlier loci and multivariate analyses of the environmental conditions, we propose priority localities for conservation that encompass most of the genetic diversity of C. radicans.

Comparative Analysis and Phylogeny of the Complete Chloroplast Genomes of Nine Cynanchum (Apocynaceae) Species.

Cynanchum belongs to the Apocynaceae family and is a morphologically diverse genus that includes around 200 shrub or perennial herb species. Despite the utilization of CPGs, few molecular phylogenetic studies have endeavored to elucidate infrafamilial relationships within Cynanchum through extensive taxon sampling. In this research, we constructed a phylogeny and estimated divergence time based on the chloroplast genomes (CPGs) of nine Cynanchum species. We sequenced and annotated nine chloroplast (CP) genomes in this study. The comparative analysis of these genomes from these Cynanchum species revealed a typical quadripartite structure, with a total sequence length ranging from 158,283 to 161,241 base pairs (bp). The CP genome (CPG) was highly conserved and moderately differentiated. Through annotation, we identified a total of 129-132 genes. Analysis of the boundaries of inverted repeat (IR) regions showed consistent positioning: the rps19 gene was located in the IRb region, varying from 46 to 50 bp. IRb/SSC junctions were located between the trnN and ndhF genes. We did not detect major expansions or contractions in the IR region or rearrangements or insertions in the CPGs of the nine Cynanchum species. The results of SSR analysis revealed a variation in the number of SSRs, ranging from 112 to 150. In five types of SSRs, the largest number was mononucleotide repeats, and the smallest number was hexanucleotide repeats. The number of long repeats in the cp genomes of nine Cynanchum species was from 35 to 80. In nine species of Cynanchum, the GC3s values ranged from 26.80% to 27.00%, indicating a strong bias towards A/U-ending codons. Comparative analyses revealed four hotspot regions in the CPG, ndhA-ndhH, trnI-GAU-rrn16, psbI-trnS-GCU, and rps7-ndhB, which could potentially serve as molecular markers. In addition, phylogenetic tree construction based on the CPG indicated that the nine Cynanchum species formed a monophyletic group. Molecular dating suggested that Cynanchum diverged from its sister genus approximately 18.87 million years ago (Mya) and species diversification within the Cynanchum species primarily occurred during the recent Miocene epoch. The divergence time estimation presented in this study will facilitate future research on Cynanchum, aid in species differentiation, and facilitate diverse investigations into this economically and ecologically important genus.

Crustacean endocrinology: Sexual differentiation and potential application for aquaculture

Crustaceans, which represent a significant subset of arthropods, are classified into three major classes: Ostracoda, Malacostraca, and Branchiopoda. Among them, sex manipulation in decapod species from the Malacostraca class has been extensively researched for aquaculture purposes and to study reproductive physiology and sexual plasticity. Some decapods exhibit sexual dimorphism that influences their biological and economic value. Monosex culture, in which only one sex is cultivated, increases production yields while reducing the risk of invasiveness, as genetic leakage into natural waters is less likely to occur. Differences in yield are also observed when cultivating different sexes, with all-male cultures of Macrobrachium rosenbergii being more profitable than both mixed and all-female cultures. Research on decapod sexual differentiation has led to a better understanding of sex determination and sexual differentiation processes in arthropods. Similar to most mammals and other vertebrate classes, Malacostraca crustaceans, including decapods, exhibit a cell-non-autonomous mode of sexual development. Genetic factors (e.g., sex chromosomes) and endocrine factors (e.g., insulin-like androgenic gland factor and crustacean female sex hormone) play pivotal roles in the development of sexually dimorphic traits. This review synthesizes the existing understanding of sex determination mechanisms and the role of sex hormones in decapod species. Additionally, it provides an overview of the methyl farnesoate, which has been suggested to be involved in male sex differentiation in some crab species, as well as the phenomenon of male-to-female sex reversal in host decapods caused by parasitic crustaceans.

Unveiling the mysteries of Asian herbivores resource partitioning in tropical wet-grassland ecosystem

Ecological niche partitioning is fundamental for the coexistence of sympatric species. However, the relationship between herbivore body size and forage availability on resource segregation and selection remains debatable. This study quantifies the niche differentiation and selectivity of forage species consumed by six Asian large herbivores (SLH), including mega-herbivores like Greater one-horned rhino (Rhinoceros unicornis), Asian elephant (Elephas maximus) and Asiatic wild buffalo (Bubalus arnee), and meso-herbivores like swamp deer (Rucervus duvaucelii), hog deer (Axis porcinus) and sambar (Rusa unicolor) in tropical wet-grasslands of the Brahmaputra floodplains. We hypothesized that body size influences dietary niche breadth and interspecific dietary similarities or dissimilarities, while forage availability influences forage selectivity among Asian herbivores. We used micro-histological technique, harvest method and Jacobs Index to quantify SLH foraging patterns, forage availability and preference, respectively. Results of the study revealed high niche breadth for elephant (0.56>Bs≤0.74) among mega-herbivores and for sambar (0.49>Bs≤0.64) among meso-herbivores. SLH showed a significant positive correlation between body size and niche breadth in wet season. High dietary overlap was recorded between buffalo and hog deer (0.79–0.86) and swamp deer and hog deer (0.75–0.86) among SLH, rhino and buffalo (0.80–0.83) among mega-herbivores, and swamp deer and hog deer (0.75–0.86) among meso-herbivores. High dietary dissimilarity was recorded between elephant and swamp deer (36–37 %), elephant and buffalo (27–33 %), and swamp deer and sambar (27–29 %). Compared to dry season (1354.54 ±641.30 g m˗2), significantly higher biomass was recorded in wet season (3026.93 ±1632.65 g m˗2; p<0.05). From dry to wet season, rhino, buffalo and hog deer shift their preferred forage from dicot to monocot. Dicot was the most preferred forage of elephant among mega-herbivores, and monocot of swamp deer and sambar among meso-herbivores. Mega- and meso-herbivores avoid invasives Merremia umbellata and Mimosa spp., while meso-herbivores avoid Mikania micrantha. Body size explains niche partitioning only for rhino, elephant and swamp deer. Forage availability contributed to niche breadth and forage preference. In conclusion, forage segregation, despite being challenging to interpret at taxonomic level, influences niche partitioning among mega- and meso-herbivores.

Scale Microornamentation of Six Species of Venomous Snakes from China

The scales of six venomous snake species from China were examined for their ultrastructure. Scanning electron microscopy was used to observe the scales, which were peeled off from the middle back of the snakes. The results revealed significant differences in the microdermatoglyphic structure patterns between the two families, Viperidae and Elapidae. Viperidae exhibited a “polygonal” structural unit, while Elapidae displayed arcs, pores, and strips as their basic structure. Additionally, there were notable differences in ultrastructure within each family. In Viperidae, Ovophis makazayazaya had a flat structural unit, Trimeresurus stejnegeri had a mound-like uplift near the center with a flat surrounding, and Protobothrops mucrosquamatus had an overall uplifted structure. In Elapidae, Ophiophagus hannah showed obvious differences in the size and arrangement of arc structures. The intraarc structure of Bungarus multicinctus resembled vertebral bodies, while that of Sinomicrurus peinani was columnar in shape. The ultrastructural characteristics of snake scales generally exhibited essential differences among advanced taxonomic units. However, there were detailed differences among species within the same family or genus. The initial formation of microornamentation features in scales may be related to the snakes’ habitat environment. Species formation through isolation is accompanied by the differentiation of these characteristics, and once species formation occurs, the features remain stable until the next species differentiation. There were instances of similar structures found in species with distant evolutionary relationships. This suggests that the microdermatoglyphic structure has taxonomic significance but may not necessarily have phylogenetic significance.