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Background: Lottiidae (Gray, 1840) is a derived family of Patellogastropoda and an important component of intertidal benthic communities. The mitochondrial genome (mitogenome) has been frequently used to analyze the phylogenetic relationships of Patellogastropoda. We used next-generation sequencing (NGS) to sequence the complete mitogenomes of five species. We analyzed the basic base composition characteristics of these mitogenomes, constructed a phylogenetic tree, compared the characteristics of gene rearrangement with other related species, and discussed the evolutionary patterns between gastropod species and the evolutionary relationships of each subclass. In addition, we aim to infer the differentiation time and evolutionary characteristics of various species in the order Patellogastropoda. These results will enrich the mitogenome database of Patellogastropoda and enhance our understanding of the genetic characteristics of Lottiidae and the phylogenetic relationships between gastropods. Results: We obtained the mitogenomes sequences of Lottia peitaihoensis, Patelloida saccharinoides, Patelloida ryukyuensis, Nipponacmea sp. and Nipponacmea nigrans, using next-generation sequencing technology. We analyzed the basic structural characteristics of their mitogenomes and found that their lengths ranged from 16.6 kbp to 19.1 kbp. While N. nigrans and P. saccharinoides contain 39 genes, L. peitaihoensis, P. ryukyuensis, and Nipponacmea sp. have only 38 genes, with one trnW less. The most abundant base among the five species is T, and most protein coding genes (PCGs) use ATT, ATG, and ATA as starting codons, and TAA and TAG as stopping codons. We selected the mitogenomes of 10 Lottiidae species for selection pressure analysis and found that all PCGs were subject to purifying selection. Phylogenetic analysis indicates that Patellogastropoda is a fundamental branch of the Gastropoda, and Lottiidae, within Patellogastropoda, is an independent branch at the outermost of the entire phylogenetic tree. Comparison of mitochondrial gene sequences of all Patellogastropoda species revealed a high degree of gene rearrangement within the family Lottiidae, eight sequences present among the 10 species examined. By estimating their divergence times, we found that the divergence of limpets occurred as early as the Permian period of the Paleozoic Era, and a large number of species diverged in the Cenozoic Era. Conclusion: The data obtained from this study will provide information on the assembly of the mitochondrial genome of the Lottiidae species, which will contribute to a better understanding of the evolutionary status and relationship among thes family of Patellogastropoda. [ABSTRACT FROM AUTHOR]

Background: The Caridea, affiliated with Malacostraca, Decapoda, and Pleocyemata, constitute one of the most significant shrimp groups. They are widely distributed across diverse aquatic habitats worldwide, enriching their evolutionary history. In recent years, considerable attention has been focused on the classification and systematic evolution of Caridea, yet controversies still exist regarding the phylogenetic relationships among families. Methods: Here, the complete mitochondrial genome (mitogenome) sequences of five caridean species, namely Heterocarpus sibogae, Procletes levicarina, Macrobrachium sp., Latreutes anoplonyx, and Atya gabonensis, were determined using second-generation high-throughput sequencing technology. The basic structural characteristics, nucleotide composition, amino acid content, and codon usage bias of their mitogenomes were analyzed. Selection pressure values of protein-coding genes (PCGs) in species within the families Pandalidae, Palaemonidae, and Atyidae were also computed. Phylogenetic trees based on the nucleotide and amino acid sequences of 13 PCGs from 103 caridean species were constructed, and divergence times for various families within Caridea were estimated. Results: The mitogenome of these five caridean species vary in length from 15,782 to 16,420 base pairs, encoding a total of 37 or 38 genes, including 13 PCGs, 2 rRNA genes, and 22 or 23 tRNA genes. Specifically, L. anoplonyx encodes an additional tRNA gene, bringing its total gene count to 38. The base composition of the mitogenomes of these five species exhibited a higher proportion of adenine-thymine (AT) bases. Six start codons and four stop codons were identified across the five species. Analysis of amino acid content and codon usage revealed variations among the five species. Analysis of selective pressure in Pandalidae, Palaemonidae, and Atyidae showed that the Ka/Ks values of PCGs in all three families were less than 1, indicating that purifying selection is influencing on their evolution. Phylogenetic analysis revealed that each family within Caridea is monophyletic. The results of gene rearrangement and phylogenetic analysis demonstrated correlations between these two aspects. Divergence time estimation, supported by fossil records, indicated that the divergence of Caridea species occurred in the Triassic period of the Mesozoic era, with subsequent differentiation into two major lineages during the Jurassic period. Conclusions: This study explored the fundamental characteristics and phylogenetic relationships of mitogenomes within the infraorder Caridea, providing valuable insights into their classification, interspecific evolutionary patterns, and the evolutionary status of various Caridea families. The findings provide essential references for identifying shrimp species and detecting significant gene rearrangements within the Caridea infraorder. [ABSTRACT FROM AUTHOR]

Fulgoraria rupestris is a predatory marine gastropod belonging to Neogastropoda and possessing considerable taxonomic significance. However, research on this species remains limited. We acquired the complete mitochondrial genome of F. rupestris through second-generation sequencing and conducted an analysis of its genome structural features. The mitochondrial genome of F. rupestris spans a total length of 16,223 bp and encompasses 37 genes (13 protein-coding genes (PCGs), 22 transfer RNAs, and 2 ribosomal RNAs). Notably, most tRNAs exhibit the typical cloverleaf structure, but there is an absence of the Dihydrouridine (DHU) arm in the trnS1 and trnS2 genes. The A + T content is 68.67%, indicating a pronounced AT bias. Additionally, we conducted a selection pressure analysis on the mitochondrial genomes of four species within Volutidae, revealing that all PCGs are subjected to purifying selection. In comparison to other species within Neogastropoda, F. rupestris shares an identical gene arrangement. Additionally, based on mitochondrial genome sequences of the 13 PCGs from 50 species within Neogastropoda, we constructed a phylogenetic tree. The phylogenetic tree indicates F. rupestris forms a clade with species within the family Volutidae (Cymbium olla, Neptuneopsis gilchristi, and Melo melo). This study serves as a valuable reference for future research on F. rupestris, offering insights for the upcoming phylogenetic and taxonomic classification within Neogastropoda. Furthermore, the findings provide valuable information for the development of genetic resources in this context. [ABSTRACT FROM AUTHOR]

The clam Macridiscus multifarius is ecologically and economically important in the coastal regions of China. In this study, the IIB-RAD method was used to investigate the population diversity and structure of M. multifarius along the coast of China. Genomic DNA was extracted, sequenced, and subjected, resulting in 110.88 Gb of clean reads. Analysis showed that the M. multifarius populations along the coast of China exhibited a moderate to high level of genetic diversity (mean: H O = 0.272, H E = 0.365, π = 0.390, and F IS = 0.268). Further analysis of high-quality single nucleotide polymorphisms was used to generate a maximum-likelihood phylogenetic tree, principal component analysis, and F ST values. The results revealed that there is no notable genetic differentiation among the nine M. multifarius populations south of the Yangtze River estuary. However, the Yancheng population shows clear genetic differentiation compared with the other nine populations, possibly linked to the barrier effect of the Yangtze dilution water and ocean current system. We believe that these results provide genetic insights for fisheries management to plan fisheries policies for M. multifarius and conserve natural resources. [ABSTRACT FROM AUTHOR]

Simple Summary: In this paper, a three-round nested PCR assay with high specificity and sensitivity (2.62 copies/reaction), employing the Pseudomonas plecoglossicida sctU gene, was established. The detection system was used to detect large yellow croaker samples in the Zhejiang and Fujian areas. It was found that March and April were the peak times of visceral white nodules disease, which was inversely related to temperature. Using this detection method, early detection of visceral white nodules disease in large yellow croakers could be realized. The visceral white nodules disease in the internal organs of Larimichthys crocea has caused significant harm in the aquaculture of this species, with Pseudomonas plecoglossicida considered one of the core pathogens causing this disease. In this study, we designed three pairs of specific nested PCR primers targeting the sctU gene of P. plecoglossicida, a crucial component of the Type III secretion system (T3SS), which is instrumental in bacterial pathogenesis and virulence. Through the optimization of PCR reaction conditions, specificity testing, and sensitivity determination, a method was established for the accurate detection of P. plecoglossicida. This method yielded single amplification products, exhibited a false positive rate of zero for reference bacteria, and achieved a detection sensitivity of a minimum of 2.62 copies/reaction for the target sequence. Using the detection method, we conducted analyses on the diseased populations of L. crocea, involving a total of 64 screened fishes along the southeast coast of China from 2021 to 2023. The results revealed that the infection rate of P. plecoglossicida in diseased L. crocea exceeded over 90% in March and April, while in other months, the maximum recorded infection rate was merely 10%. The detection method developed in this study shows potential for early warning and routine monitoring of visceral white nodules disease in the internal organs of species such as L. crocea. [ABSTRACT FROM AUTHOR]

Background: Despite the Caridean shrimps' vast species richness and ecological diversity, controversies persist in their molecular classification. Within Caridea, the Pandalidae family exemplifies significant taxonomic diversity. As of June 25, 2023, GenBank hosts only nine complete mitochondrial genomes (mitogenomes) for this family. The Plesionika genus within Pandalidae is recognized as polyphyletic. To improve our understanding of the mitogenome evolution and phylogenetic relationships of Caridea, this study introduces three novel mitogenome sequences from the Plesionika genus: P. ortmanni, P. izumiae and P. lophotes. Methods: The complete mitochondrial genomes of three Plesionika species were sequenced utilizing Illumina's next-generation sequencing (NGS) technology. After assembling and annotating the mitogenomes, we conducted structural analyses to examine circular maps, sequence structure characteristics, base composition, amino acid content, and synonymous codon usage frequency. Additionally, phylogenetic analysis was performed by integrating existing mitogenome sequences of true shrimp available in GenBank. Results: The complete mitogenomes of the three Plesionika species encompass 37 canonical genes, comprising 13 protein-coding genes (PCGs), 22 transfer RNAs (tRNAs), two ribosomal RNAs (rRNAs), and one control region (CR). The lengths of these mitogenomes are as follows: 15,908 bp for P. ortmanni, 16,074 bp for P. izumiae and 15,933 bp for P. lophotes. Our analyses extended to their genomic features and structural functions, detailing base composition, gene arrangement, and codon usage. Additionally, we performed selection pressure analysis on the PCGs of all Pandalidae species available in Genbank, indicating evolutionary purification selection acted on the PCGs across Pandalidae species. Compared with the ancestral Caridea, translocation of two tRNA genes, i.e., trnP or trnT, were found in the two newly sequenced Plesionika species—P. izumiae and P. lophotes. We constructed a phylogenetic tree of Caridea using the sequences of 13 PCGs in mitogenomes. The results revealed that family Pandalidae exhibited robust monophyly, while genus Plesionika appeared to be a polyphyletic group. Conclusions: Gene rearrangements within the Pandalidae family were observed for the first time. Furthermore, a significant correlation was discovered between phylogenetics of the Caridea clade and arrangement of mitochondrial genes. Our findings offer a detailed exploration of Plesionika mitogenomes, laying a crucial groundwork for subsequent investigations into genetic diversity, phylogenetic evolution, and selective breeding within this genus. [ABSTRACT FROM AUTHOR]

Simple Summary: The mitochondrial COI gene as a molecular marker is widely used in genetic diversity and population genetic diversity analysis. In this study, mitochondrial COI was used to analyze the genetic diversities of eight populations of Nerita yoldii along the coast of China. The results showed that N. yoldii has a high level of genetic diversity, with genetic structure differences observed between the Xiapu population and six other populations, excluding the Taizhou population. The results of neutral tests and nucleotide mismatch analyses indicate a historical demographic expansion in the N. yoldii population. Our study results provide foundational data for the conservation and sustainable utilization of N. yoldii resources. Nerita yoldii is a euryhaline species commonly found in the intertidal zone. To investigate the genetic diversity of 233 N. yoldii individuals from eight locations along the coast of China, we utilized the mitochondrial COI gene as a molecular marker. A total of 34 haplotypes were detected, exhibiting a mean haplotype diversity (Hd) of 0.5915 and a mean nucleotide diversity (Pi) of 0.0025, indicating high levels of genetic diversity among all populations. An analysis of molecular variance (AMOVA) indicated that the primary source of genetic variation occurs within populations. In addition, neutral tests and mismatch analyses suggested that N. yoldii populations may have experienced bottleneck events. Moderate genetic differentiation was observed between Xiapu and other populations, excluding the Taizhou population, and may be attributed to the ocean currents. Intensively studying the genetic variation and population structure of N. yoldii populations contributes to understanding the current population genetics of N. yoldii in the coastal regions of China. This not only provides a reference for the study of other organisms in the same region but also lays the foundation for the systematic evolution of the Neritidae family. [ABSTRACT FROM AUTHOR]