Search

Cockroaches are well-known pests and quarantined organisms worldwide. Due to morphological diversity and a lack of molecular data, their classification and identification are facing challenges. This study performed classification, identification, and DNA barcoding for cockroaches collected from China. Seventy-six samples were morphologically identified as seven species of two superfamilies that included Blattella germanica, Eublaberus posticus and Blaptica dubia belonging to the superfamily Blaberoidea, and Periplaneta americana, Periplaneta lateralis, Periplaneta fuliginosa and Periplaneta australasiae belonging to the superfamily Blattoidea. Based on sequence alignments of nine ribosomal and mitochondrial genes across the order Blattaria retrieved from GenBank, rDNA ITS2-517 bp and mtDNA 16S-327 bp were screened as candidates for molecular identification. Universal primers were designed for PCR amplification, cloning, and sequencing of the 37 representative samples. Sequence alignments and phylogeny analysis showed that both ITS2 and 16S confirmed samples 1-9, 20-24, and 25-29 as B. germanica, P. americana, and P. lateralis, respectively; only 16S (not ITS2) confirmed samples 10-14, 15-19, 30-34, and 35-37 as E. posticus, Blap. dubia, P. fuliginosa, and P. australasiae, respectively, indicating that 16S was a better target than ITS2 for molecular identification of cockroaches. Conservative motif and divergence analysis further revealed that ITS2 sequences vary significantly among different taxa, whereas 16S sequences are relatively conserved. There is an obvious barcoding gap between maximum intraspecific divergence and minimum interspecific divergence (2.57 % vs. 5.62 %) for ITS2, but not for 16S (6.15 % vs. 2.63 %). Therefore, it was confirmed that ITS2 is an ideal DNA barcode for molecular identification of cockroaches at lower category., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

We described a new species of cockroach, Periplaneta gajajimana sp. nov., which was collected in Gajajima, Kagoshima-gun Toshimamura, Kagoshima Prefecture, Japan, on November 2012. The new species is characterized by its reddish brown to blackish brown body, smooth surface pronotum, well developed compound eyes, dark brown head apex, dark reddish brown front face and small white ocelli connected to the antennal sockets. In male, the tegmen tip reach the abdomen end or are slightly shorter, while in the female, it does not reach the abdominal end and exposes the abdomen beyond the 7 th abdominal plate. We confirmed the validity of this new species by breeding the specimens in our laboratory to demonstrate that the features of the progeny were maintained for several generations. For comparison and easy identification of this new species, the key to species identification of the genus Periplaneta that had been reported in Japan to date are also presented.

Cockroaches inhabit various habitats, which will influence their microbiome. Although the microbiome can be influenced by the diet and environmental factors, it can also differ between species. Therefore, we conducted 16S rDNAtargeted high-throughput sequencing to evaluate the overall bacterial composition of the microbiomes of 3 cockroach species, Periplaneta americana, P. japonica, and P. fuliginosa, raised in laboratory for several generations under the same conditions. The experiments were conducted using male adult cockroaches. The number of operational taxonomic units (OTUs) was not significantly different among the 3 species. With regard to the Shannon and Pielou indexes, higher microbiome values were noted in P. americana than in P. japonica and P. fuliginosa. Microbiome composition was also evaluated, with endosymbionts accounting for over half of all OTUs in P. japonica and P. fuliginosa. Beta diversity analysis further showed that P. japonica and P. fuliginosa had similar microbiome composition, which differed from that of P. americana. However, we also identified that P. japonica and P. fuliginosa host distinct OTUs. Thus, although microbiome compositions may vary based on multiple conditions, it is possible to identify distinct microbiome compositions among different Periplaneta cockroach species, even when the individuals are reared under the same conditions.

The globally distributed American cockroach ( Periplaneta americana ) is considered a pest, but it has been widely used in traditional Chinese medicine. In the past, the American cockroach's genome and transcriptomes were sequenced, but the differential expression transcripts between developmental stages were unavailable. We performed the de novo assembly and analysis of American cockroach transcriptomes from four developmental stages. Approximately 200 million high-quality paired-end reads were generated by using Illumina Hiseq 2000 sequencer. The assembly produced 291,250 transcripts with an average length of 714 bp. In addition, 38,052 microsatellites and 11,060,020 transposable elements were identified. Based on sequence homology, 53,262 transcripts were annotated. After calculating the expression levels of all the transcripts, we found that 13 transcripts were highly expressed in all the samples and at least two, p10 and actin-related protein 1, played important roles during development. A total of 7954 differentially expressed transcripts (DETs) were identified. The adult had the largest number of DETs when compared to other samples (4818), while the 3rd and 8th larva had the least number of DETs (1332). We performed gene enrichment analysis with the DETs, and some interesting results were detected in the different groups. For example, chitin is the major component of the insect exoskeleton, and the chitin-related genes in larvae and new molted samples had higher expression levels than in adults. In addition, the enrichment analysis detected many chitin-related pathways. Our study performed the first large-scale comparative transcriptomics between the developmental stages of American cockroach, which could provide useful gene expression data for future studies.

The catecholamines norepinephrine and epinephrine regulate important physiological functions in vertebrates. In insects; these neuroactive substances are functionally replaced by the phenolamines octopamine and tyramine. Phenolamines activate specific guanine nucleotide-binding (G) protein-coupled receptors (GPCRs). Type 1 tyramine receptors are better activated by tyramine than by octopamine. In contrast; type 2 tyramine receptors are almost exclusively activated by tyramine. Functionally; activation of type 1 tyramine receptors leads to a decrease in the intracellular concentration of cAMP ([cAMP] i ) whereas type 2 tyramine receptors can mediate Ca 2+ signals or both Ca 2+ signals and effects on [cAMP] i . Here; we report that the American cockroach ( Periplaneta americana ) expresses a second type 1 tyramine receptor (PeaTAR1B) in addition to PeaTAR1A (previously called PeaTYR1). When heterologously expressed in flpTM cells; activation of PeaTAR1B by tyramine leads to a concentration-dependent decrease in [cAMP] i . Its activity can be blocked by a series of established antagonists. The functional characterization of two type 1 tyramine receptors from P. americana ; PeaTAR1A and PeaTAR1B; which respond to tyramine by changing cAMP levels; is a major step towards understanding the actions of tyramine in cockroach physiology and behavior; particularly in comparison to the effects of octopamine., Competing Interests: The authors declare no conflict of interest.

DNA barcoding promises to be a useful tool to identify pest species assuming adequate representation of genetic variants in a reference library. Here we examined mitochondrial DNA barcodes in a global urban pest, the American cockroach (Periplaneta americana). Our sampling effort generated 284 cockroach specimens, most from New York City, plus 15 additional U.S. states and six other countries, enabling the first large-scale survey of P. americana barcode variation. Periplaneta americana barcode sequences (n = 247, including 24 GenBank records) formed a monophyletic lineage separate from other Periplaneta species. We found three distinct P. americana haplogroups with relatively small differences within (≤0.6%) and larger differences among groups (2.4%-4.7%). This could be interpreted as indicative of multiple cryptic species. However, nuclear DNA sequences (n = 77 specimens) revealed extensive gene flow among mitochondrial haplogroups, confirming a single species. This unusual genetic pattern likely reflects multiple introductions from genetically divergent source populations, followed by interbreeding in the invasive range. Our findings highlight the need for comprehensive reference databases in DNA barcoding studies, especially when dealing with invasive populations that might be derived from multiple genetically distinct source populations.