Search

Many plant-sucking stinkbugs possess a specialized symbiotic organ with numerous crypts in a posterior region of the midgut. In stinkbugs of the superfamily Pentatomoidea, specific γ-proteobacteria are hosted in the crypt cavities, which are vertically transmitted through host generations and essential for normal growth and survival of the host insects. Here we report the discovery of an exceptional gut symbiotic association in the saw-toothed stinkbug, Megymenum gracilicorne (Hemiptera: Pentatomoidea: Dinidoridae), in which specific γ-proteobacterial symbionts are not transmitted vertically but acquired environmentally. Histological inspection identified a very thin and long midgut symbiotic organ with two rows of tiny crypts whose cavities harbor rod-shaped bacterial cells. Molecular phylogenetic analyses of bacterial 16S rRNA gene sequences from the symbiotic organs of field-collected insects revealed that (i) M. gracilicorne is stably associated with Pantoea-allied γ-proteobacteria within the midgut crypts, (ii) the symbiotic bacteria exhibit a considerable level of diversity across host individuals and populations, (iii) the major symbiotic bacteria represent an environmental bacterial lineage that was reported to be capable of symbiosis with the stinkbug Plautia stali, and (iv) the minor symbiotic bacteria also represent several bacterial lineages that were reported as cultivable symbionts of P. stali and other stinkbugs. The symbiotic bacteria were shown to be generally cultivable. Microbial inspection of ovipositing adult females and their eggs and nymphs uncovered the absence of stable vertical transmission of the symbiotic bacteria. Rearing experiments showed that symbiont-supplemented newborn nymphs exhibit improved survival, suggesting the beneficial nature of the symbiotic association.

Many plant-sucking stinkbugs possess a specialized symbiotic organ with numerous crypts in a posterior region of the midgut. In stinkbugs of the superfamily Pentatomoidea, specific γ-proteobacteria are hosted in the crypt cavities, which are vertically transmitted through host generations and essential for normal growth and survival of the host insects. Here we report the discovery of an exceptional gut symbiotic association in the saw-toothed stinkbug

Cockroaches are commonly found in human residences and notorious as hygienic and nuisance pests. Notably, however, no more than 30 cockroach species are regarded as pests, while the majority of 4,500 cockroaches in the world are living in forest environments with little relevance to human life. Why some cockroaches have exceptionally adapted to anthropic environments and established pest status is of interest. Here we investigated the German cockroach

Zoological Letters, an open access online journal launched in 2015 is entering its third year of publication, and now seeks to drive new insights in evolutionary and comparative zoology by the inclusion of paleontological studies into its scope.

Cladobranchian sea slugs are characterized by a number of dorsal projections, called "cerata," which are presumably involved in such biological functions as kleptocnidal defense, gas exchange, and symbiotic photosynthesis. Here, we investigated the developmental pattern of ceras formation in a cladobranchian

A new open-access journal, Zoological Letters, was launched as a sister journal to Zoological Science, in January 2015. The new journal aims at publishing topical papers of high quality from a wide range of basic zoological research fields. This review highlights the notable reviews and research articles that have been published in the first year of Zoological Letters, providing an overview on the current achievements and future directions of the journal.

Cockroaches are commonly found in human residences and notorious as hygienic and nuisance pests. Notably, however, no more than 30 cockroach species are regarded as pests, while the majority of 4,500 cockroaches in the world are living in forest environments with little relevance to human life. Why some cockroaches have exceptionally adapted to anthropic environments and established pest status is of interest. Here we investigated the German cockroach Blattella germanica, which is a cosmopolitan pest species, and the forest cockroach Blattella nipponica, which is a wild species closely related to B. germanica. In contrast to easy rearing of B. germanica, laboratory rearing of B. nipponica was challenging-several trials enabled us to keep the insects for up to three months. We particularly focused on the distribution patterns of specialized cells, bacteriocytes, for harboring endosymbiotic Blattabacterium, which has been suggested to contribute to host's nitrogen metabolism and recycling, during the postembryonic development of the insects. The bacteriocytes were consistently localized to visceral fat bodies filling the abdominal body cavity, where a number of single bacteriocytes were scattered among the adipocytes, throughout the developmental stages in both females and males. The distribution patterns of the bacteriocytes were quite similar between B. germanica and B. nipponica, and also among other diverse cockroach species, plausibly reflecting the highly conserved cockroach-Blattabacterium symbiotic association over evolutionary time. Our study lays a foundation to experimentally investigate the origin and the processes of urban pest evolution, on account of possible involvement of microbial associates.

In an attempt to establish an experimental dragonfly model, we developed a laboratory rearing system for the blue-tailed damselfly, Ischnura senegalensis. Adoption of multi-well plastic plates as rearing containers enabled mass-rearing of isolated larvae without cannibalism and convenient microscopic monitoring of individual larvae. Feeding Artemia brine shrimps to younger larvae and Tubifex worms for older larvae resulted in low mortality, synchronized ecdysis, and normal development of the larvae. We continuously monitored the development of 118 larvae every day, of which 49 individuals (41.5%) reached adulthood. The adult insects were fed with Drosophila flies in wet plastic cages, attained reproductive maturity in a week, copulated, laid fertilized eggs, and produced progeny. The final larval instar varied from 9th to 12th, with the 11th instar (56.5%) and the 12th instar (24.2%) constituting the majority. From the 1st instar to the penultimate instar, the duration of each instar was relatively short, mainly ranging from three to 11 days. Afterwards, the duration of each instar was prolonged, reaching 7–25 days for the penultimate instar and 14–28 days for the final instar. Some larvae of final, penultimate and younger instars were subjected to continuous and close morphological examinations, which enabled developmental staging of larvae based on size, shape, and angle of compound eyes and other morphological traits. This laboratory rearing system may facilitate the understanding of physiological, biochemical, and molecular mechanisms underlying metamorphosis, hormonal control, morphogenesis, body color polymorphism, and other biological features of dragonflies.

Bell-shaped ciliates of the subclass Peritrichia, such as Vorticella, Carchesium and Epistylis, are commonly found in freshwater and other aquatic environments, either solitary or colonial. Peritrichs attach to a substratum via a contractile or non-motile stalk, and collect food particles by water current using ciliary rows around the edge of the bell, called the peristome. Some peritrichs are epibiotic and ectocommensalistic associates of aquatic insects and other animals, settling on the surface of their specific hosts. Only a few peritrichs are known to establish a more internal association with their hosts, locating within the preoral cavity or esophagus of water beetles and presumably subsisting on food materials chewed and ingested by the insects. To date, no endoparasitic or endocommensalistic peritrichs have been reported from insects. Host insects reported to date have all been aquatic, and given the aquatic lifestyle of peritrichs, terrestrial hosts have been considered unlikely. In the present study, we report a dense population of bizarre microbes within the gut of a terrestrial insect, and histological, ultrastructural and molecular phylogenetic analyses identified it as a peritrich ciliate. The highly-developed hindgut of the stag beetle Aegus currani contained oval colonial peritrichs connected by branched stalks resembling grape clusters. Each zooid exhibited a reduced peristome without disc, a vestibulum with active ciliary movement inside, and an elongated macronucleus. These features are morphologically reminiscent of but distinct in some respects from those in Operculariella parasitica, known from the esophagus of dysticid diving beetles. Taxonomic, ecological and functional aspects of this gut-dwelling peritrich warrant future study.

Cladobranchian sea slugs are characterized by a number of dorsal projections, called “cerata,” which are presumably involved in such biological functions as kleptocnidal defense, gas exchange, and symbiotic photosynthesis. Here, we investigated the developmental pattern of ceras formation in a cladobranchian, Pteraeolidia semperi, using field-collected individuals at various postembryonic developmental stages. As the body length increased, the total number of cerata increased in a logistic manner, up to 280 per individual. On the dorsal side of the body, the cerata exhibited a conspicuous formation of repeated, laterally-paired clusters, or rows, along the antero-posterior axis of the animals. As the body length increased, the number of ceras rows increased in a logistic manner, reaching a plateau at around 15 rows per individual. Two types of ceras clusters were observed: well-developed ceras clusters forming a glove-like structure with a basal bulge, which tended to be found in larger animals and at the anterior body region, and less-developed ceras clusters without the bulge, which tended to be found in smaller animals and at the posterior body region. Statistical and simulation analyses suggested that bulge formation underlies increased ceras number, even after the plateaued formation of new ceras rows. These results indicate that, in the postembryonic development of P. semperi, the increase of dorsal cerata entails the following processes: (i) increase of the number of ceras rows, (ii) formation of the basal bulge in each ceras cluster, and (iii) increase of the number of cerata per ceras cluster.

Light production by organisms, or bioluminescence, has fascinated not only scientists but also ordinary people all over the world, and it has been especially so in Japan. Here we review the biological information available to date for all luminous terrestrial animals known from Japan, particularly focusing on their diversity and systematics, their biology and ecology in Japan, and putative function and biochemistry of their luminescence. In total 58 luminous terrestrial animals have been described from Japan, which consist of 50 fireflies (Coleoptera: Lampyridae), one glowworm beetle (Coleoptera: Phengodidae), two fungus gnats (Diptera: Keroplatidae), one springtail (Collembola), one millipede (Diplopoda), one centipede (Chilopoda) and two earthworms (Oligochaeta). For all except some firefly species, the DNA "barcode" sequences of a cytochrome oxidase subunit I region are provided. We also introduce how intricately the seasonal appearance and glimmering of luminous insects, in particular those of fireflies, have been interwoven into the culture, art, literature and mentality of Japanese people.

Wolbachia endosymbionts are widespread among insects and other arthropods, often causing cytoplasmic incompatibility and other reproductive phenotypes in their hosts. Recently, possibilities of Wolbachia-mediated pest control and management have been proposed, and the bean beetles of the subfamily Bruchinae are known as serious pests of harvested and stored beans worldwide. Here we investigated Wolbachia infections in bean beetles from the world, representing seven genera, 20 species and 87 populations. Of 20 species examined, Wolbachia infections were detected in four species, Megabruchidius sophorae, Callosobruchus analis, C. latealbus and C. chinensis. Infection frequencies were partial in M. sophorae but perfect in the other species. In addition to C. chinensis described in the previous studies, C. latealbus was infected with two distinct Wolbachia strains. These Wolbachia strains from the bean beetles were phylogenetically not closely related to each other. Among world populations of C. chinensis, some Taiwanese populations on a wild leguminous plant, Rhynchosia minima, exhibited a peculiar Wolbachia infection pattern, suggesting the possibility that these populations comprise a distinct host race or a cryptic species.

Microbiological characterization of gut symbiotic bacteria in a limited number of stinkbugs of the families Acanthosomatidae, Plataspidae, Pentatomidae, Scutelleridae, Parastrachiidae, Alydidae and Pyrrhocoridae has shown symbiotic association with midgut bacteria to be common in phytophagous taxa of these heteropteran insects. Here we investigated the midgut bacterial symbiont of Eucorysses grandis, a stinkbug of the family Scutelleridae. A specific gammaproteobacterium was consistently identified in insects from five different geographic origins. The bacterium was detected in 64 of 64 insects sampled from three host populations. Phylogenetic analyses revealed that the bacterium constitutes a distinct lineage in the Gammaproteobacteria, neither closely related to the gut symbiont of another scutellerid stinkbug, Cantao ocellatus, nor to gut symbionts of other stinkbugs. Diagnostic PCR, in situ hybridization and electron microscopy demonstrated that the bacterium is located extracelluarly, in the midgut fourth section, which possesses crypts. These results indicate that the primary gut symbionts have multiple evolutionary origins in the Scutelleridae. A Sodalis-allied facultative symbiont was also identified in some insects from natural populations. Biological aspects of the primary gut symbiont and the secondary Sodalis-allied symbiont are discussed.

We investigated the endosymbiotic microbiota of the citrus psyllid Diaphorina citri that vectors Liberobacter sp., the causative agent of citrus greening disease. Eubacterial 16S rDNA fragments were amplified by PCR and cloned from the whole DNA of D. citri. RFLP analysis showed that the PCR products contained five major sequence types. Nucleotide sequences of the five types were determined and subjected to molecular phylogenetic analysis. The first sequence was a member of the γ-Proteobacteria, closely related to mycetocyte symbionts of other psyllids. The second sequence belonged to the β-Proteobacteria, related to Oxalobacter and Herbaspirillum. The third sequence, belonging to the γ-Proteobacteria, showed a significant similarity to the sequences of Arsenophonus spp., known as endosymbionts of a triatomine bug and a parasitoid wasp. The fourth sequence was almost identical to the sequences of Liberobacter spp. in the α-Proteobacteria. The fifth sequence showed a high similarity to the sequenc...

Members of the family Bruchidae (Insecta, Coleoptera) were examined for Wolbachia infection. Out of seven species investigated, which represented three subfamilies and five genera, amplified bands were detected only from Callosobruchus chinensis by diagnostic PCR with Wolbachia-specific primers. Bacterial 16S rDNA was amplified by PCR, cloned and sequenced from the total DNA of C. chinensis. Molecular phylogenetic analysis demonstrated that the sequence belongs to a monophyletic group of the genus Wolbachia in the α-Proteobacteria. The Wolbachia was detected from all tissues and body parts such as ovary, gut, fat body, muscle, wing, leg, head and antenna. In six geographic populations from central Japan, all the individuals examined, more than 400 in total, possessed the Wolbachia, indicating high prevalence of Wolbachia among natural populations of C. chinensis.

When pea aphids, Acyrthosiphon pisum, were raised on an artificial diet which mimics the amino acid composition of the total tissue of aphids, their intracellular symbionts in the bacteriocyte gradually decreased in number as the host generation proceeded, accompanied with a decrease of the host's fecundity. It is possible that host sacrificed its symbionts to supplement the artificial diet that is nutritionally deficient. This inevitably incurs aposymbiosis, which will, in turn, lead to the host's sterility, as observed repeatedly.

Giant scale insects (Drosicha: Coccoldea: Monophlebidae) were investigated for their symbiotic organs and bacterial endosymbionts. Two types of bacterial 16S rRNA gene sequences, flavobacterial and enterobacterial, were consistently detected in D. corpulenta and D. pinicola. The former sequences formed a compact clade in the Bacteroidetes, allied to the symbionts of cushion and armored scales. The latter sequences formed a robust clade in the gamma-Proteobacteria, allied to enteric bacteria like Enterobacter aerogenes and Escherichia coli. Another type of 16S sequence derived from Wolbachia was also detected in D. pinicola. In-situ hybridization demonstrated that the flavobacterial and enterobacterial symbionts were localized in a pair of huge bacteriomes in the abdomen, the former in uninucleated peripheral bacteriocytes and the latter in syncytial central bacteriocytes. Electron microscopy confirmed the endocellular locations of the pleomorphic flavobacterial symbiont and the rod-shaped enterobacterial symbiont, and also revealed the location and fine structure of the Wolbachia symbiont in D. pinicola. Infection frequencies of the flavobacterial and enterobacterial symbionts were consistently 100% in populations of D. corpulenta and D. pinicola, while the Wolbachia symbiont exhibited 0% and 100% infection frequencies in D. corpulente and D. pinicola, respectively. Neither the flavobacterial symbiont nor the enterobacterial symbiont exhibited AT-biased nucleotide composition or accelerated molecular evolution. The huge bacteriomes of Drosicha giant scales would provide a useful system for investigating biochemical, physiological, and genomic aspects of the host-symbiont and symbiont-symbiont interactions.