No abstract

Sociality may affect symbiosis and vice versa. Many plant-sucking stinkbugs harbor mutualistic bacterial symbionts in the midgut. In the superfamily Pentatomoidea, adult females excrete symbiont-containing materials from the anus, which their offspring ingest orally and establish vertical symbiont transmission. In many stinkbug families whose members are mostly non-social, females excrete symbiont-containing materials onto/beside eggs upon oviposition. However, exceptional cases have been reported from two subsocial species representing the closely related families Cydnidae and Parastrachiidae, wherein females remain nearby eggs for maternal care after oviposition, and provide their offspring with symbiont-containing secretions at later stages, either just before or after hatching. These observations suggested that sociality of the host stinkbugs may be correlated with their symbiont transmission strategies. However, we found that cydnid stinkbugs of the genus Adomerus, which are associated with gammaproteobacterial gut symbionts and exhibit elaborate maternal care over their offspring, smear symbiont-containing secretions onto eggs upon oviposition as many non-social stinkbugs do. Surface sterilization of the eggs resulted in aposymbiotic insects of slower growth, smaller size and abnormal body coloration, indicating vertical symbiont transmission via egg surface contamination and presumable beneficial nature of the symbiosis. The Adomerus symbionts exhibited AT-biased nucleotide compositions, accelerated molecular evolutionary rates and reduced genome size, while these degenerative genomic traits were less severe than those in the symbiont of a subsocial parastrachiid. These results suggest that not only sociality but also other ecological and evolutionary aspects of the host stinkbugs, including the host-symbiont co-evolutionary history, may have substantially affected their symbiont transmission strategies. (250 words).

Highlights d During the hatching of a stink bug, egg cracking generates a single pulsed vibration d Fully developed embryos immediately start hatching when receiving the vibration d The vibration widely spreads across a clutch and induces its explosive hatching d Synchronized hatching crucial for survival is achieved using the vibration as a cue

No abstract

Hatching care has been reported for many taxonomic groups, from invertebrates to vertebrates. The sophisticated care that occurs around hatching time is expected to have an adaptive function supporting the feeble young. However, details of the characteristics of the adaptive function of hatching care remain unclear. This study investigated the hatching care of the subsocial shield bug, Parastrachia japonensis (Heteroptera: Parastrachiidae) to verify its function. Results show that the P. japonensis mothers vibrated the egg mass intermittently while maintaining an egg-guarding posture. Then embryos started to emerge from their shells synchronously. Unlike such behaviors of closely related species, this vibrating behavior was faint, but lasted more than 6 h. To investigate the effect of this behavior on hatching synchrony and hatching success, we observed the hatching pattern and the hatching rate in control, mother-removed, and two artificial vibration groups. Control broods experienced continuous guarding from the mother. Intermittent artificial vibration broods were exposed to vibrations that matched the temporal pattern of maternal vibration produced by a motor. They showed synchronous hatching patterns and high hatching rates. However, for mother-removed broods, which were isolated from the mother, and when we provided continuous artificial vibration that did not match the temporal pattern of the maternal vibration, embryo hatching was not only asynchronous: some embryos failed to emerge from their shells. These results lead us to infer that hatching care in P. japonensis has two functions: hatching regulation and hatching assistance. Nevertheless, several points of observational and circumstantial evidence clearly contraindicate hatching assistance. A reduction in the hatching rate might result from dependence on maternal hatching care as a strong cue in P. japonensis. We conclude that the hatching care of P. japonensis regulates the hatching pattern and serves as an important cue to induce embryo hatching.

Subsociality involving provisioning for offspring has been reported for one shield bug and three burrower bug species (Hemiptera: Pentatomoidea: Parastrachiidae and Cydnidae: Sehirinae). We present the first report of subsocial behaviour in the burrower bug Adomerus variegatus (Signoret), focusing on manifestations of maternal care, specifically the production of trophic eggs, guarding of offspring, and progressive provisioning. In our study, each female produced an egg mass that included some trophic eggs. Prior to nymphal hatch, females remained in their nests and showed egg mass guarding behaviour. Mothers started provisioning behaviour a few hours after nymphal hatch. Each mother dragged a seed (larger than her body) with her proboscis to the nest as food for the nymphs. These findings suggest that A. variegatus shows maternal-care behaviours similar to those reported in some other pentatomoid species and that trophic egg production and nest provisioning have evolved as interrelated processes.

(within 250 words)Hemipteran insects use sophisticated vibrational communications by striking body appendages to the substrate or by oscillating the abdominal tymbal. There has been, however, little investigation of sensory channels for processing vibrational signals.Using sensory nerve stainings and low invasive confocal analyses, we demonstrate the comprehensive neuronal mapping of putative vibration-responsive chordotonal organs

Numerous organisms integrate information from multiple sources and express adaptive behaviours, but how they do so at different developmental stages remains to be identified. Seeds, which are the embryonic stage of plants, need to make decisions about the timing of emergence in response to environmental cues related to survival. We investigated the timing of emergence of (Plantaginaceae) seed while manipulating the presence of seed and the relatedness of neighbouring seed. The relatedness of neighbouring seed and the presence of seeds of did not on their own influence the timing of emergence. However, when encountering a seed, a seed emerged faster in the presence of a sibling seed than in the presence of a non-sibling seed. Water extracts of seeds gave the same result. We show that seeds integrate information about the relatedness of neighbouring seeds and the presence of seeds of a different species via water-soluble chemicals and adjust their emergence behaviour in response. These findings suggest the presence of kin-dependent interspecific interactions.