Contact with water functions as a Zeitgeber for the circatidal rhythm in the mangrove cricket Apteronemobius asahinaiThe mangrove cricket Apteronemobius asahinai shows a circatidal rhythm in its locomotor activity, and this rhythm was shown to be entrained to artificial tidal cycles in the laboratory. To examine the Zeitgeber for this rhythm, in the present study, crickets were fixed with insect pins to prevent their body locomotion and a water stimulus was given to them by soaking in water while recording their locomotor activities. A single water stimulus delayed the phase when given in the middle subjective low tide and advanced the phase when given in the later subjective low tide, whereas it had only a slight effect in the subjective high tide.We conclude that contact with water functions as a Zeitgeber for the circatidal rhythm.

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Beetles are the largest insect order and one of the most successful animal groups in terms of number of species. The Japanese rhinoceros beetle Trypoxylus dichotomus (Coleoptera, Scarabaeidae, Dynastini) is a giant beetle with distinctive exaggerated horns present on the head and prothoracic regions of the male. T. dichotomus has been used as research model in various fields such as evolutionary developmental biology, ecology, ethology, biomimetics, and drug discovery. In this study, de novo assembly of 615 Mb, representing 80% of the genome estimated by flow cytometry, was obtained using the 10x Chromium platform. The scaffold N50 length of the genome assembly was 8.02 Mb, with repetitive elements predicted to comprise 49.5% of the assembly. In total, 23,987 protein-coding genes were predicted in the genome. In addition, de novo assembly of the mitochondrial genome yielded a contig of 20,217 bp. We also analyzed the transcriptome by generating 16 RNA-seq libraries from a variety of tissues of both sexes and developmental stages, which allowed us to identify 13 co-expressed gene modules. The detailed genomic and transcriptomic information of T. dichotomus is the most comprehensive among those reported for any species of Dynastinae. This genomic information will be an excellent resource for further functional and evolutionary analyses, including the evolutionary origin and genetic regulation of beetle horns and the molecular mechanisms underlying sexual dimorphism.

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