Insect cuticular extracellular matrices (ECM) including the eggshell and exoskeleton play vital roles in protecting them from natural environmental stresses. However, these chitinous ECMs must be degraded at least in part during embryonic and post-embyonic molting periods to accommodate continuous growth all the way to the adult stage. In this study we investigated the functions of groups I and II chitinases, TcCHT5 and TcCHT10, in turnover of the eggshell and cuticle in Tribolium castaneum. RNAi and TEM analyses revealed that TcCHT10 is required for digestion of chitin in the serosal cuticle for embryo hatching as well as in the old cuticle during post-embryonic molts including larval-pupal and pupal-adult metamorphosis. However, although TcCHT5 is apparently involved in these vital physiological events, TcCHT10 could substitute for TcCHT5 except during the pupal-adult molting when both enzymes are indispensable to degrade chitin in the old pupal cuticle.

Hatching occurred in the time dependent manners and strictly controlled. Although, the hatching processes are under the control of muti-embryotrophic factors and the expressed G proteins of cell generate integrated activation, the knowledge which GPCRs are expressed during hatching stage embryos are very limited. In the present study, which G proteins are involved was examined during blastocyst development to the hatching stage. The early-, expanded-, and lobe-stage blastocysts were treated with various activators and H series inhibitors, and examined developmental patterns. Pertusis toxin (PTX) improved the hatching rate of the early-stage blastocyst and lobe-formed embryos. Cholera toxin (CTX) suppressed the hatching of the early-stage blastocyst and expanded embryos. The effects of toxins on hatching and embryo development were changed by the H7 and H8. These results mean that PTX mediated GPCRs activation is signaling generator in the nick or pore formation in the ZP. In addition, PTX mediated GPCR activation induces the locomotion of trophectoderm for the escaping. CTX mediate GPCRs activation is the cause of suppression of hatching processes. Based on these data, it is suggested that various GPCRs are expressed in the periimplantation stage embryos and the integration of the multiple signals decoding of various signals in a spatial and temporal manner regulate the hatching process.