Reevaluating Symbiotic Digestion in Cockroaches: Unveiling the Hindgut's Contribution to Digestion in Wood-Feeding Panesthiinae (Blaberidae).

Cockroaches of the subfamily Panesthiinae (family Blaberidae) are among the few major groups of insects feeding on decayed wood. Despite having independently evolved the ability to thrive on this recalcitrant and nitrogen-limited resource, they are among the least studied of all wood-feeding insect groups. In the pursuit of unraveling their unique digestive strategies, we explored cellulase and xylanase activity in the crop, midgut, and hindgut lumens of Panesthia angustipennis and Salganea taiwanensis. Employing Percoll density gradient centrifugation, we further fractionated luminal fluid to elucidate how the activities in the gut lumen are further partitioned. Our findings challenge conventional wisdom, underscoring the significant contribution of the hindgut, which accounts for approximately one-fifth of cellulase and xylanase activity. Particle-associated enzymes, potentially of bacterial origin, dominate hindgut digestion, akin to symbiotic strategies observed in select termites and passalid beetles. Our study sheds new light on the digestive prowess of panesthiine cockroaches, providing invaluable insights into the evolution of wood-feeding insects and their remarkable adaptability to challenging, nutrient-poor substrates.

Rapid flower closure of Drosera tokaiensis deters caterpillar herbivory.

Certain plants exhibit rapid movement in response to mechanical stimulation; however, the ecological functions of this behaviour are largely unknown. Here, we show that the rapid flower closure of Drosera tokaiensis (Droseraceae) in response to mechanical stimulation functions as a physical defence against a specialist herbivore Buckleria paludum (Pterophoridae) caterpillar. Following feeding damage on fruits, flowers, flower stalks and buds by B. paludum, D. tokaiensis closed its flowers nine times faster than during natural circadian closure. The extent of damage to ovules was significantly reduced when the flowers were able to close compared with the condition in which closure was physically inhibited by the application of a resin. Nonetheless, flower closure had no effect on the feeding damage to stamens and styles and promoted further damage to petals. Given that feeding on petals, stamens and styles had no significant effect on the number of mature seeds, rapid flower closure leading to the protection of ovules had an overall positive effect on the reproductive success of D. tokaiensis. Our study showed rapid plant movement as a novel case of induced physical defence against herbivory.