Morphological Description and Physiological Changes in the Hindgut of Female Asiophrida xanthospilota (Chrysomelidae, Coleoptera) Across Reproductive Stages

Fecal retention is a distinctive reproductive strategy in certain leaf beetles, which enables females to use accumulated fecal material to protect their eggs and enhance offspring survival. The adult flea beetle Asiophrida xanthospilota (Baly, 1881) is a specialist herbivore that feeds on the leaves of Cotinus coggygria Scop. (Anacardiaceae). Using light microscopy, scanning electron microscopy, and micro-computed tomography, we described and illustrated the hindgut anatomy of adult female A. xanthospilota during the pre-mated and post-mated reproductive phases. We further examined the physiological changes in the hindgut associated with fecal retention, and assessed hindgut muscle activity across these two reproductive stages. The hindgut of adult A. xanthospilota consists of three regions: ileum, colon, and rectum. The ileum is a thin, straight or coiled, tube enclosed by malpighian tubules and supported by circular and longitudinal muscles. The colon lies between the ileum and rectum, possesses a chitinized cuticle, and is externally covered with tracheae and tracheoles. A rectal valve separates the colon from the rectum, which forms the posterior end of the alimentary canal and is characterized by intimal spines and robust circular muscles. During the post-mated phase, fecal retention causes pronounced dilation of the hindgut, substantially increasing the volume occupied by food remnants. Electromyographic recordings revealed high hindgut muscle activity in pre-mated females, characterized by short and variable bursts, whereas post-mated females exhibited reduced activity with longer and more sustained bursts. The functional implications of these specialized structural features are discussed. Overall, these morphological and physiological adaptations enhance the fecal retention strategy by increasing fecal capacity, regulating hindgut motility, and enabling the formation of a protective fecal case around the egg mass.