A Comparative Study Of The Alimentary Canal Morphology And Cellulase In Eucryptorrhynchus Scrobiculatus And E. Brandti

Eucryptorrhynchus scrobiculatus and E. brandti are the mainly borers on a native tree species Ailanthus altissima and its variety. They can parasitize on A. altissima at the same time but occupy different ecological niches. It’s highly possible that their feeding sites are different, too. In the view of morphology and psychology, the study not only compared the integral and microscopic morphological characters, but also determined the primary digestive enzyme cellulase. Thus to give a better understanding of the differences in the digestive mechanism in adult. Below are the results,1. The alimentary canals of E. scrobiculatus and E. brandti can be divided into 3 parts, foregut (stomodeum), midgut (mesenteron) and hindgut (proctodeum). The tract length of E. scrobiculatus is almost as doubled as that in E. brandti; but the body length of the E. scrobiculatus is 1.5 times of that in E. brandti (the body length and tract length ration in E. scrobiculatus is 2.70, and in E. brandti is 2.34).2. Foregut:Crop is absent in both species. Proventriculus is the hardest section of the whole tract, functions as gizzard. Inside the proventriculus, there are masticatory brushes and "V" shaped chitinous plates. The "V" shaped chitinous plates are trimly piled in 8 rows, and disposed row by row as an 8 pointed star look from transection. The masticatory brushes in E. scrobiculatus are long and thin, the brush region occupies about 40% of the total length of the proventriculus; while in E. brandti the number is decreased to around 25%-30%, and the brushes are shorter.3. Midgut:The midgut is composed of anterior midgut and posterior midgut. There are columnar cells and regenerative cells in the anterior midgut epithelium. Digestive enzymes are produced and secreted by columnar cells. Apocrine and holocrine secretions were observed in the anterior midgut of E. brandti. The regenerative cells cluster on the outer side of the gut wall or should say in the basal epithelium. Regenerative cells have strong renewability and compensate the cell loss of secretion. The cell layer wrinkles like tiny waves and encircles the gut lumen. So the gut is very flexible in volume and can store food to be digest temporarily. The peritrophic membrane present in both species. Posterior midgut is a constrict region on midgut. There are a lot gastric caeca. Every gastric caecum is a single cell layer sac, possibly involved in the nutrient absorption.4. Hindgut:The hindgut starts from the malpiphian tubes.6 malpiphian tubes can be found in both species. The malpiphian tubes arranged in 2 groups, one group with 2, the other with 4. In the E. scrobiculatus, there is no distinct difference between male and female. And the malpiphian tubes in male adults of E. brandti are resemble to those in E. scrobiculatus.2 types of malpiphian tubels are observed in the female E. brandti, and both of them are different from the male. This might due to the sex pheromones secretion. Numerous structures like crater located on the outer surface of the rectum. The space between these structures is not the same in these 2 species, a wider space was found in E. scrobiculatus.5. Cellulase activity:In E. scrobiculatus, cellulase in male is obviously higher than that in female, this may due to the different mobility in gender. But there is no significant difference between male and female in E. brandti when two gender have almost the same mobility. The tiny difference can be explained by the different sizes in gender. Besides, cellulase in E. brandti is remarkably higher than E. scrobiculatus, this is consistent with the observation that E. scrobiculatus prefer to feed on the tender phloem which has lower cellulose on young generation.