Review of the Gross Anatomy and Microbiology of the Phasmatodea Digestive Tract

Abstract

Abstract The sparse descriptions of the stick insect (Phasmatodea) digestive system as reported/provided in the literature are highly contradictory. This paper describes the digestive systems of several families of Phasmatodea (Timematidae, Heteropterygidae, Diapheromeridae, Pseudophasmatidae, and Phasmatidae) plus the gut microbiome of these and one other (Phylliidae) to both verify past findings and provide a general description of the Phasmatodea alimentary canal. The constrictions imposed by this anatomy on phasmid gut microbiology, its connections to recently released Phasmatodea transcriptomes, and how it differs from the anatomy of related orders in the Polyneoptera are discussed. All Phasmatodea have ridged proventriculi lined or covered with small spines. Anterior projections of the midgut, sometimes described as gastric caeca, are only found in Euphasmatodea and often obscure the proventriculus. We define the cardia as the complex of foregut and midgut tissue where the type II peritrophic matrix...