The habitat of the cockroach varies by species. The German cockroach (Blattella germanica) lives in human dwellings, while the Japanese field roach (Blattella nipponica) lives in a mountainous region. Based on phylogenetic analysis of mtCO I, the two species are closely related to each other and B. germanica is divergent from wild species such as B. nipponica. Their habitats and walking speed differ even though the two species have similar morphology. We hypothesized that habitats might influence walking speed via changes to appendage morphology and enzyme-based physiological differences. We found that phenotype such as appendage length and esterase isozyme expression were clearly different between the two species. These differences might be responsible for the observed difference in walking speed.

The habitat of the cockroach varies relative to species. The German cockroach (Blattella germanica) lives in human dwelling while B. nipponica lives in mountainous region. Even though, these two species have similar morphology, their habitats and walking speed were different. Underlying this fact, we hypothesized that habitats might influence on the walking speed via altering particularly nervous system including acetylcholinesterase (EC3.1.1.7, AChE). Full length ORFs were cloned from each species and sequenced. Sequence analyses showed that both genes in each species possess typical features of ace, and that Bgace1 and Bnace1. Those features are orthologous to the insect ace1 whereas Bgace2 and Bnace2 are to the insect ace2. Some SNPs were observed but Bgace1 and 2 showed high similarity (99%) with Bgace1 and 2, respectively. Multiple AChE bands were identified by native PAGE and IEF from three tissues (head, leg and other body) and their expression pattern was almost identical between two species. However, Esterase expression patterns were significantly different. Furthermore, length as well as detailed structure of antenna, leg and tail cerci was also significantly different. Taken together, various factors such as sensory organ detailed morphology and esterases are responsible for habitat and walking speed difference.