Respiratory system of arachnids I: morphology of the respiratory system ofSalticus scenicus and Euophrys lanigera (Arachnida, Araneae, Salticidae)

The book-lungs and the tracheal systems of two species of jumping spider, S alticus scenicus and Euophrys lanigera. were investigated using gross anato mical, light and electron microscopic methods. Both species possess well-de veloped book-lungs of similar size and tracheal systems with a basically si milar branching pattern. The tracheal spiracle opens into a single atrium, where it gives rise to four thick 'tube tracheae', from which small seconda ry tube tracheae originate in groups. The secondary tracheas (diameter 1-5 mum) run parallel, without further branching, into the prosoma. In the opis thosoma, they lie ventrolaterally, where they contact muscles and internal organs. In the prosoma, the secondary tracheae may penetrate the gut epithe lium and central nervous tissue. The structure of the tracheal walls is ver y similar to that of insects, consisting of a striated inner cuticular laye r with taenidial structures and a surrounding outer hypodermal layer. The w all thickness appears similar in all secondary tracheae, indicating that la teral gas diffusion may be possible through the walls of all small tube tra cheae. (C) 2000 Elsevier Science Ltd. All rights reserved.