Fig. 3: Internal spiracle structure of E. horridus. | Communications Biology

Fig. 3: Internal spiracle structure of E. horridus.

From: The ectoparasitic seal louse, Echinophthirius horridus, relies on a sealed tracheal system and spiracle closing apparatus for underwater respiration

Fig. 3

A–D Histological sections stained with toluidine blue. A Spiracle opening with atrium showing spinous processes close to the connection to the trachea. B Cuticular plug showing flap-like structure and different staining properties than remaining cuticle. C Cuticular rod extending to the atrio-tracheal transition. Also shown are the prominent occlusor muscles. D Distal area of the trachea showing spinous processes and also visible the atrial tube. E Schematic drawing of the internal spiracle structures. F 3D reconstruction of the internal spiracle structures. Muscles are shown in red and prominent cuticular structures in green/turquoise. Abbreviations: at (atrium), atr (atrial cuticular ridge), att (atrial tube), cp (cuticular plug), cr (cuticular rod), ocl (occlusor muscle), sp (spiracle), tr (trachea).

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