Fig. 3: External morphology and internal anatomy of wall-pore sensilla in Pisaura mirabilis.

A–D SEM and E–I TEM. A An overview of a wall-pore sensillum with a curved-tapered shaft and round socket. B Close-up image of the middle region of the sensillum shaft showing a grooved and ridged surface with multiple pore-like depressions (some are indicated by white arrows) located within the grooves. C A broken shaft revealing the hollow center (lymph space) of the sensillum. D Socket (so) of the sensillum with a nonporous, finely ribbed base. E Cross-section of the tip region of the sensillum shaft showing wall pores (black arrows) in the shaft wall cuticle (swc). The outer lymph space (osl) and inner lymph space (isl) are separated by a dendritic sheath (ds).  Dendrites are not clearly discernible. Longitudinal canals (lc) are present in the shaft wall cuticle. F Spoke canals (sc) (marked with white arrows) in the shaft wall cuticle connect the outer environment to the lymph spaces. Some partially disintegrated dendrites (de) of receptor cells are visible in the inner lymph space. A longitudinal canal is present in the shaft wall cuticle. G Cross-section of the mid-region of the sensillum shaft, showing pores connected to the lymph space via spoke canals. Two chemoreceptive dendrites (de) are visible in the inner lymph space. H Cross-section of the basal region of the sensillum shaft showing four dendrites (de) enclosed by the dendritic sheath. The longitudinal canals are mostly fused and form a compact ring-like structure. I Close-up of the basal region of the sensillum shaft in cross-section, highlighting four dendrites in the inner lymph space. The outer lymph space contains cytoplasmic projections of accessory sheath cells (pasc).