Table 1 Comparative summary of external morphology, internal anatomy, and distribution of tip-pore and wall-pore sensilla in Pisaura mirabilis

Shaft and socket external morphology

Occurrence

Both sexes; on all walking legs and pedipalps

Adult males only; on all walking legs

Shape

Slightly S-shaped; blunt tip (Fig. 1A)

Curved with tapered tip (Fig. 3A)

Shaft surface

Finely vertically ribbed shaft base (Fig. 1C, D), strongly ribbed medially and distally, ribs carry spirally arranged microtrichia (Fig. 1A); shallow longitudinal grooves at tip (Fig. 1B)

Finely vertically ribbed shaft base (Fig. 3C, D), fine diagonal ridges medially and distally (Fig. 3B); longitudinal grooves with numerous wall pores (Fig. 3B)

Pore type and location

Single oval pore (400–700 nm diameter) at tip

Numerous wall pores (~42 nm diameter) along the shaft, except at the base

Socket

Circular, slightly elevated crater-like socket (Fig. 1D)

Circular, slightly elevated crater-like socket (Fig. 3D)

Average length

♂: ~175 µm; ♀: ~188 µm

♂:~142 µm

Average diameter

♂: ~6 µm, ♀: ~6.5 µm;

♂:~2 µm

Shaft and socket internal anatomy

Location examined

Femur of 1st walking leg (males and females) (Fig. 2B)

Femur of 1st walking leg (males only) (Fig. 2B)

Shaft cross-profile

Star-shaped (mid-shaft, Fig. 1E); circular (base, Fig. 1F)

Circular; finely corrugated (Fig. 3E–G)

Shaft wall features

Double-walled appearance with longitudinal shaft canals (e.g., Fig. 1E)

Double-walled appearance with longitudinal shaft canals (Fig. 3F, G)

Longitudinal shaft canals

Present; partly coherent (Fig. 1E-F), connected with the outer sensillum lymph space at the shaft base

Present; dispersed (Fig. 3E, G), connected to outer sensillum lymph space at shaft base; not connected with radial spoke canals (Fig. 3F)

Sensillum lumen

Hollow (Fig. 1C), filled with lymph; separated into inner and outer sensillum lymph spaces (e.g., Fig. 1F)

Hollow, filled with lymph; separated into inner and outer sensillum lymph spaces (Fig. 3F)

Outer lymph space

Present; surrounds inner lymph space; contains sheath cell processes (Fig. 1F)

Present; surrounds inner lymph space; contains sheath cell processes (Fig. 3I)

Distal processes of accessory sheath cells

Present in the outer sensillum lymph space (Fig. 1F); continuing to the tip region

Present in the outer sensillum lymph space (Fig. 3I); continuing to the tip region

Inner lymph space

Present; enclosed by a continuous dendritic sheath (proximal shaft region, Fig. 1G) and peridendritic shaft cylinder (median and distal shaft region, Fig. 1F)

Present; enclosed by a continuous dendritic sheath (Fig. 3E–I)

Number of dendrites

15–18 dendrites (Fig. 1E, G)

2–4 (mostly 4, Fig. 3I) dendrites

Spoke canals (pore canals)

Not present

Present; connect wall pores with outer sensillum lymph space; no contact with longitudinal canals (Fig. 1F), ~100 nm diameter

Mechanoreceptive structures

Present; 2 tubular bodies at the socket region (multimodal sensillum)

Absent; no tubular bodies; not multimodal

Distribution

Total number

♂: ~4100; ♀: ~2900 sensilla

♂: ~3000 sensilla

Leg segments with sensilla

All segments except trochanter (Fig. 2B)

Only on segments: femur, patella, tibia (Fig. 2B)

Most abundant on

Tarsus, metatarsus, tibia (Fig. 2B)

Femur, patella, tibia (Fig. 2B)

On pedipalps

Present mostly on distal segments (Fig. 2A)

Absent

On walking legs

Present on all legs; arranged in 7–8 rows, mostly on lateral and ventral surfaces (Fig. 2B)

Present on all legs; irregularly arranged; mostly on lateral surfaces (Fig. 2B)