"Movement" - what is it, definition of the term
«Movement» denotes the observable alteration of an organism’s spatial coordinates as time progresses, encompassing linear displacement, angular shift, and complex trajectories. In arthropods such as ticks, insects, lice, and fleas, this phenomenon manifests through crawling, hopping, or host‑directed locomotion, driven by muscular contraction and sensory cues that enable the transition from one substrate to another, allowing the parasites to locate resources, evade threats, or complete life‑cycle stages.
Detailed information
Locomotion among ectoparasitic arthropods varies according to anatomical adaptations and host‑seeking strategies.
Ticks employ a “questing” posture, extending forelegs to detect carbon dioxide and heat. When a host contacts the raised legs, the tick anchors with its claws and crawls across the host’s surface. Typical crawling speed ranges from 0.5 mm s⁻¹ to 1 mm s⁻¹, allowing traversal of several meters on vegetation before attachment.
True bugs, such as bed‑bugs, rely on six well‑developed legs for rapid, short‑range movement. They can navigate vertical and horizontal surfaces, exploiting crevices and fabric folds. Walking speed averages 0.4 mm s⁻¹, while occasional bursts reach 1 mm s⁻¹, facilitating quick escape from disturbances.
Lice possess specialized claws that grip hair shafts, enabling continual clinging while moving. Their locomotor pattern consists of incremental steps, covering approximately 1 cm per minute along the host’s integument. Muscular coordination permits rapid adjustments when the host grooms or bends.
Fleas exhibit a dual system: walking and powerful jumping. Muscular contraction stores elastic energy in the protein resilin, releasing it to achieve jumps up to 120 mm—over 100 times body length. Walking speed remains modest, about 0.6 mm s⁻¹, but the jumping mechanism provides efficient host acquisition across gaps.
Key morphological features influencing displacement include:
- Leg segmentation and joint articulation (ticks, bugs, lice)
- Claw curvature and setae density (lice)
- Resilin‑rich tibial plates for elastic recoil (fleas)
Sensory inputs—thermal, olfactory, and vibratory cues—integrate with motor output to direct movement toward potential hosts. The combination of structural design and stimulus response defines each species’ capacity to locate and remain on suitable hosts.