How does a tick swell after feeding? - briefly
The tick’s abdomen inflates dramatically as it absorbs the host’s blood, stretching the cuticle and allowing internal tissues to accommodate the sudden volume increase. This engorgement can raise the animal’s mass several hundred‑fold within a few days.
How does a tick swell after feeding? - in detail
After a blood meal, a tick undergoes rapid enlargement known as engorgement. The process begins when the mouthparts pierce the host’s skin, creating a feeding canal that remains open for several days. Salivary secretions contain anticoagulants, vasodilators, and immunomodulatory proteins, allowing uninterrupted blood flow into the gut lumen.
The ingested blood is stored in the midgut, where it is mixed with digestive enzymes. Osmotic pressure within the gut rises, drawing water from the haemolymph into the lumen. This influx of fluid expands the gut wall, which is highly elastic due to a flexible cuticular matrix composed of chitin and protein cross‑links. As the gut stretches, the entire body cavity enlarges, producing the characteristic spherical shape of a fully fed tick.
Hormonal regulation coordinates the swelling. Elevated levels of the neuropeptide bursicon trigger cuticle softening, while insulin‑like peptides stimulate nutrient uptake and storage. Simultaneously, the tick’s excretory system, the Malpighian tubules, reduces water loss by reabsorbing ions, concentrating the remaining fluid within the gut.
Engorgement culminates in a dramatic increase in mass, often exceeding the unfed weight by 100‑ to 200‑fold. Structural adaptations supporting this change include:
- A highly extensible cuticle with reduced sclerotization in the posterior abdomen.
- Muscular layers that relax to accommodate volume expansion.
- A reinforced ventral shield that protects internal organs during rapid growth.
After detachment, the tick gradually reduces its size as excess water is excreted and stored nutrients are metabolized for egg development in females or for overwintering in males. The entire sequence ensures efficient acquisition of host blood while maintaining physiological stability throughout the feeding period.