How does a tick's body inflate after feeding? - briefly
After ingesting blood, the tick’s midgut expands, stretching the cuticle and causing the abdomen to swell dramatically. The cuticle’s flexible, expandable structure accommodates the increased volume without rupturing.
How does a tick's body inflate after feeding? - in detail
Ticks undergo a rapid increase in body volume once a blood meal begins. The process can be divided into several coordinated phases.
During the initial attachment, the mouthparts pierce the host’s skin, allowing the tick to insert its hypostome. Salivary secretions containing anticoagulants and immunomodulatory compounds keep the feeding site open and prevent clotting. This creates a continuous flow of blood into the foregut.
The ingested blood is stored in the midgut, where the cuticle of the abdomen is highly extensible. Specialized elastic proteins and a multilayered cuticular matrix permit the exoskeleton to stretch without rupturing. As the volume rises, the hemolymph pressure inside the body cavity increases, further expanding the cuticle.
Hormonal signals, primarily the neuropeptide crustacean cardioactive peptide (CCAP) and the insulin‑like peptide (ILP) family, trigger muscle relaxation and cuticular softening. These hormones also stimulate the production of cuticular proteins that reinforce the expanded exoskeleton, preventing over‑extension.
Water balance is regulated by a rapid diuretic phase. Malpighian tubules excrete excess water and ions, concentrating the ingested blood into a protein‑rich meal. This concentration reduces overall mass while maintaining nutrient density, allowing the tick to reach a size up to 100 times its unfed volume.
The final stage involves the sealing of the feeding cavity. Muscular contraction of the cheliceral muscles compresses the foregut, and a cement‑like secretion from the salivary glands solidifies around the attachment site, preventing loss of the engorged blood.
Key mechanisms:
- Anticoagulant‑rich saliva maintains blood flow.
- Elastic cuticle permits dramatic abdominal expansion.
- Neurohormonal regulation relaxes muscles and softens cuticle.
- Diuresis concentrates the meal, reducing mass.
- Cement secretion secures the engorged state.
These coordinated physiological and biochemical processes enable ticks to achieve extreme body enlargement within a short feeding interval.