What does a tick's abdomen look like? - briefly
The tick’s abdomen is a rounded, often oval segment located behind the mouthparts, appearing smooth and slightly flattened when unfed and becoming markedly swollen, balloon‑like, and semi‑translucent after a blood meal. Its color shifts from pale tan to a reddish‑brown or bluish hue as it fills with blood.
What does a tick's abdomen look like? - in detail
The abdomen, or opisthosoma, occupies the rear two‑thirds of a tick’s body and is a soft, expandable sac that houses the digestive tract, reproductive organs, and blood‑storage tissues. In unfed specimens, it appears flat, oval‑shaped, and pale‑brown to reddish‑brown, with a smooth or slightly granulated surface. The dorsal shield (scutum) ends before the abdomen, leaving the latter uncovered and flexible.
When a tick feeds, the abdomen expands dramatically, becoming spherical or balloon‑like and often turning a deep, engorged red or blue‑gray. The cuticle stretches, revealing fine wrinkles that radiate from the center. Engorgement can increase the abdomen’s volume up to 100‑fold, making it the dominant visual feature.
Key visual characteristics include:
- Segmentation: Visible as faint transverse lines or sutures in some species, especially in the ixodid family.
- Color variation: Species‑specific hues range from light tan in Ixodes to darker brown in Dermacentor; engorged individuals may display a uniform darkening.
- Surface texture: Unfed abdomens are smooth; after feeding, the cuticle shows pronounced striations and occasional tiny pores where saliva was secreted.
- Shape change: From flattened and oval in the questing stage to a rounded, balloon‑like form during and after blood intake.
The ventral side presents a softer, membranous surface with visible internal organs, especially the gut filled with blood. In male ticks, the abdomen remains relatively small and less engorged, retaining a more elongated shape compared to the markedly swollen females.