How to determine a tick’s sex? - briefly
Sex is identified by the shape of the ventral genital aperture: males have a narrow, pointed «gonopore», while females possess a broader, rounded opening. Additionally, a complete dorsal «scutum» indicates a male, whereas females display a partial «scutum».
How to determine a tick’s sex? - in detail
Identifying the sex of a tick requires examination of morphological structures that differ between males and females. The most reliable characters are visible on the ventral side of the idiosoma and on the dorsal scutum in adult stages.
In adult specimens, the genital aperture is located anterior to the anal groove. In males, the aperture appears as a shallow, elongated slit bordered by a pair of sclerotized plates. In females, the opening is a wider, rounded pore without distinct bordering plates. Observing these features under a stereomicroscope at 40–60 × magnification provides clear discrimination.
The scutum also displays sexual dimorphism. Male ticks possess a fully developed, hard scutum that covers the entire dorsal surface, often with pronounced punctations and a distinct pattern of spiracular plates. Female ticks have a reduced, soft scutum limited to the anterior portion, leaving the posterior dorsum uncovered to accommodate engorgement. The presence of a complete dorsal shield therefore indicates a male, while a partial shield signals a female.
Additional characters assist in confirmation:
- Presence of copulatory spurs on the legs: males exhibit small, hook‑like extensions on the first pair of legs; females lack these structures.
- Size of the anal groove: males typically show a narrower groove; females display a broader, more pronounced groove.
- Engorgement state: heavily distended bodies are almost exclusively female, as males do not feed to the same extent.
When external morphology is ambiguous, especially in nymphal stages, molecular methods provide definitive results. Polymerase chain reaction targeting sex‑specific markers, such as the Y‑linked gene in species with heterogametic males, yields a binary outcome. DNA extraction from a single leg or the opisthosoma, followed by amplification with primers described in recent acarological studies, distinguishes male from female genetic material with high accuracy.
A practical workflow for sex determination:
- Place the tick on a clean slide, ventral side up.
- Examine the genital aperture and scutum under a stereomicroscope.
- Record the presence or absence of a complete dorsal shield and copulatory spurs.
- If morphological traits are inconclusive, extract DNA and perform PCR with sex‑specific primers.
- Interpret the PCR result: amplification of the Y‑linked fragment confirms a male; absence indicates a female.
Accurate sex identification supports ecological research, vector competence assessments, and control strategies.