First Report of Morphological Anomalies in Haemaphysalis megaspinosa Ticks from Japan

Morphological anomalies in ticks have been described in various species. Gynandromorphism, asymmetry, and lack of legs are well documented anomalies worldwide. However, only two cases have been reported in Japan. Furthermore, few studies have documented anomalies which could impact the identification of ticks. This study reports morphological anomalies in Haemaphysalis megaspinosa ticks for the first time.

Host-questing H. megaspinosa ticks were collected from the southern part of Hokkaido Prefecture, Japan, using a flannel sheet (70 × 100 cm) dragged over vegetation. Morphological observations were performed using a light microscope.

A total of 1,352 H. megaspinosa nymphs were collected, and morphological anomalies of the capitulum were observed in four individuals (0.3%). Among these, three individuals had a 3/3 dental formula, differing from those of normal individuals which have a 2/2 dental formula. The remaining specimen had a 3/2 dental formula and deformed palps.

Since the dental formula is a key morphological feature for identification of Haemaphysalis nymphs, this anomaly could potentially lead to misidentification. Hence, such anomalies, although potentially rare, are important to document considering accurate morphological identification. Further studies are needed to clarify the actual status of tick morphological anomalies in Japan.