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Simplified morphological criteria for ovarian classification in evaluating reproductive age groups of brown planthopper, Nilaparvata lugens (Stål)

Jiranan Piyaphongkul^a,*, Sukanya Arunmit^b, Wannaphan Janlapha^c, Wantana Srirattanasak^b

 
ABSTRACT:      Understanding the morphological changes in the female reproductive system is useful for predicting changes in population levels of the brown planthopper, Nilarparvata lugens. This study used morphological criteria to develop a simplified classification of ovarian development using only three phases based on age groups. In addition, the time required to complete each phase was investigated. Changes in the oviposition activity were examined in the female reproductive organs of virgin and mated macropterous N. lugens. Prior to dissecting N. lugens, side views of the females were captured, and the maximum abdominal width and contact angle (dragged from the center of annal tube to either side of body wall of the insect abdomen) were measured. Out of 1,032 samples, the ovaries of 300 virgin females did not develop to maturity, while 732 mated ones were categorized into three phases: I (pre-ovulation), II (ovulation and oviposition), and III (post-oviposition). The maximum time taken to develop during phase I was 5 days. Phase II period was prolonged for up to 15 days with an average of 6.9 days. The number of eggs laid per female varied from 3 to 208 with an average of 96?4.9 eggs. Females entered phase III within 5?17 days. The maximum abdominal width and contact angle of N. lugens were significantly different across three ovarian phases. These criteria provide a basis for identifying the ovarian phase and predicting the population dynamics of N. lugens as a key determinant in decision-making.

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* Corresponding author, E-mail: faasjnt@ku.ac.th

Received 13 May 2023, Accepted 15 Jun 2024