Abamectin-Driven Alterations on Queen Ovaries of the Leaf-Cutting Ant Acromyrmex subterraneus subterraneus (Hymenoptera: Formicidae)

摘要

A previous report on the likely reproductive impairment of queens of the leaf-cutting ant Acromyrmex subterraneus subterraneus Forel (Hymenoptera: Formicidae) caused by abamectin led to the present investigation. Morphological studies of the reproductive tract of queens of A. subterraneus subterraneus contact-exposed to 10.0 and 50.0 mg abamectin/ml exhibited a concentration-related reduction in the number of ovarioles per ovary. They ranged from 28.0 ± 1.2 in untreated queens to 25.0 ± 2.0 and 10.02 ± 0.5 ovarioles per ovary in queens exposed to 10.0 and 50.0 mg a.i./ml, respectively. The number of oocytes per ovariole also decreased with increasing abamectin concentrations with 65% reduction in queens exposed to 10.0 mg a.i./ml. Queens exposedto 50.0 mg a.i./ml did not show any viable oocytes in their ovarioles. Abamectin also caused substantial histological alterations in queens exposed to its highest concentration, including hypertrophy of the ovariole outer sheath (squamous epithelium) andnurse cell pycnosis. No pycnosis was observed on queens exposed to 10.0 mg a.i./ml, but they showed fragmented nuclei chromatin, which could evolve into pycnosis.