Allantoin crystal formation in Bagrada hilaris (Burmeister)(Hemiptera: Pentatomidae) females

Authors: Rojas, Maria - Guadalupe; Grodowitz, Michael; REIBENSPIES, JOSEPH - Texas A&M University; REED, DARCY - University Of California; PERRING, THOMAS - University Of California; Abbas, Hamed

Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/12/2017
Publication Date: N/A
Publication URL: http://handle.nal.usda.gov/10113/5700680
Citation: N/A

Interpretive Summary: The bagrada bug, Bagrada hilaris, is a polyphagous herbivore recently reported as an invasive pest in the U.S. During dissections crystals were observed in females midgut and oviducts. Crystals were identified using x-ray diffraction techniques. Both acicular (i.e., needle-like, slender and/or tapered) and cubic (i.e., cube shaped) crystals were observed in six of 75 individuals examined (8.0%). The crystals were mainly observed in females (6.7%), followed by males (1.3%) with no crystals observed in the minimal number of nymphs examined (0%). Crystals of both types were detected in the midgut and lateral oviducts of the females and midgut in males. The acicular crystals often appeared as distinct bundles when present in the midgut and oviducts. The cubic crystals were identified as allantoin, while the acicular crystals were most likely DL-allantoin in combination with halite. While allantoin in a soluble form is often found in insect tissues and excreta; being present as a crystal, especially in such a large form, is curious and raises some interesting questions. More research is warranted to further understand mechanisms associated with such crystal formation in B. hilaris and can lead to a better understanding of the excretory process in this species and the role allantoin plays in the elimination of excess nitrogen.

Technical Abstract: Bagrada hilaris is a polyphagous herbivore recently reported as an invasive pest in the U.S. During the course of dissecting B. hilaris to understand ovarian morphology in relation to egg production and to determine sperm viability, unique crystals were observed in both the midgut and oviducts. Crystals were identified using x-ray diffraction techniques. Both acicular (i.e., needle-like, slender and/or tapered) and cubic (i.e., cube shaped) crystals were observed in six of 75 individuals examined (8.0%). The crystals were mainly observed in females (6.7%), followed by males (1.3%) with no crystals observed in the minimal number of nymphs examined (0%). Crystals of both types were detected in the midgut and lateral oviducts of the females and midgut in males. The acicular crystals often appeared as distinct bundles when present in the midgut and oviducts. Crystals varied in size with the acicular crystals ranging from 0.12 mm to 0.5 mm in length while the cubic crystals ranged in length from 0.25 mm to over 1.0 mm with widths of approximately 0.25 mm. The cubic crystals were identified as allantoin while the acicular crystals were most likely DL-allantoin in combination with halite. While allantoin in a soluble form is often found in insect tissues and excreta; being present as a crystal, especially in such a large form, is curious and raises some interesting questions. More research is warranted to further understand mechanisms associated with such crystal formation in B. hilaris and can lead to a better understanding of the excretory process in this species and the role allantoin plays in the elimination of excess nitrogen.