title: Extended hypoxia in the alfalfa leafcutting bee, Megachile rotundata, increases survival but causes sub-lethal effects.
abstract: Many insects are tolerant of hypoxic conditions, but survival may come at a cost to long-term health. The alfalfa leaf-cutting bee, Megachile rotundata, develops in brood cells inside natural cavities, and may be exposed to hypoxic conditions for extended periods of time. Whether M. rotundata is tolerant of hypoxia, and whether exposure results in sub-lethal effects, has never been investigated. Overwintering M. rotundata prepupae were exposed to 10%, 13%, 17%, 21% and 24% O2 for 11 months. Once adults emerged, five indicators of quality - emergence weight, body size, feeding activity, flight performance, and adult longevity, - were measured to determine whether adult bees that survived past exposure to hypoxia were competent pollinators. M. rotundata prepupae are tolerant of hypoxic condition and have higher survival rates in hypoxia, than in normoxia. Under hypoxia, adult emergence rates did not decrease over the 11 months of the experiment. In contrast, bees reared in normoxia had decreased emergence rates by 8 months, and were dead by 11 months. M. rotundata prepupae exposed to extended hypoxic conditions had similar emergence weight, head width, and cross-thorax distance compared to bees reared in standard 21% oxygen. Despite no significant morphological differences, hypoxia-exposed bees had lower feeding rates and shorter adult lifespans. Hypoxia may play a role in post-diapause physiology of M. rotundata, with prepupae showing better survival under hypoxic conditions. Extended exposure to hypoxia, while not fatal, causes sub-lethal effects in feeding rates and longevity in the adults, indicating that hypoxia tolerance comes at a cost.
authors.affiliation: Department of Biological Sciences, NDSU Dept 2715, North Dakota State University, PO Box 6050, Fargo, ND 58108-6050, USA. Electronic address: houda.abdelrahman.1@ndsu.edu.
authors.forename: H
authors.initials: H
authors.lastname: Abdelrahman
authors.affiliation: U.S. Department of Agriculture, Agriculture Research Services, Red River Valley Agricultural Research Center, 1605 Albrecht Blvd. North, Fargo, ND 58102-2765, USA. Electronic address: joseph.rinehart@ars.usda.gov.
authors.forename: J P
authors.initials: JP
authors.lastname: Rinehart
authors.affiliation: U.S. Department of Agriculture, Agriculture Research Services, Red River Valley Agricultural Research Center, 1605 Albrecht Blvd. North, Fargo, ND 58102-2765, USA. Electronic address: george.yocum@ars.usda.gov.
authors.forename: G D
authors.initials: GD
authors.lastname: Yocum
authors.affiliation: Department of Biological Sciences, NDSU Dept 2715, North Dakota State University, PO Box 6050, Fargo, ND 58108-6050, USA. Electronic address: kendra.greenlee@ndsu.edu.
authors.forename: K J
authors.initials: KJ
authors.lastname: Greenlee
authors.affiliation: Department of Biological Sciences, NDSU Dept 2715, North Dakota State University, PO Box 6050, Fargo, ND 58108-6050, USA; U.S. Department of Agriculture, Agriculture Research Services, Red River Valley Agricultural Research Center, 1605 Albrecht Blvd. North, Fargo, ND 58102-2765, USA. Electronic address: bryan.r.helm@ndsu.edu.
authors.forename: B R
authors.initials: BR
authors.lastname: Helm
authors.affiliation: U.S. Department of Agriculture, Agriculture Research Services, Red River Valley Agricultural Research Center, 1605 Albrecht Blvd. North, Fargo, ND 58102-2765, USA. Electronic address: william.kemp@ars.usda.gov.
authors.forename: W P
authors.initials: WP
authors.lastname: Kemp
authors.affiliation: Department of Biological Sciences, NDSU Dept 2715, North Dakota State University, PO Box 6050, Fargo, ND 58108-6050, USA. Electronic address: cody.schulz.1@ndsu.edu.
authors.forename: C H
authors.initials: CH
authors.lastname: Schulz
authors.affiliation: Department of Biological Sciences, NDSU Dept 2715, North Dakota State University, PO Box 6050, Fargo, ND 58108-6050, USA. Electronic address: Julia.bowsher@ndsu.edu.
authors.forename: J H
authors.initials: JH
authors.lastname: Bowsher
mesh_terms: D000818:Animals; D001516:Bees / Q000254:growth & development* / Q000502:physiology*; D049628:Body Size; D064666:Diapause, Insect; D005247:Feeding Behavior; D005426:Flight, Animal; D000860:Hypoxia / Q000473:pathology; D007814:Larva; D008136:Longevity; D010100:Oxygen; D012621:Seasons
chemical_list: D010100:Oxygen
keywords: Diapause; Feeding rate; Fight metabolic rate; Hypoxia; Megachile rotundata; Overwintering