Submitted to: Physiological Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/14/2012
Publication Date: 10/1/2012
Citation: Yocum, G.D., Rinehart, J.P., Boetel, M.A. 2012. Water balance in the sugarbeet root maggot, Tetanops myopaeformis, during long-term low-temperature storage and after freezing. Physiological Entomology. 37(4):340-344. Interpretive Summary: There is an increasing need for high quality insects for use in biocontrol, research, pollination, and conservation programs. The scale of this need can be seen in the size and scope of rearing activities. The USDA-APHIS facility in El-Piño, Guatemala weekly produces 2.5 billion sterile male Mediterranean fruit flies. A critical research area to meet this need is the development of short and long storage protocols. The sugar beet root maggot Tetanops myopaeformis, is currently being investigated as a model insect for enhancing low-temperature storage. The larvae can be stored in moist sand at 4 - 6°C for up to five years. The objective of this investigation is to determine if T. myopaeformis water balance mechanism(s) degrade with increasing duration of storage. Three variables were examined during storage; percent body water, water loss rates, and water loss rates following a freezing event. The larvae ability to actively uptake water from the atmosphere during storage was also investigated. We believe three key factors are involved in the larvae ability to survive multi-years storage: 1) The larvae are either in prolonged diapause or post-diapause quiescence, naturally occurring developmental stages optimized for surviving prolonged low temperatures stress, 2) Overwintering larvae possess uncommonly large metabolic reserves, and 3) The high rates of water loss observed in this investigation indicate that the high moisture microenvironment is the third key component for larval survival during long-term storage. Understanding the relative contributions and interactions between each of these factors to T. myopaeformis larvae tolerance of prolonged storage will provide valuable insights into how to optimize storage protocols for other insect species.
Technical Abstract: The sugarbeet root maggot, Tetanops myopaeformis (Röder), can be stored in moist sand at 4 - 6°C for up to five years and is freeze tolerant. The majority of the stored larvae are in post-diapause quiescence and the rest of the larvae are in a multi-year diapause. The percent body mass of water and water loss rates were determined for diapausing and stored larvae. The percent body water range from 57 to 70.1 %. The diapausing larvae as well as those larvae stored for one year had significantly less percent body water than larvae stored for the two- and three-years. The water loss followed a first-order kinetic relationship between water loss and time. The two-year stored larvae lost water at a significantly higher rate than the diapausing larvae. Larvae exhibited no active water uptake at storage temperatures. A freezing event did not induce a significant decrease in percent body water once the larvae thawed nor did it increase the larval water loss rates. These results indicate that metabolic water and the microclimate during storage are key factors enabling long-term survival of T. myopaeformis larvae during low-temperature storage.