Sperm depletion in singly mated females of the Mexican Fruit Fly (Diptera: Tephritidae)

Authors: Thomas, Donald; LEAL, SANDRA - Animal And Plant Health Inspection Service (APHIS); CONWAY, HUGH - Animal And Plant Health Inspection Service (APHIS)

Submitted to: Journal of Entomological Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/12/2017
Publication Date: 1/1/2018
Citation: Thomas, D.B., Leal, S.N., Conway, H.B. 2018. Sperm depletion in singly mated females of the Mexican Fruit Fly (Diptera: Tephritidae). Journal of Entomological Science. 53(1):82-88.

Interpretive Summary: Mated status is assessed in captured wild fruitflies as a measurement of sterile release coverage and of the severity of pest outbreaks. Capture of a fertile female in a fly free zone triggers a quarantine, but a non-fertile female does not. The traditional method involves squashing sperm storage organs called spermathecae to see if sperm is present. The reliability of that method is questionable because it results in false negatives. The fertilization chamber, called the ventral receptacle, is the first organ to receive sperm during copulation. The function of the spermathecae is to store sperm and recharge the ventral receptacle when sperm there is depleted. The present study investigated the duration of fertility in females that have constant access to fruit where they lay their eggs. The spermathecae were depleted in 3-4 weeks. The ventral receptacle was depleted in 4-5 weeks. Thus including examination of the ventral receptacle along with the spermathecae is a more reliable method for determining mated status.

Technical Abstract: Female Mexican fruit flies, or mexflies, have the capacity to produce more than a thousand eggs over their lifetime but fertility of the eggs will depend on the female’s capacity to store semen and/or to replenish semen through remating. The two parameters are interrelated in that sexual receptivity depends to a large degree on insemination status. In this controlled study we measured sperm depletion in singly mated females with continuous access to oviposition substrates using a squash technique. The spermathecae were sequentially emptied of sperm over the three weeks following copulation. Under laboratory conditions, sperm was always found in the ventral receptacle up to four weeks following copulation, but was empty in almost all females by the 5th wk. These results mirrored previous measurements of fertility in singly mated female mexflies, which declines at 26-40 d post-copulation.