Meeting Abstract
P2.104 Saturday, Jan. 5 A method to identify sex of post-infective third stage nematode larvae: a stepping stone to understanding parasite life history LOPEZ, S.R.*; BOYD, C.; KRISTAN, D.M.; California State University San Marcos; California State University San Marcos; California State University San Marcos lopez266@cougars.csusm.edu
Studies of parasite life history have revealed much about the complexities of host-parasite associations. However, for dioecious parasite species, sex specific survival is not well documented for every stage of the life cycle. Many Trichostrongyloidea nematodes have a free-living third larval stage (L3) prior to host infection and worms can remain in the L3 stage for 3-4d post-infection. Importantly, sex of L3 in Trichostrongyloidea nematodes has been shown to be chromosomally determined for all species studied to date and, therefore, does not change from free-living to post-infective stages. Although male and female L3 occur, it has been difficult to study sex specific life history characteristics of this stage in the life cycle because of a lack of sex-specific external morphology. As L3 develop into the fourth larval stage (L4), their gondal primordium (a group of cells that will become sex organs) will change size and position in the worm. We verified and expanded upon previous studies to develop a reliable method to determine sex of L3 from the nematode Heligmosomoides bakeri. We infected male laboratory mice (Mus musculus) with 200 L3 and then removed worms at 48h, 60h, 72h, and 84h post-infection and preserved worms in 10% phosphate buffered formalin. Using Nomarski optics and an ocular micrometer, the length of the gonadal primordium and its position in the worm were measured at each of these times post-infection and for free-living L3 that had been similarly preserved. We found that position of the gonadal primordium was a reliable indicator of sex at 72h post-infection. By knowing the sex ratio of L3 worms, we can now develop a better understanding of sex specific life history traits in every stage of the life cycle for this parasite.
