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Specificity in the Gregarine assemblage parasitizing Tenebrio molitor
Abstract
Gregarina niphandrodes Clopton, Percival and Janovy, 1991, Gregarina cuneata Stein, 1848, Gregarina polymorpha (Hammerschmidt, 1838) Stein, 1848, and Gregarina steini Berndt, 1902, constitute the gregarine assemblage parasitizing the yellow mealworm, Tenebrio molitor. Comparative life cycle studies were conducted across several ontogenetic stages to provide an illustration of the nature of host specificity in the gregarine life cycle. Reciprocal cross-stadium experimental infections demonstrated that G. cuneata, G. polymorpha, and G. steini are restricted to larval T. molitor and G. niphandrodes are restricted to adult T. molitor. The exogenous developmental niches of G. niphandrodes, G. cuneata, and G. polymorpha were determined along temperature and humidity axes and associated with parasite niche space on the host resource axis. Gregarine gametocysts were incubated at controlled humidity (0, 10, and 20 mm Hg vapor pressure deficit) at 20, 25, 30, and 35 C to determine the environmental limits to survival and sporulation. Although the environmental conditions that permit gametocyst developmental overlap, G. niphandrodes utilize a subset of sporulation and survival conditions that are incompatible with the developmental needs of G. cuneata and G. polymorpha. Likewise, G. cuneata and G. polymorpha survive and sporulate under a subset of environmental conditions that are incompatible with the developmental needs of G. niphandrodes. The pattern of interspecific variation in the environmental tolerances of gregarine gametocysts is analogous to the pattern of interspecific variation in host stadium specificity observed in endogenous gregarine stages. The oocysts of G. niphandrodes, G. cuneata, and G. polymorpha were tested for variation in viability over time, variation in post-sporulation development, and for host stadium specific physiological cues that initiate exsporulation. There are no interspecific differences in oocyst viability over time, post-sporulation developmental timing in the oocyst, nor in the physiological cues that initiate oocyst exsporulation in the host gut. There is no evidence to suggest that any of these phenomena play a role in host stadium specificity. These results are interpreted within the context of Chabaud's host capture hypothesis.
Subject Area
Zoology|Ecology|Entomology
Recommended Citation
Clopton, Richard Ellis, "Specificity in the Gregarine assemblage parasitizing Tenebrio molitor" (1993). ETD collection for University of Nebraska-Lincoln. AAI9333959.
https://digitalcommons.unl.edu/dissertations/AAI9333959