Trophic Eggs

Abstract

Organisms use a variety of mechanisms to protect and enhance the survival of their young. One mechanism is the use of specialized eggs, often referred to as ‘trophic eggs.’ While a variety of definitions have been proposed, in general terms trophic eggs are a type of extended maternal care that provides protection from predation and parasitism and in some groups serve as a nutritional supplement for both the offspring as well as the female parent. While previous authors have attempted to define trophic egg production in the context of the organisms or groups of organisms under study, trophic egg production is much broader than previously noted. While the use of trophic eggs has been observed in both invertebrates and vertebrates, the most evolved examples are more often observed in eusocial insects, especially the Formicidae where there are over 30 documented cases. However, examples of highly specialized mechanisms for the production of trophic eggs have been observed in two species of owlflies (Neuroptera: Ascalaphidae) where specialized ovarioles produce trophic eggs. The following is a literature review of the adaptation termed ‘trophic eggs’, how they are used and some of the factors that may have contributed to this adaptation.