Trophic Egg - Examples

Examples

• Trophic egg-laying is found relatively commonly in sub-social insects, one of the most commonly studied being the bug Adomerus triguttulus (Heteroptera: Cydnidae). Nymphs are provisioned with nettle seeds, and the ratio of trophic eggs to viable ones is higher when seeds are less well-developed or in lower quantities, indicating that they are filling the deficit of the alternate food source.
• Many ant species produce trophic eggs, although in the case of Pachycondyla apicalis (Formicidae: Ponerinae) the trophic eggs are laid by workers and offered to the queen rather than to developing offspring. However this depends on transmission of pheromones from the queen, since workers lacking contact with the queen may instead start to lay reproductive eggs.
• Some spider species lay a batch of trophic eggs the day after the viable offspring have emerged. This precise timing is based on close interactions between the mother and her offspring, including rotating and drumming behaviour by the mother, which stimulates the spiderlings to climb onto her body at the exact time of release of the trophic eggs. Consumption of trophic eggs can more than double the body weight of the spiderlings, greatly increasing their chances of survival.
• Some species of tree frogs produce trophic eggs in the same location as their reproductive eggs. Species such as Dendrobates spp. lay both types of eggs within water-filled tree holes, bromeliad reservoirs, and pitcher plants; where the trophic eggs provide nutrition for the emerging tadpoles. Another frog species, Leptodactylus fallax, shows extraordinarily high levels of parental care, with both parents remaining near the burrow, and females feeding each brood a total of 10,000-25,000 trophic eggs, their only source of nutrition.
• Intrauterine cannibalism is common in the viviparous shark order Lamniformes (commonly known as mackerel sharks). This strategy is effective in applying the mother's available resources to production of the optimal number of offspring viable in the ecological niche of a large marine predator. Such cannibalism may take the form of oophagy (eating sibling eggs) or adelphophagy (literally, eating one’s brother, but in context meaning the eating of one's siblings). In either form intrauterine cannibalism certainly minimises waste of nutrient resources, such as surplus eggs in the mother's reproductive system, and it prevents the development of excessive numbers of small offspring, rather than a small number of vigorously competitive young sharks. It has been speculated to ensure the survival of only the fittest offspring. However, that speculation has no substance, simply because there is no systematic genetic difference, and hence no systematic difference in genetic fitness, between embryos produced at various times and places in the mother's reproductive system. An embryo that in genetic terms is poorly fit, but nearly mature, would have no difficulty in eating an fit egg or much younger sibling embryo, no matter how genetically fit they might be.