In some spider species, offspring consume their mother. This behavior serves a purpose in the survival and development of the young. It is a form of parental care ensuring the next generation receives crucial nutrients.
The Phenomenon of Matriphagy
Matriphagy, from the Greek words for “mother” and “to eat,” is the biological process where offspring consume their mother. This behavior typically occurs within the first few weeks of the spiderlings’ lives. The specifics of how matriphagy unfolds can vary among species, but it generally involves the mother providing her body as a nutrient source.
In species like the desert spider (Stegodyphus lineatus), the mother’s internal organs begin to degrade and liquefy even before the eggs hatch. After the spiderlings emerge, the mother may initially regurgitate partially digested food for them. Within one to two weeks, the young then consume the mother’s liquefied tissues, often by puncturing her abdomen and sucking up the nutrient-rich fluid. This process can take several hours, leaving behind only an empty exoskeleton.
Other species employ different methods. For example, in the black lace-weaver (Amaurobius ferox), matriphagy begins after the mother lays trophic (nutritional) eggs for her offspring to consume. Days later, the mother uses web vibrations and drumming to signal to her spiderlings, inviting them to consume her. The spiderlings then inject venom to dissolve her tissues, leading to a quick death. In some crab spiders (Australomisidia ergandros), the mother’s nutrients are liquefied into hemolymph, which offspring consume through her leg joints, resulting in a more gradual process.
Evolutionary Advantages of Matriphagy
Matriphagy offers significant evolutionary advantages for the offspring. The consumption of the mother provides a highly concentrated and readily available source of nutrition, which is particularly beneficial in environments where food resources are scarce. This nutrient boost leads to several positive outcomes for the spiderlings.
Offspring that engage in matriphagy exhibit higher weights, faster molting times, and a larger body mass at dispersal. This accelerated development allows them to reach a more robust and active stage before venturing out independently, increasing their chances of survival. Matriphagy also improves the spiderlings’ ability to capture larger prey items and their survival rates compared to those deprived of this maternal meal. It can also reduce the likelihood of sibling cannibalism, as the mother’s body provides ample nourishment for the entire brood.
Diversity in Spider Parental Care
Matriphagy is not a universal behavior across all spider species; it is observed in a limited number of them. It is considered an extreme form of parental care, representing a terminal investment by the mother in her offspring’s success.
Many other spider species exhibit diverse forms of parental care without matriphagy. Some mothers construct protective egg sacs, guarding them vigilantly from predators and environmental fluctuations. Wolf spiders, for instance, are known for carrying their egg sacs attached to their spinnerets and, once hatched, carrying their spiderlings on their backs for several weeks. During this period, the mother protects her young.
Other spiders, like nursery web spiders, build specialized nursery webs where their young can develop safely. These varied strategies demonstrate the wide range of adaptations spiders have evolved to ensure the survival and reproductive success of their progeny.