Thursday, December 12, 2013

Have you ever fought with a sibling in the backseat of a car? Ever argued over Legos, Barbies, or who gets the last Oreo? Well your sibling rivalry is nothing compared to those found in nature…

In many groups within the animal kingdom, sibling cannibalism has been observed (Fox 1975). This rather intense form of bickering among brothers and sisters comes in various forms, and can start at a very young age. So young in fact, that the siblings haven’t yet left their mother.

A Crepipatella occulta larva consuming a nurse egg
In utero cannibalism is called adelphophagy, in which one multi-celled embryo consumes another embryo or multiple nurse eggs. In the latter case, the organism is consuming its “potential sibling” (MacKay and Gibson 1999). This form of intrauterine cannibalism may provide certain fitness advantages to the embryos that survive; the nutrients gained allow them to develop larger and healthier, giving them a greater chance of survival after leaving the mother (Collin and Spangler 2012).

This behavior is found across various organisms, from lady bugs to certain sharks (Osawa 2002, Gilmore et al 1983). 
Intrauterine cannibalism has been observed in Sand Tiger Shark 
Of particular interest to me is the adelphophagic development of certain marine gastropods. My work in the Collin lab involves nurse egg development in three species of marine snails, from both Panama and Chile. The variability in these three species’ development shows just how diverse sibling cannibalism can be, even on a very small scale. So while it may seem to be a cruel form of development, it is also an extremely interesting and complex ecological behavior.

And with all that in mind, my brother comes to visit me in Panama tomorrow…

Collin, Rachel, and Abby Spangler. "Impacts of Adelphophagic Development on Variation in Offspring Size, Duration of Development, and Temperature-Mediated Plasticity." The Biological Bulletin 223.3 (2012): 268-77
Fox, L. R. "Cannibalism in Natural Populations." Annual Review of Ecology and Systematics 6.1 (1975): 87-106.
Gilmore, R. G., J. W. Dodrill, and P. A. Linley. "Reproduction and Embryonic Development of the Sand Tiger Shark, Odontaspis Taurus (Rafineque)." Fishery Bulletin 81.2 (1983): 201-25.
Mackay, Julie, and Glenys Gibson. "The Influence of Nurse Eggs on Variable Larval Development In(Polychaeta: Spionidae)." Invertebrate Reproduction & Development 35.3 (1999): 167-76.
Osawa, Naoya. "Sex-dependent Effects of Sibling Cannibalism on Life History Traits of the Ladybird Beetle Harmonia Axyridis (Coleoptera: Coccinellidae)." Biological Journal of the Linnean Society 76.3 (2002): 349-60.