The subtle intracapsular survival of the fittest: maternal investment, sibling conflict, or environmental effects?
Ecological Society of America
Developmental resource partitioning and the consequent offspring size variations are of fundamental importance for marine invertebrates, in both an ecological and evolutionary context. Typically, differences are attributed to maternal investment and the environmental factors determining this; additional variables, such as environmental factors affecting development, are rarely discussed. During intracapsular development, for example, sibling conflict has the potential to affect resource partitioning. Here, we investigate encapsulated development in the marine gastropod Buccinum undatum. We examine the effects of maternal investment and temperature on intracapsular resource partitioning in this species. Reproductive output was positively influenced by maternal investment, but additionally, temperature and sibling conflict significantly affected offspring size, number, and quality during development. Increased temperature led to reduced offspring number, and a combination of high sibling competition and asynchronous early development resulted in a common occurrence of “empty” embryos, which received no nutrition at all. The proportion of empty embryos increased with both temperature and capsule size. Additionally, a novel example of a risk in sibling conflict was observed; embryos cannibalized by others during early development ingested nurse eggs from inside the consumer, killing it in a “Trojan horse” scenario. Our results highlight the complexity surrounding offspring fitness. Encapsulation should be considered as significant in determining maternal output. Considering predicted increases in ocean temperatures, this may impact offspring quality and consequently species distribution and abundance.
Thanks are given to Viviers, UK, and Vör Marine Research Center, Iceland, for their help with adult sample collection. Thanks also go to Adam Reed, Alastair Brown, and Andrew Oliphant for help with animal maintenance, and to Andrew Oliphant for helpful discussions on the topic. This work was supported by grants from the Total Foundation (Abyss2100) to S. Thatje and the Malacological Society to K. Smith. We thank two anonymous reviewers for constructive criticism on the draft manuscript.
This is the final version of the article. Available from Ecological Society of America via the DOI in this record.
Vol. 94 (10), pp. 2263 - 2274