Offspring Size in Marine Animals

Abstract

Marine animals can allocate their investment in reproduction into many small offspring, a few large ones, or anything in between. The trade-off between the two extreme strategies is that the chance to survive to maturation varies inversely with offspring size. We examined size in marine organisms across a wide taxonomic range covering >17 orders of magnitude in body mass and found two distinct strategies: offspring is either proportional to, or invariant with, parent size. Which strategy is optimal depends mainly on how mortality rate of juveniles varies with body size, and hence, determines the chance of surviving to maturation. The photo collage illustrates some of the diversity of marine animals covered in our study. The organisms are not to scale. The species included are (from upper left): cuckooGillSansMT-Italic wrasse (Labrus mixtus), sea angel (Clione limacina), larva of Norwegian lobster (Nephrops norvegicus), box jelly (Euplokamis dunlopae), and (second row from left): the copepod (Metridia longa), larva of the seastar (Luidia sarsi), larva of the lion mane (Cyanea capillata), pluteus larva of brittle star, and larval cod (Gadus morhua). Photo collage by E. Selander. The photograph illustrates the article “Adult and offspring size in the ocean over 17 orders of magnitude follows two life history strategies,” by Anna B. Neuheimer, Martin Hartvig, Jan Heuschele, Samuel Hylander, Thomas Kiørboe, Karin H. Olsson, Julie Sainmont, and Ken H. Andersen, tentatively scheduled to appear in Ecology 96(12), December 2015. http://dx.doi.org/10.1890/14-2491.1