Meeting Abstract

49.11  Jan. 6  Egg mass physiology: Interactive effects of morphology, temperature, and embryonic age on oxygen gradients in invertebrate egg masses WOODS, H.A.**; MORAN, A.L.; Univ. of Montana, Missoula; Clemson University, Clemson, SC art.woods@mso.umt.edu

Embryos of many marine invertebrates are encased in gelatinous masses for part or all of development. Because gel retards oxygen flux, this life-history mode profoundly affects partial pressures of metabolic gases surrounding embryos. We examined the effects of four factors (temperature, embryo age, embryo density, and egg-mass size) on the metabolism of egg masses using both natural egg masses of a nudibranch and artificial egg masses made using sand dollar embryos and agarose. Both temperature and embryo age strongly affected metabolic rates of nudibranch embryos. Rates of oxygen consumption roughly doubled between 12 and 21 degrees C and increased 2-4 fold from early cleavage to the veliger stage. Advanced embryonic age and higher temperature both led to steeper oxygen gradients into egg masses. Small artificial masses (2 mm diameter) had virtually no internal oxygen gradients regardless of embryo density or temperature, while oxygen profiles in medium (4 mm) and large (10 mm) artificial masses depended strongly and interactively on embryo density and temperature. Our data suggest that temperature, through its effects on embryonic metabolism, interacts with embryo age, embryo density, and egg-mass size in important ways bearing on egg mass design. These findings allowed us to make specific predictions about egg mass physiology within and among species distributed across steep marine temperature gradients in nature. We test these predictions by comparing temperature sensitivity of metabolism of nudibranch embryos from temperate versus Antarctic sites.