Michael P. Russell

Resource allocation plasticity in sea urchins: rapid, diet induced, phenotypic changes in the green sea urchin, Strongylocentrotus droebachiensis (Müller)

Abstract The gonads of sea urchins have a dual function: reproduction and nutrient storage. In general, these animals are secondarily sessile and cannot easily migrate from areas of low resource availability to areas of high resource availability. Given these conditions, an experiment was performed to test the hypothesis that sea urchins ( Strongylocentrotus droebachiensis Muller) from an area of low food quality could rapidly increase gonadal tissue in response to a sudden increase of high quality food. Sea urchins were collected from a site that lacked preferred algae on Swans Island, Maine. Initially, animals were dissected to determine the percentage of the various body components. The remaining animals were distributed among four groups of equal number and size distribution. Each group was assigned randomly to 1 of 4 feeding treatments: Alaria esculenta , Laminaria digitata , Laminaria longicruris , and Ascophyllum nodosum . Animals were fed ad libitum during the experiment. Half of the sea urchins from each treatment were dissected after 3 weeks and the rest after 6 weeks. Significant differences were found among the treatments at both the 3 and 6 weeks dissections with A . esculenta producing the greatest increase in gonad wet weight. For the 6 weeks dissections there appeared to be a compensatory loss of perivisceral fluid in sea urchins that increased gonadal tissue. No differences among treatments were found for the body wall, Aristotles lantern, or gut body components. Synthesizing these results with studies of other closely related species reveals a dynamic picture of resource allocation and phenotypic plasticity in sea urchins. Environmental variation can induce morphological change in sea urchins and these modifications have been described as graded reaction norms. The results presented here show that the temporal responses of the reaction norms of the various body components are graded and different components vary in response time.

Real and random patterns associated with molluscan spatial and temporal distributions

-The species-level properties of geographic range and geologic duration are often used as variables in evolutionary studies. However, estimates of species duration are not independent of estimates of geographic range. Before these properties are used in macroevolutionary hypotheses, error associated with these estimates must be quantified. This error may lead to spurious inferences of evolutionary processes. To assess the error associated with estimates of geographic range and geologic duration, we modeled various sampling regimes and calculated the bias associated with these estimates. We present three analyses which document the bias associated with estimates of geographic range and geologic duration. First, we find a positive correlation between local abundance and geographic range for a sample of 180 species of Recent prosobranch gastropods from the northeastern temperate Pacific Ocean. Therefore, geographically short-ranging species are less likely to be represented in the fossil record than geographically long-ranging species because of their local rarity. Second, we demonstrate that the chance of underestimating the geographic range of a species is acute for species with restricted spatial distributions, further compounding the problem of documenting their distribution in space and time. Third, we present a simulation which quantifies the degree of autocorrelation between geographic range and geologic duration for different levels of sampling resolution and spatial distributions of fossil localities. Michael P. Russell. Department of Paleontology, University of California, Berkeley, California 94720 David R. Lindberg. Museum of Paleontology, University of California, Berkeley, California 94720 Accepted: August 22, 1988

Type 2 diabetes is associated with loss of HDL endothelium protective functions

Aims/Hypothesis One of the hallmarks of diabetes is impaired endothelial function. Previous studies showed that HDL can exert protective effects on endothelium stimulating NO production and protecting from inflammation and suggested that HDL in obese people with diabetes and dyslipidemia may have lower endothelial protective function. We aimed to investigate whether type 2 diabetes impairs HDL endothelium protective functions in people with otherwise normal lipid profile. Methods In a case-control study (n = 41 per group) nested in the Cooper Center Longitudinal Study we tested the ability of HDL to protect endothelium by stimulating endothelial nitric oxide synthase activity and suppressing NFκB-mediated inflammatory response in endothelial cells. In parallel we measured HDL protein composition, sphinogosine-1-phosphate and P-selectin. Results Despite similar levels of plasma HDL-C the HDL in individuals with type 2 diabetes lost almost 40% of its ability to stimulate eNOS activity (P<0.001) and 20% of its ability to suppress TNFα-dependent NFκB-mediated inflammatory response in endothelial cells (P<0.001) compared to non-T2D controls despite similar BMI and lipid profile (HDL-C, LDL-C, TC, TG). Significantly, the ability of HDL to stimulate eNOS activity was negatively associated with plasma levels of P-selectin, an established marker of endothelial dysfunction (r = −0.32, P<0.001). Furthermore, sphingosine-1-phosphate (S1P) levels were decreased in diabetic plasma (P = 0.017) and correlated with HDL-mediated eNOS activation. Conclusions/Interpretations Collectively, our data suggest that HDL in individuals with type 2 diabetes loses its ability to maintain proper endothelial function independent of HDL-C, perhaps due to loss of S1P, and may contribute to development of diabetic complications.

Bioerosion by pit-forming, temperate-reef sea urchins: History, rates and broader implications

Sea urchins are dominant members of rocky temperate reefs around the world. They often occur in cavities within the rock, and fit so tightly, it is natural to assume they sculpted these “pits.” However, there are no experimental data demonstrating they bore pits. If they do, what are the rates and consequences of bioerosion to nearshore systems? We sampled purple sea urchins, Strongylocentrotus purpuratus, from sites with four rock types, three sedimentary (two sandstones and one mudstone) and one metamorphic (granite). A year-long experiment showed urchins excavated depressions on sedimentary rocks in just months. The rate of pit formation varied with rock type and ranged from <5 yr for medium-grain sandstone to >100 yr for granite. In the field, there were differences in pit size and shapes of the urchins (height:diameter ratio). The pits were shallow and urchins flatter at the granite site, and the pits were deeper and urchins taller at the sedimentary sites. Although overall pit sizes were larger on mudstone than on sandstone, urchin size accounted for this difference. A second, short-term experiment, showed the primary mechanism for bioerosion was ingestion of the substratum. This experiment eliminated potential confounding factors of the year-long experiment and yielded higher bioerosion rates. Given the high densities of urchins, large amounts of rock can be converted to sediment over short time periods. Urchins on sandstone can excavate as much as 11.4 kg m-2 yr-1. On a broader geographic scale, sediment production can exceed 100 t ha-1 yr-1, and across their range, their combined bioerosion is comparable to the sediment load of many rivers. The phase shift between urchin barrens and kelp bed habitats in the North Pacific is controlled by the trophic cascade of sea otters. By limiting urchin populations, these apex predators also may indirectly control a substantial component of coastal rates of bioerosion.