Re-examination of the Effects of Food Abundance on Jaw Plasticity in Purple Sea Urchins

Morphological plasticity is a critical mechanism that animals use to cope with variations in resource availability. During periods of food scarcity, sea urchins demonstrate an increase in jaw length relative to test diameter. This trait is thought to be reversible and adaptive by yielding an increase in feeding efficiency. We directly test the hypotheses that (1) there are reversible shifts in jaw length to test diameter ratios with food abundance in individual urchins, and (2) these shifts alter feeding efficiency. Purple sea urchins, Strongylocentrotus purpuratus, were collected and placed in either high or low food treatments for 3 months, after which treatments were switched for two additional months between February and September, 2015 in La Jolla, CA (32.8674°N, 117.2530°W). Measurements of jaw length to test diameter ratios were significantly higher in low compared to high food urchins, but this was due to test growth in the high food treatments. Ratios of low food urchins did not change following a switch to high food conditions, indicating that this trait is not reversible within the time frame of this study. Relatively longer jaws were also not correlated with increased feeding efficiency. We argue that jaw length plasticity is not adaptive and is simply a consequence of exposure to high food availability, as both jaw and test growth halt when food is scarce

The Influence of pH Variation on CooA Activity

CooA, a CO-sensing heme protein, acts as a transcriptional activator of CO-metabolizing proteins in bacteria such as Rhodospirillum rubrum and Carboxydothermus hydrogenoformans through sequence-specific DNA binding. Previous research indicated a reduced iron center and CO gas were necessary for CooA to achieve its active conformation and bind DNA. To determine if other reaction conditions facilitate CooA activation, the role of pH on CooA function was tested. Specifically, a fluorescence anisotropy assay was employed to measure possible Fe(III) CooA DNA binding from pH 3 - 12. Interestingly, CooA was observed to bind DNA without CO at acidic conditions, with optimal binding observed at pH ~3. These results are discussed in light of the normal CO-dependent activation mechanism of CooA proteins

Classification of journal surfaces using surface topography parameters and software methods to compensate for stylus geometry

Measurements made with a stylus surface tracer which provides a digitized representation of a surface profile are discussed. Parameters are defined to characterize the height (e.g., RMS roughness, skewness, and kurtosis) and length (e.g., autocorrelation) of the surface topography. These are applied to the characterization of crank shaft journals which were manufactured by different grinding and lopping procedures known to give significant differences in crank shaft bearing life. It was found that three parameters (RMS roughness, skewness, and kurtosis) are necessary to adequately distinguish the character of these surfaces. Every surface specimen has a set of values for these three parameters. They can be regarded as a set coordinate in a space constituted by three characteristics axes. The various journal surfaces can be classified along with the determination of a proper wavelength cutoff (0.25 mm) by using a method of separated subspace. The finite radius of the stylus used for profile tracing gives an inherent measurement error as it passes over the fine structure of the surface. A mathematical model is derived to compensate for this error

Spatial and temporal variability in the relative contribution of king mackerel (Scomberomorus cavalla) stocks to winter mixed fisheries off South Florida

King mackerel (Scomberomorus cavalla) are ecologically and economically important scombrids that inhabit U.S. waters of the Gulf of Mexico (GOM) and Atlantic Ocean (Atlantic). Separate migratory groups, or stocks, migrate from eastern GOM and southeastern U.S. Atlantic to south Florida waters where the stocks mix during winter. Currently, all winter landings from a management-defined south Florida mixing zone are attributed to the GOM stock. In this study, the stock composition of winter landings across three south Florida sampling zones was estimated by using stock-specific otolith morphological variables and Fourier harmonics. The mean accuracies of the jackknifed classifications from stepwise linear discriminant function analysis of otolith shape variables ranged from 66−76% for sex-specific models. Estimates of the contribution of the Atlantic stock to winter landings, derived from maximum likelihood stock mixing models, indicated the contribution was highest off southeastern Florida (as high as 82.8% for females in winter 2001−02) and lowest off southwestern Florida (as low as 14.5% for females in winter 2002−03). Overall, results provided evidence that the Atlantic stock contributes a certain, and perhaps a significant (i.e., ≥50%), percentage of landings taken in the management-defined winter mixing zone off south Florida, and the practice of assigning all winter mixing zone landings to the GOM stock shoul

First-Year Recruitment of Largemouth Bass: The Interdependency of Early Life Stages

Four early life events (i.e., hatching, the ontogenetic diet shift to piscivory, fall lipid accumulation, and the first winter) are conceptualized as being critical to 1st-yr recruitment success of largemouth bass (Micropterus salmoides) via cause-and-effect associations among them. Toward this end, we conducted a multiple life-stage investigation of largemouth bass to examine the functional dependency and significance to recruitment of these temporally separated early life events. Specifically, we quantified growth and survival of two largemouth bass year-classes in six Alabama ponds from hatching to the end of the first winter. The first winter was an important survival bottleneck with lower largemouth bass survival in ponds with smaller largemouth bass (high-density ponds), relative to ponds with larger fish (low-density ponds). While cannibalism was not important, we found sizedependent first-winter mortality to be regulated directly by lipid reserves (i.e., triglycerides) accumulated during fall, and indirectly by both hatch date and the ontogenetic diet shift to piscivory during summer. Early-hatched largemouth bass attained an initial length advantage, remaining large relative to late-hatched fish, despite the relatively higher growth rate of late-hatched fish during their first month of life. Enhanced size permitted earlyhatched fish to become piscivorous before late-hatched fish, increasing their access to fish prey (i.e., sunfishes) during fall. This in turn elevated their fall lipid accumulation and winter survival above that of late-hatched fish. Our results indeed suggest that 1st-yr recruitment of largemouth bass in southern systems is governed by several functionally dependent critical events. Because each is likely vital to understanding recruitment variability, we suggest that future recruitment studies should adopt a more synthetic (i.e., multiple life-stage) approach.This research was supported in part by National Science Foundation grants DEB-9108986 and DEB-9410323, and Federal Aid in Fish Restoration Project F40-R administered by the Alabama Game and Fish Division to DRD

Asymmetric Synthesis of New Chiral Europium N,N'-Disuccinate Complexes:Shift Reagents for Aqueous Solutions and Application in the Enantiomeric Excess Determination of Amino Acids

The synthesis of new chiral N,N'-disuccinate ligands (R,R)-8, (R,R)-9, and (S,S)-10 from (5R)- or (SS)-(menthyloxy)-2(5H)-furanone is described. These ligands, after complexation with EuCl3.6H(2)O, are highly suitable as chiral shift reagents for the enantiomeric excess determination of amino acids and alpha-alkylated amino acids in aqueous solutions. Resolution experiments using various amino acids and their derivatives and a study of the pH dependency of the induced diastereomeric shift differences are included

Prey Selection by Larval Fishes as Influenced by Available Zooplankton and Gape Limitation

Feeding success during the first weeks of life is critical to determining survival and ultimate year-class strength of fishes. To compare the relative influence of gape limitation and available zooplankton on prey size selection among the larvae of three species of freshwater fishes, we gathered data on fish gape size, prey size, and size-specific prey selection in lakes and reservoirs. These variables were compared among black crappies Pomoxis nigromaculatus from a lake that contained large zooplankton as prey and white crappies P. annularis and gizzard shad Dorosoma cepedianum (a potential competitor of white crappie) from reservoirs that contained small zooplankton. In three Ohio reservoirs (i.e., small-zooplankton systems), available zooplankton and larval stages of white crappies and gizzard shad were collected once per week during April through September 1987 and 1988. Although mean prey size of white crappies continued to increase with fish size, mean prey size of smaller-gaped gizzard shad did not. However, as documented for black crappies in north-temperate lakes, white crappies in reservoirs continued to consume prey that were smaller than other available prey, even when they were no longer gape limited. Thus, although the potential for gape limitation differed between large- and small-zooplankton assemblages, prey selection did not differ as expected. Given between-species prey size selection, gizzard shad (that prefer small zooplankton) should be relatively more successful in reservoirs with small zooplankton, whereas white and black crappies (that prefer large zooplankton) should have better success in lakes with large zooplankton.This work was supported in part by DEB- 9108986 and DEB-9410323 to D.R.D., and by NSF BSR-8705518, DEB-9107173, DEB-9407859, and Federal Aid in Fish Restoration, project F-57-R to R.A.S., administered through the Ohio Division of Wildlife