Scholarship Copyright (c) 2013 Illinois Wesleyan University All rights reserved. http://digitalcommons.iwu.edu/bio_scholarship Recent documents in Scholarship en-us Fri, 25 Jan 2013 22:19:22 PST 3600 Variation in alanine transport among sibling lecithotrophic larvae of holothuroid and asteroid echinoderms http://digitalcommons.iwu.edu/bio_scholarship/33 http://digitalcommons.iwu.edu/bio_scholarship/33 Thu, 30 Sep 2010 10:48:52 PDT Variation in development rate (e.g., time to metamorphic competence) among sibling larvae has been reported, but inter-individual differences in physiological processes has received comparatively little attention.

]]> William Jaeckle Transport and Metabolism of Alanine and Palmitic Acid by Field-Collected Larvae of <i>Tedania ignis</i> (Porifera, Demospongiae): Estimated Consequences of Limited Label Translocation http://digitalcommons.iwu.edu/bio_scholarship/32 http://digitalcommons.iwu.edu/bio_scholarship/32 Thu, 30 Sep 2010 10:48:51 PDT The epidermis of larvae of Tedania ignis(Porifera, Demospongiae) is uniformly ciliated except for the posterior pole. The epidermal cells are long, columnar, and monociliate; each cilium arises from an epidermal crypt; symbiotic bacteria were not observed in larval cells. These lecithotrophic ("nonfeeding") larvae can feed by assimilating dissolved organic materials (DOM) from seawater. Larvae transported both the amino acid alanine (mean = 2.73 pmol larva-1 h-1; [S] = 1 µM) and the fatty acid palmitic acid (mean = 16.27 pmol larva-1 h-1; [S] = 1 µM) from seawater. Following assimilation, the label from alanine was recovered primarily in small molecular weight compounds; the label from palmitic acid was localized chiefly in the lipid fraction. Estimates of the contribution of transport to metabolism (mean respiration rate = 940.7 pmol O2 larva-1 h-1) reveal that alanine transport is energetically insignificant. Palmitic acid transport, in contrast, could account for 21%-55% of larval metabolism. Autoradiographic analysis of the distribution of the label in larvae suggests that epidermal cells are the chief recipients of the assimilated materials. Thus, the contribution of transport to whole-larva metabolism may underestimate the tissue-specific value. At palmitic acid concentrations of 1 and 0.25 µM, the contribution of transport to the estimated metabolism of the epidermis would be 131% and 33% of energy requirements. Thus, the potential benefits of DOM to larvae are dependent not only on the nature of the epidermal transporters and the solute concentration, but also the degree to which materials are distributed among tissues.

Originally published in Biological Bulletin and used with permission.

]]> William B. Jaeckle Biology Rates of Energy Consumption and Acquisition by lecithotrophic larvae of <i>Bugula neritina</i> (Bryozoa: Cheilostomata) http://digitalcommons.iwu.edu/bio_scholarship/31 http://digitalcommons.iwu.edu/bio_scholarship/31 Thu, 30 Sep 2010 10:48:49 PDT Lecithotrophic larvae of the cheilostome bryozoan, Bugula neritina (L.), lose metamorphic competence 12 to 24 h after release from the maternal zooid. The high respiration rate of newly released larvae (mean=306.3 pmol O2 larva-1 h-1, range= 149.3 to 466.6, n=18 trials, 22.5 °C) from adults collected at Link Port, Fort Pierce, Florida during the winter/spring of 1990-1991 reflects their active swimming behavior. The average energy con¬tent per larva was 15.24 mJ (range: 13.35 to 20.17 mJ ind-1, n=5 groups). If all cells have an identical energy content and metabolic rate, then 2 and 20% of the total en¬ergy content would be consumed by the onset (2 h post-re¬lease) and the loss (24 h post-release) of metamorphic competence. Larvae of B. neritina are a composite of both larval and juvenile tissues and the loss of metamorphic competence may be due to regional depletion of labile en¬ergy stores in transitory “larval" cells, particularly the ciliated cells that comprise the locomotory organ, the corona. Although "nonfeeding", B. neritina larvae can acquire nu¬trients from the environment in the form of dissolved or¬ganic materials (DOM) in seawater. Both the amino acid alanine and the fatty acid palmitic acid can be transported from seawater ([S]=1 µM, 22.5°C). The rates of alanine influx (aptpearance of label in tissue) averaged 0.366 pmol larva-1 h-1 and, based on comparisons between rates of so¬lute transportand metabolism, would contribute little (<1% of required energy) to offset the metabolic demand. The average rate of palmitic acid influx was 4.668 pmol larva-1 h-1 and, assuming that the measured influx equals the net solute flux, could account for 21 to 72% of energy requirements. These data suggest that the duration of planktonic life of B. neritina larvae is principally regulated by the amount of endogenous energy stores, but may be mod¬ulated by available DOM in seawater.

Originally published in Marine Biology and used with permission.

]]> William Jaeckle Biology Multiple Modes of Asexual Reproduction by Tropical and Subtropical Sea Star Larvae: an Unusual Adaptation for Genet Dispersal and Survival http://digitalcommons.iwu.edu/bio_scholarship/30 http://digitalcommons.iwu.edu/bio_scholarship/30 Thu, 30 Sep 2010 10:48:48 PDT Sea star larvae (Echinodermata: Asteroidea), collected from the subtropical Northwest Atlantic Ocean, exhibited three distinct modes of asexual reproduction. A number of different bipinnariae and brachiolariae reproduced by paratomous cloning of the posterolateral arms. This morphogenesis was identical to that of larvae assignable to the genus Luidia. A second mode of asexual reproduction involves the autotomization of an anterior portion of the preoral lobe. Primary larvae with preoral lobes of varying sizes and free-swimming preoral lobes of various stages of morphological development were simultaneously collected. The free-swimming preoral lobes developed complete digestive systems and ultimately assumed the form of typical bipinnaria larvae. Asexual reproduction by larvae may also take the form of budding. The released individual is either a blastula- or gastrulastage embryo. Subsequent development to a bipinnariastage secondary larva, with the possible exception of coelom formation, appears to occur through the events associated with normal larval development. These diverse methods of asexual propagation provide a common mechanism to increase the length of larval life and amplify the number of individuals. Thus asexual reproduction by larvae should increase the likelihood of genet representation in the next generation.

Originally published in Biological Bulletin and used with permission.

]]> William Jaeckle Biology Sea star larvae Experimental Manipulations of the Organic Chemistry of Seawater: Implications for Studies of Energy Budgets in Marine Invertebrate Larvae http://digitalcommons.iwu.edu/bio_scholarship/29 http://digitalcommons.iwu.edu/bio_scholarship/29 Thu, 30 Sep 2010 10:48:47 PDT Correct measurement of changes in biomass and metabolic rates over time are two essential elements for the accurate construction of energy budgets for invertebrate larvae. Both components of larval energetics are altered by changes in the organic chemistry of the seawater. Axenic (bacteria-free) veliger larvae (88 µm shell length) of the bivalve Crassostrea gigas (Thunberg, 1795) had a 53% enhancement of their metabolic rate relative to control values (5.8 ± 0.6 pmol larva -1 h -1 , x¯ ± 1 SE) when exposed to seawater to which 1 µM glucose had been added. Gastrulae increased their rate of respiration by 35%, from 10 ± 0.9 to 13.5 ± 1.4 pmol O2 embryo -1 h -1 ; prism-stage larvae by 33% from 40.9 ± 2.0 to 54.4 ± 2.8; and pluteus-stage larvae by 50%, from 33.4 ± 1.5 to 50.3 ± 3.1. Lecithotrophic larvae of the gastropod Haliotis refuscens Swainson, 1822, either had no change (Day 1, trochophore larvae) or a significant increase (Day 2, veliger larvae) in dry organic weight when reared in natural seawater that had been passed through a filter of 0.2- µm pore size (to remove particles). In contrast, sibling larvae always decreased in dry organic weight when reared in seawater which had first been passed through a sand-filter (a treatment that alters the organic chemistry of seawater), and then a 0.2- µm (pore size) filter. These data show that alterations of the organic chemistry of seawater can affect the growth and metabolism of invertebrate larvae. If such modifications are not controlled, energy budgets constructed from laboratory experiments on larvae in altered seawater may bear little resemblance to the energetics of larvae in the field.

]]> William Jaeckle Distribution of Bipinnaria and Pilidium in Relation to Physical Structure and UV-B Light in the Water Column off Anvers Island, Antarctica http://digitalcommons.iwu.edu/bio_scholarship/28 http://digitalcommons.iwu.edu/bio_scholarship/28 Thu, 30 Sep 2010 10:48:46 PDT Feeding larvae of Antarctic bottom invertebrates have proven to be scarce in the plankton and consequently our knowledge of their ecology is limited. We collected bipinnaria larvae assignable to the genus Odontaster and several types of pilidium larvae of nemertean worms in quantitative net tows taken during the austral spring and summer 1997-1998 and considered their distribution with respect to the density stratification of the water column and the potential exposure to UV-B (λ = 308 nm). The average number of pilidium and bipinnaria larvae in the upper 40 m of the water column was 0.5 ± 1.0 per m3 and the highest abundance was 2.1 per m3 in early January when 270 bipinnariae were collected at a depth of 28 m. In October and November, water density (σ1) in the upper 40 m was relatively uniform and bipinnariae and pilidiums were collected from 2 m to the maximum depth sampled (20-38 m). Beginning in December and continuing into February, surface melt produced a marked stratification of the upper water column with a major discontinuity layer at 10-15 m, and larvae were relatively rare near the surface. Larvae drifting at a depth of 4 m during periods of ozone depletion in October and November 1997 would potentially experience average maximum UV-B exposures of 80.10 joules/m2/hr. Later in spring and summer, under a normal ozone column, average maximum potential exposures were 2.26 joules/m2/hr at 14 m, where larvae were abundant. The physiological and ecological consequences of high surface exposures to UV-B during periods of ozone depletion depend on several factors, including stage development and residence times of larvae near the surface, and remain largely unknown.

]]> William Jaeckle Coelomogenesis and Nutrition of Clonally Produced Asteroid Larvae http://digitalcommons.iwu.edu/bio_scholarship/27 http://digitalcommons.iwu.edu/bio_scholarship/27 Thu, 30 Sep 2010 10:48:44 PDT Asexual reproduction by planktotrophic larvae of asteroids is an unusual life history strategy exhibited by several species in the families Luididae, Oreasteridae, Ophidiasteridae, and Asteriidae. Larvae of the former three families reproduce asexually in the field, while the asteriid Pisaster ochraceus has produced clones when larvae are reared in the laboratory. Our knowledge of the processes involved in larval cloning and the biology of the developing clone is fragmentary in nature. We used light, electron, and scanning laser confocal microscopy to study clones that develop through paratomy of the posterolateral larval arms. The archenteron forms by a modified form of gastrulation that is mediated by large numbers of mesenchyme cells as reported by Bosch et al. (1989). Coelomogenesis is by enterocoelly through outpockets of the clonal archenteron. The results of experiments designed to trace the movement of the protein ferritin in larval tissue revealed that clonal embryos may be nutritionally dependent on the primary larva. Organic materials assimilated by the primary larva are translocated through the blastocoelic compartment and accumulate differentially in actively clonal arms suggesting a stronger skin for blastocoelic nutrients compared to nonclonal arms. At the early bipinnaria stage clones are capable of feeding through the capture of particles and assimilation of dissolved proteins from water. By the time they separate from the primary larva the clones are morphologically indistinct from sexually produced bipinnariae of equivalent size.

]]> William Jaeckle Size and Organic Content of Eggs of Marine Annelids, and the Underestimation of Egg Energy Content by Dichromate Oxidation http://digitalcommons.iwu.edu/bio_scholarship/26 http://digitalcommons.iwu.edu/bio_scholarship/26 Thu, 30 Sep 2010 10:48:43 PDT Dichromate oxidation is a simple technique that is often used to estimate the energy content of eggs in studies of marine invertebrate life histories (1). We used this method to measure the energy contents of the eggs of 12 species of marine annelids. In combination with measures of egg ash-free dry weight (AFDW), these data yielded estimates of AFDW-specific energy density that were mostly lower than the average weight-specific energy density of carbohydrates. This seemed unlikely to be correct, as invertebrate eggs typically contain little carbohydrate and instead are composed primarily of energy-dense protein and lipid (1, 2). After validating our methods (by using them to estimate energy content and AFDW of the eggs of a previously studied echinoderm) and reexamining published data on the energy contents of echinoderm eggs, we conclude that dichromate oxidation often underestimates the energy contents of small eggs of marine invertebrates. This systematic error, which is likely related to the tendency of the assay to incompletely oxidize proteins, can only be corrected with substantial independent data on egg biochemical composition. We thus suggest that dichromate oxidation should not be used for routine measurement of the total energy content of marine invertebrate eggs.

Originally published in Biological Bulletin and used with permission.

]]> William Jaeckle et al. Biology Growth and energy imbalance during the development of a Lecithotrophic Molluscan Larva (<em>Haliotis rufescens</em>) http://digitalcommons.iwu.edu/bio_scholarship/25 http://digitalcommons.iwu.edu/bio_scholarship/25 Thu, 30 Sep 2010 10:48:42 PDT Larvae of the gastropod Haliotis rufescens are classified as "nonfeeding" because they cannot capture particular foods. However, for only 1 out of 5 independent cultures was a net decrease observed in dry organic weight during the complete period of larval development (5 to 7 days). In fact, there were net increases in dry organic weight from the oocyte (day 0) to the newly formed veliger larvae (2-day-old). These weight increases during early development could be explained by increases in the amounts of specific biochemical components of the larvae, relative to oocytes. The metabolic rates of larvae were measured (oxygen consumption) and used to compare (i) the reuired energy for development with (ii) the energy supplied from the catabolism of biochemical reserves. This analysis revealed that the cost of development for larvae could not be explained by the rates of use of the energy stores initially present in the oocyte. Larvae, from two independent cultures, could only supply 25% or 71% of their energy requirements by the use of internal reserves. Larvae of H. rufescens cannot use particulate foods and, thus, this energy resources cannot be invoked. Estimates of the contribution that dissolved organic material in seawater could provide to larvae, showed that this pool of exogenous material could supply the missing energy. It is suggested that "nonfeeding" larvae can feed, but that their only available nutrients are in a dissolved form.

]]> William Jaeckle et al. Amino Acid Uptake and Metabolism by Larvae of the Marine Worm <i>Urechis caupo</i> (Echiura), a New Species in Axenic Culture http://digitalcommons.iwu.edu/bio_scholarship/24 http://digitalcommons.iwu.edu/bio_scholarship/24 Thu, 30 Sep 2010 10:48:41 PDT Axenic (bacteria-free) larval cultures of the marine echiuran worm, Urechis caupo, were reliably obtained by aseptically removing gametes directly from the gamete storage organs. Trochophore larvae only removed neutral amino acids from seawater as measured by high-performance liquid chromatography (HPLC). There was no detectable uptake, as measured by HPLC, of acidic or basic amino acids. Kinetic analysis showed that the transport system for alanine in 4-day-old larvae had a Kt of 4-6 μM and a Jmax of 9-10 pmol larva-1 h-1. Following a 50-min exposure, the majority of the radio-activity (95%) from 14C-alanine was found in the trichlo-roacetic acid-soluble fraction. Very little label appeared as acid-insoluble material, and there was no detectable lipid biosynthesis from 14C-alanine. Approximately 12% of the total alanine transported was released in the form of 14CO2. Thin-layer chromatography of intracellular free amino acid pools demonstrated that aspartic acid and glutamic acid were radiolabeled from the alanine precursor. A comparison of the energy acquired from the transport of alanine, with the metabolic rate of 4-day-old larvae, revealed that 51% of the metabolic demand could be provided by the transport and complete catabolism of this single amino acid at a concentration of 595 nM in seawater.

Originally published in Biological Bulletin and used with permission.

]]> William Jaeckle et al. Biology Axenic Culture A Long Way From Home: Transatlantic Sea Star Migration http://digitalcommons.iwu.edu/bio_scholarship/22 http://digitalcommons.iwu.edu/bio_scholarship/22 Thu, 30 Sep 2010 10:48:39 PDT For a marine biologist strolling along the eastern coast of South America, finding some sea stars (popularly called starfish, and technically members of the class Asteroidea of the phylum Echinodermata) is not all that unusual. However, when closer inspection reveals the sea stars to be ones that are also found on the shores of the western coast of Africa, the marine biologist now faces an interesting question: How did these sea stars come to be so far from home?

Originally published in Consortiumand used with permission.

]]> William Jaeckle et al. Biology Ontogenic Changes in the Rates of Amino Acid Transport from Seawater by Marine Invertebrate Larvae (<em>Echinodermata, Echiura, Mollusca</em>) http://digitalcommons.iwu.edu/bio_scholarship/23 http://digitalcommons.iwu.edu/bio_scholarship/23 Thu, 30 Sep 2010 10:48:39 PDT Transport rates of amino acids were determined for larvae of different ages of the echiuran worm Urechis caupo, the gastropod Haliotis rufescens, the bivalve Crassostrea gigas, and the sea urchin Strongylocentrotus purpuratus. All larval forms showed an increase in the transport rate of amino acids during development. Trochophores of U. caupo increased their rate of net flux for each of 5 amino acids (100 nM each) by a factor of 1.6 and 2.2 during 1-3 days and 4-8 days, respectively, for two independent cultures. In H. rufescens, the maximum transport capacity (Jmax) for alanine increased 3-fold during the 24 h required for the trochophore to develop into a veliger. In C. gigas veligers, there was a 9-fold increase in the maximum transport capacity for alanine during larval development from an 80 μm to a 300 μm larva. In sea urchins, the prism-stage larvae (2-day-old) had an alanine transport system with a Kt of 1.9 μM and a Jmax of 8.1 pmol larvae -1h-1. The kinetics of alanine transport in the pluteus-stage (4-day-old) were best described by two systems (System I: Kt = 1.0 μM with a Jmax of 5.6 pmol larva -1h-1; System II: Kt = 132.0 μM with a Jmax of 8.4 pmol larva -1h-1). In larvae of C. gigas, the relationships between the rate of alanine transport and body size was described by the equation, log Jmax (pg larva-1h-1) = 1.6894(X) + (-0.5937), where X is the shell length in μm. It is illustrated that the allometric increased in respiration rates, during the growth of bivalve larvae, is matched by an ontogenic increase in amino acid transport capacity.

]]> Donal T. Manahan et al. The Potential for Ontogenetic Vertical Migration by Larvae of Bathyal Echinoderms http://digitalcommons.iwu.edu/bio_scholarship/21 http://digitalcommons.iwu.edu/bio_scholarship/21 Thu, 30 Sep 2010 10:48:37 PDT Planktotrophy is a relatively common developmental mode among bathyal and abyssal echinoderms, but the sources of food used by deep-sea planktotrophic larvae remain generally unknown. Very few deep-sea echinoderm larvae have been collected in plankton samples, so we do not know whether larvae migrate to the euphotic zone to feed or if they rely on bacteria or detritus at greater depths. We approached this question indirectly by investigating whether larvae of bathyal echinoids can tolerate the temperatures they would encounter in the euphotic zone and whether they possess sufficient energy stores to migrate to the euphotic zone without feeding. Twenty-four hour survival at 20 and 24 °C was always much lower than survival at colder temperatures, but there were species-specific and stage-specific differences in temperature tolerances. A numerical model of the energy consumed by migrating larvae predicted that larvae should be able to reach adequate phytoplankton concentrations before exhausting parental reserves, unless they swim very slowly and have very high metabolic rates. These results suggest that long vertical migrations are more likely to be limited by physiological tolerances than by energy stores.

]]> William Jaeckle et al. Biology Marine Biology <em>Rhodobacter capsulatus</em> Porphobilinogen Synthase, a High Activity Metal Ion Independent Hexamer http://digitalcommons.iwu.edu/bio_scholarship/20 http://digitalcommons.iwu.edu/bio_scholarship/20 Thu, 30 Sep 2010 10:48:36 PDT David Bollivar The Chlorophyll Biosynthetic Enzyme Mg-Protoporphyrin IX Monomethyl Ester (Oxidative) Cyclase http://digitalcommons.iwu.edu/bio_scholarship/19 http://digitalcommons.iwu.edu/bio_scholarship/19 Thu, 30 Sep 2010 10:48:35 PDT David Bollivar Nucleotide Sequence of S-Adenosyl-L-Methionine: Magnesium Protoporphyrin Methyltransferase from <em>Rhodobacter capsulatus</em> http://digitalcommons.iwu.edu/bio_scholarship/18 http://digitalcommons.iwu.edu/bio_scholarship/18 Thu, 30 Sep 2010 10:48:35 PDT David Bollivar Molecular Genetic Analysis of Terminal Steps in Bacteriochlorophyll <em>a</em> Biosynthesis: Characterization of a <em>Rhodobacter capsulatus</em> Strain that Synthesizes Geranylgeranoil-Esterified Bacteriochlorophyll <em>a</em> http://digitalcommons.iwu.edu/bio_scholarship/17 http://digitalcommons.iwu.edu/bio_scholarship/17 Thu, 30 Sep 2010 10:48:34 PDT David Bollivar Genetic Analysis of Chlorophyll Biosynthesis http://digitalcommons.iwu.edu/bio_scholarship/15 http://digitalcommons.iwu.edu/bio_scholarship/15 Thu, 30 Sep 2010 10:48:33 PDT David Bollivar Heterologous Expression of the <em>bchM</em> Gene Product from <em>Rhodobacter capsulatus</em> and Demonstration that it Encodes S-Adenosyl-L-Methionine: Mg-Protoporhyrin IX Methyltransferase http://digitalcommons.iwu.edu/bio_scholarship/16 http://digitalcommons.iwu.edu/bio_scholarship/16 Thu, 30 Sep 2010 10:48:33 PDT David Bollivar Genetic Analyses of Photopigment Biosynthesis in Eubacteria: a Guiding Light for Algea and Plants http://digitalcommons.iwu.edu/bio_scholarship/14 http://digitalcommons.iwu.edu/bio_scholarship/14 Thu, 30 Sep 2010 10:48:32 PDT David Bollivar