Exploring the distribution and physiological roles of bacterial membrane lipids in the marine environment

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 2010Lipids have a legacy in the geologic record extending back to the Archaean. Since the phylogenetic diversity of life is reflected in the structural diversity of biomolecules, lipid biomarkers that are shown to be diagnostic of certain organisms that carry out specific biochemical processes or that are demonstrated to have unique physiological roles can be used to trace the biogeochemical influence of bacteria in modern and ancient environments. In this thesis I explore the application of two classes of bacterial membrane lipids as biomarkers for marine biogeochemical processes in marine environments: ladderanes and hopanoids. Through the detection of ladderane lipids – biomarkers for anaerobic ammonium oxidizing (anammox) bacteria – I demonstrate the presence and distribution of anammox bacteria in a subterranean estuary. Through a survey of hopanoids in marine environments and cultured marine cyanobacteria I show that hopanoids are ubiquitous in the oceans and that their presence in ancient marine sediments could provide information about biogeochemical processes in past environments. Based on novel results demonstrating that hopanoids are resistant to extraction by non-ionic detergent, I propose that they may play a role in lipid ordering and the formation of putative lipid rafts in hopanoid-producing bacteria.This work was supported by National Science Foundation grants to R.E. Summons and T.I. Eglinton (ETBC 084990) an American Chemical Society Petroleum Research Fund to R.E. Summons (ACS PRF 46838-AC2), and a WHOI OLI Tropical Initiatives grant to T.I. Eglinton and J. Waterbury. I received support from an NSF Graduate Research Fellowship, Dan David Doctoral Fellowship, WHOI COI Student Fellowship, and a WHOI Ocean Ventures Fund

Last breath

Last Breath is a Gothic Web Series about a girl who recreates her identity while recovering her lost memory. She discovers dark family secrets and a rigid society that is as equally imprisoning as her room. Ultimately, she engages in a game of intrigue, putting her family name and soul at stake. The story incorporates traditional Gothic and Southern Gothic influences described by Bailey, De Vore et al., Radcliffe, and others. The issue of format is analyzed using insights by Felicia Day, Syd Field, Tennessee Williams, and Robert McKee. The Web Series remains a pioneering medium. Shows such as The Spot, The Guild, and House of Cards embraces innovations in the webisode, as I attempt to do with the genre and formatting of Last Breath. Much in the same way Tennessee Williams transcended mediums, Last Breath recognizes classical traditions which may be applied in defining and refining the web series

Allometry, sexual size dimorphism, and niche partitioning in the Mediterranean gecko (Hemidactylus turcicus)

Hemidactylus tucrius is a small gekkonid lizard native to the Middle East and Asia that is known to exhibit sexual dimorphism in head size. Several potential explanations exist for the evolution and maintenance of sexual dimorphism in lizards. We tested 2 of these competing hypotheses concerning diet partitioning and differential growth. We found no differences in Average meal size (volume) or in any single dimension of prey size for similarly sized males and females. allometric patterns of increases in head size also were measured in males and females. We found that males exhibited a mixture of isometric and positively allometric patterns of head size increases, whereas females exhibited isometric and negatively allometric patterns. Thus, we concluded that sexual dimorphism in head size is not the result of diet partitioning but instead of differential growth patterns following sexual maturity in males and females

An unusually large number of eggs laid by a breeding red-cockaded woodpecker female

The Red-cockaded Woodpecker (Picoides borealis) is a cooperatively breeding species that typically uses a single cavity for nesting (Ligon 1970, Walters et al. 1988). A single tree, or aggregation of cavity trees, termed the cluster, is inhabited by a group of woodpeckers that includes a single breeding pair and up to several helpers, which are typically male offspring of previous breeding seasons (Ligon 1970, Lennartz et al. 1987). Each group of Red-cockaded Woodpeckers usually produces one nest per breeding season, but will often nest again during the same breeding season if the first nest fails. Double clutching and double brooding (where both nests are successful) are known to occur in Red-cockaded Woodpeckers in the southern and northern portion of the species\u27 range (LaBranche et al. 1994, Franzreb 1997, Phillips et al. 1998)

Are Pileated Woodpeckers Attracted to Red-Cockaded Woodpecker Cavity Trees?

Pileated Woodpeckers (Dryocopus pileatus) cause damage to Red-cockaded Woodpecker (Picoides borealis) cavity trees in the form of cavity enlargement or other excavations on the surface of the pine tree. However, it is not known whether Pileated Woodpeckers excavate more frequently on Red-cockaded Woodpecker cavity trees than on noncavity trees or how stand structure is related to the frequency of Pileated Woodpecker excavation. Also, it is unclear whether the cavity itself provides the stimulus to Pileated Woodpeckers to excavate or whether the presence of Red-cockaded Woodpeckers and their activities are attracting them. We surveyed all of the Red-cockaded Woodpecker cavity trees (n = 202) and 110 control trees in the loblolly (Pinus taeda)-shortleaf (P. echinata) pine habitat on the Angelina National Forest for recent Pileated Woodpecker excavation and found that approximately 7.4% of all cavity trees were damaged while no control trees showed any evidence of Pileated Woodpecker damage. The rate of Pileated Woodpecker excavation was negatively associated with hardwood midstory height and density. Pileated Woodpeckers appeared to focus most of their excavations on Red-cockaded Woodpeckers cavity entrances. WC suggest that Pileated Woodpeckers may be attracted to Red-cockaded Woodpecker cavity trees. especially the cavity, and that midstory removal used to improve Red-cockaded Woodpecker habitat may increase the incidence of damage to the cavity trees by Pileated Woodpeckers in the current fragmented landscape

Delayed reproduction of translocated Red-cockaded Woodpeckers.

Twelve pairs of Red-cockaded Woodpeckers were translocated to the Angelina National Forest. Five breeding pairs produced eggs/nestlings within the first breeding season after translocation. Clutch initiation dates for all five pairs were later than those of resident breeders. The observed delay in reporductive timing by translocated woodpeckers may have resulted from a variety of factors

An automated technique for monitoring nocturnal avian vocalizations.

Using audio recording dataloggers, we collected nocturnal bird vocalizations at different sites within the Davy Crockett National Forest and the Stephen F. Austin Experimental Forest. We detected vocalizations of a variety of nocturnal and diurnal species. This technology is useful for its application to avifauna

Influence of Habitat and Number of Nestlings on Partial Brood Loss in Red-Cockaded Woodpeckers

Partial brood loss in red-cockaded woodpeckers (Picoides borealis) was studied during 2 breeding seasons in eastern Texas. The timing of partial brood loss, group size, number of initial nestlings, number of birds fledged, and habitat characteristics of the group\u27s cavity-tree cluster were examined for 37 woodpecker groups in loblolly- (Pinus taeda) shortleaf (P. echinata) pine habitat and 14 groups in longleaf (P palustris) pine habitat. Partial brood loss occurred slightly more in the loblolly-shortleaf pine habitat than in the longleaf pine habitat, largely because nests in loblolly-shortleaf habitat initially contained more nestlings. There was a trend for more young to be fledged by groups of 4 and 5 adult woodpeckers than by groups with only 2 or 3 adult birds. Partial brood loss was greater in nests with 4 initial nestlings than in nests with 3 or fewer nestlings. Partial brood loss was always observed in nests that initially contained 4 nestlings. When nests contained 3 nestlings, partial brood loss was significantly greater in clusters where hardwood midstory was present than in clusters where hardwood midstory was minimal, consistent with the brood reduction theory. Red-cockaded woodpeckers typically laid more eggs than they could possibly fledge young, lending support to the insurance egg hypothesis

The influence of predator threat on the timing of a life-history switch point: predator-induced hatching in the southern leopard frog (Rana sphenocephala)

We tested the hypotheses that potential egg predators, crayfish Procambarus nigrocinctus and dytiscid Cybister sp. larvae, would accelerate the timing of hatching and that a larval predator, dragonfly naiad Anax junius, would delay hatching in the southern leopard frog (Rana sphenocephala). We also tested the hypothesis that differences in response would be proportional to predator lethality. Our results indicate that our hypotheses were partially supported. The presence of an efficient egg predator (crayfish) induces hatching faster than a less efficient predator (dytiscid larvae). However, the presence of a larval predator (naiads) did not delay hatching. Eggs that developed in the presence of egg predators produced hatchlings that were shorter (total length) than those reared in the presence of larval predators or those reared in the absence of predators. We suggest that earlier hatching times should decrease vulnerability to egg predators but result in shorter hatchlings

Accelerated Hatching of Southern Leopard Frog (Rana sphenocephala) Eggs in Response to the Presence of a Crayfish (Procambarus nigrocinctus) Predator

Phenotypic plasticity, such as morphological and behavioral changes in response to predators, is common in larval anurans. Less is known about inducible defenses in the embryonic stages of development. We investigated the predation risk imposed by crayfish (Procambarus nigrocinctus) on southern leopard frog (Rana sphenocephala) eggs aud whether crayfish presence induces a change in the timing of hatching of R. sphenocephala eggs. We found that crayfish significantly reduce the hatching success of R. sphenocephala eggs by eating them and that eggs hatch significantly faster in the presence of crayfish than when crayfish are not present. We also found that the nonlethal presence of crayfish (caged with no access to eggs) induced accelerated hatching, indicating that injured conspecifics are not required to elicit the response. Reception of chemical cues produced or released by crayfish may play an important role in survival of R. sphenocephala eggs