Phylogenetics of Aplanulata (Cnidaria: Hydrozoa) and the evolution and development of Ectopleura larynx

The model organism Hydra belongs to the hydrozoan clade Aplanulata. Despite being a popular model system for diverse fields of biological research, the morphology and development of Hydra are atypical of most hydrozoans. For example, most hydrozoans develop gonophores (structures housing gametes) on the body of the polyp, or release free-swimming medusae that spawn in the water column. In contrast, Hydra produce no gonophores or medusae and instead form gametes directly in the epithelia of the body column. Additionally, Hydra embryos are difficult to isolate for developmental studies (embryos encyst and are thus difficult to study), so there is currently no model species in Aplanulata for examining gene expression in developing polyps. In this dissertation, I examine the phylogenetic relationships of Aplanulata and the clade Capitata sensu stricto, originally thought to group with Aplanulata, and examine the evolution and development of the Aplanulata species Ectopleura larynx. This close relative of Hydra is ideally suited for evolutionary developmental studies because it develops directly in brooding structures, and produces attached gonophores. Because Ectopleura larynx broods on the body of the polyp, its juveniles and gonophores are easily procured for gene expression and developmental studies. My examination of Ectopleura larynx development reveals a unique type of colony formation that has never before been described in Hydrozoa in that Ectopleura larynx colonies form through sexual reproduction followed by epithelial fusion of offspring polyps to adult colonies. I characterize the expression of the paired-like homeobox gene manacle to determine polyp-colony boundaries, and suggest that stalks beneath the neck of Ectopleura larynx polyps do not have polyp identity and instead are specialized structures that interconnect polyps (stolons). Lastly, I characterize the canonical Wnt pathway in Ectopleura larynx, and examine its role in axial patterning of polyp and gonophore structures. My results are consistent with the Wnt pathway playing a role in patterning oral structures of the polyp and gonophore, and suggest that changes in expression patterns of Wnt pathway genes could explain the sexually-dimorphic morphologies of male and female gonophores of Ectopleura larynx, and the truncation of medusa development in this species

A comparative study of the public relations programs and policies in schools and businesses

Thesis (Ed.M.)--Boston Universit

A Novel Mode of Colony Formation in a Hydrozoan through Fusion of Sexually Generated Individuals

SummaryColoniality, as displayed by most hydrozoans, is thought to confer a size advantage in substrate-limited benthic marine environments and affects nearly every aspect of a species' ecology and evolution [1,2]. Hydrozoan colonies normally develop through asexual budding of polyps that remain interconnected by continuous epithelia. The clade Aplanulata is unique in that it comprises mostly solitary species, including the model organism Hydra, with only a few colonial species [3,4]. We reconstruct a multigene phylogeny to trace the evolution of coloniality in Aplanulata, revealing that the ancestor of Aplanulata was solitary and that coloniality was regained in the genus Ectopleura. Examination of Ectopleura larynx development reveals a unique type of colony formation never before described in Hydrozoa, in that colonies form through sexual reproduction followed by epithelial fusion of offspring polyps to adults. We characterize the expression of manacle, a gene involved in foot development in Hydra [5], to determine polyp-colony boundaries. Our results suggest that stalks beneath the neck do not have polyp identity and instead are specialized structures that interconnect polyps. Epithelial fusion, brooding behavior, and the presence of a skeleton were all key factors behind the evolution of this novel pathway to coloniality in Ectopleura

Optical manipulation of a single Mn spin in a CdTe-based quantum dot

A system of two coupled CdTe quantum dots, one of them containing a single Mn ion, was studied in continuous wave and modulated photoluminescence, photoluminescence excitation, and photon correlation experiments. Optical writing of information in the spin state of the Mn ion has been demonstrated, using orientation of the Mn spin by spin-polarized carriers transferred from the neighbor quantum dot. Mn spin orientation time values from 20 ns to 100 ns were measured, depending on the excitation power. Storage time of the information in the Mn spin was found to be enhanced by application of a static magnetic field of 1 T, reaching hundreds of microseconds in the dark. Simple rate equation models were found to describe correctly static and dynamical properties of the system.Comment: 4 pages, 3 figure

An Evolutionary Perspective on Human Cross-sensitivity to Tree Nut and Seed Allergens

Tree nut allergies are some of the most common and serious allergies in the United States. Patients who are sensitive to nuts or to seeds commonly called nuts are advised to avoid consuming a variety of different species, even though these may be distantly related in terms of their evolutionary history. This is because studies in the literature report that patients often display sensitivity to multiple nut species (cross-sensitivity) if they have an existing nut allergy. These reports suggest that cross-sensitivity in patients with nut allergies may be caused by an IgE antibody reacting with epitopes present in the seed proteins of different species (cross-reactivity), for example, if IgE isolated from the serum of a patient were able to bind to both almond and peanut allergens. We hypothesize that allergenic proteins in seeds may have similar amino acid sequences that cause the observed cross-sensitivity. Here, we test the hypothesis that similarity in the protein sequences of allergenic nuts drives cross-sensitivity and cross-reactivity by reconstructing the gene trees of three allergenic seed-storage proteins (vicilin, legumin, and 2S albumin) from species sampled across vascular plants. We generate estimates of their phylogenetic relationships and compare these to the allergen cross-sensitivity and cross-reactivity data that is reported in the literature. In general, evolutionary relationships of the three proteins are congruent with the current understanding of plant species relationships. However, we find little evidence that distantly related nut species reported to be cross-reactive share similar vicilin, legumin, or 2S albumin amino acid sequences. Our data thus suggest that features of the proteins other than their amino acid sequences may be driving the cross-reactivity observed during in vitro tests and skin tests. Our results support current treatment guidelines to limit nut and seed consumption if allergies are present in a patient. More studies are necessary to better understand the characteristics of allergenic proteins and patterns of cross-sensitivity in patients who suffer from nut allergies