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In this study, features of ecology, behavior, and functional morphology related to feeding activity of two populations of the amphipod Gammarus minus were compared. The two populations occupied different habitats, and I attempted to determine whether differences observed between the two populations were related to habitat. Annual production and life history of the populations were compared and their relationship to factors such as temperature, water-chemistry, and quantity of available organic matter were examined. Mouthpart and foregut morphology were compared between the two populations and between immature and mature amphipods with light and scanning electron microscopy. Measurements of structure were analyzed by linear regression. A behavioral study, comparing feeding of immature and mature G. minus, was conducted in the laboratory. Annual production of G. minus occupying a habitat characterized by the presence of watercress, gravel substrate, and constant temperature (Site 1) was 3.9 g/m² (95% C.I.: 3.2- 4.5), while that in the habitat characterized by leaf detritus and fluctuating temperatures (Site 2) was 1.8 g/m² (95% C.I.: 1.6-2.1). Breeding occurred throughout the year at Site 1, but there was a yearly cycle at Site 2. The greatest numbers of the smallest size classes of amphipod were present at Site 2 when the quantity of ash-free dry mass (AFDM) of wood and bark was greater than AFDM of leaf detritus. Of nine mouthpart and foregut structures studied, three, the number of cuspidate setae on outer plates of maxillipeds, the length of the dactyl on maxilliped palps, and the number of hook setae on the foregut ampullae, were found to be correlated with body length. Of these, rates of increase in maxilliped setae numbers and hook setae numbers were greater for immature than mature animals, and the number of hook setae for a given sized animal was generally greater for animals at Site 1 than Site 2. Animals presented with ground-up leaf material in the laboratory exhibited twenty-one recognizable behaviors. The frequencies of six behaviors were found to be statistically different between immature and mature animals. The differences suggest that immatures may prefer a food type or size other than that provided in the experiment. / Ph. D.

Predatory gastropods (Neogastropoda) feed with a proboscis (elongate snout) and complex foregut. The presence of developmental modules (semi-autonomous components) in foregut development may have facilitated emergence of predatory feeding. In species with indirect development (feeding larval stage) physical and temporal separation of developing foregut modules (dorsal=larval esophagus; ventral=juvenile feeding structures) allows larval feeding and rapid switch to carnivory. However, previous studies on neogastropods with direct development (no feeding larval stage) did not identify foregut developmental modules. Thus, I investigated foregut development in two predatory, direct developing neogastropods: Nucella lamellosa and N. ostrina (Muricoidea), using histological sectioning, 3D reconstructions, TEM, and SEM. In both species, I showed evidence for dissociable dorsal and ventral foregut developmental modules. In N. lamellosa, the two modules were physically separate, although they were not separate in N. ostrina. My results reconcile differences in previous descriptions of foregut development between neogastropods with indirect and direct development. / Graduate

<p>Sonic hedgehog (Shh) is a critical secreted signaling molecule that regulates many aspects of organogenesis. In the absence of Shh, many organs, including the foregut, larynx, palate, cerebellum and heart do not form properly. However, the cellular details of the roles of Shh, including the relevant domains of Shh expression and reception, have not been elucidated for many of these processes. </p><p>The single embryonic foregut tube must divide into the trachea and esophagus, which does not occur in the Shh-null mutant. In Chapter 5, I use Cre-Lox technology to determine that the ventral foregut endoderm is the relevant source of Shh for this process and the mesoderm must directly receive that Shh signal. Surprisingly, this signaling event appears to occur two days before the foregut begins to divide, indicating an early essential role for Shh in foregut division. </p><p>Shh is also expressed at later stages in the maturing trachea and esophagus. In Chapter 6, I demonstrate that these domains serve to establish differentiated mesoderm. In the trachea, Shh from the endoderm signals directly to the mesoderm to form the tracheal cartilage rings. In the esophagus, the roles of Shh are more complex. Shh regulates the size of the esophagus and controls patterning of the concentric rings of esophageal mesoderm, however this process seems to be indirect, requiring autocrine Shh signaling within the esophageal endoderm. </p><p>The laryngeal apparatus is entirely absent in the Shh-null mouse. I n Chapter 3, I dissect the domains of Shh expression and reception required for laryngeal development and demonstrate that loss of endodermal Shh expression causes laryngotracheoesophageal clefts and malformed laryngeal cartilages. As much of laryngeal morphogenesis poorly understood, I also utilize dual mesodermal and neural crest fate maps to determine the embryonic origins of various laryngeal tissues. Finally, as Shh signaling often occurs in concert with Bone Morphogenic Protein (BMP) signaling, I investigate the roles of BMP signaling in laryngeal development. </p><p>Much of Shh signaling occurs at the primary cilium, to which Smoothened, a critical pathway member, must translocate upon Shh signal transduction. This process requires a Smo-Kif3a-&#946;arretin complex in mammalian cell culture. However, the roles of &#946;arrestins in mouse development, and their relationship to Shh signaling have not been investigated in vivo. To do so, in Chapter 4, I analyze the phenotypes of the &#946;arr1/&#946;arr2 double knockout embryos and demonstrate that they have palatal, cerebellar, cardiovascular and renal defects consistent with a specific impairment of mitogenic Shh signaling. </p><p>Altogether, my work dissects the cellular details of Shh signaling during multiple organ systems in the mouse embryo. I further analyze the consequences of absent or misregulated Shh signaling across multiple developmental contexts and determine that Shh plays critical and diverse roles in organogenesis.</p> / Dissertation

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FoxA transcription factors are central regulators of gut development in all species. In C. elegans, pha-4/FoxA is necessary to generate cells of the foregut, or pharynx. FoxA factors need to be precisely regulated for proper development, yet we know very little about FoxA regulation. To look for potential genes that act as pha-4 regulators, the Mango lab previously conducted two screens for suppressors of the lethality associated with a partial loss of pha-4 activity. Both screens uncovered smg-8, a novel gene that is highly conserved amongst metazoans. Interestingly, the human homolog of smg-8 is amplified in some breast cancers, which also depend on FoxA1. This observation makes smg-8 a very exciting gene to investigate. The goal of my thesis is to analyze smg-8 to better understand its function and potential role as a candidate regulator of pha-4/FoxA, using C. elegans as a model system. In this thesis, I show that C. elegans smg-8 does not have a role in the Nonsense Mediated Decay pathway. I find that smg-8 modulates pha-4 protein levels during embryonic development. This work is the first direct evidence that smg-8 is a modulator of pha-4. I used biochemical and bioinformatic approaches to uncover possible partners of smg-8. These approaches identified several interesting candidates that will help place C. elegans smg-8 in a functional pathway. This work has expanded our understanding of smg-8 function and lays the foundation for further investigation of the role of this novel gene as a regulator of pha-4/FoxA in C. elegans.

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Innerhalb der Decapoda stellt das Taxon Brachyura eines der artenreichsten Taxa mit bis zu 10000 Arten dar. Die Phylogenie der Brachyura wird aufgrund morphologischer und molekularer Untersuchungen seit mehr als ein Jahrhundert kontrovers diskutiert. Zur Klärung phylogenetischer Fragestellungen wurde mit den vergleichenden Untersuchungen der Magenossikel und der Magenzähne von 66 Taxa der Brachyura ein neuer phylogenetischer Ansatz gewählt. Mit Anwendung eines spezifischen Färbepigmentes, Alizarin-Rot S, konnten sechs neue Magenossikel einer bereits existierenden Nomenklatur hinzugefügt werden, so dass jetzt 41 Magenossikel für das Grundmuster der Brachyura angenommen werden können. Im Ergebnis der phylogenetischen Analyse wird ein monophyletisches Taxon Brachyura einschließlich der Taxa Dromiidae und Raninidae unterstützt. Die von Guinot (1977, 1978) als Monophyla postulierten Teiltaxa Podotremata und Heterotremata finden hier keine Unterstützung. Taxa wie Raninidae und Cymonomidae, welche aufgrund der coxalen Position ihrer Genitalporen dem Taxon Podotremata sensu Guinot zugeschrieben werden, weisen nach vorliegenden Daten eine nähere Verwandtschaft zu den "höheren" Krabben auf. Eine Monophylie eines Taxons Thoracotremata sensu Guinot kann dagegen basierend auf den analysierten Magenstrukturen, aber auch auf der Grundlage molekularer Studien (Schubart et al. 2000a, 2000b) und dem vorliegenden Daten zum Fossilbericht angenommen werden. Eine basale Stellung der Dynomenidae und Dromiidae im Ergebnis der kladistischen Analyse lässt sich mit den Fossilfunden aus dem mittleren Jura in Übereinstimmung bringen. Des weiteren kann für die meisten Taxa der "höheren" Krabben ein gemeinsamer Vorfahre für die obere Kreide bzw. bis zum Beginn des Tertiärs postuliert werden. / Within the Decapoda the taxon Brachyura is the species-richest taxon with up to 10000 species. The phylogeny of the Brachyura has been discussed based on morphological and molecular investigations since more than a century. The investigation of the foregut-ossicles and gastric-teeth of 66 brachyuran species, is a new approach to answer important phylogenetic questions. Using a specific staining pigment Alizarin Red S, six new described foregut-ossicles are added to an existing nomenclature. As a result of this method the presence of 41 foregut-ossicles is proposed for the ground pattern of the Brachyura. The cladistic analysis supports a monophyletic origin of the Brachyura including the Dromiidae and the Raninidae. The taxa Podotremata and Heterotremata, postulated as monophyletic by Guinot (1977, 1978), are not supported in the present study. The Dromiidae and Raninidae, which are placed within the Podotremata sensu Guinot, are closer related to the "higher crabs". Based on the analysed foregut-characters, several molecular studies (Schubart et al. 2000a, 2000b), and the data of the fossil record, a monophyletic origin of the Thoracotremata sensu Guinot is suggested. The analysed basal position of the Dynomenidae and Dromiidae is in agreement with the brachyuran fossil record. A common ancestor for most of the "higher" brachyuran crabs is suggested for the period between the upper Cretaceous and the beginning of the Tertiary.