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The distribution of benthic polychaetes in the Mississippi Canyon was examined to evaluate impacts of environmental variables on species assemblages. Environmental variables considered included depth, bathymetric slope, hydrographic features, sediment grain size, food availability and sediment contamination. Samples were collected using GOMEX boxcorer. Density decreased with increasing depth exponentially. Diversity exhibited a unimodal pattern with depth with a maximum value in the intermediate depth range (about 1269 m). Deposit feeders were the most abundant feeding guild. Both the feeding guilds and faunal composition could be divided into three groups along the depth gradient: shallow (300 – 800 m), intermediate (800 – 1500 m) and deep (> 1500 m). Results of statistical analyses revealed that depth was the most important determinant in organizing polychaete assemblages in the study area. The Mississippi Canyon and the Central Transect (a non-canyon area) were found not contaminated by trace metals or Polynuclear Aromatic Hydrocarbons (PAHs) in sediments, although the highest PAHs concentration occurred at the head of the Canyon, MT1. The mean density was higher in the Mississippi Canyon (1668 N/m2) than in the Central Transect (979 N/m2), while the mean diversity in the Canyon (ES(100) = 26.9 ) was lower than the Central Transect (ES(100) = 33.1). Large amounts of terrigenous input from the Mississippi River to the Canyon could enhance polychaete density and accelerate competitive exclusion, and thus lead to lower diversity. The faunal composition was significantly different between the two transects, with higher species richness in the Mississippi Canyon (301 species). This could be attributed to structure complexity in the Mississippi Canyon. The distribution of feeding guilds was similar between two transects. The differences observed in polychaete assemblages between two transects may be largely due to high terrigenous sediment and organic matter input to the Mississippi Canyon by the Mississippi River.

In most animals, oogenesis involves a syncytial “cyst” stage. Cysts are produced by incomplete mitotic divisions of gonial precursor cells, leaving the resulting cystocytes interconnected by cytoplasmic bridges. The bridges subsequently break down, liberating the developing gametes. In some animals (e.g. meroistic insects) cysts are “polarized”, such that certain cystocytes differentiate as supportive nurse cells, rather than oocytes. The variability of cysts in animal oogenesis contrasts with the relative universality of spermatogenic cysts, making the functional importance of cysts in oogenesis unclear. I have studied oogenesis in a polychaete worm, Ophryotrocha labronica (Annelida: Dorvilleidae). These worms produce polarized, two-celled oogenic cysts with one nurse cell and one oocyte. Such cysts resemble their better-characterized counterparts in meroistic insects. However, using a variety of light- and electron-microscopic techniques, I show here that the resemblance between O. labronica and meroistic insects is largely superficial. Rather, the roles of nurse cells and the mechanisms underlying cystocyte differentiation are quite distinct in both groups. Therefore, similarities between these polychaetes and insects are probably examples of convergent evolution rather than homology. These observations underscore the plasticity of oogenesis among animals. Mechanisms by which germ cells become distinct from somatic cells in animals are also a subject of considerable research activity. Two general modes of germ-cell specification have been described in animals: deterministic specification, which is typical of established model species (e.g., Drosophila melanogaster and Caenorhabditis elegans) and inductive specification, which, though it is the more-common mode among animals, has not been well studied. As an annelid worm, O. labronica likely specifies its germ cells inductively, and therefore has potential to serve as a model species for studies of inductive germ cell specification. Realizing this potential, however, will require the development of genetic resources for this species. I describe the beginnings of such work here: the isolation and characterization of a vasa/PL10-like gene whose expression is largely restricted to germ cells, the construction of a cDNA library, and the refinement of methods for in situ hybridization and immunostaining to visualize gene expression in whole worms.

In most animals, oogenesis involves a syncytial “cyst” stage. Cysts are produced by incomplete mitotic divisions of gonial precursor cells, leaving the resulting cystocytes interconnected by cytoplasmic bridges. The bridges subsequently break down, liberating the developing gametes. In some animals (e.g. meroistic insects) cysts are “polarized”, such that certain cystocytes differentiate as supportive nurse cells, rather than oocytes. The variability of cysts in animal oogenesis contrasts with the relative universality of spermatogenic cysts, making the functional importance of cysts in oogenesis unclear. I have studied oogenesis in a polychaete worm, Ophryotrocha labronica (Annelida: Dorvilleidae). These worms produce polarized, two-celled oogenic cysts with one nurse cell and one oocyte. Such cysts resemble their better-characterized counterparts in meroistic insects. However, using a variety of light- and electron-microscopic techniques, I show here that the resemblance between O. labronica and meroistic insects is largely superficial. Rather, the roles of nurse cells and the mechanisms underlying cystocyte differentiation are quite distinct in both groups. Therefore, similarities between these polychaetes and insects are probably examples of convergent evolution rather than homology. These observations underscore the plasticity of oogenesis among animals. Mechanisms by which germ cells become distinct from somatic cells in animals are also a subject of considerable research activity. Two general modes of germ-cell specification have been described in animals: deterministic specification, which is typical of established model species (e.g., Drosophila melanogaster and Caenorhabditis elegans) and inductive specification, which, though it is the more-common mode among animals, has not been well studied. As an annelid worm, O. labronica likely specifies its germ cells inductively, and therefore has potential to serve as a model species for studies of inductive germ cell specification. Realizing this potential, however, will require the development of genetic resources for this species. I describe the beginnings of such work here: the isolation and characterization of a vasa/PL10-like gene whose expression is largely restricted to germ cells, the construction of a cDNA library, and the refinement of methods for in situ hybridization and immunostaining to visualize gene expression in whole worms.

Estudos taxonômicos foram conduzidos em onufídeos coletados na Baía do Araçá, em São Sebastião, litoral norte do estado de São Paulo, utilizando dados morfológicos e moleculares, e se confirmou que os espécimes coletados pertencem à espécie Diopatra neapolitana, originalmente descrita para o Golfo de Nápoles (Mar Mediterrâneo). Com a identidade específica dos animais confirmada, foi conduzido um estudo anual, com coletas mensais visando entender o ciclo reprodutivo a partir dos gametas femininos presentes no celoma, concluindo que, os indivíduos brasileiros possuem reprodução assíncrona, com o ciclo reprodutivo regido mais pelo tamanho de cada animal, do que pelos meses do ano. O estudo anual focou também na espermatogênese destes animais, que é caracterizada pela presença do citóforo, comum a outras espécies de poliquetas. Observou-se, entretanto, que a espermiogênese possui dois caminhos possíveis: formação de mórulas espermáticas e maturação do espermatozoide na própria estrutura unida pelo citóforo. Foi estudado o hermafroditismo sequencial desta espécie, caracterizado pelas papilas espermoducais, que para os indivíduos da Baía do Araçá, apresentam diferentes estágios de maturação, podendo representar as passagens de um gênero sexual para outro. Por fim foi estudado o desenvolvimento larval e dispersão de gametas, a partir de fertilizações in vitro, com registro de todos os estágios larvais para a espécie estudada, além da construção de protocolos importantes para a biologia do desenvolvimento / Taxonomic studies were conducted with onuphids collected at Araçá Bay, located in São Sebastião, in the northern coast of the state of São Paulo, using morphological and molecular data, and it is confirmed that these specimens belong to the species Diopatra neapolitana, which type locality is the Gulf of Napoli. After confirming the species identity, an annual study was conducted, with mensal collects of specimens, aiming to understand the reproductive cycle, based on feminine gametes present on each celom, and the conclusion is that for the Brazilian specimen, the reproduction is asynchronous, with the reproductive cycle guided rather by the size of each animal, than by the months. The annual study also focused on the spermatogenesis, which is characterized by the presence of the cytophore, common on other polychaete species, however, the spermiogenesis can be accomplished by two paths: formation of spermatic morulae or maturation of spermatozoa linked in the cytophore structure. The sequential hermaphroditism, characterized by the presence of spermoducal papillae, was also studied, and, for the specimen of the Araçá Bay, there are different maturation stages for this feature, probably related to the transition from one gender to another. Lastly, the larval development and gametes dispersion were studied, using in vitro> fertilizations, registering all larval stages for the present species, as well as the origination of development biology protocols

This dissertation addresses large-scale trends in composition, density, taxonomic and functional diversity in deep-sea benthic polychaete communities in the Gulf of Mexico (GoM). The study includes samples from two major sampling programs: the Deep Gulf of Mexico Benthos (DGoMB) program (2000–2002) (51 stations, 200-3700 m) and the SIGSBEE program (Universidad Nacional Autónoma de México), 2008-2010 (27 stations on the Sigsbee Abyssal Plain). Polychaete density decreased exponentially with depth. Alpha diversity did not show a mid-depth maximum and reached its peak near the Mississippi trough. Feeding guild diversity was also highest in the Mississippi trough. The environmental parameters that determine diversity and density of polychaete assemblages and species distribution ranges were examined. Depth, export flux of particulate organic carbon (POC), percent sand and silt were the best predictors of heterogeneity of polychaetes in the GoM. We performed an ecological niche modeling analysis (ENM) based on ‘presence-only’ data of four cosmopolitan species belonging to the Cirratulidae and Spionidae in the GoM. The GoM, being a semi-enclosed ocean basin, offers complex topographic features and hydrographic processes. Comparisons of the overall polychaete diversity and richness patterns from this study for this region indicate a strong geographic variation with increasing depth and distance from the shore. Additionally, the environmental gradients observed play a major role in shaping the spatial distribution of polychaete communities in this region.

Oyster reefs are important estuarine ecosystems that provide habitat to many species including threatened and endangered wading birds and commercially important fishes and crabs. Infaunal organisms (i.e. small, aquatic animals that burrow in the sediment) are also supported by oyster reef habitats. Infaunal organisms are critical to marine food webs and are consumed by many important species that inhabit coastal estuaries. However, over the past century 85% of shellfish reef habitats have been lost, making restoration of these areas vital. Due to their important role in coastal food webs, infauna is hypothesized to be a strong indicator of habitat productivity to document the transition from a dead to a restored and living intertidal oyster reef. Research was conducted in Mosquito Lagoon of the northern Indian River Lagoon system. Three replicate samples were collected from 12 intertidal oyster reefs (four dead, four live, four restored). Samples were collected one-week pre-restoration and one month and six months post-restoration. Infauna was counted and sorted into six taxonomic categories: polychaetes, amphipods, isopods, gastropods, bivalves, and decapods. Reef infaunal abundance increased following restoration: restored reefs became more similar to live reefs one month following restoration. Six months after restoration restored reefs were also significantly different than dead reefs. Live reefs consistently had high infaunal abundance and dead reefs consistently had low abundance, while restored reefs were intermediate. These data suggest restored reefs are more productive than their dead counterparts, with restoration showing a positive trajectory to impact numerous infaunal species and their associated food webs.

<p> Populations of three tubicolous polychaetes, Clymenella torquata, Spiophanes wisleyi and Sabellaria vulgaris located in the intertidal zone of the south shore of Cobequid Bay, Nova Scotia were studied for their effects on the surrounding sediment. Grain size measurements were made of the tubes and the surrounding sediment. T-tests were made on the resultant differences between the Inman sorting and mean statistics of the two sand populat ions . The percentages of heavy and light minerals were also measured with the use of a binocular microscope. The differences in sorting and mean grain size between the tubes and substrate may affect stability and porosity of the sediment and effect sediment structures easily identifiable in the geologic record. </p> <p> Clyrnenella torquata inhabits a low energy intertidal sandy envir onment and increases the porosity of the sediment by its feeding habits. Stabilization of the sediment may be effected by high population densities of Clymenella (densities around 420/m^2). Tubes were built with preferential grain sizes. Spiophanes wisleyi exists in phenomenally high population densities in low-energy areas. The large numbers of tubes (up to 98,000/m^2) bind the sediment; tubes are made of virtually the same grain sizes as the substrate; no bioturbation occurs during the construction of the tubes. The latter two factors make preservation potential very low in the geologic record. Sabellaria vulgaris in the study area is of little sedimentological importance. Population densities are too low to affect the surrounding substrate. This species exists in a high energy zone a characteristic of fauna which build reefs. Reef formation by sabellariids may have been important in the geologic past and is locally important today in the North Sea (Schafer, 1972) and Florida (Gram, 1968). </p> / Thesis / Bachelor of Science (BSc)

Sphaerodoridae is a group of benthic marine worms (Annelida) characterized by the presence of spherical tubercles covering their whole surface. They are commonly considered as belonging to Phyllodocida although sistergroup relationships are still far from being understood. Primary homology assessments of their morphological features are lacking, hindering the appraisal of evolutionary relationships between taxa. Therefore, our detailed morphological investigation focuses on different Sphaerodoridae as well as on other members of Phyllodocida using an integrative approach combining scanning electron microscopy (SEM) as well as immunohistochemistry with standard neuronal (anti-5-HT) and muscular (phalloidin-rhodamine) markers and subsequent CLSM analysis of whole mounts and sections. Furthermore, we provide histological (HES) and light microscopical data to shed light on the structures and hypothetical function of sphaerodorid key morphological features. We provide fundamental details into the sphaerodorid morphology supporting a Phyllodocida ancestry of these enigmatic worms. However, the muscular arrangement and the presence of an axial muscular pharynx is similar to conditions observed in other members of the Errantia too. Furthermore, nervous system and muscle staining as well as SEM and histological observations of different types of tubercles indicate a homology of the so called microtubercles, present in the long-bodied sphaerodorids, to the dorsal cirri of other Errantia. The macrotubercles seem to represent a sphaerodorid autapomorphy based on our investigations. Therefore, our results allow comparisons concerning morphological patterns between Sphaerodoridae and other Phyllodocida and constitute a starting point for further comparative investigations to reveal the evolution of the remarkable Sphaerodoridae.