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The UDSpace Institutional Repository collects and disseminates research material from the University of Delaware.
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Recent Submissions
The Like Of This Bell
(2011) Brandon Boan
The Like Of This Bell
(2011) Brandon Boan
Morphology, composition, and deterioration of the embryonic rostral sheath of the smalltooth sawfish (Pristis pectinata)
(Fishery Bulletin, 2024-05-28) Poulakis, Gregg R.; Wyffels, Jennifer T.; Fortman, P. Eric; Wooley, Andrew K.; Heath, Lukas B.; Yakich, Dylan M.; Wilson, Patrick W.
Elongated rostra evolved in diverse animal groups as adaptations for feeding, defense, sensory perception, and reproduction. Sawfish rostra have tooth-like dermal denticles, referred to as rostral teeth, along their lateral margins. Embryos have a sheath, or covering, for the calcified rostral teeth during gestation, and it persists until after parturition. Little is known about the morphology and composition of the sheath. During 18 years of tagging juvenile smalltooth sawfish (Pristis pectinata), sheaths were documented for 36 neonates with stretch total lengths of 581–812 mm, and samples were collected from 6 specimens for laboratory evaluation. The multilayered, skin-like sheath, which cannot be easily removed manually, has a vascularized inner layer of connective tissue composed primarily of fibrous proteins (e.g., collagen, reticulin, and keratin) surrounded by an outer layer of columnar and spherical epithelial cells overlying a basement membrane. The columnar cells contain condensed chromatin and differentiate into the outermost spherical cells that contain carbohydrates. After birth, the sheath is shed evenly over 4 d, through sloughing and apoptosis, fully exposing the rostral teeth. The sheath is an ephemeral embryonic organ that protects the female and the embryos from injury during gestation and birth.
Resumen
Los rostros alargados evolucionaron en diversos grupos de animales como adaptaciones para la alimentación, la defensa, la percepción sensorial y la reproducción. Los rostros de los peces sierra tienen a lo largo de sus márgenes laterales, dentículos dérmicos, denominados dientes rostrales. Los embriones tienen una cubierta o envoltura para los dientes rostrales calcificados durante la gestación, que persiste hasta después del parto. Se sabe poco sobre la morfología y composición de la cubierta. Durante 18 años de marcado de juveniles de pez sierra peine (Pristis pectinata), se documentaron las cubiertas de 36 neonatos con longitudes totales estiradas de 581-812 mm, y se recogieron muestras de 6 especímenes para su evaluación en laboratorio. La cubierta multicapa, similar a la piel, la cual no puede extraerse manualmente con facilidad, tiene una capa interna vascularizada de tejido conectivo compuesta principalmente de proteínas fibrosas (ej. colágeno, reticulina y queratina) rodeada por una capa externa de células epiteliales columnares y esféricas que recubren una membrana basal. Las células columnares contienen cromatina condensada y se diferencian en las células esféricas más externas que contienen carbohidratos. Tras el nacimiento, la cubierta se desprende uniformemente a lo largo de 4 días, mediante descamación y apoptosis, exponiendo completamente los dientes rostrales. La cubierta es un órgano embrionario efímero que protege a la hembra y los embriones de lesiones durante la gestación y el nacimiento.
Distribution and composition of redox-active species and dissolved organic carbon in Arctic lacustrine porewaters
(Arctic, Antarctic, and Alpine Research, 2024-07-22) Xin, Danhui; Hudson, Jeffrey M.; Sigman-Lowerya, Anthony; Chin, Yu-Ping
The interaction between redox-active species and dissolved organic carbon (DOC) is crucial in driving lacustrine benthic microbial processes. In lacustrine porewaters, many redox-active species exist in their reduced form, while DOC acts as a substrate and an electron acceptor. Understanding the types and abundance of redox-active species in porewaters along with their complementary DOC substrate is pivotal for gaining insights into benthic processes, particularly in regions susceptible to climate change. We report the in-situ measurement of redox-active species in sediment porewaters, alongside the ex-situ measurement of DOC extracted from cores collected from two Arctic lakes (Toolik and Fog 1). Fe2+ was abundantly detected below 4 cm of the sediment-water interface in all cores and was inversely related to dissolved O2. Additionally, two distinct Fe(III)-complexes were identified. DOC ranged in the order of 10s of mg/L and either remained stable or increased with depth. A comparison between Toolik and Fog 1 lakes revealed a higher accumulation of Fe2+ and DOC in the latter. This study marks the first of its kind to assess spatial distributions of redox-active species and DOC as a function of depth from multiple sites in Arctic lacustrine porewaters.
Homelessness In Delaware: An Assessment
(Delaware Journal of Public Health, 2023-06-12) Metraux, Stephen; Peuquet, Steven W.
The authors provide an assessment of trends and dynamics of homelessness in Delaware since 2007, when the last systematic study of this topic was released. Using population data on homelessness in the state, the authors present evidence that, after a period of apparent stability, homelessness in Delaware is currently at levels that are unprecedentedly high, while providers of homeless services have not adapted to this change. As a first step to addressing this alarming trend, the authors call for stakeholders to regroup and develop a coordinated, statewide approach to address this problem.