Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 3 of 3
Full-Text Articles in Entire DC Network
Salinity Effects On The Development And Larval Tolerance Of Five Species Of Echinoderms., Richard Allen Roller
Salinity Effects On The Development And Larval Tolerance Of Five Species Of Echinoderms., Richard Allen Roller
LSU Historical Dissertations and Theses
Salinity effects on the developmental rates, larval tolerances and various metabolic processes of five species of echinoderms were investigated. Development of Lytechinus variegatus (Lamarck), Strongylocentrotus droebachiensis (O. F. Muller, 1776), Strongylocentrotus purpuratus (Stimpson, 1857), Strongylocentrotus pallidus (G. O. Sars, 1871), and Pisaster ochraceus (Brandt, 1835) larvae were observed. Developmental rates and larval survival to metamorphosis of S. droebachiensis and S. pallidus varied directly with salinity and were well within the observed salinity tolerance and distributional limits for the adults. For each species, embryos and larvae at lower salinities (20, 22.5, and $25\sp{o}\!/\!\sb{oo})$ tended to develop more slowly than those at …
Geographic Variation In Morphology And Allozymes Within Tree Squirrels, Sciurus Niger And S. Carolinensis, Of The Lower Mississippi River Valley., Nancy D. Moncrief
Geographic Variation In Morphology And Allozymes Within Tree Squirrels, Sciurus Niger And S. Carolinensis, Of The Lower Mississippi River Valley., Nancy D. Moncrief
LSU Historical Dissertations and Theses
Geographic variation was studied in fox squirrels, Sciurus niger, and gray squirrels, S. carolinensis, by comparing patterns of differentiation within and between these two sympatric species. Patterns of variation were examined in light of the lower Mississippi River as a potential barrier to dispersal and gene flow in these squirrels. Differences within and between species were analyzed using morphologic (15 cranial and mandibular measurements) and allozymic (35 presumptive gene loci) characters. Geographic patterns of variation among populations were apparent in the morphology and allozymes of both species; patterns of differentiation in morphologic and allozymic characters are similar between species; however, …
Effects Of Riverine Barriers On Genetic Differentiation Of Amazonian Forest Undergrowth Birds (Peru)., Angelo Paul Capparella
Effects Of Riverine Barriers On Genetic Differentiation Of Amazonian Forest Undergrowth Birds (Peru)., Angelo Paul Capparella
LSU Historical Dissertations and Theses
The high frequency with which rivers delimit phenotypically differentiated bird taxa is unique to Amazonia, where major rivers often form the boundaries between allospecies and subspecies pairs of understory terra firme forest birds. In contrast, many such forest species with life history traits similar to these differentiated forms show no variation in plumage across even the largest rivers. To determine whether such species are nonetheless genetically differentiated, I obtained tissue samples from populations of forest understory birds from opposite banks of the Napo and Amazon rivers of northeastern Peru. These included three species that are not phenotypically differentiated across the …