Mark-Resight Methodology for Estimating Population Densities for Prairie Dogs

Abstract: Accurate assessments of local population size of the black-tailed prairie dog (Cynomys ludovicianus) are essential because of their overall decline and importance to prairie ecosystems. We describe the use of mark-resight methodology to estimate black-tailed prairie dog population size and density. Study colonies include isolated urban habitat fragments in Denver, Colorado, USA, and unfragmented control colonies in the Pawnee National Grassland, USA. We compare results from various mark-resight estimators to those derived from linear transformations of visual counts of active prairie dogs. Our results suggest that mark-resight methods are feasible in both urban and rural systems, and reveal extremely high densities for isolated prairie dogs in urban sites. Our methodology can be used to obtain reliable, unbiased estimates of local population size and density.     

The role of highly unsaturated fatty acids in aquatic foodweb processes

1. Polyunsaturated fatty acids (PUFA) are almost exclusively synthesized by plants. Animals can convert from one form of PUFA to another through elongation and desaturation, but very few can synthesize PUFA de novo. PUFA play an important role in regulating cell membrane properties, serve as precursors for important animal hormones and are essential for animals. 2. In aquaculture studies, highly unsaturated fatty acids (HUFA), a subset of PUFA, have been found to be critical for maintaining high growth, survival and reproductive rates and high food conversion efficiencies for a wide variety of marine and freshwater organisms. 3. The plankton literature suggests high food-quality algae species are rich in HUFA and low food-quality algae are poor in HUFA. Adding semi-pure emulsions of HUFA to algae monocultures can markedly increase the growth rates of zooplankton feeding on these mixtures. 4. A study measuring zooplankton biomass accrual when feeding on natural phytoplankton found a strong correlation between phytoplankton HUFA (specifically eicosapentaenoic acid) content and herbivorous zooplankton production. 5. The aquatic ecology literature suggests that planktonic foodwebs with high HUFA content phytoplankton have high zooplankton to phytoplankton biomass ratios, while systems with low HUFA phytoplankton have low zooplankton biomass. Also, the seasonal succession of plankton in many temperate lakes follows patterns tied to phytoplankton HUFA content, with intense zooplankton grazing and ‘clear-water-phases’ characteristic of periods when the phytoplankton is dominated by HUFA-rich species. 6. Herbivorous zooplankton production is constrained by the zooplankton’s ability to ingest and digest phytoplankton. It is becoming increasingly clear, however, that much of the phytoplankton which is assimilated may be nutritionally inadequate. HUFA may be key nutritional constituents of zooplankton diets, and may determine energetic efficiency across the plant–animal interface, secondary production and the strength of trophic coupling in aquatic pelagic foodwebs.     

Shoot Auxin and Light in the Mechanism Maintaining the Posture of the Cotyledons of Linum usitatissimum

The mean cotyledon angle (liminal day posture) of flax is linearlyrelated to light intensity, the cotyledons being raised withincreasing intensity; adjustments occur when plants are transferredto new conditions. Short days, low light intensity, and prolongeddarkness result in epinasty. Epinastic and hyponastic responsesare enhanced by excision of the epicotyl shoot. Applicationof indoleacetic acid to the cut shoot is an effective substitutefor the excised portion. Ringing the intact epicotyl with 2,3,5-tri-iodobenzoicacid has an effect comparable to excision. Given continuously or in a light/dark cycle, blue light induceshyponasty, and red light maintains the liminal posture for about48 h after which time epinasty occurs. Far-red light given continuouslyinduces epinasty to an extent comparable to the effect of darkness.Irradiation with far-red light even for brief periods priorto placing the plants in darkness enhances the epinastic response:the effect of far-red light is reversed by a subsequent shortexposure to red light. Interruption of a prolonged period of darkness by blue lightconsiderably lessens the subsequent epinastic reaction whetheror not any epinasty has occurred before the light-break. Redor white light given under these circumstances has less effect.     

Terminology and functional morphology of attachment structures in pelmatozoan echinoderms

Brett, Carlton E. 1981 12 IS: Terminology and functional morphology of attachment structures in pelmatozoan echinoderms. Lethaia . Vol. 14, pp. 343–370. Oslo. 1SSN 0024–1164.
Fixation on the seafloor is a fundamental, though little studied, aspect of the biology and distributional ecology of pelmatozoan echinoderms. Morphology of pelmatozoan attachment structures (holdfasts) and their component appendages is summarized herein and a detailed terminology proposed. Three major modes of fixation are differentiated in living and fossil stemmed echinoderms - primary, composite and secondary attachments - in addition to the direct thecal attachment in stemless forms. Specific holdfast morphologies, which characterize certain major taxa (families and orders) of pelmatozoans, may limit the available life-modes in these echinoderms. Significantly, numerous lineages of echinoderms have independently developed secondary attachment modes associated with the evolution of flexible tapered stem ends and/or true cirri. Cirri are rare in early Paleozoic pelmatozoans but appeared in most major groups by the late Paleozoic. * Pelmatozoa. attachment structures, holdfasts, terminology, functional morphology .