Step-point sampling provides a rapid, accurate, and objective method of determining the botanical composition and total cover of herbaceous vegetation. These determinations enable one to evaluate the forage stand on any specific area. The method has been used
The RNA:DNA ratio for first-feeding larvae (12 days after hatching, 4-6 mm standard length, SL) of Australian bass (Percichthyidae, Macquaria novemaculeata) exposed to four different feeding regimes over 8 days was found to be insensitive to the level of starvation. An alternative condition index based on residuals derived from the regression of RNA on SL showed significant differences over the course of the experiment; these reflected the four feeding treatments. Field collections of juvenile monacanthids (Paramonacanthus otisensis, 10-30 mm SL) from a local estuary revealed no significant difference in RNA: DNA ratio at three sites over six weeks. A residual-based index (RNA on dry weight) showed parallel fluctuations at all sites; they were positively correlated with water temperature. The RNA : DNA ratio depends on the difference in fluorescence between total nucleic acids (TNA, using thiazole orange) and DNA (using Hoechst 33258) to calculate RNA, as there is no RNA-specific fluorescent dye. The numerator is thus dependent on the denominator, and measurement error may be compounded in the ratio, exacerbating potential variability in the index. Ratios may also be variably correlated with age or size and consequently may erroneously indicate condition or growth in larger and faster-growing fish.
Late Devensian and early Flandrian, mollusc-, ostracod-and pollen-bearing deposits from Bingley Bog, West Yorkshire are described. The sequence of environmental changes began with a rapid climatic amelioration which allowed the establishment of a diverse molluscan and ostracod fauna. This was followed by a short, less temperate episode that is registered by both the animal and the plant fossils. The Mollusca in particular imply that while a partial climatic recovery was made after this episode, environmental conditions were in overall decline. This decline culminated in a short, severe climatic phase which was probably responsible for the extinction of the fauna, and for a significant change in the flora. Birch woodland was replaced by tundra-like vegetation. The initial climatic amelioration most probably corresponds to the onset of temperate conditions at the start of the Windermere (Aller0d) Interstadial. A subsequent worsening of climate, to cool temperate conditions, is tentatively correlated with the Older Dryas episode. The final cold phase would thus represent the Younger Dryas (Loch Lomond) Stadial. Both plant and animal records indicate the establishment of temperate conditions subsequent to Younger Dryas time. The early Flandrian fauna exhibited a rapid increase in both numbers and diversity, and woodland developed widely during the period.
The reproductive characteristics of six ophiuroid species, Ophiura irrorata loveni, Ophiura lienosa, Amphioplus daleus, Ophiacantha cosmica, Ophiernus quadrispinus and Ophioplexa condita, were studied at two localities in the vicinity of the Crozet Islands in the Southern Indian Ocean. The two localities were notable in having almost identical environmental characteristics other than major differences in surface-water primary productivity and organic matter flux, whilst at the same time being only 460km apart. Three species were sufficiently abundant at the two sites to compare their reproductive biology under different productivity regimes. Ophiura irrorata loveni showed significant differences in oocyte size distributions and population size distributions between the two sites which appeared to be related to the characteristics of organic matter flux at those localities. Ophiacantha cosmica and Ophioplexa condita showed differences in abundance between the two sites. This appeared to be related to the availability of suitable substrata.
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