STABLE ISOTOPES PROVIDE EVIDENCE FOR POOR NORTHERN PINTAIL PRODUCTION ON THE CANADIAN PRAIRIES

Abstract: Concerns have been raised regarding declines in western North American northern pintail (Anas acuta L.) populations over the past 30 years. Elucidating the natal origins of pintails and identifying production areas of pintails are important steps in determining the cause of the observed declines. Here, we used stable isotope (sulphur, hydrogen, carbon, nitrogen) featherprints to determine the geographic origins of northern pintail ducks shot by hunters in southern Alberta and Saskatchewan, Canada. Based on the best data available for inferring the distribution of breeding pintails, the proportion of hatch-year pintails originating from Prairie regions was smaller than expected. Our results suggest that production of northern pintails on the Canadian Prairies may be significantly lower than predicted by the number of breeding birds and may be related to human-induced reductions in nest success as a result of agricultural practices.     

Fire incidence,but not fire size,affects macropod densities

The regeneration of plants post‐fire has widely been shown to be attractive to vertebrate herbivores. However, there are few data relevant to the effect of fire size on herbivore densities. In dry eucalypt forest in one region and hummock sedgeland in another region, we used timed scat counts to test the effect of fire and fire size on Tasmanian macropod densities 6 months after burning. We also tested whether soil characteristics and the nature of ground cover related to the degree of attractiveness of post‐burn regeneration. Soil nutrients and higher covers of grasses and herbs in ground layer vegetation were associated with higher macropod densities. In dry eucalypt forest, fire incidence and fire size did not affect macropod density, while in hummock sedgeland, fire had a positive effect on macropod density, but fire size had no effect.     

Explanation for Unusual Potency of Salmon Calcitonin

THE calcitonins are polypeptide hormones of thirty-two amino-acids which lower serum calcium in mammals by inhibiting bone resorption¹. During evaluation of these hormones as a means of treating skeletal disorders in man, particularly Paget's disease of bone^{2, 3}, the surprising observation was made that calcitonin from the salmon (SCT) is 20–200 times more potent than porcine calcitonin (PCT) and at least ten times more potent than human calcitonin^{3, 4}. SCT is far more potent than any mammalian calcitonin yet tested in a wide variety of animal species^{5, 6}. This unusual potency of salmon calcitonin could reflect either a greater hormone affinity for receptor sites or a greater resistance to metabolic destruction. We now report evidence which supports the latter possibility, infused SCT disappears from the circulation of the dog much more slowly than does PCT.     

The influence of feeding habits on whole-body metal concentrations in aquatic insects

SUMMARY.

• 1 Concentrations of seven metals in forty taxa of aquatic insects were determined in order to examine the influence of the insects’ feeding habits on their whole-body metal content. Species were grouped into five feeding categories which reflected both the type of material the organisms ingested and their contact with sediments during feeding.
• 2 Species such as the burrowing mayflies (Ephemeridae) and some of the Chironomidae, which indiscriminately ingest sediment along with detritus, had the highest concentrations of most metals. Filter feeders (e.g. Hydropsychidae) had the next highest concentrations, followed by species which to some degree selectively ingest detritus and periphyton (e.g. many Ephemeroptera, Plecoptera and Trichoptera). Carnivores and surface feeding species, such as the Gerridae and Gyrinidae, had the lowest metal concentrations.
• 3 Analysis of metal concentrations of both gut contents and bodies of individuals from each of these feeding types explain these differences. Gut material was enriched in most metals (Co, Cr, Fe, Sb, Sc) relative to their concentrations in the organism's body and it often constituted a major proportion of an organism's whole-body burden of a metal.
• 4 Both the concentrations of metals in the gut material and the proportion of the whole-body burden of a metal that was associated with gut contents varied with the feeding habit of a species. This was because of differences in the amount of inorganic material ingested by the species in each feeding category, higher concentrations occurring in organisms which ingested relatively greater amounts of sediment.
• 5 Organism concentrations of K and Na were less affected by feeding habits since the majority of the whole-body burden of these metals was associated with an organism's tissue and surface rather than with gut material.

     

Late Ordovician-Early Silurian fluctuations in sea level from eastern Anticosti Island, Quebec

Over 1,000 m of Upper Ordovician to Lower Silurian mixed carbonate and clastic strata on Anticosti Island are nearly tectonically undisturbed, despite their proximity to the Northern Appalachians fronting Quebec's Gulf of St. Lawrence. Natural cliffs exposed along the coast and rivers in the eastern part of the island make a relatively conformable sequence belonging to the Ashgill and Llandovery Series. Fossil communities interpreted as depth-associated in life are especially repetitious in the Becscie, Gun River, Jupiter, and Chicotte Formations (Llandovery Series), and to a lesser degree in the Upper Vaureal and Ellis Bay Formations (Ashgill Series). Preliminary study of the pattern of changeovers in Eocoelia, Pentamerus and Stricklandia communities suggests that Anticosti seas deepened and shallowed three and a half times during the Early Silurian. High water peaks were reached during B₁-B₂, C₁-C₂ and C₄-C₅ times, with a final deepening trend beginning in late C₅ time. Age determinations of these events are based on the occurrence of graptolites (with some new records from Anticosti) keyed to the standard graptolite zones, and species of the Eocoelia lineage are also useful for correlation. The profile of the Anticosti sea-level curve compares well with other curves reconstructed from the Lower Silurian of New York, Michigan, and Iowa. Widespread synchronism in sea-level changes on the North American platform is thus corroborated.     

Glycosidases from Cotyledons of Pisum sativum L.

-Mannosidase and ß-N-acetylglucosaminidase were purifiedfrom extracts of cotyledons of germinating Pisum sativum L.A 13-fold purification of a-mannosidase free from ß-N-acetylglucosaminidaseactivity was achieved by precipitation in ammonium sulphate,column chromatography on DEAE-cellulose, and treatment with2 M pyridine. ß-N-Acetylglucosaminidase was purified200-fold by the use of (NH₄)₂SO₄, and chromatography on ConcanavalinA¹-Sepharose and Sephacryl-200. This preparation showed no measurablecontamination by -mannosidase activity. Both glycosidases appearto be glycoproteins and demonstrate optimal activity at pH valuesof 4.0–4.5. Both glycosidases appear to have very similarmolecular weights, with -mannosidase being slightly larger thanß-N-acetylglucosaminidase. An extensive search forthe activity of aspartylglycosylamine amido hydrolase in peacotyledons proved unsuccessful.     

Macroinvertebrate distribution and production on the floodplains of two lowland headwater streams

SUMMARY.

• 1 Spatial and temporal distribution, abundance and production of the floodplain macroinvertebrate communities of two low-gradient headwater streams in Virginia, U.S.A., were studied over 1 year.
• 2 Spatial and temporal distribution patterns of invertebrates were affected by inundation patterns. Numbers, biomass and production were higher in low than high floodplain areas and on a floodplain continuously inundated over 9 months compared with a floodplain completely flooded only occasionally during storms.
• 3 The predominant species in terms of numbers and production on both floodplains was the harpacticoid copepod Attheyella illinoisensis Forbes. Other species with relatively high production were the sphaeriid clam Pisidium sp., the leptophlebiid mayfly Leptophlebia sp., the isopod Caecidotea racovitzai (Williams), and the chironomids Paratendipes sp. and Polypedilum spp.
• 4 Annual invertebrate production (dry weight) on the floodplain continuously inundated over 9 months was 6.1 g m^?2; production on the periodically inundated floodplain was 1.7 g m^?2. Collector-gatherers accounted for 58–61%, and predators 19–25%, of the production.
• 5 Annual invertebrate production on the floodplains, calculated on the basis of a linear metre of channel length, was 84–490 gm^?1, or about one to two orders of magnitude greater than probable production in the channels, suggesting the significance of floodplain invertebrates to stream system trophic dynamics.

     

Population-genetic evidence for two species in Anopheles minimus in Thailand

ABSTRACT. Sympatric occurrence of homozygotes for two electro-morphs controlled by a locus for octanol dehydrogenase, and the absence of heterozygotes, at two localities, indicates two isomorphic species within the taxon Anopheles minimus Theobald in Thailand. This view is supported by significant, relative deficiences of heterozygotes at other electromorphic loci. Gene frequency data are reported for seven electro-morphic loci in An.minimus sensu lato from eleven localities: one of the newly recognized species predominated in all but one locality and the second was confined to two localities. This species pair of An.minimus s.l. was clearly distinguished from An.aconitus Donitz, An.pampanai Biittiker & Beales and An.varuna Iyengar, three species closely related to An.minimus s.l. in the series Myzomyia of Anopheles subgenus Cellia.     

Food provisioning lowers inter-clutch interval in Moorhens Gallinula chloropus

Food supplements were provided to Moorhens Gallinula chloropus during production of their first brood, to test whether food availability limited the number of broods they could rear in a season. Supplemented territories had shorter inter-clutch intervals when individual differences were held constant, although they did not produce more broods. Because unmanipulated birds with short inter-clutch intervals produced more broods, food availability may be one of several factors limiting the production of multiple broods and therefore reproductive success.