Pigeon navigation: Charcoal filter removes relevant information from environmental air

Summary Homing pigeons were displaced and kept until they were released in airtight containers ventilated with environmental air that could be passed through: (a) a filter made of fiberglass paper retaining large portions of the solid and liquid aerosol particles, (b) an additional filter consisting of activated charcoal, or (c) no filter (controls). Before its release, each bird was taken out of the container, and its olfactory epithelium was immediately anesthetized by lidocaine (Xylocaine). Thus, neither experimentals nor controls were able to smell while their initial orientation behavior was being observed.The controls' initial bearings were better homeward-oriented than those of pigeons ventilated with charcoal-filtered air in 14 of 17 releases conducted in Italy and Germany, at distances of 24–155 km. In the final analysis, the bearings of the charcoal-filter birds did not show any relation to the direction toward home, whereas those of the controls did. Pigeons ventilated with air that had passed through only the paper filter did not behave noticeably differently from control pigeons.It is concluded that the material bases of olfactory navigation in pigeons are substances dispersed in the atmosphere, most probably in a molecular state.     

Efficient size-selective bacterivory by phagotrophic nanoflagellates in aquatic ecosystems

Size-selective grazing on bacterioplankton by phagotrophic nanoflagellates was analyzed and modelled. The proposed model resembles a Monod equation (Michaelis-Menten-like expression) in which clearance rates by heterotrophic nanoflagellates depend on bacterioplnnkton biovolume. Larger bacteria were ingested faster than smaller bacteria. The proposed model was in agreement with experimental data from different authors, both from cultures and natural assemblages. Size-selective grazing efficiency was analyzed as the ability of phagotrophic nanoflagellates to discriminate between cells differing in volume by a factor of two, e.g., corresponding to dividing and nondividing bacteria. Unlike previously published models, the proposed model suggests that phagotrophic nanoflagellates could be highly effective size-selective grazers for small bacteria (<0.1 m³), which are the most common bacterial sizes in planktonic systems. However, phagotrophic nanoflagellates were unable to size-discriminate dividing and nondividing bacteria for volumes >0.1 m³. These results strongly support the hypothesis that heterotrophic nanoflagellate grazing, by discriminating between different sizes of dividing and nondividing bacteria, may actually be regulating bacterial size and growth rate in natural aquatic ecosystems.     

Application of ‘Landsat’ data to resource management

Over the past few years, a great deal of interest has been focused on the use of remote sensing for resource management. This paper examines one of the most useful systems — Landsat. Included in this paper is a discussion of this remote-sensing technology, its application and its future as a tool for resources planning and management.     

A field test of the intraspecific brood parasitism hypothesis in the golden egg bug (<Emphasis Type="Italic"> Phyllomorpha laciniata</Emphasis>)

In natural populations of golden egg bugs ( Phyllomorpha laciniata), females lay eggs on plants where they develop unattended, or on conspecifics, where they remain firmly glued until the nymphs hatch and start an independent life. Mortality rates among eggs laid on plants are higher than among eggs carried by adults. Because females cannot lay eggs on themselves, in order to improve offspring survival, they have to lay eggs on other individuals. Two hypotheses have been proposed to explain egg carrying: (1) the mating pair intraspecific brood parasitism hypothesis suggests that females dump eggs on copulating pairs, and (2) the paternal care hypothesis suggests that the system is driven mainly by males accepting eggs to improve the survival rates of their own offspring. Our data from the field show that 77% of the eggs are carried by males, because more males than females carry eggs, and because males carry a greater number of eggs. In addition, we show that mating males carry more recently laid eggs than single males. These results support the view that egg carrying is performed predominantly by males and that eggs are laid on males by their current mating partner, probably between repeated copulations. Males are likely to accept eggs, despite intermediate levels of paternity, because they cannot discriminate in favour of their own eggs, because rejected eggs will face 97% mortality rates on plants, and because they do not suffer mating costs when they carry eggs. However, females carry 23% of the eggs, but no differences in egg carrying have been found between mating and single females, suggesting that this is not the result of egg dumping while females are copulating. Egg carrying by females could reflect low levels of intraspecific parasitism, which is likely to reflect the low rate of successful attempts by egg-laying females who try to oviposit on other conspecifics rather indiscriminately, in an effort to improve the survival of their offspring.     

Morphologic development, relative sea level rise and sustainable management of water and sediment in the Ebre Delta, Spain

The Ebre (Ebro) Delta is one of the most important wetland areas in the western Mediterranean. Ca. 40 % of the delta plain is less than 0.5 m above mean sea level and part of the southern margin of the delta is at mean sea level in an area protected by dikes. Both mean rates of secular subsidence in the Ebre Delta and eustatic sea level rise are ca. 1 – 2 mm/yr. Thus, the present annual relative sea level rise (RSLR) rate in the Ebre Delta may be at least 3 mm/yr. Measured accretion rates in the delta range from 4 mm/yr in the wetlands surrounding the river mouth to <0.1 mm/yr in impounded salt marshes and rice fields. The annual sediment deficit in the delta plain to offset RSLR is close to 1 million m³/yr. Accretion rates in the rice fields prior to the construction of large dams in the Ebre watershed were higher than RSLR rates, from 3 – 15 mm/yr. At present, >99 % of the riverine sediments are retained in the reservoirs and rice fields are losing ca. 0.2 mm/yr. Future management plans should take RSLR into account and include control of freshwater and sediment flows from the river in order to offset negative effects from waterlogging and salt intrusion, and maintain land elevation. This will include the partial removal of sediments trapped behind the Ribarroja and Mequinença dams. Stocks and inputs of sediments in the corresponding reservoirs are large enough for land elevation of ca. 50 cm in the whole delta plain. Advantages of this solution include (1) new sediments to the delta to offset subsidence (via rice fields) and coastal retreat, (2) enhanced functioning of the delta (productivity and nutrient processing), (3) avoidance of accumulation of sediments in the reservoirs. Hence, it is important to manage river discharges at the dams from an integrated viewpoint, whereas currently only hydropower and agricultural requirements are considered. It is also crucial to maintain periods of high discharge, to have enough river energy to transport as much sediments as possible.     

A morphological approach for relating decapod crustacean cephalothorax shape with distribution in the water column

Cephalothorax profiles for individuals of 18 decapod crustacean species were obtained from pictures of specimens captured using various experimental bottom trawls in the Mediterranean basin, at depths ranging from 200 to 4000 m in 2000 and 2002. Profiles were compared using the shape (outline) of the entire cephalothorax (including and excluding the rostrum). Principal component analysis (PCA) of the profiles, rostrum included, yielded two large species groupings related to rostrum size, species having a long rostrum being clustered on the positive portion of the first axis and species having a short rostrum being clustered on the negative portion of this same axis (the F1 axis explained 72.17% of the total variance). The PCA separated pelagic and endobenthic animals (with short rostrums) from nektobenthic animals (with long rostrums). Only the two deepest-dwelling species (dwelling at depths below 2000 m) were distanced from their respective groups. The pelagic shrimp Acanthephyra pelagica was clearly grouped with the nektobenthic species despite being reported to have a pelagic habitat. The nektobenthic deep-sea species Nematocarcinus exilis has a relatively medium-size rostrum and was placed among the pelagic–endobenthic species. The endobenthic and pelagic groups remained stable even when rostral morphometrics were excluded from the PCA analysis. The hypothesis that predation and diet are the fundamental determining factors for all habitats throughout most of the lifetimes of individuals and hence that species will evolve specialised phenotypes to adapt to local environmental conditions is considered in the discussion.Communicated by O. Kinne, Oldendorf/Luhe     

Effects of copper and cadmium on osmoregulation and oxygen consumption in two species of estuarine crabs

Green crabs (Carcinus maenas) and rock crabs (Cancer irroratus) were exposed to various concentrations of copper as cupric chloride (CuCl₂ · 2 H₂O), and cadmium as cadmium chloride (CdCl₂ · 21/2 H₂O) for 48 h. The exposures were conducted at 5 different salinities. At the end of each exposure period, tests of blood-serum osmolality and gill-tissue oxygen consumption were performed. Copper-exposed crabs exhibited loss of osmoregulatory function with increasing copper concentration until normally hyperosmotic serum became isosmotic with the surrounding medium. Cadmium elevated greencrab serum above its normal hyperosmotic state. Copper had no effect on gill-tissue oxygen consumption; however, cadmium reduced the rate of oxygen consumption in both species tested.     

NADP+-isocitrat-dehydrogenase aus Idus idus (Pisces: Cyprinidae). I. Aktivität als funktion der adaptationstemperatur

Activity of NADP⁺-dependent isocitrate dehydrogenase (ICDH) of the white dorsal muscle of Idus idus L. was determined by special analysis, under optimum homogenisation, centrifugation and cuvette conditions. The experimental conditions differed considerably from those used for the investigation of NADP⁺-ICDH activity in mammals by Bücher et al. (1964). Daily measurements of activity over a period of 10 days revealed variations in enzyme activity which are difficult to explain. However, the variations are smaller than those established in earlier tests. In order to obtain statistically valid results, the highest possible number of test fishes (at least 10 individuals for each measurement) must be investigated over a period of 5 to 10 days. NADP⁺-ICDH of individuals acclimated to 10°C showed 28% higher specific and non-specific activity than that of fish maintained at 20°C (experimental temperature 25°C). At 5 different adaptation temperatures, increasing activities were observed with decreasing adaptation temperature (compensation). These measurements were made over a period of 5 successive days.     

Recommendations for rural abandoned mine program (RAMP) in Iowa,USA

In the last three years, twelve orphan coal surface mines in Iowa, USA, have been reclaimed under the Federal Rural Abandoned Mine Program (RAMP) by smoothing highly acid spoils, covering the spoils with a thin dirt layer and planting a cover crop. Ten years ago a test plot was designed with a wedge of loess over acid spoils. Subsequent observation suggests that on the new RAMP sites, acidified throughflow and discharge of shallow soil moisture and groundwater will gradually kill the vegetation in the lower valleys and erosion will proceed upvalley as a migrating knickpoint. The problem might be eliminated by directing the acidified throughflow beneath the cover material, in sand underdrains or tile lines in the main drainages. The discharge could either be diluted in a nearby creek, if adequate flow is available, or neutralised in a basin paved with limestone rip-rap. Vegetation which was found to be especially well adapted to thin cover sites includes native prairie grasses, crownvetch and cattails. Sphagnum mosses may also offer some possibilities for such locations. A RAMP reclamation site should be designed as an experimental area to test these methods and determine their cost. These recommendations may also be applicable in other mining areas.