Morphogenesis of the foetal membranes and placenta of the root-rat (Tachyoryctes splendens (Rüppel))

The morphogenesis of the foetal membranes and placenta of the root-rat Tachyoryctes splendens was studied by light microscopy. Implantation of the blastocyst is antimesometrial. The mode of implantation is secondary interstitial and the decidual reaction is similar to that in other rodents. Amniogenesis is by cavitation with a temporary open epamniotic cavity. Inversion of the yolk sac is complete but the disappearance of the parietal segment occurs relatively late. With the breakdown of both the decidua capsularis and parietalis, the yolk sac wall near the margins of the placenta becomes bathed in a pool of maternal blood and tissue debris resembling the haemophagous organ. The yolk sac villi are well vascularized. The allantoic cavity is persistent up to the limb bud stage. The definitive placenta is haemochorial and shows conspicuous endodermal sinuses or placental pits.     

Effects of spawning Pacific salmon on the isotopic composition of biota differ among southeast Alaska streams

1. Adult Pacific salmon (Oncorhynchus spp.) transport marine nutrients to fresh waters and disturb sediments during spawning. The relative importance of nutrient fertilisation and benthic disturbance by salmon spawners can be modulated by environmental conditions (e.g. biological, chemical and physical conditions in the catchment, including human land use). 2. To determine the importance of the environmental context in modifying the uptake and incorporation of salmon‐derived material into stream biota, we measured the nitrogen (δ¹⁵N) and carbon (δ¹³C) isotopic composition of benthic algae (i.e. epilithon) and juvenile coho salmon (Oncorhynchus kisutch) in seven streams across a timber‐harvest gradient (8–69% catchment area harvested), both before and during the salmon run. Conditional bootstrap modelling simulations were used to assess variability in the response of epilithon and juvenile coho salmon to spawning salmon. 3. In response to spawning salmon, epilithon exhibited enrichment in both δ¹⁵N (mean: 1.5‰) and δ¹³C (2.3‰). Juvenile coho were also enriched in both δ¹⁵N (0.7‰) and δ¹³C (1.4‰). Conditional bootstrap models indicate decreased variation in data as spatial replication increases, suggesting that the number of study sites can influence the results of Pacific salmon isotope studies. 4. Epilithon isotopic enrichment was predicted by environmental conditions, with δ¹⁵N enrichment predicted by stream temperature and timber harvest (R² = 0.87) and δ¹³C enrichment by discharge, sediment size, timber harvest and spawner density (R² = 0.96). Furthermore, we found evidence for a legacy effect of salmon spawners, with pre‐spawner δ¹⁵N and δ¹³C of both epilithon and juvenile coho predicted by salmon run size in the previous year. 5. Our results show that the degree of incorporation of salmon‐derived nitrogen and carbon differs among streams. Furthermore, the environmental context, including putative legacy effects of spawning salmon, can influence background isotopic concentrations and utilisation of salmon‐derived materials in southeast Alaska salmon streams. Future studies should consider the variation in isotopic composition of stream biota when deciding on the number of study sites and samples needed to generate meaningful results.     

Performance of Symydobius americanus (Homoptera: Aphididae) on paper birch grazed by caterpillars

Abstract.

• 1 The potential for host plant-mediated interactions between leaf-chewers and the aphid Symydobius americanus on paper birch (Betula papyrifera) was investigated experimentally.
• 2 Datana ministra and Malacosoma disstria caterpillars were caged on randomly chosen, undamaged branches until they had eaten 30–50% of the leaf area. Control branches received cages but no larvae.
• 3 Alates of S.americanus were than caged on the experimental and control branches to assess the effect of chewing damage on colony performance.
• 4 Chewing damage had no detectable effect on initiation of alate reproduction, development time, mortality of nymphs or colony growth rate.

     

Investing in biodiversity: an economic perspective on global priority setting

Biodiversity investment priorities are a major concern for funding agencies and parties to the Convention on Biodiversity. We present a cost-effectiveness index designed to rank global biodiversity investments addressing weaknesses identified in several existing procedures. First, we explicitly address the issue of cost. Biodiversity conservation can be expensive -- ensuring that money is efficiently spent is important if conserving maximum biodiversity is an objective. Second, a high degree of threat to biodiversity is commonly accepted as constituting the principal reason for intervention and a basis for prioritization. The possibility that a high degree of threat might constitute a reason for non-intervention is rarely considered. The index presented in this study seeks to address these shortcomings by incorporating biodiversity ‘cost’, as measured by investment, and biodiversity ‘benefit’, as measured by a representative biodiversity indicator, species, richness. These elements form the basis of the cost -- benefit ratio needed for cost-effectiveness analysis. Investment in biodiversity is affected by issues of vulnerability (threat) and viability (success). A successful investment intervention will, however, depend on the probability or likelihood of success and the degree of threat prevalent in a particular country. These are integrated into the index as probabilities which will influence the amount of biodiversity ‘saved’ by an intervention. We apply the index using data for the Asia – Pacific region, to provide a cost-effective priority investment index (CEPII) ranking by country. Acute data limitations at the global level particularly in applying complementarity, necessitate caution in the interpretation of the index which, like other methods, requires some subjective choice of success and threat surrogates. The index continues the task of combining scientific and socioeconomic criteria relevant to global priorities. This revised version was published online in November 2006 with corrections to the Cover Date.     

Extensive Predator Space Use Can Limit the Efficacy of a Control Program

ABSTRACT Reduced to small isolated groups by anthropogenic habitat losses or habitat modifications, populations of many endangered species are sensitive to additive sources of mortality, such as predation. Predator control is often one of the first measures considered when predators threaten survival of a population. Unfortunately, predator ecology is often overlooked because relevant data are difficult to obtain. For example, the endangered Gaspésie caribou (Rangifer tarandus caribou) has benefited from 2 periods of predator control that targeted black bears (Ursus americanus) and coyotes (Canis latrans) in an attempt to reduce predation on caribou calves. Despite a high trapping effort, the number of predators removed has remained stable over time. To assess impact of predator movements on efficacy of a control program, we studied space use of 24 black bears and 16 coyotes over 3 years in and around the Gaspésie Conservation Park, Quebec, Canada, using Global Positioning System radiocollars. Annual home ranges of black bears averaged 260 km² and 10 individuals frequented area used by caribou. Annual home ranges of resident coyotes averaged 121 km², whereas dispersing coyotes covered >2,600 km². Coyotes were generally located at lower altitudes than caribou. However, because coyotes undertook long-distance excursions, they overlapped areas used by caribou. Simulations based on observed patterns showed that 314 bears and 102 coyotes potentially shared part of their home range with areas used by female caribou during the calving period. Despite low densities of both predator species, extensive movement and use of nonexclusive territories seem to allow predators to rapidly occupy removal areas, demonstrating the need for recurrent predator removals. Our results underscore the necessity of considering complementary and alternative solutions to predator control to assure long-term protection of endangered species.     

The value of infrared thermography for research on mammals: previous applications and future directions

• 1 Infrared thermography (IRT) involves the precise measurement of infrared radiation which allows surface temperature to be determined according to simple physical laws. This review describes previous applications of IRT in studies of thermal physiology, veterinary diagnosis of disease or injury and population surveys on domestic and wild mammals.
• 2 IRT is a useful technique because it is non‐invasive and measurements can be made at distances of <1 m to examine specific sites of heat loss to >1000 m to count large mammals. Detailed measurements of surface temperature variation can be made where large numbers of temperature sensors would otherwise be required and where conventional solid sensors can give false readings on mammal coats. Studies need to take into account sources of error due to variation in emissivity, evaporative cooling and radiative heating of the coat.
• 3 Recent advances in thermal imaging technology have produced lightweight, portable systems that store digital images with high temperature and spatial resolution. For these reasons, there are many further opportunities for IRT in studies of captive and wild mammals.