Studies on the prevalence of haematozoa of British bats

Bloodfilms were collected from 491 bats representing 12 of the 15 species of British bats, from a number of sites in England and Scotland, and examined for haematozoa. Trypanosoma (Schizotrypanum ) sp. were found in Pipistrelluspipistrellus, Nyctalus noctula, N. leisleri, Eptesicus serotinus and Myotis brandtii , and Trypanosoma (Megatrypanum) incertum was found in P. pipistrellus. Both subgenera of trypanosomes appear to be transmitted by the bat bug Cimex pipistrelli. Gametocytes of the haemoproteid Poly-chromophilus murinus were found in one-third of Myotis daubentonii examined, and stages of the parasite were found in the vector, the wingless blood-sucking fly, Nycteribia kolenatii , collected from these bats. The piroplasm Babesia vesperuginis was found in the blood of P. pipistrellus and Myotis mystacinus , and was the only parasite to show evidence of pathogenicity to bats.     

Changing Sink Demand Affects the Area but not the Specific Activity of Assimilate Sources in Cantaloupe (Cucumis meloL.)

To better understand source-sink interactions, this work focusedon the influence of fruit number on leaf area and photosyntheticactivity in cantaloupe. To this end, flowers were removed over2 years on two Charentais cultivars to obtain single-fruit plantsand plants with an unrestricted fruit load (which set two tofive fruits and constituted control plants). At the whole plantscale, net photosynthesis was reduced by about 30% under highfruit load. At the leaf scale, a submodel of stomatal conductancewas fitted to the data and was included in a rectangular hyperbolamodel of leaf photosynthesis. Maximum leaf net photosynthesisaveraged 14.83 µmol CO₂m^-2s^-1at 1000 µmol quantam^-2s^-1. Light use efficiency was not affected by fruit loadand equalled 0.040 mol CO₂mol^-1quanta. Leaf area of plants withunrestricted fruit load decreased after 24 days from pollination,while the leaf area of single-fruit plants was still increasing.The decrease was due to production of fewer new leaves per day,whereas the number of senescent leaves and the size of individualleaves were not affected by the treatment. Under high fruitload, cultivar Galoubet developed a larger projected leaf areathan cultivar Talma. Thus it is concluded that: (1) large cantaloupefruits may divert a large amount of assimilates away from, andgrow at the expense of, the canopy; and (2) photosynthesis ofthe canopy was lowered because leaf area was reduced whereasphotosynthetic rate of leaves was not altered.Copyright 1998Annals of Botany Company. Cucumis meloL., fruit load, source-sink interactions, leaf photosynthesis, canopy photosynthesis, leaf area, SLA, source strength.     

Tip Transformation in Tetrahymena: A Morphogenetic Response to Interactions Between Mating Types*

SYNOPSIS. In Tetrahymena thermophila subline B, a morphogenic alteration of the anterior end of cells of mating types III and VII results from a cellular interaction which precedes and is a prerequisite for pairing. Cell pairing begins 1 h after starved cells of complementary mating type are mixed. The 1 h-long lag period is characterized by an actinomycin D-sensitive inductive interaction in the first 30 min, followed by a maturation period. Tip transformation begins during the maturation period and continues after pairing. Scanning electron microscopy of deciliated cells reveals ridges which form a chevron meeting in a midline seam between the oral apparatus and the anterior tip. During transformation, the seam broadens until the ridged surface is completely smooth. Melding of the ridges also occurs at the tip of the cell resulting in its blunted appearance. Cells of complementary mating types join in the region of this modified surface, which eventually becomes a specialized cell junction perforated by cytoplasmic bridges. Thus, pursuant to an inductive interaction the structure of the tip of cells is modified in anticipation of the pairing event. Rate of cell pairing might be limited by rate of tip transformation.     

Response of secondary production by macroinvertebrates to large wood addition in three Michigan streams

1. We measured responses in macroinvertebrate secondary production after large wood additions to three forested headwater streams in the Upper Peninsula of Michigan. These streams had fine‐grained sediments and low retention capacity due to low amounts of in‐channel wood from a legacy of past logging. We predicted that wood addition would increase macroinvertebrate secondary production by increasing exposed coarse substrate and retention of organic matter. 2. Large wood (25 logs) was added haphazardly to a 100‐m reach in each stream, and a 100‐m upstream reach served as control; each reach was sampled monthly, 1 year before and 2 years after wood addition (i.e. BACI design). Macroinvertebrate secondary production was measured 1 year after wood addition in two habitat types: inorganic sediments of the main channel and debris accumulations of leaf litter and small wood. 3. Overall macroinvertebrate production did not change significantly because each stream responded differently to wood addition. Production increased by 22% in the main‐channel of one stream, and showed insignificant changes in the other two streams compared to values before wood addition. Changes in main‐channel macroinvertebrate production were related to small changes in substrate composition, which probably affected habitat and periphyton abundance. Macroinvertebrate production was much greater in debris accumulations than in the main‐channel, indicating the potential for increased retention of leaf litter to increase overall macroinvertebrate production, especially in autumn. 4. Surrounding land use, substrate composition, temperature and method of log placement are variables that interact to influence the response of stream biota to wood additions. In most studies, wood additions occur in altered catchments, are rarely monitored, and secondary production is not a common metric. Our results suggest that the time required for measurable changes in geomorphology, organic matter retention, or invertebrate production is likely to take years to achieve, so monitoring should span more than 5 years, and ecosystem metrics, such as macroinvertebrate secondary production, should be incorporated into restoration monitoring programs.     

Estimating Black Bear Density Using DNA Data From Hair Snares

ABSTRACT DNA-based mark-recapture has become a methodological cornerstone of research focused on bear species. The objective of such studies is often to estimate population size; however, doing so is frequently complicated by movement of individual bears. Movement affects the probability of detection and the assumption of closure of the population required in most models. To mitigate the bias caused by movement of individuals, population size and density estimates are often adjusted using ad hoc methods, including buffering the minimum polygon of the trapping array. We used a hierarchical, spatial capture-recapture model that contains explicit components for the spatial-point process that governs the distribution of individuals and their exposure to (via movement), and detection by, traps. We modeled detection probability as a function of each individual's distance to the trap and an indicator variable for previous capture to account for possible behavioral responses. We applied our model to a 2006 hair-snare study of a black bear (Ursus americanus) population in northern New York, USA. Based on the microsatellite marker analysis of collected hair samples, 47 individuals were identified. We estimated mean density at 0.20 bears/km². A positive estimate of the indicator variable suggests that bears are attracted to baited sites; therefore, including a trap-dependence covariate is important when using bait to attract individuals. Bayesian analysis of the model was implemented in WinBUGS, and we provide the model specification. The model can be applied to any spatially organized trapping array (hair snares, camera traps, mist nests, etc.) to estimate density and can also account for heterogeneity and covariate information at the trap or individual level.     

Hierarchical multi-scale occupancy estimation for monitoring wildlife populations

Occupancy estimation is an effective analytic framework, but requires repeated surveys of a sample unit to estimate the probability of detection. Detection rates can be estimated from spatially replicated rather than temporally replicated surveys, but this may violate the closure assumption and result in biased estimates of occupancy. We present a new application of a multi-scale occupancy model that permits the simultaneous use of presence–absence data collected at 2 spatial scales and uses a removal design to estimate the probability of detection. Occupancy at the small scale corresponds to local territory occupancy, whereas occupancy at the large scale corresponds to regional occupancy of the sample units. Small-scale occupancy also corresponds to a spatial availability or coverage parameter where a species may be unavailable for sampling at a fraction of the survey stations. We applied the multi-scale occupancy model to a hierarchical sample design for 2 bird species in the Black Hills National Forest: brown creeper (Certhia americana) and lark sparrow (Chondestes grammacus). Our application of the multi-scale occupancy model is particularly well suited for hierarchical sample designs, such as spatially replicated survey stations within sample units that are typical of avian monitoring programs. The model appropriately accounts for the non-independence of the spatially replicated survey stations, addresses the closure assumption for the spatially replicated survey stations, and is useful for decomposing the observation process into detection and availability parameters. This analytic approach is likely to be useful for monitoring at local and regional scales, modeling multi-scale habitat relationships, and estimating population state variables for rare species of conservation concern. © 2011 The Wildlife Society.     

THE PHYSIOLOGICAL ECOLOGY OF REPTILIAN EGGS AND EMBRYOS. AND THE EVOLUTION OF VIVIPARITY WITHIN THE CLASS REPTILIA

1. Eggs of Crocodilia and Chelonia, like those of birds, have a pair of egg membranes separating a thick layer of albumen from the calcareous shell. In contrast, eggs of oviparous Lepidosauria have only a single shell membrane, upon which relatively small amounts of calcium carbonate are deposited; and the volume of albumen in eggs is extraordinarily small at the time of oviposition. 2. With the possible exception of certain geckos and some chelonians, eggs of oviparous reptiles seem always to absorb water from the substrate during the course of normal incubation. In so far as the rate of water absorption exceeds the rate of water loss by transpiration from exposed surfaces, the eggs swell during incubation. The term ‘cleidoic’ cannot be used to describe eggs of this type. 3. Embryos of lizards and snakes influence the water potential of extra-embryonic fluids contained within their eggs, thereby maintaining or increasing the gradient in water potential that drives water absorption. 4. Embryos of Crocodilia and Chelonia obtain a substantial portion of the calcium used in ossification of skeletal elements from the inner surfaces of the eggshell. In contrast, embryonic lizards and snakes draw upon extensive reserves of calcium present in the yolk, and obtain little (if any) calcium from the eggshell. 5. All reptilian embryos seem to produce substantial quantities of urea as a detoxification product of protein catabolism. Contrary to expectation, uricotelism may not be common among reptilian embryos, even in those few instances where development takes place within a hard, calcareous egg. 6. In eggs of Crocodilia and Chelonia, respiratory gases seem to pass by diffusion through pores in the calcareous eggshell and through spaces between the fibres of the pair of egg membranes. No pores have been observed in the shell of lepidosaurian eggs, and so gases presumably diffuse between the fibres of the single (multilayered) shell membrane. 7. Metabolism of reptilian embryos is temperature-dependent, as is true for most ectothermic organisms. For each species, there appears to be a particular temperature at which embryonic development proceeds optimally, and departures from this optimum elicit increases in developmental anomalies and/or embryonic mortality. 8. Viviparity has evolved on numerous occasions among species of the Squamata, but seemingly never among Crocodilia or Chelonia. Since the evolution of viviparity entails a progressive reduction in the eggshell, only those organisms whose embryos do not depend upon the eggshell as a source of calcium may have the evolutionary potential to become viviparous. 9. Evolutionary transitions from oviparity to viviparity could have been driven by selection related to (i) thermal benefits to embryos consequent upon retention of eggs within the body of a parent capable of behavioural thermoregulation; (ii) protection of the eggs from nest predators and/or soil microbes; and (iii) more effective exploitation of a seasonal food resource by early emerging young.     

Patch selection by mottled sculpin (Pisces: Cottidae) in a southern Appalachian stream

1. We examined the effects of prey abundance on patch selection by a benthic fish, the mottled sculpin ( Cottus bairdi ), in a fourth order, southern Appalachian stream (North Carolina, U.S.A.). This habitat is a mosaic of small (i.e. < 0.5 m²), relatively discrete patches.
2. Patches were characterized in terms of physical habitat variables, detritus (coarse particulate organic matter, CPOM) and macroinvertebrate abundance (number and biomass). We quantified patch selection by comparing the characteristics of patches utilized by sculpin with those of locally available patches. Locally available patches were selected using a constrained random sampling design (i.e. randomly selected within a 2 m radius from each fish). We also examined the relationship between macroinvertebrate abundance, CPOM and the physical characteristics of available patches.
3. Patches selected by sculpin contained significantly higher macroinvertebrate abundances (both number and biomass) than locally available patches in five out of six seasonal samples. Sculpin also occupied patches with significantly higher amounts of CPOM in three out of five seasonal samples. Patches utilized by sculpin, however, could not be consistently differentiated from locally available patches on the basis of physical variables. In addition, macroinvertebrate abundance was not consistently related to physical habitat variables or CPOM during the course of the study.
4. Our results suggest that sculpin are able to assess patch quality on the basis of prey abundance and select patches that potentially maximize energy gain. This behaviour may produce an increase in individual fitness, especially when prey distributions are not consistently related to habitat variables. Quantifying patch use in relation to prey abundance may help elucidate the causal factors determining habitat use by benthic fishes in other lotic systems.