Active habitat selection by pre-settlement reef fishes

Our understanding of habitat selection by reef fish larvae has changed dramatically in the last 10 years. Fish larvae have long been considered passive particles at the mercy of ocean currents, tides and weather events. For reef fishes, ecological evidence has shown that passive dispersal alone often cannot explain larval distributions, suggesting active behaviour by reef fish larvae. While behaviourally modified passive transport may be important, recent work demonstrates that some reef fish larvae have the capability to actively swim to settlement habitat. They can orientate to reefs from distances of at least 1 km and can swim at speeds of 13.5 cm s^?1 for several days. The question then becomes, what are the cues that fish larvae use to orientate to reefs? Ambient reef sound has been shown to be attractive to reef fish larvae, and current research aims to understand better the nature and use of these acoustic cues. Other potential cues include chemoreception/olfaction, wave cues and visual location of reefs. A better understanding of active habitat selection and the underlying sensory and behavioural mechanisms will improve our knowledge of recruitment processes in reef fish ecology, and may have implications for active management of reef fish populations.     

A STORAGE-LIKE DISEASE WITH SKELETAL INVOLVEMENT IN A DOG

A storage-like disease in a 14-month-old Rhodesian Ridgeback dog is described. Clinically the dog was lame on all legs, and appendicular joint capsules were distended. Radiographically and at necropsy, there was evidence of osteoarthritis, increased volume of synovial fluid, and marked hypertrophy of the synovial membranes. Large mononclear cells with vacuolated cytoplasm were evident in synovial membranes. Large mononuclear cells with vacuolated cytoplasm were evident in synovial membranes. Large mononuclear cells with vacuolated cytoplasm were evident in synovial membranes, bone marrow, liver, lymph nodes, and endocrine glands. Vacuolated cells in lymph nodes stained positively for fat. Transmission electron microscopy revealed empty membrane-bound cytoplasmic vacuoles. The similarity of this disease to storage diseases in man where arthropathy is a feature is discussed.     

Tolerance of juvenile black sea bass Centropristis striata to acute ammonia and nitrite exposure at various salinities

ABSTRACT:   Experiments were conducted to determine the acute tolerance of juvenile (mean weight ± standard error, 9.9 ± 0.9 g) black sea bass Centropristis striata to environmental un-ionized ammonia-nitrogen (NH₃-N) and nitrite-nitrogen (NO₂-N) exposure at various salinities. Specifically, median lethal concentrations (LC50 values) of NH₃-N and NO₂-N at 24, 48 and 96 h of exposure were determined at salinities of 10, 20 and 30 g/L at 22°C. With the exception of LC50 values determined at 48 h, median lethal concentrations of NH₃-N to black sea bass were not influenced by environmental salinity; 24, 48, and 96 h LC50 values ranged from 0.81 to 0.85, 0.65–0.77, and 0.46–0.54 mg-NH₃-N/L, respectively. In contrast, tolerance of black sea bass to environmental NO₂-N was compromised at reduced salinities. Median lethal concentrations of NO₂-N to fish at 24, 48 and 96 h of exposure ranged from 288.3 to 429.0, 258.4 to 358.8 and 190.0 to 241.9 mg-NO₂-N/L, respectively. Results indicate that while juvenile black sea bass are relatively sensitive to acute NH₃-N exposure, they are highly resistant to NO₂-N exposure.     

EFFECTS OF METHOD OF ESTABLISHMENT ON TALL FESCUE AND ITALIAN RYEGRASS MIXTURES IN THE FOLLOWING YEAR

Tall fescue and Italian ryegrass mixtures react differently to management in the year of sowing. The decrease in yield of tall fescue and the increase in growth of red clover, caused by the use of a cover crop, was still evident in the following year. In both the spring grazing and total yield of the first harvest year, the Italian ryegrass/ white clover mixture was better than the tall fescue/white clover mixture when a cover crop was used. The reverse trend was recorded when the grass plus clover was sown without the cereal. In general, the addition of red clover to the tall fescue/ white clover, or Italian ryegrass/white clover mixture, increased the yield, but the magnitude of the increase was modified by management during establishment. The increase in total herbage yield and the reduction of white clover growth due to nitrogen application were both related to management in the year of sowing. Consideration should thus be given to method of establishment in the assessment of herbage seeds mixtures.     

The relationship between the degree of thrombocytopenia and infection with Ehrlichia canis in an endemic area

Ehrlichia canis is the causative agent of canine monocytic ehrlichiosis. In order to evaluate platelet counts as a screening test for E. canis in an endemic area, 217 whole blood samples from dogs were divided into three groups: 71 non-thrombocytopenic samples (group A, platelet counts greater than 200 000/mL) and 146 thrombocytopenic samples (less than 200 000/mL). The thrombocytopenic group was further divided into 62 with platelet counts between 100 000-200 000/mL (Group B) and 84 samples with less than 100 000 platelets/mL (Group C). All samples were examined for the presence of a segment of the Ehrlichia canis 16S rRNA gene using a nested polymerase chain reaction. Sixty-seven of the 217 samples (30.9%) were positive for the presence of the E. canis 16S rRNA gene; 53 (63.1%) of the group C samples and 13 (21%) of group B. Only one (1.4%) of the non-thrombocytopenic samples (Group A) was positive. These data support the concept that platelet counts may be a good screening test for canine monocytic ehrlichiosis, and that the magnitude of thrombocytopenia may increase the reliability of diagnosis.     

Increase in chemokines CXCL10 and CCL2 in blood from pigs infected with high compared to low virulence African swine fever virus isolates

Modulation of the expression of chemokines and chemokine receptors in whole blood was compared following infection of pigs with high and low virulence isolates of African swine fever virus. Levels of mRNAs for CCL2, CCL3L1, CCL4, CXCL10, CCR1 and CCR5 were significantly increased in at least one time point following infection in two experiments and CCL5, CCR9 and CXCR4 mRNA were significantly increased in one of the experiments. The results showed that greatest fold increases in mRNAs for CXCL10 and CCL2 were observed following infection of pigs. CXCL10 mRNA was increased by up to 15 fold in infected compared to uninfected pigs. CXCL10 protein was also detected in serum from pigs infected with the high virulence Benin 97/1 isolate. Levels of CCL2 mRNA were increased in pigs infected with high virulence Benin 97/1 isolate compared to low virulence OURT88/3 isolate and this correlated with an increase of greater than 30 fold in levels of CCL2 protein detected in serum from pigs infected with this isolate. An increase in overall chemotaxis active compounds in defibrinated plasma samples from Benin 97/1 infected pigs was observed at 3 days post-infection (dpi) and a decrease by 7 dpi as measured by chemotaxis assay using normal pig leucocytes in vitro. Increased levels of CXCL10 may either contribute to the activation of lymphocyte priming toward the Th1 phenotype or induction of T lymphocyte apoptosis. Increased levels of CCL2, a chemoattractant for macrophages, may result in increased recruitment of monocytes from bone marrow thus increasing the pool of cells susceptible to infection.     

Animal movement varies with resource availability,landscape configuration and body size: a conceptual model and empirical example

Landscape Ecology - Animals must move to find food, shelter and mates, and escape predation and competition. Changes in landscape configuration and resource availability can disrupt natural...     

Historical landscape ecology of an urbanized California valley: wetlands and woodlands in the Santa Clara Valley

Historical records provide information to land managers and landscape ecologists attempting to understand current trajectories in altered landscapes. In this study, we synthesized a heterogeneous array of historical sources to reconstruct historical land cover in California’s Santa Clara Valley (a.k.a. “Silicon Valley”). To increase and assess accuracy, we used the triangulation of overlapping, independent data sources and the application of certainty level standards. The region has been subject to extensive urbanization, so we also evaluated the applicability of historical landscape reconstructions to the altered landscape. We found evidence for five major land cover types prior to significant Euro–American modification. Valley freshwater marsh, wet meadow, alkali meadow, willow grove, and valley oak savanna have all experienced extreme decline (85–100%) since Euro–American settlement. However, comparison of historical land cover patterns to contemporary land use suggested several new strategies for environmental recovery, despite the limitations of surrounding urbanization. We also observed a temporal shift in riparian habitat along the mainstem of Coyote Creek, from a relatively open mixture of riparian scrub, sycamore woodland, and unvegetated gravel bars to dense riparian forest, likely resulting from stream flow regulation. By identifying former land cover patterns we provide a basis for evaluating local landscape change and setting restoration targets, including the identification of residual features and under-recognized land cover types. These findings suggest that reliable historical landscape reconstructions can be developed in the absence of standardized historical data sources and can be of value even in highly modified regions.     

Influence of land use on water quality in a tropical landscape: a multi-scale analysis

There is a pressing need to understand the consequences of human activities, such as land transformations, on watershed ecosystem services. This is a challenging task because different indicators of water quality and yield are expected to vary in their responsiveness to large versus local-scale heterogeneity in land use and land cover (LUC). Here we rely on water quality data collected between 1977 and 2000 from dozens of gauge stations in Puerto Rico together with precipitation data and land cover maps to (1) quantify impacts of spatial heterogeneity in LUC on several water quality indicators; (2) determine the spatial scale at which this heterogeneity influences water quality; and (3) examine how antecedent precipitation modulates these impacts. Our models explained 30–58% of observed variance in water quality metrics. Temporal variation in antecedent precipitation and changes in LUC between measurements periods rather than spatial variation in LUC accounted for the majority of variation in water quality. Urbanization and pasture development generally degraded water quality while agriculture and secondary forest re-growth had mixed impacts. The spatial scale over which LUC influenced water quality differed across indicators. Turbidity and dissolved oxygen (DO) responded to LUC in large-scale watersheds, in-stream nitrogen concentrations to LUC in riparian buffers of large watersheds, and fecal matter content and in-stream phosphorus concentration to LUC at the sub-watershed scale. Stream discharge modulated impacts of LUC on water quality for most of the metrics. Our findings highlight the importance of considering multiple spatial scales for understanding the impacts of human activities on watershed ecosystem services.