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Mean Mass (mean + mass)
Selected AbstractsMorphology and Histology of the Atlantic Bottlenose Dolphin (Tursiops truncatus) Adrenal Gland with Emphasis on the MedullaANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 2 2005L. S. Clark Summary This study provides the first detailed description of the Atlantic bottlenose dolphin (Tursiops truncatus) adrenal gland with emphasis on the medulla. Thirty-one dolphins of varying age and sex were used in this study. No statistical differences were found between the right and left gland mass, however, the left was typically greater. Mean mass for the right and left adrenal glands were 4.99 ± 0.513 and 5.36 ± 0.558 g, respectively. No statistical differences were found between average gland mass and sexual maturity or sex. The average cortex/medulla ratio was 1.22 ± 0.060 meaning approximately 48% is cortex, 41% is medulla, and 11% was categorized as other (i.e. blood vessels, connective tissue, etc.). The cortex contained pseudolobules and the typical zonation. A medullary band, consisting of highly basophilic staining cells was found at the periphery of the medulla. Projections of the medulla to the gland capsule were noted. Immunolabelling with polyclonal antibodies against the enzymes dopamine , hydroxylase and phenylethanolamine N-methyl transferase indicated that noradrenaline producing cells are found throughout the medulla including the medullary band while adrenaline producing cells are only found within the medullary band. Transmission electron microscopy confirmed the presence of two distinct cell populations within the medullary band and a single cell population throughout the medulla. [source] Coarse woody debris in Australian forest ecosystems: A reviewAUSTRAL ECOLOGY, Issue 8 2005GEMMA WOLDENDORP Abstract Coarse woody debris (CWD) is the standing and fallen dead wood in a forest and serves an important role in ecosystem functioning. There have been several studies that include estimates of CWD in Australian forests but little synthesis of these results. This paper presents findings from a literature review of CWD and fine litter quantities. Estimates of forest-floor CWD, snags and litter from the literature are presented for woodland, rainforest, open forest and tall open forest, pine plantation and native hardwood plantation. Mean mass of forest floor CWD in Australian native forests ranged from 19 t ha,1 in woodland to 134 t ha,1 in tall open forest. These values were generally within the range of those observed for similar ecosystems in other parts of the world. Quantities in tall open forests were found to be considerably higher than those observed for hardwood forests in North America, and more similar to the amounts reported for coniferous forests with large sized trees on the west coast of the USA and Canada. Mean proportion of total above-ground biomass as forest floor CWD was approximately 18% in open forests, 16% in tall open forests, 13% in rainforests, and 4% in eucalypt plantations. CWD can be high in exotic pine plantations when there are considerable quantities of residue from previous native forest stands. Mean snag biomass in Australian forests was generally lower than the US mean for snags in conifer forests and higher than hardwood forest. These results are of value for studies of carbon and nutrient stocks and dynamics, habitat values and fire hazards. [source] Effects of radio-transmitter antenna length on swimming performance of juvenile rainbow troutECOLOGY OF FRESHWATER FISH, Issue 4 2004K. J. Murchie Abstract,,, Technological advances have lead to the production of micro radio-transmitters capable of being implanted in fish as small as c. 5 g. Although the actual tags are small, transmitters are equipped with long antennas that can increase drag and tangle in debris. We examined the effects of radio-transmitter antenna length on the swimming performance of juvenile rainbow trout, Oncorhynchus mykiss, (N = 156, mean mass = 34 g, mean fork length = 148 mm). Although we tested a variety of different antenna lengths up to a maximum of 300 mm, only the longest antenna significantly impaired swimming performance relative to control fish (P < 0.001). There was no difference in swimming performance between the sham (surgery, but no transmitter) and the control fish (handled, but no surgery), suggesting that the surgical procedure itself did not negatively affect the fish. Regression analysis, however, indicated that there was a significant decrease in swimming performance associated with increased antenna length (R2 = 0.11, P < 0.001). In addition, when held in laboratory tanks, fish with the three longest antennas (150, 225 and 300 mm) frequently became entangled with the standpipe. We suggest that researchers, under the guidance of the tag manufacturer, trim antennas to the shortest possible length required to detect fish in their specific study area. Antenna length is clearly an important issue for small fish, especially for species that inhabit complex habitats where antennas may become entangled, and where fish must attain speeds near limits of their swimming capacity. Resumen 1. Los avances tecnológicos han llevado a producir micro radio-trasmisores capaces de ser implantados en peces de muy pequeño tamaño (,5 g). Aunque las marcas actuales son pequeñas, los trasmisores están equipados con antenas largas que pueden llegar a enredarse en los restos de vegetación. Examinamos los efectos de la longitud de la antena sobre la rutina natatoria de juveniles de Oncorhynchus mykiss (n = 156, peso medio = 34 g, longitud furcal media = 148 mm). 2. Aunque analizamos varias longitudes de antena, hasta 300 mm, solamente las de mayor longitud alteraron la rutina natatoria en relación a los peces control (P < 0.001). No hubo diferencia en la rutina natatoria entre individuos bajo cirugía pero sin trasmisores respecto de los individuos control (manipulados pero sin cirugía) lo que sugiere que los procedimientos de cirugía no afectaron negativamente a los peces. Sin embargo, análisis de regresión indicaron un declive significativo en la rutina natatoria asociado a la longitud de la antena (R2 = 0.11, P < 0.001). Además, al ser mantenidos en tanques, los individuos con las tres antenas mas largas (150, 225, y 300 mm) frecuentemente se enredaron con las tuberías. 3. Sugerimos a los investigadores que, bajo la dirección de los productores de marcas y antenas, consideren el uso de las antenas más pequeñas que permitan detectar a los peces en sus respectivas áreas de estudio. La longitud de la antena es una cuestión importante para los pequeños peces, especialmente para especies en hábitats complejos donde las antenas pueden llegar a enredarse y donde los peces pueden alcanzar velocidades casi al limite de su capacidad natatoria. [source] Reducing fish losses to cormorants using artificial fish refuges: an experimental studyFISHERIES MANAGEMENT & ECOLOGY, Issue 3 2008I. RUSSELL Abstract, The hypothesis that the introduction of artificial refuges might provide protection for fish and reduce the level of cormorant predation was tested in two, paired-pond, cross-over trials during the winters of 2003 and 2004, using a ,refuge' pond and an adjacent equivalently stocked ,control' pond. There were 77% fewer cormorant visits to the refuge pond than the control pond, on average. There was also a 67% fall in the mean mass of fish consumed per cormorant visit and 79% less fish mass lost in the refuge pond. The results are discussed in the context of interactions between cormorants and fish and the potential use of the tool in fisheries management. [source] Seasonal patterns in biomass smoke pollution and the mid 20th-century transition from Aboriginal to European fire management in northern AustraliaGLOBAL ECOLOGY, Issue 2 2007David M. J. S. Bowman ABSTRACT Aim, Globally, most landscape burning occurs in the tropical savanna biome, where fire is a characteristic of the annual dry season. In northern Australia there is uncertainty about how the frequency and timing of dry season fires have changed in the transition from Aboriginal to European fire management. Location, In the tropical eucalypt savannas that surround the city of Darwin in the northwest of the Northern Territory of Australia. Methods, Our study had three parts: (1) we developed a predictive statistical model of mean mass (µg) of particulates 10 µm or less per cubic metre of air (PM10) using visibility and other meteorological data in Darwin during the dry seasons of 2000 and 2004; (2) we tested the model and its application to the broader air shed by (a) matching the prediction of this model to PM10 measurements made in Darwin in 2005, (b) matching the predictions to independent measurements at two locations 20 km to the north and south of Darwin and (c) matching peaks in PM10 to known major fire events in the region (2000,01 dry seasons); and (3) we used the model to explore changes in air quality over the last 50 years, a period that spans the transition from Aboriginal to European land management. Results, We demonstrated that visibility data can be used reliably as a proxy for biomass burning across the largely uncleared tropical savannas inland of Darwin. Validations using independent measurements demonstrated that our predictive model was robust, and geographically and temporally representative of the regional airshed. We used the model to hindcast and found that seasonal air quality has changed since 1955, with a trend to increasing PM10 concentrations in the early dry season. Main conclusions, The results suggest that the transition from Aboriginal to European land management has been associated with an increase in fire activity in the early months of the dry season. [source] The responses of floodplain primary production to flood frequency and timingJOURNAL OF APPLIED ECOLOGY, Issue 1 2001A.I. Robertson Summary 1,River regulation and abstraction have dramatically altered the natural flow regime of many rivers world-wide, but experimental investigations of the biological effects are infrequent. In the mid-region of the Murray River, Australia, river regulation has reduced the frequency and duration of spring floods and increased the frequency of summer floods. We used controlled floods (treatments: no floods, spring floods, summer floods and spring + summer floods) to determine how the growth of river red gum Eucalyptus camaldulensis trees, aquatic macrophytes and biofilms varied with the seasonal timing and frequency of flooding. 2,After 6 years of controlled flooding, above-ground net production of wood by river red gum trees was equal and greatest in plots receiving spring + summer floods and summer floods (mean 496 g m,2 year,1). Production was significantly lower in plots receiving spring floods or no controlled floods, which had similar rates of production (mean 330 g m,2 year,1). 3,During 2 years of measurement in wetlands created by flooding, production and species richness of aquatic macrophyte were both greater in spring than in summer floods. The history of flood frequency at any experimental site did not affect macrophyte production or species richness. The aquatic macrophyte community in shallow regions of wetlands differed significantly with the seasonal timing of floods, but not flood frequency. 4,The accumulation of chlorophyll a and total mass of biofilm on wood surfaces in wetlands created by flooding were greater in spring (mean chlorophyll a, 0·88 µg cm,2; mean mass, 0·066 mg cm,2) than in summer floods (mean chlorophyll a, 0·09 µg cm,2; mean mass, 0·034 mg cm,2). The history of flood frequency at any experimental site did not affect accumulation of either the autotrophic or heterotrophic components of biofilms. 5,Spring flooding, while not as beneficial for tree growth, is critical for the growth of wetland macrophytes, the maintenance of macrophyte species richness, and favours better development of autotrophic biofilms. Maintenance of both the timber harvest and wetland conservation values of these floodplains will require the return of more natural flood flows in the spring period. Restoration of floodplain rivers requires a thorough understanding of the relationships between ecological functions and the natural flow regime. [source] Effects of reduced salinities on growth, food conversion efficiency and osmoregulatory status in the spotted wolffishJOURNAL OF FISH BIOLOGY, Issue 2 2001A. Foss No significant differences in mean mass between groups were found at any time in spotted wolffish Anarhichas minor, mean (±S.D.) initial mass 76 (±21) g, reared at salinities of 12, 17, 25 and 34, for 12 weeks at 8° C. Salinity did not have a significant effect on daily feeding rates, total food consumption, food conversion efficiency and protein efficiency ratio. Growth trajectories varied between groups, but no overall difference in growth was found. Plasma osmolality and plasma chloride levels decreased with salinity in a 48 h abrupt exposure trial, and in the growth experiment the low salinity groups (12 and 17,) exhibited significantly lower values compared with 25 and 34,. The decrease was moderate and concentrations were well within the range described for other marine species. The results indicate that the spotted wolffish is a strong osmoregulator which could be reared at various salinity levels. [source] Dynamics of extinction of a small population of the three-spined stickleback (Gasterosteus aculeatus L) caused by habitat modificationAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 4 2010R. J. Wootton Abstract 1.Abundance of a population of three-spined stickleback, Gasterosteus aculeatus L., in a small backwater of Afon Rheidol in mid-Wales (UK) was estimated annually each October from 1972 to 1999 by mark,recapture. 2.The population became extinct in 2000, because of land-use changes in 1995, which modified the drainage pattern through the backwater, causing the backwater to eventually dry up. 3.The final decline to extinction started from an estimated abundance of 1550 in 1998 and the abundance in 1999, the year before extinction, was 85. The smallest abundance from which the population showed an increase was 670. 4.Two years before extinction (1998), the population was characterized by an anomalously high proportion of small fish. 5.There was a significant power relationship between the years to extinction and population size, but if the data were analysed in two periods, 1972,1989 and 1990,1999, the relationship was only significant for the second period. 6.There was no relationship between time to extinction and per capita annual rate of increase (k), although values of k were unusually low in the last two years before extinction. 7.Time to extinction was not related to mean length, mean mass or the condition of the fish. 8.The results suggest that the indicators of impending extinction may vary with the causes of extinction and may be ambiguous, even when a long time-series of demographic data is available. Copyright © 2010 John Wiley & Sons, Ltd. [source] Bergmanns's size cline in New Zealand marine spray zone spiders (Araneae: Anyphaenidae: Amaurobioides)BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2010BRENT D. OPELL Members of the spider genus Amaurobioides are restricted to the spray zone of rocky marine coasts, where they construct and hunt from silk retreats. Collecting for this study shows these spiders to be distributed around the entire New Zealand coast. A Templeton, Crandall, and Sing (TCS) analysis of the ND1 mitochondrial gene places specimens from the North Island and the northern half of the South Island into a group distinct from Amaurobioides maritima O.P.-Cambridge, 1883, which is restricted to the southern half of the South Island. Females of this northern group exhibit latitude- and temperature-related clines in body length, body mass, and residual index of condition, with larger individuals with greater indices of condition being found at cooler, southern sites. This size cline also appeared in a broader geographical analysis that included Amaurobioides piscator Hogg, 1909 from the sub-Antarctic Auckland and Campbell Islands. Thirteen ND1 haplotypes are represented in the northern group. Both independent contrast analyses and standard regressions of the mean body lengths and mean masses of these haplotypes, and the mean latitudes and temperatures of the sites where haplotypes were present, document a Bergmann's size cline, and provide evidence for an underlying genetic component. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101, 78,92. [source] | |||||||||||||