Ecomorphological constraints imposed by the kidney component measurements in honeyeater birds inhabiting different environments

The histological renal anatomy of 10 species of honeyeaters was examined quantitatively, using stereology. The kidneys of five species of predominantly wet zone inhabiting birds: the western spinebill Acanthorhynchus superciliosus , White-checked honeyeater Phylidonyris nigra . New Holland honeyeater Phylidonyris novaehollandiae , little wattlebird anthochaera chrysoptera and red wattlebird Anthochaera carunculata , were compared to five predominantly arid zone inhabiting birds: the grey-fronted honeyeater Meliphaga plumula , white-plumed honeyeater Meliphaga penicillata , white-fronted honeyeater Phylidonyris albifrons , spiny-checked honeyeater Acanthogenys rufogularis and yellow-throated miner Manorina flarigula. The kidneys were asymmetrical, with the left kidney being larger than the right kidney. Kidney mass was directly proportional to body mass (coefficient of correlation, r =+0·95), as was kidney volume to kidney mass (r =+1·0). Wet zone honeyeaters generally and a higher percentage and absolute volume of renal cortex, whilst arid zone honeyeaters generally had a significantly higher percentage and absolute volume of renal medulla. There were few differences between species, in either the percentage or absolute volume or luminal surface area of nephron components within the cortex. Within the medulla, wet zone honeyeaters generally had a higher percentage and absolute luminal surface area of collecting ducts, whilst arid zone honeyeaters had a higher percentage and absolute surface area of capillaries. This may be due to factors such as variations in diet and climate between habitats resulting in differences in honeyeater renal morphology which enable arid zone birds to conserve water and wet zone birds to conserve ions more efficiently.     

The retinopetal system in the turtle Pseudemys scripta elegans

Injections of 125I wheat-germ agglutinin or horseradish peroxidase into the eyes of turtles labeled retrogradely cells in a mesencephalic reticular area lying between the trochlear and the isthmic nuclei. Their number was small and they were found predominantly contralateral to the injected eye. These reticular neurons were not labeled following control injections into the orbital cavity and therefore are considered to project to the retina similar to correspondingly located neurons in some other vertebrates.     

Some comparative aspects of the organ distribution of superoxide dismutase activity in the freshwater turtle, Pseudemys scripta elegans.

1. Superoxide dismutase activities in five tissues of the relatively anaerobic freshwater turtle were compared with SOD activities in the same tissues of two mammalian species (mouse and rabbit) with a more usual pattern of dependence on O2 availability. 2. SOD activities in brain, lung and skeletal muscle, but not liver or cardiac muscle, are significantly lower in the turtle. The turtle also shows differences in the pattern of relative SOD activities in various tissues as compared to the two mammalian species. 3. The data indicate that a relationship does exist between SOD activities and O2 exposure in intact vertebrate systems, and is consistent with a physiological role for SOD in tissue O2 metabolism.     

Environment-specific shell shape variation in the boring mytilid Leiosolenus patagonicus

Environmental conditions induce phenotypic responses (behavioural, morphological and physiological) in many marine species. The boring mytilid Leiosolenus patagonicus inhabits different types of substrata, such as sandstone intertidal and hard subtidal substrata (here called ‘lifeless-substratum’) and shells of bivalve species (here called ‘live-substratum’), where they are exposed to different restrictions in their growth. We used geometric morphometric methods to compare the contour shell shapes from each type of substratum (live and lifeless) since we expected the body shape to differ between individuals from these different substrata. The results showed that the shell shape depends on the type of substratum where the larvae recruit. The mean shell shapes of individuals from the live-substratum are more slender than those of the individuals growing inside the lifeless-substratum. Individuals from live-substratum can adapt their phenotype depending on the oyster’s anti-parasitism responses, while in lifeless-substratum they are able to build their own refuges.     

Some observations on shell shape variation in Pacific Nucella

This paper considers the patterns of shell shape variation shown by Nucella canalicuata, N. emarginata and N. lamellosa from two areas of the Pacific Northwest: the shores near Friday Harbour on San Juan Island and near Bamfield on the west coast of Vancouver Island. No clear pattern of variation in association with changes in exposure was seen in either N. canaliculata or N. lamellosa . It appears that genetic influences are more important controls of shell shape than environmental selection in both these species. Nucella emarginata shows the nearest approximation to the pattern shown by the Atlantic species, N. lapillus , but only at the exposed end of the wave-action gradient. On those shores, enclaves from the most surf-washed open coast headlands have shells with proportionally larger apertures (and thus a shorter, squatter form) than their equivalents in local shelter. But, unlike in N. lapillus , the trend does not continue onto genuinely sheltered shores. Under these circumstances the species is generally rare and, where enclaves do occur, their shells are of much the same shape (although of a much larger size) as in more exposed situations.     

Individual boldness is linked to protective shell shape in aquatic snails

The existence of consistent individual differences in behaviour (‘animal personality’) has been well documented in recent years. However, how such individual variation in behaviour is maintained over evolutionary time is an ongoing conundrum. A well-studied axis of animal personality is individual variation along a bold–shy continuum, where individuals differ consistently in their propensity to take risks. A predation-risk cost to boldness is often assumed, but also that the reproductive benefits associated with boldness lead to equivalent fitness outcomes between bold and shy individuals over a lifetime. However, an alternative or complementary explanation may be that bold individuals phenotypically compensate for their risky lifestyle to reduce predation costs, for instance by investing in more pronounced morphological defences. Here, we investigate the ‘phenotypic compensation’ hypothesis, i.e. that bold individuals exhibit more pronounced anti-predator defences than shy individuals, by relating shell shape in the aquatic snail Radix balthica to an index of individual boldness. Our analyses find a strong relationship between risk-taking propensity and shell shape in this species, with bolder individuals exhibiting a more defended shell shape than shy individuals. We suggest that this supports the ‘phenotypic compensation’ hypothesis and sheds light on a previously poorly studied mechanism to promote the maintenance of personality variation among animals.     

Evolutionary responses of aquatic macroinvertebrates to two contrasting flow regimes

Hydrobiologia - Natural disturbances are agents of natural selection that drive multiple biological adaptations along evolutionary time. Frequent, high magnitude disturbances are expected to select...     

Comparative morphology of freshwater sculpin inhabiting different environmental conditions in the Chesapeake Bay headwaters

Environmental Biology of Fishes - We compared body morphology of two freshwater sculpin taxa that inhabit distinct environmental conditions in the Chesapeake Bay watershed of eastern North America:...     

Vascular smooth muscle contractile properties in the turtle Pseudemys scripta elegans

1. Turtle aortic rings were characterized by high frequency spontaneous contractile activity and variable responsiveness to constrictor agents.2. The tissue response was remarkably insensitive to temperature at a range of 37°–15°C.3. The contractile response was effectively blocked by the calcium channel antagonist nifedipine and was substantially dependent on extracellular calcium concentrations.4. Lowering the sodium concentration of the bath medium resulted in a strong, transient contraction followed by reduced responsiveness to norepinephrine and the absence of spontaneous activity.5. Disruption of the vessel endothelium resulted in enhanced and reduced responsiveness to norepinephrine (NE) and acetylcholine (ACh), respectively.6. The results indicate that the regulation of contractile function in turtle vascular smooth muscle differs in several respects from that of mammalian tissue, perhaps, reflecting the adaptation of the vasculature to low pressure and ectothermic conditions.     

The effect of aquatic plant abundance on shell crushing resistance in a freshwater snail

Most of the shell material in snails is composed of calcium carbonate but the organic shell matrix determines the properties of calcium carbonate crystals. It has been shown that the deposition of calcium carbonate is affected by the ingestion of organic compounds. We hypothesize that organic compounds not synthesized by the snails are important for shell strength and must be obtained from the diet. We tested this idea indirectly by evaluating whether the abundance of the organic matter that snails eat is related to the strength of their shells. We measured shell crushing resistance in the snail Mexipyrgus churinceanus and the abundance of the most common aquatic macrophyte, the water lily Nymphaea ampla, in ten bodies of water in the valley of Cuatro Ciénegas, Mexico. We used stable isotopes to test the assumption that these snails feed on water lily organic matter. We also measured other factors that can affect crushing resistance, such as the density of crushing predators, snail density, water pH, and the concentration of calcium and phosphorus in the water. The isotope analysis suggested that snails assimilate water lily organic matter that is metabolized by sediment bacteria. The variable that best explained the variation in crushing resistance found among sites was the local abundance of water lilies. We propose that the local amount of water lily organic matter provides organic compounds important in shell biomineralization, thus determining crushing resistance. Hence, we propose that a third trophic level could be important in the coevolution of snail defensive traits and predatory structures.     

Geographical variation in shell shape of the pod razor shell Ensis siliqua (Bivalvia: Pharidae)

The present study assessed the existence of variation in the shell shape of the pod razor shell (Ensis siliqua) throughout its distributional range in the north-eastern Atlantic. Shells of E. siliqua caught at seven collecting sites (three in Portugal, three in Spain and one in Ireland) were studied by geometric morphometric methods, using both landmark- and contour-based methods. Both approaches (landmarks inside the valves and shell outline) discriminated the shells from Aveiro (centre of Portugal) and Strangford Lough (Ireland) from those caught in the nearby localities (remaining Portuguese and Spanish sites, maximum distance of 550 km by sea). Landmark analysis revealed that shells from Aveiro were more similar to shells from Ireland (~1,500 km far away). Contour analysis revealed that shells from Aveiro had a shape with a comparatively larger height-to-width ratio, whereas shells from Ireland showed a slightly more curved outline than in the remaining sites. Landmark- and contour-based methods provided coherent complementary information, confirming the usefulness of geometric morphometric analyses for discerning differences in shell shape among populations of E. siliqua. A brief review of previous applications of geometric morphometric methods to modern bivalve species is also provided.     

Shape variation in a benthic stream fish across flow regimes

Evolution of fish body shapes in flowing and non-flowing waters have been examined for several species. Flowing water can select for fish body shapes that increase steady swimming efficiency, whereas non-flowing water can favor shapes that increase unsteady swimming efficiency. Benthic stream fishes often use areas near the substrate that exhibit reduced or turbulent flow, thus it is unclear which swimming forms would be favored in such environments, and how shape might change across flow regimes. To test the relationship between fish body shape and flow regime in a benthic stream fish, we used geometric morphometric techniques to characterize lateral body shape in mountain sucker (Catostomus platyrhynchus) across flow rates, using stream gradient as an indicator of stream flow. Mountain suckers from low-flow environments were more streamlined, consistent with steady swimming body shapes, whereas mountain suckers from high flows had deeper bodies, consistent with unsteady swimming body shapes. In addition, smaller individuals tended to have more robust body shapes. These patterns are opposite to those predicted for stream fishes in the mid-water column. The benthic stream environment represents a distinct selective environment for fish shape that does not appear to conform to the simple dichotomy of flowing versus non-flowing water.     

Immunocytochemical and biochemical studies of histamine in the retina of the turtle Pseudemys scripta

A combination of immunocytochemical and biochemical methods was used to study histamine in the turtle retina. Histamine-like immunoreactivity was localized within paraboloids of certain cone photoreceptors by use of two different antisera directed against histamine. Preincubation of eyecups in Ringer's containing 10 microM histamine selectively increased the immunoreactivity of these photoreceptor paraboloids. The present localization of histamine in paraboloids indicated that, although histamine is in photoreceptors of the turtle retina, it may play some metabolic or neuromodulatory role, and not function as a neurotransmitter.     

Prolonged diving and recovery in the freshwater turtle, Pseudemys scripta--IV. Effects of profound acidosis on O2 consumption in turtle vs rat (mammalian) brain and heart slices

The oxygen consumption of rat versus turtle brain and heart slices was compared as a function of extracellular pH and temperature. At pH = 6.20 rat (mammalian) brain and heart slices show a significant depression of oxygen consumption as compared to pH = 7.50 at temperatures of both 24 degrees and 37 degrees C. In the turtle oxygen consumption in brain and heart slices was not depressed at pH = 6.20 compared to pH = 7.50 at 24 degrees C and brain oxygen consumption was not significantly different at the two pH values at 37 degrees C. Turtle heart QO2 was depressed at 37 degrees C. The results suggest that extracellular acidosis depresses mitochondrial O2 uptake in mammalian brain and heart, playing a role in the bioenergetic manifestations of O2 depletion. Turtle brain mitochondria do not show a depression of QO2 at the acidotic pH. The resistance to acidosis of turtle brain mitochondria presumably enhances the possibility of survival following prolonged diving by maintaining ATP generation during the early diving period and during recovery.     

Cultivar variation in cotton photosynthetic performance under different temperature regimes

Cotton (Gossypium hirsutum L.) yields are impacted by overall photosynthetic production. Factors that influence crop photosynthesis are the plants genetic makeup and the environmental conditions. This study investigated cultivar variation in photosynthesis in the field conditions under both ambient and higher temperature. Six diverse cotton cultivars were grown in the field at Stoneville, MS under both an ambient and a high temperature regime during the 2006–2008 growing seasons. Mid-season leaf net photosynthetic rates (P_N) and dark-adapted chlorophyll fluorescence variable to maximal ratios (F_v/F_m) were determined on two leaves per plot. Temperature regimes did not have a significant effect on either P_N or F_v/F_m. In 2006, however, there was a significant cultivar × temperature interaction for P_N caused by PeeDee 3 having a lower P_N under the high temperature regime. Other cultivars’ P_N were not affected by temperature. FM 800BR cultivar consistently had a higher P_N across the years of the study. Despite demonstrating a higher leaf F_v/F_m, ST 5599BR exhibited a lower P_N than the other cultivars. Although genetic variability was detected in photosynthesis and heat tolerance, the differences found were probably too small and inconsistent to be useful for a breeding program.