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851.
M. D. Vazquez-Illanes R. Barcia I. Ibarguren J. A. Villamarín J. I. Ramos-Martínez 《Marine Biology》1992,112(2):277-281
6-phosphofructo-2-kinase (PFK-2) from the mantle of the sea musselMytilus galloprovincialis Lmk, collected from the Ría de Arosa (NW Spain) in 1990, was purified 550-fold by extraction and sequential affinity chromatography on Affi-gel Blue and ATP-agarose columns. The enzyme was a dimer with a native molecular weight of 100 kilodaltons (KDa) and a subunitM
r of 53 KDa. PFK-2 activity is dependent on the presence of Pi. At physiological Pi concentrations, the enzyme exhibits hyperbolic kinetics with both ATP and Fru-6-P, withK
m values of 0.62 and 0.37 mM respectively. In vivo, PFK-2 activity is limited by the concentration of Fru-6-P which is low in comparison with theK
m for this substrate. Citrate and PEP inhibited PFK-2 activity. 相似文献
852.
The organization, general anatomy, and surface microanatomy of all regions of the gills of a representive bivalve mollusc, Placopecten magellanicus Gmelin, were studied using stereo-microscopic, histological, and scanning electron microscopic techniques. Individuals were collected in May and November 1985 from Chamcook Bay, New Brunswick, Canada. In addition to correcting earlier accounts of this structure, a number of new observations are reported. The orientation of the ciliated spurs appears to be responsible for the sinusoidal arrangement of the gill filaments. Micrographs showing the structure of the dorsal respiratory expansion are presented. The entire abfrontal surface of the principal filament, including the dorsal respiratory expansion, is densely ciliated and mucosecretory. These characteristics may aid in the establishment of a respiratory current and in the prevention of gill damage during escape responses. All nonciliated regions of the gill filaments are covered with microvilli, thus greatly increasing the surface area of the gill. The feeding mechanism is discussed in relation to the dorsal and ventral ciliated tracts. Symbiotic ciliate protozoans are constantly dislodged from the gill filaments and transported via the ventral mucus string to the buccal region. The nutritional implications of these observations are discussed. 相似文献
853.
Photosynthesis and respiration in Ahnfeltia plicata (Huds.) Fries (Gigartinales) was measured in a seawater flowthrough system at different temperatures, salinities and photon flux densities (PFD). The exchanges of dissolved oxygen and inorganic carbon were continuously recorded with an oxygen probe and a pH electrode measuring variation in CO2–HCO
3
-
equilibrium as pH changes. Highest apparent photosynthesis at moderate photon flux density (PFD 50 E m-2 s-1) was found at 15°C and 33 S. Photosynthesis was measured up to PFD 500 E m-2 s-1 and no light saturation was documented. In the present experimental set-up, with continuous supply of fresh seawater, the number of limiting factors during photosynthesis measurements is reduced. 相似文献
854.
Hugh?DrummondEmail author Cristina?Rodríguez Adriana?Vallarino Claudia?Valderrábano Gabriela?Rogel Emilio?Tobón 《Behavioral ecology and sociobiology》2003,53(5):287-296
According to the desperado sibling hypothesis, chicks of obligately siblicidal species kill their junior broodmates as early as possible because junior broodmates face dire ecological prospects and are consequently predisposed to aggressively overthrow elder broodmates by all-out aggression. The agonistic behavior of junior chicks is virtually unknown because they die so young. We investigated the agonistic behavior of hypothetical desperados by fostering junior brown boobies (Sula leucogaster, an obligately siblicidal species) into nests of the blue-footed booby (S. nebouxii, a facultatively siblicidal species) containing an older singleton blue-foot chick. Controls were junior blue-footed boobies fostered into the same situation. Junior brown boobies were 7 times more aggressive than controls and most of them dominated their elder and larger nestmates. Four of nine brown booby juniors showed relentless aggression, delivering up to 711 pecks, bites and pushes (including "expulsion pushes") per hour, thereby overwhelming nestmates 90% heavier and permanently expelling one of them from the nest. Similarly, in natural broods of two surviving brown booby chicks, the losing chick was 13 times as aggressive as blue-foot subordinates, up to at least age 7 weeks. Contrast of the two species of booby suggests the evolution of agonistic roles within broods may be partly driven by selection on potential victims to express a level and type of aggressiveness appropriate to their status-related ecological prospects. 相似文献
855.
Influence of industry on the geochemical urban environment of Mieres (Spain) and associated health risk 总被引:4,自引:0,他引:4
Loredo J Ordóñez A Charlesworth S De Miguel E 《Environmental geochemistry and health》2003,25(3):307-323
This study is concerned with the elemental composition of soils and street dust collected in an historical industrial city of approximately 27 000 inhabitants, where old Hg mining and metallurgical activities strongly affected the load of heavy metals in the urban environment. For the purpose of the study, representative samples of soils and street dust were collected at different locations in the whole urban area (3 km2). Elevated mean concentrations of As in soils and street dust (69 and 135 g g–1, respectively), and Hg (3.07 and 4.24 g g–1, respectively), compared to background levels and to those found in other cities, reflect the anomalous geochemical nature of these materials and the strong influence exerted by the old mining sites. 相似文献
856.
Copulatory plugs do not assure high first male fertilisation success: sperm displacement in a lizard
Pedro L. Moreira Vera L. Nunes José Martín Octávio S. Paulo 《Behavioral ecology and sociobiology》2007,62(2):281-288
Sperm competition selects for opposing male defensive and offensive reproductive traits, and its outcome may be determined
by the effectiveness to which one trait has evolved to out-compete the other. We tested the effectiveness of a first male
plug physical interference with a second male insemination (defence) vs the effectiveness of plug and associated sperm displacement
by a second male (offence) on the outcome of sperm competition in Iberian rock lizards. We conducted a double mating experiment
where we compared the proportion of eggs per clutch fertilised by the same second males (against the same first males) when
they copulated with females 30 min (first male plug adhered firmly inside the female cloaca) and 4 h (first male plug loosely
adhered or shed from the female cloaca) after first males. We found that second males fertilised the majority of the eggs
per clutch in the 30-min treatment, whereas fertilisations were equally shared between the two males in the 4-h treatment.
These results show that plugs have little defensive effectiveness, and thus, do not assure high first male fertilisation success.
Instead, sperm displacement appears to be associated with plug displacement. That is, because sperm embedded in first male
plugs, and displaced from competition for fertilisations by second males, is expected to increase in number with decreasing
time allowed for female sperm transport, second males thus enjoy higher fertilisation success. This study shows that offensive
plug displacement out-competes plug defensive role in Iberian rock lizards. Moreover, it reveals sperm displacement as a novel
sperm competition mechanism in reptiles. 相似文献
857.
858.
Roles of male residence and relative size in the social behavior of Iberian rock lizards, Lacerta monticola 总被引:2,自引:0,他引:2
Many studies on contest competition used residency asymmetry as a discrete variable. However, the probability of winning an
interaction may change as a continuous function of the value of the location where the encounter occurs. We performed a field
study to examine the importance of location within a home range and relative body size to the outcomes of agonistic interactions
between male lizards, Lacerta monticola. The distances to activity centers (the most used locations based on a density function of sightings) and relative size play
important roles in agonistic interactions and had interacting effects in natural conditions. On the other hand, previous studies
with lizards suggested that inferior competitors are able to avoid agonistic interactions in the field. Thus, we staged encounters
in the laboratory to examine the behavioral responses of smaller individuals. The responses of each focal smaller male were
measured in its own home cage (resident), in the cage of a larger male (intruder) and in a cage in which no male was previously
present (control). The predominant behavioral tactics of smaller males were avoidance when they are the intruders and displaying
when they are the residents. Submissive displays by smaller males may help reduce the costs of agonistic encounters. 相似文献
859.
Marta C. Soares Sónia C. Cardoso Isabelle M. Côté 《Behavioral ecology and sociobiology》2007,61(7):1015-1022
Predation risk is amongst the most pervasive selective pressures influencing behaviour and animals have been repeatedly shown
to trade-off foraging success for safety. We examined the nature of this trade-off in cleaning symbioses amongst Caribbean
coral reef fishes. We predicted that cleaning gobies (Elacatinus evelynae and Elacatinus prochilos) should prefer fish clients that pose a low risk of predation (e.g. herbivores) over clients that may have more ectoparasites
but pose a higher risk (e.g. piscivores). Our field observations revealed that cleaners did clean preferentially client species
with more parasites but predatory and non-predatory clients had similar ectoparasite loads. Despite the lack of a foraging
advantage for inspecting predators, cleaners did not avoid risky clients. On the contrary, a larger proportion of visiting
predators than non-predators was inspected, gobies initiated more interactions with predatory clients, and predators were
attended to immediately upon arrival at cleaning stations. This preferential treatment of dangerous clients may allow the
rapid identification of cleaners as non-prey item or may be due to the effect of predators on the rest of the cleaners’ clientele,
which avoided cleaning stations whilst predators were present. Dealing with potentially risky clients may allow gobies to
regain access to their main food source: non-predatory clients. 相似文献
860.
Valuation of climate-change effects on Mediterranean shrublands. 总被引:1,自引:0,他引:1
Pere Riera Josep Pe?uelas Verónica Farreras Marc Estiarte 《Ecological applications》2007,17(1):91-100
In general, the socioeconomic analysis of natural systems does not enter into the realms of natural science. This paper, however, estimates the human-welfare effects of possible physicochemical and biological impacts of climate change on Mediterranean shrublands over the coming 50 years. The contingent choice method was applied to elicit the trade-offs in perceived values for three climate-sensitive attributes of shrubland (plant cover, fire risk, and soil erosion) and for the costs of programs designed to mitigate changes. Soil erosion was found to be the attribute of shrubland that most concerned the population, followed by fire risk and then plant cover. An increase of 1% in the shrubland area affected by erosion was estimated to cost each person on average 2.9 euros per year in terms of lost welfare, a figure that is equivalent in terms of perceptions of social welfare to an increase of 0.24% in the shrub area burned annually and a decrease of 3.19% in the area of plant cover. These trade-off values may help ecologists, policy makers, and land managers to take social preferences into account. 相似文献