Evolutionarily stable sexual allocation by both stressed and unstressed potentially simultaneous hermaphrodites within the same population.

Factors influencing allocation of resources to male and female offspring continue to be of great interest to evolutionary biologists. A simultaneous hermaphrodite is capable of functioning in both male and female mode at the same time, and such a life-history strategy is adopted by most flowering plants and by many sessile aquatic animals. In this paper, we focus on hermaphrodites that nourish post-zygotic stages, e.g. flowering plants and internally fertilising invertebrates, and consider how their sex allocation should respond to an environmental stress that reduces prospects of survival but does not affect all individuals equally, rather acting only on a subset of the population. Whereas dissemination of pollen and sperm can begin at sexual maturation, release of seeds and larvae is delayed by embryonic development. We find that the evolutionarily stable strategy for allocation between male and female functions will be critically dependent on the effect of stress on the trade-off between the costs of male and female reproduction, (i.e. of sperm and embryos). Thus, we identify evaluation of this factor as an important challenge to empiricists interested in the effects of stress on sex allocation. When only a small fraction of the population is stressed, we predict that stressed individuals will allocate their resources entirely to male function and unstressed individuals will increase their allocation to female function. Conversely, when the fraction of stress-affected individuals is high, stressed individuals should respond to this stressor by increasing investment in sperm and unstressed individuals should invest solely in embryos. A further prediction of the model is that we would not expect to find populations in the natural world where both stressed and unstressed individuals are both hermaphrodite.

Rapid recovery of genetic diversity of dogwhelk (Nucella lapillus L.) populations after local extinction and recolonization contradicts predictions from life-history characteristics.

The dogwhelk Nucella lapillus is a predatory marine gastropod populating North Atlantic rocky shores. As with many other gastropod species, N. lapillus was affected by tributyltin (TBT) pollution during the 1970s and 1980s, when local populations became extinct. After a partial ban on TBT in the United Kingdom in 1987, vacant sites have been recolonized. N. lapillus lacks a planktonic larval stage and is therefore expected to have limited dispersal ability. Relatively fast recolonization of some sites, however, contradicts this assumption. We compared levels of genetic diversity and genetic structuring between recolonized sites and sites that showed continuous population at three localities across the British Isles. No significant genetic effects of extinction/recolonization events were observed in SW Scotland and NE England. In SW England we observed a decrease in genetic diversity and an increase in genetic structure in recolonized populations. This last result could be an artefact, however, due to the superposition of other local factors influencing the genetic structuring of dogwhelk populations. We conclude that recolonization of vacant sites was accomplished by a relatively high number of individuals originating from several source populations (the 'migrant-pool' model of recolonization), implying that movements are more widespread than expected on the basis of development mode alone. Comparison with published data on genetic structure of marine organisms with contrasted larval dispersal supports this hypothesis. Our results also stress the importance of local factors (geographical or ecological) in determining genetic structure of dogwhelk populations.

Stress promotes maleness in hermaphroditic modular animals.

Sex-allocation theory developed for hermaphroditic plants predicts that impaired phenotype or reduced parental survivorship caused by environmental stress should induce relatively greater allocation to the male function. We provide experimental evidence of stress-induced maleness, already well documented in flowering plants, in a modular animal. By using cloned copies of replicate genotypes, we show that the marine bryozoan Celleporella hyalina increases the ratio of male to female modules in response to diverse environmental stressors. Mating trials confirmed that paternity is determined by fair-raffle sperm competition, which should obviate local mate competition at characteristic population density and promote the advantage of increased male allocation. The demonstrated similarity to plants transcends specific physiological pathways and suggests that stress-induced bias toward male function is a general response of hermaphroditic modular organisms to impaired prospects for parental productivity or survival.

Responsiveness to brightness change in hooded rats: effects of sex and procedure.

In an investigation of recognition memory involving a preference test, hooded rats of both sexes were individually confined to the stem and choice area of a T- or Y-maze by means of clear Perspex barriers across each arm entrance that enabled the subjects to see into but not enter the arms. Following removal of the barriers and changing of one arm to opposite brightness, the first arm entered and the number of entries of and time spent in each arm were recorded. In the first experiment, rats entered first the arm that had been changed. During the first minute of observation, they also entered this novel arm more often and spent more time in it than the unchanged arm, irrespective of the type of change. In a second experiment, when the change was from one arm black and the other white to two black arms, more responsiveness occurred after 6-min prior exposure (without access) than after 3 min. In both experiments, the nature of the apparatus (T- or Y-maze) affected several outcomes, but the most significant influence was of the sex of the subjects. Females appeared less responsive to change than males as determined by entries of and time spent in the changed arm. Rather than inferiority of females in recognition or spatial memory, the sex effects were most likely due to their more rapid habituation to novelty possibly assisted by superior visual exploration capacities.

Sampling ozone exposure of Canadian forests at different scales: some case studies.

The use of passive samplers in extensive monitoring, such as that used in national forest health monitoring plots, indicates that these devices are able to determine both spatial and temporal differences in ozone exposure of the plots. This allows for categorisation of the plots and the potential for cause-effect analysis of certain forest health responses. Forest exposure along a gradient of air pollution deposition demonstrates large variation in accumulated exposures. The efficacy of using passive samplers for in situ monitoring of forest canopy exposure was also demonstrated. The sampler data produced weak relationships with ozone values from the nearest "continuous" monitor, even though data from colocated samplers showed strong relationships. This spatial variation and the apparent effect of elevation on ozone exposure demonstrate the importance of topography and tree canopy characteristics in plant exposure on a regional scale. In addition, passive sampling may identify the effects of local pollutant gases, such as NO, which may scavenge ozone locally only to increase the production of this secondary pollutant downwind, as atmospheric reactions redress the equilibrium between concentrations of this precursor and those of the generated ozone. The use of passive samplers at the stand level is able to resolve vertical profiles within the stand and edge effects that are important in exposure of understorey and ground flora. Recent case studies using passive samplers to determine forest exposure to ozone indicate a great potential for the development of spatial models on a regional, landscape, and stand level scale.

Water-borne sperm trigger vitellogenic egg growth in two sessile marine invertebrates.

A diverse array of sessile marine invertebrates mate by passive dispersal of sperm which fertilize the brooded eggs of neighbours. In two such species, a sea-mat (phylum Bryozoa) and an ascidian (phylum Chordata), vitellogenic egg growth is absent in reproductively isolated specimens, but is triggered by a water-borne factor released by conspecifics. In both of these colonial, hermaphroditic species, the active factor can be removed from water by filtration. The effect involves self-/non-self-recognition: water conditioned by a separate subcolony of the same genetic individual does not prompt oocyte growth. In each species, allosperm move from the surrounding water to the ovary and are then stored in close association with the growing oocytes. We concluded that sperm themselves are the water-borne factor that triggers the major phase of female reproductive investment. This mechanism is, to our knowledge, previously undescribed in animals, but has parallels with the initiation of maternal investment in flowering plants following the receipt of compatible pollen. The species studied may be representative of many other aquatic invertebrates which mate in a similar way. The stimulation of egg growth by allosperm could lead to intersexual conflict during oogenesis.

Intrinsic exploration in animals: motives and measurement.

Intrinsic exploration involves exploratory acts that are not instrumental in achieving any particular goal other than performance of the acts themselves. Of the theories proposed to account for the motivation of intrinsic exploration in animals, concepts of exploratory drive, optimal arousal and fear have featured prominently. But since no single approach has adequate explanatory or predictive power, it is probably sufficient to go no further than accept that organisms may have some type of `need' for sensory change which can be satisfied mainly by intrinsic exploration. Attempts to measure the phenomenon in the laboratory can be divided into forced tests in which locomotion and other motor responses are recorded in animals placed into a totally novel environments, and free tests involving measurements of active choices of differing degrees of novelty. Because of the difficulty of distinguishing between extrinsic and intrinsic exploration with activity indices, tests of free exploration are always preferable. These include novelty-related location preferences (including spontaneous alternation and responses to brightness change), object exploration and learning for exploratory rewards all of which can be viewed as reasonably valid measures of intrinsic exploration to a greater or lesser extent.

Effects of diazepam and cyclohexyladenosine on open-field behavior in rats perinatally exposed to caffeine.

Adult rat offspring earlier exposed to maternally ingested caffeine during both gestation and lactation were observed in an open field following acute administration of diazepam or cyclohexyladenosine. While both drugs reduced measures of locomotion and emotional reactivity, caffeine-exposed rats showed evidence of greater sensitivity to cyclohexyladenosine (but not diazepam) as determined by its effects on grooming behavior and tendencies to occupy the center squares of the apparatus. This suggested that adenosine (A1) rather than benzodiazepine receptor activity had been affected by the perinatal caffeine experience which also reduced locomotor activity while increasing center occupancy. The acute effects of diazepam and cyclohexyladenosine also depended largely on the sex of the subjects. Diazepam affected locomotor activity more and both drugs affected defecation less in females than in males. No other interaction involving sex was significant.

Foraging strategies of dogwhelks, Nucella lapillus (L.): interacting effects of age, diet and chemical cues to the threat of predation.

The effects of diet history, hunger and predation risk on short-term behavioral decisions of dogwhelks were tested in a specially designed test apparatus, termed a linear feeding array (LFA). The LFA consists of a sequential series of prey items mounted in a flume with unidirectional current directed towards a test (predatory) animal, and into which potential olfactory cues regarding predation risk are introduced. For dogwhelks the array was constructed vertically to accomodate intertidal foraging movements and is termed a vertical linear array (VLA). The behaviors exhibited by the dogwhelks were interpreted from distribution patterns in the VLA. Recent experimental studies and advances in optimal foraging theory provided the basis for the hypotheses tested in the VLA, which included: foraging and other behaviors are affected by predation, animals will avoid risk in the presence of predation threat, responses to predation threat will be proportional to the number and kinds of predator cues present, and starved animals will take greater risks than fed animals. We also test the proposition that foraging decisions are further modified by age. Three groups of juvenile and adult animals were maintained on diets of barnacles, mussels or no food (starved). The scent of crabs and damaged conspecifics served as olfactory cues to predation risk. Dogwhelks exhibited a range of behaviors in the VLA including: sheltering, searching, feeding, and aerial climbing. Distribution of animals in the tank assumed a relatively stable pattern after 2-3 h. These patterns were interpreted as the consequence of heirarchial decision making including: (i) a decision to become active, leaving the resting place or water refuge adopted during initial placement, followed by (ii) a decision to move vertically upwards or downwards, and (iii) a decision to attack prey when encountered. Analysis of movement patterns revealed that the initial decision, analogous to leaving a crevice as the tide comes in, was influenced in adults by predator cues and in juveniles by both predator cues and diet history. Perceived risk, as crab and damaged-conspecific odors, made individuals more likely to remain inactive, a risk-avoiding strategy for animals already in a refuge. Starved animals were more likely to descend into the tank and attack prey than fed animals. Our results support the hypotheses that higher-order predators affect the foraging decisions of dogwhelks and that juveniles and satiated animals are more sensitive to predation risk than starved ones. Together, these and earlier studies suggest that dogwhelks assess their environment before foraging, and that they are attuned to reducing the risks of mortality.

Lead, cadmium, arsenic and zinc in the ecosystem surrounding a lead smelter.

A lead smelter has been operating at Belledune in the province of New Brunswick, in eastern Canada, since 1966. This paper presents data on the concentrations of the four primary metals emitted from the smelter - lead, cadmium, arsenic and zinc - which were measured in the terrestrial environment near the smelter and the concentrate transport route. Deposition of these metals to the snowpack and the uptake by grass forage are discussed in relation to non-regulatory guidelines, toxicity and atmospheric emissions. A 1992 snowpack transect survey extending 0.5-40 km northwest, southeast and south of the smelter revealed lead concentrations of 2-3193 ppb, cadmium <0.10-49.7 ppb, arsenic <3.0-72.0 ppb, and zinc 3-401 ppb. Deposition estimates within this zone for lead were between 0.046 and 20.1 kg/ha/yr, cadmium <0.007 and 313 g/ha/yr, arsenic <0.016 and 453 g/ha/yr and zinc 0.020 and 2.52 kg/ha/yr. Concentrations of these metals in the snowpack were highest within 3 km of the smelter and were detectable at greater distances SE of the smelter. Lead was dispersed greater distances from the smelter than cadmium or arsenic. Snowpack samples collected within 5-20 m of the railway contained 140-7270 ppb of lead, 0.4-36.9 ppb of cadmium, <3.0-72.0 ppb of arsenic and 41-13100 ppb of zinc. Grass forage sampled within 0.6-16 km of the smelter contained lead 5-152 ppm, cadmium 0.10-4.1 ppm, and zinc 22-154 ppm. Highest concentrations of lead, cadmium and zinc in grass forage were found were found within 2.2 km of the smelter. Grass forage collected within 10-70 m of the railway contained lead 13-288 ppm, cadmium 0.4-1.3 ppm and zinc 98-831 ppm.

Effects on open-field behavior of diazepam and buspirone alone and in combination with chronic caffeine.

Effects of diazepam (1, 2 mg/kg) and buspirone (1.25, 2.5 mg/kg) on locomotor and rearing activity were observed in rats tested in an open field. Both doses of each drug reduced ambulation. However, for buspirone, this effect was confined to females. Walking and rearing was reduced by the higher dose of diazepam and rearing by both doses of buspirone. In rats that had ingested approximately 26 mg/kg/day of chronic caffeine for seven days prior to and immediately before testing, all effects of diazepam observed earlier failed to achieve significance except for ambulation. However, all earlier buspirone effects (including female-only decreased ambulation) were unaffected by the caffeine treatment. It was concluded that buspirone may be preferable to diazepam as an anxiolytic when in the presence of regular caffeine ingestion.

Effects of physostigmine on novelty-related location preferences.

Novelty-related location preferences and activity in an exploration box were recorded for male and female Wistar albino rats following intraperitoneal injections of 0.04 or 0.08 mg/kg of either physostigmine or neostigmine. Although rearing was reduced by the highest dose of both drugs and ambulation was reduced by the same dose of neostigmine, neither agent affected the significant preferences for novelty that typified all subjects. In a second experiment designed to assess the effects of 0.08 mg/kg of the two drugs administered during rather than after confinement to the familiar half of the apparatus, neostigmine reduced rearing, walking, and ambulation while increasing defecation, but physostigmine did not affect any response. While some minor motor impairment may have arisen from its peripheral effects, the lack of changes in novelty-related location preferences failed to support facilitation of either novelty avoidance or habituation by physostigmine suggested in previous studies.

Clonal structure of the introduced freshwater snail Potamopyrgus antipodarum (Prosobranchia: Hydrobiidae), as revealed by DNA fingerprinting.

Multi-locus DNA fingerprints were obtained from individuals of the hydrobiid snail, Potamopyrgus antipodarum (= P. jenkinsi), by using an RNA derivative (pSPT 18.15) of Jeffrey's 33.15 minisatellite core sequence. Whole-body homogenization of snails yielded 3.21 +/- 0.09 micrograms DNA per individual, producing complex profiles comprising 12-22 fragments within the 1.0-20.0 kilobase (kb) size range. Fingerprints from natural and experimental populations identified three distinct clonal genotypes corresponding to morphological strains A, B and C, with only rare mutational variants. Mother-offspring comparisons of genetic fingerprints revealed genetic stability during apomictic parthenogenesis. Data support the notion that British populations of P. antipodarum comprise three widespread obligate parthenogenetic clones resulting from a mid-19th Century introduction from Australasia. The present-day low levels of genotypic diversity are discussed in relation to the typical occurrence of P. antipodarum in man-made or immature habitats.

Effects of substrate brightness differences on isopod (Porcellio scaber) turning and turn alternation.

Woodlice ran faster in a straight runway when the floor was white than when it was black. When a runway with totally black or white floors (reflecting different levels of light) met up with equal areas of both brightnesses, woodlice turned in the direction of the runway brightness. Normal turn alternation after a forced turn was suppressed by this tendency to continue following the same substrate brightness when it involved moving in the direction of a repeating turn. However, when it involved turning in the direction of an alternating turn, the tendency to follow the same brightness had no effect on alternation.

Behavioral effects of exposure to caffeine during gestation, lactation or both.

Open-field behavior and latencies of emergence from a darkened chamber to a brightly lit arena were recorded at 1, 2, 4 and 6 months after birth in male and female rats that had been exposed to 26 or 45 mg/kg/day caffeine ingested by dams in their drinking water during gestation, 25 or 35 mg/kg/day during lactation or to the two low or high doses ingested during both gestation and lactation. One or both of the gestational or lactational doses reduced locomotor activity and increased defecation in the open field at all ages for males only. Rearing was decreased for both sexes by 25 mg/kg/day lactational caffeine. Numbers of rats that failed to or took longer than 1 min to emerge into the brightly lit arena were increased by 26 mg/kg/day gestational caffeine. All rats that had been exposed to either dose combination of caffeine during both gestation and lactation showed less locomotor and rearing activity, reduced tendencies to emerge within 1 min and, at 6 months of age only, more defecation in the open field. It was concluded that the effects of gestational and lactational exposure to caffeine were additive in their modification of the developing brain as reflected in decreased motor activity possibly arising from heightened emotional reactivity to the testing situation. Hypersensitivity of males to caffeine exposure during either gestation or lactation separately seemed to diminish when exposure was increased for all rats through experience of the drug during both gestation and lactation. Possible involvement of caffeine-induced increases in adenosine receptors in the type of results obtained was discussed.

Sex-and age-dependent effects of prenatal exposure to caffeine on open-field behavior, emergence latency and adrenal weights in rats.

Pregnant rats were provided with drinking water containing 0, 0.23 or 0.3 mg/ml of caffeine throughout gestation. These concentrations gave rise to daily doses of 0, 28 and 36 mg/kg. Open-field behavior and latencies to emerge from a darkened chamber were observed in offspring at regular intervals from 1 to 8 months after birth. The main results revealed increases in open-field locomotor and rearing activity with 28 but not 36 mg/kg/day. The opposite pattern characterized emergence latency. These changes were more typical of male rats particularly when older. Combining the present results with those of an earlier study by the authors strengthened the curvilinear trends observed and led to the conclusion that, low doses of prenatal caffeine increase activity and decrease emotionality. Higher doses may have the opposite effects to the point that the significant differences from control subjects reported earlier can occur. When 8 months old, female but not male rats prenatally exposed to 36 mg/kg/day of caffeine had significantly heavier adrenal glands than controls.

Methylscopolamine and conditioned location avoidance.

On alternate days, rats were confined to one side of a shuttlebox following IP administration of saline and to the other following the peripherally-acting muscarinic antagonist, methylscopolamine (1.2 mg/kg). They later avoided the side associated with the drug effect. By duplicating an earlier finding with centrally- and peripherally-acting scopolamine, this result identified aversive peripheral actions of the two drugs as mainly responsible for the effects observed.

Lack of spontaneous alternation in favor of perseveration in domestic fowls and pigeons.

When allowed successive free choices of the arms of a T-maze, domestic fowls and pigeons repeated rather than alternated entries of the two alternatives. Such perseveration was less when one arm was black and the other white than when both were grey. Perseveration increased between the beginning and the end of the experiment and was unaffected by confinement to a chosen arm for 30 or 60 seconds. Removal from a chosen arm may have provided relief from an aversive situation and thus reinforced subsequent re-entries of the same arm. The results were therefore accounted for by the adoption of a win-stay escape strategy.

Effects of adrenalin on novelty choices and activity in rats.

Rearing, ambulation and occupancy of the novel half of an exploration box were observed in Wistar albino rats following intraperitoneal injections of saline, 0.03 or 0.06 mg/kg adrenalin. All three responses were decreased by the drug in a dose-related manner. Adrenalin did not seem to impair ability to discriminate between novel and familiar stimuli since the percentage of rearing that occurred in the novel half was highest in rats who received the 0.06 mg/kg dose. It was concluded that the suppression of novelty choices (and probably rearing and ambulation) by adrenalin was mainly due to its aversive peripheral properties. Pretreatment with 20 mg/kg oxprenolol HCl largely prevented the effects observed earlier, thereby implicating -adrenoceptors in adrenalin's behavioral action.