A patch use model to separate effects of foraging costs on giving-up densities: an experiment with white-tailed deer (<Emphasis Type="Italic">Odocoileus virginianus</Emphasis>)

The giving-up density of food (GUD), the amount of food remaining in a patch when a forager ceases foraging there, can be used to compare the costs of foraging in different food patches. But, to draw inferences from GUDs, specific effects of foraging costs (predation risk, metabolic and missed opportunities costs) on GUDs have to be identified. As high predation risk, high metabolic costs and abundant food all should produce high GUDs, this does not allow us to infer directly the quality of a habitat. In order to separate the effect of each foraging cost, we developed an optimal foraging model based on food supplementation. We illustrate the use of our model in a study where we assessed the impact of a power line right-of-way in a white-tailed deer (Odocoileus virginianus) winter yard by determining whether the negative effects of cover loss outweigh the positive effects of browse regeneration.     

Lying down as a means of reducing fly harassment in red deer (Cervus elaphus)

Summary Resting time in red deer (Cervus elaphus) was shown to be more than twice as long on days when harassment by head flies (Hydrotaea irritans) was considered severe compared with days when fly harassment was estimated as low. Avoidance reactions in the deer decreased as soon as the deer reclined and became stabilized at a level corresponding to approximately 50% of the initial response frequency. The present observations do not give any clear indications as to whether it is the head flies per se or climatic factors that are the primary cause of reduced locomotory behaviour in the deer. It is concluded, however, that due to a causal relationship between the appearance of flies and certain types of weather, and because lying down has a relieving effect, inactivity may be an important part of the strategy used by red deer to cope with head fly harassment.     

Terrestrial runoff as a cause of outbreaks of Acanthaster planci (Echinodermata: Asteroidea)

Outbreaks of adult Acanthaster planci (Linnaeus) have appeared at irregular intervals, arriving 3 yr after heavy rains (>100 cm in 3 months) following droughts (<25 cm in 4 months) or 3 yr after rains exceeding intensities of 30 cm in 24 h. Outbreaks of A. planci follow typhoons that bring heavy rains, but do not follow dry typhoons of equivalent wind force. Outbreaks occur around the high islands in Micronesia and Polynesia, but not around the atolls at intermediate locations. Phytoplankton blooms appear off high islands at the beginning of the rainy season in bays with large watersheds and with sufficient residence time of the waters; these are the initial sites of A. planci abundance on Guam. The spawning seasons of A. planci occur at the beginning of the rainy season on both sides of the equator. I hypothesize that, on rare occasions, terrestrial runoff from heavy rains (following the dry season or a record drought) may provide enough nutrients to stimulate phytoplankton blooms of sufficient size to produce enough food for the larvae of A. planci. The increased survival of larvae results in an outbreak of adults 3 yr later. This hypothesis can be tested by predicting future outbreaks. An outbreak of A. planci on Saipan in the summer of 1981 was predicted on the basis of heavy rains in August 1978.Contribution no. 169, University of Guam Marine Laboratory     

Ecological sexual segregation in fallow deer (Dama dama): a multispatial and multitemporal approach

We questioned the different interpretations of ecological sexual segregation from a novel perspective, i.e., by carrying out diverse temporal and spatial scale analyses within a long-term study (1984–2003). Thus we combined spatial (small/large) and temporal (small/large) scale analyses to identify the factors generating sexual segregation in fallow deer in San Rossore, Italy. The study site was divided into an eastern sector characterized by human disturbance (DS) and a western undisturbed sector (US). According to census data, human presence increased in DS from 1984, and while females gradually abandoned it, males remained—thus supporting the predation risk hypothesis (large spatial and temporal scale)—and actually increased their presence in DS, where they seemingly benefited from a lower female density. This supported the indirect competition hypothesis. The analysis of data on a large temporal and small spatial scale confirmed that intersexual competition, in particular for grass, was higher in a crowded pasture in US. Observations by means of radio-telemetry of 23 adult females and 25 adult males (1997–2001, reduced temporal and large spatial scale) showed that large scale segregation was relevant during the day and disappeared at night, when disturbance was absent and also the females reached DS. This also supported the predation risk hypothesis. Moreover, sexes showed different habitat choices inside DS at night, thus supporting the forage selection hypothesis (small spatial and temporal scale). In conclusion, failure to address the whole set of combinations of spatial and temporal scale analyses would have led to monocausal explanations of ecological sexual segregation.     

Skin papillae as possible electroreceptors in the deep-sea eel Cyema atrum (Cyemidae: Anguilloidei)

Surface structure and internal organization of prominent skin papillae in the mesopelagic eel Cyema atrum have been investigated by scanning and transmission electron microscopy. Each papilla is club-shaped and possesses a pore at its distal end. A central rod, filled with cellular strands and surrounded by a 30 to 40 m wide matrix of clear material, runs from the tip to the base of the papilla. A cluster of cells, located 60 m below the surface of the skin, appears to be connected with the lateral line nerve. The lack of stereo- and kinocilia on the one hand, and the presence of a central rod and a terminal pore on the other, demonstrate that the cutaneous papillae in C. atrum cannot be regarded as typical lateral-line neuromasts. They share several features with electroreceptors, known from other fishes. It is postulated that C. atrum and other deep-sea species with similar skin papillae have been able to partially substitute vision and other senses useful for orientation by electroreception.     

Elaphoidella grandidieri (Harpacticoida: Copepoda): demographic characteristics and possible use as live prey in aquaculture

In freshwater ecosystems, rotifers and cladocerans are ideal prey for fish larvae whereas copepods, due to their purported low growth rate and predatory tendency, are not. We recently isolated the parthenogenetic Elaphoidella grandidieri (Gueme et Richard, 1893) a benthic freshwater harpacticoid, from a fish farm in the State of Morelos, central Mexico and tested its potential as a live prey organism for larval vertebrates. Population growth and life table demography experiments were conducted, in 100 ml recipients with 50 ml of test medium on a diet of Scenedesmus acutus at a density of 1.0 X 10(6) cell ml(-1); the former on live algae alone while the latter on live algae as well as detritus. We also conducted experiments to document the prey preference for this copepod by the larval Ameca splendens (Pisces: Goodeidae) and Ambystoma mexicanum (Amphibia: Ambystomatidae), fed the rotifer Plationus patulus, the ostracod Heterocypris incongruens, and the cladocerans Moina macrocopa and Daphnia pulex. Elaphoidella grandidieri is relatively easy to maintain under laboratory conditions, reaching densities (copepodites and adults) of more than 10,000 l(-1). The generation time ranged between 30-45 days, depending on the diet. The net reproductive rate was as high as 60 nauplii female(-1) day (1). Population growth rates ranged between 0.03 and 0.11 d(-1), live algae being the superior diet compared to detritus. Both predators showed no preference for E. grandidieri, but in the absence of alternate prey they consumed 80% of the harpacticoids offered. The data have been discussed in relation to the potential of E. grandidierias live food for aquaculture.     

Virus-like particles in Heterosigma akashiwo (Raphidophyceae): a possible red tide disintegration mechanism

Electron microscopical observations on algal samples collected in 1992 in the middle or final stages of a red tide in Hiroshima Bay, Japan, revealed virus-like particles (VLPs) in the red tide alga Heterosigma akashiwo (Class Raphidophyceae). The host cells appeared moribund and the VLPs were located in and around the nuclear area. The VLPs were icosahedral, ca. 185 nm in diameter, and generated from the periphery of several viroplasms. VLPs were also observed in three other types of H. akashiwo-like cells, which were morphologically distinguishable from each other. The appearance of VLPs in the red tide alga could explain the dramatically rapid termination of this red tide.     

Wind induced upwelling as a possible explanation for mass occurrences of epiphyticEctocarpus siliculosus (Phaeophyta) in the northern Baltic Proper

The quantity of epiphytic filamentous algae varies considerably in macroalgal vegetation along rocky shores of the northern Baltic Proper. The main species responsible for irregular mass occurrences is the summer annual brown algaEctocarpus siliculosus (Dillw.) Lyngb. In this study, data collected over a 3-yr monitoring period are related to hydrographical parameters. The tideless and brackish Baltic Sea is salinity stratified, and the salinity difference between surface and bottom waters can be used to indicate upwelling events. Mass occurrences developed when the salinity difference was low. These salinity differences explained 87% of the observed increase inE. siliculosus cover. We propose that the slight salinity changes themselves do not affect the growth ofE. siliculosus, but rather they can be used as indicators of short nutrient pulses. These nutrient pulses are not detected in standard water sampling, as they are utilised by both pelagic and benthic organisms within a few hours or days. If the proposed mechanism is true, changes in wind speed and direction have an important effect on the nutrient dynamics of littoral algal communities. A higher frequency of SW winds may cause mass occurrences of filamentous algae, which are often believed to indicate eutrophication of an anthropogenic origin.     

Genital shape correlates with sperm transfer success in the praying mantis Ciulfina klassi (Insecta: Mantodea)

The rapid divergence of male genitalia is a widely observed evolutionary phenomenon. Although sexual selection is currently regarded as providing the most likely driving force behind genital diversification, the mechanisms responsible are still debated. Here, we investigate the relationship between male genital morphology and sperm transfer in the praying mantid Ciulfina klassi using geometric morphometrics. The shape of male genitalia in C. klassi influenced sperm transfer duration and the number and proportion of sperm transferred, suggesting that genital morphology is under sexual selection in this species. Genital size however was not correlated with any aspect of sperm transfer. Intriguingly, two of the major genital shape components correlated positively with the number of sperm transferred, but negatively with sperm transfer duration. Hence, males that most effectively transfer sperm to the female spermatheca do so in a relatively short period of time. A direct negative relationship was also found between sperm transfer duration and sperm transfer success. Overall, our study suggests that the variable genital shape of Ciulfina may have been selected for more efficient sperm transfer.     

Male capacity as related to sperm production,pregnancy initiation,and sperm competition in deer mice (Peromyscus maniculatus)

Summary Limitations on male capacity may be important to the evolution of mating strategies and behavior. Sperm counts in successive ejaculates of deer mice (Peromyscus maniculatus) decreased progressively through six ejaculations and remained depressed the following day. Males were as effective in inseminating females in cycling estrus with their second two ejaculates as with their first two and as effective in inseminating postpartum females with their fifth as with their first. In sperm competition situations males competed with rested males as effectively with their fourth, fifth, and sixth ejaculates as with their first. Thus, although sperm counts decrease in successive ejaculates, males suffer no apparent functional deficiency as long as they continue ejaculating. It is not clear whether or not deer mice are honest salesmen but they appear to be honest ejaculators and usually are honest intromitters.     

Parental energy expenditure: a proximate cause of helper recruitment in the pied kingfisher (Ceryle rudis)

Summary Energy expenditure of adult Pied Kingfishers was measured with doubly-labeled water. Results were related to reproductive success of parents aided and unaided by helpers. Energetically stressed parents in a colony with poor food supply accepted potential helpers more often than unstressed birds in another colony where food was easily available. This treatment of helpers was reversed in both colonies through experimental manipulation of clutch size and hence energetic stress. Results are discussed in relation to the costs and benefits that helpers incur on the parents' fitness.     

Sex differences in the consequences of maternal loss in a long-lived mammal, the red deer (Cervus elaphus)

In several primates, the presence of mothers affects the growth, survival and reproduction of their offspring, but similar effects have not yet been demonstrated in ungulates. Here, we investigate the effects of the mother’s presence in a population of red deer (Cervus elaphus) on the Isle of Rum, Scotland, which is the subject of a long-term, individual-based study. We compared measures of performance including antler growth in young males and age at first reproduction in females and survival of deer with mothers still alive against those that have lost their mothers (orphans). We show that orphaning both before and after weaning increases the risk of a natural death for both sexes. For males, no maternal benefit was detectable past 24 months of age while, for females, post-weaning benefits continued throughout life. Orphaning resulted in compromised male physical condition as measured by a reduced probability of growing antlers by 16 months of age while no evidence for compromised reproduction was found in females. These results support assertions that post-weaning maternal associations affect the development and survival of offspring.     

Food alert in bumblebees (Bombus terrestris): possible mechanisms and evolutionary implications

The return of a successful bumblebee forager stimulates nestmates to leave the nest and search for food. Here we investigate the mechanisms by which this happens. Successful Bombus terrestris foragers perform irregular runs in their nest, often lasting for several minutes. Run duration is at its maximum when food has just been discovered. Running likely serves to distribute a pheromone, since the information flow between "runners" and "recruits" can be disrupted by eliminating air exchange, while leaving other potential means of communication intact. In addition, nectar stores in the nest may be monitored continuously. A sudden influx of nectar into the nest also causes measurable increases in forager activity. The implications of bumblebee recruitment behavior for the evolution of communication in bees are discussed.     

Carotenoid patterns in twenty-nine species of sponges in the order Poecilosclerida (Porifera: Demospongiae): a possible tool for chemosystematics

We assessed the utility of separated carotenoid mixtures for sponge systematics. Carotenoids were extracted from 29 species of 22 genera of 6 families for the demosponge order Poecilosclerida. Mixtures were separated (by thinlayer chromatography on silica gel) without chemical modification and after alteration by saponification, reduction or acetylation or a combination thereof. This approach allowed analysis of individual colonies of less than 1 g wet weight. Relationships among taxa were determined through use of Lawson's similarity index and discriminative analysis. Analysis of multiple runs of fractions from one individual of Ophlitaspongia pennata showed the method to be consistent and reliable. Comparison of specimens of species collected at different localities and times showed high correspondence of carotenoid patterns except in those species suspected of representing species complexes. Analysis of members of the family Clathriidae and of relationships within the order Poecilosclerida suggest that fatty acids esterified to carotenoids may be family-specific and of more taxonomic value than carotenoids. The importance of testing for seasonal, geographic and habitat variability in biochemical patterns is stressed. We discuss the significance of these methods to sponge systematics and their use in comparative studies.     

Prolonged withdrawal: A possible predator evasion behavior in Balanus glandula (Crustacea: Cirripedia)

The duration of cirral withdrawal in Balanus glandula (Darwin) varies by a factor of three depending on the type of stimulus applied. Contact with potential predators including thaidid gastropods (Thais emarginata, T. lamellosa), and forcipulate asteroids (Leptasterias hexactis, Pycnopodia helianthoides) elicits significantly longer withdrawal durations than contact with an herbivorous gastropod (Tegula pulligo), a grazing, spinulosid asteroid (Henricia leviuscula) or a neutral, brown algal stimulus (Fucus distichus). By substantially attenuating the release of metabolites, prolonged withdrawal probably increases the likelihood of being bypassed by nonvisual predators relying on chemical cues to verify that barnacles are alive. The reduced response to the non-predatory species indicates that this is not a generalized response to gastropods or asteroids, but rather that it appears to be specific to potential predatory species.     

Distribution and possible immobilization of lead in a forest soil (Luvisol) profile*

Geochemical analyses using a sequential extraction method and lead adsorption studies were carried out in order to characterize the distribution and adsorption of lead on each genetic horizon of a Luvisol profile developed on a pelagic clayey aleurolite. Clay illuviation is the most important pedogenic process in the profile studied. Its clay mineralogy is characterized by chlorite/vermiculite species with increasing chlorite component downward. The amount of carbonate minerals strongly increases in the lower part of the profile resulting in an abrupt rise in soil pH within a small distance. The Pb content of the soil profile exceeds the natural geochemical background only in the Ao horizon, and its amount decreases with depth in the profile without correcting for differences in bulk density, suggesting the binding of Pb to soil organic matter. According to the sequential extraction analysis the organic matter and carbonate content of the soil have the most significant effect on lead distribution. This effect varies in the different soil horizons. Lead adsorption experiments were carried out on whole soil samples, soil clay fractions, as well as on their carbonate and organic matter free variant. The different soil horizons adsorb lead to different extents depending on their organic matter, clay mineral and carbonate content; and the mineralogical features of soil clays significantly affect their lead adsorption capacity. The clay fraction adsorbs 25 more lead than the whole soil, while in the calcareous subsoil a significant proportion of lead is precipitated due to the alkaline conditions. 10 and 5 of adsorbed Pb can be leached with distilled water in the organic matter and clay mineral dominated soil horizons, respectively. These results suggest that soil organic matter plays a decisive role in the adsorption of Pb, but the fixation by clay minerals is stronger.*This study was presented at the 20th European SEGH conference in Debrecen, Hungary, 2002.     

Modelling effects of chemical exposure on birds wintering in agricultural landscapes: The western burrowing owl (Athene cunicularia hypugaea) as a case study

We describe an ecotoxicological model that simulates the sublethal and lethal effects of chronic, low-level, chemical exposure on birds wintering in agricultural landscapes. Previous models estimating the impact on wildlife of chemicals used in agro-ecosystems typically have not included the variety of pathways, including both dermal and oral, by which individuals are exposed. The present model contains four submodels simulating (1) foraging behavior of individual birds, (2) chemical applications to crops, (3) transfers of chemicals among soil, insects, and small mammals, and (4) transfers of chemicals to birds via ingestion and dermal exposure. We demonstrate use of the model by simulating the impacts of a variety of commonly used herbicides, insecticides, growth regulators, and defoliants on western burrowing owls (Athene cunicularia hypugaea) that winter in agricultural landscapes in southern Texas, United States. The model generated reasonable movement patterns for each chemical through soil, water, insects, and rodents, as well as into the owl via consumption and dermal absorption. Sensitivity analysis suggested model predictions were sensitive to uncertainty associated with estimates of chemical half-lives in birds, soil, and prey, sensitive to parameters associated with estimating dermal exposure, and relatively insensitive to uncertainty associated with details of chemical application procedures (timing of application, amount of drift). Nonetheless, the general trends in chemical accumulations and the relative impacts of the various chemicals were robust to these parameter changes. Simulation results suggested that insecticides posed a greater potential risk to owls of both sublethal and lethal effects than do herbicides, defoliants, and growth regulators under crop scenarios typical of southern Texas, and that use of multiple indicators, or endpoints provided a more accurate assessment of risk due to agricultural chemical exposure. The model should prove useful in helping prioritize the chemicals and transfer pathways targeted in future studies and also, as these new data become available, in assessing the relative danger to other birds of exposure to different types of agricultural chemicals.     

Eiseniella tetraedra (Savigny, 1826) (Oligochaeta: Lumbricidae) as a bioindicator of heavy metals

The objective of this study was to assess the potential of the earthworm Eiseniella tetraedra (Savigny, 1826) as a bioindicator for cadmium (Cd) and lead (Pb) exposure. The importance of earthworms in metal pollution monitoring is widely recognized in terrestrial ecosystems. In this study, the levels of Cd and Pb in soils and earthworm tissues were studied at two locations, Polur Falls and a riverside area located in Abali, in the Elburz Mountains in Iran. At both locations the concentration of Cd and Pb in earthworms was higher than in the surrounding soils and a significant difference was found between the two stations, the latter probably attributable to the (1) amount of pesticides that are used for crop treatment in Abali and (2) presence there of clay, which is known to be rich in Cd. Data indicate that E. tetraedra is an efficient bioaccumulator of Cd and Pb and might act thus serve as a bioindicator of exposure.     

The cause of size-assortative mating in the leaf beetle Trirhabda canadensis (Coleoptera : Chrysomelidae)

Summary Examples of positive assortative mating by body size are abundant but its causes remain controversial. I show that size-assortative mating occurs in the chrysomelid beetle Trirhabda canadensis and I test a series of alternative hypotheses to explain how this mating pattern comes about. Results suggest that assortative mating in this beetle is due to the greater ease with which size-matched pairs can achieve intromission, and not due to size-biased skews in the availability of mates or mate choice favoring large individuals. There was no correlation between male and female elytron length (a measure of body size) at the initiation of courtship, but pairs assorted positively by size at the onset of intromission. Moreover, in the laboratory, there was a negative correlation between male and female size for pairs engaged in courtship that terminated without mating. Assortative mating was not associated with a large-male mating advantage and there was no evidence of female choice of large males. Nor was there unequivocal evidence for male choice of large females; although mating females were slightly larger and considerably heavier than solitary females, males did not differ in the frequency with which they rejected large and small females. Assortative mating in T. canadensis appeared to be caused by the lower ability of mismatched pairs to achieve intromission after an encounter, both when males were larger and when they were smaller than the female.     

Hood construction as a spacing mechanism inCleistostoma kuwaitense (Crustacea: Ocypodidae)

The ocypodid crabCleistostoma kuwaitense inhabits the upper shores of the mudflats of Kuwait, where it constructs a semi-permanent mud hood over the entrance to its burrow. Between September and November 1986, data were collected on the distribution and orientation of the hoods and their openings to investigate the crab's social spacing system. Irrespective of density, the distribution of burrow hoods is non-random, tending towards a regular dispersion. A contributory factor for this dispersion pattern is that the surface hoods tend to increase the distance between adjacent burrows. The hood openings are randomly distributed with respect to compass direction but avoid directly facing those of nearest neighbours. In the absence of burrow plugging and eviction as used by other ocypodid crabs, construction of elongated hoods appears to be a good alternative for ensuring social spacing.