Analysis of an intertidal population of the amphipod Gammarus palustris using a modified version of the egg-ratio method

An intertidal population of Gammarus palustris Bousfield was sampled over a 23-month period and analyzed by a modified form of the egg-ratio method. Total numbers and size-frequency distributions revealed small numbers in the early spring which later increased to a peak in the summer months. This was followed by a marked reduction near the end of sumer and a subsequent rise in numbers during the early fall. Finally there was a second decrease to very low numbers in the late fall and early winter. Average brood size was calculated and used as an indication of food limitation. Attempts to correlate this with per capita rate of change (r), birth rate ( \((\hat b)\) and death rate ( \((\hat d)\) ) suggested that the population increase in the early summer was food-rather than predator-limited. The late summer decline appears to be the result of predation pressure as well as food limitation. The fall peak is attributed to juvenile release from ovigerous femals escaping previous predation and to an increase in adult males resulting from a release in predation pressure. The winter decline may be due to adverse environmental conditions.     

Kin discrimination in the spotted hyena (<Emphasis Type="Italic">Crocuta crocuta</Emphasis>): nepotism among siblings

We examined patterns of affiliation, association, and aggression to inquire whether spotted hyenas (Crocuta crocuta) can distinguish among various groups of maternal and paternal siblings. If so, and if these animals conform to predictions of kin selection theory, then behavioral interactions among hyenas should vary with relatedness. We also considered familiarity-based recognition and phenotype matching as mechanisms hyenas might use to recognize kin. Patterns of affiliative behavior indicated that hyenas favored full-sibling littermates over half-sibling littermates or any other group of half-siblings. Rates of dyadic aggression generally did not vary with kinship. Hyenas associated more closely with half-sibling littermates than with non-littermate half-siblings, and hyenas affiliated more with maternal half-siblings than with paternal half-siblings, suggesting that familiarity-based cues might mediate discrimination among these sibling classes. In addition, operation of a phenotype-matching mechanism was suggested by the preference hyenas demonstrated during affiliative interactions for full- over half-sibling littermates, and by their lack of preference in these interactions for half-sibling littermates over non-littermate half-siblings. Phenotype matching was also suggested by our observation that paternal half-siblings cooperated more, and fought less, than did non-kin. Our data indicate that hyenas can discriminate among various types of siblings, that their social behavior conforms to predictions of kin selection theory, and that they recognize kin using mechanisms of both familiarity and phenotype matching.Communicated by S. Alberts     

The cost of mating with a non-virgin male in a monandrous butterfly: experimental evidence from the speckled wood, Pararge aegeria

Contrary to vertebrates, sperm production in insects may bear considerable costs for males. This is especially true in species that donate spermatophores containing sperm and nutrient-rich accessory gland products like in butterflies. Hence, spermatophores at first and subsequent copulations can differ in a quantitative and qualitative way. Such effects have particularly been shown in polyandrous species providing large spermatophores. Here we experimentally tested the effect of male mating status (virgin male vs recently mated male) on copulation duration, spermatophore size and females’ fitness components in a monandrous butterfly Pararge aegeria that typically donates small spermatophores. Copulations with non-virgin males lasted on average five times longer than that with virgin males and resulted in a spermatophore which was on average three times smaller. Number of eggs laid and female life span were not affected by the mating status treatment, but there was a significant effect on the number of living caterpillars a female produced, as copulations with virgin males resulted in higher numbers of larval offspring. Interestingly, the difference in spermatophore mass at the first and the second copulation increased with male body size. This suggests differential spermatophore allocation decisions among males of different size. Consequences for females and potential mechanisms influencing female fitness components are discussed. Given the small absolute size of spermatophores in P. aegeria, components other than consumable nutrients (perhaps hormones) should cause the observed effects.     

Feeding biology of the shrimp Rimicaris exoculata at hydrothermal vents on the Mid-Atlantic Ridge

A newly described species of shrimp, Rimicaris exoculata Williams and Rona, 1986, dominates the megafaunal community at two hydrothermal vent sites on the Mid-Atlantic Ridge. Behavioral observations and gut-content analyses indicate, that these shrimp ingest large amounts of sulfide particles from black smoker chimneys. We found no evidence for chemoautotrophic endosymbionts in R. exoculata, based on analyses of morphology, stable isotopes, lipopolysaccharides, and ribulose-1,5-bisphosphate carboxylase (RuBPCase) activity. Instead we suggest that the shrimp, are normal heterotrophs, grazing on free-living microorganisms associated with black smoker chimneys. We infer that high bacterial productivity is required to sustain populations of R. exoculata at these vent sites.     

A dispersal model for larvae of the deep sea red crab Geryon quinquedens based upon behavioral regulation of vertical migration in the hatching stage

Behavioral responses to gravity, hydrostatic pressure, and thermoclines are described for Stage I zoeae of the deep sea red crab Geryon quinquedens Smith. Survival and rate of development as a function of temperature is presented for all larval stages. Although temperatures between 10° and 25°C have no direct effect upon survival, development time is five times longer at 10°C than at 25°C. Stage I larvae show strong negative response to gravity. Swimming rate increases with an increase in pressure up to 20 atm above ambient at 11°C, but not at 15°C. Swimming rates at 15°C are higher than those measured at 11°C at each pressure tested. Stage I larvae readily penetrate sharp thermoclines. Potential dispersal ranges of G. quinquedens larvae in the Mid-Atlantic Bight are suggested based on larval behavior, development time, and coastal hydrography. A testable recruitment model is proposed for G. quinquedens.Contribution no. 1365 of the Center for Environmental and Estuarine Studies     

The relationship between dewlap size and performance changes with age and sex in a Green Anole (Anolis carolinensis) lizard population

Ornaments are believed to signal an individual's ability to reproduce successfully and/or survive. Since an individual's fitness is often influenced by multiple traits (e.g. number of copulations, ability to acquire nest sites or to escape predators), which are difficult to quantify simultaneously, we examine performance traits (bite force, jumping performance) believed to be relevant to an individual's fitness. Specifically, we ask whether variation in dewlap size is related to variation in body size, bite force and jumping ability in the lizard Anolis carolinensis. Our results show that dewlap size is correlated with jumping capacity across all individuals, whereas the relationships between dewlap size, body size and bite force differ depending on sex/age class. We argue that selection against relatively large dewlaps at the transition between small mature and large mature males might be responsible for the lack of a relationship within large males. The absence or presence of a correlation between dewlap size and bite force, on the other hand, might be explained by differences in behaviour, such as territory establishment, anti-predator tactics, and/or mate choice. Our work thus suggests that selective forces influencing the evolution of ornaments may operate differently on different sexes and life-history stages.     

Ecologically based management of rodents in the real world: applied to a mixed agroecosystem in Vietnam.

Rodents cause significant damage to lowland irrigated rice crops in the Red River Delta of Vietnam. A four-year study was conducted in 1999-2002 to examine the effectiveness of applying rodent control practices using the principles of ecologically based pest management. Four 100-150 ha study sites adjacent to villages were selected and farmers on two treated sites were asked to follow a set of rodent management practices, while farmers on the untreated sites were asked not to change their typical practices. Farmers on the treated sites were encouraged to use trap-barrier systems (TBS's; 0.065-ha early planted crop surrounded by a plastic fence with multiple capture traps; one TBS for every 10-15 ha), to work together over large areas by destroying burrows in refuge habitats soon after planting (before the rats reestablish in the fields and before the onset of breeding), synchronizing planting and harvesting of the their rice crops, cleaning up weeds and piles of straw, and keeping bund (embankment) size small (<30 cm) to prevent burrowing. A 75% reduction in the use of rodenticides and plastic barrier fences (without traps or an early crop) was achieved on treated sites. The abundance of rodents was low after implementation of the management practices across all sites. There was no evidence for an effect of treatment on the abundance of rodents captured each month using live-capture traps, and no difference in damage between treatments or in yields obtained from the rice crops. Therefore, ecologically based rodent management was equally effective as typical practices for rodent management. Farmers on the treated sites spent considerably less money applying rodent control practices, which was reflected in the comparative increase in the partial benefit:cost of applying ecologically based rodent management from 3:1 on treated sites and untreated sites prior to the implementation of treatments to 17:1 on treated sites in the final year of the project.     

Bestimmung von Redoxzonen in einem mineralölbelasteten Grundwasserleiter

Goal and Scope

The goal of this study is the investigation and the grafic presentation of the characteristic redox zonation in a mineral oil contaminated aquifer which will be formed in the plume downstream of the contamination source. Methanogenic conditions, sulfate-reduction, Fe(III)-reduction, Mn(IV)-reduction, nitrate-reduction, aerobic conditions. By that indications type and degree of microbial degradation which is the most important part in Natural Attenuation (NA) processes can be obtained easily.

Methods

Changes of the groundwater parameters Eh, O₂, NO ₃ ^? , SO₄ ^2?, Fe²⁺, Mn²⁺, HCO₃ ^?, Ca²⁺ will be measured upstream, downstream and also in the centre of the plume. The results will be presented in a sequence of special diagrams.

Results and Conclusion

When microbial degradation of hydrocarbons takes place, a microbial community will always use that electron acceptor from which it will gain a maximum of energy by the corresponding redox-reactions. This means as long as oxygen is available this will be used. After its depletion nitrate serves as electron acceptor leading via nitrite to the formation of nitrogen or ammonia. Manganese (IV) and Iron (III) species which are rather insoluble are mainly available from the soil-phase, can act as electron acceptor as next, leading to soluble Manganese (II) and Iron (II) compounds in groundwater. Finally before methanogenic conditions occur sulphate will become a suitable electron acceptor leading to the formation of hydrogen sulphide. All these processes of mineralization of the hydrocarbons will lead to the production of CO₂ and as consequence to an increase of HCO₃ ^? in groundwater changing the calcareous/carbonic acid-equilibrium. By that more soluble Ca(HCO₃)₂ is formed from insoluble CaCO₃, so the concentration from Ca²⁺ will also inerease. Thus, by the action of microorganisms, a typical redox-zonation and changes of other parameters will occur.

Recommendations and Perspective

To follow the changes in time and space of some characteristic groundwater parameters is a simple way to estimate the potential of microbial degradation in a contaminated aquifer considering Natural Attenuation (NA)-processes.     

Strike-induced chemosensory searching is absent in the cordylid lizard,Cordylus cordylus,a scleroglossan ambush forager

Summary Strike-induced chemosensory searching (SICS) was not detected experimentally in the cordylid lizard,Cordylus cordylus. Both components of SICS, a post-strike elevation in tongue-flick rate (PETF) and searching movements for attacked and released prey, were absent. The findings are consistent with previous data showing that PETF and/or SICS are lacking in all lizard families yet studied that forage primarily by ambush, but are present in actively foraging scleroglossan families and the herbivorous iguanian family Iguanidae. It is suggested that foraging behavior is a primary determinant of the presence or absence of SICS in lizards. Nevertheless, in most families in the two major clades, Iguania and Scleroglossa, the plesiomorphic foraging mode is retained. The findings agree with the prediction that SICS is absent in families lacking lingually mediated prey chemical discrimination (PCD), presumably due to selection against movement by ambush foragers that avoid being detected by either prey or predators because they remain motionless. Although PETF and SICS were absent, labial-licking and lingual movements similar to those observed after swallowing increased after biting prey, suggesting that the functions of these lingual movements may have been related to grooming. Locomotory movements did not increase following biting and appeared to represent avoidance of the experimenter.     

Patterns of metal soil contamination and changes in terrestrial cryptogamic communities

Correlations between terricolous bryophyte- and lichen- vegetation and edaphic parameters (pH, organic matter, nitrogen, Carbon/nitrogen ratio, Cation Exchange Capacity, and Cd, Pb and Zn soil contents) of soils submitted to a gradient of metal contamination in northern France were performed using statistical analysis. Six classes can be distinguished according to the low-, intermediate- and high-trace metal levels respectively, leading to the conclusion that bryophyte- and lichen-groupings have a strong bioindicative value of the heavy metal pollution of soils.