Mate attraction by females in a sexually cannibalistic praying mantis

We studied mate attraction by females of the praying mantid, Tenodera aridifolia sinensis, testing honest signaling of mate availability versus deceptive signaling to attract males for sexual cannibalism. We experimentally varied female diet and mating history and measured the rate of attraction of a wild population of males to caged females. Honest signaling theory predicts that virgin females will attract males at the greatest rate whereas deceptive signaling predicts that hungry females (which are more likely to cannibalize males) will attract more males, particularly among non-virgin females. Our results show that hungry females did not attract more males than well-fed females. Indeed, the opposite was true: hungry females attracted significantly fewer males. Moreover, hungry females were no more likely than well-fed females to attract males subsequent to mating, and mated females attracted males at a lower rate than did virgin females. We also observed female T. aridifolia sinensis and male Mantis religiosa arriving at the caged females and we discuss the significance of these observations. The results refute the hypothesis of deceptive signaling and show that mate attraction signals of female T. aridifolia sinensis are honest indicators of female mate availability and a lower risk of sexual cannibalism.     

Feeding and predator-avoidance by the rose anemone Urticina piscivora

We investigated the influence of feeding rate on the behavior of the rose anemone Urticina piscivora. We predicted that anemones would travel less and be less willing to detach from the substrate in response to contact with a predator (Dermasterias imbricata) as feeding rate was experimentally increased. As predicted, anemones receiving 0 mussels (Mytilustrossulus) daily moved significantly more than those receiving either 1 or 2 mussels daily. Anemones receiving 0 mussels daily also detached significantly quicker in response to predator contact compared to the 1 mussel per day group, which in turn detached significantly quicker than did the 2 mussels per day group. A field test of the same prediction gave mixed results. We also examined whether anemones could detect feeding rates of neighbors. Movement rates of anemones receiving 1 mussel daily when neighbors received 0 mussels daily were compared with those when neighbors received 2 mussels daily. We predicted that if the subjects could detect feeding rates of neighbors, they should move less when neighbors received less food than themselves (since their position is relatively good) than when neighbors received more food. The results support this interpretation. Received: 21 August 1996 / Accepted: 22 October 1996     

Species-specific attraction to pheromonal analogues in orchid bees

Male orchid bees (Euglossini) collect fragrances from flowers and other natural sources, a behaviour that has shaped the euglossine pollination syndrome. Males store such chemicals in hind leg pouches and later expose them during courtship display. In the present study, we show that complex bouquets of two sympatric species of Eulaema, E. meriana and E. bombiformis, are chemically distinct. When exposed during bioassays at display perches individual hind leg extracts rapidly and consistently attracted other males of the correct species, even if derived from males of disparate localities (French Guiana and Panama). Conspecific males as well as females of E. bombiformis arrived at natural perch sites only from downwind, and two copulations were observed. Our findings demonstrate that acquired odours mediate exclusive attraction within species and support the idea that such fragrances are pheromone analogues. Their role in acquiring matings and during male–male interaction is discussed.     

Spatial-econometric analysis of attraction and repulsion of private conservation by public reserves

It is difficult for public agencies to make optimal reserve-site selections without knowing how new public reserves might influence the configuration of private conservation. Private land trusts protect much land in the USA, but little is known about how private groups respond to conservation decisions made by other conservation agents. To fill that gap, we analyze township-level spatial data on conservation in California, Illinois, and Massachusetts to explore relationships between the location of private and public conservation land. Using linear spatial-econometric models and Bayesian spatial probit models, we find evidence that private-protected acres are clustered together in space. In California, it appears that private land conservation is attracted towards places where the government has reserves. In Illinois and Massachusetts, however, it appears that private conservation shifts away from townships with government reserves due to a mixture of spatial repulsion and simple acreage displacement.     

Female choice in sage grouse: the roles of attraction and active comparison

Previous studies of female choice in sage grouse Centrocercus urophasianus have implicated both the acoustic quality and repetition rate of the stereotyped strut display as putative cues for female choice. Stages in the choice process at which specific components of male courtship display influence female decisions were investigated using field observations of female pre-mating behavior. Females visited a subset of territorial males and then actively chose one of these as a mate. The order in which males were visited suggested that females searched until an acceptable mate was found, rather than employing a “best-of-n” tactic. Numbers of females visiting a male were related to differences in an acoustical component of display (inter-pop interval) whereas the probability that a visiting female mated was related to display rate (Table 3), indicating that initial attraction and active choice are influenced by different components of display. In addition, inter-pop interval and display rate tended to covary inversely (Fig. 1), suggesting that attraction and active choice may impose conflicting selection pressures on display performance. Received: 11 November 1995/Accepted after revision: 16 March 1996     

Trade-off between mate guarding and mate attraction in the polygynous great reed warbler

Summary In a Swedish population of the polygynous great reed warbler Acrocephalus arundinaceus, about 40% of the males formed pairs with more than one female. Males sang two completely separated types of song: (1) long song when they tried to attract mates and (2) short shong when they guarded a fertile female. As soon as a male had attracted a female he immediately switched from long to short song and apparently guarded her for at least 3 days. Most males left their female and started singing long several days before her fertile period ended. This behavior probably increased the risk of cuckoldry. By assuming that males of polygynous species maximize their fitness over the whole breeding season (i.e., maximize fitness rate), we predicted longer mate guarding periods when the probability of attracting a second female was low and the risk of cuckoldry was high. These predictions were supported by observations. The probability of attracting a second female decreased during the breeding season and, in accordance, the number of days that males sang long song during the primary female's fertile period was negatively correlated with the time of the season. This trend held also for individual males when comparing mating periods of their primary and secondary female. The increasing rate of male intrusions with season may also have contributed to the increasing mate guarding periods. Offprint requests to: D. Hasselquist     

Reproductive enhancement by helpers and an experimental inquiry into its mechanism in the bicolored wren

Summary As part of continuing studies of sociality in the wren genus Campylorhynchus we have been studying the bicolored wren — a facultatively cooperative breeder — for the past 6 years in the central Venezuelan savanna. Reproductive groups have ranged in size from 2 to 5. In one of our study populations, only about 15% of the groups contained helpers, and nearly all these contained only a single male helper (Fig. 2). In an adjacent population, the majority of groups contained helpers, and more than half of these contained several helpers of either sex. Territory size is, on average, much smaller in the latter population. In these populations the presence of a single helper is associated with a three-fold increase in reproductive success (Table 1). Additional helpers are not associated with further reproductive enhancement. Enhancement is chiefly due to an increased proportion of nest starts that eventually produce independent juveniles. This reproductive enhancement is not merely an epiphenomenon resulting from the presence of helpers on territories which are superior for other reasons, such as greater resource availability or the quality of particular parents. It is also not a function of the mean or variance in nestling feeding rate. Predator exclusion experiments, in which certan nests were artificially protected from terrestrial predators, suggested that the mechanism of reproductive enhancement was heightened effectiveness of nest defense. Helpers are usually nondispersers from the parental territory, and have always been found to be close relative of the nestlings that they assist in rearing.     

Waterfowls habitat modeling: Simulation of nest site selection for the migratory Little Tern (Sterna albifrons) in the Nakdong estuary

This paper aims to find patterns in nest site selection by Little Terns Sterna albifrons, in the Nakdong estuary in South Korea. This estuary is important waterfowl stopover and breeding habitat, located in the middle of the East Asia-Australasian Flyway. The Little Tern is a common species easily observed near the seashore but their number is gradually declining around the world. We investigated their nests and eggs on a barrier islet in the Nakdong estuary during the breeding season (May to June, 2007), and a pattern for the nest site selection was identified using genetic programming (GP). The GP generated a predictive rule-set model for the number of Little Tern nests (training: R² = 0.48 and test: 0.46). The physical features of average elevation, variation of elevation, plant coverage, and average plant height were estimated to determine the influence on nest numbers for Little Tern. A series of sensitivity analyses stressed that mean elevation and vegetation played an important role in nest distribution for Little Tern. The influence of these two variables could be maximized when elevation changed moderately within the sampled quadrats. The study results are regarded as a good example of applying GP to vertebrate distribution patterning and prediction with several important advantages compared to conventional modeling techniques, and can help establish a management or restoration strategy for the species.     

Feeding habits of the dungeness crab Cancer magister as determined by the index of relative importance

Specimens of the Dungeness crab Cancer magister, were collected subtidally and intertidally from an estuary in Washington State, USA in June and September 1980, and January, April, May and July, 1981. Gut contens of freshly collected crabs were analyzed by the Index of Relative Importance; for each prey taxon, this method measured frequency of occurrence, percentage of total biomass, and percentage of total numbers consumed. The most important higher taxon eaten was fish; however, the most important prey genus was the shrimp Crangon spp. There was greater predation on Crangon spp. at night at the intertidal site, and during winter and spring when the shrimp were most abundant there. Feeding activity, as indicated by a weight-specific gut-fullness index, showed no consistent diel pattern. There were significant ontogenetic changes in feeding patterns: first-year crabs preyed primarily on very small bivalves or small crustaceans including their conspecifics; second-year crabs preferred Crangon spp. and fish, and third-year crabs preyed less on Crangon spp. and more on fish. Such changes in feeding habits with ege could be purely due to mechanics of food handling, but might also reduce competition among age groups of crabs, possibly partitioning resources within the estuary. Findings are discussed in terms of optimal foraging and compared to other similar studies.Contribution No. 599, School of Fisheries, University of Washington, Seattle, Washington 98195, USA     

Feeding by larvae of intertidal invertebrates: assessing their position in pelagic food webs

One of the leading determinants of the structure and dynamics of marine populations is the rate of arrival of new individuals to local sites. While physical transport processes play major roles in delivering larvae to the shore, these processes become most important after larvae have survived the perils of life in the plankton, where they usually suffer great mortality. The lack of information regarding larval feeding makes it difficult to assess the effects of food supply on larval survival, or the role larvae may play in nearshore food webs. Here, we examine the spectrum of food sizes and food types consumed by the larvae of two intertidal barnacle species and of the predatory gastropod Concholepas concholepas. We conducted replicated experiments in which larvae were exposed to the food size spectrum (phytoplankton, microprotozoan and autotrophic picoplankton) found in nearshore waters in central Chile. Results show that barnacle nauplii and gastropod veligers are omnivorous grazers, incorporating significant fractions of heterotrophs in their diets. In accordance with their feeding mechanisms and body size, barnacle nauplii were able to feed on autotrophic picoplankton (<5 microm) and did not consume the largest phytoplankton cells, which made the bulk of phytoplankton biomass in spring-summer blooms. Balanoid nauplii exhibited higher ingestion rates than the smaller-bodied chthamaloid larvae. Newly hatched C. concholepas larvae also consumed picoplankton cells, while competent larvae of this species ingested mostly the largest phytoplankton cells and heterotrophic protozoans. Results suggest that persistent changes in the structure of pelagic food webs can have important effects on the species-specific food availability for invertebrate larvae, which can result in large-scale differences in recruitment rates of a given species, and in the relative recruitment success of the different species that make up benthic communities.     

Lectin-induced enhancement of superoxide anion production by red tide phytoplankton

Chattonella marina, a raphidophycean flagellate, is a highly toxic red tide phytoplankton which causes severe damage to fish farming. Recent studies demonstrated that Chattonella spp. continuously release superoxide anions (O₂ ⁻) while they are living. Heterosigma akashiwo, another raphidophycean flagellate, also produces O₂ ⁻. In the present study, we found that lectins such as concanavalin A (Con A), wheat germ agglutinin (WGA), and castor bean hemagglutinin (CBH) stimulated  C. marina and H. akashiwo to generate enhanced amounts of O₂ ⁻ in a concentration-dependent manner. The lectin-specific sugars potently inhibited the lectin-induced increase of O₂ ⁻ production, suggesting that the effects of lectins are mediated mainly through the interaction of these lectins with carbohydrate moiety present on the flagellate cell surface. In contrast to the potent ability of native Con A (tetravalent), succinylated Con A (divalent) showed only a slight stimulative effect on these flagellates. O₂ ⁻ production was totally inhibited by treatment with proteinase K for 30 min, without affecting the viabilities of flagellates. These results suggest that cell-surface redox enzymes may be involved in O₂ ⁻ production, and such enzymes are responsible for the lectin-stimulation. Received: 21 August 1997 / Accepted: 8 January 1998     

Mainstreaming the social sciences in conservation

Despite broad recognition of the value of social sciences and increasingly vocal calls for better engagement with the human element of conservation, the conservation social sciences remain misunderstood and underutilized in practice. The conservation social sciences can provide unique and important contributions to society's understanding of the relationships between humans and nature and to improving conservation practice and outcomes. There are 4 barriers—ideological, institutional, knowledge, and capacity—to meaningful integration of the social sciences into conservation. We provide practical guidance on overcoming these barriers to mainstream the social sciences in conservation science, practice, and policy. Broadly, we recommend fostering knowledge on the scope and contributions of the social sciences to conservation, including social scientists from the inception of interdisciplinary research projects, incorporating social science research and insights during all stages of conservation planning and implementation, building social science capacity at all scales in conservation organizations and agencies, and promoting engagement with the social sciences in and through global conservation policy‐influencing organizations. Conservation social scientists, too, need to be willing to engage with natural science knowledge and to communicate insights and recommendations clearly. We urge the conservation community to move beyond superficial engagement with the conservation social sciences. A more inclusive and integrative conservation science—one that includes the natural and social sciences—will enable more ecologically effective and socially just conservation. Better collaboration among social scientists, natural scientists, practitioners, and policy makers will facilitate a renewed and more robust conservation. Mainstreaming the conservation social sciences will facilitate the uptake of the full range of insights and contributions from these fields into conservation policy and practice.     

Feeding by the sand crab Portunus pelagicus on material discarded from prawn trawlers in Moreton Bay,Australia

A field and laboratory study in 1984–1985 using the foregut contents of crabs caught in Moreton Bay, Queensland, when trawling was underway, showed that animals discarded from trawls constituted about 33% of the diet. Portunus pelagicus can fill its foregut in about 8 min and clear it completely of tissues in about 6 h, except for fish bone which requires about 24 h. P. pelagicus used a zigzag search pattern to find food and moved towards it at a mean point-to-point speed of 290 m h^-1 (8 cm s^-1). Underwater still photography on the trawl grounds showed that P. pelagicus was the most common scavenger attracted to a bait that simulated trawl-discards, and that it was most active at dusk. Trawler-discards at periods of high food demand in summer may allow larger populations of P. pelagicus to exist than would otherwise occur.     

Feeding behavior and acquisition of zooxanthellae by planula larvae of the sea anemone Anthopleura elegantissima

Symbiotic associations between cnidarians and photosynthetic dinoflagellates (i.e., zooxanthellae) are common in the marine environment. Many symbiotic cnidarians produce offspring that are initially nonsymbiotic. These new hosts must acquire symbiotic algae from environmental sources. We examined zooxanthella acquisition by laboratory-reared planula larvae of the temperate sea anemone Anthopleura elegantissima. Larvae ingested zooxanthellae while they were feeding. However, the signal that prompted larval feeding behavior did not originate from the symbiotic algae; the addition of algal cells to larval cultures never elicited a feeding response. In contrast, the addition of macerated animal tissue from several sources invariably generated a strong feeding response, which resulted in the larvae indiscriminately ingesting any particulate matter that was present, including zooxanthellae or other unicellular algae. Ingested zooxanthellae were incorporated into endodermal cells, where they remained undigested, while all other ingested material was digested or expelled within 24 h. Our results provide evidence that one source of zooxanthellae likely to serve as a route of infection in the natural environment is zooxanthella-laden mucus egested by anemones. This egested material fulfilled both of the criteria necessary for successful infection: it prompted larvae to begin feeding and provided an abundant supply of zooxanthellae that were ingested and taken up into endodermal cells of the new host.     

Interspecific attraction to the mobbing calls of black-capped chickadees (Parus atricapillus)

The species and number of birds attracted to playbacks of mobbing calls and song of the black-capped chickadee, Parus atricapillus, were compared. The chickadee vocalizations were played at abandoned chickadee nests, and the numbers and species of other birds that approached the speaker were tallied. Few non-chickadees were observed in the area when the song was played. That significantly more birds approached the speaker and displayed mobbing behavior during the mobbing call playback suggests that black-capped chickadee mobbing vocalizations carry meaning for at least ten other avian species. This finding supports the idea that species subjected to the same predators in an area may benefit by recognizing each others’ predator calls. This recognition may be facilitated by the similar structure of different species’ mobbing calls and also a learned association of another species’ call with the presence of a predator. Received: 23 March 1995 /Accepted after revision: 28 October 1995     

重金属污染土壤的电动原位修复技术研究

电动力学修复技术作为一种新型的修复技术,由于其处理土壤污染的高效性,近几年来受到了越来越多的关注。综述了电动力学修复技术原理及近几年来其在重金属修复中的最新研究进展,阐述了电动力学修复技术相对于其它修复技术的优势,并指出了电动修复技术中需要克服的技术障碍,探讨了其大规模商业应用的可行性。电动技术能够强化土壤物质的传质过程,能够高效、快速定向迁移土壤中重金属离子达到去除的目的;同时电动技术可以与其它修复技术结合发展出系列组合修复技术,具有广泛的应用前景。从单一电动到复合电动是今后电动力学技术发展的重要方向。目前对污染物质复合电动力学效应下的迁移机理及模型、不同土壤性质(组分、酸碱性等)对于污染物质去除效率及其调控措施的研究仍需进一步深入。     

Feeding,food preference,and the uptake of food energy by the supralittoral isopod Ligia pallasii

Analyses of gut contents of freshly collected Ligia pallasii (Brandt) showed that the principal foods were encrusting diatoms, insect larvae, occasional members of the same species, and a variety of red and green seaweeds growing in the upper interiidal tidepool habitat. L. pallasii prefers to eat the green seaweed Ulva sp., and the brown alga Nereocystis luetkeana, when given a choice between several seaweeds, although neither of these forms is normally accessible to the isopods. The absorption (assimilation) of food-energy was 78% on a diet of Ulva and 55 to 76% on a diet of N. luetkeana—representative values for an algivorous invertebrate. A correlation analysis on the relationship of feeding preference of L. pallasii with calorific value of 7 potential seaweed foods suggested that feeding preference in this species is related to factors other than energy content of the food. Food preferences of invertebrates are discussed in relation to calorific value, accessibility, and to various nutritional factors.     

Feeding and non-feeding aggression can be induced in invasive shore crabs by altering food distribution

Human activity can have a large impact on surrounding ecosystems. For example, humans alter resource distributions for other species, potentially modifying these species competitive dynamics. These changes in local competitive processes are frequently associated with species invasions. Here, we investigate how differences in resource distribution affect competitive behaviour using the highly invasive European shore crab (Carcinus maenas). Using a controlled laboratory experiment in combination with behaviour assays and social network analysis, we show that individuals feeding in habitats with clumped food distributions are more aggressive than individuals feeding in habitats where food is evenly dispersed, and this aggression is present even on days where crabs are not feeding. Additionally, this persistent aggression can be induced, suggesting that individuals of this invasive species possess the flexibility to modify their competitive behaviours in response to differences in food distributions. Furthermore, we show how these individual responses can lead to changes in overall organisation of aggressive interactions within a population. We discuss these results in relation to how human impacts can have long-term effects on competitive behavioural strategies, and how behavioural flexibility can allow invasive species to colonise and persist in highly impacted sites such as urban ecosystems.     

Feeding habits of marine cladocerans in the Inland Sea of Japan

Natural food items of five species of marine cladocerans, Evadne nordmanni, E. tergestina, Penilia avirostris, Podon leuckarti and P. polyphemoides, were investigated in the Inland Sea of Japan between April 1986 and May 1987. Gut content examination with SEM (scanning electron microscopy) revealed that feeding was largely limited to centric diatoms and a few exceptions of pennate diatoms and dinoflagellates. No animal remains were detected, and some unidentified materials were also found. Phytoplankton smaller than 35 m in size (cell diameter in centric diatoms and longest dimension in others) was found most frequently in the gut of cladocerans. The role of grazing of marine cladocerans in trophodynamic pathways of the pelagic realm is discussed.     

Feeding and cleaning mechanisms in the suspension feeding bivalve Mytilus edulis

Feeding and pseudofeces formation were studied in intact Mytilus edulis clearing suspensions of graphite particles, and the processes were compared with activities observed in mussels with a severed adductor muscle. Most particulate material in the stomach was present in the suspended state. Ingestion of particles in suspension could take place concurrently with the production of pseudofeces. Severing of the adductor muscle resulted in profuse secretion of mucus that gradually subsided to a constant low level. Addition of graphite particles at concentrations that did not cause mucus secretion in the intact mussels strongly stimulated secretion in the operated mussels, resulting in the accumulation of highly viscid, mucusparticle aggregates. These aggregates were mechanically stable, in contrast to the fragile pseudofeces. It is indicated that normal feeding depends upon hydromechanical mechanisms that produce highly concentrated suspensions of particles for ingestion, and that mucociliary mechanisms serve to clean the gills and other organs of the mantle cavity for excess particulate material. It is further indicated that intact mussels secrete mucus only in the amounts needed to consolidate excess particulate material, and that lesions affect the normal balance between particles in suspension and mucus secretion by enhancing the sensitivity of the mechanisms that control mucus secretion.