Toxicity of zinc,cadmium and copper to the shrimp Callianassa australiensis. I. Effects of individual metals

The acute toxicity of zinc, cadmium and copper to Callianassa australiensis (Dana) was evaluated in static tests. Each test lasted up to 14 d and LC₅₀ values were calculated for 4, 7, 10 and 14 d intervals. The toxicity of each metal increased with exposure time; thus the 4 d LC₅₀ values of 10.20, 6.33 and 1.03 mg l^-1 were considerably higher than the 14 d LC₅₀ values of 1.15, 0.49 and 0.19 mg l^-1 for zinc, cadmium and copper respectively. Toxicity curves reveal that none of the values were asymptotic, indicating that median lethal threshold concentrations were not reached for any of the metals. This suggests that 14 d is an insufficient time in which to complete meaningful, acute lethality tests for marine shrimps. Longer tests are necessary if lethal threshold concentrations are to be used with application factors to derive safe concentrations for the protection of C. australiensis.     

A review of the chemical ecology of the Cerambycidae (Coleoptera)

Summary. This review summarizes the literature related to the chemical ecology of the Cerambycidae and provides a brief overview of cerambycid biology, ecology, economic significance, and management. Beetles in the family Cerambycidae have assumed increasing prominence as pests of forest and shade trees, shrubs, and raw wood products, and as vectors of tree diseases. Exotic species associated with solid wood packing materials have been notable tree killers in North American urban and peri-urban forests. In forested ecosystems native species respond to disturbances such as fires and windstorms, and initiate the biodeterioration of woody tissue. Eggs are laid by females, on or through the bark surface of stem and branch tissue of moribund, recently killed or decomposing woody plants; larval cerambycids (roundheaded woodborers) typically feed in the phloem and later in the xylem. Females will also, in some cases, select living hosts, e.g. adult conifer and angiosperm trees, for oviposition. Research on the chemical ecology of over 70 species has revealed many examples of attractive kairomones (such as floral volatiles, smoke volatiles, trunk and leaf volatiles, and bark beetle pheromones), repellents and deterrents, oviposition stimulants, short- and long-range sex pheromones, and defensive substances. Emerging generalities are that attractants tend to be monoterpenoids and phenolic esters; oviposition stimulants are monoterpenoids and flavanoids; short-range sex pheromones are female-produced, methyl-branched cuticular hydrocarbons; and long-range sex pheromones are male-produced -hydroxy ketones and (,)-diols ranging in length from 6 to 10 carbons. The latter compounds appear to originate from glands in the male thorax; putative defensive substances originate from metasternal secretory pores or mandibular glands. In one unusual case, a flightless, subterranean female that attacks sugar cane produces a sex pheromone that is derived from the amino acid isoleucine. With significantly more than 35,000 species of Cerambycidae worldwide, these generalities will be subject to change as more species are examined. Addendum The authors would like to point out that the electronic version is more accurate than the printed version.     

Spatial distribution of main forest soil groups in Croatia as a function of basic pedogenetic factors

The model of spatial distribution of main forest soil groups in Croatia was developed as a function of basic pedogenetic factors: lithological substratum, macroclimate and relief. Used data about soil group, lithological substratum, terrain slope and aspect were collected on 1881 soil profiles. Macroclimatic data were estimated for each soil profile by spatial interpolation between meteorological stations. Feedforward neural networks were used as modelling tool. The final model has total classification correctness of 63.5% for training data set and 62.3% for independent test data set. The best result (86.4%) was achieved for fluvisols which are strongly spatially correlated with alluvial sediment in a flood plains. The worst result was achieved for luvisol (14.2%) which mainly comprised very old soils, probably developed under pedogenetic factors different from actual. The model was applied on entire Croatian territory aiming at construction of potential spatial distribution of main forest soils (without human impact), which was compared by the potential spatial distribution of major forest types modelled independently.     

Short-term and long-term facilitation of goose grazing by livestock in the Dutch Wadden Sea area

We studied the impact of livestock grazing on the distribution ofBranta bernicla bernicla (Dark-bellied Brent goose) in the Dutch Wadden Sea during spring. It was hypothesized that livestock facilitate short-term (within-season) grazing for geese as well as long-term (over years). Therefore we measured grazing pressure by geese in salt marsh and polder areas that were either grazed (spring-grazed) or ungrazed during spring (summer-grazed). Additionally, we carried out a preference experiment with captive geese to test the preference between spring-grazed and summer-grazed polder swards. We furthermore compared patterns of use by geese between long-term ungrazed and grazed salt marshes. In May, there is a difference in grazing pressure by geese between polder pastures that are grazed or ungrazed during spring. In this month, the ungrazed polder pastures are abandoned and the geese shift to either the grazed polder pastures or to the salt marsh. Vegetation in the polder that had been spring-grazed had a lower canopy height and a higher tiller density than summer-grazed vegetation. The captive geese in the preference experiment showed a clear preference for vegetation that had been spring-grazed by sheep over ungrazed vegetation. Goose grazing pressure was negatively correlated to canopy height, both on the polder and on the salt marsh. Within the plant communities dominated byFestuca rubra andPuccinellia maritima, marshes that were intensively grazed by livestock generally had higher grazing pressure by geese than long-term ungrazed or lightly grazed salt marshes.     

Influence of thermal history on the response of <Emphasis Type="Italic">Montastraea annularis</Emphasis> to short-term temperature exposure

Acclimation of reef corals to environmental conditions has been related to metabolic response at large geographic scales, but regional relationships have rarely been described. Physiological responses to temperature increases of Montastraea annularis (Ellis and Solander 1786) from an inner lagoon and an outer barrier reef in the Gulf of Honduras, southern Belize, were compared in May 2003. The hypothesis that inferred differences in thermal history would result in contrasting responses to elevated temperature was tested. Ambient seawater temperatures adjacent to corals at 4–5 m depth were measured every 15 min at inner lagoon and outer barrier reef collection sites for 1 year (June 2002–May 2003). Monthly averages and 3-day running averages (warmest period, July–October 2002) of daily maximum seawater temperatures were significantly higher (by ∼0.5°C) at inner lagoon reef compared to outer barrier reef sites. M. annularis photosynthesis (P) and respiration (R) rates were measured in respirometers at six temperatures between 29°C and 35°C approximately every hour, with repeated measurements over 3 h. P and R were significantly lower across most temperature treatments for samples collected from the inner lagoon compared to outer barrier reef. Both inner and outer reef M. annularis displayed an increase in P and R with increasing temperature between 29°C and 32°C, but above 32°C P and R sharply declined. P/R ratio versus temperature showed a significant difference between the elevations of the regression lines suggesting that M. annularis from the outer barrier reefs may have been more physiologically stressed than those from the inner lagoon reefs when exposed to acute temperature changes. These results emphasize that thermal stress must be considered within the context of acclimation temperature, and that short-term exposures may have physiologically important effects on this species.     

Evolution of coral reef fish<Emphasis Type="Italic"> Thalassoma</Emphasis> spp. (Labridae). 1. Molecular phylogeny and biogeography

Wrasses in the genus Thalassoma comprise 27 recognized species that occur predominantly on coral reefs and subtropical rocky reefs worldwide. The phylogenetic relationships for 26 species were examined based on two mitochondrial genes (cytochrome b and 16S rRNA) and one nuclear intron (the first intron of the ribosomal protein S7). Two closely related species, the bird-wrasses (Gomphosus varius Lacepède, 1801 and G. caerulaeus Lacepède, 1801), were also included in the analysis. These species grouped within the genus Thalassoma. Thalassoma newtoni (Osório, 1891) from Sao Tome, which is generally synonymized with the Atlantic/Mediterranean Thalassoma pavo (Linnaeus, 1758) appears to be a valid species. Using a molecular clock, the genus was estimated to have originally diverged 8–13 million years ago, with Thalassoma ballieui (Vaillant and Sauvage, 1875) from Hawaii and Thalassoma septemfasciata Scott, 1959 from Western Australia as the ancestral species. Approximately 5–10 million years ago, a sudden burst of speciation resulted in seven clades, which were resolved with the sequence data. The terminal Tethyan event and the closing of the Isthmus of Panama were probably the major historical factors shaping the evolution of species in the genus Thalassoma. These data on the spatio-temporal pattern of speciation in the Indo-Pacific indicate that peripheral species have been generated at various times throughout the history of the genus, and that none of the widespread species are relatively young. Thus, there is no clear support for centrifugal (youngest at the periphery) versus centripetal (oldest at the periphery) modes of generation of species, two theories which have been used to account for geographic gradients in species diversity.     

Choosing a home: how the scouts in a honey bee swarm perceive the completion of their group decision making

This study considers the mystery of how the scout bees in a honey bee swarm know when they have completed their group decision making regarding the swarm's new nest site. More specifically, we investigated how the scouts sense when it is appropriate for them to begin producing the worker piping signals that stimulate their swarm-mates to prepare for the flight to their new home. We tested two hypotheses: "consensus sensing," the scouts noting when all the bees performing waggle dances are advertising just one site; and "quorum sensing," the scouts noting when one site is being visited by a sufficiently large number of scouts. Our test involved monitoring four swarms as they discovered, recruited to, and chose between two nest boxes and their scouts started producing piping signals. We found that a consensus among the dancers was neither necessary nor sufficient for the start of worker piping, which indicates that the consensus sensing hypothesis is false. We also found that a buildup of 10–15 or more bees at one of the nest boxes was consistently associated with the start of worker piping, which indicates that the quorum sensing hypothesis may be true. In considering why the scout bees rely on reaching a quorum rather than a consensus as their cue of when to start preparing for liftoff, we suggest that quorum sensing may provide a better balance between accuracy and speed in decision making. In short, the bees appear to begin preparations for liftoff as soon as enough of the scout bees, but not all of them, have approved of one of the potential nest sites.

A nonparametric procedure for analyzing repeated measures of spatially correlated data

Many agricultural, biological, and environmental studies involve detecting temporal changes of a response variable, based on data observed at sampling sites in a spatial region and repeatedly over several time points. That is, data are repeated measures over time and are potentially correlated across space. The traditional repeated-measures analysis allows for time dependence but assumes that the observations at different sampling sites are mutually independent, which may not be suitable for field data that are correlated across space. In this paper, a nonparametric large-sample inference procedure is developed to assess the time effects while accounting for the spatial dependence using a block bootstrap. For illustration, the methodology is applied to describe the population changes of root-lesion nematodes over time in a production field in Wisconsin.     

Carbofuran induced impairment in the hypothalamo-neurohypophyseal-gonadal complex in the teleost,Channa punctalus (Bloch)

The effect of chronic exposure to carbofuran (4.5 ppm in static water) for six months on the gonadal histophysiology and hypothalamo-neurohypophyseal complex was studied in Channa punctatus. Experimental observations revealed significant inhibition of gonadal development with associated degenerative abnormalities as evidenced by ovarian and testicular histology and reduced gonadosomatic index. Degenerative changes in ovary were exihibited by stage I (oogonium) and stage II (immature/non-vitellogenic) oocytes as marked by perinuclear ooplasmic lysis, clumping and dissolution resulting in disintigration of nuclear material altogether attributed to complete degeneration of such oocytes. Testicular deleterious changes included degeneration of spermatogenic elements and necrosis of interstitial cells of Leydig. Correlative histophysiological changes were also observed in the pituitary gonadotrophs and hypothalamic, nucleus pre-opticus, neurons that were smaller, inactive and less in number with associated necrosis. Corresponding to the changes in nucleus pre-opticus neurons, significant inhibition of brain monoamine oxidase enzyme activity was also recorded in treated group. These observations suggest that carbofuran even at low concentration level under long-term exposure is capable of inducing retardation of gonadal development which might have been mediated through the impairment of the hypothalamo-neurohypophyseal-gonadal axis in this species.