Draglines and Assessment of Fighting Ability in Cannibalistic Jumping Spiders

The frequency of injury and death during female-female aggression varies in the jumping spider genus Portia, with interactions being more violent (likely to end in death or injury of one of the combatants) in P. labiata (from Sri Lanka) than in another two species (P. fimbriata from Australia and P. schultzi from Kenya). To investigate the role of draglines in the assessment of fighting ability, two types of tests were carried out: 1) dragline discrimination and 2) mirror image response (Portia's reaction to mirror images is comparable to interaction with conspecific rivals). For both types of testing, triplets of equal-size conspecific females were used: one female (the test spider) was exposed to draglines of two equal-size conspecific females they had not encountered before (donor spiders). The fighting abilities of donor spiders were determined directly by staging intraspecific contests between them. In dragline-discrimination tests (spider placed in petri dish containing draglines from two conspecific females with different fighting ability), females of P. labiata, but not the other two species, avoided draglines of the superior fighter (i.e., they spent the majority of their time on draglines of donor spiders with lesser fighting ability). For mirror-image testing, the test spider was placed in a petri dish containing a mirror and draglines. Each test spider was tested on two successive days, with donor draglines in the two tests coming from conspecific females with different fighting ability. In these tests, females of P. labiata (but not the other two species) spent less time embracing (each spider pressing its forelegs, palps and front of body against the other spider) and more time in a part of the petri dish where view of the mirror was obstructed when on the draglines of donor spiders with greater fighting ability than when on the other conspecific's draglines. Findings from this study suggest that P. labiata females use signpost cues associated with draglines to assess the relative fighting abilities of unknown opponents.     

Determination of an Optimal Pitfall Trap Size for Sampling Spiders in a Western Australian Jarrah Forest

Pitfall trapping is a sampling technique extensively used to sample surface foraging invertebrates for biological diversity studies and ecological monitoring. To date, very few invertebrate studies have considered what trap size is optimal for sampling spiders. This study presents preliminary findings from a single short sampling period on the role of trap size in sampling spiders in a Western Australian Jarrah forest. Four different trap diameters (4.3, 7.0, 11.1 and 17.4 cm) were examined (4 trap sizes × 15 replicates = 60 traps). Two-way ANOVAs revealed no significant interaction effects between trap size or the spatial positioning of transects within the study site along which the pitfall traps were arranged. Post-hoc tests revealed abundance, family richness and species richness increased with increasing trap sizes for traps 7.0 cm. No significant differences in these dependent variables occurred between 4.3 and 7.0 cm traps, or for species richness between 11.1 and 17.4 cm traps. Determination of an optimal trap size was undertaken by bootstrapping and calculating species accumulation curves for increasing numbers of traps used. Three different criteria were considered: equivalent number of traps (15), standardized sampling intensity (cumulative trap circumference, approximately 207 cm) and standardized cumulative handling time (approximately 1 hour 17 minutes). The largest trap size (17.4 cm) was most efficient in terms of number of traps and trap circumference. For the same number of traps, it caught 19 species whereas all other trap sizes caught ten species. At the standardized circumference, it caught seven species whereas all other trap sizes caught five. For handling time, however, the two largest trap sizes (17.4 and 11.1 cm) were optimal. Both caught nine species whereas all other traps caught 相似文献   

Life table characteristics of Macrolophus caliginosus preying upon Tetranychus urticae

The life table characteristics of the polyphagous mirid Macrolophus caliginosus Wagner (Heteroptera: Miridae) preying on various stages of Tetranychus urticae Koch (Acari: Tetranychidae) with tomato as host plant were described at 22 °C. The following average parameters were obtained: Female longevity: 28.7 days; fecundity: 0.7 eggs/female/day; egg mortality: 2.6%; pre-oviposition period: 5.5 days; oviposition period: 18.1 days; post-oviposition period: 3.2 days; juvenile development time: 26.8 days; juvenile mortality: 34.9%; and sex ratio (/(+): 0.46. Life table parameters were estimated as net reproduction rate (R ₀): 6.15; intrinsic rate of increase (r _m): 0.031 day^–1; finite rate of increase (): 1.032; mean generation time (T _c): 58.17 days; and doubling time (T ₂) 22.2 days. The parameters obtained were in accordance with those reported for M. caliginosus fed on another mite species (T. turkestani Ugarov & Nikolski (Acari: Tetranychidae)). However, compared to the performance of M. caliginosus fed on common glasshouse insect pests, a diet consisting of only mites appeared to be inferior. However, being a voracious predator, M. caliginosus may be a valuable addition to existing methods of mite control.     

Proteolytic activities in body and faecal extracts of the storage mite, Acarus farris

Trypsin, chymotrypsin, cathepsins B and D, aminopeptidase and carboxypeptidases A and B were detected in body extracts of the storage mite Acarus farris (Oudemans) (Astigmata: Acaridae). Faeces-enriched medium exhibited higher (10-50-fold) specific protease activity rates than those measured with mite body extracts for trypsin, chymotrypsin and carboxypeptidases A and B, suggesting that they are involved in mite digestion. However, the activity of cathepsin B was only three-fold higher in faecal than in body extracts, indicating that its presence in the lumen of the digestive tract is low compared to that of serine proteases. The activity of aminopeptidases was higher in mite bodies, indicating that they might be membrane bound. Cathepsin D activity was only detected in body extracts, indicating that this enzyme is not a digestive protease in this species. Zymograms resolved three major bands of gelatinolytic activity, but at least one protease form was only present in body extracts. Protease inhibitors of different specificity were tested in vivo to establish their potential as control agents. The development of A. farris was significantly retarded when the immature stages were fed on artificial diet containing inhibitors of serine and cysteine proteases and aminopeptidases, whereas no such effect was found with inhibitors of aspartyl proteases and carboxypeptidases. Interestingly, the most significant effects on A. farris occurred when a combination of inhibitors targeting different enzyme classes was supplied mixed in the diet, suggesting a synergistic toxicity. Several plant lectins were also tested, but only wheat germ agglutinin and concanavalin-A affected development.     

Food source of riparian spiders analyzed by using stable isotope ratios

We analyzed the food source of riparian spiders in a middle reach of the Chikuma River, Japan, by using stable isotope ratios of carbon and nitrogen. The carbon and nitrogen isotope ratios of attached algae were higher than those of terrestrial plants, reflecting a large carbon isotope fractionation in terrestrial plants and a difference in nitrogen sources. The carbon isotope ratios of terrestrial insects were similar to those of the terrestrial plants, and the ratios of aquatic insects were scattered between those of the terrestrial plants and the attached algae. The carbon and nitrogen isotope ratios of spiders were intermediate between those of the terrestrial and aquatic insects. The two-source mixing model using the carbon isotope ratio showed that the web-building spiders utilized both the terrestrial and aquatic insects, with large contribution by the aquatic insects (54% on average with a maximum of 92% among spiders taxa collected in each zone), in the riparian area in a middle reach of the Chikuma River. The large contribution of the aquatic insects was often observed for the spiders collected near river channel (<5m) and for the horizontal web-building spiders collected across the riparian area. The relative contribution of the aquatic insects might be related with food availability (distance from river channel) and spiders food preference reflected in their web types (horizontal vs. vertical). Our results showed that organic materials produced in the river channel, in the riparian area, and in the terrestrial area surrounding the riparian area were mixed at the carnivorous trophic level of riparian spiders.     

Diet and Feeding Ecology of Woolly Monkeys in a Western Amazonian Rain Forest

I investigated the diet and feeding ecology of two social groups of woolly monkeys (Lagothrix lagotricha poeppigii) in Yasuní National Park, Ecuador between April 1995 and March 1996. Woolly monkeys in Yasuní were predominantly frugivorous, with fruits comprising ca. 77% of the yearly diet; the next most common food type in the diet was insect and other animal prey. The fruit diet of woolly monkeys in Yasuní is the most diverse yet recorded for any ateline primate, including spider monkeys (Ateles), which are often regarded as ripe fruit specialists: 208 distinct morphospecies of fruits were consumed by woolly monkeys either during the study or during several preceding months of pilot work. Nonetheless, close to one-third of the yearly diet came from just 3 plant genera—Inga, Ficus, and Spondias—and only 20 genera each contributed to 1% of the diet. For one study group, the proportion of ripe fruit in the diet each month was correlated with the habitat-wide availability of this resource, a pattern evidenced by several other ateline species. However, the relationship was not apparent in the second study group. The modal party size for feeding bouts on all food types was a single monkey, and, contrary to reports for other atelines, neither feeding party size nor the total number of feeding minutes that groups spent in food patches was well predicted by patch size. Both results highlight the independent nature of woolly monkey foraging. Given that woolly monkeys and closely-related spider monkeys focus so heavily on ripe fruits, their very different patterns of social organization are intriguing and raise the question of just how their ecological strategies differ. Two important differences appear to be in the use of animal prey and in the phytochemical composition of the ripe fruits that they consume: spider monkeys rarely forage for animal prey, and woolly monkeys seldom consume the lipid-rich fruits that are an important part of spider monkey diets.     

Demography of the cereal rust mite Abacarus hystrix (Acari: Eriophyoidea) on quack grass

Demography parameters of the cereal rust mite Abacarus hystrix (Nalepa) on quack grass were studied to investigate its potential capacity of population increase in conditions of initially low density. The experiment was maintained under laboratory conditions at a constant temperature of 19.5-20.5 degrees C and 94 +/- 1% RH. Life-history data were used to calculate duration of developmental stages, survival of adults and rates of population increase. A new method of estimation of age-dependent fecundity is proposed. On average, eggs required 7.98 (n = 33, 95% CI: 7.68-8.21) days to develop into adults. Life expectancy of females was longer than that of males (9.72 and 5.41 days, respectively). The mean sex ratio, expressed as the proportion of females, was 0.80 (n = 122, CI: 0.71-0.86). The reproductive output for females was age-dependent and daily egg production reached a peak (3.83 eggs/day, CI: 2.50-5.15) on the 5th day, and then decreased steeply. The net reproductive rate (R0) was 10.12 female progeny per female per generation, the generation time (T) was 11.31 days, the intrinsic rate of increase (r) was 0.20 female progeny per female per day, and the finite rate of increase (lambda) was 1.23 female progeny per day. These estimates showed that A. hystrix has a great potential capacity for rapid population increase when colonising new hosts and its density is low. Therefore, we conclude that the population of the cereal rust mite on quack grass may rapidly build up to very high densities and can be a reservoir population, which may easily disperse and infest other, including cultivated, grasses.     

Biology, ecology and control of the Penthaleus species complex (Acari: Penthaleidae)

Blue oat mites, Penthaleus spp. (Acari: Penthaleidae), are major agricultural pests in southern Australia and other parts of the world, attacking various pasture, vegetable and crop plants. Management of these mites has been complicated by the recent discovery of three cryptic pest species of Penthaleus, whereas prior research had assumed a single species. The taxonomy, population genetics, ecology, biology and control of the Penthaleus spp. complex are reviewed. Adult Penthaleus have a dark blue-black body approximately 1 mm in length, and eight red-orange legs. Within Australia, they are winter pests completing two or three generations a season, depending on conditions. The summer is passed as diapausing eggs, when long-distance dispersal is thought to occur. The Penthaleus spp. reproduce by thelytokous parthenogenesis, with populations comprising clones that differ ecologically. The three pest Penthaleus spp. differ markedly in their distributions, plant hosts, timing of diapause egg production and response to pesticides, highlighting the need to develop control strategies that consider each species separately. Chemicals are the main weapons used in current control programs, however research continues into alternative more sustainable management options. Host plant resistance, crop rotations, conservation of natural enemies, and improved timing of pesticide application would improve the management of these pests. The most cost-effective and environmentally acceptable means of control will result from the integration of these practices combined with the development of a simple field-based kit to distinguish the different mite species.     

The cDNA and genomic DNA organization of a novel toxin SHT-I from spider Ornithoctonus huwena

Spider venoms are complex mixtures of neurotoxicpeptides, proteins and low molecular mass organicmolecules. Their neurotoxic activity is due to the interac-tion of the venom components with cellular receptors, inparticular ion channels. Spider venoms have…     

Solution structure of Phrixotoxin 1, a specific peptide inhibitor of Kv4 potassium channels from the venom of the theraphosid spider Phrixotrichus auratus

Animal toxins block voltage-dependent potassium channels (Kv) either by occluding the conduction pore (pore blockers) or by modifying the channel gating properties (gating modifiers). Gating modifiers of Kv channels bind to four equivalent extracellular sites near the S3 and S4 segments, close to the voltage sensor. Phrixotoxins are gating modifiers that bind preferentially to the closed state of the channel and fold into the Inhibitory Cystine Knot structural motif. We have solved the solution structure of Phrixotoxin 1, a gating modifier of Kv4 potassium channels. Analysis of the molecular surface and the electrostatic anisotropy of Phrixotoxin 1 and of other toxins acting on voltage-dependent potassium channels allowed us to propose a toxin interacting surface that encompasses both the surface from which the dipole moment emerges and a neighboring hydrophobic surface rich in aromatic residues.