Plant resistance, plant traits, and host plant choice of the leaf-folding sawfly on the arroyo willow

Abstract. 1. The hypotheses that genetic variation in host plant resistance of the arroyo willow affected leaf folder ( Phyllocolpa sp.) (Hymenoptera: Tenthredinidae) density and that genetic variation in shoot length and leaf length was correlated with resistance were tested.
2. Willows grown in pots and exposed to ovipojsition by the leaf folding sawfly in cages had significantly different densities among clones, indicating variation in resistance caused by genetic differences among conspecific host plants.
3. There was a general correspondence between leaf folder density on potted cuttings and on the plants in the field that were the sources of cuttings.
4. In behavioural choice experiments, susceptible clones (with highest leaf fold densities) had the highest oviposition activity of female leaf folders compared to clones that were resistant to the leaf folder.
5. Clones differed significantly in shoot length and leaf length among clones grown in pots, among clones in the field, and between shoots with galls and shoots without galls on clones in the field.
6. Leaf folder density was significantly positively correlated with mean shoot length on field clones in 1985 and 1986, but was not correlated with leaf length, although leaf length and shoot length were correlated.
7. Leaf length variation among willow clones accounted for a significant portion of the variation in resistance of potted willows, but shoot length was unimportant.     

Notes on the use of wood refugia by Physella heterostropha (say) in a thermally disturbed swamp

Physella heterostropha size distributions and densities were measured in Pen Branch delta, a thermally altered swamp of the Savannah River, South Carolina. During cessation of thermal input, measurements were taken in a highly impacted area and more natural area. Of the three substrates sampled, logs, small woody material and benthos, snail density was highest on small pieces of submerged wood and < 20% of the snails on logs were out of the water. Following resumption of thermal input, snail density was four times higher on logs than previously measured. Snails responded to elevated water temperatures by congregating in a narrow band slightly above the water. Snail size did not appear to affect their response. However, the thermal history of the snails influenced their behaviour and survival rates. Logs may be a potential refuge for snails when water temperature are greater greater than 38°C. However, our results indicate that long-term survival in this manner may be impossible.     

Effects of weather and feeding on body temperature and activity in the snake Masticophis flagellum

1. 1.|Body temperature (T_b) and activity of the snake Masticophis flagellum were studied by radiotelemetry in an outdoor enclosure.

2. 2.|Mean diurnal T_b varied little over a wide range of weather conditions, but weather variation was accompanied by major changes in sun exposure and in the timing and duration of activity.

3. 3.|Recently fed snakes reduced activity and exhibited neither a thermophilic response nor increased precision of thermoregulation compared to fasting snakes.

兴安落叶松结实规律与长短枝习性的关系

1987年5月,大兴安岭林区发生的特大森林火灾,实属世界罕见,火灾面积达1.0×10~6ha 多。大量的火烧迹地亟待更新、无论是人工更新还是人工促进天然更新,其中关键的问题之一是种子的来源,在大兴安岭地区,兴     

The effect of insecticides on the distribution of foracing parasitoids,Diaeretiella rapae [Hym.: Braconidae] on plants

Foraging aphid parasitoids,Diaeretiella rapae M'Intosh, were exposed to sublethal doses of the insecticides pirimicarb, permethrin and malathion on brusslls sprouts plants. Observations on wasp distribution over time revealed that wasps spent less time on sprayed plants, relative to controls and, while on these plants, tended to concentrate activity on unsprayed surfaces. For permethrin and malathion, pesticide residues reversed the stereotypic upward foraging pattern of the wasp. Negative consequences of sublethal pesticide doses for parasitoid foraging efficiency are discussed.      

Muscle development in the tambaqui, an important Amazonian food fish

Eggs of the tambaqui Colossoma macropomum were incubated at 28 and 31) C. Somitogenesis started shortly after the formation of the neural plate and notochord. New somites were added at the rate of one every 13 min at 28) C and one every 11 min at 31) C. Myogenesis started in the most rostral myotomes at the 9-somite stage and proceeded in a caudal direction. Mononuclear myotubes with the morphological characteristic of muscle pioneer cells were observed lateral to the notochord. The majority of myotubes were formed from the fusion of 3–6 spindle-shaped myoblasts. Myofibril synthesis started soon after cell fusion at the periphery of myotubes. Close membrane contacts and 'gap'-type junctions were observed between myotubes, immature muscle fibres and at the inter-somite boundary, suggesting that the cells were electrically coupled. Embryos exhibited rhythmic movements at the 20-somite stage, and hatched at the 29–30-somite stage 15–18 h post-fertilisation (PFT) at 28° C and 11 h PFT at 31° C. Larvae hatched at a comparatively early stage of development prior to the completion of somitogenesis and the formation of eye pigment, pectoral fins and jaws. The myotomes comprised a single superficial layer of well-differentiated muscle fibres which contained abundant mitochondria, overlying an inner core of myotubes (presumptive white muscle layer). Differentiation and growth during the larval stages was extremely rapid, and the juvenile stage was reached after little more than 6 days at 28° C.     

Deficit of didocosahexaenoyl phospholipid in the eyes of larval sea bass fed an essential fatty acid deficient diet

Larval sea bass Dicentrarchus labrax of 27 days old were reared on Artemia enriched with Super Selco©, Tuna Orbital Oil or Yeast. The first diet is commonly used in mariculture for larval rearing, the second diet was designed to deliver an optimal docosahexaenoic acid (22: 6n-3) to eicosapentaenoic acid (20: 5n-3) ratio, and the third diet was deficient in docosahexaenoic acid (22: 6n-3). The eyes of these larvae were analysed after 28 days and the molecular species of the three main phospholipid classes, phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylserine (PS) determined. Eyes from larvae fed Artemia enriched with yeast showed large decreases in molecular species containing 22: 6n-3 compared to those supplemented with tuna orbital oil, most notably in 16: 0/22: 6n-3 PC which fell from 10.6 to 0.4%, in 22: 6n-3/22: 6n-3 and 18: 1/22: 6n-3 PE which fell from 29.6 to 0.3% and from 10.8 to 1.1% respectively, and in 22: 6n-3/22: 6n-3 PS which fell from 34.3 to 1.7%. Molecular species containing all other fatty acids, and especially 20: 5n-3, were elevated in eyes from the yeast-supplemented fish. In larvae fed Artemia enriched with Super Selco, amounts of eye 22: 6n-3/22: 6n-3 phospholipid were slightly lower in all three phospholipid classes compared to eyes from the tuna orbital oil-supplemented larvae. There was also a trend of decreased saturated fatty acid/22: 6n-3 and monounsaturated fatty acid/22: 6n-3 molecular species in all classes from the Super Selco-supplemented fish, the deficits being made up with molecular species containing 20: 5n-3 and 22: 5n-3. These results are discussed in relation to larval viability with particular respect to visual function.     

Behaviour in usurpers and late joiners ofPolistes biglumis bimaculatus (Hymenoptera,Vespidae)

Summary During the late pre-emergence phase, a foundress of the paper waspPolistes biglumis bimaculatus may be expelled by a conspecific female from her own nest (usurpation) or, less frequently, joined by another female of the same species (late association). The behaviour of femalePolistes biglumis bimaculatus, when usurping a conspecific colony or joining another foundress, is compared with that of foundresses on non-usurped colonies. The most conspicous difference is the intense abdomen stroking behaviour the usurper performs over the comb surface on the first days after usurpation. As observed in otherPolistes species, once usurpers and joiners arrive on a strange nest they will destroy most of the immature brood of the previous nest owner. Although host workers are not aggressive towards the intruder females, reproductive success of usurpers and joiners is low compared with that of legitimate foundresses. The same behaviours observed on usurped colonies are found in the obligate social parasites ofPolistes. These behaviours are therefore discussed in the context of the evolution of intra- and inter-specific parasitism.     

Behavioural evidence for colour vision in stomatopod crustaceans

If an organism can be taught to respond in a particular way to a wavelength of light, irrespective of that light's intensity, then it must be able to perceive the colour of the stimulus. No marine invertebrate has yet been shown to have colour vision. Stomatopod crustaceans (mantis shrimps) are colourful animals and their eyes have many adaptations which indicate that they are capable of such spectral analysis. We adopted an associative learning paradigm to attempt to demonstrate colour vision. Stomatopods readily learnt to choose some colours from arrays of greys, even when the correct choice colours were darker than the ones they had been trained to. Possible mechanisms underlying colour vision in these animals, and their ecological significance are discussed. A simple model is presented which may help interpret the complex-stomatopod colour vision system and explain some of the learning anomalies.Abbreviations ND neutral density - OD optical density - R8 Retinular cell 8 - R1–7 Retinular cells 1–7 - R1D Distally placed R1–7 retinular cells in mid-band row 1 - e.g. R1P Proximally placed R1–7 retinular cells in mid-band row 1 - D/P Estimate of chromatic signal ratio     

Effects of social conditions on Juvenile Hormone mediated reproductive development in Bombus terrestris workers

Abstract. During the annual life cycle of the bumble bee Bombus terrestris (L.) colony, there is a stage characterized by worker reproduction in the presence of the queen. It has been proposed that this is a result of a decrease in queen inhibition. This hypothesis was examined by studying the effects of queens taken from colonies at different stages of development on several aspects of worker physiology and behaviour: rates of Juvenile Hormone (JH) release in vitro , ovary development, and behaviour associated with reproduction. After optimizing and validating the radiochemical assay for JH release for bumble bee workers, we found that queenless workers had significantly more developed ovaries and higher rates of release of JH than did queenright workers, confirming and extending previous findings that suggest that bumblebee ovarian development is under JH control. Mated queens, separated from their colony and brood, can have the same inhibitory effect on the reproductive development of callow workers. In contrast, workers confined with virgin queens or in queenless groups demonstrated a significantly higher rate of release of JH, overt aggression and threatening behaviours. However, there were no differences in rates of release of JH between workers confined in groups in the laboratory with queens taken from colonies either before or after the onset of worker reproduction. Furthermore, overt aggression and threatening behaviours were similar and low in both types of groups. These results gave no support to the hypothesis that a decrease in queen inhibition is associated with the onset of worker reproduction. We also show that young workers reared in colonies either before or after worker reproduction occurs, or in queenless colonies, all demonstrated similar, low rates of release of JH. These results suggest that older workers may inhibit the corpora allata of younger workers in queenless colonies.