Role of plant phenology in mediating interactions between two biological control agents for spotted knapweed

The role of spotted knapweed phenology on the attack rate of two seed-head insects Urophora affinis and Larinus minutus was assessed in a series of field studies at four study sites in south-eastern British Columbia, Canada. Slow or later developing knapweed plants had more seed heads that contained only single or multiple U. affinis whereas early or faster developing plants had more seed heads containing L. minutus alone or in combination with U. affinis. L. minutus did not distinguish between seed heads with or without U. affinis larvae when laying eggs. However, seed heads with multiple U. affinis present, produced fewer L. minutus adults than expected. The probability of single or multiple U. affinis galls being present increased with seed-head diameter but was not affected by seed-head height. Attack by L. minutus increased with seed-head diameters >5 mm and was lower at plant heights above 50 cm. These results demonstrate two mechanisms that enable U. affinis to successfully coexist with L. minutus: differences between the species in their response to the developmental phenology of knapweed heads, and increased survivorship of U. affinis in heads with multiple U. affinis galls through niche interference competition. These mechanisms provide a possible explanation for the persistence of U. affinis populations on spotted knapweed, in spite of high levels of within seed-head mortality that have been observed with increasing L. minutus populations.     

Electric interactions through chirping behavior in the weakly electric fish, Apteronotus leptorhynchus

The weakly electric fish Apteronotus leptorhynchus produces wave-like electric organ discharges distinguished by a high degree of regularity. Transient amplitude and frequency modulations (“chirps”) can be evoked in males by stimulation with the electric field of a conspecific. During these interactions, the males examined in this study produced six types of chirps, including two novel ones. Stimulation of a test fish with a conspecific at various distances showed that two electrically interacting fish must be within 10 cm of each other to evoke chirping behavior in the neighboring fish. The chirp rate of all but one chirp type elicited by the neighboring fish was found to be negatively correlated with the absolute value of the frequency difference between the two interacting fish, but independent of the sign of this difference. Correlation analysis of the instantaneous rates of chirp occurrence revealed two modes of interactions characterized by reciprocal stimulation and reciprocal inhibition. Further analysis of the temporal relationship between the chirps generated by the two fish during electric interactions showed that the chirps generated by one individual follow the chirps of the other with a short latency of approximately 500–1000 ms. We hypothesize that this “echo response” serves a communicatory function.     

Electrical stimulation of the preoptic area in Eigenmannia: evoked interruptions in the electric organ discharge

The functional role of the basal forebrain and preoptic regions in modulating the normally regular electric organ discharge was determined by focal brain stimulation in the weakly electric fish, Eigenmannia. The rostral preoptic area, which is connected with the diencephalic prepacemaker nucleus, was examined physiologically by electrical stimulation in a curarized fish. Electrical stimulation of the most rostral region of the preoptic area with trains of relatively low intensity current elicits discrete bursts of electric organ discharge interruptions in contrast to other forebrain loci. These responses were observed primarily as after-responses following the termination of the stimulus train and were relatively immune to variations in the stimulus parameters. As the duration and rate of these preoptic-evoked bursts of electric organ discharge interruptions (approximately 100 ms at 2 per s) are similar to duration and rate of natural interruptions, it is proposed that these bursts might be precursors to natural interruptions. These data suggest that the preoptic area, consistent with its role in controlling reproductive behaviors in vertebrates, may be influencing the occurrence of electric organ discharge courtship signals by either direct actions on the prepacemaker nucleus or through other regions that are connected with the diencephalic prepacemaker nucleus. Accepted: 16 October 1999     

Mauthner cell-evoked synaptic actions on pacemaker medullary neurons of a weakly electric fish

The present study was designed to examine the synaptic events in neurons of the pacemaker nucleus of Gymnotus carapo during the increase in rate of the electric organ discharge following activation of Mauthner cells. Pacemaker and relay cells were investigated using intracellular recordings which were performed under two different conditions: (1) with the pacemaker nucleus spontaneously discharging and (2) after its activity was abolished by anesthesia. Mauthner axon activation induced an increase in the rate of pacemaker cell discharges. This response was accompanied by an increase in the slope of the pacemaker potential (up to 110%) and a depolarization of these cells. The discharges of relay cells followed one to one those of pacemaker cells. In contrast to that observed in pacemaker cells, only brief depolarizing antidromic effects could be evoked in relay cells after Mauthner axon activation. In quiescent pacemaker cells, Mauthner cell activation induced a prolonged (up to 500 ms) depolarizing potential with an average amplitude of 1.92 ± 0.82 mV; its latency was 4.43 ± 1.14 ms. Our data indicate that, within the pacemaker nucleus, the population of pacemaker cells is the only target for Mauthner cell-evoked, short-latency excitatory synaptic actions. Accepted: 1 March 1997     

Delay-Dependent Response in Weakly Electric Fish under Closed-Loop Pulse Stimulation

In this paper, we apply a real time activity-dependent protocol to study how freely swimming weakly electric fish produce and process the timing of their own electric signals. Specifically, we address this study in the elephant fish, Gnathonemus petersii, an animal that uses weak discharges to locate obstacles or food while navigating, as well as for electro-communication with conspecifics. To investigate how the inter pulse intervals vary in response to external stimuli, we compare the response to a simple closed-loop stimulation protocol and the signals generated without electrical stimulation. The activity-dependent stimulation protocol explores different stimulus delivery delays relative to the fish’s own electric discharges. We show that there is a critical time delay in this closed-loop interaction, as the largest changes in inter pulse intervals occur when the stimulation delay is below 100 ms. We also discuss the implications of these findings in the context of information processing in weakly electric fish.     

烟田中静电喷雾和电动喷雾下噻虫嗪的防效及对昆虫群落的影响

【目的】探明静电喷雾与电动喷雾对噻虫嗪防治害虫效果及烟田昆虫群落的影响,为静电喷雾在烟草上的推广应用提供理论依据。【方法】利用静电喷雾与电动喷雾法喷施0.66 g·L~(-1)25%噻虫嗪水分散粒剂,施药1、3、7 d后,测定2种方法对烟蚜与斜纹夜蛾的防治效果、在烟株与土壤中的沉积以及对昆虫群落的影响。【结果】喷施25%噻虫嗪水分散粒剂1、3、7 d后,静电喷雾对烟蚜和斜纹夜蛾的防治效果均显著高于电动喷雾的防治效果,且防治效果均随时间的推移而升高。噻虫嗪在静电喷雾处理区烟叶上的沉积量高于电动喷雾处理区烟叶上的沉积量,而在静电喷雾处理区土壤中的沉积量低于电动喷雾处理区土壤中的沉积量,且都随时间的推移而降低。静电喷雾与电动喷雾均引起烟田昆虫群落的变化,静电喷雾引起的害虫和中性昆虫的数量变化大于电动喷雾,但天敌昆虫的数量变化小于电动喷雾,且静电喷雾区烟田的物种丰富度明显高于电动喷雾区,可见静电喷雾施药对烟田昆虫群落的影响小于电动喷雾施药。静电喷雾的S_t/S_i与S_n/S_p比值明显高于电动喷雾,说明静电喷雾烟田中昆虫群落稳定性高于电动喷雾烟田中昆虫群落的稳定性。【结论】相比电动喷雾,静电喷雾能够提高噻虫嗪在烟叶上的沉积量,从而提高噻虫嗪对害虫的防治效果,同时减少噻虫嗪在土壤中的沉积量,提高噻虫嗪的生态安全性,因此,静电喷雾在烟草病虫害防治上具有较好的应用前景。     

Direct and indirect effects of predation by Saduria entomon (Isopoda) on the size-structure of Monoporeia affinis (Amphipoda)

We performed a 6-month laboratory experiment to investigate the direct and indirect effects of predation by the benthic invertebrate predator Saduria entomon on the growth and survival of Monopreia affinis prey individuals in different age-cohorts at low and high prey densities. The experimental results were compared with changes of growth and abundance in corresponding age-cohorts of M. affinis at sites with different S. entomon and M. affinis densities in the deep sublittoral zone of the Bothnian Sea during the same year. In the experiment, the presence of S. entomon reduced growth rate of M. affinis in the 1-year and 2-year age-cohorts at low amphipod density. Increased refuge use by M. affinis, expressed as a decrease in swimming activity in the presence of S. entomon, is suggested to have reduced feeding rate and therefore growth of the amphipods. The recruitment of M. affinis offspring was reduced in presence of S. entomon. In the field, the growth rate of amphipods in the 1-year cohort increased with increasing S. entomon density at low amphipod density. We found no corresponding increase of M. affinis growth in the 2-year cohort. The positive effect on 1-year amphipod growth indicated that predation reduced intra-cohort competition of M. affinis and increased growth of surviving prey at high predator density. In both the experiment and the field data we found indications of size-selective predation on smaller M. affinis specimens. This was because of the changed ratio between number of individuals in the juvenile age-cohorts and lower recruitment of amphipod offspring connected to S. entomon density. The experimental results and field data suggest that predation by S. entomon may have both direct and indirect effects on the size-structure of M. affinis populations. Received: 22 June 1998 / Accepted: 15 March 1999     

Vertical, lateral and longitudinal movement of zooplankton in a large river

1. The spatial distribution and movement patterns of zooplankton in large rivers are little known compared with those in lake environments. We conducted a series of studies in the Ohio River (U.S.A.) during the low flow period to assess diel vertical (DVM), longitudinal and lateral movement of crustacean zooplankton. 2. The dominant large zooplankter, the copepod Eurytemora affinis, showed a consistent vertical migration pattern of daytime ascent and night‐time descent during all sampling periods – the reverse of the most common migratory pattern of zooplankton in lakes. The cladoceran Bosmina migrated in a similar way in two of the three sampling periods. Surveys taken longitudinally in the river showed similar trends for both taxa. 3. During the lateral surveys, E. affinis was significantly more abundant in the shallow littoral zone during the night than in the daytime. The combination of vertical and lateral movement patterns along with the diel distribution of zooplanktivorous fish suggest that these movements are a predator‐avoidance mechanism. 4. Sampling programmes in large rivers should consider that larger zooplankton such as E. affinis may not be randomly distributed in the river channel and behaviours such as diel vertical migration may be just as evident in river habitats as in lakes.     

Monopolar electric discharges of the catfish <Emphasis Type="Italic">Parasilurus asotus</Emphasis> (Siluridae,Siluriformes)

Electric discharges in the catfish Parasilurus asotus are registered for the first time. The discharges are monopolar pulses of a 50–300 ms duration which corresponds to the frequency characteristics of ampoules of electroreceptors in these catfish. Electric generation is discovered only upon the aggressive-defensive behavior of not less than two species. In solitary fish no discharges were observed neither at prolonged continuous registration (longer than 24 h each) nor at mechanical stimulation. The hypothesis is discussed of a potential mechanism of active (under use of their own electric discharges) monitoring of water conductivity with a relative sensitivity on the order of 0.0002%. This hypothesis may be applied to an explanation of anomalous group behavior of these catfish before earthquakes.     

Comparative spring distribution of zooplankton in three macrotidal European estuaries

The zooplankton of three european estuaries (Ems, Gironde and Westerschelde) was investigated during spring 1992 by means of samples taken along the salinity gradient. The three estuaries are comparable in terms of total area, flushing time and salinity gradient but differ by their level of eutrophication (highest in the Westerschelde), suspended matter concentration (highest in the Gironde) and potential phytoplankton production (highest in the Ems). Copepods and meroplankton dominated the zooplankton in the three estuaries. The dominant copepod species were Eurytemora affinis and Acartia bifilosa. The distribution of E. affinis along the salinity gradient differed between the estuaries. Peaks of abundance were observed at 0 PSU in the Gironde, 6 PSU in the Ems and 9 PSU in the Westerschelde. The downstream shift of the population in the Westerschelde was likely due to anoxic conditions occurring in the oligohaline zone. In the Gironde the downstream distribution of E. affinis was limited by the very high suspended matter concentration found in the maximum turbidity zone. Whatever the estuary, the parameters of the population of E. affinis and maximum abundance values were similar. However, the influence of the better quality of the available food was suggested in the Ems where individual dry weights and egg production were higher than in the two other estuaries. The influence of a good quality of food in the Ems was confirmed by the development of a large population of Acartia bifilosa (as abundant as E. affinis) and highest values of adult individual weights.The meroplankton (essentially Polychaete and cirripede larvae) was much more developed in the Ems than in the Westerschelde and Gironde. This was likely due to the large extent of mudflats and hard substrates in the Ems favouring adult settlement and hence the number of larvae locally produced.     

Length‐weight relationships of four fish species from Visakhapatnam coast,India

Length‐weight relationships (LWRs) were determined for 4 deep water fish species from Visakhapatnam coast, India. Specimens were collected fortnightly between December 2013 and November 2015 from commercial trawls at Visakhapatnam fish landing centre (16.98°N–20.2°N, Long.82.19°–86.53°E). Individuals were captured between 100 and 300 m depth with shrimp trawl net (head rope length: 37–46 m and cod end mesh size: 30–40 mm). Total length (TL) (nearest to 0.1 cm) and body weights (nearest to 0.1 g) were taken each individual. All LWRs were significant with r² values ranged from 0.958 for Uranoscopus bicinctus Temminkc & Schlegel, 1843 to 0.983 for Uranoscopus chinensis Guichenot, 1882 and “b” values ranged from 2.832 for U. bicinctus to 3. 402 Synodus indicus (Day, 1873).This study provides a new maximum length data for three species (Uranoscopus bicinctus Temminkc & Schlegel, 1843; Uranoscopus chinensis Guichenot, 1882 and Uranoscopus marmoratus Cuvier, 1829).     

Intraspecific agonistic interactions in freely swimming mormyrid fish, Marcusenius macrolepidotus (South African form)

South African bulldogs (Marcusenius macrolepidotus, Mormyridae) generate brief (less than 1 ms) electric organ discharges (EODs), separated by much longer and highly variable inter-discharge intervals (IDIs). The diurnal and nocturnal overt behaviour and electrical activity were studied under various conditions: in isolated fish, in pairs of fish, and in a group of four fish that were kept in a "natural" large aquarium. EODs from up to four individuals were recorded simultaneously and identified. While resting during the day, isolated fish showed a broad inter-individual variability of IDI patterns, with distribution histogram modes ranging from 85.7 ms to 325.8 ms. When foraging during the day, IDI modes were shorter and less variable (36.3–48.3 ms). Behaviour patterns displayed during nocturnal agonistic encounters were retreating, parallel swimming, anti-parallel display, attack, and fleeing/chasing. High-discharge-rate (HD) displays were observed at several stages of these encounters, for example, during anti-parallel display (a period of low overt motor activity), or following attacks. IDI durations as short as 11 ms occurred during HD displays, which followed low-rate inter-HD activity almost without transition. IDI distribution histogram modes when fish showed anti-parallel display were 15.4 ms and 24.8 ms, and 30.0 ms during nocturnal non-agonistic interactions. No overt fighting was observed once a dominance relationship was established. In a large aquarium, an approaching dominant male evoked a simultaneous discharge arrest in a group of three subdominant males. Electronic Publication     

Analysis of the jamming avoidance response in the electric fish Gymnotus carapo

The electric fish Gymnotus carapo emits brief (4 ms) electric pulses separated by much longer intervals of high regularity (coefficient of variation 0.01–0.02). Two main changes in the firing patterns of electric organ discharge were observed when two fish were placed together. (1) All fish pairs showed an increase in the frequency difference between the two fish, in comparison with the value observed in isolated fish, prior to the interaction. This change increased the number of beats per second between both discharge trains, i.e., the number of times per second that the higher rate discharge sweeps the lower rate one when displayed on an oscilloscope. (2) When the sweeping velocity fell below 2–3 sweeps/s, transient frequency increases were also observed in the electric organ discharge of the higher rate fish when they were about to discharge simultaneously. The contribution to jamming avoidance of these two changes was analyzed by comparing recordings of behavioral interactions with simulations produced by a computational model. The jamming effect of the firing of a conspecific located in the same tank was evaluated by counting the number of coincidences between both trains (occurrence of discharges of the two fish within 2 ms of one another). The number of coincidences was evaluated as a function of the sweeping velocity in both simulations (with and without transient frequency increases) and real fish. As the sweeping velocity increased, single coincidences increased slightly in simulations without transient frequency increases, whereas the successive coincidences (coincidences repeated in successive discharges) decreased abruptly. The simulation including transient frequency increases eliminated the successive coincidences and decreased the single ones. Only when the sweeping velocity was less than 2–3 sweeps/s, did transient frequency increases improve the coincidence-avoiding performance of the simulation. The number of coincidences observed in natural behavioral interactions for the different sweeping velocities coincided with the distributions obtained with the simulations. As successive coincidences are known to be more detrimental for electrolocation than single ones, the increase in the sweeping velocity may be considered a jamming avoidance strategy in Gymnotus carapo, in addition to the already described transient frequency increases. Received: 2 June 1998 / Accepted in revised form: 18 November 1998     

Electric discharges and electrogenesis peculiarity in two African upside-down catfishes, <Emphasis Type="Italic">Synodontis caudovittatus</Emphasis> and <Emphasis Type="Italic">S. eupterus</Emphasis> (Mochokidae,Siluriformes)

The paper reports spontaneous generation of weak electric discharges with an amplitude of 0.4–1.0 mV and a frequency of 3–9 min^–1 by solitary Synodontis caudovittatus fish. When fish individuals were tested in pairs, their aggressive–defense interactions were associated with an increase in the amplitude of the discharges (up to 30–45 mV) compared to the discharges of individual fish, while the duration of the pulses increased up to 20–25 ms due to the prolongation of the second phase. In S. eupterus, electric activity was recorded only in the course of aggression–defense interactions, while spontaneous generation of discharges was not observed at all. The paper discusses the different aspects of electrocummunication between the catfish including the role of the reversion of polarity of the merged summated discharges with increased duration.     

Life histories ofNeomysis integer,and its copepod prey,Eurytemora affinis,in a eutrophic and brackish shallow lake

Data was collected on the population structure and fecundity of the mysidNeomysis integer and the calanoid copepodEurytemora affinis in Hickling Broad, a shallow and eutrophic brackish lake, over a two-year period 1988/89. Standing biomass and production rate estimates were made using estimates of size-specific dry weights and development times obtained from laboratory measurements, field observations and information found in the literature. Both mysid and copepod are capable of a rapid response to favourable conditions and have high rates of birth, growth and production.E. affinis reproduces throughout the year with an estimated annual (May 1988–May 1989) production of 20 g dry wt m⁻². Copepod standing biomass was less in 1989 compared with 1988 owing to an overall reduction in copepod body-size and a reduction of size at maturity. There was a suggestion from the data that this was caused by predation from a greater number of large (>9 mm body-length) mysids in 1989 compared with 1988.N. integer is highly seasonal in its growth with distinct peaks of recruitment in May and July. Annual (May 1988–May 1989) production of the mysid was estimated as 5.8 g dry wt m⁻². AlthoughE. affinis is the only available prey ofN. integer in the lake, the mysid population appears independent of changes in that of the copepod and probably avoids negative predator-prey feedback mechanisms owing to an ability to feed on epiphytic algae.     

Establishment and Dispersal ofUrophora affinis(Diptera: Tephritidae) andMetzneria paucipunctella(Lepidoptera: Gelechiidae) in Southwestern Virginia

Two European gall-producing insects,Urophora affinisFrfld. (Diptera: Tephritidae) andMetzneria paucipunctella(Zeller) (Lepidoptera: Gelechiidae) were introduced into Virginia in 1986 for biological control of spotted knapweed (Centaurea maculosaLam.). Adults ofU. affinis(n = 2625) andM. paucipunctella(n = 450) were released at two sites in Montgomery County, Virginia, and their populations were monitored yearly by dissecting spotted knapweed flower heads. Beginning in 1992, knapweed samples collected at various distances from the release sites were checked for dispersal.U. affinisis well established and is spreading slowly. The number of larvae per flower head and the seed numbers are inversely related as plants with the greatest number of larvae per spotted knapweed head had the lowest number of seeds. Knapweed density has declined at one of the release sites which had the highest rate of infestation byU. affinis.Establishment of the moth,M. paucipunctella,is less certain as it has been recovered at a very low level from only one site.     

Is the copepod egg production in a highly turbid estuary (the Gironde, France) a function of the biochemical composition of seston?

The influence of the biochemical composition of particles originating from surface waters of the Gironde estuary on egg production rates of Eurytemora affinis zooplanktonic population was studied. In the high turbidity zone, suspended particulate matter had a low nutritional quality because the easily available organic fraction represented less than 15% of the overall particulate organic matter. In waters located seaward of the high turbidity zone, a slight increase in nutritional quality was observed. As a result, the sum of easily extractable organic macromolecules represented 15 to 33% of the overall particulate organic matter. The present study suggests that the low egg-production rate of Eurytemora affinis, occurring in the high turbidity zone, results from combined effects of temperature and bad feeding conditions in the area. Low copepod production can be explained by little phytoplankton growth due to light limitation and, therefore, restricted food availability, as well as difficulties in food selection, non-living particle may being dominant.     

Electric organ discharges of the gymnotiform fishes: III. Brachyhypopomus

We measured and mapped the electric fields produced by three species of neotropical electric fish of the genus Brachyhypopomus (Gymnotiformes, Rham phichthyoidea, Hypopomidae), formerly Hypopomus. These species produce biphasic pulsed discharges from myogenic electric organs. Spatio-temporal false-color maps of the electric organ discharges measured on the skin show that the electric field is not a simple dipole in Brachyhypopomus. Instead, the dipole center moves rostro-caudally during the 1st phase (P1) of the electric organ discharge, and is stationary during the 2nd phase (P2). Except at the head and tip of tail, electric field lines rotate in the lateral and dorso-ventral planes. Rostro-caudal differences in field amplitude, field lines, and spatial stability suggest that different parts of the electric organ have undergone selection for different functions; the rostral portions seem specialized for electrosensory processing, whereas the caudal portions show adaptations for d.c. signal balancing and mate attraction as well. Computer animations of the electric field images described in this paper are available on web sites http://www.bbb.caltech.edu/ElectricFish or http://www.fiu.edu/∼stoddard/electricfish.html. Accepted: 22 September 1998     

Electroporative deformation of salt filled lipid vesicles

Membrane electroporation, vesicle shape deformation and aggregation of small, NaCl-filled lipid vesicles (of radius a = 50 nm) in DC electric fields was characterized using conductometric and turbidimetrical data. At pulse durations t_E≤ 55 ± 5 ms the increase in the conductivity of the vesicle suspension is due to the field-induced efflux of electrolyte through membrane electropores. Membrane electroporation and Maxwell stress on the vesicle membrane lead to vesicle elongation concomitant with small volume reduction (up to 0.6% in an electric field of E = 1 MV m^–1). At t_E > 55 ± 5 ms, further increases in the conductivity and the optical density suggest electroaggregation and electrofusion of vesicles. The conductivity changes after the electric pulse termination reflect salt ion efflux through slowly resealing electropores. The analysis of the volume reduction kinetics yields the bending rigidity κ = (4.1 ± 0.3) ⋅ 10^–20 J of the vesicle membrane. If the flow of Na⁺ and Cl^– ions from the vesicle interior is treated in terms of Hagen-Poiseuille's equation, the number of permeable electropores is N = 39 per vesicle with mean pore radius r_p = 0.85 ± 0.05 nm at E = 1 MVm^–1 and t_E≤ 55 ± 5 ms. The turbidimetric and conductometric data suggest that small lipid vesicles (a ≤ 50 nm) are not associated with extensive membrane thermal undulations or superstructures. In particular with respect to membrane curvature, the vesicle results are suggestive for the design and optimization of electroporative delivery of drugs and genes to cell tissue at small field strengths (≤1 MVm^–1) and large pulse durations (≤100 ms). Received: 8 July 1997 / Accepted: 15 September 1997     

Effect of noradrenalin and serotonin on responses of area CA3 neurons evoked in guinea pig hippocampal slices by electrical stimulation of mossy fibers

The effect of noradrenalin (NA) and serotonin (5-HT) on responses of area CA₃ cells evoked by electrical stimulation of mossy fibers was studied in slices of guinea pig hippocampus survivingin vitro. Both substances, which modify the general level and organization of spontaneous activity, also affected responses of area CA₃ cells. Changes in magnitude and structure of the response usually correlated with corresponding changes in spontaneous activity. In certain cases NA, which lowered the frequency of spontaneous activity but increased its relative content of "complex discharges" and also the number of reduced action potentials in the complex discharge, also led to an increase in the response to stimulation. 5-HT evoked periodic grouped activity in some cells and led to the appearance of such grouped discharges for the first time in the responses of other cells. Unlike NA, 5-HT caused prolonged (up to 40 min) after-facilitation of the response and an increase in spontaneous discharge frequency.Institute of Biological Physics, Academy of Sciences of the USSR, Pushchino-on-Oka. Translated from Neirofiziologiya, Vol. 14, No. 4, pp. 410–417, July–August, 1982.