Most physiological and ecological approaches to animal locomotion are based on steady state assumptions, yet movements of many animals are interspersed with pauses lasting from milliseconds to minutes. Thus, pauses, along with changes in the duration and speed of moves, form part of a dynamic system of intermittent locomotion by which animals adjust their locomotor behavior to changing circumstances. Intermittent locomotion occurs in a wide array of organisms from protozoans to mammals. It is found in aerial, aquatic and terrestrial locomotion and in many behavioral contexts including search and pursuit of prey, mate search, escape from predators, habitat assessment and general travel. In our survey, animals exhibiting intermittent locomotion paused on average nearly 50% of their locomotion time (range 6–94%). Although intermittent locomotion is usually expected to increase energetic costs as a result of additional expenditure for acceleration and deceleration, a variety of energetic benefits can arise when forward movement continues during pauses. Endurance also can be improved by partial recovery from fatigue during pauses. Perceptual benefits can arise because pauses increase the capacity of the sensory systems to detect relevant stimuli. Several processes, including velocity blur, relative motion detection, foveation, attention and interference between sensory systems are probably involved. In animals that do not pause, alternative mechanisms for stabilizing the perceptual field are often present. Because movement is an important cue for stimulus detection, pauses can also reduce unwanted detection by an organism's predators or prey. Several models have attempted to integrate energetic and perceptual processes, but many challenges remain. Future advances will require improved quantification of the effects of speed on perception.

The Behavioral Ecology of Intermittent Locomotion1

Auditory behavior of the cricket. II: Simplicity of calling-song recognition in Gryllus, and anomalus phonotaxis at abnormal carrier frequencies

Summary1.In applying the recently developed methods of compensated walking to the study of cricket phonotaxis, we have first asked how such devices alter the dynamic body-substrate situation from that experienced in natural walking on a fixed substrate. Because a quantitative treatment has not been available, we derive certain general mechanical requirements of such compensation systems, and show in this context just what the Kramer treadmill accomplishes.2.Mathematical predictions of the above analysis were confirmed by frame-by-frame TV analysis of crickets during natural walking and compensated walking on the Kramer treadmill. These are as follows. Body-substrate inertial effects can be made to resemble those occurring during fixed-substrate walking as long as the animal walks continuously and the compensation is highly damped. During starts and stops, however, body-substrate acceleration, and hence the associated leg forces, differ severely from those experienced in walking on a fixed substrate.3.Despite the above effects, the presence of some bearing noise, and the elimination of all visual guidance, we show that a useful form of ‘blind auditory tracking’ can be obtained regularly. Loudspeakers playing the male calling song are accurately tracked by females, with meandering of direction about the target direction, via several characteristic modes of start-stop behavior. The tracking mode adopted at any instant can depend upon song attractiveness, song intensity, the history of stimuli presented, the individual, and factors unknown to us. The mode adopted also affects the nature of the meandering seen in the direction record.4.Depending upon the season and the source of the crickets, one-quarter to one-half of adult females older than 3 to 4 weeks turn out to be ‘good trackers’ in our conditions, and to remain so for some weeks. Sound intensity has little effect upon tracking accuracy in the range 70–90 dB, as long as the song is an attractive one.5.We have developed experimental paradigms which test for discrimination by the female between male calling song and various ‘wrong songs’. These employ two alternating loudspeakers to control against directional clues available from the apparatus, and allow comparison of response to different songs both sequentially and simultaneously (the choice situation). We show that in both kinds of presentation females can clearly and reproducibly discriminate between calling song and wrong songs having no syllable structure or the wrong syllable repetition rate.6.If during the tracking of calling song the song is turned off, the female stops within a few seconds. If, instead, one replaces the calling song suddenly with a wrong song (rejected when presented alone), the wrong song is ‘tracked’ for 10 to 20 s or more. These effects have implications regarding operational definitions of ‘motivation’ and ‘context setting’; they may also lead to ways of distinguishing between the recognition and tracking processes.7.Contrary to expectation based on earlier work withGryllus campestris, we find that increasing the number of syllables per chirp in the range 4–8 (with repetition interval 30 ms) increases, rather than decreases, attractiveness of the song in both our sequential and our choice tests.8.The finding that attractiveness of a song increases with number of syllables suggests that inGryllus the key feature of sound signals that elicit ‘recognition and pursuit’ may be modulation power near 30 Hz, associated with the syllable repetition rate.This hypothesis predicts that natural ‘rivalry song’ (with chirps of 20 or more syllables near the 30-Hz rate) ought to be very attractive; we find that it is, and suggest a reinterpretation of its role in nature.9.In a separate set of experiments, the callingsong sound was gated by the walking-velocity signal so that sound could be heard either (i) only during walking or (ii) only during stops. Only our two best trackers succeeded in our tracking tests if sound was presented strictly during walking; 8 good trackers failed. With sound available only during stops, many succeeded if they happened to employ a suitable tracking mode. Our impression is that ‘stopping to listen’ (or even to look) is ordinarily a significant part of the search behavior.

Auditory behavior of the cricket. I: Dynamics of compensated walking and discrimination paradigms on the Kramer treadmill

1.

Many one-eared female crickets (Gryllus campestris andGryllus bimaculatus), whether the loss is due to surgery or to developmental accident, can maintain characteristic, stable courses with respect to the direction of male calling song, when tested on the Kramer spherical tread-mill. The error angles are usually less than 90°, so that Regen's (1924) remark about the success of such females in finding singing males is supported.




2.

Some females with developmental unilateral hearing deficit, confirmed both histologically and by sparing of tracking after removal of the suspect leg, track nearly as accurately as normal animals with two ears.




3.

Experiments in which tympana were immobilized with wax, whether tracking behavior or interneuron responses were monitored, show that the anterior tympanum — considered for some time to be irrelevant to hearing — mediates appreciable sound input to the auditory receptors, at least when the posterior tympana are blocked.




4.

The above results resolve two current paradoxes regarding comparison of tympanum immobilization in behavior with the mechanics of receptor excitation:

First, because even unambiguously one-eared animals can maintain stable sound-oriented courses, such tracking performance with waxed tympana does not argue that total tympanal immobilization spares some auditory function of that ear (cf. Schmitz et al. 1983). The argument assumes that tracking would not be expected if one ear were silenced; the assumption is evidently false.

Second, it has been unclear why waxing of both posterior tympana raises tracking threshold only ca. 20 dB (Schmitz 1983) whereas the tympanalmechanics studies of Kleindienst et al. (1983) have suggested a much greater deficit. Our finding that one must wax the anterior tympana as well, in order to produce deficit greater than ca. 20 dB, clarifies the situation. That is, in the biophysical experiments both tympana of the leg were immobilized by the procedures used (pressure matching and water immersion), whereas in most current behavioral tympanum-waxing experiments (but not in those of Bailey and Thomson 1977) the anterior tympana have been ignored.




5.

A novel behavioral effect was observed with all four tympana blocked. Thresholds for orientation were ca. 90–100 dB, but in every case the animals tended to walk away from the loudspeaker.




6.

The search for an explanation of one-eared tracking leads us to analogies with the recovery from imbalance following such surgery as hemilabyrinthectomy in vertebrates. A ‘phantom tympanum’, on the side with deficit, could in principle participate in corrective tracking, by the usual notions of bilateral comparison.

Auditory behavior of the cricket. IV. Interaction of direction of tracking with perceived temporal pattern in split-song paradigms

1 Acute as a Bug's Ear: An Informal Discussion of Hearing in Insects.- 2 Biophysics of Sound Localization in Insects.- 3 The Sensory Ecology of Acoustic Communication in Insects.- 4 Development of the Insect Auditory System.- 5 Neural Processing of Acoustic Signals.- 6 The Evolutionary Innovation of Tympanal Hearing in Diptera.- 7 The Vibrational Sense of Spiders.- 8 The Sensory Coevolution of Moths and Bats.

Comparative hearing : Insects

New information is presented on acoustic orientation in crickets following a comparison between a species with a discontinuous song pattern, Scapsepidus maginatus (Murphey & Zaretsky, 1972) and one with a continuous song pattern, Teleogryllus oceanicus . The females acuity for side discrimination is ± 10° from the body axis whereas the total phonokinetic response shows a greater degree of error. Females can scan their turn angle to target angles beneath 60°. Erros is expressed in terms of information loss through the total behavioural sequence. The cricket does not orient while moving, requires no fixed leg position during the stop for effective orientation and can establish source direction on the basis of at least two syllables. Evidence of differential anterior and posterior tympanic membrane function is suggested.

Acoustic Orientation in the Cricket Teleogryllus Oceanicus (Le Guillou)

BACKGROUND Progressive burden of diabetes mellitus is a major concern in India. Data on the predictors of poor glycemic control among diabetics are scanty. A population-based cross-sectional study nested in an urban cohort was thus conducted in West Bengal, India to determine the burden and correlates of total and uncontrolled abnormalities in glucose metabolism (AGM) in a representative population. METHODS From 9046 adult cohort-members, 269 randomly selected consenting subjects (non-response = 7.24%) were interviewed, examined [blood pressure (BP), anthropometry], tested for fasting plasma glucose (FPG) and glycosylated hemoglobin (HbA1C). Those having pre-diagnosed diabetes or FPG ≥126 or HbA1c≥6.5 were defined as diabetic. Among non-diabetics, subjects with FPG (mg/dl) = 100-125 or HbA1C(%) = 5.7-6.4 were defined as pre-diabetic. Pre-diagnosed cases with current FPG ≥126 were defined as uncontrolled AGM. Descriptive and regression analyses were conducted using SAS-9.3.2. RESULTS Among participants, 28.62% [95% Confidence Interval (95%CI) = 23.19-34.06)] were overweight [body mass index(BMI) = (25-29.99)kg/meter2], 7.81% (4.58-11.03) were obese(BMI≥30kg/meter2), 20.82% (15.93-25.70) were current smokers, 12.64% (8.64-16.64) were current alcohol-drinkers and 46.32% of responders (39.16-53.47) had family history of diabetes. 17.84% (13.24-22.45) had stage-I [140≤average systolic BP (AvSBP in mm of mercury)<160 or 90≤average diastolic BP (AvDBP)<100] and 12.64% (8.64-16.64) had stage-II (AvSBP≥160 or AvDBP≥160) hypertension. Based on FPG and HbA1c, 10.41% (6.74-14.08) were diabetic and 27.88% (22.49-33.27) were pre-diabetic. Overall prevalence of diabetes was 15.61% (11.25-19.98). Among pre-diagnosed cases, 46.43% (26.74-66.12) had uncontrolled AGM. With one year increase in age [Odds Ratio(OR) = 1.05(1.03-1.07)], retired subjects [OR = 9.14(1.72-48.66)], overweight[OR = 2.78(1.37-5.64)], ex-drinkers [OR = 4.66(1.35-16.12)] and hypertensives [ORStage I = 3.75(1.42-9.94); ORStage II = 4.69(1.67-13.17)] had higher odds of diabetes. Relatively older subjects [OR = 1.06(1.02-1.10)], unemployed [OR = 19.68(18.64-20.78)], business-owners [OR = 25.53(24.91-16.18)], retired [OR = 46.53(45.38-47.72)], ex-smokers [OR = 4.75(1.09-20.78)], ex-drinkers [OR = 22.43(4.62-108.81)] and hypertensives [ORStage II = 13.17(1.29-134.03)] were more likely to have uncontrolled AGM. CONCLUSIONS Burden of uncontrolled AGM was high among participants. Efforts to curb the diabetes epidemic in urban India should include interventions targeting appropriate diabetic control among relatively older persons, unemployed, business-owners, retired, ex-smokers, ex-drinkers and hypertensives.

/pdf/burden-and-socio-behavioral-correlates-of-uncontrolled-2zm0pr5vrl.pdf

Peter L. Thomson

Papers

Acoustic Orientation in the Cricket Teleogryllus Oceanicus (Le Guillou)

Burden and Socio-Behavioral Correlates of Uncontrolled Abnormal Glucose Metabolism in an Urban Population of India.