Direction of the ventilatory currents (arrows) flowing over the abdomen of larval ephemeropterans. (A) Ecdyonurus dispar, (B) Leptophlebia marginata, (C) Ephemera vulgata, (D) Cloëon dipterum, and (E) Caenis horaria.

Paths of the gills(arrows at dashed lines) of larval ephemeropterans.(a) Paths of two adjacent left gills of Ecdyonurus dispar viewed from behind. Solid lines represent the anterior of the two.(b) Paths of the two lamellae of the second pair of gills of Leptophlebia marginata viewed from behind. Solid lines represent the anterior of the two. (c) Path of a gill of Caenis horaria viewed from behind with ventilatory current flowing from left to right. C, compression; S, suction.

Effect of changes in ambient Po₂ (broken line) on ventilatory rate of intact, undisturbed larvae of Corydalis cornutus. Solid line connects mean ventilatory responses of six animals exposed at time 0 to hypoxia (10% O₂, 90% N₂), and later to normoxia (20% O₂, 80% N₂). Vertical bars represent one standard error of the mean.

Water flows (arrows) during inhalation and exhalation in Octopus vulgaris. (A) and (B) show views from side and from below during the brief expansion of the mantle; (C) and (D) show flows during the longer, exhalant, part of the cycle.

Pressure differential across the gills of Octopus vulgaris during (A) normal, quiet ventilation and (B) strong ventilation. Broken lines are the mean differentials.

Paths of water (arrows) through the gill chamber of Carcinus maenas (branchiostegite and limbs have been removed), c, cheliped; g 6–9, gills 6–9; m, third maxilliped; p 1–4, peraeopods 1–4; s, scaphognathite. Thickness of the arrows indicates the importance of the flow paths.

Gill ventilation volumes (cc/min) of a specimen of Cancer pagurus in two separate experiments, with both posterior and anterior inhalent openings unobstructed (normal—unshaded area), with posterior openings artificially closed (shaded area), and with anterior openings closed (stippled area).

Relationship between total number of gill platelets per gram dry tissue body weight and dry tissue body weight in Macrophthalmus hirtipes (○) and Helice crassa (•). The curve was fitted using normal back‐transformation of a least‐squares regression of platelet number on the inverse of body weights of both species combined.

Patterns of ventilation of the branchial chambers in Pseudothelphusa garmani. (A) Submerged—water breathing with forwardly directed gill ventilation. The scaphognathite generates an oscillating subambient hydrostatic pressure variation; r indicates a brief reversal of scaphognathite beat. (B) Bimodal breathing in shallow water, with access to air. Forwardly directed ventilation (a) switches to a maintained reversal (b), with increase in branchial chamber pressure to above the ambient level. This high pressure is maintained by alternate reversed scaphognathite beating and carapace movements (c) and slow pressure/volume changes generated by movements of the walls of the branchial chambers (d). These above‐ambient pressures draw air through the branchial chambers. (C) Air breathing after long‐term exposure to air, without access to water. The regular, slow pressure/volume changes, together with contraction of intrinsic muscles, generate ventilation of the branchial chambers and the invaginated lung.

Ventilation in dragonfly larvae. Recordings of (a, b) normal ventilation in Aeshna, (c) gulping ventilation in Aeshna, and (d) maintained abdominal compression in Anax imperator. Upper traces, dorsoventral movements of the sterna (upwards indicates lifting, i.e., expiration); lower traces, pressure changes in the branchial chamber in relation to ambient pressure (0) (upwards indicates positive pressure).

Thermistor records of (A) fast and (B) slow rectal pumping in a damselfly larva (Calopteryx splendens). The large exhalant pulse is followed by a series of inhalant strokes and then, in slow pumping, a pause.

Correlation between spiracular movements, oxygen uptake, carbon dioxide emission, composition of the tracheal gases, and intratracheal pressure during the three phases of passive suction ventilation in Hyalophora.

Endotracheal pressure variation during discontinuous ventilation in a 34 mg individual of Cataglyphis bicolor. is 4.16 μl · h⁻¹, DVC frequency is 1.0 mHz, ambient temperature 25°C. Note the very brief (about 10 s), small increase in pressure as the C phase starts (decrease in pressure).

Discontinuous carbon dioxide emission in a dune‐sea colony ant Camponotus detritus. (A) Typical pattern in an ant of mass 0.0473 g. Discontinuous ventilatory cycle (DVC) periodicity is 357 ± 64 s; is 0.0105 ± 0.0258 ml · h⁻¹. (B) Effect of activity on an ant of mass 0.0692 g: during activity (0–10 minutes), is 0.0475 ± 0.0246 ml · h⁻¹; after activity (from 25 minutes), is 0.0187 ± 0.0449 ml · h⁻¹.

Simultaneous recordings of water loss (upper trace) and discontinuous carbon dioxide emission (lower trace) in Romalea guttata at 25°C. The vertical dashed lines enclose one ventilatory cycle, in which bursts of carbon dioxide emission (C) alternate with periods of little or no carbon dioxide emission (D). The dashed line separating the respiratory water loss peak (A) from the cuticular component (B) represents an interpolation between the two adjacent interburst periods.

Discontinuous release of carbon dioxide (upper trace) and water (lower trace) by an individual female Pogonomyrmex rugosus alate of mass 31.4 mg at 25°C. Mean is 0.167 ± 0.411 cm³ · g⁻¹ · h⁻¹. DVC frequency is 0.925 mHz. Mean rate of water loss is 2.79 mg · g⁻¹ · h⁻¹. Peak burst rate of water loss yields a conservative estimate of water loss rate in the absence of spiracular control. Note that random interburst fluctuations in the water loss rate record are instrument noise.

Change of ventilation pattern with temperature in an individual of Apis mellifera of live mass 0.084 g. Metabolic rate is expressed per unit live mass. It is constant but appears to fluctuate above 11°C because it is estimated from the carbon dioxide emission rate, which varies above this temperature.

Pattern of ventilation in an individual of Onymacris plana of mass 0.639 g at 30°C during and immediately after activity. When inactive, mean is 0.143 ml · h⁻¹ and mean DVC period is 5.1 minutes. This is typical of the pattern displayed by a number of desert‐living tenebrionid beetles.

Ventilation rates of Locusta migratoria at different internal temperatures.

Ventilatory cycle of Hierodula membranacea. S, dorsal movements of the sterna (upwards indicates abdominal compression, i.e., expiration); ats, a chronic recording from the “expiratory” anterior tergosternal muscle.

Behavior of the spiracles of Schistocerca gregaria. (A) Before flight and during early part of flight, (B) about 30 minutes after start of flight, and (C) at end of flight and immediately after flight. Cl., spiracles closed; Exp., expiration; Insp., inspiration; O., spiracles open.

O₂‐N₂ diagrams. (a) Relationship between nitrogen and oxygen at pressures up to a total of 1.5 atm. Dashed line indicates their relative proportions in air. (b) Enlargement of the shaded area in (a). A indicates the relative proportions of nitrogen and oxygen in air at 1.0 atm. In a compressible gas gill their proportions change during a dive in the direction of B, provided the animal remains just below the water surface (i.e., at a pressure of 1.0 atm). If the animal dives to a depth of 1 meter (a pressure of 1.1 atm), the initial proportions are given by A' and they change during the dive in the direction of B'. To the right of × the gas gill loses oxygen to the water. In an incompressible gas gill the change in the proportions of the two gases is in the direction of C at all depths.

View of a flat plastron to illustrate diffusion paths of oxygen. h, height of plastron; x₁, maximum extent of plastron.

Relationship between relative drop in oxygen tension across the plastron interface and relative distance from the spiracle. Each curve is derived from (ΔPo)_x = (ΔP_o)_av cos h n(x₁ ‐ x)/sin h nx₁. (ΔP_o)_x, actual drop in oxygen tension at distance x from the spiracle; (ΔPo)_av, average drop in oxygen tension; h, height of the plastron; x, maximum extent of the plastron; n, (i_o/Dh)^1/2; i_o, invasion coefficient of oxygen; D, diffusion constant of oxygen within the plastron. nx₁ is a measure of the functional efficiency of the plastron. Curves are derived for various values of nx_1, i.e., 0.1 (A), 0.5 (B), 1.0 (C), 2.0 (D), 3.0 (E), 5.0 (F), and 10.0 (G).

Computed relationship between effective thickness of the boundary layer and current velocity.

(a) Relationship between ventilatory frequency and current velocity in larvae of Pycnopsyche guttifer and Pycnopsyche lepida. (b) Relationship between oxygen consumption and current velocity in normal and anesthetized larvae of the same two species.

Relationship between oxygen consumption and environmental oxygen concentration for various ephemeropteran larvae.

Simultaneous recordings of (a) oxygen consumption (▪) and heart rate (▴) and (b) scaphognathite rate (▴) and ventilation volume (▪) in Carcinus maenas during declining ambient oxygen tension.

Instantaneous rates of carbon dioxide release and oxygen uptake in Otala lactea, showing individual breaths before and during a burst of carbon dioxide release. No measurable gas exchange occurred between breaths when the pneumostome was closed.

Section of Carcinus maenas passing through the space between gills 5 and 6. Values of are shown at different levels between the gills at three sampling points. Percentage oxygen utilization values at the three levels are underlined. Solid arrows, water flow; arrows at dashed lines, blood flow.

Relationship between oxygen uptake and the percentage utilization of oxygen at different oxygen tensions in Procambarus simulans. Each type of symbol represents the measurements made on a single animal. Open symbols refer to oxygen uptake, while closed ones of the same shape represent utilization of oxygen by the same animal.

Oxygen consumption () of a ghost crab (Ocypode guadichaudii) run for a period of 20 minutes at 0.19 km · h⁻¹.

Intracellular recordings from four different types of expiratory motor neurons in Schistocerca gregaria. (a) Bursting motor neuron showing a decrease in frequency during the burst, (b) tonic motor neuron with higher frequency expiratory bursts, (c) motor neuron the activity of which waxes and wanes, and (d) phasic motor neuron which only fires at high ventilatory rates. Expiration is indicated by downward movement of the lower traces.

Spontaneous respiratory motor neuron activity in Anax parthenope julius. (a) Intracellular spikes in a large‐type expiratory motor neuron (upper trace) and corresponding 1 spikes in a second lateral nerve (larger spikes in n2A). (b) Intracellular spikes in an inspiratory motor neuron (upper trace) and corresponding 1 spikes in one of the motor neurons in the median nerve (sn). (c) IPSPs recorded in an inspiratory motor neuron during expiration; the two traces are continuous. Time calibration: 1 s (a and b), 0.1 s (c).

Intracellular recordings from inspiratory motor neurons in Scistocerca gregaria. (a) Bursts of spikes occuring only during inspiration, and (b) bursts of spikes during inspiration together with a lower firing frequency during expiration. Inspiration is indicated by upward movement of the lower traces.

Alternation of expiratory bursts in a second lateral nerve (n₂) and inspiratory bursts in the subintestinal muscle (sit) in an aeshnid larva.

Recording of expiratory burst from a second lateral nerve (n₂) and from the “Primary” expiratory dorsoventral muscle which innervates in (RDV) in Anax imperator. Note the 1:1 relation‐ship between one of the units in the nerve and the muscle potentials.

Recording of expiratory bursts from a second lateral nerve (lower traces) and from the “primary” expiratory dorsoventral muscle which it innervates (upper traces) in Aeshna. (a) Consecutive bursts, (b) superimposed potentials of a single burst, and (c) a single burst. Note facilitation of the muscle potentials.

Summary of normal ventilation in aeshnid dragonfly larvae showing, from the bottom, expiratory and inspiratory muscle activity, the strain produced by a single expiratory dorsoventral muscle, sternal movement, branchial chamber pressure, and opening of the anal valve. Exp., expiration; Exp. mus., expiratory muscle; Insp., inspiration; J. mus., inspiratory muscle; 5–8, abdominal segments 5–8.

Chronic recordings from muscles during normal ventilation in an aeshnid dragonfly larva. The top trace in each record is from the expiratory dorsoventral muscle of the seventh abdominal segment (rRDV7). The lower traces are from two different (a, b) longitudinal tergal muscles (1LT₂7 and 1LT₁9). l, left; r, right; final numeral indicates abdominal segment.

The relationship between the duration of expiratory (○) and inspiratory (•) bursts and the duration of the ventilatory cycle in Schistocerca gregaria.

Extracellular, chronic recording from an expiratory dorsoventral muscle of an unrestrained aeshnid larva showing the transition from normal ventilation (Vn) to jet‐propulsive swimming (S) and back again; a–d are continuous records.

Extracellular, chronic recordings from an unrestrained aeshnid larva during ventilation (Vn) and jet‐propulsive swimming. (a) Recordings from expiratory (rRDV7) and anterior (lADV7) dorsoventral muscles. (b) Recordings from anterior (lADV7) and posterior (lPDV7) dorsoventral muscles l, left; r, right; numeral indicates abdominal segment.

Extracellular, chronic recordings from an unrestrained aeshnid larva during ventilation (Vn) and jet‐propulsive swimming. Upper traces are from an expiratory dorsoventral muscle (rRDV6); lower traces are from one of the ventral, longitudinal muscles (rLLSP₁7). l, left; r, right; last numeral indicates abdominal segment.

“Free‐running” activity in the closer motor neurons innervating (a) second pair of spiracles (A, right; B, left) of Periplaneta americana, and (b) spiracles 1 (SP1) and 2 (SP2) of Schistocerca gregaria. In (b) the connectives between the meso‐ and metathoracic ganglia had been severed. (a from 65

Relationship between dorsoventral sternal movements (upper line: upwards indicates sternal lifting, i.e., abdominal compression) and the frequency of motor impulses in the nerve to the closer muscle of spiracle 1 of a locust (lower line: overall frequency of both closer motor neurons).

Simultaneous recordings from the motor nerves to the closer muscles of spiracles 1 (SP 1) and 2 (SP 2) in a locust during an expiratory pause.

Frequency of motor impulses in the nerves to the closer and opener muscles of spiracle 1 of Schistocerca gregaria during ventilation at a higher frequency than that shown in Figure 46. EXPⁿ, expiration; INSPⁿ, inspiration; GI, activity in the mesothoracic opener neurons; GII, activity in the prothoracic motor neurons.

Intracellular recording from a spiracle closer motor neuron in Schistocerca greguriu.

Intracellular recording from an opener motor neuron of spiracle 4 in Schistocerca gregaria. IPSPs, inhibitory postsynaptic potentials.

(a) Muscle activity in an expiratory dorsoventral muscle (DVM) and the opener muscle of spiracle 10 (Sp. 10) in Blaberus giganteus during rapid ventilation. (b) Muscle activity in the opener muscle of spiracle 10 (L, left; R, right) during transitional coupling in Blaberus giganteus. The right spiracle is dominant and shows strong expiratory bursts and weak inspiratory bursts; the left spiracle is subordinate and shows slight expiratory activity and strong inspiratory bursts.

Recordings from gill retractor and protractor motor neurons and muscles of the larva of Corydalis cornutus during ventilation. (A) Intracellular recording from a gill protractor muscle (upper trace) and extracellular recording from the nerve which innervates the retractor and protractor muscles (lower trace). (B) Extracellular recording from the nerve innervating the gill muscles (lower trace) and intracellular recording from a fiber in the retractor muscle (upper trace). Vertical calibrations refer to intracellular traces.

Sequential pattern of electrical activity in all swimmeret muscles during a single, representative cycle of swimmeret beating in Homarus americanus. Heavy bars correspond to the active periods of the muscles indicated on the ordinate. The pattern was reconstructed by combining numerous individual records of the type shown in Figure 54.

Representative records of the electrical activity of the bundles of swimmeret muscle fibers (upper traces) and the simultaneous movements of the corresponding swimmeret (lower traces; upwards indicate power stroke) during rhythmic swimmeret movements in Homarus americanus. The number at the start of each record identifies the bundle from which each record was taken (see Figure 53).

Time lag between the beginning of bursts in two motor neurons innervating the same muscle (Δ on the inset) in Homarus americanus, plotted against the duration of the corresponding movement cycle. r, Correlation coefficient. The inset shows the activity of the two motor neurons.

Phase position in the movement cycle at which a power stroke muscle in Homarus americanus begins to fire, plotted against the cycle duration. The phase position was calculated by dividing the cycle duration into the difference between the beginning of the cycle and the beginning of the electrical activity in the muscle. Negative phase positions denote power stroke activity that began during the preceding return stroke.

Recording from D1 depressor motor neuron in Carcinus maenas, showing that it contributes bursts of impulses to the motor programs for both forward and reversed gill ventilation. The bar above the record indicates a period of reversed ventilation, occurring spontaneously during normal forward ventilation. DN, depressor nerve; LN, levator nerve.

Recordings from L2 levator motor neurons in Carcinus maenas. (a) A motor neuron (L2F) that fires only during the forward rhythm of the scaphognathites. During a period of spontaneous reversals (bar on top of recording), the membrane potential oscillations of the cell are reduced considerably in amplitude and it remains silent. The dotted line on the intracellular trace indicates the resting membrane potential level of the motor neuron during pauses in rhythmic activity. (b) A motor neuron (L2R) which normally fires only during rhythm reversals. During the period of normal rhythmicity the membrane potential of the cell oscillates weakly in synchrony with the motor output pattern. During a period of spontaneous reversals (bar on top of recording), the oscillations increase in amplitude and a burst of spikes occurs on each depolarizing peak. DN, depressor nerve; LN, levator nerve.

Effect of the frequency of stimulation of a command interneuron (right interneuron B) in Procambarus clarkii. Recordings from right (upper traces) and left (lower traces) nerve roots of the third abdominal ganglion. Stimulation: (A) 20 Hz, (B) 25 Hz, (C) 30 Hz, and (D) 40 Hz.

Records showing that increasing stimulation frequency of a single command fiber in Homarus americanus decreases burst period and increases number of active motor neurons and their firing frequency. The third trace of each recording is a stimulus monitor.

Depolarization of interneuron 1a (INT_1a) in the first abdominal segment of Pacifastacus leniusculus causes a long‐lasting activation of the swimmeret system, as recorded in a power stroke neuron (PS₄) and a return stroke neuron (RS₄) of the fourth abdominal ganglion.

Intracellular recordings from interneuron 1b (INT_1b), a power stroke neuron (PS₄), a power stroke motor neuron (PS.MN₄), and the swimmeret flexor motor neurons (flex₁) of Pacifastacus leniusculus. Depolarization of INT_1b simultaneously excites the flexor motor neurons and inhibits the swimmeret rhythm (PS₄ and PS.MN₄).

(a) A large hyperpolarizing current injected into FMi2 (downward movement of lowest trace) triggers periods of reversed ventilation from both left (LEV₁) and right (LEV_r) levator motor neurons in Carcinus maenas. Note that there is one levator burst characteristic of forward ventilation before the start of the reversed motor pattern. (b) A large depolarizing current injected into FMi3 (upward movement of lowest trace) initially extends the levator bursts but then elicits a switch to reversed ventilation.

Intracellular recording from CPGi2 during forward (a) and reversed (b) ventilation in Carcinus maenas. Peak‐to‐peak amplitude of this oscillation is 22 mV. Arrow indicates the membrane potential (‐39 mV) during a ventilatory pause. DEP, depressor motor neurons; LEV, levator motor neurons; rev, reversed ventilation.

Effects of intracellular current injection into CPGi2 of Carcinus maenas. (a) Depolarizing current of 5 nA (upwards on bottom trace) stops the ventilatory rhythm and inhibits all levator motor neuron (LEV) activity, whereas some depressor motor neurons (DEP) become tonic. (b) Hyperpolarizing current of −3 nA (downwards on bottom trace) resets the motor output and stops the firing of the motor neuron innervating depressor muscle D2a (recorded in LEV trace) for the duration of the pulse.

Intracellular activity in two interneurons (INT.L24 and INT.L25) and two motor neurons (M.N.L7 and M.N.LDG₂) in Aplysia californica. During each cycle, activity in L25 precedes synaptic input to the other three neurons. Large IPSPs in LDG₂ are produced by L24. Thus at least part of the excitation of LDG₂ during a spontaneous burst in L25 is due to disinhibition.

Spontaneous burst in interneuron L26 of Aplysia californica produces excitatory synaptic activity and firing in the gill motor neuron LDG1, which in turn produces a gill contraction (GILL).

Spontaneously occuring compound postsynaptic potential, Input 3 (Ip.3), causes a rhythmic discharge in its follower cells in Lymnaea stagnalis. (Its first discharge on these recordings is indicated by a bar.) The interneuron RPeD1, and the visceral H (V.H Cell), mantle cavity (R.P.A Group) and pneumostome opener muscle (V.J Cell) motor neurons are all excited by this input.

Initiation of respiratory rhythm in the isolated brain of Lymnaea stagnalis by depolarization of interneuron RPeD1. Hy‐perpolarization of this interneuron (*) has no effect on the other two neurons, but depolarization (bar) initiates activity in interneuron IP3I (actually recorded from its follower VJ cell), while inhibiting interneuron VD4. Activation of IP3I in turn excites RPeD1 and the previously hyperpolarized VJ cell while inhibiting VD4. Upon recovery from inhibition by IP3I, VD4 fires a burst of action potentials, and the cycle is repeated spontaneously.

Intracellular recordings from two interneurons RPeD1 and IP3I and a follower VJ cell in Lymnaea stagnalis. Electrical stimulation of RPeD1 () inhibits the VJ cell while exciting IP3I by a biphasic action (i.e., inhibition followed by excitation). Once activated, IP3I excites both RPeD1 and the VJ cell ().

Retractor bursts recorded from segments 1–4 of a larva of Corydalis cornutus.

Recordings from the right first nerve root in the 5th (upper trace) and 4th (lower trace) abdominal ganglia of Procambarus clarkii.

Expiratory bursts recorded from expiratory dorsoven‐tral muscles of abdominal segments 5–8 of a larva of Anax impera‐ tor. S, sternal movements (upwards indicates lifting/abdominal compression, i.e. expiration).

Activity in an interneuron (int) and a mesothoracic closer motor neuron (mn) during ventilation in Schistocerca gregaria. (a) Normal ventilation. Bursts of spikes in the closer motor neuron correspond to expiration. (b) Depolarization of the interneuron with a steady current of 1.0 nA elicits a higher frequency of firing in the interneuron and shortens the motor neuron burst. (c) Hyperpolarization of the interneuron with a steady current of 0.5 nA reduces the number and frequency of spikes in the interneuron and increases firing in the motor neuron. (d) Hyperpolarization of the interneuron with a steady current of 1.5 nA eliminates spikes in the interneuron and increases firing in the motor neuron even further. Voltage calibration: motor neuron, 16 mV; interneuron, 8 mV.

Characteristics of the ascending inspiratory interneuron 516 in Procambarus clarkii. (A) Recordings of intracellular activity in interneuron 516 and extracellular activity from nerve 10 (Exp) of the metathoracic ganglion. (B) Positive current (+2 nA) injected into interneuron 516 increases its activity and increases the respiratory rate (Exp). (C) Phase‐response curve calculated using a pulse duration of 300 ms and a current of +2 nA. Dotted area indicates the average time in the cycle in which the neurons are active.

Characteristics of interneuron 725, located in the first unfused abdominal ganglion of Procambarus clarkii. (A) Recordings of intracellular activity in interneuron 725 and extracellular activity from nerve 8 (Exp) of the metathoracic ganglion. (B) Interneuron 725 hyperpolarized by a constant negative current of −3 nA to prevent firing. Positive current (+2 nA) injected into the interneuron causes a prolongation of the respiratory cycle. (C) Phase‐response curve calculated using a pulse duration of 350 ms and a current of +2 nA. Dotted area indicates the average time in the cycle in which the neurons are active.

Intracellular recordings from the ascending excitatory (AE) interneuron of Anax parthenope, together with expiratory bursts in a second lateral nerve (n2A) of the fifth abdominal ganglion and inspiratory bursts in the median nerve (sn) of the sixth abdominal ganglion. Time calibration: A, 2.5 s; B, 0.2 s. Voltage calibration applies to AE.

Intracellular recording from the ascending excitatory (AE) interneuron, together with expiratory bursts in a second lateral nerve (n2A) and inspiratory bursts in a median nerve (sn) of the larva of Anax parthenope. Stimulation of AE (upwards on bottom trace) during the period between inspiratory bursts (solid arrows) elicits bursts in the expiratory motor neurons, but stimulation during inspiration (arrows at dashed lines) has no effect on either expiratory or inspiratory motor neurons. Vertical calibration refers to top (mV) and bottom (nA) traces.

Increases in ventilatory rate of Carcinus maenas, (a) following a reduction in (upper trace). A longer “compensatory” increase in ventilatory rate (b) follows the return to normoxia after 18 minutes in hypoxia. Pauses alternating with short bouts of ventilatory bursting (arrow) occur during hyperoxia and normoxia.

(A) Possible reflex pathways in Homarus americanus, activated by retraction of a swimmeret and probably controlled by the coxal proprioceptors. Note the similarity of the effect on power stroke and return stroke neurons, and the reciprocal effect of this input on excitor and peripheral inhibitor axons to the same muscle. (B) Possible reflex pathways activated by stimulation of the sensory setae which border the rami of the swimmeret. Note the opposite effects of setae stimulation on the power stroke and return stroke motor neurons, and the reciprocal effect of setae stimulation on excitor and peripheral inhibitor axons to the same muscle. ▾, excitation; •, inhibition.

Recordings from second lateral nerves on one side of the fifth (5) and seventh (7) abdominal segments in an aeshnid larva; all from the same preparation. (a) Normal rhythm. (b, c) Effect of stimulation of the ipsilateral first lateral nerve of the seventh abdominal segment. (d) Normal burst and (e) elicited burst on an expanded time scale. Arrows indicate stimuli.

One‐to‐one entrainment of ventilatory rhythm to electrical stimulation in the larva of Corydalis cornutus. Recordings from nerve V1 of the third abdominal ganglion. Stimuli (stim) were delivered to nerve V_d of the same ganglion. (a) Unstimulated rhythm (84 beats · min⁻¹). (b) Stimulation at a frequency of 108 beats · min⁻¹.

Recording from the DN and LNa lateral nerve branches in Carcinus maenas. LNa contains the levator motor neurons; DN contains all of the depressor motor neurons except D2a, which is in nerve branch LNb. The spontaneous rhythm is interrupted by stimulation of nerve branch LNb with 3.0 V, 0.2 ms pulses at 20 Hz (solid line). The only depressor neuron that continues to fire is D2b. D1 is also a depressor motor neuron.