Pectoral Fin Beat Research Articles

The effect of progressive hypoxia on swimming mode and oxygen consumption in the pile perch, Phanerodon vacca

The effect of progressive hypoxia on swimming mode and oxygen consumption in the pile perch, Phanerodon vacca

Does motor noise from recreational boats alter parental care behaviour of a nesting freshwater fish?

Abstract Recreational boating activity has the potential to generate noise pollution that may influence wild fish. Such noise may be particularly relevant to fish engaged in parental care (PC), where alterations in behaviour could influence individual fitness and productivity of fish populations. Here, the PC behaviour of the freshwater largemouth bass (Micropterus salmoides) was examined to determine whether disturbance from boat noise altered paternal behaviour. Changes in nest‐tending and brood‐guarding behaviour were measured following exposure to noise treatments of 1‐min duration using underwater playbacks of recorded boat noises. One experiment compared the behaviour of bass tending eggs before, during, and after exposure to high‐speed or idling combustion motors, or an electronic bow‐mounted trolling motor. No significant differences in the time on nest, number of pectoral fin beats, and number of turns between the pre‐treatment, treatment, and post‐treatment periods for all three motor types were observed. A second experiment assessed the impacts of noise (high‐speed combustion motor only) on the behaviour of nesting bass across the development stages of offspring (i.e. egg, egg‐sac fry, and swim‐up fry). During the egg‐sac fry stage, nest‐guarding males turned significantly less on the nest during the noise treatment compared with the long‐term post‐treatment period, indicating a stage‐specific impact of boat noise on parental behaviour. The effect was transient, however, and limited to the period that the noise was present. Given that PC and recreational boating activity tend to co‐occur in nearshore areas, prolonged or frequent repeated exposure of nesting fish to boat noise during the egg‐sac fry stage could have adverse consequences for fitness and reproductive output. Efforts to restrict recreational boating activity in the vicinity of fish engaged in PC (e.g. through the use of set‐backs) would be a risk‐averse approach to mitigating the effects of noise pollution on fish.

Turbulent flow reduces oxygen consumption in the labriform swimming shiner perch, Cymatogaster aggregata.

Fish swimming energetics are often measured in laboratory environments which attempt to minimize turbulence, though turbulent flows are common in the natural environment. To test whether the swimming energetics and kinematics of shiner perch, Cymatogaster aggregata (a labriform swimmer), were affected by turbulence, two flow conditions were constructed in a swim-tunnel respirometer. A low-turbulence flow was created using a common swim-tunnel respirometry setup with a flow straightener and fine-mesh grid to minimize velocity fluctuations. A high-turbulence flow condition was created by allowing large velocity fluctuations to persist without a flow straightener or fine grid. The two conditions were tested with particle image velocimetry to confirm significantly different turbulence properties throughout a range of mean flow speeds. Oxygen consumption rate of the swimming fish increased with swimming speed and pectoral fin beat frequency in both flow conditions. Higher turbulence also caused a greater positional variability in swimming individuals (versus low-turbulence flow) at medium and high speeds. Surprisingly, fish used less oxygen in high-turbulence compared with low-turbulence flow at medium and high swimming speeds. Simultaneous measurements of swimming kinematics indicated that these reductions in oxygen consumption could not be explained by specific known flow-adaptive behaviours such as Kármán gaiting or entraining. Therefore, fish in high-turbulence flow may take advantage of the high variability in turbulent energy through time. These results suggest that swimming behaviour and energetics measured in the lab in straightened flow, typical of standard swimming respirometers, might differ from that of more turbulent, semi-natural flow conditions.

Acquired versus innate prey capturing skills in super-precocial live-bearing fish.

Live-bearing fish start hunting for mobile prey within hours after birth, an example of extreme precociality. Because prenatal, in utero, development of this behaviour is constrained by the lack of free-swimming sensory-motor interactions, immediate success after birth depends on innate, evolutionarily acquired patterns. Optimal performance however requires flexible adjustment to an unpredictable environment. To distinguish innate from postnatally developing patterns we analysed over 2000 prey capture events for 28 metallic livebearers (Girardinus metallicus; Poeciliidae), during their first 3 days after birth. We show that the use of synchronous pectoral fin beats for final acceleration and ingestion is fixed and presumably innate. It allows for direct, symmetrical control of swimming speed and direction, while avoiding head yaw. Eye movements and body curvatures, however, change considerably in the first few days, showing that eye-tail coordination requires postnatal development. The results show how successful prey captures for newborn, live-bearing fish are based on a combination of fixed motor programmes and rapid, postnatal development.

Eye movements are coordinated with pectoral fin beats during locomotion in a marine teleost fish

Animals must simultaneously engage multiple functional systems in order to navigate, feed and survive in complex environments. Nearly all vertebrates perform rapid gaze-shifting eye movements called saccades, but we know little about the behaviour of saccades during rhythmic locomotion. This study examined how saccades are coordinated with locomotor movements in a pectoral-fin-propelled teleost fish, Cymatogaster aggregata, the shiner surfperch. Individual fish were filmed swimming in a flow tank at 10 cm s(-1), and timing data were analysed using circular statistics. The results reveal that C. aggregata generates saccades non-uniformly throughout the pectoral fin cycle. Saccades primarily occur during fin abduction, when a large amount of thrust is produced, and rarely occur during the thrust-free refractory phase. Because vision is known to be impaired during saccades, we hypothesize that C. aggregata synchronizes saccades with periods of high acceleration in order to stabilize retinal images during low-acceleration phases, which are nearly saccade-free.

Movement and function of the pectoral fins of the larval zebrafish (Danio rerio) during slow swimming

Pectoral fins are known to play important roles in swimming for many adult fish; however, their functions in fish larvae are unclear. We examined routine pectoral fin movement during rhythmic forward swimming and used genetic ablation to test hypotheses of fin function in larval zebrafish. Fins were active throughout bouts of slow swimming. Initiation was characterized by asymmetric fin abduction that transitioned to alternating rhythmic movement with first fin adduction. During subsequent swimming, fin beat amplitude decreased while tail beat amplitude increased over swimming speeds ranging from 1.47 to 4.56 body lengths per second. There was no change in fin or tail beat frequency with speed (means ± s.d.: 28.2±3.5 and 29.6±1.9 Hz, respectively). To examine potential roles of the pectoral fins in swimming, we compared the kinematics of finless larvae generated with a morpholino knockdown of the gene fgf24 to those of normal fish. Pectoral fins were not required for initiation nor did they significantly impact forward rhythmic swimming. We investigated an alternative hypothesis that the fins function in respiration. Dye visualization demonstrated that pectoral fin beats bring distant fluid toward the body and move it caudally behind the fins, disrupting the boundary layer along the body's surface, a major site of oxygen absorption in larvae. Larval zebrafish also demonstrated more fin beating in low oxygen conditions. Our data reject the hypothesis that the pectoral fins of larval zebrafish have a locomotor function during slow, forward locomotion, but are consistent with the hypothesis that the fins have a respiratory function.

Kinematics and energetic benefits of schooling in the labriform fish, striped surfperch Embiotoca lateralis

Schooling can provide fish with a number of behavioural and ecological advantages, including increased food supply and reduced predator risk. Previous work suggests that fish swimming using body and caudal fin locomotion may also experience energetic advantages when trailing behind neighbours. However, little is known about the potential energetic advantages associated with schooling in fish that swim using their pectoral fins. Using the striped surfperch Embiotoca lateralis, a labriform fish that swims routinely with its pectoral fins, we found that pectoral fin beat frequencies were significantly higher for schooling individuals swimming in the front of a school relative to those swimming in the back, with trailing individuals benefiting from a 14.9 ± 3.2% reduction in fin beat frequency (mean ± SE). Trailing fish were estimated to benefit from a 25.6% reduction in oxygen consumption, based on correlations between swimming speeds and pectoral fin beat frequency and between swimming speeds and oxygen consumption of solitary fish. In addition, leading individuals in a school were estimated to have higher oxygen consumption than solitary individuals swimming at the same speed, based on their higher pectoral fin frequency. We suggest that this may be explained by differences in swimming behaviour, with schooling individuals continuously correcting their position relative to their neighbours whilst solitary individuals maintained a more rigid swimming pattern. Taking into account the increased oxygen consumption in leaders vs. solitary fish, we estimated that for an energetic advantage to occur in a school of striped surfperch as a whole, more than 78% of the individuals need to be in trailing positions, which is likely to be a common occurrence based on previous observations of other schooling species.

Pectoral fin beat frequency predicts oxygen consumption during spontaneous activity in a labriform swimming fish (Embiotoca lateralis)

The objective of this study was to identify kinematic variables correlated with oxygen consump- tion during spontaneous labriform swimming. Kine- matic variables (swimming speed, change of speed, turning angle, turning rate, turning radius and pectoral fin beat frequency) and oxygen consumption (MO2) of spontaneous swimming in Embiotoca lateralis were measured in a circular arena using video tracking and respirometry, respectively. The main variable influencing MO2 was pectoral fin beat frequency (r 2 =0.71). No significant relationship was found between swimming speed and pectoral fin beat frequency. Complementary to other methods within biotelemetry such as EMG it is suggested that such correlations of pectoral fin beat frequency may be used to measure the energy requirements of labriform swimming fish such as E. lateralis in the field, but need to be taken with great caution since movement and oxygen consumption patterns are likely to be quite different in field situation compared to a small lab tank. In addition, our methods could be useful to measure metabolic costs of growth and development, or bioassays for possible toxicological effects on fish.

The effects of acute temperature change on swimming performance in bluegill sunfishLepomis macrochirus

Many fish change gait within their aerobically supported range of swimming speeds. The effects of acute temperature change on this type of locomotor behavior are poorly understood. Bluegill sunfish swim in the labriform mode at low speeds and switch to undulatory swimming as their swimming speed increases. Maximum aerobic swimming speed (U(max)), labriform-undulatory gait transition speed (U(trans)) and the relationships between fin beat frequency and speed were measured at 14, 18, 22, 26 and 30 degrees C in bluegill acclimated to 22 degrees C. At temperatures below the acclimation temperature (T(a)), U(max), U(trans) and the caudal and pectoral fin beat frequencies at these speeds were reduced relative to the acclimation level. At temperatures above T(a) there was no change in these variables relative to the acclimation level. Supplementation of oxygen levels at 30 degrees C had no effect on swimming performance. The mechanical power output of the abductor superficialis, a pectoral fin abductor muscle, was measured in vitro at the same temperatures used for the swimming experiments. At and below T(a), maximal power output was produced at a cycle frequency approximately matching the in vivo pectoral fin beat frequency. At temperatures above T(a) muscle power output and cycle frequency could be increased above the in vivo levels at U(trans). Our data suggest that the factors triggering the labriform-undulatory gait transition change with temperature. Muscle mechanical performance limited labriform swimming speed at T(a) and below, but other mechanical or energetic factors limited labriform swimming speed at temperatures above T(a).

Mechanical and energetic factors underlying gait transitions in bluegill sunfish (Lepomis macrochirus)

As their swimming speed increased, bluegill sunfish (Lepomis macrochirus) switched from pectoral-fin-powered labriform swimming to undulations of the body axis. This gait transition occurred at a mean swimming speed of 0.24+/-0.01 m s(-1) and a pectoral fin beat frequency of 2.79+/-0.11 Hz (mean +/- s.e.m., N=6). The power output available from the main upstroke (adductor profundus) and downstroke (abductor superficialis) muscles, measured using the work-loop technique was maximal at the gait transition point. The cost of transport, measured by respirometry, increased as the fish switched from labriform to undulatory swimming. Our data show that bluegill changed gait as swimming speed increased to recruit additional muscle mass, rather than to maximize economy, as is the case for many terrestrial animals.

Bluegill Lepomis macrochirus synchronize pectoral fin motion and opercular pumping

The relative timing between operculum and pectoral fin motion was examined in swimming bluegill Lepomis macrochirus to determine if respiratory fluid flows from the operculum might have an effect on flow over the pectoral fin. Five bluegill were filmed swimming at speeds from 0·5 to 1·5 body (total) lengths s−1. The timing of opercular pumping and pectoral fin beating was noted and analysed using circular statistics. Fish tended to ventilate their gills every second or third pectoral fin beat. While locomotion and ventilation had different frequencies, however, they were synchronized: fish maintained a consistent phase relationship between them. Thus, within pectoral fin beats when the operculum pumps, the jet consistently occurred during pectoral fin abduction, ending just after the fin was fully abducted and beginning adduction. Based on the distance between the opercular slit and the pectoral fin base, the jet was estimated to reach the fin during maximum abduction. Dye flow visualization confirmed this estimate, revealing that the opercular flow wraps around the base of the fin during peak abduction, when it is likely to have little hydrodynamic effect.

Parasitic isopod Anilocra apogonae, a drag for the cardinal fish Cheilodipterus quinquelineatus

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 287:209-216 (2005) - doi:10.3354/meps287209 Parasitic isopod Anilocra apogonae, a drag for the cardinal fish Cheilodipterus quinquelineatus Sara Östlund-Nilsson1,4,*, Lynda Curtis2, Göran E. Nilsson3, Alexandra S. Grutter2 1Vision, Touch and Hearing Research Centre (VTHRC), School of Biomedical Sciences, and 2Department of Zoologyand Entomology, University of Queensland Brisbane, Queensland 4072, Australia 3Physiology Programme, Department of Molecular Biosciences, University of Oslo, PO Box 1041, 0316 Oslo, Norway4Present address: Department of Biology, University of Oslo, PO Box 1066, 0316 Oslo, Norway *Email: s.x.nilsson@bio.uio.no ABSTRACT: Cymothoid isopods Anilocra apogonae are regular ectoparasites of the cardinal fish Cheilodipterus quinquelineatus on the Great Barrier Reef. To determine whether this large isopod, attached to the head of the fish, affects the physiology and behaviour of its host, we conducted morphological measurements to obtain a condition index and several laboratory experiments on fish with and without isopods. The condition index did not vary between parasitised and non-parasitised wild fish. However, we found that parasitised fish lost more weight than unparasitised fish when fed a low food ration. Parasitised fish also had a higher rate of oxygen consumption than non-parasitised fish. When maintaining body posture in calm water, parasitised fish had an elevated pectoral fin beat frequency, probably because the isopod attaches asymmetrically, causing an asymmetrical weight balance for which the fish needs to compensate. Moreover, the sustained aerobic swimming speed as well as the swimming endurance at high water speeds were reduced in parasitised fish, possibly because of the drag from the parasite. The results suggest that parasites can have significant effects on fish even if this is not revealed by their body condition index in the wild. The metabolic effects found imply that parasitised fish may have to spend more time foraging to compensate for their higher metabolism. This could expose them to a higher risk of being eaten, a situation made worse by an impaired swimming ability that may reduce their capacity to escape a predator. KEY WORDS: Parasite · Isopod · Apogonidae · Cardinal fish · Condition index Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 287. Online publication date: February 18, 2005 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2005 Inter-Research.

Boxfishes (Teleostei: Ostraciidae) as a model system for fishes swimming with many fins: kinematics.

Swimming movements in boxfishes were much more complex and varied than classical descriptions indicated. At low to moderate rectilinear swimming speeds (<5 TL s(-1), where TL is total body length), they were entirely median- and paired-fin swimmers, apparently using their caudal fins for steering. The pectoral and median paired fins generate both the thrust needed for forward motion and the continuously varied, interacting forces required for the maintenance of rectilinearity. It was only at higher swimming speeds (above 5 TL s(-1)), when burst-and-coast swimming was used, that they became primarily body and caudal-fin swimmers. Despite their unwieldy appearance and often asynchronous fin beats, boxfish swam in a stable manner. Swimming boxfish used three gaits. Fin-beat asymmetry and a relatively non-linear swimming trajectory characterized the first gait (0--1 TL s(-1)). The beginning of the second gait (1--3 TL s(-1)) was characterized by varying fin-beat frequencies and amplitudes as well as synchrony in pectoral fin motions. The remainder of the second gait (3--5 TL s(-1)) was characterized by constant fin-beat amplitudes, varying fin-beat frequencies and increasing pectoral fin-beat asynchrony. The third gait (>5 TL s(-1)) was characterized by the use of a caudal burst-and-coast variant. Adduction was always faster than abduction in the pectoral fins. There were no measurable refractory periods between successive phases of the fin movement cycles. Dorsal and anal fin movements were synchronized at speeds greater than 2.5 TL s(-1), but were often out of phase with pectoral fin movements.

Effects of dissolved carbon dioxide on the physiology and behavior of fish in artificial streams

A new technology for treating waters contaminated with acid mine drainage involves the dissolution of limestone particles using carbon dioxide at pressures above ambient. Because of the fish health risks associated with episodes of high carbon dioxide levels in treated waters, we subjected three species of fish, brook trout (Salvelinus fontinalis), slimy sculpin (Cottus cognatus), and blacknose dace (Rhinichthys atratulus), to 24 h exposures of elevated dissolved carbon dioxide (CO2) at three levels, ranging from 1.0 (low) to 6.3 (high)%, under laboratory conditions. We measured blood physiological variables as well as behavior, including feeding responses, before, during, and after exposure. Physiological responses differed by species, but all species had elevated hematocrits after 1 h of exposure. Brook trout hematocritis were higher at medium and high levels of CO2 than in a control group (0.0% CO2) after 24 h of exposure. Slimy sculpin hematocrits were higher in medium- and high-level exposure groups than in controls after 1 h, but not after 24 h, of exposure. Blacknose dace hematocrits were higher in all three exposure groups than in controls after 1 h but only in medium-level exposure groups after 24 h. Brook trout plasma glucose was significantly higher in medium- and high-level exposure groups after 1 h, and in the high-level group after 24 h, than in controls. Slimy sculpin plasma glucose was not significantly different in elevated CO2 exposure groups from that of controls throughout exposure. Branchial ventilation was significantly greater in all species at elevated CO2 during exposure, indicating stress; however, no difference was observed between treatment and control groups of blacknose dace after 24 h, indicating acclimation. Pectoral fin beats and cough rates were not consistently related to CO2 exposure throughout the study. Brook trout had the longest lasting reaction to stress at lower levels of CO2 among the three species tested. Many of the 11 observed behavioral variables, related to swimming, feeding, social, and illness factors, were affected by elevations of dissolved CO2. Two to seven behavioral variables (18-64% of those measured) were affected by treatment level of dissolved CO2 with a trend by species for the number of variables affected: brook trout > blacknose dace > slimy sculpin. However, behavioral sensitivity to treatment level was greatest in blacknose dace. Recovery to pre-treatment activity rates for most behavior patterns (including feeding) was observed 24 h after cessation of exposure in all three species. Recovery was independent of treatment level, was most rapid in blacknose dace, and was slowest in brook trout. Overall, slimy sculpin was least affected behaviorally by elevated CO2. Although all three species showed stress response and changes in behavior at moderate levels of CO2 (> or = 2%), brook trout and blacknose dace showed evidence of ability to avoid harmful CO2 levels by swimming out of affected waters, whereas the slimy sculpin showed minimal behavioral changes despite remaining in place during exposure. Thus, predation risk and other sources of mortality seem minimal in the event of technological malfunction at a stream treatment site involving the use of CO2 under pressure.

Effects of dissolved carbon dioxide on the physiology and behavior of fish in artificial streams

A new technology for treating waters contaminated with acid mine drainage involves the dissolution of limestone particles using carbon dioxide at pressures above ambient. Because of the fish health risks associated with episodes of high carbon dioxide levels in treated waters, we subjected three species of fish, brook trout (Salvelinus fontinalis), slimy sculpin (Cottus cognatus), and blacknose dace (Rhinichthys atratulus), to 24 h exposures of elevated dissolved carbon dioxide (CO2) at three levels, ranging from 1.0 (low) to 6.3 (high)%, under laboratory conditions. We measured blood physiological variables as well as behavior, including feeding responses, before, during, and after exposure. Physiological responses differed by species, but all species had elevated hematocrits after 1 h of exposure. Brook trout hematocrits were higher at medium and high levels of CO2 than in a control group (0.0% CO2) after 24 h of exposure. Slimy sculpin hematocrits were higher in medium- and high-level exposure groups than in controls after 1 h, but not after 24 h, of exposure. Blacknose dace hematocrits were higher in all three exposure groups than in controls after 1 h but only in medium-level exposure groups after 24 h. Brook trout plasma glucose was significantly higher in medium- and high-level exposure groups after 1 h, and in the high-level group after 24 h, than in controls. Slimy sculpin plasma glucose was not significantly different in elevated CO2 exposure groups from that of controls throughout exposure. Branchial ventilation was significantly greater in all species at elevated CO2 during exposure, indicating stress; however, no difference was observed between treatment and control groups of blacknose dace after 24 h, indicating acclimation. Pectoral fin beats and cough rates were not consistently related to CO2 exposure throughout the study. Brook trout had the longest lasting reaction to stress at lower levels of CO2 among the three species tested. Many of the 11 observed behavioral variables, related to swimming, feeding, social, and illness factors, were affected by elevations of dissolved CO2. Two to seven behavioral variables (18–64% of those measured) were affected by treatment level of dissolved CO2 with a trend by species for the number of variables affected: brook trout>blacknose dace>slimy sculpin. However, behavioral sensitivity to treatment level was greatest in blacknose dace. Recovery to pre-treatment activity rates for most behavior patterns (including feeding) was observed 24 h after cessation of exposure in all three species. Recovery was independent of treatment level, was most rapid in blacknose dace, and was slowest in brook trout. Overall, slimy sculpin was least affected behaviorally by elevated CO2. Although all three species showed stress response and changes in behavior at moderate levels of CO2 (≥2%), brook trout and blacknose dace showed evidence of ability to avoid harmful CO2 levels by swimming out of affected waters, whereas the slimy sculpin showed minimal behavioral changes despite remaining in place during exposure. Thus, predation risk and other sources of mortality seem minimal in the event of technological malfunction at a stream treatment site involving the use of CO2 under pressure. © 2001 John Wiley & Sons, Inc. Environ Toxicol 16: 84–95, 2001

Effects of Water Acidity on Swimbladder Function and Swimming in the Fathead Minnow,Pimephales promelas

Swimbladder function, buoyancy-related behavior, and swimming performance were examined in fathead minnows (Pimephales promelas) following chronic (&gt;4 d) exposure to acid-treated water (pH 5.3). When denied surface access in still water, treated fish, unlike controls (pH 7.7), failed to increase buoyancy and standard volume over "access to air" levels and had significantly higher proportions of swimbladder CO2and O2. In current, treated fish reduced buoyancy over 48 h to a lesser extent than controls and were severely limited in their ability to increase internal pressure of swimbladder gases. pH significantly affected the maintenance of a minimum buoyancy over 32 d. Upon transfer from current to still water without access to air, the rate of buoyancy adjustment over 48 h was significantly slower in treated fish. With surface access, fish of both groups filled swimbladders within 6–12 h following removal from current; however, treated fish displayed significantly lower proportions of swimbladder CO2and O2at 12 and 24 h. Both groups of fish compensated hydrodynamically for insufficient static lift with higher frequencies of pectoral fin beats, treated fish having generally higher frequencies. Swimming performance was unaffected by water pH, but treated fish lost more weight than controls. We propose that impaired swimbladder function contributes to the elimination of fathead minnows from acidified environments.

Performance of motor systems in Antarctic fishes

Velocities of swimming and eye movements were measured in several species of nototheniid fish living at −1.9 °C in McMurdo Sound, Antarctica. 1. The most common mode of swimming was labriform. The speed of labriform swimming inPagothenia borchgrevinki, a cryopelagic species, was a linear function of pectoral fin beat frequency, reaching a maximum of 38 cm s−1 (1.8 L s−1) at a fin beat frequency of about 2 Hz (Fig. 2). 2. Subcarangiform swimming was employed for short dashes and escape responses. In this modeP. borchgrevinki attained a maximum swimming speed of 110 cm s−1 (4.9 L s−1) at a caudal fin beat frequency of 5.7 Hz. 3. The maximum amplitude of saccadic eye movements was about 20° inP. borchgrevinki, and 30° in the benthic speciesTrematomus bernacchii andT. centronotus. In all 3 species, amplitude was correlated with saccade velocity (Fig. 6). 4. Saccade velocities were variable compared with those of mammals. Outward saccades (away from the resting position of the eye) were slower than return saccades of the same amplitude. The maximum velocity of outward saccades was about 50 deg s−1; that of return saccades was about 120 deg s−1. 5. Maximum swimming speeds in antarctic fish are close to speeds predicted by extrapolation to the same temperature from temperate fishes, but saccade velocities are higher than predicted. The difference is attributed to a relative lack of temperature compensation in muscle, while there is a greater degree of compensation in the central nervous system.