流速对红鳍银鲫幼鱼游泳状态的影响

在28℃水温下,采用特制的鱼类游泳行为测定装置,研究体重(125.94±13.87)g的红鳍银鲫(Barbodes schwanenfeldi)幼鱼在0.0m/s(对照组)和0.1m/s、0.3m/s、0.5m/s3种流速下的游泳行为。结果表明,从0.0～0.3m/s,红鳍银鲫幼鱼平均趋流率和摆尾频率均随着流速的增加而增大,而0.5m/s组在90min内随时间延长而下降。红鳍银鲫游泳状态明显受到所处流速的影响,在静水对照组以"逆流前进"和"顺流而下"为主,两者共占总观察时间的98%以上;各流速组均以逆流静止为主,且随着流速的增大,逆流静止所占时间比例从45.8%增加至81.3%,而逆流前进所占时间比例由24.1%减至5%以下;逆流后退所占时间比例以0.1m/s组最大,为16.4%;顺流而下的比例随着流速增大先减小后增大,3个流速组依次为13.7%、2.1%和10.9%。红鳍银鲫幼鱼的游泳速度(V)和摆尾频率(TBF)在逆流前进及逆流静止两种游泳状态下呈线性正相关,而在逆流后退和顺流而下两种状态下两者没有显著相关。     

不同流速下杂交鲟幼鱼游泳状态与活动代谢研究

为研究水流速度对杂交鲟幼鱼行为和代谢的影响,探讨游泳状态与活动代谢及相关游泳运动参数之间的关系,在26℃水温下,使用特制的鱼类游泳行为和活动代谢同步测定装置,测定了杂交鲟幼鱼在0.1、0.3、0.5 m/s三种流速和静水条件下的游泳状态、趋流率、摆尾频率和耗氧率。结果表明:随着流速的增大,杂交鲟幼鱼逆流前进和逆流静止游泳状态所占时间比例显著减少,而逆流后退所占时间比例显著增加,顺流而下时间比例有所上升。在0.0—0.3 m/s的流速范围内,杂交鲟幼鱼各个时段的平均趋流率、摆尾频率和耗氧率均随着流速的增加而增大,在0.3 m/s流速下分别达到100%﹑(2.53±0.34)Hz和(490.99±164.59)mg O2/(kg.h)。当流速增加至0.5 m/s时,在趋流率仍保持100%的情况下,其耗氧率相比0.3 m/s增加了21.86%,而摆尾频率却减小了6.70%。实验过程杂交鲟幼鱼趋流率与摆尾频率呈显著线性正相关,而摆尾频率与耗氧率在大部分时段却无相关性。随着时间的延长,各流速组杂交鲟幼鱼趋流率、摆尾频率和耗氧率呈现不同的变化趋势,其趋流率均相对稳定;但摆尾频率均随时间延长呈下降趋势,而耗氧率则在实验前9h随时间延长逐渐增加,随后趋于稳定。研究结果提示:杂交鲟幼鱼游泳状态的变化与流速有关,而反映运动强度大小的摆尾频率与活动代谢率的关系受到游泳状态的显著影响,同时也与运动代谢特征的时间变化有关。       

障碍物对鳙幼鱼游泳行为的影响

天然河道底部的障碍物形成了复杂的水流环境，洄游鱼类对复杂水流环境的响应行为对于鱼能否上行或下行通过障碍物并完成生活史至关重要。本研究在封闭水槽中采用递增流速法测试了鳙(Aristichthys nobilis)幼鱼在不同障碍物型式下的临界游泳速度，结果表明：鳙幼鱼在自由来流、圆柱和半圆柱下的临界游泳能力无显著性差异(P>0.05),而方柱下鳙幼鱼的临界游泳能力显著降低(P<0.05);鳙幼鱼受障碍物下游复杂流场影响表现出3个特征游泳姿态，依此划分出3个位置区间；为了分析方柱下游泳能力下降的原因，统计了不同流速下鳙幼鱼在3个位置区间所占的时间百分比，并提取了相应的游泳动力学指标，包括摆尾频率、摆尾幅度、鱼头侧向最大加速度、鱼身侧向最大加速度、身体波动速度、身体波长和鱼头最大转角速度；鳙幼鱼在近柱区(障碍物下游6～26 cm; A区)停留时间最长，时间百分比高达63.1%;其次是中区(障碍物下游26～46 cm; B区)为29.1%;远柱区(障碍物下游46～66 cm; C区)最低，为7.8%;不同水流速度下，鳙幼鱼在方柱下游3个位置区间的时间百分比分布也有明显差异，在流速为5...     

不同体质量和饥饿程度对红鳍东方鲀幼鱼游泳能力的影响

为了考察不同体质量和饥饿程度红鳍东方鲀(Takifugu rubripes)幼鱼的游泳能力,利用行为生态学方法测定了不同体质量(0.22—3.31 g)和饥饿天数(1d、3d、6d和9d)下红鳍东方鲀幼鱼的绝对临界游速(U_crit,cm/s)、相对临界游速(U_crit’,体长/s,BL/s)、偏好游速(U_pref,cm/s)、6个流速区域(2—36 cm/s)下停留时间百分比(P_t,%)、偏好区域平均流速(V_mean,cm/s)和总游泳距离(D_1h,m)等游泳行为指标。结果显示,体质量和饥饿显著影响红鳍东方鲀幼鱼的U_crit、U_crit’、P_t、V_mean和D_1h。随体质量增加,实验鱼的U_crit、U_pref、V_mean和D_1h均逐渐升高,而U_crit...     

不同流速对鱇(鱼良)白鱼游泳行为的影响

在25℃水温下,采用特制的鱼类游泳行为测定装置对实验鱼在静水和0.1、0.2和0.25 m·s-1流速下的游泳状态、游泳速度、趋流率和摆尾频率等参数进行测定,研究水流速度对鱇(鱼良)白鱼(Anabarilius grahami)游泳行为的影响.结果表明:有流速组的趋流率显著高于静水组,但不同流速组间的趋流率无显著差别;在0 ～0.2 m·s-1流速范围内,摆尾频率随流速加快而显著增大,但在0.25 m·s-1流速下40 min后摆尾频率显著低于0.2m·s-1流速组;随着流速的增大,主要游泳状态由逆流前进变为逆流静止;在有流速组,顺流而下状态所占时间比例相对其他游泳状态都较少;在逆流游泳的3种状态中,游泳速度均随流速的增加而增大,在顺流而下状态中,游泳速度和水速间无显著相关;游泳速度、摆尾频率和水流速度两两之间均存在显著的线性相关.     

鲢幼鱼在不同水流速度下的暴发-滑行行为策略

在水温（18±1）℃的条件下,以全长（11.70±0.57）cm的鲢（Hypophthalmichthys molitrix）幼鱼为研究对象,测定其不同流速（16.5、22.0、27.5、33.0、38.5、44.0、49.5和55.0 cm/s）下的持续游泳时间、调头百分比和暴发-滑行运动数据。结果表明,鲢的平均持续游泳时间先随流速的增加而减小,后随流速的增加而增加。当流速33.0 cm/s时,平均持续时间最短为118.6min,其中各组试验鱼的最大可持续游泳时间均可达到200min。调头百分比随流速的增加迅速减小,当流速≥44.0 cm/s时,不再出现调头行为。暴发-滑行游泳的平均暴发时间随流速的增加呈上升趋势（y=0.03x+2.64,R2=0.92,P<0.05）。平均对地暴发距离均在30-45 cm,没有显著性差异（P>0.05）,平均绝对暴发距离存在极显著性差异,且随流速的增加而增加（y=4.98x-5.63,R2=0.98,P<0.001）。平均对地暴发速度没有显著性差异（平均对地平均速度和最大速度分别在9-12 cm/s、12-16 cm/s,P>0.05）。平均绝对暴发速度与水流速度之间存在线性正相关关系（平均绝对平均暴发速度:y=0.98x+10.74,R2=1.00,P<0.001;平均绝对最大暴发速度:y=1.02x+13.75,R2=0.99,P<0.001）。研究表明鲢在不同的流速下采取的暴发-滑行行为策略不同。     

游泳加速模式对团头鲂和南方鲇的最大游泳速度及运动代谢的影响

为了探讨游泳加速模式对不同生态习性鱼类游泳性能及运动代谢的影响, 评估团头鲂(Megalobrama amblycephala)和南方鲇(Silurus meridionalis)的临界游泳速度(U_crit)、爆发游泳速度(U_burst)和最大代谢率(MMR)的适宜测定方法, 在4种加速模式条件下, 检测了实验鱼的最大游泳速度(V_max), 以及鱼体在运动过程中及其力竭后代谢恢复期的耗氧率(MO₂)。结果显示: 在速度增量(ΔV)为20 cm/s, 加速持续时间(Δt)为2min的加速模式条件下, 团头鲂和南方鲇的V_max及游泳过程的无氧代谢占比均分别显著高于其他3种加速模式(P< 0.05), 呈爆发运动(U_burst)状态。在ΔV为10 cm/s, Δt分别为20、40和60min 的加速模式下, 两种鱼的无氧代谢占比均在12%以下且相互间无显著差异(P>0.05); 其中团头鲂在这3种加速模式下的V_max之间无显著性差异(P>0.05); 而南方鲇在ΔV为10 cm/s、Δt为20min条件下的V_max显著高于另2种加速模式的测定值(P< 0.05)。两种鱼的MO₂在各加速模式下均随着游泳速度的升高而增加; 但在爆发游泳过程中, 两种鱼的MO₂随游泳速度的增加呈现不同的变化趋势, 团头鲂的MO₂随速度的变化曲线在接近100 cm/s的时候出现拐点, 此后MO₂随速度的增幅变小; 而南方鲇的该曲线在速度为20 cm/s时就出现拐点, MO₂的变化进入“平台期”。在所有加速模式下, 两种鱼在运动过程中的最大耗氧率(AMO₂)均显著高于力竭后代谢恢复期的最大值(DMO₂, P< 0.05)。用U_crit法测得团头鲂的AMO₂高于U_burst法的测得值, 而南方鲇则相反。由研究结果得出, 测定团头鲂的U_crit采用ΔV为10 cm/s、Δt在20—60min的加速模式是适宜的, 测定南方鲇U_crit的适宜加速模式是ΔV为10 cm/s、Δt为20min。两种鱼均应采用在运动阶段测得的最大MO₂作为MMR; 测定团头鲂的MMR适用于U_crit法, 测定南方鲇的MMR适用于U_burst法。团头鲂持续游泳的能力较强, 爆发游泳的加速能力相对较弱; 而南方鲇则表现出相反的趋势, 该差异反映了物种适应其生态习性的权衡效应。     

加速流对鲢、鳙幼鱼下行过程中游泳行为的影响

研究以具有下行洄游需求的鲢(Hypophthalmichthys molitrix)、鳙(Aristichthys nobilis)幼鱼为实验对象, 分别在2种不同流态加速流(Ⅰ: 22—55 cm/s, Ⅱ: 25—60 cm/s)中进行下行实验, 对实验鱼在2种加速流中的游泳行为(下行率、下行方式及各区域游泳时间)进行定量分析并利用游泳停留时间百分比F_t衡量其偏好水流速度。结果显示: 加速流下鲢、鳙均表现出了直接下行与非直接下行两种行为。其中加速流Ⅰ中鲢、鳙直接下行率分别为35.71%、30.00%, Ⅱ中分别为45.83%、59.09%。非直接下行的鲢在2种加速流中小于30 cm/s流速区域的停留时间显著高于其他区域(P<0.05), 即鲢在实验条件下的偏好水流速度范围为小于30 cm/s; 非直接下行的鳙在加速流Ⅰ中小于30 cm/s及50—55 cm/s流速区域的停留时间显著高于其他区域(P<0.05), Ⅱ中小于30 cm/s流速区域的停留时间显著高于其他区域(P<0.05), 即鳙本实验条件下偏好水流速度范围为小于30 cm/s。将2种加速流流速相同区域合并分析发现鲢、鳙在小于30 cm/s和50—55 cm/s流速区域的停留时间存在显著性差异(P<0.05), 中间及高流速区域无明显性差异(P>0.1)。研究表明: 加速流对鲢、鳙下行游泳行为产生了影响且2种鱼在下行通过方式和偏好流速选择上存在一定的种间差异性。     

流速对细鳞裂腹鱼游泳行为及能量消耗影响的研究

通过自制密封的鱼类游泳实验装置, 研究了流速对细鳞裂腹鱼游泳行为和能量消耗的影响。结果显示,细鳞裂腹鱼的摆尾频率随游泳速度的变化有明显的变化规律, 摆尾频率随着流速的增加而显著性的增加,而摆尾幅度有减小趋势, 差异性不显著。结果还表明, (26±1) ℃时, (10.60±0.54) cm 细鳞裂腹鱼的相对临界游泳速度为(11.5±0.5) BL/s, 绝对临界游泳速度为(110.28±2.02) cm/s。测定的相对临界流速较其他的鲤科鱼大,是对生存水流环境(流速0.5—1.5m/s)适应性的表现。这一结果表明鱼类的游泳能力是能够训练的。运动代谢率与相对流速的关系为, AMR = 93.08e(0.307v) + 314.33, R2= 0.994; 单位距离能耗与流速的指数关系为COT =28e (-1.03V) +6.05, R2= 0.998。流速达到8 BL/s 时, 裂腹鱼耗氧率开始下降, 从流速7 BL/s 时, (1245.57±90.97 )mg O2/(kg·h)最大, 下降到(978.78±189.38) mg O2/(kg·h)。1—7 BL/s 流速范围内, 裂腹鱼单位时间内的耗氧率随着游泳速度的增加而增加, 而且随着游泳速度的增加, 单位距离能耗(COT)逐渐减少, 最小能耗在6 倍体长流速, 0.68 m/s 时, 为(6.00±1.57) J/(kg·m), 其能量利用效率最大。       

亚成体巨须裂腹鱼游泳能力及活动代谢研究

以野生雅鲁藏布江巨须裂腹鱼(Schizothorax macropogon)为对象,通过自制的鱼类游泳实验装置,测定了4个温度(5、10、15和18℃)梯度下亚成体巨须裂腹鱼的临界游泳速度(Ucrit)及流速变化对耗氧率的影响,并通过摄像记录分析了不同游泳速度下的游泳行为。野生亚成体巨须裂腹鱼的临界游速随着温度的变化呈近似线性的递增趋势(P<0.001),4个温度下的绝对临界游速(Ucrit-a)分别为(0.88±0.07)、(1.09±0.07)、(1.24±0.15)和(1.49±0.15)m/s;若以单位时间内游过的体长倍数(BL/s)表示,相对临界游速(Ucrit-r)分别为(3.96±0.21)、(4.4±0.16)、(4.9±0.18)和(5.35±0.14)BL/s。根据不同温度及流速下耗氧率的变化情况,采用非线性拟合得到了4个温度梯度下耗氧率与游泳速度关系的幂函数模型(P<0.05)。模型表明耗氧率随游泳速度的增大而增加,且温度越高耗氧率随游泳速度的变化越显著。4个温度下的速度指数分别为2.4、2.6,2.8及3.1,表明有氧运动的效率随温度升高有所降低。在自然水温条件下(5—9℃),摆尾频率(TBF)与流速的关系呈线性正相关(P<0.001),而运动步长(Ls)的变化与流速没有显著关系,出现由高至低再升高的三个阶段。录像分析表明在流速逐渐增加的过程中,巨须裂腹鱼采用了三种不同的游泳方式,以实现降低能量消耗的目的。研究可为鱼道等过鱼设施的设计提供参考,对数量日益减少的巨须裂腹鱼保护具有较大的意义。     

The swimming performance of brown trout and whitefish: the effects of exercise on Ca2 + handling and oxidative capacity of swimming muscles

The swimming performance of two fish species, the brown trout and whitefish, having initially different swimming strategies, was measured after nine different training programs in order to relate the effects of exercise on Ca²⁺ handling and oxidative capacity of swimming muscles. The time to 50% fatigue was measured during the training period, and compared with the density of dihydropyridine (DHP) and ryanodine (Ry) receptors and succinate dehydrogenase (SDH) and phosphorylase activity determined by histochemical analysis of the swimming muscles. Overall, both trained brown trout and whitefish had superior swimming performance as compared to control ones. Interestingly, the training programs had different effect on the two species studied since brown trout achieved the highest swimming performance, swimming against the water flow velocity of 2 BL s⁻¹ while among whitefish the best efficiency was seen after training with lower swimming velocities. Training also induced a significant increase in DHP and Ry receptor density in both species. Generally, in brown trout the most notable increase in the receptor densities was observed in red muscle sections from the fish swimming for 6 weeks against water currents of 1 BL s⁻¹ (DHPR 176.5 ± 7.7% and RyR 231.4 ± 11.8%) and white muscle sections against 2 BL s⁻¹ (DHPR 129.6 ± 12.4% and RyR 161.9 ± 15.5%). In whitefish the most prominent alterations were noted in samples from both muscle types after 6 weeks of training against water current of 1.5 BL s⁻¹ (DHPR 167.1 ± 16.9% and RyR 190.4 ± 19.4%). Finally, after all the training regimens the activity of SDH increased but the phosphorylase activity decreased significantly in both the species. To conclude, our findings demonstrate an improved swimming performance and enhanced Ca²⁺ regulation and oxidative capacity after training. Moreover, there seems to be a connection between the swimming performance and receptor levels, especially in white swimming muscles of different fish species, regardless of their initially deviant swimming behaviours. However, depending on the training regimen the divergent swimming behaviours do cause a different response, resulting in the most prominent adaptational changes in the receptor levels of red muscle samples with lower swimming velocities in brown trout and with higher ones in whitefish.     

Swimming response of goldfish,Carassius auratus,and the tetra,Hemigrammus caudovittatus,larvae to individual food items and patches

Synopsis Swimming speed and swimming path of goldfish and tetra larvae were studied in aquaria containing food patches composed of decapsulated cysts and immobilized nauplii of Artemia salina or sparsely distributed prey. The mean swimming speed of starved larvae in the medium without food was about four times higher than the speed of larvae feeding in a patch. Satiated larvae swam about 1.5 times slower than hungry fish. Consumption of single prey items by starved larvae caused the following sequence of swimming responses: handling pause (cessation of swimming), slow swimming in a restricted area, and fast swimming (approximately twice as fast as hungry larvae before encountering food) accompanied by a widening of the area searched (area increased searching). Mean swimming speed was constant over a broad range (10¹–10³ ind·1^–1 of food density, although at extreme (high or low) values of food density it depended on swimming responses of the predator. Frequency of visits to the different parts of the aquarium strongly depended on encounters of hungry fish with food particles or patches.     

The effects of fasting on swimming performance in juvenile qingbo (Spinibarbus sinensis) at two temperatures

We measured the following variables to investigate the effects of fasting and temperature on swimming performance in juvenile qingbo (Spinibarbus sinensis): the critical swimming speed (U_crit), resting metabolic rate ${(\dot{\mathrm{M}}O}_{\mathrm{2rest}})$ and active metabolic rate ${(\dot{\mathrm{M}}O}_{2active})$ of fish fasting for 0 (control), 1, 2 and 4 weeks at low and high acclimation temperatures (15 and 25 °C). Both fasting treatment and temperature acclimation had significant effects on all parameters measured (P<0.05). Fasting at the higher temperature had a negative effect on all measured parameters after 1 week (P<0.05). However, when acclimated to the lower temperature, fasting had a negative effect on U_crit until week 2 and on ${(\dot{\mathrm{M}}O}_{\mathrm{2rest}})$, ${(\dot{\mathrm{M}}O}_{\mathrm{2active}})$ and metabolic scope (MS, ${(\dot{\mathrm{M}}O}_{\mathrm{2active}})$–${(\dot{\mathrm{M}}O}_{\mathrm{2rest}})$) until week 4 (P<0.05). The values of all parameters at the lower temperature were significantly lower than those at the higher temperature in the identical fasting period groups except for ${(\dot{\mathrm{M}}O}_{\mathrm{2rest}})$ of the fish that fasted for 2 weeks. The relationship between fasting time (T) and U_crit was described as U_crit(15)=−0.302T²−0.800T+35.877 (r=0.781, n=32, P<0.001) and U_crit(25)=0.471T²−3.781T+50.097 (r=0.766, n=32, P<0.001₎ at 15 and 25 °C, respectively. The swimming performance showed less decrease in the early stage of fasting but more decrease in the later stage at the low temperature compared to the high temperature, which might be related to thermal acclimation time, resting metabolism, respiratory capacity, energy stores, enzyme activity in muscle tissue and energy substrate utilization changes with fasting between low and high temperatures. The divergent response of the swimming performance to fasting in qingbo at different temperatures might be an adaptive strategy to seasonal temperature and food resource variation in their habitat.     

桂林市游泳儿童隐孢子虫感染现状调查

目的了解广西壮族自治区桂林市游泳儿童隐孢子虫感染现状。方法根据桂林市地理位置抽取6家游泳馆,于2017年8月初问卷调查选中游泳馆中小于14岁的游泳儿童,同时采集儿童24h内的新鲜粪便,使用RIDA~隐孢子虫快速检测法检测粪便隐孢子虫卵囊;每个游泳馆采集2次泳池水样,每次采集1份水样,并于4h内检测水质微生物指标(细菌总数、大肠菌群),其余水质指标(游离性余氯、浑浊度、尿素、pH)现场测定。结果共调查298人(2~13岁),男性儿童165人,女性儿童133人,游泳儿童隐孢子虫感染率为4.0%,其中男性儿童感染率为4.2%,女性儿童感染率为3.8%,5岁以下游泳儿童感染率最高(4.5%),10岁以上游泳儿童感染率最低(2.9%);6家游泳馆水质检测指标中尿素(33.3%)和余氯(16.7%)合格率较低,其余检测指标(浑浊度、pH、细菌总数、大肠菌群)合格率为100.0%。游泳儿童隐孢子虫感染人数在不同性别、年龄段中差异无统计学意义(P0.05);在不同余氯浓度、不同浑浊度游泳馆中分布差异有统计学意义(P0.05),。结论该地区游泳儿童存在隐孢子虫感染;增加泳池余氯量不能降低游泳儿童感染隐孢子虫的风险,降低泳池水浑浊度有利于降低游泳儿童隐孢子虫感染风险。     

Depth telemetry from the sixgill shark,Hexanchus griseus,at Bermuda

Synopsis Transmitters were attached to two female sixgill sharks, Hexanchus griseus, which were followed in course and depth for periods of 4 and 2 days. The sharks swam slowly (10 to 20 cm s^-1) and continuously, generally moving parallel to the bottom contours within a limited (less than 10 km long) area. The greatest depth was an excursion to 1500 m, but otherwise the sharks remained near the bottom at depths ranging from 600 to 1100 m.     

铜绿假单胞菌泳动能力相关新基因的筛选及鉴定

从Mu转座突变子文库中经过表型筛选,得到12株泳动(Swimming motility)能力缺陷的突变子,经Mu转座子插入位点的确认、基因克隆及测序分析发现其中10个突变子中Mu转座子分别插入到10个不同的与鞭毛运动和功能相关的基因中,2个突变子中Mu转座子插入到功能未知的新基因(PA2950和PA5022)中,电镜观察结果表明这2个突变株均具有完整的鞭毛,初步推测这2个基因可能是参与鞭毛泳动的能量代谢、趋化作用或信息传递的新基因。     

The influence of temperature on diving behaviour in the alpine newt, Triturus alpestris

An aquatic lifestyle poses serious restriction to air-breathing animals in terms of time and energy spent during a dive cycle. The diving frequency increases with water temperature, therefore an ectotherm's time budget greatly depends on the thermal characteristics of the aquatic environment. Available data suggests that time costs caused by temperature-dependent dive frequency can be partially compensated for by adjusting the swimming speed and diving angle during dive cycle. We tested this prediction by examining the influence of temperature on the diving behaviour of the alpine newt, Triturus alpestris. The ascending speed and angle showed disparate patterns of temperature dependency, with a minor influence on travel duration. Surprisingly, at higher temperatures, the diving newts saved most of their time by restricting swimming activity in the water column during their return to the bottom and not by adjusting their ascending duration. Hence, aquatic newts have the capacity to reduce temperature-dependent time costs of aerial breathing primarily by behavioural modifications during the descending phase of the dive cycle.     

Hexamethonium sensitivity of the swim musculature of the pteropod mollusc, <Emphasis Type="Italic">Clione limacina</Emphasis>

Swimming in reduced electrophysiological preparations of the pteropod mollusc, Clione limacina, was blocked by bath application of hexamethonium even though pattern generator activity continued with this treatment. Neuromuscular recordings indicated that hexamethonium blocked synaptic input from Pd-3 and Pd-4 motoneurons to slow-twitch muscle cells, while connections from Pd-1A and Pd-2A motoneurons to fast-twitch muscle cells were variable in their response to hexamethonium—synaptic inputs were suppressed in most cases and occasionally blocked, but the latter only with high concentrations and long incubations. Acutely dissociated wing muscle cells showed a concentration-dependency in the percentage of contracted cells with bath application of acetylcholine, and this contractile activity was blocked in preparations that were first bathed in hexamethonium. Intracellular recordings from dissociated slow-twitch muscle cells showed conductance-increase depolarizations of approximately 20 mV following 1 s pressure ejections of 10⁻⁴ M acetylcholine from micropipettes placed immediately adjacent to the muscle cells. These responses were blocked when hexamethonium was bath applied prior to the pressure-applied acetylcholine. The results suggest the Pd-3/Pd-4 motoneuron to slow-twitch muscle cell junctions are cholinergic with nicotinic-like receptors, while the Pd-1A/Pd-2A to fast-twitch muscle cell connections are likely cholinergic, but with a different receptor type.