聚苯乙烯微塑料长期暴露对海水青鳉(Oryzias melastig-ma)亲代生长、繁殖及子代发育的影响

微塑料污染是近年来受到国际社会广泛关注的海洋环境问题之一,由微塑料造成的生态和人类健康风险不容小觑,但微塑料对鱼类的长期危害目前尚无定论.为评估微塑料颗粒对海洋鱼类的长期影响,选取塑料生产和环境中常见的聚苯乙烯(polystyrene,PS)为研究对象,对海水青鳉(Oryzias melastigma)60 dph(days post hatching,dph)幼鱼进行了为期50 d的长期暴露,系统研究PS暴露对海水青鳉亲代的生长、繁殖和子代胚胎发育等的影响.结果显示,在粒径为10μm、浓度为1×104 parti-cles·L-1和1×105 particles·L-1暴露条件下,PS处理组亲代体长和体质量的改变与对照组相比无显著差异,PS暴露未显著影响亲代性成熟进程和受精过程;PS暴露未显著影响子代胚胎心率和孵化时间,但能显著降低子代孵化率,造成胚胎发育畸形.上述结果表明,PS长期暴露对亲代生长和繁殖未产生明显影响,但对子代的胚胎发育具有不利影响,研究结果为科学评估海洋微塑料污染的生态风险提供了重要参考.     

城镇污水处理厂进出水对日本青鱂早期阶段亚慢性毒性效应

采用日本青鳉胚胎及幼鱼暴露评估污水处理厂进出水的综合毒性效应。水样采自广州市3个污水处理厂的进水口和出水口。96 h青鳉幼鱼急性毒性试验表明:6个水样均没有对青鳉幼鱼产生急性毒性效应。14 d胚胎暴露试验结果:3个污水处理厂的进水及1号和3号污水处理厂的出水均引起胚胎死亡,胚胎孵化率均低于70%且均与对照组产生了显著性差异(p0.05)。3个厂的进水和1号、2号厂出水的鱼苗畸形率与对照组也有显著差异(p0.05),其中3号厂进水鱼苗畸形率高达(33.73±8.94)%。而6个水样的胚胎孵化时间均与对照组无显著差异(p0.05),均在9 d左右。7 d鱼苗暴露试验结果:1、2、3号3个水厂进水的鱼苗死亡率分别是(30.16±2.75)%,(24.07±1.60)%,(37.90±4.77)%,与对照组产生明显差异(p0.05)。出水对鱼苗的致死效应明显低于进水,但出水对鱼苗的致死效应相对于对照组仍有显著差异(p0.05)。     

镉胁迫下黑点青鳉(Oryzias melastigma)肝脏金属硫蛋白mRNA性别差异性表达研究

鱼类金属硫蛋白(metallothionein,MT)mRNA作为生物标志物已越来越多地应用到水环境重金属污染的监测中,然而重金属胁迫下鱼类MT mRNA表达是否具有性别差异性特征目前尚无相关报道。以海洋模式鱼类—黑点青鳉(Oryzias melastigma)为实验鱼类,首次克隆了其MT基因全长c DNA序列,分析了黑点青鳉MT基因和氨基酸序列特征,然后进一步研究了水体中镉暴露后雌、雄性黑点青鳉肝脏中MT mRNA表达的差异性。结果显示,黑点青鳉MT基因c DNA全长为385 bp,编码60个氨基酸,预测编码的多肽分子量为5 990 Da,含有脊椎动物MT基因特征性序列结构cys-x-cys、cys-x-x-cys和cys-x-cys-cys。镉胁迫下雌、雄性黑点青鳉肝脏MT mRNA表达结果显示,在0.8,4.0和8.0μg·L-1环境浓度的镉暴露1~7 d条件下,与对照组相比,雄性黑点青鳉在所有的不同暴露浓度和不同暴露时间的实验组中肝脏MT mRNA几乎均被显著性诱导表达;而雌性黑点青鳉只在较高暴露浓度和较长暴露时间的实验组中才被显著性诱导表达,并且MT mRNA的表达水平比雄性低得多。上述研究结果表明,在相同的镉胁迫条件下,雄性黑点青鳉肝脏MT mRNA的表达比雌性更敏感;以黑点青鳉MT mRNA作为生物标志物监测海洋环境重金属污染生物效应状况时,应选择更敏感的雄性黑点青鳉作为监测鱼类。利用生物标志物监测水环境污染物生物效应时,监测动物的性别差异是一个应当考虑的重要因素。     

城镇污水处理厂进出水对日本青鳉早期阶段亚慢性毒性效应

采用日本青鳉胚胎及幼鱼暴露评估污水处理厂进出水的综合毒性效应。水样采自广州市3个污水处理厂的进水口和出水口。96 h青鳉幼鱼急性毒性试验表明:6个水样均没有对青鳉幼鱼产生急性毒性效应。14 d胚胎暴露试验结果:3个污水处理厂的进水及1号和3号污水处理厂的出水均引起胚胎死亡,胚胎孵化率均低于70%且均与对照组产生了显著性差异(p0.05)。3个厂的进水和1号、2号厂出水的鱼苗畸形率与对照组也有显著差异(p0.05),其中3号厂进水鱼苗畸形率高达(33.73±8.94)%。而6个水样的胚胎孵化时间均与对照组无显著差异(p0.05),均在9 d左右。7 d鱼苗暴露试验结果:1、2、3号3个水厂进水的鱼苗死亡率分别是(30.16±2.75)%,(24.07±1.60)%,(37.90±4.77)%,与对照组产生明显差异(p0.05)。出水对鱼苗的致死效应明显低于进水,但出水对鱼苗的致死效应相对于对照组仍有显著差异(p0.05)。     

邻苯二甲酸二(2-乙基己)酯(DEHP)和邻苯二甲酸单乙基己基酯(MEHP)长期暴露对海洋青鳉(Oryzias melastigma)内分泌干扰效应的评价

为探讨邻苯二甲酸二(2-乙基己)酯(DEHP)和邻苯二甲酸单乙基己基酯(MEHP)长期暴露对海水生物的内分泌干扰效应及机制,将孵化后1周的海洋青鳉(Oryzias melastigma)分别暴露于DEHP(0.1 mg·L-1和0.5 mg·L-1)和MEHP(0.1 mg·L-1和0.5 mg·L-1)6个月。结果显示:DEHP显著增加了雌性和雄性海洋青鳉的肝指数,而MEHP只在高剂量时显著增加雄性青鳉的肝指数。对于雌性青鳉,DEHP暴露后肝脏雌激素相关基因ERα、ERβ、ERγ、VTG1、VTG2、ChgH和ChgL的表达水平显著上调,而对于雄性青鳉,DEHP暴露后,只有肝脏ERβ的表达水平显著上调。相比之下,MEHP暴露对雌性和雄性青鳉肝VTG和Chg基因表达无显著影响。DEHP激活了雌性和雄性青鳉的肝过氧化物增殖激活受体PPARα和PPARγ,而MEHP只在低剂量时上调了雄性青鳉PPARγ的表达。在雌性和雄性青鳉体内,VTG和Chg的表达与ERα和ERγ的表达显著相关,并且ER与PPAR也显著相关。研究表明,DEHP长期暴露可通过激活肝性激素受体调控肝雌激素响应基因(VTG和Chg)和过氧化物增殖激活受体(PPARα和PPARγ)的表达而对海洋青鳉产生内分泌干扰效应,并且显示出性别特异性。MEHP对海洋青鳉的内分泌干扰效应弱于DEHP。     

Di (2-ethylhesyl)(DEHP)和Monoethylphthalate(MEHP)长期暴露对海洋青鳉(Oryzias melastigma)内分泌干扰效应的评价

为探讨邻苯二甲酸二(2-乙基己)酯(DEHP)和邻苯二甲酸单乙基己基酯(MEHP)长期暴露对海水生物的内分泌干扰效应及机制,将孵化后1周的海洋青鳉(Oryzias melastigma)分别暴露于DEHP(0.1 mg·L^-1和0.5 mg·L^-1)和MEHP(0.1 mg·L^-1和0.5 mg·L^-1)6个月。结果显示：DEHP显著增加了雌性和雄性海洋青鳉的肝指数,而MEHP只在高剂量时显著增加雄性青鳉的肝指数。对于雌性青鳉,DEHP暴露后肝脏雌激素相关基因ERα、ERβ、ERγ、VTG1、VTG2、ChgH和ChgL的表达水平显著上调,而对于雄性青鳉,DEHP暴露后,只有肝脏ERβ的表达水平显著上调。相比之下,MEHP暴露对雌性和雄性青鳉肝VTG和Chg基因表达无显著影响。DEHP激活了雌性和雄性青鳉的肝过氧化物增殖激活受体PPARα和PPARγ,而MEHP只在低剂量时上调了雄性青鳉PPARγ的表达。在雌性和雄性青鳉体内,VTG和Chg的表达与ERα和ERγ的表达显著相关,并且ER与PPAR也显著相关。研究表明,DEHP长期暴露可通过激活肝性激素受体调控肝雌激素响应基因(VTG和Chg)和过氧化物增殖激活受体(PPARα和PPARγ)的表达而对海洋青鳉产生内分泌干扰效应,并且显示出性别特异性。MEHP对海洋青鳉的内分泌干扰效应弱于DEHP。     

Cu2+和Cd2+对日本青鳉（Oryzias latipes）早期发育阶段的急性毒性效应研究

为探究并比较淡水鱼种日本青鳉早期发育阶段对Cu2和Cd2等重金属胁迫的响应,在实验室通过半静态方式,对日本青鳉受精卵和仔稚鱼分别进行了48 h和96 h急性毒性实验.结果表明:Cu2对日本青鳉胚胎24、48 h-LC50分别为8.164 mg·L-1和6.965 mg·L-1;Cd2+对日本青鳝胚胎24、48 h-LC50分别为63.084 mg· L-1和53.093 mg ·L-1;较低浓度组Cu2+(≤1.97 mg ·L-1)时日本青鳉胚胎的发育速率快于对照组,而较高浓度组(≥3.87 mg·L-1)胚胎的发育速率则慢于对照组;与Cu2略有不同,无论浓度高低Cd2对胚胎的孵化速率均产生抑制作用;Cu2+和Cd2质量浓度分别高于1.97 mg·Lq和19.68 mg· L-1时,两种重金属离子均显著降低胚胎的孵化率(P＜0.05).Cu2对日本青鳉初孵仔鱼24、48、72和96 h-LC50分别为5361 mg·L-1、2.844 mg·L-1、2.020 mg·L-1和1352 mg·L-1;Cd2+对日本青鳉初孵仔鱼24、48、72和96 h-LC50分别为15.907 mg·L-1、10550 mg·L-1、7.986 mg· L-1和6346 mg·L-1;Cu2+对日本青鳉稚鱼24、48、72和96 h-LC50分别为5.732 mg·L-1、4.037 mg· L-1、2A98 mg·L-1和1.955 mg·L-1;Cd2+对日本青鳉稚鱼的24、48、72和96 h-LC50分别为16A19 mg·L、11.745 mg· L-1、8516 mg·L-1和6.776 mg· L-1.与其它淡水水生生物相比,日本青鳉仔稚鱼对铜和镉离子较为敏感.     

吡唑醚菌酯对不同阶段斑马鱼的毒性效应评价

为评价吡唑醚菌酯对鱼类不同生命阶段的毒性效应,以斑马鱼(Brachydanio rerio)为测试生物,测定了其对斑马鱼胚胎、仔鱼(孵化3 d和孵化12 d)和成鱼的急性毒性及对胚胎和仔鱼(孵化3 d)的发育毒性。结果表明,吡唑醚菌酯对斑马鱼胚胎、仔鱼(孵化3 d)、仔鱼(孵化12 d)和成鱼的96 h-LC50分别为0.0578(0.0540~0.0631)、0.0299(0.0282~0.0320)、0.0330(0.0310~0.0350)和0.0756(0.0692~0.0862)mg·L-1,其毒性大小依次为仔鱼(孵化3 d)仔鱼(孵化12 d)胚胎成鱼。与对照组相比,吡唑醚菌酯0.101 mg·L-1处理,可对斑马鱼胚胎24 h自主运动产生显著抑制作用;0.0609、0.0777和0.101 mg·L-1处理,可对斑马鱼胚胎48h心跳速率产生显著抑制作用;0.0609和0.0777 mg·L-1处理,可对斑马鱼胚胎96 h孵化仔鱼体长产生显著抑制作用。在供试浓度下吡唑醚菌酯暴露96 h后,均可对斑马鱼仔鱼(孵化3 d)体重和体长产生明显的抑制效应,对斑马鱼仔鱼(孵化3 d)心跳未产生明显影响。在高浓度下,吡唑醚菌酯可诱导斑马鱼胚胎产生畸形,主要包括心包水肿、卵黄囊水肿等;而对仔鱼(孵化3 d)未观察到明显的致畸效应。     

日本青鳉(Oryzias latipes)胚胎和卵黄期仔鱼对镉的 敏感性

物理化学方法对镉的监测忽略了其生物可利用性,生物监测可以有效地弥补这种不足。本研究测试了日本青鳉(Ory-zias latipes)胚胎和卵黄期仔鱼对镉的敏感性。结果表明:日本青鳉胚胎和卵黄期仔鱼的蛋白含量对镉表现出较高的敏感性,卵黄期仔鱼的蛋白含量在4μg·L-1的氯化镉暴露后就出现显著降低;氯化镉对卵黄期仔鱼脊柱畸形的EC50低于国家地表水环境质量标准规定的Ⅱ类水标准;脊柱畸形率与镉浓度之间存在的线性关系,可为定量监测镉污染提供理论依据;脊柱畸形可以在48h之内被4μg·L-1的氯化镉极显著地诱导,因此这种潜在的生物监测模型很有希望应用到水环境污染的快速预警中。通过对国内主要水体中镉污染水平的分析发现,卵黄期仔鱼的蛋白含量变化和脊柱畸形率对部分水体的镉污染可以实现生物监测。因此,利用日本青鳉胚胎和卵黄期仔鱼对低水平镉污染的高度敏感性,能够建立起1种简易廉价并且有效的水环境中低水平镉污染的生物监测模型。     

高锰酸钾及氯化锰对日本青鳉的急、慢性毒性(Toxic Effects of Potassium Permanganate and Manganese Chloride on the Early Life Stage of Japanese Medaka（Oryzias latipes）)

饮用水生产中投加高锰酸钾可能引起高锰酸钾及其副产物二价锰的毒性效应.利用日本青鳉的胚胎-幼鱼发育阶段评价了以高锰酸钾为预氧化剂的饮用水生产工艺安全性.结果表明,高锰酸钾对日本青鳉的LC50-96h为1.48mg·L-1.慢性暴露中,对孵化时间影响的最低可观察效应浓度(LOEC30d)为0.1mg·L-1;暴露于0.4mg·L-1的高锰酸钾对30d后日本青鳉的体长、体重、累计死亡率均有显著影响,但对孵化率率无显著影响.氯化锰(Mn2+)对日本青鳉的LC50-96h为550mg·L-1,对体重影响的LOEC30d为3.2mg·L-1.当高锰酸钾的使用浓度在0.5～1.5mg·L-1之间,其在滤后水中的高锰酸钾残余浓度低于检出限,而降解中间体产物Mn2+浓度小于0.5mg·L-1,均低于本文报道的LOECs数值.     

Swimming behavior of juvenile anchovies (<Emphasis Type="Italic">Anchoa</Emphasis> spp.) in an episodically hypoxic estuary: implications for individual energetics and trophic dynamics

Diel swimming behaviors of juvenile anchovies (Anchoa spp.) were observed using stationary hydroacoustics and synoptic physicochemical and zooplankton profiles during four unique water quality scenarios in the Neuse River Estuary, NC, USA. Vertical distribution of fish was restricted to waters with DO greater than 2.5 mg O₂ l⁻¹, except when greater than 70% of the water column was hypoxic and a subset of fish were occupying water with 1 mg O₂ l⁻¹. We made the prediction that an individual fish would select a swim speed that would maximize net energy gain given the abundance and availability of prey in the normoxic waters. During the day, fish adopted swim speeds between 7 and 8.8 bl s⁻¹ that were near the theoretical optimum speeds between 7.0 and 8.0 bl s⁻¹. An exception was found during severe hypoxia, when fish were swimming at 60% above the optimum speed (observed speed = 10.6 bl s⁻¹, expected = 6.4 bl s⁻¹). The anchovy is a visual planktivore; therefore, we expected a diel activity pattern characteristic of a diurnal species, with quiescence at night to minimize energetic costs. Under stratified and hypoxic conditions with high fish density coupled with limited prey availability, anchovies sustained high swimming speeds at night. The sustained nighttime activity resulted in estimated daily energy expenditure over 20% greater than fish that adopted a diurnal activity pattern. We provide evidence that the sustained nighttime activity patterns are a result of foraging at night due to a lower ration achieved during the day. During severe hypoxic events, we also observed individual fish making brief forays into the hypoxic hypolimnion. These bottom waters generally contained higher prey (copepod) concentrations than the surface waters. The bay anchovy, a facultative particle forager, adopts a range of behaviors to compensate for the effects of increased conspecific density and reduced prey availability in the presence of stratification-induced hypoxia.     

Developmental changes in the composition of myofibrillar proteins in the swimming muscles of Atlantic herring,Clupea harengus

Changes in myofibrillar protein composition during development have been investigated in the swimming muscles of the Atlantic herring Clupea harengus L. using a range of electrophoretic techniques. The main muscle-fibre type of larvae, and the fast- and slow-muscle fibres of adult fish were found to contain distinct isoforms of myosin heavy chain (MHC) and myosin light chain 2 (LC2). Larval LC2 was present as a minor component of adult fast-muscle myosin. In contrast, larval and adult fast-muscle myosin appeared to contain identical alkali light chains. Tropomyosin and troponin C were also identical in larval and in adult fast-muscle. All three muscle-fibre types contained unique isoforms of troponin T (TNT) and troponin I (TNI). Larval muscle had multiple isoforms of TNT, some of which may correspond to embryonic forms. It was concluded that although the main muscle-fibre type in larvae shares some myofibrillar proteins with adult fast muscle, it also contains characteristic isoforms of MHC, TNI, TNT and LC2 and therefore represents a distinct fibre type. The particular combination of myofibrillar proteins present at any developmental stage was found to be dependent on the rearing temperature. For example, a higher proportion of embryonic TNT isoforms were present at hatching in larvae reared at 5°C than at either 10 or 15°C. Over a period of 7 d, there was a gradual reduction in the number of TNT isoforms, but the pattern in 5°C larvae after 7 d still did not resemble that in 1 d-old larvae reared at 15°C.     

The effect of acute hypoxia on swimming stamina at optimal swimming speed in flathead grey mullet <Emphasis Type="Italic">Mugil cephalus</Emphasis>

Flathead grey mullets Mugil cephalus are commonly found in Mediterranean lagoons, which are regularly subject to high environmental variations. Oxygen is one of the factors that shows extremely high variation. The objective of this study was to test the effects of acute hypoxia exposure at two experimental temperatures (i.e. 20 and 30°C) on the stamina (time to fatigue) in M. cephalus swimming at the minimal cost of transport (i.e. optimal swimming speed; U _opt). At each temperature, a relationship was established between swimming speed and oxygen consumption (MO₂). This allowed estimation of U _opt at 45 cm s⁻¹ (~1.12 Body Length s⁻¹). Independent of temperature, stamina at U _opt was significantly reduced in severe hypoxia, i.e. at 15% of air saturation (AS). In these conditions, oxygen supply appears therefore to be insufficient to maintain swimming, even at the low speed tested here. After the stamina test, MO₂ measured in fish tested at 15% AS was significantly higher than that measured after the test in normoxia. Therefore, we suggest that in hypoxia, fish used anaerobic metabolism to supplement swimming at U _opt, leading to an oxygen debt. Since flathead grey mullet is a hypoxia-tolerant species, it is possible that hypoxic conditions less severe than those tested here may reduce stamina at low speed in less tolerant species. In addition, we suggest that testing stamina at these speeds may be relevant in order to understand the effect of hypoxia on behavioural activities carried out at low speed, such as food searching.     

Metabolic scaling,buoyancy, and growth in larval Atlantic menhaden,Brevoortia tyrannus

We measured growth of larval Atlantic menhaden, Brevoortia tyrannus in terms of mass, volume, and weight in water as well as the mass-specific activities of the metabolic enzymes citrate synthase, lactate dehydrogenase, and malate dehydrogenase. Weight in water, the force the fish must exert to maintain vertical position, increases by a factor of 18 in larvae growing from 10 to 15 mm. The weight increase coincides with the development of the larval swim bladder. The activities of all three enzymes per unit mass of fish tissue decline greatly over this time period, indicating that the fish does not further develop its aerobic and anaerobic metabolic capacity for swimming during this growth interval.     

Cd2、Hg2+、Cr6+和pb2对黑点青鳉(Oryzias melastigma)早期生活阶段的毒性效应研究

近岸海域重金属污染不容乐观,作为“一种潜在的海洋模式鱼种”黑点青鳉(marine medaka,Oryzias maelastigma)对不同重金属胁迫的响应水平却鲜有报道.为探究并比较海水鱼种黑点青鳉早期生活阶段对Cd2+、Hg2+、Cr6 +和pb2 +等不同重金属胁迫的响应,在实验室通过半静态方式,对黑点青鳉受精...     

氯化镉和敌敌畏突发胁迫下斑马鱼的行为差异

采用计算机摄像跟踪技术,以正常水体中斑马鱼的行为变化为基础,比较突发性氯化镉和敌敌畏污染胁迫下斑马鱼的个体行为(游动速度、深度、转弯次数和加速度)和鱼群行为(平均距离和分散度)的变化规律.研究结果表明:斑马鱼在两种污染物突发性胁迫下,行为反应快速且敏感,游动行为响应与污染物种类和暴露时间直接相关;两种不同类型的污染胁迫...     

Diel and seasonal changes in the distribution of fish on a southeast Brazil sandy beach

The effect of diel and seasonal changes in the distribution of fishes on a subtropical sandy beach on the southeastern coast of Brazil were studied. Seine netting was carried out on both seasonal and diel scales between July 1998 and June 1999. A total of 46 fish species was recorded, six being numerically dominant: Anchoa tricolor, Gerres aprion, Harengula clupeola, Atherinella brasiliensis, Mugil liza and Diapterus rhombeus. Seasonal changes in abundance of dominant species were detected. Species dominant in winter were Anchoa tricolor, H. clupeola and Atherinella brasiliensis; in spring, Anchoa tricolor and G. aprion; in summer G. aprion and D. rhombeus; and in autumn M. liza and H. clupeola. Overall, diel patterns did not reveal any significant trends; however, if we consider each season separately, an increase in A. tricolor abundance was recorded during the day in winter/spring, being replaced at night by H. clupeola in winter, and by G. aprion in spring. Increases in number of individuals and biomass at sunset, and decreases during the night were recorded. The winter/spring inshore/offshore movements at diel scale performed by the three most abundant species demonstrate that diel fluctuation acts more at a species-specific level than at a structural one; in summer there was no evidence of diel movements due to a heavy influx of G. aprion and D. rhombeus, which use the area throughout day and night, increasing overall abundance. Seasonal movements seems to be related to ontogenetic change in species, while diel movements in the fish assemblage seem to be more related to physiological requirements, such feeding activity of each particular species, than to physico-chemical conditions.Communicated by O. Kinne, Oldendorf/Luhe     

Otolith size-at-hatch reveals embryonic oxygen consumption in the zebrafish, <Emphasis Type="Italic">Danio rerio</Emphasis>

Otoliths have frequently been used to reconstruct growth histories in larval, juvenile and adult fish. However, there is growing evidence that otolith growth is directly determined by metabolic intensity and, consequently, only indirectly related to somatic growth. By performing measurements of oxygen consumption rate and other early life-history traits on individual eggs of zebrafish (Danio rerio), we found that oxygen consumption explained residual variance in otolith size that is not accounted for by egg size. Total oxygen consumption during the embryonic stage explained 34% of the variance in sagitta size at hatch, whereas larval size at hatch (as a proxy for growth during the embryonic period) was not significantly correlated with sagitta size. This strongly suggests that otolith growth is directly related to metabolic rate, and yields a mechanism that may explain recent observations of a link between otolith size at hatch and viability in larval fish.     

Distribution,growth and life cycle of the mesopelagic amphipod Primno abyssalis (Hyperiidea: Phrosinidae) in the southern Japan sea

The vertical distribution, growth, maturation, brood size and life cycle of the hyperiid amphipod Primno abyssalis (formerly P. macropa) were investigated using seasonal samples collected from Toyama Bay, southern Japan Sea, during the period June 1986 to September 1992. Over four different seasons of the year, P. abyssalis was most abundant in the 200 to 350 m strata at night and the 350 to 400 m strata during the day, indicating 100 to 150 m as the general distance of diel vertical movement. Some differences in vertical migrating behavior were noted among juveniles, adult males and females. Population-structure analysis revealed the occurrence of three cohorts aged 0+, 1+ and 2+ yr. Growth as body length in this species is linear with time. Estimated time to complete one life cycle is 1.8 to 2.5 yr for females, but only 0.8 yr for males. Maximum longevity is 2.8 yr. Instar analysis based on the segment number of pleopod rami indicated that newly hatched juveniles molt ten times to reach adult male, and four more times to reach adult female. Adult instar number was found to be only 1 for males and 5 for females. Ovigerous females occurred throughout the year, but the annual peak of release of juveniles from the female's marsupium is estimated to be arly March. Brood size was not correlated with female size, a maximum brood size of 214 eggs was recorded. The dry and ash-free dry weights of instars suggested that juveniles in the female marsupium, adult males, and older adult females are less active feeding or non-feeding stages. Except for the reduced growth rate and the occurrence of small, short-lived males, most characteristics of P. abyssalis are consistent with the present view of the life modes of mesopelagic animals, including linear growth in length, aseasonal reproduction, and smaller brood size coupled with larger eggs.