钱塘江口弹涂鱼繁殖特征及早期发育

对采自钱塘江口沿岸滩涂(E 30°15',N 121°27')的弹涂鱼(Periophthalmus modestus)进行了繁殖特征和早期发育研究。弹涂鱼的个体绝对繁殖力(F)为1 432～2 978粒,平均1 998粒;体长相对繁殖力(FL)为36～62粒/mm,平均45粒/mm;体重相对繁殖力(FW)为528～1 530粒/g,平均864粒/g(n=83)。雌鱼性体指标(GSI)为8.47%～25.39%,平均14.49%(n=83);雄鱼GSI为0.10%～0.57%,平均0.25%(n=76)。弹涂鱼的成熟卵为沉性黏着性卵,有黏着丝,卵径(0.42±0.01)mm(n=500);受精卵椭球形,长径(0.75±0.02)mm,短径(0.56±0.03)mm,长短径比例0.74±0.03(n=300);受精卵为端黄卵,胚盘形成于动物极,作盘状卵裂。胚胎发育可划分为29个发育时相,在(27±0.5)℃、盐度10和pH 7.8±0.3条件下,经历124.13 h孵出仔鱼,所需的积温达3 351.34 h.℃。初孵仔鱼全长(2.17±0.09)mm(n=9),器官发育完善,胸鳍和鳔等器官已形成,眼睛有大量黑色素沉积,心率达(154.33±5.87)次/min(n=20)。实验条件下,初孵仔鱼投喂褶皱臂尾轮虫(Brachionus plicatilis)培育至23 d。3～4 d龄卵黄囊已完全吸收,进入后期仔鱼;7 d龄,脊椎骨开始弯曲,消化管呈折型;11 d龄,尾鳍开始分化,尾椎骨开始上翘,上颌出现牙齿;15 d龄,下颌出现牙齿;23 d龄,尾鳍鳍条发育完整,除第一背鳍外,其他各鳍已形成。幼鱼在培育过程中出现了两个死亡高峰期,第一个高峰出现在仔鱼孵化后5～7 d龄的开口期,第二个高峰则出现在20～23 d龄的变态期。     

日本鬼鲉胚胎发育及仔、稚鱼形态学观察

对日本鬼鲉的胚胎及仔稚鱼形态发育进行观察,描述了各发育时期的发育时序和形态特征。日本鬼鲉的受精卵呈正圆球形,无色透明,无油球,平均卵径为(1.42±0.04)mm,呈浮性。在水温(22±0.5)℃,盐度31‰的条件下,历时约52h10min完成孵化。初孵仔鱼全长(3.04±0.13)mm,卵黄囊长(2.23±0.08)mm,卵黄囊高为(1.65±0.06)mm,在(21±0.5)℃水温下,仔鱼孵化后3d内营内源性营养(卵黄囊仔鱼),第4天卵黄囊完全消失,开口摄食轮虫。13d全长(7.12±0.35)mm,背鳍鳍条出现进入稚鱼早期,15d全长(7.92±0.61)mm鱼体及各鳍开始出现金黄色斑纹,25d全长(13.66±0.55)mm,整个鱼体呈黄褐色,完成变态进入幼鱼期,开始营底栖生活。同时观察了自胚胎发育至幼鱼期鱼苗体表色素分布的变化及其器官发育的形态变化。     

盐度对新吉富罗非鱼受精卵孵化和仔稚鱼活力的影响

研究了盐度梯度对新吉富罗非鱼(Oreochromis niloticus)受精卵孵化和仔鱼活力的影响。水温(28±0.5)℃下,观察比较了8个梯度的盐度(3‰、6‰、9‰、12‰、15‰、18‰、21‰、24‰)及纯净淡水(盐度为0)条件下,新吉富罗非鱼受精卵的孵化时间、孵化周期、孵化率和畸形率。同时在不同盐度条件下对4批初孵仔鱼进行耐饥饿实验,测定其不投饵存活系数(SAI)值。结果表明,新吉富罗非鱼受精卵在盐度6‰～15‰时,孵化率较高(89.0%～92.7%);盐度低于3‰和高于18‰时,孵化率较低。仔鱼生存适宜盐度3‰～15‰,最适盐度6‰～9‰。新吉富罗非鱼仔鱼在盐度0～3‰及18‰～24‰时,仔鱼的SAI值较低,不适宜仔鱼培育;盐度为6‰～15‰时,仔鱼的活力较高。仔鱼的SAI值与受精卵的孵化率呈正相关关系。     

盐度对条石鲷胚胎发育的影响

为了确定条石鲷胚胎孵化的适宜盐度,在试验水温为23.0℃～25.2℃条件下,设置了8个盐度组进行条石鲷胚胎孵化试验,研究了盐度对条石鲷胚胎发育的影响。结果表明:低盐度和高盐度对胚胎有持续性伤害,均可造成胚胎和卵黄球在卵裂期收缩而死亡,一部分胚胎在原肠期之后收缩死亡;低盐度可造成初孵仔鱼畸形率增加,主要引起仔鱼脊柱"L"形和"C"形弯曲,而高盐度可导致胚体胚孔关闭以后尾部的畸形发育;通过分析各盐度组的孵化率、仔鱼畸形率和盐度之间的关系,得出健康仔鱼比例(PHL)和盐度(S)的关系式为PHL=-0.0018S2-0.1135S-0.8853(R2=0.948),以PHL70%为适宜孵化盐度范围,以PHL90%为最适孵化盐度范围,由此确定在23.0℃～25.2℃条件下,条石鲷的适宜孵化盐度范围为21～42(PHL70%),最适为30～33(PHL90%)。     

北极茴鱼胚胎及仔鱼发育

研究对人工繁殖的北极茴鱼(Thymallus arcticus grubei)胚胎发育开展系统观察,记录分析其胚胎及仔鱼发育各时期的形态特征,旨在为北极茴鱼的人工繁育和种质资源保护提供必要的基础数据。结果显示,北极茴鱼受精卵呈圆球形,金黄色,沉性卵,未吸水卵径(2.46±0.14) mm,吸水卵径(3.14±0.18) mm,卵黄质内有多个油球。油球的数量和空间分布在胚胎发育过程中发生了规律性变化。在孵化水温(11.06±0.72)℃,溶氧8.3—9.8 mg/L条件下,历时301h完成整个胚胎发育过程,所需积温为3384.84h·℃,经历合子期、卵裂期、囊胚期、原肠胚期、神经胚期、器官形成期和孵化出膜7个阶段,共26个时期。北极茴鱼仔鱼尾鳍、胸鳍的分化和眼色素沉积在受精卵胚胎发育后期就已经完成,背鳍、腹鳍、臀鳍和脂鳍等在胚后发育过程中相继分化。其初孵仔鱼平均全长为(9.33±0.35) mm,仔鱼卵黄囊呈圆球形, 18日龄时卵黄囊和油球被完全消耗。其早期发育阶段(0—16日龄)的生长特性符合公式:y=0.0005x⁴–0.0201x³+0....     

长江口纹缟虾虎鱼胚胎发育及早期仔鱼生长与盐度的关系

研究了长江口纹缟虾虎鱼(Tridentiger trigonocephalus)胚胎发育及早期仔鱼生长与盐度的相关性。纹缟虾虎鱼胚胎发育时,盐度4与6试验组效果较好,受精率分别达(76.28±2.73)%与(74.63±5.49)%,孵化率分别达(66.95±2.99)%与(62.15±2.18)%,出膜时间分别为(228.8±5.9)h与(221.5±5.2)h,器官发育特征较明显,畸形率较低。纹缟虾虎鱼仔鱼发育时,初孵仔鱼全长(2.534±0.078)mm,卵黄囊长径(0.421±0.047)mm,短径(0.369±0.038)mm,5日龄时卵黄囊基本消失,初步形成消化器官、循环器官和运动器官等。盐度8与10水体孵育的仔鱼畸形率达5―20%,其他试验组略低。盐度4与6试验组仔鱼的器官发育速度快于其他3个试验组。盐度0―6试验组纹缟虾虎鱼仔鱼生存活力指数（SAI）为41.83―46.83,仔鱼活力较好,而盐度8―10试验组SAI值为23.43―29.13,活力较差。综合各项指标表明,在盐度0―10范围内,长江口纹缟虾虎鱼胚胎发育的适宜盐度为4―6,早期仔鱼生长的适宜盐度为2―4。     

长鳍吻鮈胚胎发育特征观察

以人工繁殖获得的长鳍吻鮈Rhinogobio ventralis受精卵为材料,观察了长鳍吻鮈胚胎发育,分析了其发育特征。结果显示:成熟长鳍吻鮈卵的卵径为1.52 mm±0.07 mm,吸水膨胀后卵膜径达到6.44 mm±0.08 mm,为卵径的4.2倍。在水温17.35℃±0.24℃条件下,长鳍吻鮈受精卵历时73.50 h孵化出膜,出膜仔鱼全长6.25 mm±0.11 mm,从受精到孵化出膜的积温为1275.44℃·h。根据胚胎发育过程形态特征,将长鳍吻鮈胚胎发育过程分为受精卵、卵裂、囊胚、原肠、神经胚、器官发生和出膜7个阶段26个时期。结果表明:长鳍吻鮈受精卵吸水后的卵膜径、出膜前胚体蜷曲程度等可作为长鳍吻鮈早期发育阶段形态学鉴定的依据。长鳍吻鮈胚胎发育阶段的积温高于一些产漂流性卵鱼类。     

盐度及pH对星斑裸颊鲷受精卵孵化和仔鱼耐饥饿能力的影响

比较观察了不同盐度(0、5‰0、10‰、15‰、20‰、25‰、30‰、35‰、40‰和45‰)及不同pH(5.5、6.0、6.5、7.0、7.5、8.0、8.5、9.0和9.5)条件下,星斑裸颊鲷(Lethrinus nebulosus)受精卵的孵化时间、孵出期、孵化率、畸形率及一定时间内(24h和48h)仔鱼成活率,并且在以上盐度和pH条件下对星斑裸颊鲷初孵仔鱼进行耐饥饿试验,测定其不投饵存活指数(survival activity index,SAI).结果表明,只有SAI值大于3的星斑裸颊鲷仔鱼才有可能被进一步培育成苗,低于3的将在数天内死亡;星斑裸颊鲷受精卵孵化的适宜盐度范围是10‰～45‰,最适宜盐度范围15‰～40‰,适宜pH是6.5～9.0,最适宜pH范围7.0～8.5;初孵仔鱼生存的适宜盐度范围是10‰～40‰,最适宜盐度范围20‰～25‰,适宜pH是5.5～9.5,最适宜pH范围7.0～8.5.     

温度和盐度对中华多刺鱼胚胎发育过程的影响

2006年3-5月,在北京怀柔水库入库河流怀九河的西四渡河河段,采集性成熟的中华多刺鱼(Pungitius sinensis),人工干法授精获取受精卵,观察并记录受精卵的胚胎发育历程;设置温度和盐度梯度,观察温度和盐度对中华多刺鱼胚胎发育过程的影响。结果表明:北京地区的中华多刺鱼胚胎发育的起始温度(生物学零度)为4.7℃,适宜的发育水温为14.0℃-16.0℃,与中华多刺鱼繁殖盛期(4月中下旬)自然水体的水温相近;平均水温14.0℃时,中华多刺鱼完成胚胎发育约需183h;水温升至22.5℃时,胚胎的孵化率仅为22.2%;水温升至25.0℃时,受精卵不能孵化,此温度应是中华多刺鱼胚胎发育温度的上限。实验表明,北京地区中华多刺鱼的胚胎对盐度的耐受力较为有限,在与自然水体相同的盐度下(0‰)其孵化率接近100%;随着盐度的升高,孵化率降低,8‰盐度时,仅有56%的受精卵孵化;至20‰时,受精卵全部死亡,此盐度应为中华多刺鱼胚胎发育的盐度上限。     

白斑狗鱼胚胎和仔鱼发育的研究

白斑狗鱼 (EscoxluciusLinnaeus) ,卵圆球形 ,呈金黄色 ,直径为 1.9— 2 .2mm ,具黏性。在 5— 11℃的温度下 ,受精卵历时 185h 18min发育后孵出 ,所需总积温为 2 6 4 1 37℃ ,胚胎发育可划分为 6个阶段 ,33个发育时期。初孵仔鱼全长 7 0— 7 7mm ,从孵出到各鳍形成需 2 1d。胚胎发育各期及仔鱼的主要形态特征均被描述     

Responses of embryonic stages of the estuarine mud crab,Macrophthalmus hirtipes (Jacquinot), to salinity

Females of the estuarine mud crab, Macrophthalmus hirtipes (Jacquinot, 1853) (Ocypodidae) carrying newly-deposited eggs were maintained in salinities of 11‰, 18‰, and 36‰ at 10°C. In 11‰ salinity eggs swelled more than in the other salinities; embryonic development was retarded; and eggs did not hatch. In 18‰ and 36‰, rates of development were generally similar and successful hatching occurred after approximately 75 days. However, late-stage eggs in 18‰ were significantly (P<0.001) larger than those in 36‰, even though initial egg volumes were the same. Zoeae were morphologically similar, except that the dorsal spine was significantly (P<0.001) longer in 36‰ compared with 18‰.     

Spawning frequency, fecundity, egg weight and spawning type of silver pomfret, Pampus argenteus (Euphrasen) (Stromateidae), in Kuwait waters

Silver pomfret, Pampus argenteus, were collected by fishing with drift gillnets on one spawning ground in Kuwait waters during 1998–2000. Fish size frequency, sex ratio, maturation cycle, spawning frequency, fecundity and egg weight were assessed. The length–weight relationship differed between sexes whereby females were significantly bigger than males. Spawning started in mid‐May and continued until early October. During this time the water temperature ranged from 26.0 to 32.8°C, salinity was ? 39.0‰ and water depth ranged between 5 and 12 m. Large females spawned earlier than young spawners and the overall percentage of males during the spawning period was 70.3%. Spawning occurred after 13.00 h, with peak spawning between 15.00 and 18.00 hours during outgoing tide. Mean daily spawning frequency amounted to 63.2%. Spawning activity was found to be associated with the lunar cycle and spawnings were concentrated during the first and third quarters of the moon period, indicating a semilunar reproduction cycle. It was concluded that a female would spawn at least six times during the season. No change was observed in relative fecundity during the peak spawning season (June–August). Average relative batch fecundity was 176.3 eggs g^?1 somatic weight (SW), corresponding to a relative total fecundity of 1058 eggs g^?1 SW, which is 1.5 times higher than estimates obtained from counting the standing stock of oocytes. Bigger fish produced heavier eggs and the egg weight decreased as the spawning season progressed. Based on gonadal cycles, oocyte size frequency distribution and total fecundity, we concluded that silver pomfret is a multiple batch spawner with indeterminate fecundity.     

Thermohaline tolerance and embryonic development in capelin eggs (Mallotus villosus) from the Northeast Atlantic Ocean

Capelin (Mallotus villosus) displays alternative reproductive modes throughout its circumpolar distribution. This predicts divergent thermohaline tolerance of eggs because they are incubated in either a steady offshore or variable intertidal environment. We investigate herein thermohaline tolerance of eggs from the offshore spawning Barents Sea capelin. Subsequently, we compare our data with those previously published on other offshore and intertidal spawning capelin populations across the Northeast Atlantic Ocean, with the aim of determining possible patterns in the thermohaline tolerance of eggs from the alternative reproductive modes. In a 2?×?4 factorial design various combinations of salinities and temperatures had only negligible effect on the survival of eggs until first hatch. The embryonic development rate from fertilisation until first hatch across populations and between the two reproductive modes suggested non-local thermohaline tolerance towards the physical factors during development. Finally, no differences were observed in salinity tolerance from fertilisation to first hatch between populations representing different reproductive modes. The present findings demonstrate wide thermohaline tolerance of capelin eggs regardless of population origin and reproductive mode.     

Roles of environmental cues for embryonic incubation and hatching in mudskippers

Reproduction on mudflats requires that eggs are protected from different environmental challenges during development and hatch when environmental conditions are favorable for survival of juveniles. Mudskippers are air-breathing, amphibious gobies of the subfamily Oxudercinae, and one of a few vertebrates that reside on mudflats. They excavate burrows in mudflats and deposit eggs in them. However, these burrows are filled with extremely hypoxic water, in which eggs could not survive. To secure embryonic development within their burrows, the burrow-guarding parental fish (a male or mating pair) store fresh air in an egg chamber, located near the bottom or at mid-depth in a burrow, by transporting mouthfuls of air during each low tide. The Japanese mudskipper, Periophthalmus modestus, is the best-studied species regarding reproductive strategies. The air-supplying behavior appears to be predominantly governed by the oxygen levels within egg chambers, but also by some other factor that is possibly related to the tidal cycle. When embryonic development is complete, the burrow-guarding male P. modestus removes the air from the egg chamber and releases the air outside the burrow on a nocturnal rising tide. Consequently, the tide floods the egg chamber and induces hatching. Because P. modestus eggs only have a 5-6 day window for hatching competence, the male's initial selection of the position for the burrow in the intertidal zone and the timing of spawning relative to the tidal cycle are both important factors in hatching success. This is particularly crucial for those burrows in higher intertidal zones, which may be reached only by spring high tides. Not much is known for other mudskippers, but it is likely that they also employ similar reproductive strategies. The objective of this review is to summarize available information on reproductive strategies of mudskippers, and to discuss future directions to better elucidate mechanisms and adaptive significance for the reproduction of mudskippers. Further comparative studies with both mudskippers and other oxudercine gobies dwelling mudflats could shed new light on how vertebrates solved problems of reproduction when they expanded habitats to environments in an air-water interface.     

Habitat segregation and cryptic adaptation of species of Periophthalmus (Gobioidei: Gobiidae)

A study was conducted on the habitat distribution of four sympatric species of Periophthalmus (the silver‐lined mudskipper Periophthalmus argentilineatus, the slender mudskipper Periophthalmus gracilis, the kalolo mudskipper Periophthalmus kalolo and the Malacca mudskipper Periophthalmus malaccensis) from northern Sulawesi. Molecular phylogenetic reconstructions based on one mtDNA marker (16S) were used to validate the morphological taxa, identifying five molecular clades. Periophthalmus argentilineatus includes two molecular species, which are named Periophthalmus argentilineatus clades F and K. Multivariate direct gradient analysis show that these species form three distinct ecological guilds, with the two molecular species occurring in different guilds. Periophthalmus clade F is ecologically eurytypic; Periophthalmus clade K and P. kalolo are prevalent in ecosystems isolated by strong oceanic currents and at shorter distances from the sea; P. gracilis plus P. malaccensis are prevalent in ecosystems connected by shallow coastal waters, in vegetated habitats at larger distances from the sea. This indicates for the first time that mudskipper species exhibit a range of adaptations to semiterrestrialism not only within genera, but even within morphospecies, delineating a much more complex adaptive scenario than previously assumed.     

Crayfish freshwater adaptation starts in eggs: ontogeny of osmoregulation in embryos of Astacus leptodactylus

Osmoregulation was studied throughout the embryonic development of Astacus leptodactylus. Egg-carrying females were held in freshwater (FW) and in three dilute seawater media (200, 400, 600 mosm kg(-1), 6.8, 13.6, 20.4 per thousand salinity). In FW, changes in peri-embryonic fluid (PEF) and (when available) embryonic hemolymph osmolality were followed from newly-laid eggs to hatching (for an embryonic eye index, EI, of 430-450 microm) and in first-stage juveniles. The PEF and/or hemolymph osmolality remained stable at about 360-380 mosm kg(-1) from early to late (EI 410 microm) embryos; it decreased prior to hatching (EI 420 microm) and in newly-hatched juveniles, down to 290 mosm kg(-1). Artificial opening and removal of the egg membranes, followed by direct exposure to FW, demonstrated that the ability to hyper-osmoregulate, and consequently to survive, in FW appears in embryos with EI > or = 410 microm, i.e., only a few hours or days before hatching. Following a transfer to the dilute seawater media, the PEF/hemolymph osmolality increased slowly over 18-20 days and became isosmotic with the external media at 13.6 and 20.4 per thousand. The embryos died at EI 380-395 microm in these media, and only at 6.8 per thousand was the development completed until successful hatch. These results demonstrate that (1) the embryos become able to osmoregulate in FW shortly before hatching, (2) the embryos are osmo-protected in the eggs during their development, (3) embryonic development and hatching are possible up to a salinity of 7 per thousand. These results are discussed in relation to freshwater adaptation of crayfish.     

Functional anatomy and kinematics of the oral jaw system during terrestrial feeding in Periophthalmus barbarus

Cover illustration . Skeletal body plan of the Atlantic mudskipper (Periophthalmus barbarus) from a lateral view. The mudskipper uses its fish feeding apparatus to successfully feed in the terrestrial environment. Each color represents a unit of fused or otherwise firmly interconnected ossified structures. Presented from a micro CT‐scan using Amira (FEI Visualization Sciences Group). See Michel et al. (pp. 1145–1160 10.1002/jmor.20291 ) for further details.     

Effect of salinity on the embryonic development of Macrobrachium acanthurus (Decapoda: Palaemonidae)

The effect of salinity level on the embryonic development of Macrobrachium acanthurus was analyzed under laboratory conditions, considering characteristics of the egg (size, volume, and water content) and of the embryo (eye index). The experimental design was completely randomized, with five repetitions (ovigerous females) per treatment (0, 10, 17 and 20 ppt). During embryonic development, two eggs per female were taken daily for analyses of size, volume, water content, and eye index. Our results showed that salinity of 20 ppt leads to death and/or abortion of the embryo in all females. The size, volume and water content of eggs increased according to embryonic development, providing space in the egg for formation and organization of embryo. Salinity affected these egg characteristics, causing water loss to the hypertonic medium. Neither the duration of embryonic development nor embryo formation were affected by saltwater content. The results of the present study indicate that ovigerous females of M. acanthurus can survive in freshwater rivers as well as in low-salinity environments during incubation period and the successful larval development is not likely to rely on female migrating to estuaries. Larvae can easily be incubated in freshwater and complete development at higher salinities after hatch.     

牛蒡抗虫活性及抗虫成分的初步研究

在水温(23±0.5)℃、pH 7.0～8.0、溶解氧＞5 mg· L-1的条件下,研究孵化过程中不同盐度对拟目乌贼胚胎发育和孵化率的影响.结果表明,拟目乌贼卵透明略带奶油色,近椭圆形,短径为0.596～1.758 cm,长径为1.452～3.136 cm,刚产出的卵重约2g;孵化完成时,卵膜内的重量达到4.5g.在盐度为28‰时,经过28～30 d孵化,卵的短径和长径平均分别增加了0.601、0.615 cm,孵化率为57.0％;盐度为23‰时,卵的长径和短径也相应增加,增幅分别为0.567、1.263 cm,孵化率为13.5％;盐度为33‰时,经过28～30 d孵化,卵短径平均增长0.150 cm,而长径却缩短了0.141 cm,孵化率为9.5％;在盐度为13‰、18‰、38‰和43‰条件下,胚胎停止发育,孵化率为0.结果表明,拟目乌贼属于狭盐性种类,盐度变化对拟目乌贼胚胎发育和孵化有直接影响.     

Phylogeography of Walton’s Mudskipper,Periophthalmus waltoni Koumans, 1941 (Perciformes: Gobiidae), from the Persian Gulf and Gulf of Oman

Mudskippers are amphibious air breathing fish with terrestrial adaptations in contrast to entirely aquatic fish. They are adapted to living on mudflats and show morphological, physiological, and behavioural features that could affect their phylogeny and phylogeography. A comparative genetic analysis was carried out on 100 specimens of the mudskipper Periophthalmus waltoni Koumans, 1941 from eight different sites along the coast of the Persian Gulf and Gulf of Oman. Phylogeographic inference based on two mitochondrial markers (Cyt b and D-loop) suggests that P. waltoni populations are divided into two well-divergent clades western and eastern. This is likely related to the geohydrological history of the area during the last Pleistocene glaciations. The regional phylogeographies are apparently also influenced by ecological and geographical barriers such as salinity, water current, and the geographic position of the Strait of Hormuz.