不同水温对青鱂鱼胚胎发育的影响

研究了孵化水温对青鱂(Oryzias latipes)胚胎发育的影响。结果表明,在19.69~36.03℃范围内,青鱂胚胎都能孵化出仔鱼,孵化时间随水温上升而缩短。26.03~33.90℃是其胚胎发育的最适温度;其中,在27.58℃孵化率最高,达到83%,仔鱼成活率达到90.9%。当水温低于17.64℃,青鱂胚胎发育极其缓慢,至47d只有1尾仔鱼孵出;当水温高于38.67℃,其胚胎不能孵出仔鱼。青鱂胚胎发育的理论有效积温为112.62℃.d,发育阈温度为17.55℃。     

The effect of water flow on spawning in the medaka, Oryzias latipes

The effect of water flow on spawning was investigated in the medaka, Oryzias latipes. Spawning rate decreased under water flow exposure and recovered when water flow stopped. Spawning of medaka was suppressed by water flow much lower than that critical velocity for fish to swim.     

Effects of thyroid hormone on gonadotropin-induced steroid production in medaka,Oryzias latipes,ovarian follicles

Blood and ovarian samples were collected at intervals of 4h prior to spawning time from medaka (Oryzias latipes) that were maturationally synchronized with artificial photoperiod (14h light: 10h dark). Plasma estradiol-17β (E₂) levels increased rapidly from 16h before spawning and peaked at 8h before spawning. Follicle-enclosed oocytes (ovarian follicles) at different stages of development were isolated from the ovaries and used to study the in vitro effects of thyroid hormone (triiodothyronine; T₃) on pregnant mare serum gonadotropin (GTH)-induced E₂ production. GTH at a concentration of 100 IU/ml stimulated E₂ production by ovarian follicles collected between 32 and 16h before spawning. At 32h before spawning, T₃ (5 ng/ml) administered along with GTH (100 IU/ml) resulted in a 3.5 fold increase in E₂ production, compared with GTH administered alone. These results suggest that T₃ can act on ovarian follicles directly to modulate GTH-stimulated E₂ production in the medaka.     

视黄酸信号通路在青鳉精原干细胞体外增殖与分化中的作用

为探究视黄酸(Retinoic acid, RA)在鱼类精原干细胞(Spermatogonial stem cells, SSC)增殖与分化中的作用,本研究首先以三荧光报告载体pGRY(延伸因子1α启动子驱动组蛋白H2B-绿色荧光融合蛋白、减数分裂联会复合体蛋白3(Scp3)启动子驱动嘌呤霉素红色荧光融合蛋白、精蛋白启动子驱动黄色荧光蛋白)转染青鳉精原干细胞系SG3,获得稳转细胞SG3-pGRY,然后分别在2D与3D培养条件下检测RA信号对其增殖与分化的影响。结果显示,稳转细胞SG3-pGRY的红色荧光可监测细胞内源性Scp3的表达,且细胞仍保持干性及分化潜能,表明其可用于监测细胞分化状态。在2D培养条件下,即在细胞培养板中待细胞生长密度约90%就进行传代培养,RA可显著抑制细胞增殖,其受体α、β、γ泛抑制剂BMS493可促进细胞增殖;第48 h,RA处理可下调细胞多能性相关基因pou5f3、klf4表达,上调减数分裂相关基因dazl表达,但对其他减数分裂相关基因如scp3表达无明显影响;第8 d,处理组及对照组均未能观察到红色荧光,这与已有报道RA处理体外培养小鼠SSC可显著促进Scp3表达,并进入减数分裂I期偶线期的研究结果明显不同。在3D培养条件下,即用96孔球形低吸附微量培养板进行培养,48 h后细胞成球状体聚集生长,RA、 BMS493处理组、对照组在48 h后均观察到明显红色荧光,减数分裂相关基因表达与2D相比显著上调;第8 d与34 d,RA处理组减数分裂相关基因表达均显著高于对照组,而BMS493处理组低于对照组。综上,RA信号可抑制SG3增殖,促进其分化,但不是诱导细胞发生减数分裂的关键分子。本研究不仅为鱼类SSC分化相关研究提供了良好研究模型,而且促进了我们对于RA信号在鱼类SSC增殖与分化中作用的深入认识。     

Multiple paternity,reproductive skew and correlates of male reproductive success in a wild population of the Trinidadian guppy

Abstract – In most species, males have a higher reproductive potential than females, leading to skewed reproductive success, particularly in mating systems where pre‐ or postcopulatory sexual selection reinforces inequality in male mating success. We investigated multiple paternity, reproductive skew and correlates of male reproductive success in a wild population of the Trinidadian guppy (Poecilia reticulata). We used nine microsatellite loci to assess the frequency of multiple paternity, number of sires per brood and reproductive skew. Across broods, the frequency of multiple paternity was high with 94% of broods having multiple sires (range: 1–5), resulting in a reproductive skew of 0.14. Variation in male reproductive success was high (range: 0–14 offspring per male), suggesting that there is considerable opportunity for sexual selection. Next, we examined correlations between male reproductive success and sexual coloration, sperm velocity and gonopodium length. Relative area of orange, black, iridescent and total coloration, and sperm velocity were not correlated with reproductive success. However, gonopodium length explained 14% of the variation in reproductive success, suggesting that gonopodium length is likely a sexually selected trait. We discuss these findings in the light of other studies that genetically dissect joint‐sex parentage and examine correlates of male reproductive success in wild populations.     

An astacin-like protease, alveolin, is released from cortical vesicles and induces changes in egg envelope proteins during fertilization of medaka (Oryzias latipes) eggs

Upon fertilization, two major protein groups, ZI-1,2 and ZI-3, composing the egg envelope are polymerized to insoluble forms via temporary formation of 132 kDa and 61–62 kDa intermediate proteins. We have shown that an astacin-like protease, `alveolin' is released from cortical vesicles into the perivitelline space after egg activation and induces initiation of the polymerization of egg envelope proteins. To clarify initial reactions of the polymerization, the primary structure of the 132 kDa protein was analyzed.     

Nest site characteristics and male reproductive success in the upland bully, Gobiomorphus breviceps (Eleotridae)

Abstract— The characteristics of male upland bullies ( Gobiomorphus breviceps ) and their nest sites were examined in two New Zealand streams as possible determinants of male reproductive success. There was no association between male size, nest site characteristics (depth, distance to shore, river velocity, nest rock size), and male reproductive success. Similarly, the male's parasite load had no detectable influence on reproductive success. Multiple regression analysis revealed that no combination of factors could explain the wide variation in male reproductive success. It may be that the unpredictable nature of the stream habitats of bullies has favored reduced choosiness in females, which could lead to an absence of correlations between male and nest characteristics and reproductive success.     

雌雄半滑舌鳎脑垂体基因表达差异研究

为研究半滑舌鳎雌雄个体大小和生长速度差异悬殊的分子机理,采集来自同一亲本、同一发育阶段的半滑舌鳎雄鱼和雌鱼脑垂体,分别与Affymetrix的斑马鱼基因芯片杂交,筛选差异表达基因。芯片杂交结果显示二者共有1 051个基因检测到明显的杂交信号,其中上调基因486个,下调基因561个。进一步比较雄鱼和雌鱼杂交信号的比值(Ratio值),有39个基因的Ratio值小于0.6或大于1.5,其中sh3gl1b、meis2.1、acta1、Noxa、slc25a5这5种上调基因和col1a2、klf7、acta2这3种下调基因可能与半滑舌鳎雌雄生长差异相关。这一结果为深入研究半滑舌鳎雌雄性别分化与生长调控机制提供了新思路。     

Composition and location of simulated lake-shore redds influence incubation success in kokanee, Oncorhynchus nerka

Abstract  Methods for improving spawning habitat for lakeshore spawning kokanee, Oncorhynchus nerka (Walbaum), were explored by quantifying incubation success of embryos exposed to three substrate treatments in Lake Pend Oreille, Idaho, USA. Substrate treatments included no modification that used existing gravels in the lake (EXISTING), a cleaned substrate treatment where existing gravels were sifted in the water column to remove silt (CLEANED) and the addition of new, silt-free gravel (ADDED). Incubation success was evaluated using Whitlock–Vibert incubation boxes buried within each substrate treatment that contained recently fertilised embryos. Upon retrieval, live and dead sac fry and eyed eggs were enumerated to determine incubation success (sac fry and eyed eggs × 100/number of fertilised embryos). Incubation success varied significantly among locations and redd treatments. In general, incubation success among ADDED redds (0.0–13.0%) was significantly lower than that for EXISTING (1.4–61.0%) and CLEANED (0.4–62.5%) redds. Adding new gravel to spawning areas changed the morphometry of the gravel-water interface and probably exposed embryos to disturbance from wave action and reduced embryo survival. Moreover, efforts to improve spawning habitat for lakeshore spawning kokanee should consider water depth and location (e.g. protected shorelines) as important variables. Adding clean gravel to existing spawning areas may provide little benefit if water depth or lake-bottom morphometry are altered.     

Size-related factors causing individual variation in seasonal reproductive success of fluvial male Dolly Varden (Salvelinus malma)

Abstract– Reproductive activities of individually identified fluvial Dolly Varden ( Salvelinus malma ) were observed during a breeding season in a small stream. Males and females both established dominance hierarchies based on body size. Females spawned from late October to late November, with no apparent peak, and larger females spawned earlier than small ones. Males competed for access to females by adopting two types of mating tactics: pairing and sneaking. The tactic used depended on the male's position in the dominance hierarchy of the breeding group. Seasonal reproductive activity and mating success of males were positively correlated with body size, with only the largest male monopolizing most of the mating opportunities, and the small males were rarely successful in mating. Smaller males, however, lost as much weight as large males during the breeding season. Females preferred the largest male in the breeding group as a mate, while males courted females of any size. It is suggested that the polygynous mating pattern is a consequence of size-related differences in competitive ability among males, and the degree of monopolization is affected by both the temporal distribution and the spawning tactics of the females.     

Life-history of the flagfin shiner, Pteronotropis signipinnis, from a blackwater stream in southeastern Mississippi

Abstract – Flagfin shiners, Pteronotropis signipinnis , were collected from Sweetwater Creek, a second-order blackwater stream in southeastern Mississippi, during each month of 1996. Analysis of length frequency histograms indicated a life span of 1 to 2 years. Sex ratio was not different from a 1:1 ratio. Adult males were larger and more heavily pigmented near the abdomen than females. Females were reproductive from April to mid-August. All females attained sexual maturity by 27 mm SL and produced multiple clutches of ova. Clutch size varied from 12 to 101 ova and was correlated with SL. Mean mature oocyte diameter was 0.88 mm (range 0.76–0.96). Despite the relationship between clutch size and body size, P. signipinnis may be selected to invest in early reproduction rather than growth. This idea is supported by the small size at maturity in this species and is consistent with an opportunistic life-history strategy. ^Note     

Determining home range,changes in habitat use with time,and the threats to an endangered freshwater turtle (Rafetus euphraticus) in Turkey

1. The Euphrates softshell turtle (Rafetus euphraticus) is the most threatened chelonian species in the Middle East, where it is endemic to the Tigris and Euphrates basins. Since the ecology of this species is little known, it is difficult to plan any reliable action for its correct management and conservation.
2. To enhance the scientific knowledge on R. euphraticus, and to establish a science-based management strategy, a detailed investigation was undertaken on the distribution, habitat, activity and home range of R. euphraticus in Turkey. The previous distribution records in Turkey are for the 1990s; thus, this study is the first comprehensive field research on the species after nearly 3 decades.
3. There was a significant sexual size dimorphism in the Turkish population, with males larger than females.
4. Four individuals were radiotracked for 1 year. The mean home range was highly variable depending on how it was calculated, but that of males was considerably greater than that of females by all methods used.
5. A quantitative evaluation was made of habitat change with time. The land cover classes potentially available to turtles in the Euphrates River basin increased by more than 100% between the 1990s and 2018: 92% of this enhancement was derived from water bodies and coastal lands.
6. Fifteen dams have been built in the lower part of the basins in the last 30 years. In addition, continuing human interactions have caused the fragmentation or destruction of suitable habitats for R. euphraticus.
7. The factors threatening R. euphraticus were assessed and a conservation action plan was developed. Some objectives such as monitoring and creating awareness of this action plan have been met while others are still waiting to be achieved.

     

Reproductive success of Atlantic salmon (Salmo salar) mature male parr in a small river,the Nivelle: influence of shelters

Grimardias D, Merchermek N, Manicki A, Garnier J, Gaudin P, Jarry M, Beall E. Reproductive success of Atlantic salmon (Salmo salar) mature male parr in a small river, the Nivelle: influence of shelters.
Ecology of Freshwater Fish 2010: 19: 510–519. © 2010 John Wiley & Sons A/S Abstract – The breeding activity of a small population of Atlantic salmon (Salmo salar L.) was monitored on the Nivelle River in southwest France to estimate the overall contribution of mature male parr and the numbers involved in egg fertilisation. In the twelve redds sampled, 563 eggs were collected for parental assignment and the physical habitat was characterised to investigate the possible relationship between parr reproductive success and habitat complexity. The overall contribution of mature male parr was particularly high (87%, one of the highest estimates ever reported). Concerning habitat complexity, granulometry and shelter diversity were correlated with the number of parr breeders contributing to egg fertilisation in each redd. A complex habitat increased multiple paternity, which could affect the effective size and genetic variability of small salmon populations.     

Quality of testicular semen of the African catfish Clarias gariepinus (Burchell, 1822) and its relationship with fertilization and hatching success

Quality differences of testicular semen of the African catfish, Clarias gariepinus, and their influence on fertilization and hatching success were investigated. In accordance with an earlier study, two semen types of the African catfish were distinguished according to testicular maturity stage. Semen type I derived from males with white mature testes whereas type II semen derived from males with grey, partly mature testes. Semen volume, sperm cell concentration and seminal plasma pH was significantly higher in type I semen than in type II semen, while sperm motility was similar. Similar fertilization percentages were obtained with semen type I and semen type II. However, the hatching percentage was higher and the percentage of deformed hatched larvae was lower for type I semen. There were significant (P<0.01) positive correlations between sperm motility and fertilization percentage, seminal plasma pH and hatching percentage and a negative correlation between seminal plasma pH and percentage of deformed larvae. Therefore seminal plasma pH and sperm motility are useful to predict semen quality of the African catfish.     

Age, differential growth and mortality rates in unexploited populations of Florida gar, an apex predator in the Florida Everglades

Abstract  Florida gar, Lepisosteus platyrhincus DeKay, were sampled in two canal systems in south Florida during 2000–2001 to estimate age, growth and mortality as part of the Everglades ecosystem-restoration effort. Tamiami (C-4) and L-31W canal systems had direct connections to natural wetlands of the Everglades and harboured large Florida gar populations. Of 476 fish aged, maximum ages were 19 and 10 years for females and males, respectively. Maximum sizes were also larger for females compared with males (817 vs 602 mm total length). Overall, female Florida gar from both Tamiami and L-31W were larger at age than males from L-31W that, in turn, were larger at any given age than males from Tamiami. Females also had lower rates of annual mortality ( Z  = 0.21) than males from L-31W ( Z  = 0.31) or males from Tamiami ( Z  = 0.54). As a large and long-lived apex predator in the Everglades, Florida gar may structure lower trophic levels. Regional- and sex-specific population parameters for Florida gar will contribute to the simulation models designed to evaluate Everglades restoration alternatives.     

The morphology–diet relationship and its role in the coexistence of two species of annual fishes

Annual fishes, which inhabit temporary pools with extremely limited habitat complexity and niche availability, display remarkable sexual dimorphism, rapid growth, and enormous investment into reproduction, all traits associated with high energy requirement. This study tests three hypotheses for two syntopic annual fishes (Austrolebias minuano and Cynopoecilus fulgens) found in six wetlands of southern Brazil: (i) considerable morphological differences result in low dietary overlap, (ii) sexual dimorphism in both species leads to intraspecific diet segregation, and (iii) dietary richness increases during ontogenetic development, and is narrower in C. fulgens than A. minuano due to morphological limitations imposed by reduced size. The diet of 82 A. minuano and 211 C. fulgens individuals was analyzed over two annual cycles. The morphology was characterized by 26 measurements covering the entire body of both species. There was no evidence of morphological specialization related to food competition and the diet of A. minuano and C. fulgens showed high overlap. High food availability, high predator abundance, and high connectivity of adjacent wetlands are likely the main mechanisms allowing coexistence of both species. Within species, sexual dimorphism did not result in a decrease in dietary overlap, which reinforces the idea that morphological differences between the sexes did not evolve as a mechanism to decrease food competition. Large A. minuano did not have a more diverse diet than the smaller C. fulgens; however, increase in body size allowed both species to ingest larger prey. Morphological variability in both species was mainly related to ontogenetic development and reproduction.     

Prespawning migratory behaviour and spawning success of sea-ranched Atlantic salmon, Salmo salar L., in the River Gudenaa, Denmark

The migratory behaviour of sea-ranched Atlantic salmon, Salmo salar L., was analysed by radio-telemetry in the River Gudenaa, Denmark. The main objectives were to: (1) estimate mortality of returning adults through the fjord; (2) observe rate of progression and migratory pattern in the fjord and river; and (3) record whether spawning occurs in the river. Forty-two returning salmon (19 males and 23 females of total body length from 60–97 cm) reared and released as smolts, were caught and equipped with external radio transmitters in the outer estuary of the River Gudenaa in 1994 and 1995. Of the tagged salmon, 18 (43%) were caught in the estuary, four (10%) were not recorded after release and 20 (47%) entered the river. The mean rate of progression through the fjord was 7.6 km d−1 (range 1.4–18.2) in 1994 and 5.4 km  d−1 (range 1.6–17.1) in 1995. Eleven salmon were alive at the onset of the spawning period. Eight were retrieved dead from the river during or after the spawning period; four with empty gonads assumed to be successful spawners, and four with intact gonads. In 1994, unsuccessful spawners (found dead with intact gonads) entered the river earlier and had a longer total migration distance in the river compared to successful spawners. This suggests that spawning success of sea-ranched salmon is associated with time of river entry and river migration length.     

Effects of Estradiol and Testosterone on the Expression of Growth‐related Genes in Female and Male Nile Tilapia,Oreochromis niloticus

Nile tilapia exhibits strong sexual growth dimorphism. The potential role of sex steroid hormones in sexual growth dimorphism is not fully understood. We investigated the effects of estradiol (E₂) and testosterone (T) on growth rate, plasma sex hormones, and expression of growth hormone (GH)‐insulin‐like growth factor (IGF) axis genes and muscle regulatory factor (MRF) genes in female and male Nile tilapia. The results revealed that serum concentrations of E₂ and T were significantly higher after correlative injection (P < 0.05). Compared to male fish, female fish had lower growth rates. E₂ increased growth performance in females with no significant effects on males, whereas T significantly increased growth performance in males, with no significant effects on females. In females, E₂ significantly increased expression of ghr1, ghr2, igf1, and igf2, while T decreased igf2 and increased ghr1 and ghr2 expression. In males, T increased expression of igf1, igf2, ghr1, and ghr2, and E₂ decreased expression of igf1, ghr1, and ghr2. Additionally, E₂ and T enhanced the expression of MRF genes (myod1, myod2, myog, and myf5) in female and male fish, respectively. The results suggest that sex steroid hormones play a role in sexual growth dimorphism by regulating the expression of GH‐IGF axis and MRF genes.