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1.
Sperm cryopreservation for fishes with internal fertilization is essentially unexplored although many species of these fishes are valuable biomedical research models. To explore methods for sperm cryopreservation within the live-bearing genus Xiphophorus, this study used X. helleri to evaluate the effects of cryoprotectant, osmotic pressure, cooling rate, equilibration time, and sperm-to-extender ratio. Sperm motility and survival duration after thawing showed significant differences among different cryoprotectants with the highest motility at 10 min after thawing obtained with 14% glycerol. With subsequent use of 14% glycerol as the cryoprotectant, the highest motility after thawing was observed with Hanks' balanced salt solution (HBSS) at 300 mOsmol/kg. Samples cooled from 5 to -80 degrees C at 20 degrees C/min yielded the highest post-thaw motility although no significant difference was found in the first 4h after thawing for cooling rates across the range of 20-35 degrees C/min. Evaluation of equilibration time revealed no significant difference between 20 min and 2h, but the highest motility at 10 min after thawing was found with a 20-min equilibration. Dilution ratios of sperm-to-extender at 1:20, 1:60, and 1:120 showed no significant differences in motility and survival duration after thawing, but the dilution of sperm solutions with HBSS (320 mOsmol/kg) immediately after thawing reduced the decline of sperm motility, and significantly prolonged the survival duration. Based on these findings, the highest average sperm motility (77%) at 10 min after thawing was obtained when sperm were suspended in HBSS at 300 mOsmol/kg with 14% glycerol as cryoprotectant, diluted at a ratio of sperm to HBSS-glycerol of 1:20, equilibrated for 10 min, cooled at 20 degrees C/min from 5 to -80 degrees C before being plunged in liquid nitrogen, and thawed in a 40 degrees C water bath for 7s. If diluted immediately after thawing, sperm frozen by the protocol above retained continuous motility after thawing for more than 8 days when stored at 4 degrees C. 相似文献
2.
Swordtails and platyfish of the genus Xiphophorus are valuable models for biomedical research and are also commercially raised as ornamental fish valued by aquarists. While research use and commercial interest increases yearly in these fish, cryopreservation of sperm is unexplored in this genus. Xiphophorus are live-bearing fishes characterized by small body sizes, limited sperm volumes, and internal fertilization, an atypical reproductive mode for fish. These attributes make research involving cryopreservation of Xiphophorus germplasm challenging. To explore methods for sperm cryopreservation, this study evaluated the effect of different loading volumes of sperm suspension in 0.25-ml French straws, different dilution ratios of sperm to extender, an osmolality range of extender without cryoprotectant and with dimethyl sulfoxide (DMSO) as cryoprotectant, and short-term storage at room temperature and 4 degrees C after thawing. No significant difference in sperm motility due to straw loading volume was observed after thawing. Sperm motility was observed to decrease with increasing dilution. The osmolality of Hanks' balanced salt solution (HBSS) without cryoprotectant in which the highest sperm motility (67%) was observed was 320 +/- 3 mOsm/kg, which was also the osmolality of X. helleri blood plasma. When cryopreserved with 10% DMSO, however, the highest motilities within 10 min after thawing were observed with HBSS in the range of 240-300 mOsm/kg. Sperm suspended in HBSS at 320 mOsm/kg with a dilution factor of 100 maintained motility for 24h at room temperature, but persisted for 10 days when stored at 4 degrees C. These results provided the first evidence that cryopreservation may be applied to conservation of genetic resources in live-bearing fishes. 相似文献
3.
Aggression occurs when individuals compete over limiting resources. While theoretical studies have long placed a strong emphasis on context-specificity of aggression, there is increasing recognition that consistent behavioural differences exist among individuals, and that aggressiveness may be an important component of individual personality. Though empirical studies tend to focus on one aspect or the other, we suggest there is merit in modelling both within- and among-individual variation in agonistic behaviour simultaneously. Here, we demonstrate how this can be achieved using multivariate linear mixed effect models. Using data from repeated mirror trials and dyadic interactions of male green swordtails, Xiphophorus helleri, we show repeatable components of (co)variation in a suite of agonistic behaviour that is broadly consistent with a major axis of variation in aggressiveness. We also show that observed focal behaviour is dependent on opponent effects, which can themselves be repeatable but were more generally found to be context specific. In particular, our models show that within-individual variation in agonistic behaviour is explained, at least in part, by the relative size of a live opponent as predicted by contest theory. Finally, we suggest several additional applications of the multivariate models demonstrated here. These include testing the recently queried functional equivalence of alternative experimental approaches, (e.g., mirror trials, dyadic interaction tests) for assaying individual aggressiveness. 相似文献
4.
In experiments, there are usually two general ways of obtaining dominants and subordinates to test for the effect of recent experience upon ulterior behavior and dominance. One is to ‘impose’ such an experience on the contestants by a priori deciding which individual of the pair will become the dominant and which will become the subordinate through the use of rigged contests. The second technique is to let contestants ‘self-select’ the winner and loser by waiting for the spontaneous outcome of dyadic encounters between two usually well matched opponents. These two techniques of obtaining dominants and subordinates probably represent extreme cases on a single continuum of investment made by animals to settle dominance. To test this, we compared dominants and subordinates obtained from these two techniques in Xiphophorus fish males. It was found that pairs obtained through rigged contest (R) were much more aggressive in subsequent encounters than pairs in which the dominant and subordinate could self-select (S). They recuperated more rapidly from handling, initiated contact earlier, took more time to assess each other, and fought for a longer period of time. Prior-winners and prior-losers of the R condition more frequently relied on aggressive behavior during contest than that of the S condition. As a consequence, prior-winners and prior-losers of the R condition won equally the subsequent contest. On the contrary, prior-winners of the S condition defeated their prior-loser opponent in a majority of cases. These results can be tentatively explained by the following principle, winning or losing against a well matched opponent would leave more ‘experience’ than winning over a much weaker opponent, or losing to a much stronger one. This reinforces the hypothesis that prior-experiences are not qualitative states but come in various degrees. 相似文献
5.
J. A. C. Jonas-Davies V. Winfrey G. E. Olson 《Molecular reproduction and development》1983,7(4):309-324
The plasma membrane of spermatogenic cells of the teleost Xiphophorus helleri was examined ultrastructurally and cytochemically in order to characterize the temporal development of the membrane specializations characteristic of the mature spermatozoon. Mature sperm display a mosaic distribution of Concanavalin A and Ricinus comrnunis I binding sites; the anterior region of the head displays an intense binding that is not seen in other surface regions. This asymmetric binding is evident in early spermatids and the area of lectin binding appears associated with the plasma membrane overlying the nucleus. Transmission electron microscopy reveals that the plasma membrane over the anterior region of the head is characterized by an ordered glycocalyx and a tight adherence to the underlying nucleus. Additional membrane differentiations were revealed both in the midpiece region where a “submitochondrial net” is attached to the plasma membrane and at the base of the axoneme where the plasma membrane possesses a “collar-like” arrangement of circumferential rings. The possible functions of these differentiations, as well as their correlation to differentiations seen in sperm of other animal groups, are discussed. 相似文献
6.
7.
Competition for mating opportunities may involve exclusion of intrasexual competitors (direct) or defending resources necessary
to attract mates (indirect). Male swordtails (Xiphophorus helleri) engage in direct competition. Moreover in natural populations they defend a home range. This study aimed to test whether
this home range defence is a form of food resource defence, which may therefore have a female attraction function. Male swordtails
did defend a food resource and showed increased aggression in the presence of both food and females. However, food resource
defence decreased when females were present, suggesting that both food and females are treated as defendable resources. 相似文献
8.
Swordtail males formed dominance hierarchies at shallow sites in creeks or streams and invested much time in maintaining a high rank-order position (mean 11·1 chases per 5 min). 相似文献
9.
The attack readiness of socially isolated male swordtails () was measured in two different aggression tests: (a) In the standard–opponent test the aggressive responses to a small, rather passive opponent swimming in a small adjacent compartment of the test aquarium were counted. (b) In the mirror test the subjects were confronted with their own mirror image. Social isolation for 4 weeks resulted in a decrease of attack readiness in both test situations. It is concluded that -- similar to cichlids -- external stimuli from conspecifics are essential for maintaining the level of aggression readiness characteristic for socially living males. There are good reasons to propose that the effect of external stimuli is mediated by the pituitary-gonadal axis. On the other hand, it is well known from previous studies that, in escalated encounters between freely swimming males, isolated males fight longer and at higher intensities for rank-order position than non-isolated males. The hypothesis is proposed that the high fighting intensity of previously isolated males could be due to an experience levelling effect of social isolation, i.e. the influence of different agonistic experience is reduced by isolation.A critical review of the literature on isolation-induced decremental and incremental effects on aggression in teleosts is presented. Often it is extremely difficult to compare the results of different authors because the methods of behavioural measurement differ to a large extent. However, it is a striking fact that social isolation of immature fish in all known cases has resulted in an increase of aggressiveness. Probably in mature males, depending on species and circumstances, either an incremental or a decremental effect of social isolation may be adaptive. On the one hand, a spontaneous increase of attack readiness may be advantageous for defence of a territory or a position in the social hierarchy and improves the ability of a single individual to join a group of strange conspecifics. On the other hand, it may be economic to lower the level of androgenic hormones to some extent in the absence of conspecifics, and this could lead to a reduction of the aggression level. 相似文献
10.
In this study, refrigerated storage and cryopreservation of sperm from the green swordtail Xiphophorus helleri were investigated. Previous cryopreservation research in this species utilized motile sperm because unlike in most fish species, Xiphophorus sperm can remain continuously motile after collection for a week with refrigerated storage. However, this species reproduces by internal fertilization, and given the significant requirements for motility within the female reproductive tract and potential limitations on sperm energetic capacities, immobilization of sperm prior to insemination could be used to improve fertilization success. Thus, the goal in this study was to use osmotic pressure to inhibit the motility of sperm after collection from X. helleri, and to test the effect of immobilization on refrigerated storage and cryopreservation. The objectives were to: (1) estimate the motility of sperm at different osmotic pressures, and determine an osmotic pressure suitable for immobilization; (2) cryopreserve the immobilized sperm, and estimate the motility after thawing with or without dilution, and (3) compare motility of non-immobilized and immobilized sperm after thawing, centrifugation, and washing to remove cryoprotectant. Motility was determined when sperm were suspended in 11 different osmotic pressures (24-500 mOsmol/kg) of Hanks' balanced salt solution (HBSS). Motility was observed between 116 and 425 mOsmol/kg. Sperm were not motile when the osmolality was lower than 116 or higher than 425 mOsmol/kg. Motility of the immobilized (non-motile) sperm could be activated by changing the osmotic pressure to 291-316 mOsmol/kg, and motility of immobilized sperm from hypertonic HBSS (425 mOsmol/kg) was significantly higher than that from hypotonic HBSS (145 mOsmol/kg) after 48 h of storage. At an osmolality of 500 mOsmol/kg, HBSS was used as extender to maintain immobilized sperm during cryopreservation with glycerol as the cryoprotectant. High motility (approximately 55%) was obtained in sperm after thawing when cryopreserved with 10-15% glycerol, and dilution of thawed sperm in fresh HBSS (1:4; V:V) was found to decrease the motility significantly. No difference was found in the motility of thawed sperm cryopreserved with 14% glycerol and extended in 310 and 500 mOsmol/kg HBSS. Washing by centrifugation prolonged the motility of thawed sperm from 24 to 72 h in HBSS at 310 and 500 mOsmol/kg. This study showed that sperm from X. helleri could be immobilized by use of specific osmotic pressures, and that the immobilization did not affect sperm motility after thawing. The immobilization of sperm by osmotic pressure could minimize reduction of the energetic capacities necessary for insemination, traversal, and residence within the female reproductive tract, and fertilization. 相似文献
11.
Sperm cryopreservation of live-bearing fishes, such as those of the genus Xiphophorus is only beginning to be studied, although these fishes are valuable models for biomedical research and are commercially raised as ornamental fish for use in aquariums. To explore optimization of techniques for sperm cryopreservation of these fishes, this study measured the volumetric shrinkage response during freezing of sperm cells of Xiphophorus helleri by use of a shape-independent differential scanning calorimeter (DSC) technique. Volumetric shrinkage during freezing of X. helleri sperm cell suspensions was obtained in the presence of extracellular ice at a cooling rate of 20 degrees C/min in three different media: (1) Hanks' balanced salt solution (HBSS) without cryoprotective agents (CPAs); (2) HBSS with 14% (v/v) glycerol; and (3) HBSS with 10% (v/v) dimethyl sulfoxide (DMSO). The sperm cell was modeled as a cylinder of 33.3 microm in length and 0.59 microm in diameter with an osmotically inactive cell volume (V(b)) of 0.6V(o), where V(o) is the isotonic or initial cell volume. By fitting a model of water transport to the experimentally determined volumetric shrinkage data, the best-fit membrane permeability parameters (reference membrane permeability to water, L(pg) or L(pg)[cpa] and the activation energy, E(Lp) or E(Lp)[cpa]) of the Xiphophorus helleri sperm cell membrane were determined. The best-fit membrane permeability parameters at 20 degrees C/min in the absence of CPAs were: L(pg)=0.776 x 10(-15)m3/Ns (0.0046 microm/min atm), and E(Lp)=50.1 kJ/mol (11.97 kcal/mol) (R2=0.997). The corresponding parameters in the presence of 14% glycerol were L(pg)[cpa]=1.063 x 10(-15)m3/Ns (0.0063 microm/min atm), and E(Lp)[cpa]=83.81 kJ/mol (20.04 kcal/mol) (R2=0.997). The parameters in the presence of 10% DMSO were L(pg)[cpa]=1.4 x 10(-15)m3/Ns (0.0083 microm/min atm), and E(Lp)[cpa]=90.96 kJ/mol (21.75 kcal/mol) (R2=0.996). Parameters obtained in this study suggested that the optimal rate of cooling for X. helleri sperm cells in the presence of CPAs ranged from 20 to 35 degrees C/min and were in close agreement with recently published, empirically determined optimal cooling rates. 相似文献
12.
The acrosome reaction is a fundamental requirement for mammalian fertilization. Its exact molecular mechanisms and cellular elements are still poorly understood. We have detected an acrosomal sperm antigen, SAA-1, by monoclonal antibodies directed against SAA-1, that appears to be critically involved in the regulation of the acrosome reaction. SAA-1 is conserved within a broad range of mammalian species, emphasizing its important role in mammalian reproduction. Here we demonstrate that SAA-1 is immunohistochemically detectable in a nonmammalian vertebrate whose sperm do not possess an acrosome. In the swordtail, a live-bearing teleost with special reproductive tactics, we were able to demonstrate immunoreactivity of sperm heads of spermatids and mature sperm in the testis using monoclonal antibodies against SAA-1. Due to the cystic spermatogenesis with synchronous sperm maturation, immunoreactive maturational stages could be clearly identified. Stored immunoreactive sperm were also identified in spermathecal tissue of the female genital tract. Interestingly, immunoreactivity was furthermore detected in defined cells of the compounded endocrine organs pituitary and endocrine pancreas. All these different cell systems are involved in paracrine regulation and exhibit exocytotic properties. The possible nature of SAA-1 is discussed. Additionally, some new aspects of the morphologic composition of the swordtail pituitary are described. 相似文献
13.
For many species in nature, a sire's progeny may be distributed among a few or many dams. This poses logistical challenges--typically much greater across males than across females--for assessing means and variances in mating success (number of mates) and reproductive success (number of progeny). Here we overcome these difficulties by exhaustively analyzing a population of green swordtail fish (Xiphophorus helleri) for genetic paternity (and maternity) using a suite of highly polymorphic microsatellite loci. Genetic analyses of 1476 progeny from 69 pregnant females and 158 candidate sires revealed pronounced skews in male reproductive success both within and among broods. These skews were statistically significant, greater than in females, and correlated in males but not in females with mating success. We also compare the standardized variances in swordtail reproductive success to the few such available estimates for other taxa, notably several mammal species with varied mating systems and degrees of sexual dimorphism. The comparison showed that the opportunity for selection on male X. helleri is among the highest yet reported in fishes, and it is intermediate compared to estimates available for mammals. This study is one of a few exhaustive genetic assessments of joint-sex parentage in a natural fish population, and results are relevant to the operation of sexual selection in this sexually dimorphic, high-fecundity species. 相似文献
14.
Effect of growth compensation on subsequent physical fitness in green swordtails Xiphophorus helleri
Early environmental conditions have been suggested to influence subsequent locomotor performance in a range of species, but most measurements have been of initial (baseline) performance. By manipulating early growth trajectories in green swordtail fish, we show that males that underwent compensatory growth as juveniles had a similar baseline swimming endurance when mature adults to ad libitum fed controls. However, they had a reduced capacity to increase endurance with training, which is more likely to relate to Darwinian fitness. Compensatory growth may thus result in important locomotor costs later in life. 相似文献
15.
The swordlike exaggerated caudal fin extensions of male swordtails are conspicuous traits that are selected for through female choice. Swords are one of only few examples where the hypothesis of a pre-existing bias is believed to apply for the evolution of a male trait. Previous laboratory experiments demonstrated that females prefer males with longer swords and even females from some swordless species show an affiliation for males of sworded species. Earlier phylogenetic studies based on maternally inherited mitochondrial DNA placed the sworded southern swordtail Xiphophorus clemenciae with swordless platies, contradicting its morphology-based evolutionary affinities. The analyses of new nuclear DNA markers now recover its traditional phylogenetic placement with other southern swordtails, suggesting that this species was formed by an ancient hybridization event. We propose that sexual selection through female choice was the likely process of hybrid speciation, by mating of platy females with males of an ancestral swordtail lineage. In artificial crosses of descendent species from the two potential ancestral lineages of X. clemenciae the hybrid and backcross males have swords of intermediate lengths. Additionally, mate choice experiments demonstrate that hybrid females prefer sworded males. These experimental lines of evidence make hybridization through xeno-specific sexual selection by female choice the likely mechanism of speciation. 相似文献
16.
多氯联苯对剑尾鱼超氧化物岐化酶活性的影响 总被引:19,自引:2,他引:19
目的 研究多氯联苯 (PCBs)暴露对剑尾鱼 (Xiphophorushelleri)超氧化物歧化酶 (SOD)活性的影响 ,探讨剑尾鱼器官组织内SOD活性变化作为环境风险评价 (ERA)的有效生物学标记的可行性。方法 测定了PCBs对剑尾鱼 30d的半致死浓度 (LC50 ) ;使用浸浴法以 0、2、5 0 μg L三个PCBs浓度为剑尾鱼染毒 ,定量测定了 72h内肝、鳃及卵巢组织中的SOD的活性变化。结果 PCBs对剑尾鱼的 30dLC50 为 1 0 5 80 μg L ;PCBs对剑尾鱼肝脏和卵巢的SOD活性有明显 (P <0 0 1 )的影响。在最初染毒的 1 2h内 ,SOD活性略有上升 ,但随暴露时间延长 ,浓度增加 ,肝和卵巢的SOD活性均呈下降趋势。此外 ,结果还显示肝组织的SOD活性较高于卵巢的SOD活性 ,表明不同器官组织的SOD活性对PCBs胁迫的敏感性存在一定的差异。实验中鳃组织SOD活性在PCBs暴露后其变化不明显 (P >0 0 5 )。结论 表明剑尾鱼肝细胞SOD活性可作为环境风险评价 (ERA)的有效生物学标记 相似文献
17.
17β-雌二醇对剑尾鱼卵黄蛋白原的诱导研究 总被引:3,自引:0,他引:3
目的研究17β-雌二醇(E2)暴露对雄性剑尾鱼(Xiphophorus helleri)卵黄蛋白原(vitellogenin,Vtg)诱导作用作为环境风险评价(ERA)的有效生物学标记的可行性。方法以E2诱导的剑尾鱼雄性个体的整体匀浆液为材料,采用Sephacryl S-300凝胶过滤层析柱和QSepharose阴离子交换柱从剑尾鱼体内提纯Vtg。结果确定了被纯化的剑尾鱼Vtg在4%~7.5%Native PAGE电泳中相对分子质量为540×103。4%~7.5%Native PAGE电泳后的凝胶分别利用苏丹黑B进行脂蛋白染色、高碘酸-Schiff试剂进行糖蛋白染色和甲基绿进行磷蛋白染色,表明剑尾鱼Vtg是一种富含糖、脂、磷的蛋白。结论表明雄性剑尾鱼卵黄蛋白原的诱导变化可作为环境风险评价(ERA)的有效生物学标记。 相似文献
18.
C Azevedo 《Journal of cell science》1976,22(2):325-334
Intranuclear inclusions were observed in oocytes of Xiphophorus helleri during prophase I. In osmium-fixed leptotene nuclei, the inclusions were made up of groups of membrane-limited vesicles or tubules with pale contents, situated near the inner nuclear membrane with which some of them exhibited apparent continuities. In zygotene nuclei, larger vesicles also appeared bounded by two or three membranes and containing tubules apparently invaginated from their walls. In pachytene-dictyate nuclei most vesicular bodies had a wall formed by stratified membranes, or were entirely made up of membranous whorls. In glutaraldehyde-osmium fixed material some of these myeline-like bodies showed a peculiar arrangement, consisting of concentric bands each containing thick inner dense lamellae 2-0-3-0 nm thick and a 5-0 nm outer lamella. It is suggested that these inclusion bodies arise from the inner nuclear membrane of oocytes when cells start to grow intensely during prophase I. The bodies seem to become more complex at late prophase, probably by association of individual vesicles and the occurrence of multiple membrane invaginations, which may be related to active metabolic phenomena taking place at this stage in oocytes. 相似文献
19.
Alexandra L. Basolo & Kevin J. Delaney 《Ethology : formerly Zeitschrift fur Tierpsychologie》2001,107(5):431-438
Preexisting receiver biases can affect the evolution of sexually selected traits once traits favored by such biases arise. Female guayacón olmeca, Priapella olmecae , and green swordtail, Xiphophorus helleri , possess a bias favoring sworded conspecific males, despite phylogenetic evidence that the sexually selected sword expressed by male swordtails arose in Xiphophorus after the divergence of the two genera. In this study, we investigated the state of the bias favoring a sword in male Priapella and Xiphophorus to determine whether males also possess a bias that could operate in an intersexual selection context. Male P. olmecae preferred conspecific females with swords to those without swords. Thus, males and females in this unsworded species appear to share a preexisting bias favoring individuals of the opposite sex with swords. Male X. helleri , however, did not express a bias favoring sworded females; instead, in this species in which the sword is restricted to males, males discriminated against conspecific females with swords. Previous work suggests that female mate choice and male–male competition likely contribute to the maintenance of the sword in X. helleri . The sword may also play a role in sex recognition in swordtails. The absence of a sword preference in male green swordtails could reflect the current function of the sword. 相似文献