Turbidity affects association behaviour in male Poecilia latipinna

Male association preferences in a bisexual‐unisexual species complex were studied in clear and turbid environments. In south and central Texas, where the gynogenetic sexual‐parasite Poecilia formosa lives syntopically with Poecilia latipinna as its sexual host species, association times of P. latipinna males with conspecific sexual and heterospecific asexual females in clear and turbid water were measured sequentially. Turbidity had an influence on male mate association behaviour. Males spent less time with any kind of female stimulus in turbid water. There was no preference for conspecific sexual females, either in turbid water or under clear conditions. Also, origin of males and acclimatization to turbid water had no effect. How turbidity as a source of visual noise might affect communication among individuals and how this environmental factor might contribute to the stability of this sexual‐asexual mating complex in nature are discussed.     

Hypoxia and interdemic variation in Poecilia latipinna

Variation in respiratory traits was quantified between two populations of the sailfin molly Poecilia latipinna (one from a periodically hypoxic salt marsh, Cedar Key, and one from a chronically normoxic river site, Santa Fe River). Two suites of characters were selected: traits that may show both short‐term acclimation response and interdemic variation in acclimation response (metabolic rate, critical oxygen tension and respiratory behaviour), and those that are not likely to respond to short‐term acclimation but may vary among populations (gill morphometric characters). Sailfin mollies from the salt marsh, acclimated to hypoxia (1 mg l⁻¹, c . 20 mmHg) for 6 weeks, spent less time conducting aquatic surface respiration and had lower gill ventilation rates than hypoxia‐acclimated conspecifics from the well‐oxygenated river site. Poecilia latipinna acclimated to hypoxia exhibited a lower critical oxygen tension ( P _c) than fish acclimated to normoxia; however, there was also a significant population effect. Poecilia latipinna from Cedar Key exhibited a lower P _c than fish from the Santa Fe River, regardless of acclimation. Cedar Key fish had a 14% higher mean gill surface area relative to fish from the Santa Fe River, a character that could account, at least in part, for their greater tolerance to hypoxia.     

Sailfin molly females (Poecilia latipinna) copy the rejection of a male

When females choose among males they often accept one male asa potential partner and reject others as nonacceptable mates.The rejection of "wrong" males and the acceptance of "right"males are equally important processes in mate choice. Sailfinmolly females have been shown to copy the mate choice of otherfemales when accepting a male. The present study used videoplaybacks to test whether or not sailfin molly females copythe rejection of a male. Test females spent significantly lesstime with previously attractive males after having observedtheir rejection by other females. Eight of 15 females even reversedtheir choice and preferred the male they had previously foundunattractive. In control experiments, we showed that neitherinconsistency in female mate choice nor escape behavior of afemale in a nonsexual context could explain these results. Thisis the first study that shows that sailfin molly females copythe rejection of a male.     

Physiological responses to hyper-saline waters in sailfin mollies (Poecilia latipinna)

We examined the ionoregulatory physiology and biochemistry of the teleost sailfin molly (Poecilia latipinna), an inhabitant of salt marshes along the gulf coast, during exposure to hyper-saline waters (salinity range 35-95 ppt). Mollies were able to tightly control plasma Na(+) and Cl(-) concentrations and tissue water levels up to 65 ppt, but at higher salinities plasma ion levels began to rise and muscle water content dropped. Still, even at the highest salinity (90 ppt) plasma Na(+) and Cl(-) levels were only 32% and 39%, respectively, above levels at 35 ppt. Drinking rates at 60 ppt climbed 35%, while gut Na(+)/K(+)-ATPase (NAK) activity rose 70% and branchial NAK activity jumped 200%. The relatively small rise in drinking rate, in the face of a more than doubling of the osmotic gradient, suggests that a reduction in branchial water permeability significantly limited water loss and associated salt load. At 80 ppt, a salinity where plasma ion levels just begin to rise, drinking rate rose more rapidly, but gut and gill NAK activity did not, suggesting that mollies employed other pathways (perhaps renal) of salt excretion. At higher salinities, plasma ion levels continued to rise and muscle water content fell slightly indicating the beginnings of internal osmotic disturbances. To evaluate the energetic costs of hyper-salinity on mollies we measured the rate of O(2) consumption and found it rose with salinity, in sharp contrast to virtually all species previously examined. Interestingly, despite higher metabolism, growth was unaffected by hyper-salinity.     

Ultrastructure of the adenohypophysis in the teleost Poecilia latipinna

Summary In the sailfin molly, Poecilia latipinna, seven morphological endocrine celltypes could be distinguished with the electron microscope. Each of these was identified with one of the seven cell-types distinguished with the light microscope, to most of which endocrine functions have previously been allocated. Corticotrophs and prolactin cells form the rostral pars distalis, and the proximal pars distalis consists of an outer layer of gonadotrophs and an inner zone containing growth hormone cells and thyrotrophs. The pars intermedia contains two cell-types, of uncertain function. Stellate cells (interstitial cells) occur throughout the adenohypophysis, but are most numerous and prominent in the rostral pars distalis. The inner proximal pars distalis contains a cell-type not previously distinguished in this species with the light microscope, the Z-cell, which could be aminergic.The ultrastructural features of each cell-type are described in detail, and discussed in comparisons with the homologous cells described in other teleosts. There is good agreement for different teleosts in the ultrastructural details of each cell type.We thank Mr. L. Ethridge, Mr. M. P. Hancock, Mr. D. Hollingworth and Mr. W. Thomson for technical assistance, and Mr. D. Taylor of the Nuffield Institute of the Zoological Society of London for permission to use the Nuffield Institute electron microscope. We are grateful to Dr. Harry Grier, who collected and embedded glands from P. latipinna in its natural fresh-water habitat in Florida, U.S.A. T. Batten is in receipt of an S.R.C. Research Studentship.     

Circadian changes in prolactin cell activity in the pituitary of the teleost Poecilia latipinna in freshwater

Summary Quantitative morphometric studies with the electron microscope were made on the prolactin cells of wild freshwater sailfin mollies taken in Florida in August at four different times of day. The results indicate a circadian rhythm in the prolactin cell, the period of highest synthetic activity being from midday to evening, as indicated by the condition of nucleus, Golgi apparatus and rough endoplasmic reticulum, and by the incidence of granule release profiles. No circadian changes were detected in the ACTH cells.Several distinct sites of prolactin granule release were recognised. However, there was no conclusive evidence of granule release by any mechanism other than classical exocytosis.We thank Mr. W. Thomson for technical assistance and Ann Grier for help in collecting the fish. T.F.C. Batten is in receipt of an S.R.C. Research Studentship.     

Environmental effects on adult growth patterns in the male sailfin molly,Poecilia latipinna (Poeciliidae)

Synopsis Widespread male body size variation in P. latipinna appears to be attributable to genetic variation in the size at maturation. The contribution of adult growth needs to be assessed because adult growth rates may vary with size at maturation and local environment. In our laboratory study we examined adult growth patterns as a function of size at maturation and juvenile experience (favorable or unfavorable conditions). In our field study we assessed adult growth as a function of initial size and environmental condition (using males in enclosures in contrasting habitats). Adult growth rates in the laboratory were an order of magnitude higher than rates observed in field enclosures. Growth rates varied with male size, increasing with increasing male size in the laboratory study but decreasing with increasing male size in the field study. The laboratory results alone would have cast considerable doubt on the ability to interpret size distributions of field-collected males, but the field results indicate that adult growth is sufficiently low that it can be ignored as a source of body size variation within and among populations.     

Male body length influences mate-choice copying in the sailfin molly Poecilia latipinna

Females can choose a male independently of other females' matepreferences, or they can copy the mate choice of other females.Alternatively, mate-choice copying and independent mate choicecan interact if females assess male traits when deciding whetheror not to copy. We investigated how mate-choice copying interactswith a preference for large males in the sailfin molly (Potecilialatipinna). Sailfin molly females exhibited a preference forlarger males. They also copied the mate choice of other femaleswhen males were of similar body length. Females did not copy,however, when males differed substantially in body length. Ourresults show that conspecific mate copying occurs in the sailfinmolly but does not override a preference for larger males.     

补充蒺藜提取物对男子拳击运动员肩、肘关节爆发力和耐力的影响

目的:研究补充蒺藜提取物对力量训练和耐力训练的男子拳击运动员肩、肘关节的爆发力和耐力的影响。方法:15名青少年男子拳击运动员随机分为训练对照组(n=7)和训练+蒺藜组(n=8,完成所有测试项目的n=6)。两组运动员同时进行3周大强度力量训练,休息4周,再进行3周中强度耐力训练,每周训练6d。训练+蒺藜组运动员每日上午训练前服用1250mg的蒺藜提取物胶囊,而对照组服用安慰剂。训练前、力量训练和耐力训练后,用瑞士CONTREX等速肌力测试仪检测两组运动员肩关节的屈伸肌、收展肌和肘关节的屈伸肌在90°/s和120°/s角速度运动时的相对峰力矩(峰力矩/体重)、相对平均功率(平均功率/体重)、相对总功(总功/体重)、做功疲劳度和屈伸肌(和收展肌)峰力矩比。结果:与训练前比较,力量训练和耐力训练可降低男拳击运动员肩和肘关节屈伸肌的相对总功(90°/s和120°/s),增加肩关节屈肌做功疲劳度(120°/s)(P均<0.05);与对照组比较,补充蒺藜提取物可改善男拳击运动员力量训练所致肩关节屈伸肌相对总功的减少及屈肌做功疲劳度的增加,以及耐力训练所致肘关节屈伸肌相对总功的降低(P均<0.05);其余各检测指标无显著差异。结论:补充蒺藜提取物可改善力量训练所致肩关节、耐力训练所致肘关节的屈伸肌爆发力和耐力的降低;但不影响肩关节收展肌的爆发力和耐力,也不影响肩和肘关节的稳定性。     

Size and morphological variation in males of the sailfin molly,Poecilia latipinna

Synopsis Mature males of the sailfin molly, Poecilia latipinna (Poeciliidae), display extensive variation in size and morphology. Small males, less than about 30 mm SL, usually exhibit no distinctive color or morphological development. Large males, greater than about 45 mm SL, display full expression of the sailfin traits, including bright blue and gold life colors, distinctive pigment markings on the fins and body, and a greatly enlarged dorsal fin. Intermediate-sized males, 30–45 mm SL, display intermediate and variable development of secondary sexual characteristics. For convenience, small, intermediate, and large males are respectively referred to as Types 1, II, and III. A multi-year analysis of four study populations in east-central Florida revealed that males did not occur in discrete classes but, instead, occurred in a size and morphological continuum. Coloration and morphological development were highly correlated with size, and the mensural traits examined displayed strong allometry. Size distributions of mature males were relatively stable at any study site over time, but there were large differences between sites. At one extreme, males at the VABI site were always relatively small (16–40 mm SL) and Type III males were absent. At the other extreme, the population at the BDGST site contained a full array of male sizes (18–60 mm SL) and Type III males were present in small numbers throughout the summer months. Regression analysis revealed only minor differences between these extreme populations in the relationship between morphological development and body size. It appears that environmental, genetic, and social factors interact in a complex and poorly understood way to control variation in male size and morphology.     

Distribution of steroidal saponins in Tribulus terrestris from different geographical regions

The steroidal saponins of Tribulus terrestris L. (Zygophyllaceae) are considered to be the factor responsible for biological activity of products derived from this plant. The activity depends on the concentration and the composition of active saponins, which in turn is influenced by the geographical origin of plant material. Samples of T. terrestris collected in Bulgaria, Greece, Serbia, Macedonia, Turkey, Georgia, Iran, Vietnam and India were analyzed by LC-ESI/MS/MS for the presence and the concentration of protodioscin (1), prototribestin (2), pseudoprotodioscin (3), dioscin (4), tribestin (5) and tribulosin (6). The flavonoid rutin (7) was also included in the comparison. The results revealed distinct differences in the content of these compounds depending on region of sample collection, plant part studied and stage of plant development. The samples from Bulgaria, Turkey, Greece, Serbia, Macedonia, Georgia and Iran exhibited similar chemical profile and only some quantitative difference in the content of 1-7 with protodioscin (1) and prototribestin (2) as main components. The Vietnamese and Indian samples exhibit totally different chemical profile. They lack 2 and 5, while tribulosin (6) is present in high amounts. Compounds different from 1 to 7 are dominating in these 3 samples. The presented results suggested the existence of one chemotype common to the East South European and West Asian regions. Most probably, the Vietnamese and Indian samples belong to other chemotypes which are still to be studied and characterized. No clear correlation between the burrs morphology and the chemical composition of the samples has been found.     

Female sperm limitation in natural populations of a sexual/asexual mating complex (Poecilia latipinna, Poecilia formosa)

In sperm-dependent sexual/asexual mating systems, male mate choice is critical for understanding the mechanisms behind apparent stability observed in natural populations. The gynogenetic Amazon molly (Poecilia formosa) requires sperm from sexual males (e.g. Poecilia latipinna) to trigger embryogenesis, but inheritance is strictly maternal. Consequently, males should try to avoid or reduce the cost of mating with asexuals. We investigated male mate choice by documenting the presence of sperm in natural populations and found that a higher proportion of sexual females had sperm than asexuals. In addition, among those females that had sperm, sexuals had more sperm than asexuals. Our results hint at a role for male mate choice as a stabilizing factor in such systems.     

Feeding rates in the sailfin molly Poecilia latipinna and its coexisting sexual parasite,the gynogenetic Amazon molly Poecilia formosa

Feeding rates of the gynogenetic Amazon molly Poecilia formosa and one of its sexual hosts, the sailfin molly Poecilia latipinna, were measured under winter and summer temperature conditions. Food consumption of the unisexual P. formosa in winter conditions was significantly higher than that of P. latipinna, and it is hypothesized that the resulting food stress might have an important influence on the population composition of these closely related fishes via higher winter mortality in P. formosa.     

Pigments and ultrastructures of pigment cells in xanthic sailfin mollies (Poecilia latipinna).

Electron micrographs of skin from xanthic (gold) sailfin mollies revealed numerous xanthophores, as well as scattered melanophores. The melanophores were seen to contain premelanosomes in various stages of development. This is consistent with the fact that xanthic mollies have been shown to be tyrosinase positive. Melanosomes in xanthic mollies appear to develop by one of two pathways: 1) from an endoplasmic reticulum-derived vesicle which develops an internal lamellar framework, and 2) by fusion of multiple Golgi-derived vesicles which lack an internal lamellar framework. Analysis of the pigments in the skin of the xanthic mollies identified four colorless pteridine pigments (xanthopterin, isoxanthopterin, neopterin, and pterin) and a carotenoid with an absorbance spectrum similar to beta-carotene. It appears that, unlike some other poeciliid fishes, sailfin mollies do not use pteridine pigments for orange coloration. Rather, they appear to rely primarily on carotenoids.     

Individual Variation in Male Size and Behavioral Repertoire in the Sailfin Molly Poecilia latipinna

Variation among individuals in the expression of behaviors and associations of behaviors in different contexts can lead to the maintenance of behavioral polymorphisms. Individual variation in morphology is often associated with behavioral polymorphism, yet the degree to which morphology predicts behavioral phenotype is not well understood. We measured individual variation in size and behaviors in the sailfin molly, Poecilia latipinna, by comparing the behavior of individual males of different sizes across four different contexts (mating, exploratory tendency, sociability, and predator inspection). We also investigated the degree to which male size, a fixed genetic trait, influenced the expression of each behavior and associations between behaviors. We found that male mollies show strong associations between certain behaviors and only some of these are predicted by male size. For example, size has a strong influence on the courtship‐boldness axis with larger males showing higher rates of courtship displays and being bolder in predator inspection. A positive association was found between exploratory tendency, sociability, and gonopodial thrusting rates, yet the expression of these behaviors was independent of male size. Thus, sailfin mollies, like many fish species, show associations of behaviors that contribute to differences among males in personality type. The fixed genetic effect of male size at maturity influences courtship and boldness, but individual variation in exploratory tendency, sociability, and sneak copulation attempts through gonopodial thrusts is independent of male size. Such variation among males in behavioral associations within and between different contexts may slow the rate at which populations of P. latipinna can diverge in individual behaviors.     

Female Preferences for Sailfin and Body Size in the Sailfin Molly, Poecilia latipinna

We tested the mating preference of female sailfin mollies (Poecilia latipinna) by presenting them with pairs of dummy males differing in: (I) sailfin and body size together (holding sailfin : body size ratio constant); (II) body size alone (holding sailfin size constant); (III) sailfin size alone (holding body size constant); and (IV) sailfin : body size ratio (holding total lateral projection area constant). Females spent more time near dummies of greater sailfin or greater body size. The preference functions based on the first three sets of stimuli showed a similar pattern: the preference between any two simultaneously presented dummies increased with the magnitude of the discrepancy in lateral projection area (LPA) between them. However, when LPA was held constant in expt (IV), neither body size, sailfin size, nor any particular dummy (i.e. any particular sailfin + body size combination) was preferred. These findings suggest that increased LPA is more stimulating to sexually receptive females and that females consequently prefer larger males. The sailfin may therefore have evolved as a way for males to exploit this sensory bias and appear larger to prospective mates.     

Innate and Learned Shoaling Preferences Based on Body Coloration in Juvenile Mollies,Poecilia latipinna

Shoaling offers fish enhanced protection from predators through a phenomenon known as the confusion effect. This phenomenon depends on a high degree of phenotypic homogeneity within a shoal, which may confuse predators that have difficulty in targeting a single individual as prey. Accordingly, fish typically choose shoalmates with similar phenotypic characteristics to themselves. In the molly (Poecilia latipinna), dramatic differences in body coloration have been shown to affect shoalmate choice in adults. Here, we show that juvenile mollies (50 d old) were capable of shoaling and that early experience impacted shoalmate choice. When raised in isolation, mollies chose shoalmates with similar body coloration to their own. When raised with other juvenile mollies, test fish chose to associate with individuals of the same coloration as the fish with whom they had been reared. These results show that P. latipinna are capable of the behavioral plasticity that has been demonstrated in other fish species, and that early experience affects the impact of body coloration on shoaling decisions in this species.     

Multilocus DNA fingerprinting detects population differentiation in the outbred and abundant fish species Poecilia latipinna

Several workers have suggested that multilocus multilocus variable number of tandem repeat (VNTR) based 'DNA fingerprints' are not useful in detecting differentiation among outbred populations. They suggest that the extremely high mutation rates and complexity associated with multilocus VNTR fragments make detection of interpopulation differences against a background of extremely high intrapopulation variation unlikely. This paper shows that DNA fingerprinting with the multilocus VNTR probes (GACA)₄ and (CT)₉ reveal significant population differences in VNTR frequencies between Florida and Georgia populations of the outbred, abundant and vagile fish species Poecilia latipinna. Differences in mutation rates among some VNTR loci may account for the ability to detect interpopulation differentiation with these probes. These results suggest that appropriate species/probe combinations would allow investigations of population structure on a microgeographical scale even in outbred species with multilocus VNTR probes where less-sensitive techniques have failed.