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1.
A gonadotropic hormone-releasing hormone analogue ([D-Ala6, Pro9-NHEt]LHRH, GnRH-A) was administered to the winter flounder, Pleuronectes americanus (Walbaum) at different stages of the reproductive cycle from September 1988 to July 1989. Both males and females responded to releasing hormone treatment throughout the year except for a brief summer period in post-spawned fish when the gonads were regressed. In females, GnRH-A markedly increased plasma estradiol-17 and testosterone levels and accelerated growth of the ovaries during the period of early gonadal recrudescence beginning in August. In prespawning females, GnRH-A treatment increased plasma testosterone levels in association with a stimulation of germinal vesicle migration and ultimately ovulation. During the fall, GnRH-A treatment of males increased plasma androgen levels (testosterone and 11-ketotestosterone) and stimulated growth of the testes. In February, a time when spermiation is initiated in only half of the males, the proportion of spermiating males was increased by treatment with releasing hormone, indicating that spermiation can be advanced in some males by ca. 2 mo.A portion of this work was given as a poster presentation at the XIth International Symposium on Comparative Endocrinology, Malaga, Spain, May 14–20, 1989 相似文献
2.
Mediterranean amberjacks, Seriola dumerilii Risso, were caught off the Pelagie Islands, in the south Mediterranean Sea, between May 1997 and June 1999. Fish blood was sampled, and gonads were collected at 10-day intervals throughout the spawning period and at monthly intervals during the resting period. Concentrations of plasma estradiol-17ß (E2), testosterone (T), 17,20ß-dihydroxy-4-pregnen-3-one (DHP) and vitellogenin (Vtg) in females; and plasma T and 11-ketoT (11-KT) in males were correlated with changes in gonadal development. The first females that had already ovulated (F5) were found in late May. Most mature females (F4) were caught in June. Post-spawned females (F6) were found from late July until September. Estradiol-17ß was at baseline levels (<0.02 ng ml–1) during autumn/winter and rapidly peaked (6.29±0.68 ng ml–1) from May to early July. Plasma T levels showed a similar profile and were positively correlated to E2 (r2=0.668) during the spawning period. Continuously elevated levels of E2 and T were observed during the spawning season in vitellogenic females (stages F3, F4 and F5). Resting females were found during the autumn/winter months. Vitellogenin levels increased during May and peaked in June, reverting to undetectable levels in August, in parallel with sex steroid changes. Plasma DHP levels peaked in June (283.45±97.3 pg ml–1), falling to basal values (<5 pg ml–1) in August. DHP levels were higher in mature females (F4) than in maturing (F3) and in partially ovulated (F5) females. DHP values increased during germinal vesicle migration, peaked during germinal vesicle breakdown and decreased again during complete oocyte hydration. In males, changes in T and 11-KT plasma levels were related to testis development. The highest levels of T (5.76±2.64 ng ml–1) were measured during spermatogenesis and highest 11-KT (5.28±3.6 ng ml–1) in males with milt, from May to June. This study provides information, for the first time, on the relation between plasma sex steroid profiles and gonad development in wild Mediterranean amberjack, a useful benchmark for broodstock monitoring under controlled conditions.Communicated by R. Cattaneo-Vietti, Genova 相似文献
3.
Plasma sex steroid profiles and the seasonal reproductive cycle in male and female winter flounder,Pleuronectes americanus 总被引:1,自引:0,他引:1
The pattern of seasonal gonadal development and variations in plasma sex steroids were investigated in adult male and female winter flounder, Pleuronectes americanus (Walbaum), from Conception Bay Newfoundland beginning August 1987 to December 1988. The winter flounder reproductive cycle can be divided into five consecutive phases of relative reproductive activity including: (1) rapid gonadal recrudescence in the fall (August–December); (2) continued slow gondadal growth in females, or maintenance of the well developed gonads in males, during the winter (December–February); (3) a prespawning phase of gonadal maintenance in the spring (March–April); (4) spawning early in the summer (May–June) after the female gonads reach peak weight; and (5) the summer postspawned period (June–August) when the gonads remain regressed. Female gonadal recrudescence in August is characterized by small increases in plasma estrogen levels and recruitment of small oocytes (150 m) into yolk accumulation. For the winter months, estradiol-17 levels in the plasma remain stable, approximately 15 ng ml-1, until rising again together with testosterone to peak hormone levels just prior to spawning in conjunction with the highest seasonal values for the gonadosomatic index (GSI) and oocyte diameter. After spawning, the ovaries are regressed and sex steroids in the plasma fall to very low levels. Rapid seasonal recrudescence of the gonads in males is evident from rising GSI values, which reach a maximum in October, and from substantial early seasonal increases in plasma testosterone and 11-ketotestosterone. Afterwards, although GSI values subsequently decline presumably reflecting the process of spermiogenesis and/or onset of spermiation in some males, the testes remain relatively well developed with the presence of sperm throughout the spawning season. As the proportion of spermiating males increases, the plasma levels of the androgenic steroid hormones rise to peak circulating levels from April to June. At the end of the summer reproductive season, the testes of post-spawned males become regressed and plasma testosterone and 11-ketotestosterone levels fall, reaching the lowest seasonal values. 相似文献
4.
K. Håkan Olsén J. Torbjörn Järvi Ian Mayer Erik Petersson Frederieke Kroon 《Chemoecology》1998,8(1):9-17
Summary. In the present experiment the behaviour and endocrine status of males of the brown trout, Salmo trutta L., (Salmoniformes: Salmonidae) were studied when males were kept in a stream tank with a nest digging female. Groups of
mature adult males and precocious intact or anosmic male parr were placed with the nesting female so that the group resembled
a natural spawning situation with big anadromous fish acting as dominant males and precocious parr acting as “sneakers”. A
control experiment was also run with only males without a female present. In intact parr there were significant positive correlations
between the per cent of the total observation time spent with a female, milt volume, and plasma concentration of 17α, 20β-dihydroxy-4-pregnen-3-one.
Anosmic parr had significantly lower volumes of strippable milt and gonadal steroid hormone levels compared with intact parr.
However, no differences were found in the control experiment. Significantly fewer anosmic parr attended and courted the nesting
female and those anosmic fish that attended the female had significantly lower plasma levels of gonadal hormones. Intact parr
also displayed a greater number of agonistic acts against other parr without any difference in fighting ability. No differences
in aggression occured in the control experiment. In adult males together with a female, post-experimental gonadal steroid
hormone levels were higher than pre-experimental levels. Positive correlations between aggression and androgen hormone levels
were observed in adult males. No differences in plasma hormone levels were observed between adult males and intact precocious
males. The results show that olfactory occlusion results in low steroid hormone levels and milt volumes in precocious males
placed in a spawning situation. The courting behaviour was also affected by anosmia. Odours from the nesting female may have
caused the enhanced plasma hormone levels and stimulated the males to attend the female.
Received 15 May 1997; accepted 29 June 1997. 相似文献
5.
The relationship between sperm characteristics and reproductive success was examined in male herring, Clupea harengus L. Males were categorised as being first-time or repeat spawners on the basis of their age; they were also grouped according
to whether their sperm were immediately active and exhibited forward motion on contact with seawater (FM) or had little or
only vibratory motion (VM). Unlike the Pacific herring C. pallasii Valencienes, Atlantic herring sperm is usually motile on contact with seawater. The age, weight and gonadosomatic index (testes
mass as a percentage of somatic mass = GSI) were measured and used as characteristics for individual fish. Sperm traits measured
were (1) adenosine triphosphate (ATP) concentration, (2) sperm count, (3) duration of sperm motility. Reproductive success
for each male was estimated from the fertilisation rate and from the length of larvae at hatching. Fertilisation rates for
all fish were generally >80%. The ATP concentration of non-activated spermatozoa was negatively correlated with fertilisation
rate. Among repeat spawners, fish with higher GSIs produced larvae that were larger at hatching. Although VM sperm fertilised
eggs at rates equivalent to fertilisation by FM sperm, the larvae produced by VM sperm were significantly smaller at hatching.
Larval length tended to increase in parallel with the duration of sperm motility, but the relationship was not significant
in these tests. The results did not indicate any age or size pattern to spawning readiness in male herring. Sperm that are
not yet ready to be shed are not fully motile on contact with seawater, but are still capable of fertilising eggs that hatch
successfully. There is likely to be a progression of males which come into spawning readiness within a spawning shoal; therefore
it is possible that paternal influences would result in a progressive decrease in larval size over the spawning period in
winter-spawning Celtic Sea herring.
Received: 22 November 1997 / Accepted: 8 June 1998 相似文献
6.
Peculiar fertilization dynamics, with males releasing sperm in mucous trails lasting several hours, characterize some demersal
spawning fish. The mating system was investigated in a natural population of one of these species: the grass goby Zosterisessor ophiocephalus (Pallas, 1814), a large coastal goby inhabiting seagrass meadows in shallow brackish water. Adult males ranged in size from
7.4 to 23 cm total length, but only larger ones were observed to dig and defend a burrow, where they performed parental care
on eggs laid by one to several females. Field observations together with analyses of age, sperm production, trail sperm content
and sperm competition tests indicated the occurrence of alternative male mating tactics, likely the expression of an ontogenetic
gradient. Larger males are older than smaller ones, and while the former are territorial, the latter “sneak” territorial male
spawns. The ejaculate characteristics indicate that grass goby males have functionally polymorphic spawns: in fact sperm trails
of larger males last longer and release fewer sperm than those of smaller males. Sperm production over several days is more
constant in larger than in smaller males, but the total number of sperm released is higher in the latter. The influence of
seminal fluid in the functional intraspecific variability in sperm release in this species is discussed.
Received: 30 December 1999 / Accepted: 31 July 2000 相似文献
7.
Sperm characteristics associated with different male reproductive tactics in bluegills (Lepomis macrochirus) 总被引:3,自引:0,他引:3
We examined the availability and motility of sperm from parental and sneaker male bluegills (Lepomis macrochirus), a colonially nesting sunfish (Family Centrarchidae) with male parental care and a high incidence of cuckoldry by both sneaker
and satellite males. We found no differences between sneakers and parentals in length and swimming speed of sperm, or percent
and duration of sperm activity. In sneaker milt, however, sperm was almost 50% more concentrated than in parental milt (16.5×106 vs 11.5×106 sperm/μl of milt, respectively). Despite this difference in sperm concentration, stripped ejaculates from sneakers contained
almost 400 million fewer sperm (only 32% as many sperm) than those from parentals due to their much smaller stripped ejaculate
volumes (only about 19% that of parentals). Thus unless sneakers can compensate by releasing more sperm or gaining closer
proximity to eggs at the time of spawning, they may be at a disadvantage with respect to sperm competition. We discuss these
results in relation to models for the evolution of alternative reproductive behaviours in this species and suggest that the
cuckolders may be making the best of a bad situation.
Received: 18 February 2000 / Revised: 23 March 2000 / Accepted: 14 September 2000 相似文献
8.
Eva Giacomello Francis C. Neat Maria B. Rasotto 《Behavioral ecology and sociobiology》2008,62(5):671-680
Sperm competition, cost of spermatogenesis and spawning frequency are known to influence ejaculate expenditure. Accordingly,
males, particularly those with high reproductive costs, are expected to have evolved mechanisms enabling them to prudently
allocate sperm, such as the fractioning of ejaculate expenditure or the semi-cystic type of spermatogenesis, hypothesised
to favour the production of small ejaculates. In this study, we investigate sperm competition risk, ejaculate size and mode
of ejaculate release in seven polygynous blenniid fish where males provide sole paternal care of eggs. In addition, we estimated
the relative size of the two parts composing the male gonad, the strictly testicular (testicular lobules or testis) and the
glandular (testicular gland), as the development of the latter is indicative of the level of semi-cystic spermatogenesis.
In all the examined species, eggs were laid one by one, and the sperm expenditure at mating, evaluated as the total number
of sperm released per mating, was parcelled out in several successive ejaculations, allowing males to adjust the release of
sperm to the duration of egg deposition. In accordance with sperm competition theory, species experiencing higher sperm competition
risk allocated more in sperm, both considering ejaculate size and ejaculate expenditure per mating. An increase in sperm expenditure
was paralleled by the development of the testis at the expense of the testicular gland. Smaller species, whose males do not
face sperm competition risk and fecundity is low, produced smaller ejaculates and exhibited a more developed testicular gland,
supporting the hypothesis that a semi-cystic type of spermatogenesis is a mechanism allowing sperm economy. 相似文献
9.
The spawning patterns of two penaeid prawns, Metapenaeus endeavouri (Schmitt) and M. ensis (De Haan), were examined from data collected at 45 stations between March 1986 and March 1992. An index of population fecundity
based on the abundance, proportion and fecundity of sexually mature females was used as a measure of spawning output of the
prawn stock. The population fecundity index for M. ensis was higher than that for M. endeavouri. The monthly population fecundity index for M. endeavouri varied markedly among years, while that for M. ensis was consistent among years. Spawning of M. endeavouri occurred year-round, while that of M. ensis was concentrated mainly in spring (September to November). For M. endeavouri, a minor spawning, derived from a relatively small number of summer spawners, occurred in the 20 to 30 m offshore waters
in summer. In early summer (after May), the major spawning group consisted of large females from the winter-spawning cohort,
and the spawning area shifted to depths of 30 to 60 m. In winter (July), the major spawning, derived from the winter-spawning
cohort, occurred at depths of 20 to 40 m. For M. ensis, the major spawning, derived from the spring-spawning cohort, was observed in depths <50 m and was concentrated particularly
in inshore waters (<20 m) in spring. In autumn, the spawning output was mainly from the autumn-spawning cohort, which comprised
but a small number of individuals. In winter, the major spawning group again consisted of the large females from the spring-spawning
cohort, and spawning increased in the oceanic waters (>50 m). These results suggest that mature female M. endeavouri and M. ensis move offshore (>40 m) by May and July, respectively, and return to shallow waters (<35 m) in July and November, respectively.
The monthly reproduction patterns of both species in the “effective spawning” area showed that the major spawning season for
M. endeavouri is August to October and that for M. ensis is September to December.
Received: 19 February 1999 / Accepted: 18 June 2000 相似文献
10.
The aim of this study was to investigate reproductive strategies and their consequences in gray mouse lemurs (Microcebus murinus), small solitary nocturnal primates endemic to Madagascar. Previous reports of sexual dimorphism in favor of males and females,
respectively, a high potential for sperm competition and pheromonal suppression of mating activity among captive males, led
us to investigate mechanisms of intrasexual competition in a wild population. Based on 3 years of mark-recapture data, we
demonstrate that sexual dimorphism in this species fluctuated annually as a result of independent changes in male and female
body mass. Male body mass increased significantly prior to the short annual mating season. Because their testes increased
by 100% in the same period and because their canines are not larger than those of females, we suggest that large male size
may be advantageous in searching for estrous females and in enabling them to sustain periods of short-term torpor. In contrast
to reports from captive colonies, we found no evidence for two morphologically distinct classes of males. Finally, we also
show that most adult males are active throughout the cool dry season that precedes the mating season, whereas most adult females
hibernate for several months. This is in contrast to other solitary hibernating mammals, where males typically emerge 1–2
weeks before females. Thus, this first extended field study of M.␣murinus clarified previous conflicting reports on sexual dimorphism and male reproductive strategies in this primitive primate by
showing that their apparent deviation from predictions of sexual selection theory is brought about by specific environmental
conditions which result in sex-specific life history tactics not previously described for mammals. A general conclusion is
that sexual selection can operate more strongly on males without resulting in sexual dimorphism because of independent selection
on the same traits in females.
Received: 6 July 1997 / Accepted after revision: 28 March 1998 相似文献
11.
In Portuguese waters, thornback ray Raja clavata spawns mainly between May and January, although females and males in spawning condition are found throughout the year. The
maturation process can be divided into three main phases by using information on gonad weight, oviducal gland and uterus width
in females and on gonad weight, clasper length and sperm duct width in males. Females attain length-at-first-maturity at 784 mm
and males at 676 mm, at ages of 7.5 and 5.8 years, respectively. In females larger than length-at-first-maturity, a resting
stage was identified characterized by low gonadosomatic index and well-developed oviducal glands and uteri. These results
along with the low proportion of adult females that are effectively reproducing per month demonstrated that the thornback
ray cannot be considered a continuous spawner as described in other studies. Fecundity was determinate with about 35 eggs
released per batch. During the spawning season, a total of four batch episodes occur indicating that the total fecundity was
approximately 136 eggs per female. Regional differences may exist in the reproductive strategy of the species, namely on the
duration of the spawning season, length-at-first-maturity, and fecundity, which can be related to a more intense fishing pressure
in northern European waters. 相似文献
12.
The annual epidemic spawning period of a Scottish population of Arenicola marina (L.) has been recorded over a period of 13 yr. This population spawns between mid-October and mid-November in a discrete
spawning event over a period of 4 to 5 d. Endocrine manipulation experiments showed that spawning is induced in females only
if sufficient titres of PMH (prostomial maturation hormone) are present in the prostomia. These levels are attained during
the 2 to 3 wk prior to the natural spawning date. The East Sands, St. Andrews population always spawns during periods of spring
tides regardless of tidal amplitude or whether they are full- or new-moon tides. Meteorological data, including sea-temperature
data were collected for each year, and correlation of the environmental data with spawning time was attempted. Correlation
of spawning times with weather patterns showed that mean daily air pressures were significantly higher during the spawning
period than from September to November as a whole. Evidence also suggests that a reduction in sea temperature is required
prior to spawning. A significant moderate negative correlation was found between May to July air temperatures and spawning
date, suggesting that higher May to July temperatures may induce early spawning. Daily rainfall and wind speed were also lower
during the spawning period, but not significantly so. These results indicate that air pressure (or changes therein) may act
as a final spawning cue, and the advantages of this are discussed in relation to fertilization success. A model of the interplay
between environmental parameters and the endocrine mechanisms controlling the induction of spawning is proposed. Higher than
average summer temperatures may advance gametogenesis to bring the population into a state of maturity (full-size oocytes,
well-developed sperm morulae), and may also advance spawning time. Once the population has completed gametogenesis, a drop
in sea temperature is then required to trigger an increase in endocrine titres within the prostomium, without which spawning
cannot be induced by prostomial injection. The population spawns on spring tides; however a lack of clement weather coinciding
with the spring tide will result in population-wide spawning being aborted, as in 1996. Clement weather (high pressure, low
rainfall and wind speed) in conjunction with spring tides permits spawning to proceed to completion.
Received: 21 June 1999 / Accepted: 25 January 2000 相似文献
13.
Theo C. M. Bakker Michael Hollmann Marion Mehlis Marc Zbinden 《Behavioral ecology and sociobiology》2014,68(4):617-627
Some theoretical models of sperm competition make the assumption that in fish species with external fertilisation, sperm length relates positively to swimming speed at the expense of sperm longevity. Few studies have tested this assumption. We used the three-spined stickleback, Gasterosteus aculeatus L., to study functional sperm morphology. In this study, the relationship between males’ mean sperm length and fertilisation rate was investigated in vitro in a non-competitive situation. Fertilisation at different time points after sperm release was taken into account, and sperm morphology was quantified from scanning electron microscopy images. The time series of artificial fertilisations demonstrated that males which produced sperm with a longer tail fertilised faster, but their sperm had a shorter lifespan (or activity period). It was further suggested that males that produced sperm with a larger midpiece had greater fertilisation chances later on in the fertilisation process. Thus, in sticklebacks, there exists functional variation in sperm morphology, and sperm tail length is traded off against sperm longevity (or activity). 相似文献
14.
Sexual selection may operate through either direct selection on preference genes or indirect genetic benefits. However, in many species both direct and indirect selection may operate and can influence female mate and oviposition choice. Adaptations by males for sperm competition can also affect female mate and oviposition choice and can lead to sexual conflict. We investigated the role of direct and indirect benefits and male adaptation to sperm competition for female oviposition decisions in the bitterling, Rhodeus sericeus, a freshwater fish that spawns on the gills of living unionid mussels. Field experiments showed that females chose mussels for spawning on the basis of the number of embryos already in mussels and the body size and/or extent of red coloration of the eyes of territorial males. There was also a significant interaction between these direct and indirect benefits of oviposition choice. Territorial male bitterling avoided leading females to mussels into which rivals had already released sperm. Males also increased their rate of sperm release into mussels in response to sperm release by sneaking males. We discuss the possibility that sexual conflict in oviposition choice occurs in this species. 相似文献
15.
The reproductive cycle of the Antarctic articulate brachiopod Liothyrella uva (Broderip, 1833) is described from monthly samples collected between September 1985 and July 1987 from a population at Signy
Island, Antarctica. Spermatogenesis and oogenesis are described for the first time in this species. Surface dried-tissue masses
for a standard individual (41 mm shell length) were calculated for the digestive diverticula, gut, lophophore and gonad from
monthly dissections of 15 brachiopods. Seasonal patterns, with summer peaks, were observed in the digestive diverticula and
gut. The lophophore and gonad masses did not exhibit seasonal trends. Females showed a sharp decrease in proportion of large
oocytes between October and November in 1986, suggesting spawning during this period. There was no similar decrease during
the same period in 1985. Mean percent spermatozoa measurements revealed a large increase in November 1985 and a rapid decline
in December 1985. This suggested a large spawning event for males in 1985 which was not repeated the following year. These
data indicate large inter-annual differences in reproductive activity as well as differences between males and females. They
also suggest the possibility of sperm storage by females. Brood characteristics were also highly variable. The smallest brooding
female was 31.5 mm in length. Some females brooded more than one developmental stage simultaneously, and variation in brood
size (numbers of embryos or larvae held in the lophophore) and brood composition between individuals was high. All samples
collected throughout the 2 yr period contained some females with broods. The data suggest that the reproductive strategy of
L. uva is highly plastic, and that there may be three reproductive periodicities on seasonal, annual and inter-annual time scales.
Received: 16 May 1997 / Accepted: 2 March 1998 相似文献
16.
Vertical distribution, life cycle, and developmental characteristics of the mesopelagic copepod Gaidius variabilis Brodsky in the Oyashio region were investigated by combining analyses of field copepodite populations with laboratory-rearing
data of egg hatching and naupliar development. Field samplings from five discrete depths between the surface and ≤2000 m were
made approximately every month for 1 year. Most populations of G. variabilis occurred between 600 and 1000 m depth. A modest degree of reversed diel vertical migration behavior and some stage-specific
depth-distribution patterns were noted. All copepodite stages were observed throughout the year, suggesting a year-round spawning
of G. variabilis. From a prominent abundance peak of Copepodite Stage 1 (C1) seen in June to August, together with development times of eggs
and nauplii obtained in laboratory-rearing experiments, the major spawning season was extrapolated to be April to June, the
phytoplankton bloom season. Tracing the peak abundance of each copepodite stage (distinguishing males and females for C4 to
C6), the generation times of males and females were deduced as 2 and 1 year, respectively. All between-stage increments in
terms of wet-, dry-, and ash-free dry weights were greatest in C3/C4, and least in C5/C6 for both males and females. The increments
in C3/C4 and C4/C5 were greater for males than for females, reflecting a longer stage duration of the males. These weights
did not increase in C5/C6 males, possibly because feeding ceased in C6 males. These results for G. variabilis are compared with those for some mesopelagic copepods previously reported from other regions.
Received: 25 October 1999 / Accepted: 20 March 2000 相似文献
17.
Histological examination of gonads of female and male red porgy, Pagrus pagrus, reared in captivity, was carried out in order to describe the main gonadal changes related to gametogenesis and the seasonal changes of environmental factors. The gonadosomatic index (GSI) and the concentration of serum vitellogenin (VTG) were also determined. The frequency distribution of gonad development stages and the GSI and vitellogenin concentration during the annual cycle indicated the separation of the female and male reproductive cycles into three main periods. The autumn period when gametogenesis begins (October-November), the period of exogenous vitellogenesis (December-March) or spermiation (December-March), and the spawning season (March-May). The spawning period coincided with an increase in temperature (15-19°C) and daylength. Serum levels of vitellogenin rose significantly in January, reached a peak at the beginning of the spawning period (March, 405.5 µg ml-1) and remained high until the end of the spawning period (May). 相似文献
18.
Frequency and timing of extrapair fertilisation in the polyandrous red phalarope (Phalaropus fulicarius) 总被引:1,自引:0,他引:1
James Dale Robert Montgomerie Denise Michaud Peter Boag 《Behavioral ecology and sociobiology》1999,46(1):50-56
In sequentially polyandrous bird species, where females mate with different males in succession during a single breeding
season, sperm stored by females can occasionally lead to extrapair fertilisations (EPFs) in clutches cared for by the second
and subsequent males. Thus, we predicted that in red phalaropes (Phalaropus fulicarius) – a sex-role-reversed, sequentially polyandrous, arctic breeding shorebird – EPFs would occur more frequently in clutches
laid later in the breeding season. We used multilocus DNA profiling to examine the frequency and timing of EPFs in a population
of red phalaropes breeding in the Canadian high arctic. Using a technique to determine parentage without maternal DNA, we
inferred that 6 of 70 chicks in 18 broods resulted from EPFs – one extrapair chick in each of 6 broods. These results were
supported by a further analysis using microsatellite DNA. As predicted, broods containing EPFs hatched from clutches laid
significantly later in the season than did broods containing no EPFs. The difference in median hatch dates between broods
with and without EPFs was 9.0 days, or 38% of the entire egg-laying period in that season. For the whole breeding season,
we estimated that 6.5% of chicks were sired by extrapair males, which is similar to extrapair paternity estimates for other
sex-role-reversed birds, but relatively low compared to the majority of socially monogamous species studied so far.
Received: 24 August 1998 / Received in revised form: 18 January 1999 / Accepted: 24 January 1999 相似文献
19.
When females mate with more than one male, the ensuing sperm competition leads to the evolution of male mechanisms that skew
paternity. Males of the yellow mealworm beetle (Tenebrio molitor) transfer a spermatophore to females during copulation, but sperm release and storage occur later. We investigated how the
interval between two matings with different males affects sperm precedence by varying the interval between the copulations
so that the second mating was either: (1) before sperm release from the first spermatophore (<5 min); (2) after sperm release
but before spermatophore ejection (15–20 min); (3) after spermatophore ejection but before sperm storage (4 h), or (4) after
complete sperm storage (24 h). We collected offspring over a period of 2 weeks and determined paternity by protein electrophoresis.
There was second-male sperm precedence in all treatments, but when the interval was <5 min, the second male usually (86% of
cases) had complete sperm precedence (i.e., P
2=1). Investigations into the mechanism of second-male sperm precedence during <5-min mating intervals indicate that sperm
release from the first spermatophore is inhibited, a phenomenon which has not been previously documented.
Received: 31 January 2000 / Revised: 9 June 2000 / Accepted: 26 August 2000 相似文献
20.
Geir Rudolfsen Rudolf Müller Davnah Urbach Claus Wedekind 《Behavioral ecology and sociobiology》2008,62(4):561-567
The mating behavior and reproductive strategies of Alpine whitefish like Coregonus zugensis (Nüsslin) are poorly understood, probably because they spawn in deep water where direct observations are difficult. In this
study, we interpret life-history and sperm quality traits of fish that we caught from their spawning place. We found that
males invest heavily into gonadal tissue (up to 5.6% of their body weight), which is, in comparison to other fish, consistent
with external fertilization, distinct pairing and moderate to high communal spawning, or no pairing and low to moderate communal
spawning. Sperm competition theory and recent experimental studies on other salmonids predict that males optimize ejaculate
characteristics in relation to the costs of sperm and the level of competition they have to expect: dominant males are predicted
to invest less into ejaculate quality and to have slower spermatozoa than subdominant males. We found that spermatozoa of
older males are slower than those of younger males. Moreover, older males have larger breeding tubercles, a secondary sexual
trait that has, in some previous studies, been found to be linked to good condition and to good genetic quality. Our results
suggest that C. zugensis has age-linked reproductive strategies, that multimale spawning is common, i.e., that sperm competition plays a significant
role, and that older males are on average dominant over younger males at the spawning place. 相似文献