Heridas por asta de toro, análisis de 138 casos.

OBJECTIVE: Bull-horn injuries (BHI) are unique and there is reduced published literature about it. We present an analysis of a 11-year BHI case series. METHOD: Study of 138 cases developed during a 11-year period with hospitalization admission greater than 24 hours with diagnosis of BHI/contusion. We classified patients in two groups: group A, patients undergoing procedures under general anaesthesia and group B undergoing procedures under local anaesthesia. Variables: age, sex, date, hospitalization length, main region affected, Comprehensive complication index (CCI, ISS, intensive care unit (ICU) admission, stay and mortality. Statistical analysis: t-Student test, ANOVA, χ2 and linear or logistic regression. RESULTS AND CONCLUSIONS: ISS was related to hospital stay, CCI, ICU admission and type of treatment applied. The comparative statistical analysis of variables between both groups determined a significant difference in age, ISS and hospitalization length, being greater in those belonging to group A. There is a more risk of undergoing surgery by increasing age, ISS and presenting the wounds in thorax-abdomen-pelvis area. CCI may be a good method of quantifying postoperatory morbidity in polytraumatized patients or in other areas besides the abdomen.

OBJETIVO: Las heridas por asta de toro (HAT) poseen características únicas y existe literatura escasa en esta área. Presentamos un análisis de 11 años de pacientes con HAT. MÉTODO: Estudio retrospectivo y analítico de 138 casos durante un periodo de 11 años, de pacientes ingresados durante más de 24 horas por HAT. Clasificamos a los pacientes en dos grupos: grupo A, sometidos a procedimientos bajo anestesia general, y grupo B, sometidos a procedimientos bajo anestesia local. Variables recogidas: edad, sexo, mes del suceso, hospitalización (días), región afectada, Comprehensive Complication Index (CCI), Injury Severity Score (ISS), ingreso y estancia en la unidad de cuidados intensivos (UCI) y mortalidad. Análisis estadístico: t de Student, ANOVA, χ2, regresión lineal y logística. RESULTADOS Y CONCLUSIONES: El ISS se relaciona directamente con la estancia hospitalaria, el CCI, el ingreso en UCI y el tratamiento recibido. Entre ambos grupos se evidenció una diferencia significativa en edad, ISS y estancia hospitalaria, siendo mayores en el grupo A. Existe un mayor riesgo de necesitar cirugía conforme aumentan la edad, el ISS y las heridas en tórax, abdomen o pelvis. El CCI puede ser un buen método para cuantificar la morbilidad posoperatoria en pacientes politraumatizados o con lesiones en otras áreas distintas del abdomen.

X-Y sperm aneuploidy in 2 cattle (Bos taurus) breeds as determined by dual color fluorescent in situ hybridization (FISH).

The present study was undertaken to investigate aneuploidy rates in the sperm populations of 2 cattle (Bos taurus) breeds by using dual color fluorescent in situ hybridization (FISH) with Xcen and Y chromosome-specific painting probes, obtained by chromosome microdissection and DOP-PCR. Frozen semen from 10 Italian Friesian and 10 Italian Brown testing bulls was used for the investigation. For each bull, more than 5,000 sperm were analyzed, for a total of 52,586 and 51,342 sperm cells for the 2 breeds, respectively. The present study revealed - in both breeds - a preponderance of the Y-bearing sperm compared to the X-bearing sperm. Within each breed, a statistically significant variation in the various classes of aneuploidy (XX, YY and XY) was found: differences were found in the Friesian breed among the 3 diploidy classes, and in the Brown breed, among the 3 disomy classes (p < 0.05) as well as among the 3 diploidy classes (p < 0.01). However, the 2 breeds did not differ significantly in the overall mean rates of X-Y aneuploidy (disomy + diploidy) which amounts to 0.162% in the Italian Friesian and 0.142% in the Italian Brown. When meiosis I (MI) and II (MII) errors were compared, statistically significant differences (p < 0.01) were found in the disomy classes and in both breeds, whereas the differences between diploidy classes were not significant. Compared to humans, a lower level of aneuploidy has been found in the domestic species analyzed so far. The present study contributes to the establishment of a baseline level of aneuploidy in the sperm populations of 2 cattle breeds which could be used for monitoring future trends of reproductive health, especially in relation to environmental changes and mutagens.

What does testosterone do for red deer males?

Testosterone has been proposed to have a dual effect, enhancing sexual traits while depressing parasite resistance in males. Here, we test this hypothesis in red deer, examining males from captive populations during the whole annual cycle and males from natural populations during the breeding season. We first explored the effects of body size, age and sampling date on testosterone to avoid confounding effects. Our results show that in captive populations seasonal changes in testosterone levels were mirrored by changes in testes size, and that during the rut there was a strong correlation between both. In natural populations, males with higher testosterone levels had larger testes, improved sperm quality, smaller burr diameter, stronger antlers, higher haematocrit levels, and increased nematode parasite load. By contrast, no significant relationship was found between testosterone and spleen size or tick parasite load. We conclude that testosterone (i) improves males' reproductive investment and physical stamina, (ii) improves antler strength but reduces burr diameter, and (iii) imposes a cost in terms of depressed parasite resistance.

Superovulation and in vitro oocyte maturation in three species of mice (Mus musculus, Mus spretus and Mus spicilegus).

Mouse oocytes can be obtained via superovulation or using in vitro maturation although several factors, including genetic background, may affect response. Our previous studies have identified various mouse species as models to understand the role of sexual selection on the evolution of sperm traits and function. In order to do comparative studies of sperm-oocyte interaction, we sought reliable methods for oocyte superovulation and in vitro maturation in mature females of three mouse species (genus Mus). When 5 IU pregnant mare's serum gonadotrophin (PMSG) and 5 IU human chorionic gonadotrophin (hCG) were injected 48 h apart, and oocytes collected 14 h post-hCG, good responses were obtained in Mus musculus (18+/-1.3 oocytes/female; mean+/-S.E.M.) and Mus spretus (12+/-0.8), but no ovulation was seen in Mus spicilegus. Changes in PMSG or hCG doses, or longer post-hCG intervals, did not improve results. Use of PMSG/luteinizing hormone (LH) resulted in good responses in M. musculus (19+/-1.2) and M. spretus (12+/-1.1) but not in M. spicilegus (5+/-0.9) with ovulation not increasing with higher LH doses. Follicular puncture 48 h after PMSG followed by in vitro maturation led to a high oocyte yield in the three species (M. musculus, 23+/-0.9; M. spretus, 17+/-1.1; M. spicilegus, 10+/-0.9) with a consistently high maturation rates. In vitro fertilization of both superovulated and in vitro matured oocytes resulted in a high proportion of fertilization (range: 83-87%) in the three species. Thus, in vitro maturation led to high yields in all three species. These results will allow future studies on gamete interaction in these closely related species and the role of sexual selection in gamete compatibility.

Use of a neuroleptic in assisted reproduction of the critically endangered Mohor gazelle (Gazella dama mhorr).

Stress is a limiting factor in assisted reproduction in wild animals maintained in captivity and measures to reduce it should improve reproductive success. The effect of the long-acting neuroleptic (LAN) perphenazine enanthate was assessed on ovarian stimulation for the recovery of immature oocytes from Mohor gazelle (Gazella dama mhorr) and their subsequent in vitro maturation, fertilization and embryo culture. The viability of embryos after transfer was also examined. Perphenazine enanthate decreased activity levels and facilitated handling of treated animals when compared to controls. LAN-treated animals showed a more regular pattern of respiratory and heart rates and body temperature than controls; no major differences were found in hematological and biochemical parameters between groups. Perphenazine-treated females had lower plasma cortisol levels during the days of intense handling. No significant differences were found in the number of punctured follicles and recovered oocytes between groups. The percentage of mature oocytes per female was significantly higher in the LAN-group. Fertilization and cleavage rates were not significantly different between groups. Embryos developed in culture but none reached the blastocyst stage, and those transferred to the oviduct of synchronized recipients did not develop to term. In conclusion, treatment of females with perphenazine enanthate during ovarian stimulation did not have negative effects on maturation, fertilization and embryo development in vitro. Moreover, an increase in oocyte maturation rate per female was observed. Thus, the use of LANs could be useful to alleviate the effects of handling-stress during assisted reproductive procedures in wild ungulates.

In vitro oocyte maturation, fertilization and culture after ovum pick-up in an endangered gazelle (Gazella dama mhorr).

The recovery of immature oocytes followed by in vitro maturation, fertilization and culture (IVMFC) allows the rescue of biological material of great genetic value for the establishment of genetic resource banks of endangered species. Studies exist on sperm cryopreservation of endangered Mohor gazelle (Gazella dama mhorr), but no work has been carried out yet on oocyte collection, fertilization and culture in this or related species. The purpose of this study was to develop a protocol for ovarian stimulation for the recovery of oocytes and subsequent IVMFC in the Mohor gazelle using frozen-thawed spermatozoa. Ovum pick-up was performed after ovarian stimulation with a total dose of 5.28 mg of ovine FSH. A total of 35 oocytes were recovered from 56 punctured follicles (62%) (N=6 females). Out of 29 cumulus-oocyte complexes matured in vitro, 3% were found at germinal vesicle stage, 7% at metaphase I, 21% were degenerated, and 69% advanced to metaphase II. Fertilization and cleavage rates of matured oocytes were 40 and 30%, respectively. Embryos cleaved in vitro up to the 6-8 cell stage but none progressed to the blastocyst stage, suggesting the existence of a developmental block and the need to improve culture conditions. Although more studies are needed to improve hormonal stimulation and oocyte harvesting, as well as IVMFC conditions, this study demonstrates for the first time the feasibility of in vitro fertilization with frozen-thawed semen of in vitro matured oocytes collected by ovum pick-up from FSH-stimulated endangered gazelles.

Inbreeding and reproduction in endangered ungulates: preservation of genetic variation through the Organization of Genetic Resource Banks.

There is a constant increase in the number of species suffering marked reductions in population size. This reduction in size and the lack of genetic flow may lead to a decrease in genetic variability and to matings between close relatives (i.e. inbreeding) with an ensuing reduction in fitness. It is thus important to understand the mechanism underlying the deleterious effects of inbreeding and to develop reproductive biotechnologies that will allow the reduction of inbreeding depression by facilitating gene exchange between populations. The study of three endangered species of gazelles, Cuvier's gazelle (Gazella cuvieri), Mohor gazelle (Gazella dama mhorr) and dorcas gazelle (Gazella dorcas neglecta) has revealed that inbreeding negatively affects several semen parameters (motility, sperm morphology, acrosome integrity). Semen cryopreservation has been achieved in the three species but success varies depending on the diluent employed and the level of inbreeding. Artificial insemination of Mohor gazelles have led to the birth of the first gazelle born using frozen-thawed semen but improvements are needed before this technology can be applied on a routine basis for the genetic management of the populations. Collection of oocytes after ovarian stimulation, followed by in vitro maturation, fertilization and culture has met with some initial success in the Mohor gazelle. These, together with other reproductive technologies, will offer an invaluable help in preserving the maximum of genetic diversity of these and related endangered ungulate species.

The application of reproductive technologies to natural populations of red deer.

Over the past decade, there has been increasing interest in the application of reproductive technology to the conservation and management of natural populations of deer. The application of assisted reproduction technologies within natural population of deer is in its infancy. However, its future potential is enormous, particularly in relation to genetic management or conservation. This paper reviews the present state of such technologies for a wild subspecies of red deer, the Iberian red deer (Cervus elaphus hispanicus), by discussing the major components of oestrous synchronization, semen collection/cryopreservation and insemination techniques. In addition, findings made during the course of studies on natural populations have enormous potential for the understanding of novel reproductive mechanism that may not be uncovered by livestock or human studies. A summary of these results are also reviewed here.

Sperm competition influences sperm size in mammals.

Among mammals sperm competition leads to selection for increased sperm numbers but it is not known whether it also leads to changes in sperm size. Two contrasting theoretical predictions have been made. The first hypothesis relies on the assumption that there is a trade-off between sperm numbers and sperm size and predicts that, in species confronting sperm competition, there will be a concomitant decrease in sperm size as sperm numbers increase. In contrast, the second hypothesis suggests that longer sperm may outcompete rival sperm; if longer sperm may swim faster, they will reach the ova sooner and will be selected when sperm competition prevails. We tested these hypotheses in both primates and rodents. We report that males from species in which females mate promiscuously have longer sperm than species in which females mate with one male. In addition, we also found that sperm length is positively correlated with maximum sperm velocity. Our findings thus support the view that longer sperm may be adaptive in the context of sperm competition.

Coevolution between male ejaculates and female reproductive biology in eutherian mammals.

Among eutherian mammals, sperm competition has favoured the evolution of high sperm numbers and long spermatozoa, but it cannot account for all the variability observed. In this paper we argue that differences in female reproductive biology may also have influenced the evolution of sperm numbers as well as several other sperm traits. Sperm fertile lifespan is positively related to the interval between the onset of oestrus and ovulation, suggesting that males try to ensure that their spermatozoa will remain capable of effecting fertilization until ovulation occurs. We tentatively suggest that variation in sperm fertile lifespan may be related to differences in sperm size. The duration of capacitation is positively related to sperm fertile lifespan, suggesting that the time constraints imposed by the female have also influenced the duration of this process. When females possess long oviducts in relation to their body size, males produce relatively high sperm numbers to counteract the greater losses incurred. Contrary to our prediction, sperm size does not seem to be related to the thickness of the zona pellucida.

A comparative study of ejaculate traits in three endangered ungulates with different levels of inbreeding: fluctuating asymmetry as an indicator of reproductive and genetic stress.

We studied three closely related species of endangered gazelles (Gazella dorcas, Gazella dama and Gazella cuvieri) with different levels of inbreeding in order to determine at which intensities inbreeding influences ejaculate traits. We also examined whether fluctuating asymmetry (FA) is a reliable indicator of genetic as well as reproductive stress. Our results show that, within each population, the individual coefficient of inbreeding is inversely related to ejaculate quality only in the species with the highest levels of inbreeding (G. cuvieri). In addition, FA is a reliable indicator of individual levels of inbreeding in both the species with the highest levels of inbreeding (G. cuvieri) and the species with intermediate levels of inbreeding (G. dama). Thus, FA appears in individuals whose levels of inbreeding are still not high enough to affect male reproductive potential and should therefore be considered a sensitive indicator of genetic stress. Finally, FA is also a reliable indicator of male reproductive stress since it is related to individual semen quality in all the species studied.

Inbreeding, fluctuating asymmetry, and ejaculate quality in an endangered ungulate.

An ever-increasing number of species are suffering marked reductions in population size as a consequence of human activities. To understand the impact of these changes it is essential to assess how small population size affects individual fitness and the viability of populations. This issue acquires special relevance among endangered species in which numbers have decreased to such an extent that captive breeding must be established with a few founders. A major risk associated with small population size is inbreeding depression. The effects of inbreeding upon male reproductive traits are the subject of an ongoing controversy, since the evidence linking lack of genetic variability and poor ejaculate quality at the population level has been criticized recently by several authors. We report that among Gazella cuvieri males, inbreeding coefficient shows a strong inverse relationship with ejaculate quality. Furthermore, the degree of fluctuating asymmetry is positively related to the coefficient of inbreeding and negatively related to the proportion of normal sperm, suggesting that it is a reliable indicator of genetic stress and of ejaculate quality.

Morphometrically-distinct sperm subpopulations defined by a multistep statistical procedure in ram ejaculates: intra- and interindividual variation.

The existence of sperm subpopulations within the mammalian ejaculate has now been widely recognized. However, to the best of our knowledge, no data exist regarding the existence of sperm morphometric subpopulations within the ovine ejaculate. Computer assisted sperm morphometry analysis (ASMA) data and clustering methods were used in this study to identify sperm-head subpopulations in ram semen. Two experiments were carried out. In Experiment 1, ejaculates from 226 mature rams of the Manchega breed belonging to 36 different herds were used. A minimum of 100 sperm heads were analyzed from each male and eight morphometric characteristics for each individual sperm were recorded. Subpopulation analysis was performed in sequential steps: variable group analysis and correlation analysis to select which morphometric characteristics to use in cluster analyses; nonhierarchical clustering analysis using sperm head length and p2a (also known as roundness) shape factor as initial classificatory variables; and hierarchical clustering analysis to obtain the final number of clusters. The clustering analyses, based on 26,306 individual cells, revealed the existence of four sperm subpopulations (SP1, SP2, SP3 and SP4) with different morphometric characteristics. Significant differences in the proportion of spermatozoa in the SP1 and SP3 were found between rams belonging to different herds. In Experiment 2, the intra- and intermale variability on the distribution of sperm subpopulations was assessed. Three ejaculates from each of 21 rams were collected and the same multistep clustering analysis was performed. For all subpopulations defined, the intermale variability resulted in high values, being the intramale variability much lower. This fact would allow the use of sperm head morphometry to characterize a male and might provide valuable information to asses its fertility. In conclusion, our results show that using computer assisted sperm morphometry analysis and multivariate cluster analyses, four sperm subpopulations with different head phenotype were identified in ram ejaculates.

Effect of storage of domestic cat (Felis catus) epididymides at 5 degrees C on sperm quality and cryopreservation.

Postmortem sperm recovery from the epididymides may constitute a powerful tool for the conservation of valuable genetic material. The domestic cat (Felis catus) is a good model for wild felids and, using this model, we have explored the effect of epididymides storage time on sperm motility and percentage of intact acrosomes upon sperm recovery and after cryopreservation. We also examined the effect of time of sperm equilibration with glycerol before freezing on sperm motility and the percentage of intact acrosomes. Motility varied between sperm recovered from epididymides that were stored for different times. Significant differences were seen in the sperm motility index (SMI) before freezing (55.91+/-2.02, 48.21+/-1.47, and 43.03+/-1.32) and after thawing (51.81+/-3.02, 41.90+/-2.14, and 42.35+/-1.95) of sperm recovered from epididymides stored for 0, 48, or 72 h, respectively. The percentage of intact acrosomes did not vary significantly with storage time (average 60.33+/-1.38% before and 52.50+/-1.91% after freezing, respectively). The percentage of normal sperm after different storage times did not differ (average 19.22+/-1.25% normal sperm after recovery). When epididymides were stored for 72 h, time of sperm equilibration with glycerol (30 vs. 120 min) resulted in significant differences in both motility (SMI=39.17+/-2.76 and 45.00+/-2.65, respectively) and the percentage of intact acrosomes (45.76+/-4.91% and 60.67+/-3.64%, respectively) after thawing. In conclusion, best results are achieved when sperm are recovered from epididymides within 24h of cool storage and when they are equilibrated with glycerol during 120 min before freezing. The current results should be useful in the further development of techniques for the rescue and cryostorage of epididymal spermatozoa of endangered felids.

Male reproductive traits, semen cryopreservation, and heterologous in vitro fertilization in the bobcat (Lynx rufus).

There is limited information on bobcat ejaculate traits and sperm cryopreservation and fertilizing ability. Bobcats were electroejaculated under general anesthesia in November (autumn) and April (spring), and endocrine and sperm traits were characterized. Testosterone (mean+/-SEM: 0.90+/-0.15 ng/mL) was not different between sampling times, but cortisol (average: 13.95+/-1.73 microg/dL) was significantly higher in April. Average number of spermatozoa was 10.0+/-3.4 x 10(6) sperm/ejaculate, with values being significantly higher in April. Sperm motility (average 55.7+/-5.8% motile sperm) was not different between sampling times. The proportion of normal spermatozoa in the ejaculate (average: 14.7+/-2.1%) was significantly higher in April, but the percentage of spermatozoa with intact acrosomes (average: 43.7+/-3.8%) was significantly higher in autumn. Spermatozoa were cryopreserved in a Tes-Tris-based diluent (TEST) or Biladyl, both containing 20% egg yolk and 4% glycerol. Diluted sperm were loaded into straws, refrigerated using a programmable thermoblock with a dry chamber, frozen in nitrogen vapors, thawed, and incubated in F-10 medium with 5% fetal bovine serum for up to 3h. After cryopreservation in TEST, there were about 50% motile sperm upon thawing, and survival was high during incubation post-thaw. Cryopreservation in Biladyl led to similar results, but motility decreased substantially during incubation post-thaw. Bobcat spermatozoa fertilized domestic cat oocytes matured in vitro. Fertilization rates were higher for sperm collected in April and cryopreserved in TEST (46%) than for those cryopreserved using Biladyl (<3%). Fertilized oocytes cleaved in culture, and some (27%) reached the morula stage. This study has allowed us to gain further baseline information on bobcat reproduction, explore sperm cryopreservation conditions, and show that fertilizing capacity can be tested using in vitro-matured cat oocytes. These results will be important for future conservation efforts.

Effect of egg yolk, cryoprotectant, and various sugars on semen cryopreservation in endangered Cuvier's gazelle (Gazella cuvieri).

Cryopreservation of spermatozoa from endangered species is a valuable tool for genetic management. Previous studies showed the feasibility of cryopreservation of spermatozoa from various endangered gazelles but have also revealed difficulties with available protocols for semen freezing in Cuvier's gazelle (Gazella cuvieri). Experiments were carried out to investigate the effect of (a) 5% or 20% egg yolk or 4% or 6% glycerol, and (b) addition of sugars (glucose, fructose, lactose and raffinose) on cryopreservation using a Tes-Tris-based diluent (TEST). A diluent containing 13.5% raffinose, 5% or 20% egg yolk, and 6% glycerol (REYG) was also evaluated. Semen was obtained by electroejaculation from 22 G. cuvieri males. Diluted samples were loaded into 0.25 ml straws, cooled to 5 degrees C over 1.5h (-0.16 degrees C/min), equilibrated at that temperature for 2h, frozen in nitrogen vapours for 10 min and plunged into liquid nitrogen. Subsamples were assessed for motility and acrosome integrity upon collection, after refrigeration-equilibration, after freezing and thawing, and 2h after thawing. Use of TEST with 20% egg yolk or with 4% glycerol led to worse motility preservation, whereas TEST with 5% egg yolk and 6% glycerol led to better results. Addition of fructose, lactose or raffinose to TEST resulted in similar or worse preservation of motility than inclusion of glucose. On the other hand, use of a raffinose-based medium with 20% egg yolk and 6% glycerol (REYG) afforded better preservation of motility than use of TEST. With REYG, 20% egg yolk was better than 5% egg yolk for motility preservation. Differences were noted between males in their responses to cryopreservation when using different egg yolk or glycerol concentrations. Moreover, spermatozoa from most males exhibited better cryopreservation with REYG although some were better cryopreserved in TEST. The raffinose-based diluent thus represents an improvement over previous results but more work is needed to better characterize cryopreservation conditions for future routine banking of Cuvier's gazelle spermatozoa.

Differences in fertility and suckling patterns between primiparous and multiparous rhesus mothers (Macaca mulatta).

Primiparous females gave birth around the same time as multiparous nonlactating females, and earlier than did multiparous lactating females. No differences in birth sex ratio were found between primiparous and multiparous females. During the breeding season following birth, primiparous mothers returned to oestrus later than did multiparous mothers, and while few primiparous mothers conceived successfully during that season, most multiparous mothers did. Primiparous females suckled their infants more frequently than did multiparous females at all ages; infants of primiparous females also made more nipple contacts per bout, and had shorter sucking bouts. When mothers came into oestrus, suckling frequency drastically increased for primiparous females, but not for multiparous females, magnifying the differences between the two groups. After the first oestrus, suckling frequency declined for all mothers, but multiparous mothers had consistently lower suckling frequencies than did primiparous mothers. The high suckling frequency, and numerous nipple contacts per bout, found among primiparous mothers are likely to be related to the low reproductive chances that these females faced during the breeding season. Multiparous mothers seemed to compensate for their low suckling frequency by lengthening the suckling bouts, and this suckling pattern did not hinder their reproduction. It is argued that primiparous mothers might have to suckle their infants more frequently because they can only produce milk at slow rates, being in this way forced into a reproductively inhibiting suckling pattern. However, the delay in subsequent reproduction could be ultimately advantageous for primiparous mothers if it enhanced infant survival, and allowed the mothers to regain physical condition before reproducing again.

Changes in female reproductive condition following male take-overs in a colony of hamadryas and hybrid baboons.

This paper describes and discusses events observed in the Madrid colony of hamadryas and hybrid baboons, when a novel group of 3 adult males, 3 adult females and 1 unweaned infant was introduced to the resident colony comprising 12 adult females, 11 juveniles and 6 unweaned infants. Novel males took over resident adult females in any reproductive condition, and all acyclic females (i.e. lactating, pregnant and immature) exhibited a dramatic enhancement of sexual activity. Lactating females shortened their postpartum amenorrhoea periods and resumed oestrous cycles around day 14 following the introduction of the novel males, without infanticide occurring. Their return to breeding condition was not affected by the age of their current infant or the day they were taken over by the males. A female in an early stage of pregnancy aborted spontaneously and resumed oestrus on day 26. The other pregnant female significantly shortened her gestation time, delivered a viable infant on day 13, and resumed breeding activity 39 days post-partum (on day 52), while suckling her infant. A cycling female adopted and suckled a 74-day-old infant, continued showing oestrous cycles and conceived. Immature females reached menarche significantly earlier than expected and only then joined one of the newly established harem units. It is argued that the observed enhancement of sexual activity was not imposed by the males' aggressive behaviour but rather was a spontaneous female response to male novelty. This single causal factor was potent enough to override the role that nutrition and lactation normally play in the control of the females' reproductive activity. Differences in latency until the appearance of the response were probably due to the different constraints imposed by the female's current reproductive state. It was also hypothesized that when (a) sexual swellings are attractive to males, (b) novel males are especially active in the process of bonding with new females, and (c) males are important sources of coalitionary support, females might by developing sexual swellings compete more successfully against other females and attain a higher position in the female hierarchy of the newly established unit. This would have the ultimate effect of increasing their potential reproductive success. In several cases females did gain socially by coming into oestrus, but attained no immediate reproductive advantage.

Mechanisms of sperm competition: Linking physiology and behavioural ecology.

Sperm competition has received a great deal of attention from behavioural ecologists because it is the ultimate form of male-male competition, and may also be important for female choice. It is becoming clear that the adaptive value of the behavioural strategies of males and females will not be fully understood until we have a better understanding of the physiological mechanisms that come into play after copulation. We now have enough information to compare the underlying mechanisms in birds and mammals and to relate these to the way in which sperm competition operates in both groups. To integrate this knowledge, the boundaries between behavioural ecology and physiology will have to be crossed in what promises to be a most fruitful enterprise.

The evolution of eutherian spermatozoa and underlying selective forces: female selection and sperm competition.

We have examined sperm morphology and dimensions in Eutherian mammals. In most Eutherians, sperm heads are round or oval and spermatozoa have short tails (average sperm length about 65 microns; range = 33-121 microns). Rodents, however, clearly depart from the typical Eutherian pattern in that they show a broad array of head morphs and an extreme range of sperm dimensions (35-250 microns). In order to trace the evolutionary changes that rodent sperm have undergone, we have used phylogenetic relationships based on biogeographical, morphological, chromosomal and genic data, and we have superimposed onto them the information available on sperm traits. Analyses were carried out for five rodent groups on which enough information was available. The evolutionary trends which emerged from these studies have two main points in common: throughout evolution spermatozoa have become enlarged and morphologically more complex, and this process seems to have taken place independently in different lineages. A general model was developed which outlines the different evolutionary pathways that rodent sperm have undergone. The adaptive significance of the increase in head complexity and the elongation of the sperm tail remains obscure. We have integrated information from evolutionary, physiological and behavioural studies to address this issue. We argue that two main selective forces may have favoured these changes: female selection within the reproductive tract and sperm competition. The female tract represents a formidable barrier for spermatozoa and its provides an environment where numerous interactions take place. The extent of these barriers and the complexity of these poorly understood interactions suggest that females may be exercising a strong selection, which may enable them to favour particular types of spermatozoa or ejaculates from particular males. Throughout their evolution males must have evolved adaptations to overcome these barriers, and the conflicting interests of choosy females. Sperm competition is a potent evolutionary force among mammals, which has influenced not only the evolution of sperm numbers but also changes in sperm dimensions. Thus, sperm competition has favoured the elongation of the sperm tail, which has led to the attainment of faster swimming speed, an important factor when sperm from rival males compete to reach the ova first.