Familial influences on ovulatory function in common marmosets (Callithrix jacchus)

Previous studies have indicated that many, but not all, female common marmosets (Callithrix jacchus) housed with their natal families undergo social suppression of ovulation. In this study, we further characterized ovulatory activity in common marmoset daughters to determine the prevalence of social suppression of ovulation and to elucidate familial influences on daughters' ovarian activity. Blood samples were collected twice weekly from each of 46 daughters for 5–12 months, usually beginning when the daughters were 12 months of age. Plasma progesterone concentrations indicated that 46.3% of daughters in intact natal families ovulated at least once, with the age at first ovulation averaging 17.2 months; however, none of these daughters became pregnant. Daughters' ovulatory cycles showed several significant differences from those of older females housed with unrelated adults, including longer periods between successive luteal phases, shorter luteal phases, and lower peak and mean luteal-phase progesterone levels. Daughters were significantly more likely to ovulate in families in which the mother was experimentally prevented from sustaining pregnancies, and in families in which the father had been replaced by an unrelated adult male and when the daughter was approximately 10–11 months of age. Daughters in families containing an older sister never ovulated; in contrast, those with a female littermate were not less likely to ovulate than were other daughters, but had more sporadic ovarian cycles and significantly lower mean luteal-phase progesterone levels. These results confirm and extend previous findings that up to half of female common marmosets may ovulate while housed with the natal family but that virtually none sustain pregnancies, suggesting that suppression of ovulation is only one of several components of reproductive failure. Furthermore, these results demonstrate that daughters' likelihood of ovulating, as well as the endocrine profiles of their ovulatory cycles, can be modulated by numerous social influences within the family. Am. J. Primatol. 41:159–177, 1997. © 1997 Wiley-Liss, Inc.     

Pair-bond formation and breeding success in the common marmosetCallithrix jacchus jacchus

The breeding records from 22Callithrix jacchus jacchus females aged 13–23 months were examined. It was evident that females aged more than 18 months when first paired bred sooner, as did females paired with sexually experienced males. A detailed behavioral investigation of nine newly formed pairs was carried out for 10 weeks. Males showed more following, sniffing, tail-raised presents, and affectional behavior than their mates, while females showed more soliciting. Only females gave the submissive vocalization (ngÄ). This shows that there is a degree of sexual dimorphism in the behavior of this monogamous monkey. Four of the nine pairs failed to conceive within 12 weeks of pairing;the females of these pairs behaved more submissively than successful breeders, showing more ngÄ and less bristling and sexual behavior. In all cases the four females were housed in close proximity to dominant relatives and this was considered to be a significant factor.     

The endocrinology of puberty and reproductive functioning in female cotton-top tamarins (Saguinus oedipus) under varying social conditions

Sexual maturation and fertility were assessed in fourteen cotton-top tamarin (Saguinus oedipus) females under various social conditions. Six tamarin females (20-28 mo of age) showed a suppression of fertility while living with their families. Hormonal profiles demonstrated low, acyclic levels of urinary luteinizing hormone (LH) and estrone-conjugates (E1C). A rapid onset of ovarian and pituitary cyclicity occurred when four of the six females were removed from their families and paired with an unrelated male. In one female, an ovulatory LH peak occurred as early as eight days after pairing and resulted in conception and full-term pregnancy. Two of the six females were housed in total isolation for 30 days following their removal from the family and prior to pairing. Gradual increases in hormone concentrations occurred during isolation; however, there was no ovarian cyclicity until each female was paired with an unrelated male. In all six females, conception occurred before or as a result of the third ovulatory cycle. Partial isolation of a 36-mo-old female resulted in elevated LH and E1C levels, but cyclicity was not observed until the female was paired with an unrelated male. These findings indicate that removal of a female from the family alone does not initiate ovarian cycling. Sexual maturation, or puberty, occurs in female tamarins living with their families between 15 and 17 mo of age when mean LH and E1C levels began to increase. However, when a female is removed and paired at 9 mo of age with an unrelated male, elevated levels of LH and E1C may be seen by 10 and 11 mo of age. Our findings indicate that a suppression of fertility occurs in cotton-top tamarins living with their families, but that reproductive suppression does not affect the process of sexual maturation. Both removal from the family environment and stimulation by an unrelated male tamarin were necessary to induce normal reproductive activity. An acceleration of puberty occurred when a female tamarin was removed from her family early in development and paired with a male.     

Parent-daughter relationships and social controls on fertility in female common marmosets,Callithrix jacchus

This study examined the reproductive status of mothers and daughters to determine if parent-eldest daughter interactions would influence the daughter's fertility in the cooperatively breeding common marmoset, Callithrix jacchus. Twice weekly fecal samples were collected for hormonal analyses from seven daughters and their mothers and analyzed for cortisol, estradiol, and progesterone by EIA. Behavioral data were collected three times weekly while the daughters were under three conditions: natal family, after removing from the family and paring with a novel male, and after removing from the paired condition and placed back with the family (renatal). Under the natal condition, five of the seven daughters exhibited ovarian cycles while their mother was pregnant or displaying ovarian cycling. The five cycling daughters spent significantly more time initiating affilative behaviors with their mothers than with their fathers and showed significant changes in their behavior over the length of the ovarian cycle. However, aggression, submission, and sexual behaviors were very low for daughters in the natal phase. No differences between cortisol levels were found for a daughter and her mother. Cortisol levels showed a significant and sustained increase upon pairing within the first 20 days. All females but one cycled while paired. Six of the seven females were accepted back into the family after pairing and five of the seven females were ovulating. These results suggest that marmoset daughters are not necessarily reproductively suppressed while living with the family. Additionally, these data suggest that female marmosets that leave their family to explore mating opportunities with other groups may return to their family without reproductive or aggressive consequences.     

Persistent vaginal cornification in mice treated with estrogen prenatally.

Twelve of 14 female mice of the ICR strain which had received a single injection of 50 mug estradiol-17beta on day 17 of fetal life exhibited irreversible cornification or stratification of the vaginal epithelium which persisted after ovariectomy until sacrifice performed 42-48 days later. Eight of the 12 mice had corpora lutea in their ovaries removed at 3-5 months of age. A similar injection of estradiol on day 15 of fetal life induced irreversible cornification or stratification of the vaginal epithelium in 6 of 12 females and only one of the 6 had corpora lutea in its ovaries when removed at 3-5 months. Mice given the same dose of estradiol on the day of birth or at 3 days of postnatal age invariably had ovaries bearing follicles of varying sizes and hypertrophied interstitial tissue but no corpora lutea. Changes in the vaginal epithelium in these animals were less remarkable as compared to that in prenatally treated mice.     

Social influences on estrogen excretion and ovarian cyclicity in saddle back tamarins (Saguinus fuscicollis)

The effects of different social living conditions on estrogen excretion and on the ovarian cycle of saddle back tamarins were investigated. Urinary estrogens were monitored as indices of ovarian cyclicity in groups of adult females living under the following experimental conditions: (1) five parous females, each living with an adult castrated male (in one of the females plasma estradiol and progesterone were also measured); (2) five adult daughters living with their families. Each daughter was then removed from her family and paired with a vasectomized male. After pairing, scent marks collected from the family were introduced daily to one of the daughters and her mate. Scent exposure was then discontinued and hormone excretion measured for several weeks. The remaining four daughters were not exposed to family scent. The females living with castrated males showed urinary estrogen cycles of an average length of 17.5 ± 1.0 days. The plasma estrogen cycle was of the same length. The females studied under condition 2 showed low, noncycling estrogen levels while living in their families. They responded to pairing with an increase in the level of urinary estrogens, and four out of five showed regular estrogen cyclicity. The fifth female exposed to family scent marks after pairing also showed an increase in urinary estrogens. However, as long as scent transfer was maintained, no cycle was observed. Estrogen excretion increased again, and cyclicity commenced when scent transfer was discontinued. It is concluded that ovarian estrogen production is suppressed and cyclicity does not occur as long as daughters live in their families. Release from suppression and perhaps stimulation by the male cause a rapid increase in estrogen levels and the onset of cyclicity. Chemical stimuli produced by the family, perhaps particularly by the mother, may be involved in reproductive suppression.     

Efficacy and effects of short- and medium-term contraception in the common marmoset (Callithrix jacchus) using melengestrol acetate implants.

This study examines the effect of melengestrol acetate (MGA) implants on reproductive function and various biochemical parameters, ovarian activity, and uterine morphology in ten female common marmosets implanted for either 6-8 or 19-21 months. Measures of body weight, concentrations of urinary glucose and blood liver enzymes were taken. Ovarian activity was assessed by analysis of urinary progestin levels and ultrasound examinations of the ovaries. Ultrasonography was also used to evaluate uterine morphology. MGA was highly effective in preventing pregnancies in the study animals. No changes in biochemical parameters were found; however, seven females developed a substantial weight gain during the study. Follicular development was not suppressed, as indicated by the presence of antral follicles, luteinized structures, and elevated urinary progestin levels. The uteri of the MGA-treated subjects were moderately enlarged with a thickened endometrium that showed a marked change in structural appearance indicative of hypertrophy and decidualization. After implant removal these changes quickly disappeared and all females ovulated within 3 weeks and conceived within 4 months post-treatment. MGA appears to be an acceptable contraceptive in the marmoset, although non-steroidal methods should be evaluated as possible potential alternatives.     

Diurnal Variation in Scent Marking Behavior in Captive Male and Female Common Marmosets, Callithrix jacchus

Chemical communication by scent-marking behavior in New World primates is used to prevent the access of potential competitors to a territory, to identify food resources and the reproductive condition of mates, among others. In common marmosets, primates of the Callitrichidae family, this behavior also occurs as olfactory identification of an individual or of the reproductive status of females. Despite this information, the diurnal variation and gender differences in the profile of this behavior remain to be investigated. The aims of this study were to establish the diurnal profile of the distribution of this behavior and the influence of the sex of markers. We used 18 adult common marmosets, Callithrix jacchus, 10 males and 8 females from 6 family groups (6 fathers and 4 sons; 4 mothers and 4 daughters). The frequency of scent-marking behavior was recorded for each animal over a period of 8 days, twice a week, for 4 weeks, starting when the animals left the nest box (approximately at 05:00 a.m.) until the end of the photophase, at about 05:00 p.m. A MANOVA test was performed to compare the frequency of scent-marking behavior at 2 hour intervals using pooled data for males and females. The results showed that significantly higher levels of scent-marking behavior occurred during the 03:00-05:00 p.m. interval compared to all other intervals. Lower values were recorded during the 11:00-13:00 interval and an effect of the sex factor was also found, with the values being higher for females than for males, although a significant difference was recorded only for the 07:00-09:00 interval. Minimal values for males were recorded during the 07:00-09:00 interval, whereas minimum values for females were recorded during the 11:00-13:00 interval. However, the highest values for both sexes continued to occur during the 15:00-17:00 interval. These results suggest that scent marking behavior in common marmosets has a preferential incidence at the end of the day and this might be occurring in association with feeding behavior. At this time these animals usually forage more to prepare for the night's fast. Since these animals can discriminate chemical clues as long as 24 hours after they have been left, the higher incidence of this behavior at this time probably will assure that the animals will localize feeding resources used on the preceding day. Significant elevation of scent marking behavior in females in relation to males was found only at 07:00-09:00 interval and seems to be associated with signalizing of reproductive status, preferential access to foraging or both.     

Onset of plural cooperative breeding in common marmoset families following replacement of the breeding male

Common marmosets, Callithrix jacchus, are usually characterized as singular cooperative breeders, with only a single, dominant female reproducing in each group. Anecdotal reports, however, have described two females breeding concurrently when an unrelated male joins their group. We tested the hypothesis that incorporation of an unrelated adult male into a family systematically leads to the onset of reproductive activity in a daughter and investigated the underlying mechanisms. We collected hormonal and behavioural data from mothers and their eldest daughters before and after the father was removed from the family and either replaced by an unrelated male (N=11) or immediately returned to the family (N=7). Variation between daughters in the occurrence of ovulatory cyclicity was not associated with the presence of an unrelated male but was closely linked to daughters' relationships with their mothers: only anovulatory daughters behaved submissively towards their mothers. Daughters never engaged in sexual behaviour with their fathers, but most did so with unrelated males. Similarly, daughters never conceived in intact natal families but did so in eight of 11 families containing an unrelated male. In six of these families, the mother and daughter bred concurrently. Thus, incorporation of an unrelated adult male into a marmoset family may frequently lead to the onset of plural breeding by activating sexual behaviour in a daughter; however, daughters ovulate only if they are not behaviourally subordinate to their mothers. Therefore, both inbreeding avoidance and rank-related reproductive suppression may constrain reproduction in marmoset daughters and contribute to maintenance of singular breeding.     

海南省鼻咽癌三个高发家系报告

本文调查了鼻咽癌聚集的10个家系。在3个高发家族中,家系1两代11人中有4 人患鼻咽癌;家系2同代6人中有3人患鼻咽癌;家系3同胞5人中有3人患鼻咽癌。我们从肿瘤流行病学、病理类型及其血缘关系作了分析,认为鼻咽癌具有垂直和水平的家族发生 倾向,支持鼻咽癌有遗传倾向的看法。 Abstract:We studied the genealogy with nasopharyngeal carcinoma(NPC)and found 25 patients (18 males,7 females)with NPC in 10 families,aged from 13 to 60.The bron of the same parents were 12 patients,accounting for 48% among these patients.Both male and female patients were found in five families;the patients in four families were all male;there were all female patients in the only one family;At the sametime,21 patients with NPC were the first kinsfolk in 8 families,accounting for 84%.Besides,we looked into 3 families with high incidence;there were 4 out of 11 family members suffering from NPC in the first genealogy in 2 generations;3 of 6 brons of the same parents were ill with NPC in the third genealogy.Based on the studies of cancer epidemiology,pathology and genealogy,our results suggested that the family incidence of NPC had vertical and horizontal thndency,and that genetic factors played a decisive role in NPC incidence.     

Social environment and reproduction in female pouched mice, Saccostomus campestris

Pouched mice were kept under controlled conditions of illumination (10D:14L) and temperature (22 +/- 2 degrees C). Age at vaginal opening, first oestrus and first conception did not differ significantly between juvenile females raised singly, in single-sex groups of 5, or with an adult male. After the introduction of a male, sterile cycles and/or matings before first conception were experienced by all females whether they were raised singly or in single-sex groups. Of 10 females raised with a male, 4 conceived at their first mating. Onset of puberty in juvenile females raised with an adult female was delayed, while in juvenile females raised with their families (mother, father and litter mates) only vaginal opening was delayed. However, when raised in family groups without the father, vaginal opening as well as first oestrus were delayed. Grouping of females after weaning, with or without a male, did not change the oestrous cycle pattern. Females in these groups cycled independently of each other and the females grouped with a male also mated and conceived independently of each other. Pregnancy was blocked in 7 of 8 females when the stud male was removed and a strange male was introduced. In females exposed to a succession of males, pregnancy was blocked up to 4 times.     

Male-female differences in family size preferences among college students

The question of differences between males and females in fertility values and attitudes was explored through surveys of unmarried male and female college students in North American colleges between 1967 and 1973. The tabulated data indicate that there is a definite difference in family size preference between males and females, with differences varying from 2- to 7/10 of a child depending on religious faith. Number of siblings in the respondent's family had no bearing on the family size preference. Nearly 1/2 of all respondents indicated a desire for number of children in the 2-4 range. However, males were more likely to prefer the lower end of the range while females preferred the upper end. Among all respondents, there were significant increases in preferences for 2-3 children and significant decreases in preferences for 5 or more, even among Catholics. In sum, Catholics preferred a range of 3-4 children with males choosing the lower and females the higher value. The optimal range for Protestants was 2-3, again with males preferring the lower and females the higher value. It is speculated that early socialization may be the reason why women prefer larger families. Research is needed into the effect of working and nonworking mothers on family size preferences of their children.     

Behavioral and social correlates of escape from suppression of ovulation in female common marmosets housed with the natal family

Although female common marmosets typically do not breed while housed with their natal families, up to half ovulate at least once while housed with the intact natal family, and a similar proportion conceive if an unrelated adult male is present in the group. In this study, we investigated the behavioral and social correlates of escape from suppression of ovulation by daughters housed in intact natal families or in families in which the father had been replaced by an unrelated adult male. Focal-animal behavioral data were collected from daughters that were (N = 7) or were not (N = 10) undergoing ovulatory cycles while housed with the natal family and from daughters that were (N = 5) or were not (N = 3) cycling or pregnant in families containing an unrelated male. Additionally, four cyclic and six acyclic females housed in intact natal families underwent simulated “prospecting” tests. Cyclic and acyclic daughters in intact natal families did not engage in sexual interactions with the father and showed few differences from one another in their interactions with the parents. Moreover, cyclic and acyclic daughters did not differ in their willingness to leave the family for short periods or to investigate an unfamiliar family in “prospecting” tests. However, daughters that underwent ovarian cycles in the presence of an unrelated male showed numerous behavioral differences from those in intact natal families, including frequent courtship and sexual behaviors with the male, reduced affiliative interactions with the mother, and elevated frequencies of aggressive display behavior. Moreover, these females were less likely to behave submissively towards the mother or the adult male. These findings suggest that both suppression of ovulation and inhibition of sexual behavior normally contribute to reproductive failure in female marmosets living with their natal families, and that the two components of suppression may become dissociated under specific social conditions. Am J Primatol 41:1–21, 1997. © 1997 Wiley-Liss, Inc.     

Sociosexual development,pair bond formation,and mechanisms of fertility suppression in female cotton-top tamarins (Saguinus oedipus oedipus)

The effect of various social environments on sociosexual behavior was examined in six young female cotton-top tamarins (Saguinus oedipus oedipus) and in three established breeding females. Behavioral observations and hormonal samples were collected on young females while they were living with their families, when they were isolated from conspecifics, and after they were paired with an unrelated male. While living with the family, all females showed a suppression of fertility and low frequencies of sociosexual behavior. Following removal from the family, isolated females displayed an increase in rate of scent marking and an increase in hormonal levels. When young females were paired with males, they were exposed to scent secretions from their natal families, from an unfamilar family, and from a control for a total of 24 weeks. After pairing, hormonal levels increased dramatically, and ovarian cyclicity began. An increase in sociosexual behavior and elevated levels of scent marking accompanied this physiological change. Newly paired females had higher rates of affiliative behavior and scent marking than did established breeding females. However, both newly paired and established breeding males were more likely to initiate contact, grooming bouts, and social sniffing than were females. Time to first ovulation was later in females who were exposed to scent secretions from their natal families than it was in those females given a control for the first 8 weeks following pairing. No female conceived during exposure to scent secretions. However, once normal ovarian cycling had begun or a pregnancy was established, exposure to scent secretions had no effect. Thus, the social environment influences the fertility, sociosexual behavior, and pair bond formation of cotton-top tamarins. In addition, chemical stimuli found in the scent secretions produced by the natal family are most likely involved in reproductive suppression.     

Ovarian function of pygmy marmoset daughters (Cebuella pygmaea) in intact and motherless families

Reproductive inhibition of subordinate Callitrichid group members has been shown to vary with genus; whereas female Leontopithecus subordinates have normal ovarian cycles and occasionally breed within groups, subordinate Saguinus females almost never do so, with Callithrix species showing intermediate levels of reproductive inhibition. No information has been available on patterns of reproduction or inhibition in subordinate females in the genus Cebuella. We assessed fertility in Cebuella pygmaea daughters to allow comparison with the remaining Callitrichid genera. Specifically, the project had two goals: 1) to determine if there was evidence of reproductive inhibition of daughters living in family groups, and 2) to compare the ovarian function of daughters living in intact family groups with that of daughters residing in motherless families (i.e., without the breeding female). We collected daily urine samples for 6–8 weeks from eight pygmy marmoset daughters living in intact family groups or motherless families. Determination of ovulatory cycling or reproductive quiescence depended on the hormonal profiles generated from urinary luteinizing hormone and pregnanediol-3-glucuronide concentrations. All females in the motherless condition (aged 13–30 months) (n = 4) ovulated during the study. In contrast, only one of four daughters (aged 13–20 months) residing in intact families was found to be cycling. Data from motherless groups indicate ovarian cycling may begin between 15 and 17 months of age. Reproductive inhibition occurs in pygmy marmosets, although in a pattern more similar to Callithrix than to other Callitrichid genera. Am. J. Primatol. 43:347–355, 1997. © 1997 Wiley-Liss, Inc.     

Identification of linkage-specific sequence motifs in sialyltransferases

Eukaryotic sialyltransferases (SiaTs) comprise a superfamily of enzymes catalyzing the transfer of sialic acid (Sia) from a common donor substrate to various acceptor substrates in different linkages. These enzymes have been classified as ST3Gal, ST6Gal, ST6GalNAc, and ST8Sia families based on linkage- and acceptor monosaccharide-specificities and sequence similarities. It was recognized early on that SiaTs contain certain well-conserved motifs, and these were denoted as L (large)-, S (small)-, and VS (very small)-motifs; recently, a fourth motif, denoted as motif III, was identified. These four motifs are common to all the SiaTs, irrespective of the linkage- and acceptor saccharide-specificities. In this study, the sequences of the various families have been analyzed, and sequence motifs that are unique to the various families have been identified. These unique motifs are expected to contribute to the characteristic linkage- and acceptor saccharide-specificities of the family members. One of the linkage specific motifs is contiguous to L-motif. Members of ST3Gal and ST8Sia families share significant sequence similarities; in contrast, the ST6Gal family is distinct from the ST6GalNAc family. The latter consists of two subfamilies, one comprising ST6GalNAc I and ST6GalNAc II, and the other comprising ST6GalNAc III, ST6GalNAc IV, ST6GalNAc V, and ST6GalNAc VI. Each of these subfamilies has characteristic sequence motifs not present in the other subfamily.     

Social suppression of ovarian cyclicity in captive and wild colonies of naked mole-rats, Heterocephalus glaber

To investigate the endocrine cause of reproductive suppression in nonbreeding female naked mole-rats, animals from 35 colonies were studied in captivity. Urinary and plasma progesterone concentrations were elevated in pregnant females (urine: 10.0-148.4 ng/mg Cr, 27 samples from 8 females; plasma: 3.6-30.0 ng/ml, 5 samples from 5 females; Days 21-40 of pregnancy) and cyclic breeding females (urine: 0.5-97.8 ng/mg Cr, 146 samples from 7 females; plasma: less than 1.0-35.4 ng/ml, 25 samples from 7 females). The latter group showed cyclic patterns of urinary progesterone, indicating a mean ovarian cycle length of 34.4 +/- 1.6 days (mean +/- s.e.m.) with a follicular phase of 6.0 +/- 0.6 days and a luteal phase of 27.5 +/- 1.3 days (19 cycles from 9 breeding females). In non-breeding females urinary and plasma progesterone values were undetectable (urine: less than 0.5 ng/mg Cr, 232 samples from 64 females; plasma: less than 1.0 ng/ml, 7 samples from 6 females). Breeding females had higher (P less than 0.001) plasma LH concentrations (3.0 +/- 0.2 mi.u./ml, 73 samples from 24 females) than did non-breeding females (1.6 +/- 0.1 mi.u./ml, 57 samples from 44 females). Urinary and plasma progesterone concentrations in non-breeding females from wild colonies situated near Mtito Andei, Kenya, were either below the assay sensitivity limit (urine: less than 0.5 ng/mg Cr, 11 females from 2 colonies; plasma: less than 1.0 ng/ml, 25 females from 4 colonies), or very low (plasma: 1.6 +/- 0.6 ng/ml, 15 females from 4 colonies). In captivity, non-breeding females removed from their colonies (i.e. the dominant breeding female) and either paired directly with a non-breeding male (N = 2), or removed and housed singly for 6 weeks before pairing with a non-breeding male (N = 5) may develop a perforate vagina for the first time in as little as 7 days. Urinary progesterone concentrations rose above 2.0 ng/mg Cr (indicative of a luteal phase) for the first time 8.0 +/- 1.9 days after being separated. These results suggest that ovulation is suppressed in subordinate non-breeding female naked mole-rats in captive and wild colonies, and show that plasma LH concentrations are significantly lower in these non-breeding females. This reproductive block in non-breeding females is readily reversible if the social factors suppressing reproduction are removed.     

Sex ratios in offspring of sex-reversed sea bass and the relationship between growth and phenotypic sex differentiation

Groups of sexually undifferentiated sea bass Dicentrarchus labrax were fed with the androgen 17α-methyltestosterone (MT) during sex differentiation. MT treatment increased males from 79±3% in the controls (the usual 3:1 male:female sex ratio of cultured sea bass) to 100±0%, implying that in the treated groups one out of each five resulting males was a masculinized female (neomale). Thirteen males from the MT treated groups were taken as the parental generation and their sperm used to individually fertilize a pool of eggs from unrelated females. The probability of having at least one neomale was 95% and most probably two or three of the males used were neomales. The offspring from each family were reared separately under the same environmental conditions. Samples were taken at 11 and 15 months of age, during and after sex differentiation, respectively. Results showed that females predominated among the larger fish whereas males and undifferentiated fish predominated among the smaller ones. Intersexes exhibited an intermediate size. All fish with a body length smaller than 12 cm were undifferentiated. These results suggest that sex differentiation is more dependent on length than on age. At 15 months, sex ratios were male-biased in all families, except one (females ranged from 5 to 50%) and only two families had sex ratios not significantly different from 1:1, suggesting that the mechanism of sex determination in the sea bass is not of a XX/XY or ZW/ZZ type since no family exhibited a female-biased progeny, as would be expected from both types. Results support the hypothesis that factors other than genetic, i.e., environmental, may act epigenetically on the sex determination mechanisms of sea bass, as has been demonstrated in other fishes.     

Relationship between metabolism, sex and reproductive tactics in young Atlantic salmon (Salmo salar L.)

Atlantic salmon can differ markedly in their growth and in the timing of reproductive maturation, leading to the dramatic contrast between the large anadromous adults and the diminutive mature male parr. This study examined the growth rates, anatomical and physiological characteristics of parr during the adoption of their discrete life histories to ascertain whether these properties can explain tactic choice. To minimise the impact of habitat differences upon these attributes, salmon were reared in the laboratory until 1.5years of age, when the "decisions" to undergo smoltification or to mature as parr had been taken. At 1.5years, both males and females showed bimodal size-frequency distributions. Neither the population of origin nor the paternal reproductive tactic influenced the "decision" to mature or the growth trajectories. Growth rate (% massday(-1) during their final 10months) and the % male and female offspring in the upper modal group were strongly correlated and varied markedly among families. Mean growth rate per family was negatively correlated with mean metabolic rate per family at emergence. Growth rate decreased as a function of parr size in January and the growth rates of upper modal fish were displaced upwards relative to those of lower modal fish. Most males in the smaller size mode matured, whereas all other fish began smoltification. Mature male parr did not differ from similarly sized female pre-smolt in routine metabolic rate, but these smaller fish had higher metabolic rates than larger male and female pre-smolts. However, mature parr differed markedly from similarly sized females and from larger male and female pre-smolts in possessing higher oxidative and lower glycolytic capacities in muscle. Overall, these data are consistent with the interpretation that growth rates dictate the distribution of parr between upper and lower modal groups. Individuals from faster growing families would be more likely to pass the threshold for smoltification and to accelerate growth, whereas those from slower growing families would remain in the lower mode. The use of metabolic capacities, e.g. metabolic rate, was linked with modal group, whereas muscle oxidative capacity was linked with male maturity. Mean family metabolic rate at emergence was negatively linked with mean growth during the subsequent year, suggesting that metabolic efficiency facilitates growth and eventually smoltification.     

Circadian and Ultradian Periodicities of Grooming Behavior in Family Groups of Common Marmosets (Callithrix jacchus) in Captivity

Three families' groups of common marmosets were observed to describe the characteristics of their grooming rhythmicity, as the duration of the episodes of self- and social grooming made and received by the animals, in captivity under natural environmental conditions. Data were collected by focal animal sampling, at 20 min hourly intervals during 16 non-consecutive days, from January to March in 1994 (sunrise: 05:24 h ± 2 min; sunset: 17:34 h ± 1 min). Time series were obtained for each individual and for each family through hourly duration of grooming. Family time serie was obtained through the mean of its individuals time series. Spectral analysis revealed statistically significant circadian rhythms for all families and individuals. Ultradian components were detected in 50% of the families and in 46.7% of the animals. Acrophases of self- and social grooming calculated by Single Cosinor took place between 9:21 h and 10:39 h, for the families. For individuals self- and social grooming made and received, acrophases occurred from 8:35 h to 12:43 h. The confidence limits of acrophases did not show differences between the families and the individuals within the families, irrespective of their sex, age and reproductive condition, suggesting that this behavior has a stronger temporal marking. Grooming has circadian and ultradian components of rhythmicity in captive families' groups of common marmosets, under natural environmental conditions. Since only some animals showed the ultradian component, it may be consequence of social or environmental masking, or yet phenotypic plasticity of temporal genotype. Further studies are needed to test these possibilities.