Litters Of Pups Research Articles

Clinical and Virological Findings in Pups Naturally Infected by Canine Parvovirus Type 2 Glu-426 Mutant

An outbreak of canine parvovirus type 2 infection caused by the Glu-426 mutant in 2 litters of pups is reported. The infected pups (n = 6) were monitored daily for evidence of clinical signs and hematological changes and for the evaluation of viral shedding in the feces. The disease induced by the Glu-426 mutant was mild in all the infected pups. Vomiting and hemorrhagic diarrhea were not observed; however, the pups developed mucoid diarrhea (3.5 median days), depression (1.5 median days), and relative leukopenia and lymphopenia (2.5 median days). Fever and loss of appetite were observed only in 2 pups. Virus was detected in the feces for 4.5, 6.5, and 46 median days by hemagglutination, virus isolation on cell cultures, and real-time polymerase chain reaction (PCR), respectively. By real-time PCR, the highest viral DNA titers were detected in the feces of both litters at day 10, reaching median values of more than 10(10) DNA copies/mg of feces.

Elf5 is essential for early embryogenesis and mammary gland development during pregnancy and lactation

Elf5 is an epithelial-specific ETS factor. Embryos with a null mutation in the Elf5 gene died before embryonic day 7.5, indicating that Elf5 is essential during mouse embryogenesis. Elf5 is also required for proliferation and differentiation of mouse mammary alveolar epithelial cells during pregnancy and lactation. The loss of one functional allele led to complete developmental arrest of the mammary gland in pregnant Elf5 heterozygous mice. A quantitative mRNA expression study and Western blot analysis revealed that decreased expression of Elf5 correlated with the downregulation of milk proteins in Elf5(+/-) mammary glands. Mammary gland transplants into Rag(-/-) mice demonstrated that Elf5(+/-) mammary alveolar buds failed to develop in an Elf5(+/+) mammary fat pad during pregnancy, demonstrating an epithelial cell autonomous defect. Elf5 expression was reduced in Prolactin receptor (Prlr) heterozygous mammary glands, which phenocopy Elf5(+/-) glands, suggesting that Elf5 and Prlr are in the same pathway. Our data demonstrate that Elf5 is essential for developmental processes in the embryo and in the mammary gland during pregnancy.

Early dietary intervention: long-term effects on blood pressure, brain neuropeptide Y, and adiposity markers

Early life nutrition impacts on subsequent risk of obesity and hypertension. Several brain chemicals responsible for both feeding and cardiovascular regulation are altered in obesity. We examined effects of early postnatal overnutrition on blood pressure, brain neuropeptide Y (NPY), and adiposity markers. Rat pup litters were adjusted to either 3 or 12 male animals (overnutrition and control, respectively) on day 1 of life. After weaning, rats were given either a palatable high-fat diet or standard chow. Smaller litter pups were significantly heavier by 17 days of age. By 16 wk, the effect of litter size was masked by that of diet, postweaning. Small and normal litter animals fed a high-fat diet had similar increases in body weight, plasma insulin, leptin, and adiponectin concentrations, leptin mRNA, and fat masses relative to chow-fed animals. An increase in 11beta-hydroxysteroid dehydrogenase-1 mRNA in white adipose tissue, and a decrease in uncoupling protein-1 mRNA in brown adipose tissue in both small litter groups at 16 wk of age, may represent a programming effect of the altered litter size. NPY concentration in the paraventricular nucleus of the hypothalamus was reduced in high fat-fed groups. Blood pressure was significantly elevated at 13 wk in high-fat-fed animals. This study demonstrates that overnourishment during early postnatal development leads to profound changes in body weight at weaning, which tended to abate with maturation. Thus the effects of long-term dietary intervention postweaning can override those of litter size-induced obesity.

Early deprivation under specific conditions leads to reduced interest in reward in adulthood in Wistar rats

Early life adversity can lead to increased vulnerability to psychiatric disease including depression, with symptoms of depressed mood, impaired coping with negative events, anhedonia, reduced appetite, and elevated stress hormone activity. In rats, postnatal manipulation studies have focused on behavioural and endocrine anxiety effects, and have demonstrated that mild pup stimulation in the form of early handling (EH) is chronically anxiolytic relative to no stimulation in the form of non-handling (NH). Furthermore, apparently severe manipulations in the form of 3–4 h daily litter–dam separation (maternal separation) or pup–litter–dam separation (early deprivation, ED) are either without effect or even EH-like, relative to NH. In this Wistar rat study, we investigated the effects of ED under different circadian and thermal conditions on adulthood behavioural and endocrine responsiveness to environmental challenge, relative to NH. ED was performed on days 1–14, during either the Light or Dark phase and at either 21 °C (cold) or 32 °C (warm). Dark-cold ED adults exhibited reduced motivation to obtain sucrose in a progressive ratio schedule, tended to be less mobile in a forced swim test, but did not exhibit an escape deficit in a foot-shock pre-exposure/shuttle box test, or altered basal or stress endocrine activity. Light ED was completely without effect on adult phenotype. Even relative to stringent NH comparison, dark-cold ED leads to a long-term trait of mild gustatory anhedonia in Wistar rats.

Hyperbaric oxygen therapy protects against mitochondrial dysfunction and delays onset of motor neuron disease in wobbler mice

The Wobbler mouse is a model of human motor neuron disease. Recently we reported the impairment of mitochondrial complex IV in Wobbler mouse CNS, including motor cortex and spinal cord. The present study was designed to test the effect of hyperbaric oxygen therapy (HBOT) on (1) mitochondrial functions in young Wobbler mice, and (2) the onset and progression of the disease with aging. HBOT was carried out at 2 atmospheres absolute (2 ATA) oxygen for 1 h/day for 30 days. Control groups consisted of both untreated Wobbler mice and non-diseased Wobbler mice. The rate of respiration for complex IV in mitochondria isolated from motor cortex was improved by 40% ( P<0.05) after HBOT. The onset and progression of the disease in the Wobbler mice was studied using litters of pups from proven heterozygous breeding pairs, which were treated from birth with 2 ATA HBOT for 1 h/day 6 days a week for the animals' lifetime. A “blinded” observer examined the onset and progression of the Wobbler phenotype, including walking capabilities ranging from normal walking to jaw walking (unable to use forepaws), and the paw condition (from normal to curled wrists and forelimb fixed to the chest). These data indicate that the onset of disease in untreated Wobbler mice averaged 36±4.3 days in terms of walking and 40±5.7 days in terms of paw condition. HBOT significantly delayed ( P<0.001 for both paw condition and walking) the onset of disease to 59±8.2 days (in terms of walking) and 63±7.6 days (in terms of paw condition). Our data suggest that HBOT significantly ameliorates mitochondrial dysfunction in the motor cortex and spinal cord and greatly delays the onset of the disease in an animal model of motor neuron disease.

BEHAVIORAL EFFECTS OF COMBINED PERINATAL L-NAME AND 0.5 Hz MAGNETIC FIELD TREATMENTS

The behavioral effects of the nitric oxide synthase inhibitor N-nitro-L-arginine methyl ester (L-NAME), when perinatally (2 d prenatal-14 d postnatal) co-administered with extremely low frequency magnetic fields, were examined in weanling and adult rats. Litters of rat pups and their dams were exposed continuously to biphasic pulsed fields presented once every 2 s. The magnetic fields were amplitude modulated in successively increasing and decreasing steps (each 30 min) between 0 and 1.8 microT or between 0 to 13 nanoT (reference field) during 4-h periods (6 periods per day). These two treatments were subdivided into dams that received tap water and dams that received 1.0 g/L L-NAME in tap water. The behavioral sequelae to these treatments for 242 progeny from 41 litters were followed from weaning (1 wk after termination of treatment) into adulthood. Compared to exposures to water and nanoT magnetic fields, perinatal exposures to the microT magnetic fields or to L-NAME in the maternal water supply were associated with increased activity levels when the rats were tested as weanlings, but decreased activity levels when the rats were tested as adults. However, the activity of rats that received the combination of L-NAME and microT magnetic fields did not differ significantly from the activity of the rats that had received water and the nanoT fields. Long-term (adulthood) effects of these perinatal treatments on associative learning, as inferred by learned fear to contextual stimuli, were not evident. These results indicate that L- NAME and this particular pattern of magnetic field antagonized one another when co-administered during the perinatal period.

Using Chicken Embryos for Teratology Studies

This unit describes methods for injecting, incubating, handling and analyzing domestic chicken embryos used in teratology studies. It also includes a discussion of caveats and special handling issues as well as some discussion of statistical analyses that differentiate working with chicken embryos from working with clutches of eggs or litters of pups. As an example of potential data, preliminary data from a study of abnormalities in early embryos and hatchling chicks exposed to chlordane are presented.

Effects of litter size on maternal care, body weight and infant development in golden hamsters ( Mesocricetus auratus)

The effects of litter size on maternal care, body weight and infant development of golden hamsters were investigated from a longitudinal perspective. Litters were culled to 1, 3, 6 and 9 pups, and the behavior and body weight of mothers and pups were recorded from the 5th to the 25th postpartum day. We noted that the time spent by mothers in bodily interactions with pups decreased as a function of litter size; maternal pup retrievals reached their maximum around the 13–15th day, which coincided with the increased locomotor activity of pups at this time; the total number of pup retrievals by the mother increased as a function of the litter size, but mothers of larger litters were more ‘efficient’ (i.e. they failed less frequently in exhibiting a full sequence of retrievals) and exhibited a low litter-size proportional mean number of retrievals. All mothers gradually lost body mass throughout lactation, and decrease in body weight was significantly related to litter size. The mean body weight gain (%) by pups decreased as a function of litter size, but we also noted that single and larger litter pups exhibited a decreased body mass (grams) by the 15th day, suggesting that infant development may be impaired at both extremes of experimental conditions. We concluded that the behavior of mothers and pups was affected by the litter size, and it appeared that the litter had an optimal size—not so large as to overlap the mother's physical capacity, and not so small as to fail to compensate for the parental investment.

Aging, reproduction, and the melatonin rhythm in the Siberian hamster.

The present study tested the hypothesis that responsiveness to melatonin, the presence of the melatonin rhythm in circulation, and parameters of the GnRH neuron system are sustained across the aging continuum in Siberian hamsters. Afternoon melatonin injections induced testicular atrophy in 42% of aged males compared with 100% of adult males. The proportion of aged males failing to respond to the melatonin injections was similar to the proportion that failed to undergo testicular regression upon exposure to short days. Exposure to short days induced testicular atrophy in juvenile and adult hamsters; however, regression was incomplete or absent in 43% of aged males. The nocturnal rise in melatonin was similar with regard to duration and peak amplitude, and appropriate with respect to photoperiod in 25-day-old juveniles, adult (5 months), and aged (17 months) hamsters. Neither advanced age nor timed melatonin treatments affected GnRH neuron numbers or distribution. Fertility was maintained in aged and adult males to a comparable extent with respect to latency to first litter and number of pups per litter; reproductive success was dramatically reduced in aged compared with adult females. Because melatonin rhythms accurately reflect day length information throughout the continuum from puberty to advanced age, the present evidence suggests that limitations in testis regression in response to short days or exogenous melatonin in a subset of aged males result from a reduced ability to respond to melatonin. In the wild, failure to undergo testicular regression in the presence of shortening day lengths may extend the breeding season of aged males.

Central allopregnanolone is increased in rat pups in response to repeated, short episodes of neonatal isolation

This experiment investigated whether neonatal isolation stress alters central concentrations of progestins. Whole brain progesterone (P), dihydroprogesterone (DHP), and allopregnanolone (3α, 5α-THP) were measured in pups that were isolated from the nest, dam, and siblings for 1 h on postnatal days (PND) 2–9 and were compared to control litters of pups that were not isolated. Isolated 2-day-old pups had significantly lower central P and higher P to DHP and 3α, 5α-THP metabolism ratios. On PND 9, pups that had been repeatedly isolated (PND 2–8), had significantly lower whole brain DHP and significantly greater whole brain 3α, 5α-THP compared to controls. Thus, the biosocial stress of isolation in neonatal rats alters central pregnane steroids.

Maternal behaviour in lactating rats stimulates c- fos in glutamate decarboxylase-synthesizing neurons of the medial preoptic area, ventral bed nucleus of the stria terminalis, and ventrocaudal periaqueductal gray

Increased activity of the immediate-early gene c- fos can be observed in many areas of the lactating rat brain after dams physically interact with pups and display maternal behaviour. These sites include the medial preoptic area, ventral bed nucleus of the stria terminalis, and the ventrolateral caudal periaqueductal gray, each of which is critical for the normal performance of particular maternal behaviours. The phenotype of cells in these areas that show increased c- fos activity after maternal behaviour, however, is unknown. Via double-label immunocytochemistry, we determined if the population of cells in these sites that express c- fos after maternal behaviour in lactating rats overlaps with the population that expresses the 67,000 mol. wt isoform of glutamate decarboxlyase, the synthesizing enzyme for the inhibitory neurotransmitter GABA. Lactating rats were separated from pups beginning on day 5 postpartum, and 48 h later half were allowed to interact with a litter of pups for 60 min whereas the other half were not. Dams re-exposed to pups were highly maternal, retrieving and licking them as well as displaying prolonged nursing behaviour that included milk letdown. Both groups of dams had a similar number of 67,000 mol. wt glutamate decarboxylase-immunoreactive cells in each site, although the number of 67,000 mol. wt glutamate decarboxylase-immunoreactive cells per microscopic field was significantly greater in the caudal ventrolateral periaqueductal gray than in the ventral bed nucleus of the stria terminalis, which in turn was greater than the medial preoptic area. In pup-stimulated dams, two to fourfold more Fos-immunoreactive cells were found in these three sites compared with non-stimulated controls. Labeling for Fos immunoreactivity and 67,000 mol. wt glutamate decarboxylase immunoreactivity was heterogeneous within each site. In the medial preoptic area, more Fos-immunoreactive and 67,000 mol. wt glutamate decarboxylase-immunoreactive cells (either single or dual-labeled) were found dorsally than ventrally. In the ventral bed nucleus of the stria terminalis, more Fos-immunoreactive and 67,000 mol. wt glutamate decarboxylase-immunoreactive cells were found medially than laterally. Within the caudal ventrolateral periaqueductal gray, 67,000 mol. wt glutamate decarboxylase-immunoreactive labeling was greatest ventromedially, while high numbers of Fos-immunoreactive nuclei were found both ventromedially and ventrolaterally. In pup-stimulated dams, more than half (53% in the medial preoptic area, 59% in the ventral bed nucleus of the stria terminalis, and 61% in the caudal ventrolateral periaqueductal gray) of the total population of Fos-immunoreactive cells also expressed 67,000 mol. wt glutamate decarboxylase. These results suggest that many of the neurons in these sites that show elevated c- fos activity after maternal behaviour are either local inhibitory interneurons or provide inhibitory input to other neural sites. These inhibitory mechanisms may be critical for the display of postpartum nurturance, possibly facilitating maternal behaviour by removing tonic inhibition on sites necessary for maternal responding or by restricting activity in neural sites that inhibit it.

Suppression of leptin during lactation: contribution of the suckling stimulus versus milk production.

Lactation in the rat is characterized by the suppression of pulsatile LH secretion, a large increase in food intake, and changes in energy balance due to the metabolic drain of milk production. The change in energy balance may be a major component in altering reproductive function. A number of factors may contribute to changing energy balance of a lactating animal; one is leptin, the product of adipose tissue, which is known to act partly as a satiety factor to decrease food intake. The aims of the present study were to determine whether there are changes in leptin levels during lactation, a state of high energy demand, and during periods of acute suckling in the presence or absence of changes in energy demand. Our goals were to determine whether lactation and the suckling stimulus influenced serum leptin levels and whether there was a potential role for leptin in the suppression of LH secretion during lactation. The first experiment was performed during diestrus of the estrous cycle, and chronic lactation, (day 9 post partum) in animals suckling 8 pups. The results showed that leptin levels were significantly decreased in both ovarian intact or ovariectomized lactators; this decrease parallels the suppression of pulsatile LH secretion. Serum insulin levels were not altered in the lactating animals. The second experiment was performed in ovariectomized lactators whose 8 pup litters were removed for 48 h, starting on day 9. On day 11, mothers received no pups or pups that were either nonfostered (resulting in no milk production) or fostered (resulting in milk production). The pups were allowed to suckle for 24 h. Following 24 h of acute suckling, serum leptin, and insulin levels correlated with the energy drain on the mother. The levels of leptin were normal and of insulin were elevated in mothers producing no milk. Conversely, leptin levels were suppressed and insulin levels normal in mothers producing milk. The third experiment used the same groups as described for the second experiment except that serial blood samples were collected for measurement of pulsatile LH secretion following 24 h of acute suckling. The results showed that regardless of whether leptin levels remained normal or were suppressed in response to acute suckling, pulsatile LH secretion was significantly inhibited compared with the nonsuckled control animals. In summary, these data suggest that the metabolic drain of milk production, and not the suckling stimulus itself, is the most likely factor responsible for the suppression of leptin secretion during lactation. Furthermore, although the decreased levels of leptin may be causally related to the inhibition of pulsatile LH secretion during chronic lactation, changes in leptin are not a prerequisite for the suppression of LH secretion in response to suckling.

Corticosterone release in response to repeated, short episodes of neonatal isolation : evidence of sensitization

Repeated isolation of neonatal rats produces persistent changes in physiology and behavior. In Experiment 1, we examined changes in plasma corticosterone (CORT) levels as a possible mechanism for the effects of isolation. Pups that were isolated from their mother and the nest for 1 h per day on postnatal days (PND) 2–9 were compared to control litters of pups that were either nonhandled or handled but not isolated. On PND 2, compared to nonhandled pups, handled pups had elevated CORT levels that returned to baseline levels within 30 to 60 min of return to the home cage. No significant elevation of CORT levels were found in handled pups on PND 9. The CORT levels of isolated pups were over twice those of nonhandled pups on PND 2 and four times those of nonhandled pups on PND 9. In Experiment 2, we investigated whether the increased CORT release in response to isolation on PND 9 was the result of the pups treatment on the previous six days as against an effect of maturation. Plasma CORT levels were measured in rat pups that were either isolated, handled or nonhandled on PNDs 2–8 during the conditions of isolation, handling and nonhandling on PND 9. There were no differences among the groups in basal plasma levels of CORT. Handling on PND 9 did not result in elevated CORT levels in any of the groups. All three groups showed a significant increase in plasma CORT levels after isolation on PND 9. However, the CORT response to isolation of pups previously isolated on PND 2–8 were significantly higher than pups that were either handled or nonhandled on PNDs 2–8. Thus, daily episodes of isolation potentiate the hypothalamic-pituitary-adrenal response to stress.

Anthelmintic efficacy of oxibendazole against some important nematodes in dogs and cats

Summary The anthelmintic efficacy and safety of the oxibendazole component in a combination oxibendazole‐niclosamide paste were investigated in dogs and cats and in litters of pups with naturally acquired nematode infections. A single dose of 15 mg oxibendazole/kg body weight given to 70 dogs and to 29 cats reduced faecal worm egg counts (EPG) by 97.6% for Toxocara canis, 95.7% for Trichuris vulpis, 94.6% for Ancylostoma caninum, and 100% for Toxascaris leonina. In cats, 96.7% efficacy was demonstrated against Toxocara cati. In a second trial, 119 pups in 22 litters were treated with the same dosage at 2, 4, and 6 weeks of age. After treatment on two consecutive days, 95% of the pups did not shed T. canis eggs, compared with 85% after only a single treatment. Side effects were rare and only recorded in young animals. A 2‐day treatment schedule is recommended for unweaned pups.

Maternal and developmental toxicity of polychlorinated diphenyl ethers (PCDEs) in Swiss-Webster mice and Sprague-Dawley rats

Polychlorinated diphenyl ethers (PCDEs) are industrial byproducts found in many ecosystems at low levels. PCDEs are not markedly toxic to adult rodents, but their developmental toxicity has not previously been examined. We evaluated the maternal and perinatal toxicity of nine PCDE congeners to outbred mice when compounds were administered from gestation day (GD) 6 through GD 15. 2,2′,4,4′,5,6′-hexaCDE and 2,3′,4′,6-tetraCDE decreased the number of pups born per female mated and the number of pups surviving per litter born. 2,2′,4,4′,5,5′-hexaCDE and 2,2′,4,5,6′-pentaCDE decreased the number of litters born per female mated, without decreasing postnatal survival. The other PCDEs did not decrease survival either pre- or postnatally. None of the PCDEs caused absence of Harderian glands in surviving offspring at the doses administered. Neither induction of cytochromes P450 nor tissue residues of individual congeners correlated well with developmental toxicity. Three PCDEs were also evaluated in outbred (Sprague-Dawley) rats: 2,2′,4,5,6′-pentaCDE and 2,3′,4′,6-tetraCDE, because of their toxicity to mice; 2,2′,4,4′,5,5′-hexaCDE, because it should exhibit PCB-like toxicity. Each congener was administered at three dose levels from GD 6 through GD 15. 2,2′,4,5,6′-pentaCDE decreased the number of litters born at 100 mg/kg/day, and the survival of pups in litters carried to term, at both 50 and 100 mg/kg per day. Postnatal weight gain was also reduced. In contrast to its action in mice, 2,3′,4′,6-tetraCDE decreased neither the numbers of litters born nor postnatal survival of rat offspring, but did suppress postnatal weight gain at least through PD 5. As in mice, induction of cytochromes P450 was not well correlated with the developmental toxicity of individual congeners.

Length of delay to birth of a second litter in dwarf hamsters (Phodopus): Evidence for post-implantation embryonic diapause

In Phodopus, all first litters are born after an 18 (or 19) day gestation. Birth of subsequent litters conceived during a postpartum estrus is routinely, but not always, delayed beyond 18 days. With an interval from first mating to birth of a second litter of as little as 36 days, Phodopus have the most compressed reproductive cycle of any eutherian mammal. Although pups of the Siberian hamster P. sungorus gain thermal independence from maternal care faster than pups of the Djungarian hamster P. campbelli, no species difference in the extent of delay to second litters was found. However, poor growth of first litter pups as a result of unintentional limitation of water bottle access increased delays before birth of a second litter in P. sungorus. Weight of pups in the first litter was a good predictor of the length of delay. In P. campbelli, females with large pups early in lactation were the only ones to deliver a second litter without delay, and short delays enhanced weaning weights for pups in the first litter. Patterns in P. sungorus were similar. The timing of the delay in second litters was investigated in P. campbelli. Delayed implantation during second pregnancies was common. Postimplantation embryonic diapause occurred in 43% of females following unilateral ovariohysterectomy on day 8 of a first pregnancy. As pup growth curves also implicated a postimplantation embryonic diapause, Phodopus may be the only known mammalian genus outside the order Chiroptera in which postimplantation diapause can occur.

Role of the Midbrain Periaqueductal Gray in Maternal Nurturance and Aggression:c-fosand Electrolytic Lesion Studies in Lactating Rats

the upright, crouched, or kyphotic, nursing posture of lactating rats is dependent on suckling stimulation from pups. Because of the neuroanatomical connections of the periaqueductal gray (PAG) and its sensorimotor integration of the analogous lordosis posture displayed by sexually receptive female rats, the possible role of the PAG in kyphosis was investigated using c-fos immunocytochemistry and electrolytic lesions. Lactating rats interacting with and nursing a litter of suckling pups showed greater Fos-immunoreactive nuclei in the lateral and ventrolateral caudal PAG (cPAGl,vl) compared with dams receiving nonsuckling somatosensory, distal, or no stimulation from pups. In contrast, this pattern was not evident in the rostral PAG, where the highest Fos levels occurred in nonsuckled dams, or in five other brainstem sites with either no group differences (peripenduncular, dorsal raphe, and pontine nuclei) or negligible Fos (ventral tegmental area, spinal trigeminal nuclei). After bilateral electrolytic lesions of the cPAGl,vl during gestation or on day 7 postpartum, active maternal behaviors, such as retrieval and licking of pups, and total nursing time were essentially normal. Kyphotic nursing, however, was reduced by 85%, nursing in prone and supine postures increased substantially, and 24 hr litter weight gains were reduced, particularly early in lactation (by 26%). Furthermore, lesioned rats attacked a strange male twice as often as controls did, which is suggestive of reduced fearfulness. These results extend the known roles of the PAG in reproductive and defensive behaviors to the postural control of suckling-induced kyphotic nursing and the modulation of maternal aggression.

Male mating behaviour and patterns of sperm precedence in Arctic ground squirrels

Ground squirrels (genusSpermophilus) display considerable interspecific variation in male reproductive behaviour. Although male Arctic ground squirrels,S. parryii plesius, are territorial during the mating period, males in several other species ofSpermophilusare not. To begin exploring the reasons for this behavioural difference, patterns of mating behaviour and sperm precedence were characterized for a free-living population ofS. parryii plesius. Twenty females that were monitored continuously throughout behavioural oestrus consorted and presumably copulated with a mean of 1.9±0.8 males during a single period of sexual receptivity. A combination of electrophoretic and DNA fingerprinting analyses revealed that more than 90% of pups in litters (N=11) reared by females that consorted with two or more males were sired by a female's first mate. The percentage of young sired by each of a female's consorts did not vary with either consortship duration or the interval between consortships by different males. Instead, the only consistent correlate of paternity was consortship order. Both pre-consortship calling and post-consortship defence of females were significantly associated with first consortships, suggesting that males were able to distinguish unmated females from females that had already copulated. Because the probability of siring young should influence which females are preferred as mates and how males compete for access to those females, comparative studies of sperm precedence patterns may yield insights into the evolution of interspecific variation in male mating behaviour.

Differential growth patterns between successive litters of the eusocial Damaraland mole‐rat, Cryptomys damarensis, from Namibia

Differential mean rates of growth were calculated for successive litters of mole‐rats born to genetically unrelated pairs of C. damarensis. The Logistic equation provided the closest fit to the growth data.Both intra‐ and inter‐colonial variation in mean maximum growth rate between successive litters incorporated into the natal colonies were determined.The mean asymptote (A), growth rate constant (K) and inflection time (I) were modelled for the first five litters of pups born to pairs of mole‐rats. Inter‐colonial analysis of recruitment to colonies revealed litters 1, 2, and 5 to grow faster than litters 3 and 4. Litters 1 and 2 had significantly higher asymptotes and inflection times than litters 3, 4, and 5 (P &lt; 0.001). All litters were assimilated into their natal colonies. There were no significant differences between males and females for the asymptote, growth rate constant, or inflection time (P &lt; 0.05).Intra‐colonial variation of litters 1 to 4 born to a single colony revealed comparable results to that obtained for inter‐colonial comparisons. Multiple comparisons showed litters 1 and 2 to have a significantly higher absolute growth rate than litters 3 and 4. The lowest rate of growth being for litter 4.The patterns of mean differential growth are discussed in the light of the social organization of the colony. It is postulated that growth rates in litters 1, 2, and 3 are more rigid since they constitute the main functional unit of colony organization. Litters 4 and 5 show a greater plasticity in growth; it is speculated that these colony members become incorporated into the various worker and defender groupings which are characteristic of C. damarensis colonies.

Live births after autologous transplant of cryopreserved mouse ovaries.

The fertility of mice after autologous transplantation of ovaries, before or after cryopreservation, was investigated in this study. Female mice were randomly assigned to either sham-operated (n = 14), ovariectomized (n = 11), fresh (n = 12) or cryopreserved (n = 11) ovarian transplant groups. Ovaries were cryopreserved in 1.4 M dimethyl sulphoxide (DMSO) by cooling to -55 degrees C at 0.5 degree C/min (ice nucleation at -7 degrees C), plunged in liquid nitrogen and then thawed at room temperature. Oestrous cyclicity was observed 7 days after sham operation or 15 days after fresh or cryopreserved ovarian transplant. Ovariectomized animals did not demonstrate oestrous cyclicity but were mated, and no pregnancies resulted. Live births were recorded from all sham-operated, all fresh transplant, and 8/11 (73%) cryopreserved transplant animals. Overall mean +/- SEM litter sizes from fresh (4.32 +/- 0.44) and cryopreserved (4.71 +/- 0.57) transplant groups were smaller (P < 0.05) than those of sham-operated animals (12.54 +/- 0.44), although the sizes were not significantly different (P > 0.05) from each other. Animals were mated at least four times, with four litters of live pups from 4/4 sham-operated, 1/10 fresh and 1/9 cryopreserved ovarian transplant animals. Litter sizes from pups of sham-operated and transplant animals were not significantly different from each other. Following autologous transplantation of mouse ovaries, before or after cryopreservation, offspring appeared normal, with high rates of fertility.